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Sample records for barred olivine chondrules

  1. Barred olivine 'chondrules' in lunar spinel troctolite 62295

    NASA Technical Reports Server (NTRS)

    Roedder, E.; Weiblen, P. W.

    1977-01-01

    Several objects have been found in sections of lunar igneous spinel troctolite 62295 that resemble certain meteoritic barred olivine chondrules. Each consists of an apparently spherical single crystal of Fo90 olivine, approximately 0.6-0.8 mm in diameter, containing a set of approximately 30-40 subparallel stringers of An95 plagioclase, whereas the stringers in ordinary meteoritic chondrules consist of glass. The olivine of the 62295 chondrules is also more magnesian, and is radially zoned, having a relatively iron-rich core and rim and an iron-poor intermediate zone. Several possible origins are proposed: impact-generated melt globules solidified in flight, spherical phenocrysts, and meteoritic chondrules, but none of these seems adequate to explain the detailed observations.

  2. Nepheline and sodalite in a barred olivine chondrule from the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Lumpkin, G. R.

    1980-01-01

    The discovery of nepheline and sodalite in association with glass in a barred olivine chondrule from the Allende C3V meteorite is reported, and the possible origin of the minerals is discussed. Scanning electron microscope/energy dispersive analysis indicates that the major minerals of the chondrule are olivine, bronzite and chromite, with olivine bars separated by glass of nearly pure plagioclase composition. The olivine is observed to have a composition richer in Fe than that predicted from olivine-liquid equilibria, indicating, along with the presence of plagioclase glass and small amounts of subcalcic diopside, the nonequilibrium crystallization of the barred olivine chondrule. The textural features of the chondrule are consistent with a liquid origin for nepheline and sodalite from the chondrule-forming liquid under nonequilibrium conditions.

  3. Experimental Reproduction of Olivine rich Type-I Chondrules

    NASA Technical Reports Server (NTRS)

    Smith, Robert K.

    2005-01-01

    Ordinary chondritic meteorites are an abundant type of stony meteorite characterized by the presence of chondrules. Chondrules are small spheres consisting of silicate, metal, and sulfide minerals that experienced melting in the nebula before incorporation into chondritic meteorite parent bodies. Therefore, chondrules record a variety of processes that occurred in the early solar nebula. Two common types of unequilibrated chondrules with porphyritic textures include FeO-poor (type I) and FeO-rich (type II) each subdivided into an A (SiO2-poor) and B (SiO2-rich) series. Type IA chondrules include those with high proportions of olivine phenocrysts (>80% olivine) and type IB chondrules include those with high proportions of pyroxene phenocrysts (<20% olivine). An intermediate composition, type IAB chondrules include those chondrules in which the proportion of olivine phenocrysts is between 20-80%. We conducted high-temperature laboratory experiments (melting at 1550 C) to produce type I chondrules from average unequilibrated ordinary chondrite (UOC) material mixed with small amounts of additional olivine. The experiments were conducted by adding forsteritic rich olivine (San Carlos olivine, Fo 91) to UOC material (GRO 95544) in a 30/70 ratio, respectively. Results of these high temperature experiments suggest that we have replicated type IA chondrule textures and compositions with dynamic crystallization experiments in which a heterogeneous mixture of UOC (GRO 95544) and olivine (San Carlos olivine) were melted at 1550 C for 1 hr. and cooled at 5-1000 C/hr using graphite crucibles in evacuated silica tubes to provide a reducing environment.

  4. Crystal Size Distributions from Porphyritic Olivine Chondrules: Insights into Formation Conditions

    NASA Technical Reports Server (NTRS)

    Zieg, M. J.; Lofgren, G. E.

    2003-01-01

    Most chondrules preserve, in their texture, a record of their precursor material and the nature and intensity of the nebular events in which they were formed. We have used crystal size distributions (CSDs) together with crystallization experiments to explore the textures of natural chondrules and their relationships to natural formation conditions. Many careful experimental studies have demonstrated fundamental relationships between the texture of a chondrule and its precursor material, melting intensity, and cooling rate. However, until recently most studies have focused on distinctions between textural types (e.g., barred, radial, porphyritic). Previous work has shown that CSDs provide precise, reproducible characterizations of chondrule-scale textures, and can be used together with crystallization experiments to estimate chondrule formation conditions. Here, we expand this study to investigate the link between texture and formation conditions for a range of natural porphyritic olivine (PO) chondrules.

  5. Laboratory Experiments Bearing on the Origin and Evolution of Olivine-rich Chondrules

    SciTech Connect

    Richter, Frank M.; Mendybaev, Ruslan A.; Christensen, John N.; Ebel, Denton; Gaffney, Amy

    2011-06-24

    Evaporation rates of K2O, Na2O, and FeO from chondrule-like liquids and the associated potassium isotopic fractionation of the evaporation residues were measured to help understand the processes and conditions that affected the chemical and isotopic compositions of olivine-rich Type IA and Type IIA chondrules from Semarkona. Both types of chondrules show evidence of having been significantly or totally molten. However, these chondrules do not have large or systematic potassium isotopic fractionation of the sort found in the laboratory evaporation experiments. The experimental results reported here provide new data regarding the evaporation kinetics of sodium and potassium from a chondrule-like melt and the potassium isotopic fractionation of evaporation residues run under various conditions ranging from high vacuum to pressures of one bar of H2+CO2, or H2, or helium. The lack of systematic isotopic fractionation of potassium in the Type IIA and Type IA chondrules compared with what is found in the vacuum and one-bar evaporation residues is interpreted as indicating that they evolved in a partially closed system where the residence time of the surrounding gas was sufficiently long for it to have become saturated in the evaporating species and for isotopic equilibration between the gas and the melt. A diffusion couple experiment juxtaposing chondrule-like melts with different potassium concentrations showed that the diffusivity of potassium is sufficiently fast at liquidus temperatures (DK>2-10-4cm2/s at 1650-C) that diffusion-limited evaporation cannot explain why, despite their having been molten, the Type IIA and Type IA chondrules show no systematic potassium isotopic fractionation.

  6. The influence of bulk composition and dynamic melting conditions on olivine chondrule textures

    NASA Technical Reports Server (NTRS)

    Connolly, Harold C., Jr.; Hewins, Roger H.

    1991-01-01

    The effects of the bulk composition and the dynamic melting conditions on the texture of olivine chondrules were investigated in a series of heating experiments. It is shown that variations in the olivine chondrule textures can be produced by varying the FeO/(FeO + MgO) ratio between the average Type IA and Type II chondrule compositions, could affect the texture of a chondrule at a constant initial melting temperature and heating time. A range of the heating times and the masses of precursor spheres caused variations in the degree of melting and in chondrule textures. Chondrule textures were distributed on a graph of initial temperatures vs. FeO/(FeO + MgO) ratios as bands parallel to the olivine disappearance curve. This graph could be used to predict chondrule textures from Fe/(FeO + MgO) ratios at specific initial melting temperatures.

  7. Heterogeneity and O-16-Enrichments in Oxygen Isotope Ratios of Olivine from Chondrules in the Mokoia CV3 Chondrite

    NASA Technical Reports Server (NTRS)

    Jones, R. H.; Leshin, L. A.; Guan, Y.

    2002-01-01

    Two chondrules from Mokoia contain olivine in which oxygen isotopes are extremely heterogeneous, with some grains highly enriched in O-16. These data provide an important link between CAIs and chondrules. Additional information is contained in the original extended abstract.

  8. Oxygen isotopic composition of relict olivine grains in cosmic spherules: Links to chondrules from carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Rudraswami, N. G.; Prasad, M. Shyam; Nagashima, K.; Jones, R. H.

    2015-09-01

    Most olivine relict grains in cosmic spherules selected for the present study are pristine and have not been disturbed during their atmospheric entry, thereby preserving their chemical, mineralogical and isotopic compositions. In order to understand the origin of the particles, oxygen isotope compositions of relict olivine grains in twelve cosmic spherules collected from deep sea sediments of the Indian Ocean were studied using secondary ion mass spectrometry. Most of the data lie close to the CCAM (Carbonaceous Chondrite Anhydrous Mineral) line, with Δ17O ranging from -5‰ to 0‰. The data overlap oxygen isotopic compositions of chondrules from carbonaceous chondrites such as CV, CK, CR and CM, which suggests that chondrules from carbonaceous chondrites are the source of relict grains in cosmic spherules. Chemical compositions of olivine in cosmic spherules are also very similar to chondrule olivine from carbonaceous chondrites. Several olivine relict grains in three cosmic spherules are 16O-rich (Δ17O -21.9‰ to -18.7‰), similar to oxygen isotopic compositions observed in calcium aluminum rich inclusions (CAIs), amoeboid olivine aggregates (AOAs), and some porphyritic chondrules from carbonaceous chondrites. These grains appear to have recorded the initial oxygen isotopic composition of the inner solar nebula. Three olivine grains from two cosmic spherules have δ18O values >+20‰, which could be interpreted as mixing with stratospheric oxygen during atmospheric entry.

  9. Olivine-rich rims surrounding chondrules in the Mokoia CV3 carbonaceous chondrite: Further evidence for parent-body processes

    NASA Astrophysics Data System (ADS)

    Tomeoka, Kazushige; Ohnishi, Ichiro

    2014-07-01

    Fine-grained rims surrounding chondrules and inclusions in the Mokoia CV3 carbonaceous chondrite can be divided into phyllosilicate-rich and olivine-rich types. We present a petrographic and electron microscopic study of the olivine-rich rims and their host objects (referred to as chondrules/olivine-rich rims). The olivine-rich rims consist mainly of Fe-rich olivine and very minor phyllosilicate (saponite). Their host chondrules contain minor saponite and phlogopite, which resulted from aqueous alteration of anhydrous silicates. Mineralogical and compositional characteristics of the chondrules/olivine-rich rims suggest that they experienced mild thermal metamorphic effects. The rims commonly contain veins of coarse-grained Fe-rich olivine, magnetite, and Fe-(Ni) sulfides. The chondrules show abundant evidence of alteration along their peripheries, and the alteration textures suggest a mechanism for rim formation by replacement of the chondrules. Initially, enstatite and opaque nodules preferentially reacted to form coarse, platy, Fe-rich olivine crystals, which were subsequently divided into finer grains. Forsterite was also replaced by Fe-rich olivine. As the alteration advanced, these Fe-rich olivines were disaggregated, mixed with simultaneously produced saponite, and formed rims. In contrast, the surrounding matrix shows no evidence of such alteration and metamorphism. These observations indicate that the chondrules/olivine-rich rims did not experience these secondary processes in their present setting. The results suggest that the chondrules/olivine-rich rims experienced extensive replacement reactions in an environment in which aqueous fluids existed but only in minor amounts. They have probably also undergone simultaneous and/or subsequent mild thermal metamorphism. We suggest that the chondrules/olivine-rich rims are actually clasts transported from a relatively dry region in the parent body that was different from the region where Mokoia was finally lithified.

  10. Experimental Replication of Relict "Dusty" Olivine in Type 1B Chondrules

    NASA Technical Reports Server (NTRS)

    Lofgren, Gary E.; Le, L.

    2002-01-01

    Introduction: Relict "dusty" olivine is considered to be a remnants of previous chondrule forming events based on petrographic and chemical evidence. Dynamic crystallization experiments confirm that dusty olivine can be produced by reduction of FeO-rich olivine in Unequilibrated Ordinary Chondrite (UOC) material. The results of these experiments compliment those of who also produced dusty olivine, but from synthetic starting materials. Techniques: Dynamic crystallization experiments were conducted in which UOC material was reduced in presence of graphite. Starting material was coarsely ground GR095554 or WSG95300 that contained olivine of Fo 65-98. Approximately 75 mg. of UOC material was placed in a graphite crucible and sealed in an evacuated silica tube. The tube was suspended in a gas-mixing furnace operated at 1 log unit below the IW buffer. The experiments were as brief as 1.5 hrs up to 121 hrs. Results: Dusty olivine was produced readily in experiments melted at 1400 C for I hr. and cooled between 5 and 100 C/hr or melted at 1300-1400 C for 24 hours. Fe-rich olivine (dusty olivine precursors) that have been partially reduced were common in the experiments melted at 1400 C and cooled at 1000 C/hr or melted at 1200 C for 24 hrs. Relict olivine is absent in experiments melted at 1400 for 24 hrs, melted above 1400 C, or cooled more slowly than 10 C/hr. Relict olivine in the experiments has minimum Fo value of 83 . Thus even in the shortest experiments the most Fe-rich olivine has been altered significantly. The precursor olivine disappears in a few to many hours depending on temperature. The experiments show Fe-rich olivine in all stages of transition to the new dusty form. The olivine is reduced to form dusty olivine in a matter of a few hours at temperatures less than 1400 C and in minutes at higher temperatures. The reduction appears to proceed from the rim of the crystal inward with time. The reduction appears initially rectilinear as if controlled by crystallography, but with time Fe-metal blebs are randomly distributed throughout the olivine. In a given experiment, dusty olivine can be found in varying stages of development, but in the longest experiments, the Fe-metal blebs are dominant and they appear to be migrating out of the olivine. The composition of the dusty olivine ranges from Fo 94-99. The Cr, Mn, and Ca content of the newly formed, dusty olivine is slightly less on average that the precursor olivine, but is till with the range of type 1 olivine. Chadacrysts in the low Ca pyroxene are most common in the higher temperature, more slowly cooled experiments and range in composition from Fo 90-99. Application to chondrule formation: These experiments place time-temperature limits on the preservation of Fe-rich olivine and the production of dusty olivine during chondrule forming events. The reduction process proceeds in a few hours at temperatures above 1400 C and in 10's of hours at temperature between 1200 and 1300 C. This result further confirms th at chondrules form in a few hours to days as suggested earlier. The experiments also confirm that dusty olivine can form from typical Fe-rich olivine in UOC material during the recycling of such olivine in the chondrule forming process.

  11. Granoblastic olivine aggregates in magnesian chondrules: Planetesimal fragments or thermally annealed solar nebula condensates?

    NASA Astrophysics Data System (ADS)

    Whattam, Scott A.; Hewins, Roger H.; Cohen, Bosmat A.; Seaton, Nicholas C.; Prior, David J.

    2008-05-01

    Granoblastic olivine aggregates (GOA) have been discovered in some Type I magnesian chondrules within carbonaceous chondrites by Libourel and Krot [Libourel, G., Krot, A.N., 2007. Evidence for the presence of planetesimal material among the precursors of magnesian chondrules of nebular origin. Earth Planet. Sci. Lett. 254, 1-8], who proposed an origin from pre-existing planetesimals. Amoeboid olivine aggregates (AOA), generally considered as aggregates of solar nebula condensates and found within similar carbonaceous chondrites, display similar equilibrium texture, though on a finer scale. For these reasons, we conducted experiments to determine if annealing of olivine required time scales appropriate to planetesimal or nebular heating. Pressed < 43 µm and < 63 µm San Carlos olivine powder (Fo 88.4) was isothermally heated at temperatures ranging from 1350-1550 °C for 1-100 h. The 100 h runs yield olivine aggregates with well-developed granoblastic texture at all temperatures, manifest as a network of randomly-oriented and sutured olivine grains with 120° triple junctions. Individual olivine grains are 4-6 sided and polygonal by 1450 °C and equigranular texture is developed at high temperature (1500-1550 °C). Melting of olivine commences at 1450-1500 °C and aids in 'ripening' and suturing (grain coarsening and grain boundary migration). Textural equilibrium is clearly met at 1550 °C. A planetesimal origin cannot be ruled out; however, the experimental evidence reveals that granoblastic texture can be reproduced in an interval not inconsistent with heating times for nebular objects. GOA may have experienced higher degrees of thermal processing than the finer-grained AOA. If the precursors were the same, grain coarsening would have to be accompanied by modification to bulk and isotopic compositions. However, the precursors could have been olivine condensates formed later than AOA. Annealing may have been a widespread process operating in the primordial solar nebula responsible for thermal processing and formation of GOA prior to their incorporation into chondrules.

  12. A Relict-Grain-Bearing Porphyritic Olivine Compound Chondrule from LL3.0 Semarkona that Experienced Limited Remelting

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    Chondrule D8n in LL3.0 Semarkona is a porphyritic olivine (PO) chondrule, 1300 x 1900 microns in size, with a complicated thermal history. The oldest recognizable portion of D8n is a moderately high-FeO, PO chondrule that is modeled as having become enmeshed in a dust ball containing a small, intact, low-FeO porphyritic chondrule and fine-grained material consisting of forsterite, kamacite, troilite, and possibly reduced C. The final chondrule melting event may have been a heat pulse that preferentially melted the low-FeO material and produced a low-FeO, opaque-rich, exterior region, 45-140 microns in thickness, around the original chondrule. Ai one end of the exterior region, a kamacite- and troilite-rich lump 960 pm in length formed. During the final melting event, the coarse, moderately ferroan olivine phenocrysts within the original chondrule appear to have been partly resorbed (These relict phenocrysts have the highest concentrations of FeO, MnO, and Cr2O3-7.5, 0.20, and 0.61 wt%, respectively-in D8n.). Narrow olivine overgrowths crystallized around the phenocrysts following final chondrule melting; their compositions seem to reflect mixing between melt derived from the exterior region and the resorbed margins of the phenocrysts. During the melting event, FeO in the relict phenocrysts was reduced, producing numerous small blebs of Ni-poor metallic Fe along preexisting curvilinear fractures. The reduced olivine flanking the trails of metal blebs has lower FeO than the phenocrysts but virtually identical MnO and Cr2O3 contents. Subsequent parent-body aqueous alteration in the exterior region of the chondrule formed pentlandite and abundant magnetite.

  13. Forsterite and Olivine in Sahara-97210 (LL3.2) and Chainpur (LL3.4) Chondrules: Compositional Evolution and the Influence of Melting

    NASA Technical Reports Server (NTRS)

    Ruzicka, A.; Floss, C.

    2004-01-01

    It is generally accepted that chondrules contain relict grains that did not crystallize in situ, and that forsterite is one type of relict grain which is a likely precursor for chondrules. Chemically and morphologically similar forsterite is also found as "isolated grains", especially in carbonaceous chondrites. Using SIMS, we analyzed forsterite, ferrous overgrowths around forsterite, and coexisting normal olivine in 5 chondrules and 2 isolated grains in the Sahara-97210 ('Sahara") LL3.2 chondrite. We earlier used the same methods to study olivine in 3 Chainpur chondrules that contain relict forsterite. Our new data for Sahara provide additional insight into the processes affecting chondrules and their precursors.

  14. An experimental study of trace element partitioning between olivine, orthopyroxene and melt in chondrules - Equilibrium values and kinetic effects

    NASA Technical Reports Server (NTRS)

    Kennedy, A. K.; Lofgren, G. E.; Wasserburg, G. J.

    1993-01-01

    Mineral/melt partition coefficients were measured using an ion microprobe for 32 elements in orthopyroxene and olivine in equilibrium and dynamic crystallization experiments on compositions corresponding to chondrules. The mineral/melt partition coefficients calculated from the measured concentrations for both olivine and orthopyroxene show very little change between equilibrium experiments and dynamic experiments with cooling rates of up to 100 C/h. The results provide a self-consistent set of partition coefficients that can be used in thermodynamic models of equilibrium and kinetic partitioning between olivine, orthopyroxene, and melt. These data can be used in models of partial melting and crystal fractionation in olivine- and orthopyroxene-rich systems, such as chondrules. The results may also be applicable to mantle peridotites, komatiitic and picritic lavas, and ultramafic intrusions.

  15. Chromite and olivine in type II chondrules in carbonaceous and ordinary chondrites - Implications for thermal histories and group differences

    NASA Technical Reports Server (NTRS)

    Johnson, Craig A.; Prinz, Martin

    1991-01-01

    Unequilibrated chromite and olivine margin compositions in type II chondrules are noted to differ systematically among three of the chondrite groups, suggesting that type II liquids differed in composition among the groups. These differences may be interpreted as indicators of different chemical compositions of the precursor solids which underwent melting, or, perhaps, as differences in the extent to which immiscible metal sulfide droplets were lost during chondrule formation. Because zinc is detectable only in type II chromites which have undergone reequilibration, the high zinc contents reported for chondritic chromites in other studies probably reflect redistribution during thermal metamorphism.

  16. Relative abundances of chondrule primary textural types in ordinary chondrites and their bearing on conditions of chondrule formation

    NASA Astrophysics Data System (ADS)

    Gooding, J. L.; Keil, K.

    1981-03-01

    A petrographic survey of > 1600 chondrules in thin-sections of 12 different mildly to highly unequilibrated H-, L-, and Li-chondrites, as well as morphological and textural study of 141 whole chondrules separated from 11 of the same chondrites, was used to determine the relative abundances of definable chondrule primary textural types. Percentage abundances of various chondrule types are remarkably similar in all chondrites studied and are ˜47-52 porphyritic olivine-pyroxene (POP), 15-27 porphyritic olivine (P 0), 9-11 porphyritic pyroxene (PP), 34 barred olivine (BO), 7-9 radial pyroxene (RP), 2-5 granular olivine-pyroxene (GOP), 3-5 cryptocrystalline (C), and ≥ 1 metallic (M). Neither chondrule size nor shape is strongly correlated with textural type. Compound and cratered chondrules, which are interpreted as products of collisions between plastic chondrules, comprise ˜2-28% of non-porphyritic (RP, GOP, C) but only ˜2-9% of porphyritic (POP, PO, PP, BO) chondrules, leading to a model-dependent implication that non-porphyritic chondrules evolved at number densities (chondrules per unit volume of space) which were 102 to 104 times greater than those which prevailed during porphyritic chondrule formation (total range of ˜1 to ˜106 m-3. Distinctive "rims" of fine-grained sulfides and/or silicates occur on both porphyritic and non-porphyritic types and appear to post-date chondrule formation. Apparently, either the same process(es) contributed chondrules to all unequilibrated ordinary chondrites or, if genetically different, the various chondrule types were well mixed before incorporation into chondrites. Melting of pre-existing materials is the mechanism favored for chondrule formation.

  17. A new estimate of the chondrule cooling rate deduced from an analysis of compositional zoning of relict olivine

    SciTech Connect

    Miura, H.; Yamamoto, T.

    2014-03-01

    Compositional zoning in chondrule phenocrysts records the crystallization environments in the early solar nebula. We modeled the growth of olivine phenocrysts from a silicate melt and proposed a new fractional crystallization model that provides a relation between the zoning profile and the cooling rate. In our model, we took elemental partitioning at a growing solid-liquid interface and time-dependent solute diffusion in the liquid into consideration. We assumed a local equilibrium condition, namely, that the compositions at the interface are equal to the equilibrium ones at a given temperature. We carried out numerical simulations of the fractional crystallization in one-dimensional planar geometry. The simulations revealed that under a constant cooling rate the growth velocity increases exponentially with time and a linear zoning profile forms in the solid as a result. We derived analytic formulae of the zoning profile, which reproduced the numerical results for wide ranges of crystallization conditions. The formulae provide a useful tool to estimate the cooling rate from the compositional zoning. Applying the formulae to low-FeO relict olivine grains in type II porphyritic chondrules observed by Wasson and Rubin, we estimate the cooling rate to be ∼200-2000 K s{sup –1}, which is greater than that expected from furnace-based experiments by orders of magnitude. Appropriate solar nebula environments for such rapid cooling conditions are discussed.

  18. The formation conditions of enstatite chondrites: Insights from trace element geochemistry of olivine-bearing chondrules in Sahara 97096 (EH3)

    NASA Astrophysics Data System (ADS)

    Jacquet, Emmanuel; Alard, Olivier; Gounelle, Matthieu

    2015-09-01

    We report in situ LA-ICP-MS trace element analyses of silicate phases in olivine-bearing chondrules in the Sahara 97096 (EH3) enstatite chondrite. Most olivine and enstatite present rare earth element (REE) patterns comparable to their counterparts in type I chondrules in ordinary chondrites. They thus likely share a similar igneous origin, likely under similar redox conditions. The mesostasis however frequently shows negative Eu and/or Yb (and more rarely Sm) anomalies, evidently out of equilibrium with olivine and enstatite. We suggest that this reflects crystallization of oldhamite during a sulfidation event, already inferred by others, during which the mesostasis was molten, where the complementary positive Eu and Yb anomalies exhibited by oldhamite would have possibly arisen due to a divalent state of these elements. Much of this igneous oldhamite would have been expelled from the chondrules, presumably by inertial acceleration or surface tension effects, and would have contributed to the high abundance of opaque nodules found outside them in EH chondrites. In two chondrules, olivine and enstatite exhibit negatively sloped REE patterns, which may be an extreme manifestation of a general phenomenon (possibly linked to near-liquidus partitioning) underlying the overabundance of light REE observed in most chondrule silicates relative to equilibrium predictions. The silicate phases in one of these two chondrules show complementary Eu, Yb, and Sm anomalies providing direct evidence for the postulated occurrence of the divalent state for these elements at some stage in the formation reservoir of enstatite chondrites. Our work supports the idea that the peculiarities of enstatite chondrites may not require a condensation sequence at high C/O ratios as has long been believed.

  19. Variations in the O-isotope composition of gas during the formation of chondrules from the CR chondrites

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Nagashima, Kazuhide; Krot, Alexander N.; Ogliore, Ryan C.; Hellebrand, Eric

    2014-05-01

    To better understand the environment of chondrule formation and constrain the O-isotope composition of the ambient gas in the Renazzo-like carbonaceous (CR) chondrite chondrule-forming region, we studied the mineralogy, petrology, and in situ O-isotope compositions of olivine in 11 barred olivine (BO) chondrules and pyroxene and silica in three type I porphyritic chondrules from the CR chondrites Gao-Guenie (b), Graves Nunataks (GRA) 95229, Pecora Escarpment (PCA) 91082, and Shişr 033. BO chondrules experienced a higher degree of melting than porphyritic chondrules, and therefore, it has been hypothesized that they more accurately recorded the O-isotope composition of the gas in chondrule-forming regions. We studied the O-isotope composition of silica as it has been hypothesized to have formed via direct condensation from the gas.

  20. Using the Fe/Mn Ratio of FeO-Rich Olivine In WILD 2, Chondrite Matrix, and Type IIA Chondrules to Disentangle Their Histories

    NASA Technical Reports Server (NTRS)

    Frank, David R.; Le, L.; Zolensky, M. E.

    2012-01-01

    The Stardust Mission returned a large abundance of impactors from Comet 81P/Wild2 in the 5-30 m range. The preliminary examination of just a limited number of these particles showed that the collection captured abundant crystalline grains with a diverse mineralogy [1,2]. Many of these grains resemble those found in chondrite matrix and even contain fragments of chondrules and CAIs [1-3]. In particular, the olivine found in Wild 2 exhibits a wide compositional range (Fa0-97) with minor element abundances similar to the matrix olivine found in many carbonaceous chondrites (CCs) and unequilibrated ordinary chondrites (UOCs). Despite the wide distribution of Fa content, the olivine found in the matrices of CCs, UOCs, and Wild 2 can be roughly lumped into two types based solely on fayalite content. In fact, in some cases, a distinct bi-modal distribution is observed.

  1. Fayalite-rich rims, veins, and halos around and in forsteritic olivines in CAIs and chondrules in carbonaceous chondrites: Types, compositional profiles and constraints of their formation

    SciTech Connect

    Hua, X.; Adam, J.; Palme, H.; Goresy, A. E. )

    1988-06-01

    Fayalite-rich rims, veins, and halos around and in forsteritic olivines are a wide-spread phenomenon in chondrules, Ca, Al-rich inclusions (CAIs), and single grains in carbonaceous chondrites. The presence of fayalite rod-like crystals and laths in rims, veins, in wall of pores, and as fluffy network bridging neighboring olivines, pyroxenes, feldspars, etc. is strongly suggestive that the fayalitic olivine was formed by condensation presumably from the solar nebula gas. The formation of the fayalitic olivine was probably caused by an increase in the H{sub 2}O/H{sub 2} ratio (to a ratio between 0.1-1) subsequent to condensation of forsterite. At that stage, FeNi inclusions in olivine were also oxidized and fayalitic halos around the metal were then formed Fe diffusion along with addition of SiO{sub 2} from the solar gas or loss of M{sub g}O to the solar gas. The Fa-rich olivine rims and veins display a narrow compositional variation between Fa{sup 34} and Fa{sup 46}. Subsequent to condensation of Fa-rich olivine and oxidation of FeNi metal, Fe diffused in forsterite. This diffusion was probable enhanced due to the presence of point defects in olivine or the formation of a nonstoichiometric phase analogous to laihunite enriched in Al{sub 2}O{sub 3} and Cr{sub 2}O{sub 3}. However, the presence of Al{sub 2}O{sub 3{minus}} and Cr{sub 2}O{sub 3{minus}} rich discrete domains cannot by excluded. Cooling rates calculated by modeling of the diffusion profiles are indicative of rapid cooling subsequent to the condensation of fayalitic olivines. The authors obtain cooling rates ranging from 2000{degree}/day and 10{degree}C/day at an initial temperature of 1200C{degree} and 900C{degree}, respectively.

  2. Relict grains in chondrules: Evidence for chondrule recycling

    NASA Technical Reports Server (NTRS)

    Jones, R. H.

    1994-01-01

    The presence of relict grains in chondrules, which offers some insight into the degree to which chondrule material was recycled in the chondrule-forming region, is discussed in this report. Relics are grains that clearly did not crystallize in situ in the host chondrule. They represent coarse-grained precursor material that did not melt during chondrule formation, and provide the only tangible record of chondrule precursor grains. Relics are commonly identified by a large difference in size, textural differences, and/or significant compositional differences compared with normal grains in the host chondrule. Two important types of relics are: (1) 'dusty,' metal-bearing grains of olivine and pyroxene; and (2) forsterite (Mg-rich olivine) grains present in FeO-rich chondrules.

  3. Size-frequency distributions of EH3 chondrules

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.; Grossman, Jeffrey N.

    1987-09-01

    Size-frequency distributions of chondrules in three EH3 chondrites, namely Qingzhen, Kota-Kota and ALHA77156, are presently determined. Radial pyroxene chondrules are larger than cryptocrystalline chondrules, while nonporphyritic chondrules have a broader size-frequency distribution than the porphyritic, and porphyritic olivine-pyroxene chondrules are larger than porphyritic pyroxene chondrules. This last result is due to a reaction of fine-grained olivine with free silica to form pyroxene during mild thermal metamorphism of the whole-rocks.

  4. Size-frequency distributions of EH3 chondrules

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Grossman, Jeffrey N.

    1987-01-01

    Size-frequency distributions of chondrules in three EH3 chondrites, namely Qingzhen, Kota-Kota and ALHA77156, are presently determined. Radial pyroxene chondrules are larger than cryptocrystalline chondrules, while nonporphyritic chondrules have a broader size-frequency distribution than the porphyritic, and porphyritic olivine-pyroxene chondrules are larger than porphyritic pyroxene chondrules. This last result is due to a reaction of fine-grained olivine with free silica to form pyroxene during mild thermal metamorphism of the whole-rocks.

  5. The Relationship Between Metal and Silicates in Type I Chondrules

    NASA Astrophysics Data System (ADS)

    Hewins, R. H.; Zanda, B.

    1992-07-01

    There is wide agreement that chondrules were formed by melting of pre-existing minerals, but there is still controversy over how, when, and from exactly what they were formed. Much work on chondrules has emphasized magnesian granular/microporphyritic type I chondrules, but metal-rich type I chondrules are even more abundant in carbonaceous chondrites (McSween, 1977). The observation that metal is homogeneous within one chondrule but differs from chondrule to chondrule (Zanda et al., 1991) suggests some systematic relationship may exist between metal and silicates. It is the purpose of this paper to investigate those relationships for Renazzo and Semarkona. We observe a strong correlation between the silicate texture of chondrules, which falls in a fine-coarse granular-porphyritic-barred sequence related to degree of melting, and the nature of the metal. Where olivine grains are small and/or closely packed, metal occurs as tiny spherules. Where grain size and melt channels are larger, metal forms coalescing blebs or chains. With distinctly microporphyritic textures metal occurs mostly near the periphery of the chondrule and with truly porphyritic and barred chondrules it forms a rim or crown around the chondrule. Similar metal coalescence and expulsion textures have been observed for Bishunpur chondrules (Rambaldi and Wasson, 1981) and geochemical evidence shows that metal rims on Semarkona chondrules were derived from their interiors (Grossman and Wasson, 1987). There appears to be a continuous gradation between metal-rich and ordinary type I chondrules as a function of degree of melting, which suggests that many type I chondrules passed through a stage of being metal-rich during formation. If chondrules were manufactured from homogeneous interstellar dust, there is a very short time period for metal-silicate fractionation. If chondrules were formed from condensate aggregates, this constraint can be relaxed as condensates aggregated over different temperature ranges could have different metal-silicate ratios. High concentrations of Si, Cr, and P in metal in chondrules have been explained as due to precursor grains of condensation origin (Grossman and Olsen, 1974; Desnoyers, 1980; Zanda, 1992) but might alternatively be due to reduction during melting at very low oxygen fugacities (Dickinson et al., 1992). We find the highest concentrations of Cr and Si in the metal in the chondrules with the highest degree of melting associated with the most magnesian silicates. This suggests that these elements were reduced into the metal during chondrule melting. However, among these forsteritic chondrules, those that experienced higher oxygen fugacities based on Cr partitioning between olivine and metal have metal grains with silica melt droplets instead of reduced Si. This indicates oxidation during cooling at temperatures exceeding 1713 degrees C. Clearly metal, like silicate, was modified during chondrule formation and that probably accounts both for the integration of Cr and Si into metal and the formation of the round silica inclusions observed by Perron et al. (1992). References: McSween H. Jr. (1977) Geochim. Cosmochim. Acta 41, 1843-1860. Zanda B., Bourot-Denise M., and Perron C. (1991) Lunar Planet. Sci. XXII, 1543-1544. Rambaldi E.R. and Wasson J.T. (1981) Geochim. Cosmochim. Acta 45, 1001-1015. Grossman J. and Wasson J.T. (1987) Geochim. Cosmochim. Acta 51, 3003-3011. Grossman L. and Olsen E. (1974) Geochim. Cosmochim. Acta 38, 173- 187. Desnoyer C. (1980) Earth Planet. Sci. Lett. 47, 223-234. Dickinson T.L., Lofgren G.E., and Casanova I. (1992) Lunar Planet. Sci. XXII, 309-310. Perron C., Zanda B., Bourot-Denise M., and Mostefaoui S. (1992) Meteoritics, this volume.

  6. Chromite-rich mafic silicate chondrules in ordinary chondrites: Formation by impact melting

    NASA Technical Reports Server (NTRS)

    Krot, Alexander N.; Rubin, Alan E.

    1993-01-01

    Chromium-rich chondrules constitute less than 0.1 percent of all ordinary chondrite (OC) chondrules and comprise three groups: chromian-spinel chondrules, chromian-spinel inclusions, and chromite-rich mafic silicate (CRMS) chondrules. Chromian-spinel chondrules (typically 100-300 microns in apparent diameter) exhibit granular, porphyritic and unusual textures and occur mainly in H chondrites. Their morphologies are distinct from the irregularly shaped chromian-spinel inclusions of similar mineralogy. Chromian-spinel chondrules and inclusions consist of grains of chromian-spinel embedded in plagioclase (Pl) or mesostasis of Pl composition. Many also contain accessory ilmenite (Ilm), high-Ca pyroxene (Px), merrillite (Mer), and rare olivine (Ol); some exhibit concentric mineral and chemical zoning. CRMS chondrules (300-1100 microns in apparent diameter) are generally larger than chromian-spinel chondrules and occur in all metamorphosed OC groups. Most CRMS chondrules are nearly spherical although a few are ellipsoidal with a/b aspect ratios ranging up to 1.7. Textures include cryptocrystalline, granular, radial, barred, and porphyritic varieties; some contain apparently relict grains. The chondrules consist of chromite (Chr), Ol and Pl, along with accessory Mer, troilite (Tr), metallic Fe-Ni (Met), Px and Ilm. The mesostasis in CRMS chondrules is nearly opaque in transmitted light; thus, they can be easily recognized in the optical microscope. Based on the similarity of mineralogy and chemistry between CRMS chondrules of different textures (opaque chromite-rich mesostasis, skeletal morphology of Ol grains, similar bulk compositions) we suggest that these chondrules form a genetically related population.

  7. Timing of Formation of a Wassonite-bearing Chondrule

    NASA Technical Reports Server (NTRS)

    Needham, A. W.; Nakamura-Messenger, K.; Rubin, A. E.; Choi, B.-G.; Messenger, S.

    2014-01-01

    Wassonite, ideally stoichiometric TiS, is a titanium monosulfide recently discovered in the Yamato 691 EH3 enstatite chondrite. Wassonite grains were located within the mesostasis of a single barred olivine chondrule. Such chondrules likely formed in the solar nebula by melting of fine grained precursor dust. The reduced nature of enstatite chondrites, and the wassonite-bearing chondrule in particular, may suggest precursor materials included Ti-bearing troilite, metallic Fe-Ni, and possibly graphite. Under the reducing conditions present in enstatite chondrites S can partition more readily into silicate melt, leading to raised Ti content of the residual Fe-FeS melt. By the time sulfide crystallized from the melt, the Ti concentration was high enough to form small grains of pure TiS - wassonite. As a mineral not previously observed in nature wassonite and its host chondrule may provide additional constraints on physical and chemical conditions in the solar nebula at a specific time and location relevant to planetary formation. Enstatite chondrites and Earth share similar isotopic compositions of Cr, Ni, Ti, O and N. Understanding the formation conditions of enstatite chondrite chondrules may therefore have wider relevance for terrestrial planet accretion and other early inner solar system processes. Here we present preliminary results of an investigation of the Al-Mg systematics of the only known wassonite-bearing chondrule. The goal of this study is to determine whether this chondrule's formation was contemporaneous with other enstatite chondrite chondrules and to establish its place in the broader timeline of solar system events.

  8. The conditions of chondrule formation, Part II: Open system

    NASA Astrophysics Data System (ADS)

    Friend, Pia; Hezel, Dominik C.; Mucerschi, Daniel

    2016-01-01

    We studied the texture of 256 chondrules in thin sections of 16 different carbonaceous (CV, CR, CO, CM, CH) and Rumuruti chondrites. In a conservative count ∼75% of all chondrules are mineralogically zoned, i.e. these chondrules have an olivine core, surrounded by a low-Ca pyroxene rim. A realistic estimate pushes the fraction of zoned chondrules to >90% of all chondrules. Mineralogically zoned chondrules are the dominant and typical chondrule type in carbonaceous and Rumuruti chondrites. The formation of the mineralogical zonation represents a fundamentally important process of chondrule formation. The classic typification of chondrules into PO, POP and PP might in fact represent different sections through mineralogically zoned chondrules. On average, the low-Ca pyroxene rims occupy 30 vol.% of the entire chondrule. The low-Ca pyroxene most probably formed by reaction of an olivine rich chondrule with SiO from the surrounding gas. This reaction adds 3-15 wt.% of material, mainly SiO2, to the chondrule. Chondrules were open systems and interacted substantially with the surrounding gas. This is in agreement with many previous studies on chondrule formation. This open system behaviour and the exchange of material with the surrounding gas can explain bulk chondrule compositional variations in a single meteorite and supports the findings from complementarity that chondrules and matrix formed from the same chemical reservoir.

  9. Reduction of CO2 during serpentinization of olivine at 300 °C and 500 bar

    NASA Astrophysics Data System (ADS)

    Berndt, Michael E.; Allen, Douglas E.; Seyfried, William E., Jr.

    1996-04-01

    CO2 reduction processes occurring during experimental serpentinization of olivine at 300 °C and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas. Data reveal that conversion of Fe(II) in olivine to Fe(III) in magnetite during serpentinization leads to production of H2 and conversion of dissolved CO2 to reduced-C species including methane, ethane, propane, and an amorphous carbonaceous phase. Hydrocarbon gases generated in the process fit a Schulz-Flory distribution consistent with catalysis by mineral reactants or products. Magnetite is inferred to be the catalyst for methanization during serpentinization, because it has been previously shown to accelerate Fischer-Tropsch synthesis of methane in industrial applications involving mixtures of H2 and CO2. The carbonaceous phase was predominantly aliphatic, but had a significant aromatic component. Although this phase should ultimately be converted to hydrocarbon gases and graphite, if full thermodynamic equilibrium were established, its formation in these experiments indicates that the pathway for reduction of CO2 during serpentinization processes is complex and involves a series of metastable intermediates.

  10. Kosmochloric Ca-rich pyroxenes and FeO-rich olivines (Kool grains) and associated phases in Stardust tracks and chondritic porous interplanetary dust particles: Possible precursors to FeO-rich type II chondrules in ordinary chondrites.

    NASA Astrophysics Data System (ADS)

    Joswiak, D. J.; Brownlee, D. E.; Matrajt, G.; Westphal, A. J.; Snead, C. J.

    2009-11-01

    Terminal particles and mineral fragments from comet 81P/Wild 2 were studied in 16 aerogel tracks by transmission and secondary electron microscopy. In eight tracks clinopyroxenes with correlated Na2O and Cr2O3 contents as high as 6.0 wt% and 13.0 wt%, respectively, were found. Kosmochloric (Ko) clinopyroxenes were also observed in 4 chondritic interplanetary dust particles (IDPs). The Ko clinopyroxenes were often associated with FeO-rich olivine ± Cr-rich spinel ± aluminosilicate glass or albitic feldspar, assemblages referred to as Kool grains (Ko = kosmochloric Ca-rich pyroxene, ol = olivine). Fine-grained (submicron) Kool fragments have textures suggestive of crystallization from melts while coarse-grained (>1 µm) Kool fragments are often glass-free and may have formed by thermal metamorphism in the nebula. Average major and minor element distributions between clinopyroxenes and coexisting FeO-rich olivines are consistent with these phases forming at or near equilibrium. In glass-bearing fine-grained Kool fragments, high concentrations of Na in the clinopyroxenes are inconsistent with existing experimentally determined partition coefficients at equilibrium. We speculate that the availability of Cr in the melt increased the clinopyroxene Na partition coefficient via a coupled substitution thereby enhancing this phase with the kosmochlor component. The high temperature minerals, fine-grain sizes, bulk compositions and common occurrence in the SD tracks and IDPs support the idea that Kool grains could have been precursors to type II chondrules in ordinary chondrites. These grains, however, have not been observed in these meteorites suggesting that they were destroyed during chondrule formation and recycling or were not present in the nebula at the time and location where meteoritic chondrules formed.

  11. Glass-rich chondrules in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Krot, Alexander N.; Rubin, Alan E.

    1994-01-01

    There are two types of glass-rich chondrules in unequilibrated ordinary chondrites (OC): (1) porphyritic chondrules containing 55-85 vol% glass or microcrystalline mesostasis and (2) nonporphyritic chondrules, containing 90-99 vol% glass. These two types are similar in mineralogy and bulk composition to previously described Al-rich chondrules in OC. In addition to Si-, Al- and Na-rich glass or Ca-Al-rich microcrystalline mesostasis, glass-rich chondrules contain dendritic and skeletal crystals of olivine, Al2O3-rich low-Ca pyroxene and fassaite. Some chondrules contain relict grains of forsterite +/- Mg-Al spinel. We suggest that glass-rich chondrules were formed early in nebular history by melting fine-grained precursor materials rich in refractory (Ca, Al, Ti) an moderately volatite (Na, K) components (possibly related to Ca-Al-rich inclusions) admixed with coarse relict forsterite and spinel grains derived from previously disrupted type-I chondrules.

  12. Experimental Constraints on Chondrule Reduction

    NASA Astrophysics Data System (ADS)

    Libourel, G.; Chaussidon, M.

    1995-09-01

    Whether or not chondritic metal results from equilibrium condensation in the nebula [1], or reflects reduction during chondrule formation [2] is still a matter of debate. Tiny metal globules are found both in matrix of primitive meteorites and in olivine-pyroxene bearing chondrules, suggesting that reduction reactions could have been established either before or during chondrule formation. The causes of reduction processes are also controversial, either controlled by the reduced protosolar atmosphere or due to the presence of reduced carbon in the chondrule precursors [3]. These issues are of fundamental importance in understanding chondrule formation processes and conditions. In addition, because chondrules are the raw material for the Earth accretion, the understanding of the processes controlling the formation of metal (and its compositions) might be also essential for the understanding of the early differentiation of the Earth. In order to shed light on metal formation in chondrules, a series of reduction experiments were carried out to establish 1. the timing of the reduction 2. the compositional effects of reduction and 3. the causes of the reduction. San Carlos olivines, Fa16 with trace amounts of Ni, Co, P, Mn, were used as starting material, this composition being close to that of chondrules on average. Olivines were ground to 50-100 m in order to be comparable to chondrule precursors. Experiments were run in a 1 atmosphere vertical furnace, in the temperature range 1550 to 1650 C and under different oxygen fugacities (IW-1 to C-CO buffer). These reduced atmospheres were imposed by a flux of different proportions of gases (CO, CO2, H2 and Ar) or by using graphite capsules with a flux of pure CO gas. For a given T and fO2, experiments were performed with time scales of 5 mn to 8 hours, and terminated by quenching the run products in dry conditions at 500 C/sec. Each experiment produced an assemblage of olivines (Fo-rich), silicate glass and metal globules (Fe-Ni) either as tiny blebs (< 1m) included in olivine or as globules (1 to 50 m) located in the silicate melt at the olivine grain boundaries. The textural features are very similar to those observed in natural unequilibrated ordinary chondrules. Indeed, olivines may or may not show a dusty appearance, with or without preferential alignment of metal blebs in the same run products. Owing to these experiments, it is also possible to specify unambiguously the mechanism for the reduction reaction: Olivine (Fa 16) > Olivine (< Fa16) + Si-glass + Fe metal + O2. In term of composition, olivine, Fe metal and glass are drastically dependent on the imposed oxygen fugacity, run duration and temperature. Within the experimental conditions, olivines vary from Fa 16 to Fa 0.15, Fe metal from 60 wt% Ni to 2 wt% Ni, and glass from silica-poor and iron-rich composition to silica-rich and iron-poor composition. In general, olivine becomes more forsteritic as oxygen fugacity decreases and run duration increases, and for a fixed oxygen fugacity, the Ni content of metal phases shows a drastic decrease as run duration increases. Moreover, these data show that the rate of this reduction process is strongly sensitive to the temperature and the nature of the reducing agent. In the light of these textural and compositional data, this study suggests that metal in chondrules can be produced on a time scale relevant for chondrule formation by reduction reactions and that these processes could also explain the main textural and compositional features of olivine and metal observed in natural chondrules. References: [1] Grossman L. and Olsen E. (1974) GCA, 38, 173-187. [2] Scott E. R. D and Taylor G. J. (1983) Proc. LPSC 14th, in JGR, 88, B275-B286. [3] Connolly H. C. Jr. et al. (1994) Nature, 371, 136-139.

  13. Constraints on the oxidation state of chondrule precursors from titanium XANES analysis of Semarkona Chondrules

    SciTech Connect

    Simon, S.B.; Sutton, S.R.; Grossman, L.

    2008-04-28

    The valence of Ti is not easily reset during chondrule formation. To investigate the oxidation state of chondrule precursors, we measured the valence of Ti in olivine, pyroxene and mesostasis in a type I and a type II chondrule in Semarkona. Chondrules are very important because they formed in the solar nebula and are a major component of chondrites, the most common type of meteorite. In unequilibrated chondrites, the ferromagnesian silicates in chondrules exhibit wide ranges of fe (Fe/(Mg + Fe)). On this basis, chondrules can be divided into type I (fe < 0.1) and type II (fe > 0.1). Because a metal must be oxidized to enter a silicate, mafic silicates with low fe's are inferred to have formed in environments where little oxidized iron was available, implying reducing conditions. Therefore, type I and type II chondrules record different oxidation states. A fundamental question in the study of chondrules is whether this difference was established during chondrule formation, or if it reflects differences in their precursors. Last year, we reported the presence of trivalent Ti in refractory forsterite found in the dense fraction of the Tagish Lake CM chondrite. In addition, in the corresponding oral presentation, we reported high Ti{sup 3+}/Ti{sup 4+} in refractory forsterite containing 0.4-0.7 wt% FeO, present in a type I chondrule. Even these low FeO contents reflect a much higher fO{sub 2} than that at which pyroxene with equivalent Ti{sup 3+}/Ti{sup 4+} would be stable. This suggests that either: the equilibrium Ti{sup 3+}/Ti{sup 4+} is higher in olivine than in pyroxene for a given fO{sub 2}; or the grains formed under highly reducing conditions and the valence of Ti in chondrule olivine is a robust recorder of the oxidation state of chondrule precursors, not easily reset during chondrule formation. To improve our understanding of the origin of chondrules we have used XANES (X-ray absorption near edge structure) spectroscopy to measure the valence state of Ti in a type I and a type II chondrule in Semarkona (LL3.0). If olivine from type I chondrules contains Ti{sup 3+} and that from type II chondrules does not, that would tell us that either their precursors formed under different conditions, or that type IIs were more strongly oxidized during formation. If olivine in type II chondrules contains Ti{sup 3+}, that would probably mean that the precursors of these chondrules were originally reduced and that oxidation occurred during chondrule formation.

  14. Congruent Melting Kinetics: Constraints on Chondrule Formation

    NASA Technical Reports Server (NTRS)

    Greenwood, James P.; Hess, Paul C.

    1995-01-01

    The processes and mechanisms of melting and their applications to chondrule formation are discussed A model for the kinetics of congruent melting is developed and used to place constraints on the duration and maximum temperature experienced by the interiors of relict-bearing chondrules. Specifically, chondrules containing relict forsteritic olivine or enstatitic pyroxene cannot have been heated in excess of 1901 C or 1577 C, respectively, for more than a few seconds.

  15. Chondrule formation, metamorphism, brecciation, an important new primary chondrule group, and the classification of chondrules

    NASA Technical Reports Server (NTRS)

    Sears, Derek W. G.; Shaoxiong, Huang; Benoit, Paul H.

    1995-01-01

    The recently proposed compositional classification scheme for meteoritic chondrules divides the chondrules into groups depending on the composition of their two major phases, olivine (or pyroxene) and the mesostasis, both of which are genetically important. The scheme is here applied to discussions of three topics: the petrographic classification of Roosevelt County 075 (the least-metamorphosed H chondrite known), brecciation (an extremely important and ubiquitous process probably experienced by greater than 40% of all unequilibrated ordinary chondrites), and the group A5 chondrules in the least metamorphosed ordinary chondrites which have many similarities to chondrules in the highly metamorphosed 'equilibrated' chondrites. Since composition provides insights into both primary formation properties of the chondruies and the effects of metamorphism on the entire assemblage it is possible to determine the petrographic type of RC075 as 3.1 with unique certainty. Similarly, the near scheme can be applied to individual chondrules without knowledge of the petrographic type of the host chondrite, which makes it especially suitable for studying breccias. Finally, the new scheme has revealed the existence of chondrules not identified by previous techniques and which appear to be extremely important. Like group A1 and A2 chondrules (but unlike group B1 chondrules) the primitive group A5 chondruies did not supercool during formation, but unlike group A1 and A2 chondrules (and like group B1 chondrules) they did not suffer volatile loss and reduction during formation. It is concluded that the compositional classification scheme provides important new insights into the formation and history of chondrules and chondrites which would be overlooked by previous schemes.

  16. Impact jetting as the origin of chondrules.

    PubMed

    Johnson, Brandon C; Minton, David A; Melosh, H J; Zuber, Maria T

    2015-01-15

    Chondrules are the millimetre-scale, previously molten, spherules found in most meteorites. Before chondrules formed, large differentiating planetesimals had already accreted. Volatile-rich olivine reveals that chondrules formed in extremely solid-rich environments, more like impact plumes than the solar nebula. The unique chondrules in CB chondrites probably formed in a vapour-melt plume produced by a hypervelocity impact with an impact velocity greater than 10 kilometres per second. An acceptable formation model for the overwhelming majority of chondrules, however, has not been established. Here we report that impacts can produce enough chondrules during the first five million years of planetary accretion to explain their observed abundance. Building on a previous study of impact jetting, we simulate protoplanetary impacts, finding that material is melted and ejected at high speed when the impact velocity exceeds 2.5 kilometres per second. Using a Monte Carlo accretion code, we estimate the location, timing, sizes, and velocities of chondrule-forming impacts. Ejecta size estimates indicate that jetted melt will form millimetre-scale droplets. Our radiative transfer models show that these droplets experience the expected cooling rates of ten to a thousand kelvin per hour. An impact origin for chondrules implies that meteorites are a byproduct of planet formation rather than leftover building material. PMID:25592538

  17. Relationships between type I and type II chondrules: Implications on chondrule formation processes

    NASA Astrophysics Data System (ADS)

    Villeneuve, Johan; Libourel, Guy; Soulié, Camille

    2015-07-01

    In unequilibrated chondrites, the ferromagnesian silicates in chondrules exhibit wide ranges of mg# = Mg/(Mg + Fe), allowing to sub-divide porphyritic chondrules into either type I (mg# > 0.9) or type II (mg# < 0.9). Although both chondrule types formed under oxidizing conditions relative to the canonical solar nebula, it is generally inferred that type II chondrules formed in more oxidizing conditions than type I. In order to check whether this redox difference was established during chondrule formation, or reflects differences in their precursors, we have undertaken a set of experiments aimed at heating type I olivine-rich (A) chondrule proxy, i.e. forsterite + Fe metal + Ca-Mg-Si-Al glass mixtures, under oxidizing conditions. We show that high temperature (isothermal) oxidation of type IA-like assemblages is a very efficient and rapid process (e.g. few tens of minutes) to form textures similar to type IIA chondrules. Due to the rapid dissolution of Fe metal blebs, a FeO increase in the melt and in combination with the dissolution of magnesian olivine allows the melt to reach ferroan olivine saturation. Crystallization of ferroan olivine occurs either as new crystal in the mesostasis or as overgrowths on the remaining unresorbed forsterite grains (relicts). Interruption of this process at any time before its completion by rapid cooling allows to reproduce the whole range of textures and chemical diversity observed in type A chondrules, i.e. from type I to type II. Several implications on chondrule formation processes can be inferred from the presented experiments. Type I chondrules or fragments of type I chondrules are very likely the main precursor material involved in the formation of most type II chondrules. Formation of porphyritic olivine type II chondrules is very likely the result of processes generating crystal growth by chemical disequilibrium at high temperature rather than processes generating crystallization only by cooling rates. This questions the reliability of chondrule thermal history (e.g. cooling rate values) hitherto inferred for producing porphyritic textures from dynamical cooling rate experiments only. Type A chondrule formation can be a very fast process. After periods of sub-isothermal heating or slow cooling (<50 K/h) as short as several tens of minutes and no longer than few hundreds of minutes at 1500-1800 °C, type A chondrules terminates their formation by a fast cooling (>103-104 K/h) in order to preserve their glassy mesostasis. Such inferred thermal history being at odds with nebular shock models, we thus advocate that impacts on planetesimals causing rapid melting and vaporization may provide the high density and highly volatile-enriched gaseous environments required to form chondrules. In this scenario, chondrules and their diversity should result from various degrees of interaction of the ejected fragments with the impact vapor plume; the most oxidizing conditions recorded in type IIA chondrules being very likely the closest to those imposed by the impact vapor plume.

  18. Petrology and thermal history of type IA chondrules in the Semarkona (LL3.0) chondrite

    NASA Technical Reports Server (NTRS)

    Jones, R. H.; Scott, E. R. D.

    1989-01-01

    Detailed petrologic studies have been made of 15 type IA, Fe-poor, porphyritic olivine chondrules in Semarkona (LL3.0). Major and minor element concentrations in olivines, pyroxenes, and mesostases, and bulk composition so the chondrules are measured along with zoning profiles in the olivine and pyroxene crystals. The mineral compositions and textures are best interpreted in terms of closed system crystallization in which the olivines and pyroxenes crystallized in situ from a melt corresponding to the bulk composition of the chondrule. Relict olivine grains are not found in the chondrules. Crystallization probably occurred at a cooling rate of the order of 1000 C/hr. Precursor materials of the chondrules were composed of two components, one refractory Ca-, Al-, and Ti-rich, and one less refractory Si-, Fe-, Cr-, and Mn-rich. The evidence is consistent with Semarkona being one of the least metamorphosed ordinary chondrites.

  19. Trace element distributions within ordinary chondrite chondrules: Implications for chondrule formation conditions and precursors

    NASA Astrophysics Data System (ADS)

    Alexander, C. M. O'D.

    1994-08-01

    The concentrations of thirty-six lithophile elements in the major silicate phases of chondrules have been determined by ion microprobe. Two types of porphyritic chondrule olivines, "normal" and incompatible-rich, have been identified. The incompatible-rich olivines, which have forsterite contents that are greater than Fo98, appear to have formed under highly reducing conditions. The olivine and low-Ca pyroxene grains in porphyritic chondrules have relatively unfractionated L-chondrite-normalized REE abundances compared to expectations from equilibrium distribution coefficients. This is consistent with porphyritic chondrules having formed at cooling rates of the order of 1000°C/h or faster. The alkali metal (Na, K, Rb, and Cs) to Al ratios in chondrule glasses vary by two orders of magnitude, the lower values possibly being the result of volatile loss from chondrules. No correlation was found between alkali metal depletions in chondrule glasses and enrichments in the surrounding rims, but any such correlation may have been destroyed by the diffusive redistribution of these elements in rims that is likely to occur even under mild metamorphic conditions. The refractory lithophiles, with the exception of Mg, are all highly incompatible in silicate melts and are, as a result, concentrated in the chondrule glasses. The refractory lithophiles in the glass are, in most cases, unfractionated from one another suggesting that neither vapor phase nor crystal-liquid fractionation played a major role in the formation of chondrules or their precursors. Based largely on the observation that the refractory lithophiles are concentrated in the chondrule glasses, it is suggested that previously reported correlations between these elements in bulk chondrule analyses are due to chondrules themselves, as opposed to refractory condensates, having been their own immediate precursors. A simple Monte Carlo simulation using the compositions of the major chondrule silicate phases reported here supports this hypothesis. It is argued that the upper limit of about one observed in the atomic Na/Al ratios of chondule glasses is not due to an albitic precursor but simply reflects that for Na to be incorporated into the structure of the melt it must take part in the coupled substitution NaAlO 2→ SiO 2.

  20. A CRITICAL EXAMINATION OF THE X-WIND MODEL FOR CHONDRULE AND CALCIUM-RICH, ALUMINUM-RICH INCLUSION FORMATION AND RADIONUCLIDE PRODUCTION

    SciTech Connect

    Desch, S. J.; Morris, M. A.; Connolly, H. C.; Boss, Alan P.

    2010-12-10

    Meteoritic data, especially regarding chondrules and calcium-rich, aluminum-rich inclusions (CAIs), and isotopic evidence for short-lived radionuclides (SLRs) in the solar nebula, potentially can constrain how planetary systems form. Interpretation of these data demands an astrophysical model, and the 'X-wind' model of Shu et al. and collaborators has been advanced to explain the origin of chondrules, CAIs, and SLRs. It posits that chondrules and CAIs were thermally processed <0.1 AU from the protostar, then flung by a magnetocentrifugal outflow to the 2-3 AU region to be incorporated into chondrites. Here we critically examine key assumptions and predictions of the X-wind model. We find a number of internal inconsistencies: theory and observation show no solid material exists at 0.1 AU; particles at 0.1 AU cannot escape being accreted into the star; particles at 0.1 AU will collide at speeds high enough to destroy them; thermal sputtering will prevent growth of particles; and launching of particles in magnetocentrifugal outflows is not modeled, and may not be possible. We also identify a number of incorrect predictions of the X-wind model: the oxygen fugacity where CAIs form is orders of magnitude too oxidizing, chondrule cooling rates are orders of magnitude lower than those experienced by barred olivine chondrules, chondrule-matrix complementarity is not predicted, and the SLRs are not produced in their observed proportions. We conclude that the X-wind model is not relevant to chondrule and CAI formation and SLR production. We discuss more plausible models for chondrule and CAI formation and SLR production.

  1. Lunar and Planetary Science XXXV: Chondrules: The Never-Ending Story

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Chondrules: The Never-Ending Story" included the following reports:Dust Size Distribution in Solar Nebula Inferred from Shock-Wave Heating Model for Chondrule Formation; Collisional Destruction of Chondrules in Shock Waves and Inferred Dust to Gas Mass Ratio; Evaporation and Accompanying Isotopic Fractionation of Sulfur from Fe-S Melt During Shock Wave Heating ; Evaporation During Chondrule Formation, Recondensation as Fine Particles, and the Condensation of S and Other Volatile Elements; Fe Isotopes and the Formation of Chondrules; Pristine and Processed Metal in CR Chondrites: Condensation in the Solar Nebula and Partial Reequilibration During Chondrule Formation; Variation of the Condensation Path of Supercooled Silicate Melt; Volatile and Moderately Volatile Trace Element Composition of Chondrules and Matrix from CM Chondrites: Implications for Chondrule Formation; Opaque Mineral Assemblages at Chondrule Boundaries in the Vigarano CV Chondrite: Evidence for Gas-Solid Reactions Following Chondrule Formation; Forsterite and Olivine in Sahara-97210 (LL3.2) and Chainpur (LL3.4) Chondrules: Compositional Evolution and the Influence of Melting; The Vaguries of Pyroxene Nucleation and the Resulting Chondrule Textures; Contemporaneous Formation of Chondrules in the Al-26-Mg-26 System for Ordinary and CO Chondrites; and Al-Mg Isotopic Systematics in Ferromagnesian Chondrules from the Unequilibrated Ordinary Chondrite.

  2. On the origin of enstatite chondrite chondrules based on their petrography and comparison with experimentally produced chondrules

    NASA Technical Reports Server (NTRS)

    Lofgren, Gary E.; Dehart, John M.; Burkett, P. J.

    1994-01-01

    The recent discovery of several types 3 and 4 enstatite chondrites (EC) in the Antarctic collection increases greatly the ability to compare unaltered, naturally-formed EC chondrules with chondrules produced experimentally from melts of enstatitic chondrule composition. Because these discoveries are so recent we have undertaken the task of characterizing these chondrules for purposes of comparison. We have looked at several new Antarctic E3 chondrites and Qingzhen. They all have numerous chondrules with well defined outlines and readily identifiable textures. All have mostly porphyritic chondrules, but there are differences in the size and kinds of textures. Radial pyroxene, barred/dendritic px, and cryptocrystalline chondrules are present in differing amounts with one exception.

  3. Fayalitic Olivine in Matrix of the Krymka LL3.1 Chondrite

    NASA Astrophysics Data System (ADS)

    Weisberg, M. K.; Zolensky, M. E.; Prinz, M.

    1995-09-01

    INTRODUCTION. Matrix persists as one of the most poorly characterized chondritic components. Its aggregational nature makes it an excellent place to search for primitive chondritic components that prevailed in the nebula during and after chondrule formation as well as components recording processes that predated and postdated accretion. In this study we focus on the occurrence and formation of the fayalitic olivine in the matrix of the Krymka LL3.1 unequilibrated ordinary chondrite. RESULTS. We limited our study to matrix areas clearly sandwiched between chondrules and did not include chondrule rims. In Krymka, matrix is coarser-grained and more Fe-rich than the rim material. Matrix is also highly variable in the size, shape and composition of its components, whereas chondrule rims appear more uniform. Krymka matrix is an aggregation of diverse mineral and lithic components. Mineral components include olivine, enstatite, diopsidic pyroxene, Ti-Al-rich Ca-pyroxene, hedenbergite, amorphous silicate material, spinel, oxides, troilite, and metal. Olivine is clearly dominant (~75% normative) and occurs in a variety of textures and compositions. Fayalitic olivine (Fa(sub)(58-94), avg.=Fa(sub)(72)) is ubiquitous throughout the matrix and occurs as (1) Isolated platelets (typically 1-3 micrometers x 3-5 micrometers, with some up to 10 micrometers in length), (2) Platelet clusters, which include randomly oriented platelets and/or intergrown platelets, (3) Platelet overgrowths which are overgrowths of parallel platelets on surfaces of larger (10-300 micrometers), more magnesian (Fa(sub)(4-34), avg.=Fa(sub)(19)) olivine fragments, (4) Euhedral-subhedral crystals (1-10 micrometers) which are often associated with and compositionally similar to platelets, and (5) Fluffy aggregates - irregularly shaped porous aggregates of submicron crystals. TEM study of the overgrowths reveals that the direction of elongation of the fayalitic platelets is along the c axis corresponding with the c direction of the larger olivine substrate. The larger, more magnesian olivine fragments are generally single crystals, but in some cases are associated with pyroxene (Fs(sub)(5-27),Wo(sub)(0.5-2)) or high-Ca pyroxene. These larger olivines are compositionally similar to chondrule olivines, whereas the fayalitic platelets are texturally and compositionally unlike olivines in chondrules. Fayalitic olivine with morphologies similar to those in Krymka matrix occur in the Chainpur LL3.4 and Ngawi LL3 matrix, but are much less common. These textures may have been characteristic of all primitive ordinary chondrite matrix, but were generally overprinted by metamorphic recrystallization. DISCUSSION: Fayalitic olivine in Krymka matrix records a process that has important implications for understanding the evolution of ordinary chondrites. It may form under oxidizing nebular conditions through solid state reactions in the presence of free silica, or vapor-solid reactions in a gas with a high silica activity [1,2]. Textural observations have been used to support a nebular origin for similar fayalitic olivine in CV3 matrix, and thermodynamic calculations indicate it could form in a nebula with a supersolar H2O/H2 ratio [3]. Vaporization experiments show that at ~10^(-6) bar and ~1650K olivine evaporates incongruently to produce a fayalitic vapor [4]. However, textural arguments favoring post-accretion formation of the fayalitic olivine in ordinary chondrite matrix and in CV3 dark inclusions have also been presented [5,6]. Thus, we consider three hypotheses for the formation of the fayalitic olivine in Krymka matrix: (1) vapor-solid reactions between a silica-rich vapor and metallic Fe degrees in the nebula, (2) vaporization of olivine-rich material to produce a fayalite vapor, followed by recondensation, or (3) parent body heating/dehydration of pre-existing phyllosilicates. Although the platy layered structure of some of the fayalitic olivine is suggestive of the layered structures of phyllosilicates and some fayalitic olivine texturally resembles saponite replacing olivine (as observed in the Kaidun CR chondrite), the platelet overgrowths on larger olivine crystals probably represent growth features and not a replacement of phyllosilicates. The platy morphology of fayalitic olivine could also indicate growth from a vapor consistent with hypotheses 1 and 2. The wide range in compositions of associated fayalitic olivine platelets suggests that they did not all form in the same environment and were not in contact under high enough temperatures to result in equilibrium; therefore, we conclude that the fayalitic olivine formed in a nebular environment. The fayalitic olivine platelets and associated fayalitic olivine in Krymka matrix may record vapor solid reactions under oxidizing nebular conditions or partial evaporation of a more Mg-rich olivine to produce a fayalite vapor, followed by recondensation. Formation through heating/dehydration of phyllosilicates is less likely. References. [1] Nagahara H. (1984) GCA, 48, 2581-2595. [2] Nagahara H. and Kushiro I. (1987) EPSL, 85, 537-547. [3] Hua X. and Buseck P. R. (1995) GCA, 59, 563-578. [4] Nagahara H. et al. (1994) GCA, 58, 1951-1963. [5] Alexander C. M. et al. (1989) EPSL, 95, 187-207. [6] Kojima T. and Tomeoka K. (1994) Meteoritics, 29, 484.

  4. The lack of potassium-isotopic fractionation in Bishunpur chondrules

    USGS Publications Warehouse

    Alexander, C.M. O'D.; Grossman, J.N.; Wang, Jingyuan; Zanda, B.; Bourot-Denise, M.; Hewins, R.H.

    2000-01-01

    In a search for evidence of evaporation during chondrule formation, the mesostases of 11 Bishunpur chondrules and melt inclusions in olivine phenocrysts in 7 of them have been analyzed for their alkali element abundances and K-isotopic compositions. Except for six points, all areas of the chondrules that were analyzed had δ41K compositions that were normal within error (typically ±3%, 2s̀). The six “anomalous” points are probably all artifacts. Experiments have shown that free evaporation of K leads to large 41K enrichments in the evaporation residues, consistent with Rayleigh fractionation. Under Rayleigh conditions, a 3% enrichment in δ41K is produced by ∼12% loss of K. The range of L-chondrite-normalized K/Al ratios (a measure of the K-elemental fractionation) in the areas analyzed vary by almost three orders of magnitude. If all chondrules started out with L-chondrite-like K abundances and the K loss occurred via Rayleigh fractionation, the most K-depleted chondrules would have had compositions of up to δ41K ≅ 200%. Clearly, K fractionation did not occur by evaporation under Rayleigh conditions. Yet experiments and modeling indicate that K should have been lost during chondrule formation under currently accepted formation conditions (peak temperature, cooling rate, etc.). Invoking precursors with variable alkali abundances to produce the range of K/Al fractionation in chondrules does not explain the K-isotopic data because any K that was present should still have experienced sufficient loss during melting for there to have been a measurable isotopic fractionation. If K loss and isotopic fractionation was inevitable during chondrule formation, the absence of K-isotopic fractionation in Bishunpur chondrules requires that they exchanged K with an isotopically normal reservoir during or after formation. There is evidence for alkali exchange between chondrules and rim-matrix in all unequilibrated ordinary chondrites. However, melt inclusions can have alkali abundances that are much lower than the mesostases of the host chondrules, which suggests that they at least remained closed since formation. If it is correct that some or all melt inclusions remained closed since formation, the absence of K-isotopic fractionation in them requires that the K-isotopic exchange took place during chondrule formation, which would probably require gas-chondrule exchange. Potassium evaporated from fine-grained dust and chondrules during chondrule formation may have produced sufficient K-vapor pressure for gas-chondrule isotopic exchange to be complete on the timescales of chondrule formation. Alternatively, our understanding of chondrule formation conditions based on synthesis experiments needs some reevaluation.

  5. Oxygen Isotope Systematics of Chondrules from the Least Equilibrated H Chondrite

    NASA Technical Reports Server (NTRS)

    Kita, N. T.; Kimura, M.; Ushikubo, T.; Valley, J. W.; Nyquist, L. E.

    2008-01-01

    Oxygen isotope compositions of bulk chondrules and their mineral separates in type 3 ordinary chondrites (UOC) show several % variability in the oxygen three isotope diagram with slope of approx.0.7 [1]. In contrast, ion microprobe analyses of olivine and pyroxene phenocrysts in ferromagnesian chondrules from LL 3.0-3.1 chondrites show mass dependent isotopic fractionation as large as 5% among type I (FeO-poor) chondrules, while type II (FeO-rich) chondrules show a narrow range (less than or equal to 1%) of compositions [2]. The .Delta(exp 17)O (=delta(exp 17)O-0.52xdelta(exp 18)O) values of olivine and pyroxene in these chondrules show a peak at approx.0.7% that are systematically lower than those of bulk chondrule analyses as well as the bulk LL chondrites [2]. Further analyses of glass in Semarkona chondrules show .17O values as high as +5% with highly fractionated d18O (max +18%), implying O-16-poor glass in chondrules were altered as a result of hydration in the parent body at low temperature [3]. Thus, chondrules in LL3.0-3.1 chondrites do not provide any direct evidence of oxygen isotope exchange between solid precursor and O-16-depleted gas during chondrule melting events. To compare the difference and/or similarity between chondrules from LL and H chondrites, we initiated systematic investigations of oxygen isotopes in chondrules from Yamato 793408 (H3.2), one of the least equilibrated H chondrite [4]. In our preliminary study of 4 chondrules, we reported distinct oxygen isotope ratios from dusty olivine and refractory forsterite (RF) grains compared to their host chondrules and confirmed their relict origins [5].

  6. A systematic for oxygen isotopic variation in meteoritic chondrules

    NASA Astrophysics Data System (ADS)

    Marrocchi, Yves; Chaussidon, Marc

    2015-11-01

    Primitive meteorites are characteristically formed from an aggregation of sub-millimeter silicate spherules called chondrules. Chondrules are known to present large three-isotope oxygen variations, much larger than shown by any planetary body. We show here that the systematic of these oxygen isotopic variations results from open-system gas-melt exchanges during the formation of chondrules, a conclusion that has not been fully assessed up to now. We have considered Mg-rich porphyritic chondrules and have modeled the oxygen isotopic effects that would result from high-temperature interactions in the disk between precursor silicate dust and a gas enriched in SiO during the partial melting and evaporation of this dust. This formation process predicts: (i) a range of oxygen isotopic composition for bulk chondrules in agreement with that observed in Mg-rich porphyritic chondrules, and (ii) variable oxygen isotopic disequilibrium between chondrule pyroxene and olivine, which can be used as a proxy of the dust enrichment in the chondrule-forming region(s). Such enrichments are expected during shock waves that produce transient evaporation of dust concentrated in the mid-plane of the accretion disk or in the impact plumes generated during collisions between planetesimals. According to the present model, gas-melt interactions under high PSiO(gas) left strong imprints on the major petrographic, chemical and isotopic characteristics of Mg-rich porphyritic chondrules.

  7. Evidence for relict grains in chondrules of Qingzhen, an E3 type enstatite chondrite

    NASA Technical Reports Server (NTRS)

    Rambaldi, E. R.; Rajan, R. S.; Wang, D.; Housley, R. M.

    1983-01-01

    Petrographic and chemical studies of the Qingzhen chondrite strongly suggest that it is the most highly unequilibrated (type 3) enstatite chondrite recognized so far. Qingzhen contains abundant, well-defined chondrules, some of which were incompletely molten during the chondrule formation process. The relict olivine grains within these chondrules contain dusty inclusions of almost pure metallic Fe, which appear to be the in situ reduction product of the fayalitic component of the olivine. The reduction process presumably took place at the time of chondrule formation and the chondrule precursor material must have been more oxidized than average enstatilite chondrite material. It is believed that this oxidized material may have formed at the enstatite chondrite formation location in the solar nebula, provided fluctuations in the degree of oxidation of the nebular gas existed at such locations. Reheating of this material under more reducing conditions would lead to the observed reduction of the olivine. Igneous olivines within chondrules always contain detectable amounts of CaO, while relict olivines are essentially CaO-free. This seems to suggest thatg the relict olivines did not originate during a previous igenous process of chondrule formation and might represent condensation products from the early solar nebula.

  8. Properties of chondrules

    NASA Technical Reports Server (NTRS)

    Grossman, Jeffrey N.; Rubin, Alan E.; Nagahara, Hiroko; King, Elbert A.

    1988-01-01

    Chondrules contain a record of many essential characteristics of the primordial solar nebula, whose high-temperature chondrule-generating events have spanned nearly 10 million years. As chondrules cooled, they became magnetized by nebular fields; chondrule rims show that dust was present in the vicinity of chondrule formation, and that multiple melting events were possible. The chondrule precursors included many large grains, showed variable degrees of Fe-oxidation, and encompassed many isotopic reservoirs. The properties of these nebular materials systematically changed from the enstatite, to ordinary, and finally to carbonaceous chondrite formation regions.

  9. Vesicles in Experimental Chondrules as Clues to Chondrule Precursors

    NASA Astrophysics Data System (ADS)

    Maharaj, S. V.; Hewins, R. H.

    1993-07-01

    The processing of chondrule precursors during melting is so extensive that there are few unambiguous indicators of their mineralogical composition. The specific combination of peak temperature and heating time, i.e., the heating mechanism, is also unknown. The general absence of vesicles in chondrules is a potential constraint on both questions. Meteor ablation spherules, whose origins are well understood, differ from chondrules in having abundant vesicles [1]. Chondrules simulated experimentally in a variety of ways have vesicles in many cases, but it has been suggested that the presence of vesicles rules out flash heating [2]. We therefore examine in detail the formation of vesicles in synthetic chondrules. Vesicles have been produced in experiments with long heating times [3] as well as short [2]. They are most prominent in charges that experienced low degrees of melting, probably because of surface tension effects that trap bubbles between relict grains, aided by high melt viscosity. The gas could be derived from air trapped when the powdered sample is prepared, binding agents (acetone, water), or volatiles in the starting minerals (Na, H2O). We have conducted experiments to determine the source of vesicles in synthetic chondrules initially heated slightly below the liquidus and cooled at 500 degrees C/hr. Runs made in pairs included charges with and without acetone binder and charges baked out at 200 degrees C for different lengths of time. Charges with acetone produced more vesicles, which could be avoided to some extent by preliminary baking. Charges with no binder had very few vesicles if baked for 1/2 hour. Vesicles are more prominent when using a well-sorted fine-grained powder than with an unsorted more uniform size distribution. Pulling a vacuum on pellets had no effect on subsequent vesicle development. Vesicles are unlikely to be due to loss of Na from the charge, because vesicles are equally prevalent in flash-heated charges, which retain most of their Na, and earlier experiments that spent longer times at temperature. Experiments with serpentine in the starting materials resulted in a popcorn vesicle texture with voids as large as 3 mm, like some ablation spherules [1]. Trapped air and binding agents cause most vesicles in experimental charges. Chondrule precursors must have consisted of olivine, etc., with no hydrous minerals, assembled at low pressure, or they would have generated vesicles. The absence of vesicles in chondrules does not rule out flash heating mechanisms. References: [1] Brownlee D. E. et al. (1983) In Chondrules and Their Origin (E. A. King, ed.), 10-25, LPI, Houston. [2] Wdowiak T. J. (1983) In Chondrules and Their Origin (E. A. King, ed.), 279-283, LPI, Houston. [3] Radomsky P. M. and Hewins R. H. (1990) GCA, 54, 3475-3490.

  10. Young Pb-Isotopic Ages of Chondrules in CB Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Amelin, Yuri; Krot, Alexander N.

    2005-01-01

    CB (Bencubbin-type) carbonaceous chondrites differ in many ways from more familiar CV and CO carbonaceous chondrites and from ordinary chondrites. CB chondrites are very rich in Fe-Ni metal (50-70 vol%) and contain magnesian silicates mainly as angular to sub-rounded clasts (or chondrules) with barred olivine (BO) or cryptocrystalline (CC) textures. Both metal and silicates appear to have formed by condensation. The sizes of silicate clasts vary greatly between the two subgroups of CB chondrites: large (up to one cm) in CB(sub a) chondrites, and typically to much much less than 1 mm in CB(sub b) chondrites. The compositional and mineralogical differences between these subgroups and between the CB(sub s) and other types of chondrites suggest different environment and possibly different timing of chondrule formation. In order to constrain the timing of chondrule forming processes in CB(sub s) and understand genetic relationship between their subgroups, we have determined Pb-isotopic ages of silicate material from the CB(sub a) chondrite Gujba and CB(sub b) chondrite Hammadah al Hamra 237 (HH237 hereafter).

  11. Composition of chondrule silicates in LL3-5 chondrites and implications for their nebular history and parent body metamorphism

    NASA Technical Reports Server (NTRS)

    Mccoy, Timothy J.; Scott, Edward R. D.; Keil, Klaus; Taylor, G. Jeffrey; Jones, Rhian H.

    1991-01-01

    The composition of 75 type-IA and type-II porphyritic olivine chondrules from nine LL type 3 to type 5 chondrites was determined and was compared with that of chondrules from the Semarkona type 3.0 meteorite. Chemical data for silicates in the LL3.3-5 chondrites indicated that porphyritic olivine chondrules in these chondrites could be derived from chondrules similar to those from the Semarkona LL3.0, the least metamorphosed one of the known LL chondrites. It is shown that the chemical trends defined by the minerals of type-IA and type-II chondrules can be satisfactorily accounted for by the process of solid-state diffusive equilibration between minerals in chondrules and the opaque matrix rather than by changes in conditions during chondrule crystallization.

  12. Petrology of FeO-poor, porphyritic pyroxene chondrules in the Semarkona chondrite

    NASA Astrophysics Data System (ADS)

    Jones, Rhian H.

    1994-12-01

    The mineralogy and petrology of FeO-poor, porphyritic, pyroxene- and olivine-rich chondrules in the Semarkona (LL3.0) chondrite are described in detail. In an extension of the textural classification scheme, these chondrules are designated types IAB and IB. In type IAB chondrules, the proportion of olivine phenocrysts is between 20-80% and in type IB chondrules, olivine constitutes <20% of the phenocryst assemblage. All the chondrules studied are FeO-poor and contain olivine and low-Ca pyroxene phenocrysts in varying proportions. Olivine is present both as chadacrysts enclosed in low-Ca pyroxene and as larger phenocrysts. Ca-rich pyroxene occurs commonly as rims on low-Ca pyroxene phenocrysts. Lamellar zoning in low-Ca pyroxene, observed in backscattered electron images, is interpreted as a primary growth feature. Apparent partition coefficients between phenocrysts and mesostasis for major and minor elements are consistent with crystallization of an essentially molten chondrule at rapid cooling rates (100-1000°C/h). Within the entire type I series, there are continuous changes in textural and compositional properties that suggest common origins for all chondrules in this series. These properties include proportions of olivine and pyroxene phenocrysts, FeO contents of olivine and pyroxene phenocrysts and a complementary relationship between the proportions of refractory elements and Si-, Fe-rich precursor components in chondrule bulk compositions. Observations of the behavior of Na suggest that evaporation and recondensation of volatile elements was not an important process during formation of type I chondrules and that abundances of volatile elements were largely controlled by the abundance of a volatile-rich precursor component.

  13. The Formation of Chondrules: Petrologic Tests of the Shock Wave Model

    NASA Technical Reports Server (NTRS)

    Connolly, H. C., Jr.; Love, S. G.

    1998-01-01

    Chondrules are mm-sized spheroidal igneous components of chondritic meteorites. They consist of olivine and orthopyroxene set in a glassy mesostasis with varying minor amounts of metals, sulfieds, oxides and carbon phases.

  14. Serpentinisation of Chondrules in the Murchison CM Carbonaceous Chondrite by Centripetal Replacement and Cementation

    NASA Astrophysics Data System (ADS)

    Lee, M. R.; Lindgren, P.

    2015-07-01

    We have found that phenocrysts in Murchison chondrules contain serpentine. Olivine-hosted veins have formed by replacement whereas polyhedral serpentine has formed by cementation of pores within clinoenstatite grains.

  15. Troilite in the Chondrules of Type-3 Ordinary Chondrites: Implications for Chondrule Formation

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Sailer, Alan L.; Wasson, John T.

    1999-01-01

    The presence of primary troilite in chondrules requires that nebular temperatures were <650 K (the 50% condensation temperature of S) at the time of chondrule formation and that chondrules were molten for periods short enough (less than or equal to 10 s) to avoid significant volatilization of S. We examined 226 intact chondrules of all textural types from eight unshocked to weakly shocked ordinary chondrite falls of low petrologic type to determine the origin of troilite in chondrules; 68 chondrules are from LL3.0 Semarkona. There is a high probability that troilite is primary (i.e , was present among the chondrule precursors) if it is completely embedded in a mafic silicate phenocryst, located within one-half radius of the apparent chondrule center and is part of an opaque assemblage with an igneous texture Based on these criteria, 13% of the chondrules in Semarkona and in the set as a whole contain primary troilite. Most of the remaining chondrules contain troilite that is probably primary, but does not meet all three criteria. Troilite occurs next to tetratacnite in some opaque spherules within low-FeO chondrules in Semarkona, implying that the Ni required to form the tetrataenite came from the troilite Troilite can accommodate 5 mg/g Ni at high temperatures (> 1170 K) but much less Ni at lower temperatures; because this is far higher than the metamorphic temperature inferred for Semarkona (approx. 670 K), the troilite must be primary Primary troilite fitting the three criteria occurs in a smaller fraction of low-FeO [FeO/(FeO + MgO) in olivine and/or low-Ca pyroxene not greater than 0.0751 than high-FeO porphyritic chondrules in Semarkona (9% vs 33%) Coarse-grained low-FeO porphyritic chondrules appear to contain somewhat more troilite on average than those of medium grain size We found a few troilite-free, metallic-Fe-Ni-bearing, low-FeO chondrules that contain Na2O-bearing augite and Na2O- and K2O-rich mesostasis; these chondrules were probably formed after ambient nebular temperatures cooled below 910 K (the 50% condensation temperature of Na) and before they reached 650 K Literature reports of rare fayalitic microchondrules in the rims around a few normal-size chondrules suggest that chondrule formation persisted until nebular temperatures cooled below 500 K Secondary troilite occurs in a few percent of Semarkona chondrules as thin veins mobilized by shock; troilite or pyrrhotite in the outer portions of some chondrules occur within opaque assemblages containing magnetite, carbide, Ni-rich sulfide, awaruite, and Co-rich kamacite produced by parent-body hydrothermal alteration.

  16. Compound chondrules fused cold

    NASA Astrophysics Data System (ADS)

    Hubbard, Alexander

    2015-07-01

    About 4-5% of chondrules are compound: two separate chondrules stuck together. This is commonly believed to be the result of the two component chondrules having collided shortly after forming, while still molten. This allows high velocity impacts to result in sticking. However, at T ∼ 1100 K, the temperature below which chondrules collide as solids (and hence usually bounce), coalescence times for droplets of appropriate composition are measured in tens of seconds. Even at 1025 K, at which temperature theory predicts that the chondrules must have collided extremely slowly to have stuck together, the coalescence time scale is still less than an hour. These coalescence time scales are too short for the collision of molten chondrules to explain the observed frequency of compound chondrules. We suggest instead a scenario where chondrules stuck together in slow collisions while fully solid; and the resulting chondrule pair was subsequently briefly heated to a temperature in the range of 900-1025 K. In that temperature window the coalescence time is finite but long, covering a span of hours to a decade. This is particularly interesting because those temperatures are precisely the critical window for thermally ionized MRI activity, so compound chondrules provide a possible probe into that vital regime.

  17. Chondrule magnetic properties

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Obryan, M. V.

    1994-01-01

    The topics discussed include the following: chondrule magnetic properties; chondrules from the same meteorite; and REM values (the ratio for remanence initially measured to saturation remanence in 1 Tesla field). The preliminary field estimates for chondrules magnetizing environments range from minimal to a least several mT. These estimates are based on REM values and the characteristics of the remanence initially measured (natural remanence) thermal demagnetization compared to the saturation remanence in 1 Tesla field demagnetization.

  18. Petrology and mineralogy of Type II, FeO-rich chondrules in Semarkona (LL3.0) - Origin by closed-system fractional crystallization, with evidence for supercooling

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.

    1990-01-01

    The petrology of type II porphyritic olivine chondrules in Semarkona (LL3.0) has been studied in detail. Olivines in these chondrules are euhedral, Fe-rich, and are strongly zoned from cores to rims of grains in FeO (Fa10-30), Cr2O3 (0.2-0.6 wt pct), MnO (0.2-0.7 wt pct), and CaO (0.1-0.4 wt pct). Interstitial mesostasis is rich in Si, Al, and Ca and is glassy with abundant microcrystallites. Minor minerals include troilite, Fe,Ni metal, and chromite. Some olivine grains contain euhedral, fayalite-rich cores that are probably produced during initial supercooling of the chondrule melt. Rare relict grains of forsteritic olivine have compositions very similar to olivines in type IA chondrules in Semarkona and may result from disaggregation of such chondrules. Apart from these relics, all properties of type II chondrules can be described by closed-system fractional crystallization of droplets which were essentially entirely molten. Type IA chondrules may have formed from type II chondrules by loss of Fe and volatiles. Alternatively, the two chondrule types may have formed in regions of considerable diversity in the solar nebula from precursor materials with different Fe/Mg ratios.

  19. Silica Under- and Oversaturated Mineral Assemblages in Chondrule Mesostases

    NASA Astrophysics Data System (ADS)

    Bridges, J. C.; Hutchison, R.

    1995-09-01

    In chondrules of unequilibrated ordinary chondrites (UOC's), mesostases sometimes have compositions that are not in equilibrium with the co-existing minerals. Examples include highly silica-oversaturated mesostases in porphyritic olivine chondrules and feldspathoid-bearing mesostases in radiating pyroxene (enstatite) chondrules [1]. As part of a larger study of chondrules and clasts in UOC's, we report the results of a survey of the mineral assemblages in mesostases. Silica enrichment can manifest itself in mesostasis glass, with SiO2 contents up to 73wt%, or as silica polymorphs. Neither of these assemblages are in equilibrium with the olivine phenocrysts which comprise the bulk of the chondrules. Chondrule CC35 (type IIA [2]) separated from Chainpur (LL3.4) is an example of the latter. Mesostasis comprising 10% of CC35 contains An(sub)69-83, Ca-px (En(sub)44-52, Fs(sub)17-18, Wo(sub)31-39) and a silica polymorph. Silica oversaturation in chondrules can readily be attributed to abundant metastable olivine crystallisation, which drives residua towards quartz-, diopside- and feldspar-rich normative compositions. This could occur in chondrules crystallising as closed systems, so sampling of a larger, chemically fractionated reservoir need not necessarily be invoked, although silica-rich clasts provide evidence that an analogous process occurred in larger, open igneous systems [3]. Some silica undersaturated mineral assemblages in mesostases may also be explained by closed system crystallisation within chondrules. A radiating pyroxene chondrule in Chainpur (Chr1) contains interstitial nepheline and scapolite. Metastable crystallisation of enstatite from an initially chondritic melt composition, at low pressure, can create silica undersaturated residua. The LREE-enriched abundances of the Chr1 mesostasis minerals are consistent with this, having up to 19 x OC La and Eu/Eu* = 10 [4]. Similarly nepheline-bearing mesostasis identified in two Parnallee (LL3.6) chondrules (P6, P22), may have crystallised from residual chondrule liquid. Other feldspathoid occurrences in chondrule mesostases cannot be explained in this way. Chondrule CC1 (type IIAB, Chainpur) consists of sodalite (<= 7wt% Cl), nepheline, An(sub)88-91 and pyroxene (En(sub)75, Fs(sub)16, Wo(sub)9) dendrites in a texture suggesting devitrification. This alkaline assemblage cannot simply be a residuum following crystallisation of the phenocrysts, because they are predominantly olivine. Mobilisation of alkali fluids within UOC parent bodies, after the formation of chondrules, is probably responsible for "white matrix" [4] but low temperature metasomatism cannot be invoked for CC1 because its texture indicates that the mesostasis assemblage is derived from a melt. Instead, there could have been a late influx of alkali elements into the precursor melt. A similar conclusion was reached for the FELINE nepheline-rich clast [5] and the feldspathoid-bearing SA-1 basaltic clast [6]. If true, the CC1 precursor melt may, like that of FELINE, have originated within an open igneous system on a planetary body. Oxygen isotopic data is being collected on these and other samples in order to help ascertain whether the alkali-enriched melts envisaged are from normal OC reservoirs or exotic sources [5]. References: [1] Alexander C. M. O'D. et al. (1994) LPS XXV, 11-12. [2] Scott E. R. D. et al. (1994) GCA, 58, 1203-1209. [3] Bridges J. C. et al. (1995) Meteoritics, submitted. [4] Hutchison R. et al. (1994) Meteoritics, 29, 476-477. [5] Bridges J. C. et al. (1995) Proc. NIPR Symp. Antarct. Met., 8, in press. [6] Kennedy A. K. and Hutcheon I. D. (1992) Meteoritics, 27, 539-554.

  20. Terminal particle from Stardust track 130: Probable Al-rich chondrule fragment from comet Wild 2

    NASA Astrophysics Data System (ADS)

    Joswiak, D. J.; Nakashima, D.; Brownlee, D. E.; Matrajt, G.; Ushikubo, T.; Kita, N. T.; Messenger, S.; Ito, M.

    2014-11-01

    A 4 × 6 μm terminal particle from Stardust track 130, named Bidi, is composed of a refractory assemblage of Fo97 olivine, Al- and Ti-bearing clinopyroxene and anorthite feldspar (An97). Mineralogically, Bidi resembles a number of components found in primitive chondritic meteorites including Al-rich chondrules, plagioclase-bearing type I ferromagnesian chondrules and amoeboid olivine aggregates (AOAs). Measured widths of augite/pigeonite lamellae in the clinopyroxene indicate fast cooling rates suggesting that Bidi is more likely to be a chondrule fragment than an AOA. Bulk element concentrations, including an Al2O3 content of 10.2 wt%, further suggests that Bidi is more akin to Al-rich rather than ferromagnesian chondrules. This is supported by high anorthite content of the plagioclase feldspar, overall bulk composition and petrogenetic analysis using a cosmochemical Al2O3-Ca2SiO4-Mg2SiO4 phase diagram. Measured minor element abundances of individual minerals in Bidi generally support an Al-rich chondrule origin but are not definitive between any of the object types. Oxygen isotope ratios obtained from olivine (+minor high-Ca pyroxene)fall between the TF and CCAM lines and overlap similar minerals from chondrules in primitive chondrites but are generally distinct from pristine AOA minerals. Oxygen isotope ratios are similar to some minerals from both Al-rich and type I ferromagnesian chondrules in unequilibrated carbonaceous, enstatite and ordinary chondrites. Although no single piece of evidence uniquely identifies Bidi as a particular object type, the preponderance of data, including mineral assemblage, bulk composition, mineral chemistry, inferred cooling rates and oxygen isotope ratios, suggest that Bidi is more closely matched to Al-rich chondrules than AOAs or plagioclase-bearing type I ferromagnesian chondrules and likely originated in a chondrule-forming region in the inner solar system.

  1. Cosmogenic neon in grains separated from individual chondrules: Evidence of precompaction exposure in chondrules

    NASA Astrophysics Data System (ADS)

    Das, J. P.; Goswami, J. N.; Pravdivtseva, O. V.; Meshik, A. P.; Hohenberg, C. M.

    2012-11-01

    Neon was measured in 39 individual olivine (or olivine-rich) grains separated from individual chondrules from Dhajala, Bjurböle, Chainpur, Murchison, and Parsa chondrites with spallation-produced 21Ne the result of interaction of energetic particle irradiation. The apparent 21Ne cosmic ray exposure (CRE) ages of most grains are similar to those of the matrix with the exception of three grains from Dhajala and single grains from Bjurböle and Chainpur, which show excesses, reflecting exposure to energetic particles prior to final compaction of the object. Among these five grains, one from chondrule BJ2A5 of Bjurböle shows an apparent excess exposure age of approximately 20 Ma and the other four from Dhajala and Chainpur have apparent excesses, described as an "age," from 2 to 17 Ma. The precompaction irradiation effects of grains from chondrules do not appear to be different from the effects seen in olivine grains extracted from the matrix of CM chondrites. As was the case for the matrix grains, there appears to be insufficient time for this precompaction irradiation by the contemporary particle sources. The apparent variations within single chondrules appear to constrain precompaction irradiation effects to irradiation by lower energy solar particles, rather than galactic cosmic rays, supporting the conclusion derived from the precompaction irradiation effects in CM matrix grains, but for totally different reasons. This observation is consistent with Chandra X-Ray Observatory data for young low-mass stars, which suggest that our own Sun may have been 105 times more active in an early naked T-Tauri phase (Feigelson et al. 2002).

  2. Oxygen-isotope compositions of chondrule phenocrysts and matrix grains in Kakangari K-grouplet chondrite: Implication to a chondrule-matrix genetic relationship

    NASA Astrophysics Data System (ADS)

    Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.

    2015-02-01

    To investigate a possible relationship between chondrules and matrix, we studied mineralogy, mineral chemistry, and in situ O-isotope compositions of chondrules, clastic matrix grains, and amoeboid olivine aggregates (AOAs) in the Kakangari K-grouplet chondrite. Most olivines and low-Ca pyroxenes in the Kakangari chondrules, matrix, and AOAs have similar magnesium-rich compositions, Fo∼95-97 (∼0.3-0.5 wt% MnO) and En∼90-96, respectively. These rather uniform chemical compositions of the different chondritic components are likely due to partial Fe-Mg-Mn equilibration during thermal metamorphism experienced by the host meteorite. Oxygen-isotope compositions of olivine and low-Ca pyroxene grains in chondrules and matrix plot along a slope-1 line on a three O-isotope diagram and show a range from 16O-enriched composition similar to that of the Sun to 16O-depleted composition similar to the terrestrial O-isotope composition. Most olivines and low-Ca pyroxenes in chondrules are 16O-poor and plot on or close to the terrestrial mass-fractionation line (mean Δ17O values ±2 standard deviations: 0.0 ± 0.8‰ and +0.2 ± 0.9‰ for olivine and pyroxene, respectively), consistent with the previously reported compositions of bulk chondrules (Δ17O = -0.16 ± 0.70‰). In addition to these 16O-poor grains, a coarse-grained igneous rim surrounding a porphyritic chondrule contains abundant 16O-rich relict olivines (Δ17O ∼ -24‰). Oxygen-isotope compositions of olivines and low-Ca pyroxenes in matrix show a bimodal distribution: 12 out of 13 olivine and 4 out of 17 pyroxene grains measured are similarly 16O-rich (Δ17O ∼ -23.5 ± 2.9‰), others are similarly 16O-poor (Δ17O ∼ -0.1 ± 1.7‰). Due to slow oxygen self-diffusion, olivines and low-Ca pyroxenes largely retained their original oxygen-isotope compositions. The nearly identical O-isotope compositions between the chondrule phenocrysts and the 16O-poor matrix grains suggest both chondrules and matrix of Kakangari sampled isotopically the same reservoirs. In addition, the presence of abundant 16O-rich grains in matrix and the chondrule igneous rim suggests both components acquired similar precursor inventories. These observations imply that chondrules and matrix in Kakangari are genetically related in the sense that material that formed matrix was one of the precursors of chondrules and chondrules and some fraction of matrix experienced the same thermal processing event. The 16O-enriched bulk matrix value compared to the bulk chondrules reported previously is likely due to presence of abundant 16O-rich grains in the Kakangari matrix.

  3. Carbon, CAIs and chondrules

    NASA Technical Reports Server (NTRS)

    Ash, R. D.; Russell, S. S.

    1994-01-01

    It has been shown that C is present in CAI's and chondrules. It can be distinguished from matrix C both by its thermal stability and isotopic composition, which implies that it was not introduced after parent body accretion. It is concluded that C must have been present in the chondrule and CAI precursor material. Therefore any models of chondrule and CAI formation and inferences drawn about solar system conditions during these events must take into account the consequences of the presence of C on inclusion chemistry, mineralogy, and oxidation state.

  4. Chondrule Crystallization Experiments

    NASA Technical Reports Server (NTRS)

    Hweins, R. H.; Connolly, H. C., Jr.; Lofgren, G. E.; Libourel, G.

    2004-01-01

    Given the great diversity of chondrules, laboratory experiments are invaluable in yielding information on chondrule formation process(es) and for deciphering their initial conditions of formation together with their thermal history. In addition, they provide some critical parameters for astrophysical models of the solar system and of nebular disk evolution in particular (partial pressures, temperature, time, opacity, etc). Most of the experiments simulating chondrules have assumed formation from an aggregate of solid grains, with total pressure of no importance and with virtually no gain or loss of elements from or to the ambient environment. They used pressed pellets attached to wires and suffered from some losses of alkalis and Fe.

  5. Are some chondrule rims formed by impact processes? Observations and experiments.

    PubMed

    Bunch, T E; Schultz, P; Cassen, P; Brownlee, D; Podolak, M; Lissauer, J; Reynolds, R; Chang, S

    1991-01-01

    Observations and experimental evidence are presented to support the hypothesis that high-speed impact into a parent body regolith can best explain certain textures and compositions observed for rims on some chondrules. A study of 19 interclastic rimmed chondrules in the Weston (H 3/4) ordinary chondrite shows that two main rim types are present on porphyritic olivine-pyroxene (POP) and porphyritic pyroxene (PP) chondrules: granular and opaque rims. Granular rims are composed of welded, fine-grained host chondrule fragments. Bulk compositions of granular rims vary among chondrules, but each rim is compositionally dependent on that of the host chondrule. Opaque rims contain mineral and glass compositions distinctly different from those of the host, partially reacted chondrule mantle components, and some matrix grains. Opaque rims are greatly enriched in FeO (up to 63 wt%). The original chondrule pyroxene compositional zonation patterns and euhedral grain outlines are discontinuous at the chondrule/rim interface. Opaque rims are dominated by fayalitic olivine (Fa92-56), with high Al2O3 content (0.78-3.15%), which makes them distinctly different from primary olivine, but similar to Fe-olivine in chondrule rims of other meteorites. Thin zones of chondrule minerals adjacent to the present rims are intermediate in FeO content between the Mg-rich interior and the Fe-rich rim, which indicates a reaction relationship. Regardless of conclusions drawn regarding other types of rims, granular and opaque rim characteristics appear to be inconsistent with nebular condensation, in that host and matrix fragments are included within the rim. We have initiated a series of experiments, using the Ames two-stage light gas gun, to investigate the hypothesis that the Weston chondrule rims are the result of thermal and mechanical alteration upon impact into a low-density medium. Clusters of approximately 200-micron-sized silicate particles were fired into aerogel (density = 0.1 g cm-3) at velocities of 5.6, 4.7, and 2.2 km sec-1. Recovered grains show characteristics that range from fragmented projectile grains mixed with melted aerogel that nearly rim the grains to grains that have melted aerogel clumps mixed with partially melted projectile. These experimental results demonstrate that rim-like thermal and mechanical alteration of projectiles can result from a high-velocity encounter with a low-density target. Therefore, experiments using appropriately chosen projectile and target materials can provide a test of the hypothesis that chondrule rims common to Weston and possibly other ordinary chondrites were formed by such a process. PMID:11538105

  6. Chondrule thermal history from unequilibrated H chondrites: A transmission and analytical electron microscopy study

    NASA Astrophysics Data System (ADS)

    Ferraris, C.; Folco, L.; Mellini, M.

    2002-10-01

    Sixteen texturally different (porphyritic, barred, radial, cryptocrystalline) FeO-rich chondrules from the unequilibrated ordinary chondrites Brownfield, Frontier Mountain (FRO) 90003 and FRO 90032 were characterized by optical and scanning electron microscopy and then thoroughly studied by transmission and analytical electron microscopy. Nanotextural and nanochemical data indicate similar thermal evolution for chondrules of the same textural groups; minor, yet meaningful differences occur among the different groups. Olivine is the earliest phase formed and crystallizes between 1500 and 1400 deg C. Protoenstatite crystallizes at temperatures higher than 1350-1200 deg C; it later inverts to clinoenstatite in the 1250-1200 deg C range. Enstatite is surrounded by pigeonitic or (less frequently) augitic rims; the minimal crystallization temperature for the rims is 1000 C; high pigeonite later inverts to low pigeonite, between 935 and 845 deg C. The outer pigeonitic or augitic rims are constantly exsolved, producing sigmoidal augite or enstatite precipitates; sigmoidal precipitates record exsolution temperatures between 1000 and 640 deg C. Cooling rate (determined using the speedometer based upon ortho-clinoenstatite intergrowth) was in the order of 50-3000 deg C/h at the clinoenstatite-orthoenstatite transition temperature (close to 1250-1200 deg C), but decreased to 5-10 deg C/h or slower at the exsolution temperature (between 1000 and 650 deg C), thus revealing nonlinear cooling paths. Nanoscale observations indicate that the individual chondrules formed and cooled separately from 1500 deg down to at least 650 deg C. Accretion into chondritic parent body occurred at temperatures lower than 650 deg C.

  7. EH3 matrix mineralogy with major and trace element composition compared to chondrules

    NASA Astrophysics Data System (ADS)

    Lehner, S. W.; McDonough, W. F.; NéMeth, P.

    2014-12-01

    We investigated the matrix mineralogy in primitive EH3 chondrites Sahara 97072, ALH 84170, and LAR 06252 with transmission electron microscopy; measured the trace and major element compositions of Sahara 97072 matrix and ferromagnesian chondrules with laser-ablation, inductively coupled, plasma mass spectrometry (LA-ICPMS); and analyzed the bulk composition of Sahara 97072 with LA-ICPMS, solution ICPMS, and inductively coupled plasma atomic emission spectroscopy. The fine-grained matrix of EH3 chondrites is unlike that in other chondrite groups, consisting primarily of enstatite, cristobalite, troilite, and kamacite with a notable absence of olivine. Matrix and pyroxene-rich chondrule compositions differ from one another and are distinct from the bulk meteorite. Refractory lithophile elements are enriched by a factor of 1.5-3 in chondrules relative to matrix, whereas the matrix is enriched in moderately volatile elements. The compositional relation between the chondrules and matrix is reminiscent of the difference between EH3 pyroxene-rich chondrules and EH3 Si-rich, highly sulfidized chondrules. Similar refractory element ratios between the matrix and the pyroxene-rich chondrules suggest the fine-grained material primarily consists of the shattered, sulfidized remains of the formerly pyroxene-rich chondrules with the minor addition of metal clasts. The matrix, chondrule, and metal-sulfide nodule compositions are probably complementary, suggesting all the components of the EH3 chondrites came from the same nebular reservoir.

  8. Condensates from vapor made by impacts between metal-, silicate-rich bodies: Comparison with metal and chondrules in CB chondrites

    NASA Astrophysics Data System (ADS)

    Fedkin, Alexei V.; Grossman, Lawrence; Humayun, Munir; Simon, Steven B.; Campbell, Andrew J.

    2015-09-01

    The impact hypothesis for the origin of CB chondrites was tested by performing equilibrium condensation calculations in systems composed of vaporized mixtures of projectile and target materials. When one of the impacting bodies is composed of the metal from CR chondrites and the other is an H chondrite, good agreement can be found between calculated and observed compositions of unzoned metal grains in CB chondrites but the path of composition variation of the silicate condensate computed for the same conditions that reproduce the metal grain compositions does not pass through the measured compositions of barred olivine (BO) or cryptocrystalline (CC) chondrules in the CBs. The discrepancy between measured chondrule compositions and those of calculated silicates is not reduced when diogenite, eucrite or howardite compositions are substituted for H chondrite as the silicate-rich impacting body. If, however, a CR chondrite body is differentiated into core, a relatively CaO-, Al2O3-poor mantle and a CaO-, Al2O3-rich crust, and later accretes significant amounts of water, a collision between it and an identical body can produce the necessary chemical conditions for condensation of CB chondrules. If the resulting impact plume is spatially heterogeneous in its proportions of crust and mantle components, the composition paths calculated for silicate condensates at the same Ptot, Ni/H and Si/H ratios and water abundance that produce good matches to the unzoned metal grain compositions pass through the fields of BO and CC chondrules, especially if high-temperature condensates are fractionated in the case of the CCs. While equilibrium evaporation of an alloy containing solar proportions of siderophiles into a dense impact plume is an equally plausible hypothesis for explaining the compositions of the unzoned metal grains, equilibrium evaporation can explain CB chondrule compositions only if an implausibly large number of starting compositions is postulated. Kinetic models applied to co-condensing metal grains and silicate droplets in a region of the plume with very similar composition, but with high cooling rate and sharply declining Ptot during condensation, produce very good matches to the zoning profiles of Ir, Ni, Co and Cr concentrations and Fe and Ni isotopic compositions observed in the zoned metal grains in CB chondrites but produce very large positive δ56Fe in the cogenetic silicate, which are not found in the chondrules.

  9. Chondrule Rims in Murchison, Cathodoluminescence Evidence for In Situ Formation by Aqueous Alteration

    NASA Astrophysics Data System (ADS)

    Sears, D. W. G.; Jie, Lu; Benoit, P. H.

    1992-07-01

    The fine-grained rims on ordinary and carbonaceous chondrite chondrules are often regarded as accretionary, mainly because they are often volatile-rich (King and King, 1981). However, Sears et al. (1991) recently argued that some chondrule rims in CM chondrites may be the result of aqueous alteration. The rims, like many features in primitive chondrites, stand out especially clearly in cathodoluminescence (CL) imagery due to the distinctive bright red CL of their abundant fine-grained forsterite. Chondrules similarly stand out well in CL images. Group A chondrules show the strong red CL of Fe-free olivine, sometimes associated with the bright yellow CL of anorthite- normative mesostases, while group B chondrules containing Fe-rich olivines and quartz-normative mesostases do not produce CL (Sears et al., 1992). Using a CL mosaic, we measured chondrule and rim diameters for every chondrule in a 17x10 mm section of Murchison. 38% of the chondrules were group A, compared with 46% in the Semarkona (LL3.0) and 61% in the Dhajala (H3.8) ordinary chondrites. While both group A and group B chondrules have rims, those on group A chondrules are significantly thicker than those on group B chondrules, the rim-to-diameter ratios being 0.2-0.5 for group A chondrules and 0.1-0.2 for group B chondrules (Fig. 1). There are two reasonable explanations for the relationship between rim thickness and chondrule group. Either (1) the composition of chondrule mainly determines the thickness of the rim, e.g., the rims were produced by the aqueous alteration of the host chondrule, or (2) the two chondrule groups were formed in different environments, say a very dusty locale favoring thick rims versus a less favorable relatively dust-free location. We note that (a) both types of chondrule coexist in the same rock, (b) CL textures at the rim/matrix are sharp while at the rim/chondrule interface they are irregular (see Fig. 7d,e in Sears et al., 1991), (c) all faces on the objects in Murchison have rims of some sort, including the fracture faces of chondrule fragments, (d) the redistribution of volatiles will have accompanied aqueous alteration, and (e) mesostases of calcic plagioclase composition are more susceptible to hydrolysis than the more SiO2-rich glasses. We therefore suggest that the evidence favors the idea that these rims formed by in situ aqueous alteration. We suspect that most of this alteration predated the complex multistage, multienvironment brecciation process (Metzler et al., 1992). We speculate that some of the coarse-grained rims observed in higher petrologic type meteorites (e.g., Rubin, 1984) were produced by metamorphism of these fine- grained rims. King E. A. and King E. A. (1982) Icarus 48, 460-472. Metzler K. Bischoff A. and Stoffler D. (1992) Geochim. Cosmochim. Acta (in press). Rubin A. E. (1984) Coarse-grained chondrule rims in type 3 chondrites. Geochim. Cosmochim. Acta 48, 1779-1789. Sears D. W. G., Batchelor D. J., Lu J., Keck B. D. (1991) Proc. NIPR Symp. Antarct. Meteor., No. 4, 319-343. Sears D. W. G., Lu J., Benoit P. H., DeHart J. M. and Lofgren G. E. (1992) Nature (in press). Figure 1, which in the hard copy appears here, shows chondrule rim thickness to diameter ratio for 70 chondrules in Murchison. "Group A" and "Group B" refers to the compositional chondrule groups (Sears et al., 1992).

  10. Chondrules and the Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Hewins, R. H.; Jones, Rhian; Scott, Ed

    2011-03-01

    Part I. Introduction: 1. Chondrules and the protoplanetary disk: An overview R. H. Hewins; Part. II. Chonrules, Ca-Al-Rich Inclusions and Protoplanetary Disks: 2. Astronomical observations of phenomena in protostellar disks L. Hartmann; 3. Overview of models of the solar nebula: potential chondrule-forming environments P. Cassen; 4. Large scale processes in the solar nebula A. P. Boss; 5. Turbulence, chondrules and planetisimals J. N. Cuzzi, A. R. Dobrovolskis and R. C. Hogan; 6. Chondrule formation: energetics and length scales J. T. Wasson; 7. Unresolved issues in the formation of chondrules and chondrites J. A. Wood; 8. Thermal processing in the solar nebula: constraints from refractory inclusions A. M. Davis and G. J. MacPherson; 9. Formation times of chondrules and Ca-Al-Rich inclusions: constraints from short-lived radionuclides T. D. Swindle, A. M. Davis, C. M. Hohenberg, G. J. MacPherson and L. E. Nyquist; 10. Formation of chondrules and chondrites in the protoplanetary nebula E. R. D. Scott, S. G. Love and A. N. Krot; Part III. Chondrule precursors and multiple melting: 11. Origin of refractory precursor components of chondrules K. Misawa and N. Nakamura; 12. Mass-independent isotopic effects in chondrites: the role of chemical processes M. H. Thiemens; 13. Agglomeratic chondrules: implications for the nature of chondrule precursors and formation by incomplete melting M. K. Weisberg and M. Prinz; 14. Constraints on chondrule precursors from experimental Data H. C. Connolly Jr. and R. H. Hewins; 15. Nature of matrix in unequilibrated chondrites and its possible relationship to chondrules A. J. Brearly; 16. Constraints on chondrite agglomeration from fine-grained chondrule Rims K. Metzler and A. Bischoff; 17. Relict grains in chondrules: evidence for chondrule recycling R. H. Jones; 18. Multiple heating of chondrules A. E. Rubin and A. N. Krot; 19. Microchondrule-bearing chondrule rims: constraints on chondrule formation A. N. Krot and A. E. Rubin; Part IV. Heating, Cooling and Volatiles: 20. A dynamic crystallization model for chondrule melts G. E. Lofgren; 21. Peak temperatures of flash-melted chondrules R. H. Hewins and H. C. Connolly Jr.; 22. Congruent melting kinetics: constraints on chondrule formation J. P. Greenwood and P. C. Hess; 23. Sodium and sulfur in chondrules: heating time and cooling curves Y. Yu, R. H. Hewins and B. Zanda; 24. Open-system behaviour during chondrule formation D. W. G. Sears, S. Huang and P. H. Benoit; 25. Recycling and volatile loss in chondrule formation C. M. O'D. Alexander; 26. Chemical fractionations of chondrites: signatures of events before chondrule formation J. N. Grossmann; Part V. Models of Chondrule Formation: 27. A concise guide to chondrule formation models A. P. Boss; 28. Models for multiple heating mechanisms L. L. Hood and D. A. Kring; 29. Chondrule formation in the accretional shock T. V. Ruzmaikina and W. H. Ip; 30. The protostellar jet model of chondrule formation K. Liffman and M. Brown; 31. Chondrule formation in lightning discharges: status of theory and experiments M. Horanyi and S. Robertson; 32. Chondrules and their associates in ordinary chondrites: a planetary connection? R. Hutchinson; 33. Collision of icy and slightly differentiated bodies as an origin for unequilibriated ordinary chondrites M. Kitamura and A. Tsuchiyama; 34. A chondrule-forming scenario involving molten planetisimals I. S. Sanders.

  11. Deformation and thermal histories of chondrules in the Chainpur (LL3. 4) chondrite

    SciTech Connect

    Ruzicka, A. )

    1990-06-01

    The results of optical and TEM studies of chondrules in the Chainpur (LL3.4) chondrite are presented. Results were obtained, using a microprobe, from quantitative microchemical analyses for Mg, Fe, Si, and Ca for the chondrule olivine and pyroxene, showing that chondrules in the Chainpur chondrite experienced varied degrees of annealing and deformation. It is suggested that Chainpur may be an agglomerate of a breccia that experienced little overall deformation or heating during and after the final accumulation and compaction of its constituents. 75 refs.

  12. Thermoluminescence and compositional zoning in the mesostasis of a Semarkona group A1 chondrule and new insights into the chondrule-forming process

    NASA Astrophysics Data System (ADS)

    Matsunami, S.; Ninagawa, K.; Nishimura, S.; Kubono, N.; Yamamoto, I.; Kohata, M.; Wada, T.; Yamashita, Y.; Lu, J.; Sears, D. W. G.; Nishimura, H.

    1993-05-01

    A large, group A1, porphyritic olivine chondrule in the Semarkona chondrite with induced thermoluminescence (TL) and compositional zoning in its mesostasis has been discovered. The chondrule has Ca-rich and Fe-poor olivine and its mesostasis is highly anorthite-normative. The chondrule shows an intense induced TL peak at about 300 C with a half-width of about 180 C. The induced TL in the 40-440 C range increases monotonically by a factor of about 6 from center to rim, while SiO2, Na2O, and MnO increase by factors of about 1.1, about 3.6, and about 6, respectively. The spectrum of the induced TL over the 200-350 C range and the Mn-TL correlation suggest Mn-activated plagioclase is an important constituent of the refractory mesostases in group A1 chondrules. The zoning may reflect fractional crystallization, Soret diffusion, transport of volatiles into the chondrule by aqueous alteration, a zoned precursor, reduction of precursor dust aggregate, or recondensation of volatiles lost during chondrule formation.

  13. Mass transfer of Fe during the serpentinization of olivine by SiO2 rich fluid at 300°C, 500 bars: Perspectives from mineral dissolution/precipitation rates and Fe isotope systematics

    NASA Astrophysics Data System (ADS)

    Syverson, D. D.; Tutolo, B. M.; Borrok, D. M.; Seyfried, W. E., Jr.

    2014-12-01

    High temperature (~300°C) hydrothermal alteration of peridotites can produce an alteration assemblage abundant in Fe-bearing serpentine and magnetite without the presence of brucite. This is particularly so in systems with SiO2-rich fluids derived from the hydration of orthopyroxene in basaltic intrusions and gabbros [1]. Few experimental studies have investigated the effects of aSiO2(aq) on the rate of olivine serpentinization and none that have examined the Fe isotopic composition of olivine hydrolysis products. Thus, this study addresses these problems by using flexible gold cell hydrothermal equipment to react olivine (Fo90) and talc with a NaCl-bearing fluid at 300 °C and 500 bars for ~90 days; providing time-series solution chemistry data coupled with Fe isotope, magnetic susceptibility, and Mössbauer measurements of reactant olivine and the serpentinization product. Talc is used to elevate the aSiO2(aq)above the serpentine-brucite buffer, effectively preventing brucite formation and allowing only the formation of Fe-bearing serpentine and magnetite from olivine alteration. Initial time series solution chemistry data indicate that the net rate of the serpentinization of olivine and talc dissolution is such that the experimental system is poised between the serpentine-brucite and serpentine-talc stability fields, with little H2 generated by the oxidation of Fe2+ upon formation of Fe-serpentine and magnetite. However, as the talc Si-source becomes effectively titrated, the continued hydration of olivine decreases the aSiO2(aq) towards the serpentine-brucite stability field concurrent with an increasing rate of H2 generation. This chemical transition likely reflects an enhanced rate of magnetite formation upon a decrease in the relative stability of Fe-serpentine. Fe isotope data indicate a slight enrichment trend in δ56Fe versus Fe3+/ΣFe of the altered mineral phases, magnetite > Fe-serpentine > olivine, although the observed inter-mineral fractionations are small, <0.1 ‰. These experimental data are consistent with observations of natural Fe isotope data derived from hydrothermally altered peridotites [2] while providing requisite quantitative constraints to understand better their origin and evolution. [1] Bach et al., 2006 (GRL) [2] Craddock et al., 2014 (EPSL)

  14. Chondrule transport in protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Goldberg, Aaron Z.; Owen, James E.; Jacquet, Emmanuel

    2015-10-01

    Chondrule formation remains one of the most elusive early Solar system events. Here, we take the novel approach of employing numerical simulations to investigate chondrule origin beyond purely cosmochemical methods. We model the transport of generically produced chondrules and dust in a 1D viscous protoplanetary disc model in order to constrain the chondrule formation events. For a single formation event we are able to match analytical predictions of the memory they retain of each other (complementarity), finding that a large mass accretion rate (≳10-7 M⊙ yr-1) allows for delays on the order of the disc's viscous time-scale between chondrule formation and chondrite accretion. Further, we find older discs to be severely diminished of chondrules, with accretion rates ≲10-9 M⊙ yr-1 for nominal parameters. We then characterize the distribution of chondrule origins in both space and time, as functions of disc parameters and chondrule formation rates, in runs with continuous chondrule formation and both static and evolving discs. Our data suggest that these can account for the observed diversity between distinct chondrite classes, if some diversity in accretion time is allowed for.

  15. Experimental investigation of the nebular formation of chondrule rims and the formation of chondrite parent bodies

    NASA Astrophysics Data System (ADS)

    Beitz, E.; Blum, J.; Mathieu, R.; Pack, A.; Hezel, D. C.

    2013-09-01

    We developed an experimental setup to test the hypothesis that accretionary rims around chondrules formed in the solar nebula by accretion of dust on the surfaces of hot chondrules. Our experimental method allows us to form dust rims around chondrule analogs while levitated in an inert-gas flow. We used micrometer-sized powdered San Carlos olivine to accrete individual dust particles onto the chondrule analogs at room temperature (20 C) and at 1100 C. The resulting dust rims were analyzed by means of two different techniques: non-destructive micro computer tomography, and scanning electron microscopy. Both methods give very similar results for the dust rim structure and a mean dust rim porosity of 60% for the hot coated samples, demonstrating that both methods are equally well suited for sample analysis. The chondrule analog's bulk composition has no measurable impact on the accretion efficiency of the dust. We measured the chemical composition of chondrule analog and dust rim to check whether elemental exchange between the two components occurred. Such a reaction zone was not found; thus, we can experimentally confirm the sharp border between chondrules and dust rims described in the literature. We adopted a simple model to derive the degree of post-accretionary compaction for different carbonaceous chondrites. Moreover, we measured the rim porosity of a fragment of Murchison meteorite, analyzed it with micro-CT and found rim porosities with this technique that are comparable to those described in the literature.

  16. The formation and alteration of the Renazzo-like carbonaceous chondrites III: Toward understanding the genesis of ferromagnesian chondrules

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Connolly, Harold C.; Lauretta, Dante S.; Zega, Thomas J.; Davidson, Jemma; Domanik, Kenneth J.

    2015-01-01

    To better understand the formation conditions of ferromagnesian chondrules from the Renazzo-like carbonaceous (CR) chondrites, a systematic study of 210 chondrules from 15 CR chondrites was conducted. The texture and composition of silicate and opaque minerals from each observed FeO-rich (type II) chondrule, and a representative number of FeO-poor (type I) chondrules, were studied to build a substantial and self-consistent data set. The average abundances and standard deviations of Cr2O3 in FeO-rich olivine phenocrysts are consistent with previous work that the CR chondrites are among the least thermally altered samples from the early solar system. Type II chondrules from the CR chondrites formed under highly variable conditions (e.g., precursor composition, redox conditions, cooling rate), with each chondrule recording a distinct igneous history. The opaque minerals within type II chondrules are consistent with formation during chondrule melting and cooling, starting as S- and Ni-rich liquids at 988-1350 °C, then cooling to form monosulfide solid solution (mss) that crystallized around olivine/pyroxene phenocrysts. During cooling, Fe,Ni-metal crystallized from the S- and Ni-rich liquid, and upon further cooling mss decomposed into pentlandite and pyrrhotite, with pentlandite exsolving from mss at 400-600 °C. The composition, texture, and inferred formation temperature of pentlandite within chondrules studied here is inconsistent with formation via aqueous alteration. However, some opaque minerals (Fe,Ni-metal versus magnetite and panethite) present in type II chondrules are a proxy for the degree of whole-rock aqueous alteration. The texture and composition of sulfide-bearing opaque minerals in Graves Nunataks 06100 and Grosvenor Mountains 03116 suggest that they are the most thermally altered CR chondrites.

  17. A Parent Magma for the Nakhla Martian Meteorite: Reconciliation of Estimates from 1-Bar Experiments, Magmatic Inclusions in Olivine, and Magmatic Inclusions in Augite

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.; Goodrich, Cyrena Anne

    2001-01-01

    The composition of the parent magma for the Nakhla (martian) meteorite has been estimated from mineral-melt partitioning and from magmatic inclusions in olivine and in augite. These independent lines of evidence have converged on small range of likely compositions. Additional information is contained in the original extended abstract.

  18. Origin of plagioclase-olivine inclusions in carbonaceous chondrites

    SciTech Connect

    Sheng, Y.J.; Hutcheon, I.D.; Wasserburg, G.J. )

    1991-02-01

    Plagioclase-Olivine Inclusions (POIs) are an abundant group of chondrule-like objects with igneous textures found in carbonaceous chondrites. POIs consist of plagioclase, olivine, pyroxene, and spinel, and cover a wide range of compositions between Type C Ca-Al-rich Inclusions (CAIs) and ferromagnesian chondrules. POIs are distinguished from CAIs by the absence of melilite, lack of refractory siderophile-rich opaque assemblages, more sodic plagioclase, and abundance of olivine and aluminousenstatite. Rare accessory minerals including armalcolite, zirconolite, rutile, and sapphirine are found in several POIs. The petrographic and chemical properties of POIs indicate that they are not condensates or evaporative residues but formed by melting or partial melting of pre-existing solids. Seven of fourteen POIs contain isotopically fractionated Mg, and despite their textures these POIs are not isotopically homogeneous. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to formation of POIs - including condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting - are common to most CAIs and chondrules. We present a scenario for the formulation of these objects and conclude that the homogeneity of the final assemblage - CAI, POI, or chondrule - is primarily a reflection of the thermal history rather than the nature of precursor materials.

  19. Producing chondrules by recycling and volatile loss

    NASA Technical Reports Server (NTRS)

    Alexander, C. M. O.

    1994-01-01

    Interelement correlations observed in bulk chondrule INAA data, particularly between the refractory lithophiles, have led to the now generally accepted conclusion that the chondrule precursors were nebular condensates. However, it has been recently suggested that random sampling of fragments from a previous generation of chondrules could reproduce much of the observed range of bulk chondrule composition.

  20. Genetic relationship between Na-rich chondrules and Ca,Al-rich inclusions? - Formation of Na-rich chondrules by melting of refractory and volatile precursors in the solar nebula

    NASA Astrophysics Data System (ADS)

    Ebert, Samuel; Bischoff, Addi

    2016-03-01

    Al-rich objects (Ca,Al-rich inclusions (CAIs), Al-rich chondrules, Al-rich fragments) occur in all chondrite classes. These objects can be centimeter-sized in CV3 carbonaceous chondrites, but they are generally much smaller in other chondrite groups and classes. Within the ordinary chondrites, most Al-rich objects are chondrules that vary from Ca- to Na-rich. Here, we have investigated the mineralogy and major element chemistry of 32 Na-rich chondrules and 3 Na-rich fragments from 15 different chondrites. Most objects (chondrules and chondrule fragments) are from ordinary chondrites (petrologic types 3.2-3.8), but two of the chondrules are from two CO3 chondrites, and three of the chondrules are from one Rumuruti (R)-chondrite. We found that these Na-rich objects have bulk Na2O-concentrations between 4.3 and 15.2 wt%. Texturally, they typically consist of euhedral to subhedral (often skeletal) mafic minerals (olivine and pyroxenes) embedded within a nepheline-normative, glassy mesostasis, which is brownish in transmitted light. In addition, some chondrules contain euhedral to subhedral spinel. Bulk chondrule compositions show group II, group III, and ultrarefractory rare earth element (REE) patterns similar to those found in CAIs. These results clearly demonstrate that the Na-rich chondrules must have been formed by melting of precursors containing an (ultra-)refractory element-rich component and Na-rich constituents. The Na-rich chondrules showed Sm and Eu anomalies, indicating that they must have formed at low oxygen fugacities. Based on the chemical composition of the Na-rich objects, we can rule out that they were formed as a result of planetary formation due to metasomatic processes or processes related to collisions between molten planetesimals.

  1. Iodine-xenon, chemical, and petrographie studies of Semarkona chondrules: Evidence for the timing of aqueous alteration

    USGS Publications Warehouse

    Swindle, T.D.; Grossman, J.N.; Olinger, C.T.; Garrison, D.H.

    1991-01-01

    We have performed INAA, petrographie, and noble gas analyses on seventeen chondrules from the Semarkona meteorite (LL3.0) primarily to study the relationship of the I-Xe system to other measured properties. We observe a range of ???10 Ma in apparent I-Xe ages. The three latest apparent ages fall in a cluster, suggesting the possibility of a common event. The initial 129I/127I ratio (R0) is apparently related to chondrule type and/or mineralogy, with nonporphyritic and pyroxene-rich chondrules showing evidence for lower R0'S (later apparent I-Xe ages) than porphyritic and olivine-rich chondrules. In addition, chondrules with sulfides on or near the surface have lower R0S than other chondrules. The 129Xe/132Xe ratio in the trapped Xe component anticorrelates with R0, consistent with evolution of a chronometer in a closed system or in multiple similar systems. On the basis of these correlations, we conclude that the variations in R0 represent variations in ages, and that later event(s), possibly aqueous alteration, preferentially affected chondrules with nonporphyritic textures and/or sulfide-rich exteriors about 10 Ma after the formation of the chondrules. ?? 1991.

  2. Iodine-xenon, chemical, and petrographic studies of Semarkona chondrules - Evidence for the timing of aqueous alteration

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.; Grossman, J. N.; Olinger, C. T.; Garrison, D. H.

    1991-01-01

    The relationship of the I-Xe system of the Semarkona meteorite to other measured properties is investigated via INAA, petrographic, and noble-gas analyses on 17 chondrules from the meteorite. A range of not less than 10 Ma in apparent I-Xe ages is observed. The three latest apparent ages fall in a cluster, suggesting the possibility of a common event. It is argued that the initial I-129/I-127 ratio (R0) is related to chondrule type and/or mineralogy, with nonporphyritic and pyroxene-rich chondrules showing evidence for lower R0s than porphyritic and olivine-rich chondrules. Chondrules with sulfides on or near the surface have lower R0s than other chondrules. The He-129/Xe-132 ratio in the trapped Xe component anticorrelates with R0, consistent with the evolution of a chronometer in a closed system or in multiple systems. It is concluded that the variations in R0 represent variations in ages, and that later events, possibly aqueous alteration, preferentially affected chondrules with nonporphyritic textures and/or sulfide-rich exteriors about 10 Ma after the formation of the chondrules.

  3. Thermal histories of CO3 chondrites - Application of olivine diffusion modelling to parent body metamorphism

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.; Rubie, David C.

    1991-01-01

    The petrologic sequence observed in the CO3 chondrite group has been suggested to be the result of thermal metamorphism on a parent body. A model developed to examine the possibility that chondrule and matrix olivines equilibrated in situ, during parent body metamorphism is presented. The model considers Fe-Mg interdiffusion between chondrule and matrix olivines. Zoning profiles comparable to those observed in chondrule olivines from partially equilibrated members of the series are reproduced successfully. Metamorphism of CO3 chondrites on a parent body is therefore a viable model for the observed equilibration. Results indicate that peak metamorphic temperatures experienced by the CO3 chondrites were around 500 C, and that the range of peak temperatures between unequilibrated and equilibrated subtypes was relatively narrow, around 100 C.

  4. Turbulence, Chondrules, and Planetesimals

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey; Hogan, Robert C.; Dobrovolskis, Anthony R.; Paque, Julie M.

    1998-01-01

    It has been shown both numerically and experimentally that 3-D turbulence concentrates aerodynamically size-selected particles by orders of magnitude. In a previous review chapter, in "Chondrules and the protoplanetary disk" we illustrated the initial predictions of Turbulent Concentration (TC) as applied to the solar nebula. We predicted the particle size which will be most effectively concentrated by turbulence; it is the particle which has a gas drag stopping time equal to the overturn time of the smallest (Kolmogorov scale) eddy. The primary uncertainty is the level of nebula turbulence, or Reynolds number Re, which can be expressed in terms of the standard nebula eddy viscosity parameter alpha = Re(nu)(sub m)/cH, where nu(sub m) is molecular viscosity, c is sound speed, and H is vertical scale height. Several studies, and observed lifetimes of circumstellar disks, have suggested that the level of nebula turbulence can be described by alpha = 10(exp -2) - 10(exp -4). There is some recent concern about how energy is provided to maintain this turbulence, but the issue remains open. We adopt a canonical minimum mass nebula with a range of alpha > 0. We originally showed that chondrule-sized particles are selected for concentration in the terrestrial planet region if alpha = 10(exp -3) - 10(exp -4). In addition, Paque and Cuzzi found that the size distribution of chondrules is an excellent match for theoretical predictions. One then asks by what concentration factor C these particles can be concentrated; our early numerical results indicated an increase of C with alpha, and were supported by simple scaling arguments, but the extrapolation range was quite large and the predictions (C 10(exp 5) - 10(exp 6) not unlikely) uncertain. The work presented here, which makes use of our recent demonstration that the particle density field is a multifractal with flow-independent properties provides a far more secure ground for such predictions. We also indicate how fine-grained dust rims on chondrules might enter into constraining the situation.

  5. Chondrules in CK carbonaceous chondrites and thermal history of the CV-CK parent body

    NASA Astrophysics Data System (ADS)

    Chaumard, NoëL.; Devouard, Bertrand

    2016-01-01

    CK chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6. It is commonly reported than ~15 vol% of CK4-6 samples are composed of chondrules. The modal abundance of chondrules estimated here for 18 CK3-6 (including five CK3s) ranges from zero (totally recrystallized) to 50.5%. Although almost all chemically re-equilibrated with the host matrix, we recognized in CK3s and Tanezrouft (Tnz) 057 (CK4) up to 85% of chondrules as former type I chondrules. Mean diameters of chondrules range from 0.22 to 1.05 mm for Karoonda (CK4) and Tnz 057 (CK4), respectively. Up to ~60% of chondrules in CK3-4 are surrounded by igneous rims (from ~20 μm to 2 mm width). Zoned olivines were found in unequilibrated chondrules from DaG 431 (CK3-an), NWA 4724 (CK3.8), NWA 4423 (CK3.9), and Tnz 057 (CK4). We modeled Fe/Mg interdiffusion profiles measured in zoned olivines to evaluate the peak metamorphic temperatures and time scales of the CK parent body metamorphism, and proposed a two-stage diffusion process in order to account for the position of inflection points situated within chondrules. Time scales inferred from Fe/Mg interdiffusion in olivine from unequilibrated chondrules are on the order of tens to a hundred thousand years (from 50 to 70,000 years for peak metamorphic temperatures of 1140 and 920 K, respectively). These durations are longer than what is commonly accepted for shock metamorphism and shorter than what is required for nuclide decay. Using the concept of a continuous CV-CK metamorphic series, which is reinforced by this study, we estimated peak metamorphic temperatures <850 K for CV, 850-920 K for CK3, and 920-1140 K for CK4-6 chondrites considering a duration of 70,000 years.

  6. Chondrules in CK carbonaceous chondrites and thermal history of the CV-CK parent body

    NASA Astrophysics Data System (ADS)

    Chaumard, NoëL.; Devouard, Bertrand

    2016-03-01

    CK chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6. It is commonly reported than ~15 vol% of CK4-6 samples are composed of chondrules. The modal abundance of chondrules estimated here for 18 CK3-6 (including five CK3s) ranges from zero (totally recrystallized) to 50.5%. Although almost all chemically re-equilibrated with the host matrix, we recognized in CK3s and Tanezrouft (Tnz) 057 (CK4) up to 85% of chondrules as former type I chondrules. Mean diameters of chondrules range from 0.22 to 1.05 mm for Karoonda (CK4) and Tnz 057 (CK4), respectively. Up to ~60% of chondrules in CK3-4 are surrounded by igneous rims (from ~20 μm to 2 mm width). Zoned olivines were found in unequilibrated chondrules from DaG 431 (CK3-an), NWA 4724 (CK3.8), NWA 4423 (CK3.9), and Tnz 057 (CK4). We modeled Fe/Mg interdiffusion profiles measured in zoned olivines to evaluate the peak metamorphic temperatures and time scales of the CK parent body metamorphism, and proposed a two-stage diffusion process in order to account for the position of inflection points situated within chondrules. Time scales inferred from Fe/Mg interdiffusion in olivine from unequilibrated chondrules are on the order of tens to a hundred thousand years (from 50 to 70,000 years for peak metamorphic temperatures of 1140 and 920 K, respectively). These durations are longer than what is commonly accepted for shock metamorphism and shorter than what is required for nuclide decay. Using the concept of a continuous CV-CK metamorphic series, which is reinforced by this study, we estimated peak metamorphic temperatures <850 K for CV, 850-920 K for CK3, and 920-1140 K for CK4-6 chondrites considering a duration of 70,000 years.

  7. Chondrules as Natural Analogs for Metal Segregation: Analyses from 3D Synchrotron Imaging

    NASA Astrophysics Data System (ADS)

    Rushmer, T. A.; Clark, S. M.; Parkinson, D.

    2013-12-01

    Chondrules from the Bjurböle meteorite have been imaged by x-ray tomography to develop 3D visualization in order to use the chondrules as starting material in experimental deformation experiments aimed at unravelling the evolution of planetesimal-sized bodies. The Bjurböle chondrite is an olivine-hypersthene bearing meteorite and classified as an L/LL4. It fell in 1899, March 12 at 10:30 pm. Bjurböle has been used in several previous studies as it is abundant and has a range of chondrule sizes. Chrondrules themselves allow for the study of the early solar system and were formed ~2-3 My after the CAIs. However, we are using the chondrules as small metal-silicate natural analogs for metal-silicate deformation experiments. The critical first step is to characterize them. We have collected 3D textural data from 14 chondrules by synchrotron-based high resolution hard x-ray microtomography imaging. A series of two-dimensional images is collected as the sample is rotated, and tomographic reconstruction yields the full 3D representation of the sample. Virtual slices through the 3D object in any arbitrary direction can be visualized, or the full data set can be visualized by volume rendering. More importantly, automated image filtering and segmentation allows the extraction of boundaries between the various phases. The volumes, shapes, and distributions of each phase, and the connectivity between them, can then be quantitatively analysed. The imaging data show that the Bjurböle chondrules fall into two main groups. Those with abundant quenched glass and those bearing crystals of olivine and pyroxene, with minor glass. The metal and sulfide mainly line the outside of the chondrules as has been previously described, but the crystal-bearing chondrules also contain centrally located and widely distributed metal and sulfide. We are using these data to prepare the chondrules for experimental deformation studies. Figure 1 shows Bjurböle chondrule 8 (BB8). Image analyses has focused on distribution of FeNi (red) and FeS (gold). Metal and sulfide are concentrated on the outer edges but finely distributed internally. Scale is ~ 1 mm. Figure 1: FeNi and FeS distribution in BB 8.

  8. Strain Measurements of Chondrules and Refraction Inclusion in Allende

    NASA Technical Reports Server (NTRS)

    Tait, Alastair W.; Fisher, Kent R.; Simon, Justin I.

    2013-01-01

    This study uses traditional strain measurement techniques, combined with X-ray computerized tomography (CT), to evaluate petrographic evidence in the Allende CV3 chondrite for preferred orientation and to measure strain in three dimensions. The existence of petrofabrics and lineations was first observed in carbonaceous meteorites in the 1960's. Yet, fifty years later only a few studies have reported that meteorites record such features. Impacts are often cited as the mechanism for this feature, although plastic deformation from overburden and nebular imbrication have also been proposed. Previous work conducted on the Leoville CV3 and the Parnallee LL3 chondrites, exhibited a minimum uniaxial shortening of 33% and 21%, respectively. Petrofabrics in Allende CV3 have been looked at before; previous workers using Electron Back Scatter Diffraction (EBSD) found a major-axis alignment of olivine inside dark inclusions and an "augen"-like preferred orientation of olivine grains around more competent chondrules

  9. Evidence in CO3.0 Chondrules for a drift in the O Isotopic Composition of the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Wasson, John T.; Rubin, Alan E.; Yurimoto, Hisayoshi

    2006-01-01

    Several recent studies have shown that materials such as magnetite that formed in asteroids tend to have higher Delta O-17 (=delta O-17 -0.52 delta O-18) values than those recorded in unaltered chondrules. Other recent studies have shown that, in sets of chondrules from carbonaceous chondrites, Delta O-17 tends to increase as the FeO contents of the silicates increase. We report a comparison of the O isotopic composition of olivine phenocrysts in low-FeO (Fal5) type II porphyritic chondrules in the highly primitive C03.0 chondrite Yamato-81020. In agreement with a similar study of chondrules in C03.0 ALH A77307 by Jones et al., Delta O-17 tends to increase with increasing FeO. We find that Delta O-17 values are resolved (but only marginally) between the two sets of olivine phenocrysts. In two of the high-FeO chondrules, the difference between Delta O-17 of the late-formed, high-FeO phenocryst olivine and those in the low-FeO cores of relict grains is well-resolved (although one of the relicts is interpreted to be a partly melted amoeboid olivine inclusion by Yurimoto and Wasson). It appears that, during much of the chondrule-forming period, there was a small upward drift in the Delta O-17 of nebular solids and that relict cores preserve the record of a different (and earlier) nebular environment.

  10. The effect of Na vapor on the Na content of chondrules

    NASA Technical Reports Server (NTRS)

    Lewis, R. Dean; Lofgren, Gary E.; Franzen, Hugo F.; Windom, Kenneth E.

    1993-01-01

    Chondrules contain higher concentrations of volatiles (Na) than expected for melt droplets in the solar nebula. Recent studies have proposed that chondrules may have formed under non-canonical nebular conditions such as in particle/gas-rich clumps. Such chondrule formation areas may have contained significant Na vapor. To test the hypothesis of whether a Na-rich vapor would minimize Na volatilization reaction rates in a chondrule analog and maintain the Na value of the melt, experiments were designed where a Na-rich vapor could be maintained around the sample. A starting material with a melting point lower that typical chondrules was required to keep the logistics of working with Na volatilization from NaCl within the realm of feasibility. The Knippa basalt, a MgO-rich alkali olivine basalt with a melting temperature of 1325 +/- 5 C and a Na2O content of 3.05 wt%, was used as the chondrule analog. Experiments were conducted in a 1 atm, gas-mixing furnace with the fO2 controlled by a CO/CO2 gas mixture and fixed at the I-W buffer curve. To determine the extent of Na loss from the sample, initial experiments were conducted at high temperatures (1300 C - 1350 C) for duration of up to 72 h without a Na-rich vapor present. Almost all (up to 98%) Na was volatilized in runs of 72 h. Subsequent trials were conducted at 1330 C for 16 h in the presence of a Na-rich vapor, supplied by a NaCl-filled crucible placed in the bottom of the furnace. Succeeding Knudsen cell weight-loss mass-spectrometry analysis of NaCl determined the P(sub Na) for these experimental conditions to be in the 10(exp -6) atm range. This value is considered high for nebula conditions but is still plausible for non-canonical environments. In these trials the Na2O content of the glass was maintained or in some cases increased; Na2O values ranged from 2.62% wt to 4.37% wt. The Na content of chondrules may be controlled by the Na vapor pressure in the chondrule formation region. Most heating events capable of producing chondrules are sufficient to volatile Na. Sodium volatilization reaction rates will be reduced to varying degrees from melt droplets, depending on the magnitude of the P(sub Na) generated. A combination of Na vapor during, and Na diffusion back into chondrules after, formation could maintain and/or enrich Na concentrations in chondrules.

  11. The effect of NA vapor on the NA content of chondrules

    NASA Astrophysics Data System (ADS)

    Lewis, R. Dean; Lofgren, Gary E.; Franzen, Hugo F.; Windom, Kenneth E.

    1993-12-01

    Chondrules contain higher concentrations of volatiles (Na) than expected for melt droplets in the solar nebula. Recent studies have proposed that chondrules may have formed under non-canonical nebular conditions such as in particle/gas-rich clumps. Such chondrule formation areas may have contained significant Na vapor. To test the hypothesis of whether a Na-rich vapor would minimize Na volatilization reaction rates in a chondrule analog and maintain the Na value of the melt, experiments were designed where a Na-rich vapor could be maintained around the sample. A starting material with a melting point lower that typical chondrules was required to keep the logistics of working with Na volatilization from NaCl within the realm of feasibility. The Knippa basalt, a MgO-rich alkali olivine basalt with a melting temperature of 1325 +/- 5 C and a Na2O content of 3.05 wt%, was used as the chondrule analog. Experiments were conducted in a 1 atm, gas-mixing furnace with the fO2 controlled by a CO/CO2 gas mixture and fixed at the I-W buffer curve. To determine the extent of Na loss from the sample, initial experiments were conducted at high temperatures (1300 C - 1350 C) for duration of up to 72 h without a Na-rich vapor present. Almost all (up to 98%) Na was volatilized in runs of 72 h. Subsequent trials were conducted at 1330 C for 16 h in the presence of a Na-rich vapor, supplied by a NaCl-filled crucible placed in the bottom of the furnace. Succeeding Knudsen cell weight-loss mass-spectrometry analysis of NaCl determined the PNa for these experimental conditions to be in the 10-6 atm range. This value is considered high for nebula conditions but is still plausible for non-canonical environments. In these trials the Na2O content of the glass was maintained or in some cases increased; Na2O values ranged from 2.62% wt to 4.37% wt. The Na content of chondrules may be controlled by the Na vapor pressure in the chondrule formation region. Most heating events capable of producing chondrules are sufficient to volatile Na. Sodium volatilization reaction rates will be reduced to varying degrees from melt droplets, depending on the magnitude of the PNa generated. A combination of Na vapor during, and Na diffusion back into chondrules after, formation could maintain and/or enrich Na concentrations in chondrules.

  12. Conference on Chondrules and Their Origins

    NASA Technical Reports Server (NTRS)

    Hrametz, K.

    1983-01-01

    Chondrule parent materials, chondrule formation, and post-formational history are addressed. Contributions involving mineralogy petrology, geochemistry, geochronology, isotopic measurements, physical measurements, experimental studies, and theoretical studies are included.

  13. Constraints on chondrule agglomeration from fine-grained chondrule rims

    NASA Technical Reports Server (NTRS)

    Metzler, K.; Bischoff, A.

    1994-01-01

    Fine-grained rims around chondrules, Ca,Al-rich inclusions, and other coarse-grained components occur in most types of unequilibrated chondrites, most prominently in carbonaceous chondrites of the CM group. Based on mineralogical and petrographic investigations, it was suggested that rim structures in unequilibrated ordinary chondrites could have formed in the solar nebula by accretion of dust on the surfaces of the chondrules. Dust mantles in CM chondrites seem to have formed by accretion of dust on the surfaces of chondrules and other components during their passage through dust-rich regions in the solar nebula. Concentric mantles with compositionally different layers prove the existence of various distinct dust reservoirs in the vicinity of the accreting parent body. Despite mineralogical and chemical differences, fine-grained rims from other chondrite groups principally show striking similarities to dust mantle textures in CM chondrite. This implies that the formation of dust mantles was a cosmically significant event like the chondrule formation itself. Dust mantles seem to have formed chronologically between chondrule-producing transient heating events and the agglomeration of chondritic parent bodies. For this reason the investigation of dust mantle structures may help to answer the question of how a dusty solar nebula was transformed into a planetary system.

  14. An Evaluation of Quantitative Methods of Determining the Degree of Melting Experienced by a Chondrule

    NASA Technical Reports Server (NTRS)

    Nettles, J. W.; Lofgren, G. E.; Carlson, W. D.; McSween, H. Y., Jr.

    2004-01-01

    Many workers have considered the degree to which partial melting occurred in chondrules they have studied, and this has led to attempts to find reliable methods of determining the degree of melting. At least two quantitative methods have been used in the literature: a convolution index (CVI), which is a ratio of the perimeter of the chondrule as seen in thin section divided by the perimeter of a circle with the same area as the chondrule, and nominal grain size (NGS), which is the inverse square root of the number density of olivines and pyroxenes in a chondrule (again, as seen in thin section). We have evaluated both nominal grain size and convolution index as melting indicators. Nominal grain size was measured on the results of a set of dynamic crystallization experiments previously described, where aliquots of LEW97008(L3.4) were heated to peak temperatures of 1250, 1350, 1370, and 1450 C, representing varying degrees of partial melting of the starting material. Nominal grain size numbers should correlate with peak temperature (and therefore degree of partial melting) if it is a good melting indicator. The convolution index is not directly testable with these experiments because the experiments do not actually create chondrules (and therefore they have no outline on which to measure a CVI). Thus we had no means to directly test how well the CVI predicted different degrees of melting. Therefore, we discuss the use of the CVI measurement and support the discussion with X-ray Computed Tomography (CT) data.

  15. MAGNESIUM ISOTOPE EVIDENCE FOR SINGLE STAGE FORMATION OF CB CHONDRULES BY COLLIDING PLANETESIMALS

    SciTech Connect

    Olsen, Mia B.; Schiller, Martin; Krot, Alexander N.; Bizzarro, Martin

    2013-10-10

    Chondrules are igneous spherical objects preserved in chondritic meteorites and believed to have formed during transient heating events in the solar protoplanetary disk. Chondrules present in the metal-rich CB chondrites show unusual chemical and petrologic features not observed in other chondrite groups, implying a markedly distinct formation mechanism. Here, we report high-precision Mg-isotope data for 10 skeletal olivine chondrules from the Hammadah al Hamra 237 (HH237) chondrite to probe the formation history of CB chondrules. The {sup 27}Al/{sup 24}Mg ratios of individual chondrules are positively correlated to their stable Mg-isotope composition (μ{sup 25}Mg), indicating that the correlated variability was imparted by a volatility-controlled process (evaporation/condensation). The mass-independent {sup 26}Mg composition (μ{sup 26}Mg*) of chondrules is consistent with single stage formation from an initially homogeneous magnesium reservoir if the observed μ{sup 25}Mg variability was generated by non-ideal Rayleigh-type evaporative fractionation characterized by a β value of 0.5142, in agreement with experimental work. The magnitude of the mass-dependent fractionation (∼300 ppm) is significantly lower than that suggested by the increase in {sup 27}Al/{sup 24}Mg values, indicating substantial suppression of isotopic fractionation during evaporative loss of Mg, possibly due to evaporation at high Mg partial pressure. Thus, the Mg-isotope data of skeletal chondrules from HH237 are consistent with their origin as melts produced in the impact-generated plume of colliding planetesimals. The inferred μ{sup 26}Mg* value of –3.87 ± 0.93 ppm for the CB parent body is significantly lower than the bulk solar system value of 4.5 ± 1.1 ppm inferred from CI chondrites, suggesting that CB chondrites accreted material comprising an early formed {sup 26}Al-free component.

  16. Chondrules born in plasma? Simulation of gas-grain interaction using plasma arcs with applications to chondrule and cosmic spherule formation

    NASA Astrophysics Data System (ADS)

    Morlok, A.; Sutton, Y. C.; Braithwaite, N. St. J.; Grady, Monica M.

    2012-12-01

    Abstract-We are investigating <span class="hlt">chondrule</span> formation by nebular shock waves, using hot plasma as an analog of the heated gas produced by a shock wave as it passes through the protoplanetary environment. Precursor material (mainly silicates, plus metal, and sulfide) was dropped through the plasma in a basic experimental set-up designed to simulate gas-grain collisions in an unconstrained spatial environment (i.e., no interaction with furnace walls during formation). These experiments were undertaken in air (at atmospheric pressure), to act as a "proof-of-principle"—could <span class="hlt">chondrules</span>, or <span class="hlt">chondrule</span>-analog objects (CAO), be formed by gas-grain interaction initiated by shock fronts? Our results showed that if accelerating material through a fixed plasma field is a valid simulation of a supersonic shock wave traveling through a cloud of gas and dust, then CAO certainly could be formed by this process. Melting of and mixing between starting materials occurred, indicating temperatures of at least 1266 °C (the <span class="hlt">olivine</span>-feldspar eutectic). The production of CAO with mixed mineralogy from monomineralic starting materials also shows that collisions between particles are an important mechanism within the <span class="hlt">chondrule</span> formation process, such that dust aggregates are not necessarily required as <span class="hlt">chondrule</span> precursors. Not surprisingly, there were significant differences between the synthetic CAO and natural <span class="hlt">chondrules</span>, presumably mainly because of the oxidizing conditions of the experiment. Results also show similarity to features of micrometeorites like cosmic spherules, particularly the dendritic pattern of iron oxide crystallites produced on micrometeorites by oxidation during atmospheric entry and the formation of vesicles by evaporation of sulfides.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS...51..520M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS...51..520M"><span id="translatedtitle">Correlations and zoning patterns of phosphorus and chromium in <span class="hlt">olivine</span> from H chondrites and the LL chondrite Semarkona</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McCanta, M. C.; Beckett, J. R.; Stolper, E. M.</p> <p>2016-03-01</p> <p>Phosphorus zoning is observed in <span class="hlt">olivines</span> in high-FeO (type IIA) <span class="hlt">chondrules</span> in H chondrites over the entire range of petrologic grades: H3.1-H6. Features in P concentrations such as oscillatory and sector zoning, and high P cores are present in <span class="hlt">olivines</span> that are otherwise unzoned in the divalent cations. Aluminum concentrations are low and not significantly associated with P zoning in <span class="hlt">chondrule</span> <span class="hlt">olivines</span>. In highly unequilibrated H chondrites, phosphorus zoning is generally positively correlated with Cr. Atomic Cr:P in <span class="hlt">olivine</span> is roughly 1:1 (3:1 for one zone in one <span class="hlt">olivine</span> in RC 075), consistent with Cr3+ charge-balancing P5+ substituting for Si4+. Normal igneous zonation involving the dominant chrome species Cr2+ was observed only in the LL3.0 chondrite Semarkona. In more equilibrated chondrites (H3.5-H3.8), Cr spatially correlated with P is occasionally observed but it is diffuse relative to the P zones. In H4-H6 chondrites, P-correlated Cr is absent. One signature of higher metamorphic grades (≥H3.8) is the presence of near matrix <span class="hlt">olivines</span> that are devoid of P oscillatory zoning. The restriction to relatively high metamorphic grade and to grains near the <span class="hlt">chondrule</span>-matrix interface suggests that this is a response to metasomatic processes. We also observed P-enriched halos near the <span class="hlt">chondrule</span>-matrix interface in H3.3-H3.8 chondrites, likely reflecting the loss of P and Ca from mesostasis and precipitation of Ca phosphate near the <span class="hlt">chondrule</span> surface. These halos are absent in equilibrated chondrites due to coarsening of the phosphate and in unequilibrated chondrites due to low degrees of metasomatism. <span class="hlt">Olivines</span> in type IA <span class="hlt">chondrules</span> show none of the P-zoning ubiquitous in type IIA <span class="hlt">chondrules</span> or terrestrial igneous <span class="hlt">olivines</span>, likely reflecting sequestration of P in reduced form within metallic alloys and sulfides during melting of type IA <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS..tmp..283M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS..tmp..283M"><span id="translatedtitle">Correlations and zoning patterns of phosphorus and chromium in <span class="hlt">olivine</span> from H chondrites and the LL chondrite Semarkona</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McCanta, M. C.; Beckett, J. R.; Stolper, E. M.</p> <p>2016-02-01</p> <p>Phosphorus zoning is observed in <span class="hlt">olivines</span> in high-FeO (type IIA) <span class="hlt">chondrules</span> in H chondrites over the entire range of petrologic grades: H3.1-H6. Features in P concentrations such as oscillatory and sector zoning, and high P cores are present in <span class="hlt">olivines</span> that are otherwise unzoned in the divalent cations. Aluminum concentrations are low and not significantly associated with P zoning in <span class="hlt">chondrule</span> <span class="hlt">olivines</span>. In highly unequilibrated H chondrites, phosphorus zoning is generally positively correlated with Cr. Atomic Cr:P in <span class="hlt">olivine</span> is roughly 1:1 (3:1 for one zone in one <span class="hlt">olivine</span> in RC 075), consistent with Cr3+ charge-balancing P5+ substituting for Si4+. Normal igneous zonation involving the dominant chrome species Cr2+ was observed only in the LL3.0 chondrite Semarkona. In more equilibrated chondrites (H3.5-H3.8), Cr spatially correlated with P is occasionally observed but it is diffuse relative to the P zones. In H4-H6 chondrites, P-correlated Cr is absent. One signature of higher metamorphic grades (≥H3.8) is the presence of near matrix <span class="hlt">olivines</span> that are devoid of P oscillatory zoning. The restriction to relatively high metamorphic grade and to grains near the <span class="hlt">chondrule</span>-matrix interface suggests that this is a response to metasomatic processes. We also observed P-enriched halos near the <span class="hlt">chondrule</span>-matrix interface in H3.3-H3.8 chondrites, likely reflecting the loss of P and Ca from mesostasis and precipitation of Ca phosphate near the <span class="hlt">chondrule</span> surface. These halos are absent in equilibrated chondrites due to coarsening of the phosphate and in unequilibrated chondrites due to low degrees of metasomatism. <span class="hlt">Olivines</span> in type IA <span class="hlt">chondrules</span> show none of the P-zoning ubiquitous in type IIA <span class="hlt">chondrules</span> or terrestrial igneous <span class="hlt">olivines</span>, likely reflecting sequestration of P in reduced form within metallic alloys and sulfides during melting of type IA <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010584','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010584"><span id="translatedtitle">Impact-Induced <span class="hlt">Chondrule</span> Deformation and Aqueous Alteration of CM2 Murchison</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hanna, R. D.; Zolensky, M.; Ketcham, R. A.; Behr, W. M.; Martinez, J. E.</p> <p>2014-01-01</p> <p>Deformed <span class="hlt">chondrules</span> in CM2 Murchison have been found to define a prominent foliation [1,2] and lineation [3] in 3D using X-ray computed tomography (XCT). It has been hypothesized that <span class="hlt">chondrules</span> in foliated chondrites deform by "squeezing" into surrounding pore space [4,5], a process that also likely removes primary porosity [6]. However, shock stage classification based on <span class="hlt">olivine</span> extinction in Murchison is consistently low (S1-S2) [4-5,7] implying that significant intracrystalline plastic deformation of <span class="hlt">olivine</span> has not occurred. One objective of our study is therefore to determine the microstructural mechanisms and phases that are accommodating the impact stress and resulting in relative displacements within the <span class="hlt">chondrules</span>. Another question regarding impact deformation in Murchison is whether it facilitated aqueous alteration as has been proposed for the CMs which generally show a positive correlation between degree of alteration and petrofabric strength [7,2]. As pointed out by [2], CM Murchison represents a unique counterpoint to this correlation: it has a strong petrofabric but a relatively low degree of aqueous alteration. However, Murchison may not represent an inconsistency to the proposed causal relationship between impact and alteration, if it can be established that the incipient aqueous alteration post-dated <span class="hlt">chondrule</span> deformation. Methods: Two thin sections from Murchison sample USNM 5487 were cut approximately perpendicular to the foliation and parallel to lineation determined by XCT [1,3] and one section was additionally polished for EBSD. Using a combination of optical petrography, SEM, EDS, and EBSD several <span class="hlt">chondrules</span> were characterized in detail to: determine phases, find microstructures indicative of strain, document the geometric relationships between grain-scale microstructures and the foliation and lineation direction, and look for textural relationships of alteration minerals (tochilinite and Mg-Fe serpentine) that indicate timing of their formation relative to deformation event(s). Preliminary Results: Deformed <span class="hlt">chondrules</span> are dominated by forsterite and clinoenstatite with lesser amounts of Fe-Mg serpentine, sulfides, and low calcium pyroxene. <span class="hlt">Olivine</span> grains are commonly fractured but generally show sharp optical extinction. The pyroxene, in contrast, is not only fractured but also often displays undulose extinction. In addition, the clinoenstatite is frequently twinned but it is unclear whether the twins are the result of mechanical deformation or inversion from protoenstatite [8]. EBSD work is currently ongoing to determine if areas of higher crystallographic strain can be imaged and mapped, and to determine the pyroxene twin orientations. In regards to alteration, we have found evidence for post-deformation formation of tochilinite and Mg-Fe serpentine indicating that aqueous alteration has indeed post-dated the deformation of the <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900038005&hterms=oxygen+isotopes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Doxygen%2Bisotopes','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900038005&hterms=oxygen+isotopes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Doxygen%2Bisotopes"><span id="translatedtitle">Oxygen isotopes in <span class="hlt">chondrules</span> and coarse-grained <span class="hlt">chondrule</span> rims from the Allende meteorite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.; Wasson, John T.; Clayton, Robert N.; Mayeda, Toshiko K.</p> <p>1990-01-01</p> <p>The relationship between the porphyritic <span class="hlt">chondrules</span> and coase-grained <span class="hlt">chondrule</span> rims of the Allende CV chondrite are examined. The oxygen isotopic compositions of seven <span class="hlt">chondrule</span>-rim pairs and a large rimless refractory <span class="hlt">chondrule</span> from Allende are determined. The results suggest that, to account for the O-isotopic compositions of the CV <span class="hlt">chondrules</span> and rims, three solid precursor components are required: a high-temperature, refractory-, alkali, and (O-16)-rich component; a low-temperature, FeO-rich, refractory, and (O-16)-poor component, and an additional component to explain the composition of BO <span class="hlt">chondrules</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992Metic..27R.228G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992Metic..27R.228G"><span id="translatedtitle">Not All Refractory Spherules in CM2S are <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Greenwood, R. C.</p> <p>1992-07-01</p> <p>Refractory spherules in CM2 meteorites are small, <300 micrometers in diameter, inclusions composed predominantly of spinel, with accessory hibonite and perovskite (Macdougall 1981). On the basis of their <span class="hlt">chondrule</span>-like morphology, and the inward-radiating habit of hibonite in some inclusions, it has been suggested that refractory spherules formed from liquid droplets (Macdougall 1981; MacPherson et al. 1983). Since many spherules are composed purely of spinel, Macdougall (1981) estimated that their 1-atm melting temperature might have been as high as 2135 degrees C. Melt temperatures in excess of 1550 degrees C were estimated by MacPherson et al. (1983) for the spinel-hibonite spherule BB1. Refractory spherules are a minor component of the Ca-Al rich inclusions (CAIs) found in CM2s. Of 345 CAIs located in the CM2 Cold Bokkeveld only 4 are refractory spherules (study in collaboration with M. Lee, University of Essex). Textural evidence from Cold Bokkeveld demonstrates that CAIs in CM2s are highly fragmented and must have been derived by disruption of larger objects (Greenwood et al. 1991). That this is also the case for refractory spherules is clearly demonstrated by MSP1, an anhedral, spinel-bearing inclusion (300 mmicrometer longest dimension) located in situ in Murchison (CM2). It comprises a rounded core (110 micrometers in diameter) of Fe-free spinel (V2O3 0.5wt%) surrounded by a rim of pyroxene (15-25 micrometers thick), in turn enclosed by a zone of <span class="hlt">olivine</span> (Fo 99.7) and Mg-rich phyllosilicate. The spinel core contains 15% void space (estimated). The pyroxene rim is zoned outwards from fassaite to diopside. Blocky crystals of <span class="hlt">olivine</span> <20 micrometers in diameter form a discontinuous rim to pyroxene and occur as isolated grains enclosed by Mg-phyllosilicate. The inclusion has an irregular outline and a sharp contact with surrounding matrix, indicating that it is a fragment of a larger, now disrupted CAI. In CV3 meteorites refractory spinel-rich spherules, similar to the Murchison example, occur within a number of different inclusion-types. Nodules, 5-300 micrometers in diameter, composed of spinel, melilite, perovskite, and pyroxene are common constituents of amoeboid <span class="hlt">olivine</span> aggregates (Hashimoto and Grossman 1987). Melilite is also present in some Murchison spherules (MacPherson et al. 1983), and prior to aqueous alteration may have been an important constituent in many of these objects. Spherical clumps of spinel crystals, termed "framboids" by El Goresy et al. (1979) are common constituents of type B2 coarse-grained CAIs (Wark and Lovering 1982). One B2 CAI in Vigarano contains a 160-micrometer-diameter framboid with a 10-20-micrometer-thick rim of spinel enclosing a touching framework of rounded grains (5-15 micrometers in diameter). Melilite, present in the bulk inclusion, forms an outer rind to the framboid 5-10 micrometers thick and may be contiguous with crystals (angstrom k(sub)16.5) interstitial to spinel within the framboid. Individually rimmed spinel nodules, up to 300 micrometers in diameter, are also an important component of "fluffy" type A inclusions (MacPherson and Grossman 1984). The structure of the Murchison inclusion MSP1 indicates that at least some CM2 refractory spherules were components of larger inclusions. In CV3s, experimental evidence suggests that spinel spherules represent residual solid material that acquired a rounded form during partial melting (Wark and Lovering 1982). The comparison made between <span class="hlt">chondrules</span> and spherules may therefore be misleading and results in erroneously high estimates of the temperatures experienced by these objects. El Goresy A., Nagel K., and Ramdohr P. (1979) Proc. Lunar Planet. Sci. Conf. 10th, 833-850. Greenwood R.C., Hutchison R., and Cressey G. (1991) Meteoritics (abstract) 26, 340. Hashimoto A. and Grossman L. (1987) Geochim. Cosmochim. Acta 51, 1685-1704. Macdougall J.D. (1981) Geophys. Res. Lett. 8, 966-969. MacPherson G.J. and Grossman, L. (1984) Geochim. Cosmochim. Acta 48, 29-46. MacPherson G.J., <span class="hlt">Bar</span>-Matthews M., Tanaka T., Olsen E., and Grossman L. (1983) Geochim. Cosmochim. Acta 47, 823-839. Wark D.A. and Lovering J.F. (1982) Geochim. Cosmochim. Acta 46, 2581-2594.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22370080','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22370080"><span id="translatedtitle"><span class="hlt">Chondrule</span> destruction in nebular shocks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jacquet, Emmanuel; Thompson, Christopher</p> <p>2014-12-10</p> <p><span class="hlt">Chondrules</span> are millimeter-sized silicate spherules ubiquitous in primitive meteorites, but whose origin remains mysterious. One of the main proposed mechanisms for producing them is melting of solids in shock waves in the gaseous protoplanetary disk. However, evidence is mounting that <span class="hlt">chondrule</span>-forming regions were enriched in solids well above solar abundances. Given the high velocities involved in shock models, destructive collisions would be expected between differently sized grains after passage of the shock front as a result of differential drag. We investigate the probability and outcome of collisions of particles behind a one-dimensional shock using analytic methods as well as a full integration of the coupled mass, momentum, energy, and radiation equations. Destruction of protochondrules seems unavoidable for solid/gas ratios ε ≳ 0.1, and possibly even for solar abundances because of 'sandblasting' by finer dust. A flow with ε ≳ 10 requires much smaller shock velocities (∼2 versus 8 km s{sup –1}) in order to achieve <span class="hlt">chondrule</span>-melting temperatures, and radiation trapping allows slow cooling of the shocked fragments. Initial destruction would still be extensive; although re-assembly of millimeter-sized particles would naturally occur by grain sticking afterward, the compositional heterogeneity of <span class="hlt">chondrules</span> may be difficult to reproduce. We finally note that solids passing through small-scale bow shocks around few kilometer-sized planetesimals might experience partial melting and yet escape fragmentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040121339&hterms=magnetite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmagnetite','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040121339&hterms=magnetite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmagnetite"><span id="translatedtitle">Origin of magnetite in oxidized CV chondrites: in situ measurement of oxygen isotope compositions of Allende magnetite and <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Choi, B. G.; McKeegan, K. D.; Leshin, L. A.; Wasson, J. T.</p> <p>1997-01-01</p> <p>Magnetite in the oxidized CV chondrite Allende mainly occurs as spherical nodules in porphyritic-<span class="hlt">olivine</span> (PO) <span class="hlt">chondrules</span>, where it is associated with Ni-rich metal and/or sulfides. To help constrain the origin of the magnetite, we measured oxygen isotopic compositions of magnetite and coexisting <span class="hlt">olivine</span> grains in PO <span class="hlt">chondrules</span> of Allende by an in situ ion microprobe technique. Five magnetite nodules form a relatively tight cluster in oxygen isotopic composition with delta 18O values from -4.8 to -7.1% and delta 17O values from -2.9 to -6.3%. Seven coexisting <span class="hlt">olivine</span> grains have oxygen isotopic compositions from -0.9 to -6.3% in delta 18O and from -4.6 to -7.9% in delta 17O. The delta 17O values of the magnetite and coexisting <span class="hlt">olivine</span> do not overlap; they range from -0.4 to -2.6%, and from -4.0 to -5.7%, respectively. Thus, the magnetite is not in isotopic equilibrium with the <span class="hlt">olivine</span> in PO <span class="hlt">chondrules</span>, implying that it formed after the <span class="hlt">chondrule</span> formation. The delta 17O of the magnetite is somewhat more negative than estimates for the ambient solar nebula gas. We infer that the magnetite formed on the parent asteroid by oxidation of metal by H2O which had previously experienced minor O isotope exchange with fine-grained silicates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992Metic..27R.281R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992Metic..27R.281R"><span id="translatedtitle">Magnetite-Pentlandite <span class="hlt">Chondrules</span> in CK Chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rubin, A. E.</p> <p>1992-07-01</p> <p>Opaque-mineral-rich <span class="hlt">chondrules</span> are among the least common <span class="hlt">chondrule</span> types and have received scant attention since their discovery by Gustav Rose in 1864. This category includes <span class="hlt">chondrules</span> comprised principally of metallic Fe-Ni (Tschermak, 1885; Gooding and Keil, 1981) or chrome-spinel (Ramdohr, 1967; Krot et al., 1992). Here I report the occurrence of seven magnetite-pentlandite <span class="hlt">chondrules</span> in Karoonda (CK4), PCA82500 (CK4/5) and EET90007 (CK5). The <span class="hlt">chondrules</span> range in size from 225x255 micrometers to 440x570 micrometers and have ellipsoidal or spheroidal morphologies. All are concentrically layered: five of the <span class="hlt">chondrules</span> have 20-60-micrometer-thick magnetite rims surrounding pentlandite-rich cores or mantles; two of the <span class="hlt">chondrules</span> have thin pentlandite rims surrounding magnetite-rich cores and mantles. One <span class="hlt">chondrule</span> from Karoonda has four distinct alternating layers of magnetite and pentlandite. Accessory phases, which occur in one or more of the <span class="hlt">chondrules</span>, include pyrrhotite, chlorapatite, ilmenite, and chalcopyrite. The <span class="hlt">chondrules</span> have finely to coarsely granular textures; in the center of one <span class="hlt">chondrule</span> from PCA82500 there is a 25x100 micrometers subhedral crystal of pentlandite. All of the <span class="hlt">chondrules</span> appear to be recrystallized, presumably due to metamorphism of their host rocks. The magnetite-pentlandite <span class="hlt">chondrules</span> are very similar to the magnetite-pentlandite-rich nodules within mafic silicate <span class="hlt">chondrules</span> in CK chondrites. I examined four nodules that range in size from 58x64 micrometers to 400x670 micrometers and have ellipsoidal or spheroidal morphologies. All but one are concentrically layered; one nodule from a Karoonda <span class="hlt">chondrule</span> has four concentric layers of magnetite+-pentlandite. The nodules probably formed from immiscible sulfide-oxide droplets within their molten silicate <span class="hlt">chondrule</span> hosts during <span class="hlt">chondrule</span> formation. Upon cooling, magnetite and monosulfide solid solution (Mss) precipitated during cotectic crystallization; the Mss transformed into pentlandite after cooling below 610 degrees C. Dense immiscible liquid droplets tend to get expelled from the equators of their spinning molten spheroidal hosts if they do not happen to be located in the molten spheroids' centers where the centrifugal forces are minimal. This phenomenon also affected the four magnetite-pentlandite nodules: one nodule is near the margin and three are at the centers of their host silicate <span class="hlt">chondrules</span>. The similarities in size, shape, mineralogy, and texture between the magnetite-pentlandite <span class="hlt">chondrules</span> and nodules indicate that these <span class="hlt">chondrules</span> constitute the set of immiscible nodule droplets that were lost to their mafic silicate <span class="hlt">chondrule</span> hosts after melting. The occurrence of magnetite-pentlandite <span class="hlt">chondrules</span> and nodules has important implications for the timing of CK chondrite oxidation. If oxidation had occurred after agglomeration and transformed metallic Fe-Ni into magnetite, the large (factor of 2) increase in molar volume would have disrupted the nodules and <span class="hlt">chondrules</span> and destroyed the evidence for rhythmic layering. The intactness of the <span class="hlt">chondrules</span> and nodules implies that the oxidation of fine-grained metallic Fe-Ni into magnetite probably occurred before agglomeration, either during <span class="hlt">chondrule</span> formation in a region of high fo(sub)2 or within porous <span class="hlt">chondrule</span>-precursor dust clumps after nebular temperatures cooled below ~130 degrees C. Hence, the pervasive silicate darkening of CK chondrites (Kallemeyn et al., 1991; Rubin, 1992) was caused by the shock mobilization of magnetite and pentlandite, not metallic Fe-Ni and troilite as in shock-darkened ordinary chondrites. References: Gooding J.L. and Keil K. (1981) Meteoritics 16, 17- 43; Kallemeyn G.W., Rubin A.E. and Wasson J.T. (1991) Geochim. Cosmochim. Acta 55, 881-892; Krot A., Ivanova M.A. and Wasson J.T. (1992) Earth Planet. Sci. Lett., submitted; Ramdohr P. (1967) Geochim. Cosmochim. Acta 31, 1961-1967; Rubin A.E. (1992) Geochim. Cosmochim. Acta 56, 1705-1714; Tschermak G. (1885) Die Mikroskopische Beschaffenheit der Meteoriten. Schweizerbart'sche Verlagshandlung, Stuttgart.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeCoA..79...79R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeCoA..79...79R"><span id="translatedtitle">Amoeboid <span class="hlt">olivine</span> aggregates (AOAs) in the Efremovka, Leoville and Vigarano (CV3) chondrites: A record of condensate evolution in the solar nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruzicka, Alex; Floss, Christine; Hutson, Melinda</p> <p>2012-02-01</p> <p>Amoeboid <span class="hlt">olivine</span> aggregates (AOAs) in the Efremovka, Leoville, and Vigarano CV3 chondrites were studied using petrographic and microanalytical techniques to evaluate the origins of these inclusions and their relationships to other chondrite components. Our data support the idea that the inclusions formed by dust growth in the solar nebula as condensates and that they preserve a record of mineralogical and chemical evolution. Spinel-rich nodules and ribbons in AOAs often show Group II trace element patterns and formed either by fractional condensation or by condensation following partial vaporization. The dominant <span class="hlt">olivine</span> component in AOAs can be explained as a condensate produced in the same way, but with fractionation occurring at a lower temperature. Other spinel-rich material in AOAs appears to be a vaporization residue. Ca-rich pyroxene + anorthite patches in AOAs show chemical signatures similar to those observed for spinel- or melilite-bearing regions but with lower refractory element and higher Mg and Si contents, supporting the idea that the patches formed by reaction between CAI-like material and Mg-Si-rich gas. Different trace element patterns (Group II and non-Group II refractory) are sometimes found for Al-rich regions (Ca-pyroxene + anorthite, or melilite-bearing) in a given AOA, suggesting that AOAs agglomerated from materials that formed under different conditions and that they did not subsequently homogenize. AOAs appear to have originated in a system with near-canonical solar composition and a low pressure gas (˜10-6-10-4 <span class="hlt">bar</span>) over a range of temperatures (mainly ˜1200-1384 K) under somewhat non-equilibrium conditions. Relative to predicted equilibrium condensates, most AOAs show an apparent paucity of metal, possibly reflecting differential, density-dependent sorting between <span class="hlt">olivine</span> and metal grains during aggregate formation. Trace element data are consistent with a simple model involving melting and igneous fractionation of AOA-like <span class="hlt">olivine</span> to produce Type I <span class="hlt">chondrule</span> <span class="hlt">olivine</span>, but other data suggest that open-system melting of <span class="hlt">chondrules</span> occurred in a different gaseous environment than that which produced AOAs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5030R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5030R"><span id="translatedtitle">A Regolith Origin of ``Pre-Irradiation" of Murchison <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riebe, M.; Huber, L.; Wieler, R.; Metzler, K.; Maden, C.; Meier, M. M. M.; Busemann, H.</p> <p>2015-07-01</p> <p>Individual <span class="hlt">chondrules</span> from a lithic fragment in Murchison all have similar CRE ages whereas <span class="hlt">chondrules</span> from outside the fragment have variable ages, providing evidence that additional irradiation of <span class="hlt">chondrules</span> occurred in the parent body regolith.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS...51..116W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS...51..116W"><span id="translatedtitle">Petrology, mineralogy, and oxygen isotope compositions of aluminum-rich <span class="hlt">chondrules</span> from CV3 chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Ying; Hsu, Weibiao; Li, Xianhua; Li, Qiuli; Liu, Yu; Tang, Guoqiang</p> <p>2016-01-01</p> <p>Bulk major element composition, petrography, mineralogy, and oxygen isotope compositions of twenty Al-rich <span class="hlt">chondrules</span> (ARCs) from five CV3 chondrites (Northwest Africa [NWA] 989, NWA 2086, NWA 2140, NWA 2697, NWA 3118) and the Ningqiang carbonaceous chondrite were studied and compared with those of ferromagnesian <span class="hlt">chondrules</span> and refractory inclusions. Most ARCs are marginally Al-richer than ferromagnesian <span class="hlt">chondrules</span> with bulk Al2O3 of 10-15 wt%. ARCs are texturally similar to ferromagnesian <span class="hlt">chondrules</span>, composed primarily of <span class="hlt">olivine</span>, pyroxene, plagioclase, spinel, Al-rich glass, and metallic phases. Minerals in ARCs have intermediate compositions. Low-Ca pyroxene (Fs0.6-8.8Wo0.7-9.3) has much higher Al2O3 and TiO2 contents (up to 12.5 and 2.3 wt%, respectively) than that in ferromagnesian <span class="hlt">chondrules</span>. High-Ca pyroxene (Fs0.3-2.0Wo33-54) contains less Al2O3 and TiO2 than that in Ca,Al-rich inclusions (CAIs). Plagioclase (An77-99Ab1-23) is much more sodic than that in CAIs. Spinel is enriched in moderately volatile element Cr (up to 6.7 wt%) compared to that in CAIs. Al-rich enstatite coexists with anorthite and spinel in a glass-free <span class="hlt">chondrule</span>, implying that the formation of Al-enstatite was not due to kinetic reasons but is likely due to the high Al2O3/CaO ratio (7.4) of the bulk <span class="hlt">chondrule</span>. Three ARCs contain relict CAIs. Oxygen isotope compositions of ARCs are also intermediate between those of ferromagnesian <span class="hlt">chondrules</span> and CAIs. They vary from -39.4‰ to 13.9‰ in δ18O and yield a best fit line (slope = 0.88) close to the carbonaceous chondrite anhydrous mineral (CCAM) line. <span class="hlt">Chondrules</span> with 5-10 wt% bulk Al2O3 have a slightly more narrow range in δ18O (-32.5 to 5.9‰) along the CCAM line. Except for the ARCs with relict phases, however, most ARCs have oxygen isotope compositions (>-20‰ in δ18O) similar to those of typical ferromagnesian <span class="hlt">chondrules</span>. ARCs are genetically related to both ferromagnesian <span class="hlt">chondrules</span> and CAIs, but the relationship between ARCs and ferromagnesian <span class="hlt">chondrules</span> is closer. Most ARCs were formed during flash heating and rapid cooling processes like normal <span class="hlt">chondrules</span>, only from chemically evolved precursors. ARCs extremely enriched in Al and those with relict phases could have had a hybrid origin (Krot et al. 2002) which incorporated refractory inclusions as part of the precursors in addition to ferromagnesian materials. The occurrence of melilite in ARCs indicates that melilite-rich CAIs might be present in the precursor materials of ARCs. The absence of melilite in most ARCs is possibly due to high-temperature interactions between a <span class="hlt">chondrule</span> melt and the solar nebula.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19800060501&hterms=Vaca+Muerta&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DVaca%2BMuerta','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19800060501&hterms=Vaca+Muerta&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DVaca%2BMuerta"><span id="translatedtitle"><span class="hlt">Olivines</span> and <span class="hlt">olivine</span> coronas in mesosiderites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nehru, C. E.; Zucker, S. M.; Harlow, G. E.; Prinz, M.</p> <p>1980-01-01</p> <p>The paper presents a study of <span class="hlt">olivines</span> and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. <span class="hlt">Olivine</span> composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; <span class="hlt">olivine</span> occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified <span class="hlt">olivine</span> orthopyroxenites. Fine-grained coronas surround <span class="hlt">olivine</span>, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980GeCoA..44.1103N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980GeCoA..44.1103N"><span id="translatedtitle"><span class="hlt">Olivines</span> and <span class="hlt">olivine</span> coronas in mesosiderites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nehru, C. E.; Zucker, S.; Harlow, G. E.; Prinz, M.</p> <p>1980-08-01</p> <p>The paper presents a study of <span class="hlt">olivines</span> and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. <span class="hlt">Olivine</span> composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; <span class="hlt">olivine</span> occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified <span class="hlt">olivine</span> orthopyroxenites. Fine-grained coronas surround <span class="hlt">olivine</span>, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010059864','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010059864"><span id="translatedtitle">Stardust to Planetesimals: A <span class="hlt">Chondrule</span> Connection?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paque, Julie; Bunch, Ted</p> <p>1997-01-01</p> <p>The unique nature of <span class="hlt">chondrules</span> has been known for nearly two centuries. Modern techniques of analysis have shown that these millimeter sized silicate objects are among the oldest objects in our solar system. Researchers have devised textural and chemical classification systems for <span class="hlt">chondrules</span> in an effort to determine their origins. It is agreed that most <span class="hlt">chondrules</span> were molten at some point in their history, and experimental analogs suggest that the majority of <span class="hlt">chondrules</span> formed from temperatures below 1600 C at cooling rates in the range of hundreds of degrees per hour. Although interstellar grains are present in chondrite matrices, their contribution as precursors to <span class="hlt">chondrule</span> formation is unknown. Models for <span class="hlt">chondrule</span> formation focus on the pre-planetary solar nebula conditions, although planetary impact models have had proponents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930069284&hterms=metamorphism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmetamorphism','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930069284&hterms=metamorphism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmetamorphism"><span id="translatedtitle">Effect of metamorphism on isolated <span class="hlt">olivine</span> grains in CO3 chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jones, Rhian H.</p> <p>1993-01-01</p> <p>The presence of a metamorphic sequence in the CO3 chondrite group has been shown previously to result in changes in properties of <span class="hlt">chondrule</span> silicates. However, the role of isolated <span class="hlt">olivine</span> grains during metamorphism of these chondrites has not been addressed. Isolated <span class="hlt">olivine</span> grains in two metamorphosed CO3 chondrites, Lance and Isna, have been investigated in this study in order to assess the compositional properties of isolated <span class="hlt">olivine</span> grains that may be attributable to metamorphism. Compositional changes in isolated <span class="hlt">olivines</span> with increasing petrologic subtype are very similar to changes in <span class="hlt">chondrule</span> <span class="hlt">olivines</span> in the same chondrites. <span class="hlt">Olivine</span> compositions from all occurrences (<span class="hlt">chondrules</span>, isolated grains, and matrix) converge with increasing petrologic subtype. The degree of equilibration of minor elements is qualitatively related to the diffusion rate of each element in <span class="hlt">olivine</span>, suggesting that diffusion-controlled processes are the most important processes responsible for compositional changes within the metamorphic sequence. The data are consistent with metamorphism taking place in a closed system on the CO3 chondrite parent body. Fe-poor <span class="hlt">olivine</span> grains in metamorphosed chondrites are characterized by an Fe-rich rim, which is the result of diffusion of Fe into the grains from Fe-rich matrix. In some instances, 'complex', Fe-rich rims have been identified, which appear to have originated as igneous overgrowths and subsequently to have been overprinted by diffusion processes during metamorphism. Processes experienced by CO3 chondrites are more similar to those experienced by the ordinary chondrites than to those encountered by other carbonaceous chondrites, such as the CV3 group.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920044034&hterms=Spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSpinel','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920044034&hterms=Spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSpinel"><span id="translatedtitle">Spinel-bearing, Al-rich <span class="hlt">chondrules</span> in two chondrite finds from Roosevelt County, New Mexico - Indicators of nebular and parent body processes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mccoy, Timothy J.; Pun, Aurora; Keil, Klaus</p> <p>1991-01-01</p> <p>Two rare spinel-bearing Al-rich <span class="hlt">chondrules</span> are identified in chondrite finds from Roosevelt County, New Mexico-RC 071 (L4) and RC 072 (L5). These <span class="hlt">chondrules</span> have unusual mineralogies dominated by highly and asymmetrically zoned Al-Cr-rich spinels. Two alternatives exist to explain the origin of this zoning-fractional crystallization or metamorphism. Fractional crystallization formed the zoning of the trivalent cations and caused a localized depletion in chromites around the large Al-Cr-rich spinels. Diffusive exchange and partitioning of Fe and Mg between <span class="hlt">olivine</span> and spinel during parent-body metamorphism can explain the asymmetric zoning of these elements. The bulk compositions of the <span class="hlt">chondrules</span> suggest affinities with the Na-Al-Cr-rich <span class="hlt">chondrules</span>, as would be expected from the abundance of Al-Cr-rich spinels. The most important factors are the temperature to which the molten <span class="hlt">chondrule</span> was heated and the cooling rate during crystallization. These two <span class="hlt">chondrules</span> cooled rapidly from near the liquidus, as indicated by the zoning, occurrence and sizes of spinels, radiating <span class="hlt">chondrule</span> textures and localized chromite depletions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950012914&hterms=radiochemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dradiochemistry','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950012914&hterms=radiochemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dradiochemistry"><span id="translatedtitle">I-Xe studies of individual <span class="hlt">chondrules</span>: What can they tell us about <span class="hlt">chondrule</span> formation?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Swindle, T. D.; Hohenberg, C. M.</p> <p>1994-01-01</p> <p>In the past 14 years, I-Xe studies have been performed on nearly 100 individual <span class="hlt">chondrules</span> from five different meteorites. More than half the studied <span class="hlt">chondrules</span> come from the unequilibrated ordinary chondrites (UOC's) Chainpur, Semarkona, and Tieschitz. However, 'unequilibrated' does not necessarily mean 'unaltered,' and the I-Xe studies of <span class="hlt">chondrules</span> from UOC's have ultimately been interpreted in terms of postformation alteration. Two types of constraints on <span class="hlt">chondrule</span> formation are discussed: (1) the duration, location, and timing of postformation alteration (in solids over a 50-m.y. span); and (2) the ages of the earliest formed <span class="hlt">chondrules</span> (a few million years after the earliest solids).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009M%26PS...44.1797D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009M%26PS...44.1797D"><span id="translatedtitle">Cosmogenic and trapped noble gases in individual <span class="hlt">chondrules</span>: Clues to <span class="hlt">chondrule</span> formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, J. P.; Murty, S. V. S.</p> <p>2009-12-01</p> <p>We studied the elemental and isotopic abundances of noble gases (He, Ne, Ar in most cases, and Kr, Xe also in some cases) in individual <span class="hlt">chondrules</span> separated from six ordinary, two enstatite, and two carbonaceous chondrites. Most <span class="hlt">chondrules</span> show detectable amounts of trapped 20Ne and 36Ar, and the ratio (36Ar/20Ne)t (from ordinary and carbonaceous chondrites) suggests that HL and Q are the two major trapped components. A different trend between (36Ar/20Ne)t and trapped 36Ar is observed for <span class="hlt">chondrules</span> in enstatite chondrites indicating a different environment and/or mechanism for their formation compared to <span class="hlt">chondrules</span> in ordinary and carbonaceous chondrites. We found that a <span class="hlt">chondrule</span> from Dhajala chondrite (DH-11) shows the presence of solar-type noble gases, as suggested by the (36Ar/20Ne)t ratio, Ne-isotopic composition, and excess of 4He. Cosmic-ray exposure (CRE) ages of most <span class="hlt">chondrules</span> are similar to their host chondrites. A few <span class="hlt">chondrules</span> show higher CRE age compared to their host, suggesting that some <span class="hlt">chondrules</span> and/or precursors of <span class="hlt">chondrules</span> have received cosmic ray irradiation before accreting to their parent body. Among these <span class="hlt">chondrules</span>, DH-11 (with solar trapped gases) and a <span class="hlt">chondrule</span> from Murray chondrite (MRY-1) also have lower values of (21Ne/22Ne)c, indicative of SCR contribution. However, such evidences are sporadic and indicate that <span class="hlt">chondrule</span> formation event may have erased such excess irradiation records by solar wind and SCR in most <span class="hlt">chondrules</span>. These results support the nebular environment for <span class="hlt">chondrule</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850025542&hterms=sulfur+topical&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsulfur%2Btopical','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850025542&hterms=sulfur+topical&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsulfur%2Btopical"><span id="translatedtitle">Nebular volatile fractionations associated with <span class="hlt">chondrule</span> formation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kracher, A.</p> <p>1985-01-01</p> <p><span class="hlt">Chondrules</span> are ubiquitous constituents of primitive solar system matter, indicating that <span class="hlt">chondrule</span> formation was an important and widespread process in the early history of the solar system. If <span class="hlt">chondrules</span> formed from fine grained CI like precursors, some volatile fractionation must have accompanied <span class="hlt">chondrule</span> formation. This is not likely related to a separation of <span class="hlt">chondrules</span> from gas (and dust, fine enough to be coupled to gas) shortly after formation, a process required by most models of <span class="hlt">chondrule</span> formation. If <span class="hlt">chondrules</span> are continuously formed in and removed from a region of the solar nebula, the chemical environment in this region will change. Vaporization of solid increases both oxygen and sulfur in the gas relative to H. Depending on the oxygen/sulfur ratio, which may vary widely as a function of precursor composition and temperature, two cases can be distinguished: (1) sulfur requires reaction with solid to condense, and thus may become much more enriched than 0; (2) if a significant amount of silicate is vaporized together with sulfides and does not recondense, changes in H/O outweigh S enrichment. In combination, these two effects may be able to account for much of the chemical variation among various types of chondrites. Opaque, fine grained matrix in unequilibrated chondrites, which is thought to derive from dust, has indeed been found to have a volatile element abundance complementary to <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006mess.book..431L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006mess.book..431L"><span id="translatedtitle">Petrology and Origin of Ferromagnesian Silicate <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lauretta, D. S.; Nagahara, H.; Alexander, C. M. O'd.</p> <p></p> <p>Ferromagnesian silicate <span class="hlt">chondrules</span> are major components of most primitive meteorites. The shapes, textures, and mineral compositions of these <span class="hlt">chondrules</span> are consistent with crystallization of a molten droplet that was floating freely in space in the presence of a gas. The texture and mineralogy of a <span class="hlt">chondrule</span> reflects the nature and composition of its precursor material as well as its thermal history. There is an enduring debate about the degree to which <span class="hlt">chondrules</span> interacted with the ambient gas during formation. In particular, it is uncertain whether or not <span class="hlt">chondrules</span> experienced evaporation during heating and recondensation during cooling. The extent to which these processes took place in <span class="hlt">chondrule</span> melts varied as a function of the duration of heating as well as the environmental conditions such as pressure, temperature, composition, and size. Thus, locked in <span class="hlt">chondrule</span> bulk compositions, mineralogy, and textures are clues to the ambient conditions of the solar nebula and the nature of material processing in the inner solar system at the early stages of planet formation. Here we survey what is known about the properties of ferromagnesian <span class="hlt">chondrules</span> in primitive meteorites and use this information to place constraints on these important parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140000237','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140000237"><span id="translatedtitle">A Microanalytical (TEM) Study of Fine-grained <span class="hlt">Chondrule</span> Rims in NWA 5717</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bigolski, J. N.; Frank, D. R.; Zolensky, Michael E.; Weisberg, M. K.; Ebel, D. S.; Rahman, Z.</p> <p>2013-01-01</p> <p>Northwest Africa (NWA) 5717 is a highly primitive ordinary chondrite of petrologic type 3.05 with ubiquitous fine-grained <span class="hlt">chondrule</span> rims [1, 2]. Rims appear around approximately 60% of <span class="hlt">chondrules</span> and are comprised of micron-sized mineral and lithic fragments and microchondrules that are embdedded in an FeO-rich submicron groundmass that compositionally resembles fayalitic <span class="hlt">olivine</span>. Some rim clasts appear overprinted with FeO-rich material, suggesting secondary alteration that postdates rim formation. Here we present a microanalytical (TEM) study of the submicron component (i.e. the groundmass) of the rims in order to determine the crystal structures and compositions of their constituent phases and decipher the accretion and alteration history recorded in rims.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS..tmp..323R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS..tmp..323R"><span id="translatedtitle">Cosmic-ray exposure ages of <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roth, Antoine S. G.; Metzler, Knut; Baumgartner, Lukas P.; Leya, Ingo</p> <p>2016-05-01</p> <p>If <span class="hlt">chondrules</span> were exposed to cosmic rays prior to meteorite compaction, they should retain an excess of cosmogenic noble gases. Beyersdorf-Kuis et al. showed that such excesses can be detected provided that the chemical composition of each individual <span class="hlt">chondrule</span> is precisely known. However, their study was limited to a few samples as they had to be irradiated in a nuclear reactor for instrumental neutron activation analysis. We developed a novel analytical protocol that combines the measurements of He and Ne isotopic concentrations with a fast method to correct for differences in chemical composition using micro X-ray computed tomography. Our main idea is to combine noble gas, nuclear track, and petrography data for numerous <span class="hlt">chondrules</span> to understand the precompaction exposure history of the chondrite parent bodies. Here, we report our results for a total of 77 <span class="hlt">chondrules</span> and four matrix samples from NWA 8276 (L3.00), NWA 8007 (L3.2), and Bjurböle (L/LL4). All <span class="hlt">chondrules</span> from the same meteorite have within uncertainty identical 21Ne exposure ages, and all <span class="hlt">chondrules</span> from Bjurböle have within uncertainty identical 3He exposure ages. However, most <span class="hlt">chondrules</span> from NWA 8276 and a few from NWA 8007 show small but resolvable differences in 3He exposure age that we attribute to matrix contamination and/or gas loss. The finding that none of the <span class="hlt">chondrules</span> has noble gas excesses is consistent with the uniform track density found for each meteorite. We conclude that the studied <span class="hlt">chondrules</span> did not experience a precompaction exposure longer than a few Ma assuming present-day flux of galactic cosmic rays. A majority of <span class="hlt">chondrules</span> from L and LL chondrites thus rapidly accreted and/or was efficiently shielded from cosmic rays in the solar nebula.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V31A4718U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V31A4718U"><span id="translatedtitle">Experimental Constraints on Alkali Volatilization during <span class="hlt">Chondrule</span> Formation: Implications for Early Solar System Heterogeneity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ustunisik, G. K.; Ebel, D. S.; Nekvasil, H.</p> <p>2014-12-01</p> <p>The chemical variability of <span class="hlt">chondrule</span> volatile element contents provide a wealth of information on the processes that shaped the early solar system and its compositional heterogeneity. An essential observation is that <span class="hlt">chondrule</span> melts contain very low alkalies and other volatile elements (e.g., Cl). The reason for this depletion is the combined effects of cooling rates (10 to 1000K/h), the small size of <span class="hlt">chondrules</span>, and their high melting temperatures (~1700 to 2100 K) resulting in extensive loss of volatiles at canonical pressures (e.g., 10-4<span class="hlt">bar</span>). However, we observe some <span class="hlt">chondrules</span> with significant concentrations of volatiles (Na, Cl), that differ markedly from <span class="hlt">chondrules</span> dominated by refractory elements. Could such heterogeneity arise from loss of alkalis and Cl to a gas phase that itself later condenses, thereby yielding variations in volatile enrichments in <span class="hlt">chondrules</span>? Does Cl enhance volatility of the alkalis to varying extents? Experiments on Cl-bearing and Cl-free melts of equivalent composition for 10 min, 4 h, and 6 h reveal systematic effects of Cl on alkali volatility. Cl-bearing melts lose 48% of initial Na2O, 66% of K2O, 96% of Cl within the first 10 minutes of degassing. Then the amount of alkali loss decreases due to the absence of Cl. Cl-free melts loses only 15% of initial Na2O and 33% K2O. After 4 hours, melts lose 1/3 of initial Na2O and 1/2 of K2O. For both systems, Na2O is more compatible in the melt relative to K2O. Therefore, the vapor given off has a K/Na ratio higher than the melt through time in spite of the much higher initial Na abundance in the melt. Enhanced vaporization of alkalis from Cl-bearing melt suggests that Na and K evaporate more readily as volatile chlorides than as monatomic gases. Cl-free initial melts with normative plagioclase of An50Ab44Or6 evolved into slightly normal zoned ones (An49Ab50Or1) while Cl-bearing initial melts normative to albitic plagioclase (An46Ab50Or4) evolved to reverse zoned ones (An54Ab45Or1). The vapor phase over Cl-bearing <span class="hlt">chondrule</span> melts may have a bimodal character over time. The heteregeneous volatile contents of <span class="hlt">chondrules</span> may result from quenching of melt droplets at different stages of repeated heating, <span class="hlt">chondrule</span> fragment recycling, and recondensation of exsolved volatiles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060049107&hterms=Mineralogist&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DMineralogist','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060049107&hterms=Mineralogist&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DMineralogist"><span id="translatedtitle">Aluminian Low-Ca Pyroxene in a Ca-Al-rich <span class="hlt">Chondrule</span> from the Semarkona Meteorite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.</p> <p>2006-01-01</p> <p>A Ca-AI-rich <span class="hlt">chondrule</span> (labeled G7) from the Semarkona LL3.0 ordinary chondrite (OC) consists of 73 vol% glassy mesostasis, 22 vol% skeletal forsterite. 3 vol% fassaite (i.e., Al-Ti diopside), and 2 vol% Al-rich, low-Ca pyroxene. The latter phase, which contains up to 16.3 wt% A1203, is among the most AI-rich, low-Ca pyroxene grains ever reported. It is inferred that 20% of the tetrahedral sites and 13% of the octahedral sites in this grain are occupied by Al. Approximately parallel optical extinction implies that the Al-rich, low-Ca pyroxene grains are probably orthorhombic, consistent with literature data that show that A1203 stabilizes the orthoenstatite structure relative to protoenstatite at low pressure. The order of crystallization in the <span class="hlt">chondrule</span> was forsterite, AI-rich low-Ca pyroxene, and fassaite; the residual liquid vitrified during <span class="hlt">chondrule</span> quenching. Phase relationships indicate that, for a G7-composition liquid at equilibrium, spinel and anorthite should crystallize early and orthopyroxene should not crystallize at all. The presence of AI-rich orthopyroxene in G7 is due mainly to the kinetic failure of anorthite to crystallize; this failure was caused by quenching of the G7 precursor droplet. Aluminum preferentially enters the relatively large B tetrahedra of orthopyroxene; because only one tetrahedral size occurs in fassaite, this phase contains higher mean concentrations of Al2O3 than the Al-rich orthopyroxene (17.8 and 14.7 wt%, respectively). <span class="hlt">Chondrule</span> G7 may have formed by remelting an amoeboid <span class="hlt">olivine</span> inclusion that entered the OC region of the solar nebula during an episode of <span class="hlt">chondrule</span> formation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050165557','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050165557"><span id="translatedtitle">Genetic Relationships Between <span class="hlt">Chondrules</span>, Rims and Matrix</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huss, G. R.; Alexander, C. M. OD.; Palme, H.; Bland, P. A.; Wasson, J. T.</p> <p>2004-01-01</p> <p>The most primitive chondrites are composed of <span class="hlt">chondrules</span> and <span class="hlt">chondrule</span> fragments, various types of inclusions, discrete mineral grains, metal, sulfides, and fine-grained materials that occur as interchondrule matrix and as <span class="hlt">chondrule</span>/inclusion rims. Understanding how these components are related is essential for understanding how chondrites and their constituents formed and were processed in the solar nebula. For example, were the first generations of <span class="hlt">chondrules</span> formed by melting of matrix or matrix precursors? Did <span class="hlt">chondrule</span> formation result in appreciable transfer of <span class="hlt">chondrule</span> material into the matrix? Here, we consider three types of data: 1) compositional data for bulk chondrites and matrix, 2) mineralogical and textural information, and 3) the abundances and characteristics of presolar materials that reside in the matrix and rims. We use these data to evaluate the roles of evaporation and condensation, <span class="hlt">chondrule</span> formation, mixing of different nebular components, and secondary processing both in the nebula and on the parent bodies. Our goal is to identify the things that are reasonably well established and to point out the areas that need additional work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940007705&hterms=Enigma&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DEnigma','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940007705&hterms=Enigma&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DEnigma"><span id="translatedtitle">Flash melting of <span class="hlt">chondrule</span> precursors in excess of 1600 C. Series 1: Type 2 (B1) <span class="hlt">chondrule</span> composition experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Connolly, Harold C., Jr.; Hewins, Roger H.; Lofgren, Gary E.</p> <p>1993-01-01</p> <p>Several questions in <span class="hlt">chondrule</span> production remain an enigma despite years of experiments. What were the melting temperatures experienced by <span class="hlt">chondrules</span>? What were the physical characteristics of <span class="hlt">chondrule</span> precursors? How and why did volatile elements (i.e. Na) found within <span class="hlt">chondrules</span> survive the formation process? We present the initial results of a series of experiments designed to investigate the above questions by using flash melting to duplicate the melting stage of <span class="hlt">chondrule</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060049098&hterms=AGENTS+OXIDATION&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAGENTS%2BOXIDATION','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060049098&hterms=AGENTS+OXIDATION&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAGENTS%2BOXIDATION"><span id="translatedtitle">Relationships Among Intrinsic Properties of Ordinary Chondrites: Oxidation State, Bulk Chemistry, Oxygen-isotopic Composition, Petrologic Type, and <span class="hlt">Chondrule</span> Size</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.</p> <p>2006-01-01</p> <p>The properties of ordinary chondrites (OC) reflect both nebular and asteroidal processes. OC are modeled here as having acquired nebular water, probably contained within phyllosilicates, during agglomeration. This component had high Ai70 and acted like an oxidizing agent during thermal metamorphism. The nebular origin of this component is consistent with negative correlations in H, L, and LL chondrites between oxidation state (represented by <span class="hlt">olivine</span> Fa) and bulk concentration ratios of elements involved in the metal-silicate fractionation (e.g., NdSi, Ir/Si, Ir/Mn, Ir/Cr, Ir/Mg, Ni/Mg, As/Mg, Ga/Mg). LL chondrites acquired the greatest abundance of phyllosilicates with high (delta)O-17 among OC (and thus became the most oxidized group and the one with the heaviest O isotopes); H chondrites acquired the lowest abundance, becoming the most reduced OC group with the lightest O isotopes. <span class="hlt">Chondrule</span> precursors may have grown larger and more ferroan with time in each OC agglomeration zone. Nebular turbulence may have controlled the sizes of <span class="hlt">chondrule</span> precursors. H-chondrite <span class="hlt">chondrules</span> (which are the smallest among OC) formed from the smallest precursors. In each OC region, low-FeO <span class="hlt">chondrules</span> formed before high-FeO <span class="hlt">chondrules</span> during repeated episodes of <span class="hlt">chondrule</span> formation. During thermal metamorphism, phyllosilicates were dehydrated; the liberated water oxidized metallic Fe-Ni. This caused correlated changes with petrologic type including decreases in the modal abundance of metal, increases in <span class="hlt">olivine</span> Fa and low-Ca pyroxene Fs, increases in the <span class="hlt">olivine</span>/pyroxene ratio, and increases in the kamacite Co and Ni contents. As water (with its heavy 0 isotopes) was lost during metamorphism, inverse correlations between bulk (delta)O-18 and bulk (delta)O-17 with petrologic type were produced. The H5 chondrites that were ejected from their parent body approx.7.5 Ma ago during a major impact event probably had been within a few kilometers of each other since they accreted approx.4.5 Ga ago. There are significant differences in the <span class="hlt">olivine</span> compositional distributions among these rocks; these reflect stochastic nebular sampling of the oxidant (Le., phyllosilicates with high (delta)O-17) on a 0.1-1 km scale during agglomeration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/920847','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/920847"><span id="translatedtitle"><span class="hlt">Olivine</span>-FeS Partial-Melt</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Roberts, J; Siebert, J; Ryerson, F J; Kinney, J</p> <p>2006-10-02</p> <p>The figure shows Fe-S-filled melt channels in <span class="hlt">olivine</span> created at high temperature and pressure. The 3D image was obtained on Beamline 8.3.2 at the Advanced Light Source, Lawrence Berkeley Laboratory, with a spatial resolution of better than two microns (<span class="hlt">bar</span> is 10 microns). Permeability of Fe-S melts in <span class="hlt">olivine</span> at high temperatures and pressures provides an important constraint on models of planetary core formation. Permeability must be inferred from empirical relationships based on microstructure. To date, estimates of permeability have varied by more than five orders of magnitude. To provide more accurate constraints, we used high-resolution synchrotron radiation computed tomography to image the three-dimensional network of melt-containing pores in an <span class="hlt">olivine</span> matrix, and calculated the permeability directly by solving the equations of Stokes flow through the actual pore network using a lattice-Boltzmann approach. These calculations provide an independent constraint on models of planetary core formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.129....1C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.129....1C"><span id="translatedtitle">Tungsten diffusion in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cherniak, D. J.; Van Orman, J. A.</p> <p>2014-03-01</p> <p>Diffusion of tungsten has been characterized in synthetic forsterite and natural <span class="hlt">olivine</span> (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and <span class="hlt">olivine</span> powders. Experiments were prepared by sealing the source material and polished <span class="hlt">olivine</span> under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the <span class="hlt">olivine</span> were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing <span class="hlt">olivine</span> are similar, and tungsten diffusion in <span class="hlt">olivine</span> shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in <span class="hlt">olivine</span> indicate that Hf-W ages in <span class="hlt">olivine</span>-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040059901&hterms=history&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DThe%2Bhistory%2Bof','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040059901&hterms=history&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DThe%2Bhistory%2Bof"><span id="translatedtitle">Metallic <span class="hlt">Chondrules</span> in NWA1390 (H3-6): Clues to Their History from Metallic Cu</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>LaBlue, A. R.; Lauretta, D. S.</p> <p>2004-01-01</p> <p>A recent study of ordinary chondrites suggests that many long-recognized shock indicators in <span class="hlt">olivine</span> and pyroxene minerals may be erased by post-shock annealing. Therefore, the presence of other indicators of shock, which can not be erased by subsequent heating, are important to fully characterize the history of chondritic meteorites. One such proposed indicator is metallic Cu, which occurs in at least 2/3 of ordinary chondrites. Here we present a comparative study of two metallic <span class="hlt">chondrules</span> in the NWA1390 ordinary chondrite, both of which contain appreciable Cu in the Fe,Ni metal phase and one that is partially rimmed by metallic Cu.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PNAS..113.2886B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PNAS..113.2886B"><span id="translatedtitle">Tungsten isotopic constraints on the age and origin of <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Budde, Gerrit; Kleine, Thorsten; Kruijer, Thomas S.; Burkhardt, Christoph; Metzler, Knut</p> <p>2016-03-01</p> <p><span class="hlt">Chondrules</span> may have played a critical role in the earliest stages of planet formation by mediating the accumulation of dust into planetesimals. However, the origin of <span class="hlt">chondrules</span> and their significance for planetesimal accretion remain enigmatic. Here, we show that <span class="hlt">chondrules</span> and matrix in the carbonaceous chondrite Allende have complementary 183W anomalies resulting from the uneven distribution of presolar, stellar-derived dust. These data refute an origin of <span class="hlt">chondrules</span> in protoplanetary collisions and, instead, indicate that <span class="hlt">chondrules</span> and matrix formed together from a common reservoir of solar nebula dust. Because bulk Allende exhibits no 183W anomaly, <span class="hlt">chondrules</span> and matrix must have accreted rapidly to their parent body, implying that the majority of <span class="hlt">chondrules</span> from a given chondrite group formed in a narrow time interval. Based on Hf-W chronometry on Allende <span class="hlt">chondrules</span> and matrix, this event occurred ˜2 million years after formation of the first solids, about coeval to <span class="hlt">chondrule</span> formation in ordinary chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19840054478&hterms=trace+metals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dtrace%2Bmetals','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19840054478&hterms=trace+metals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dtrace%2Bmetals"><span id="translatedtitle">Trace elements in rims and interiors of Chainpur <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilkening, L. L.; Boynton, W. V.; Hill, D. H.</p> <p>1984-01-01</p> <p>Trace elements were measured in the rims and interiors of nine <span class="hlt">chondrules</span> separated from the Chainpur LL-3 chondrite. Whole rock samples of Chainpur and samples of separated rims were also measured. <span class="hlt">Chondrule</span> rims are moderately enriched in siderophile and volatile elements relative to the <span class="hlt">chondrule</span> interiors. The enriched volatile elements include the lithophilic volatile element Zn. The moderate enrichment of volatiles in <span class="hlt">chondrule</span> rims and the lack of severe depletion in <span class="hlt">chondrules</span> can account for the complete volatile inventory in Chainpur. These results support a three-component model of chondrite formation in which metal plus sulfide, <span class="hlt">chondrules</span> plus rims and matrix silicates are mixed to form chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950012923&hterms=flashing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dflashing','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950012923&hterms=flashing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dflashing"><span id="translatedtitle"><span class="hlt">Chondrule</span> precursors and cooling paths: The sulfur evidence</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zanda, B.; Yu, Y.; Bourot-Denise, M.; Hewins, R. H.; Connolly, H. C., Jr.</p> <p>1994-01-01</p> <p>The behavior of moderately volatile elements (Na and S) is controversial but critical in understanding <span class="hlt">chondrule</span> precursors and heating processes. Sulfide appeared to be present in most <span class="hlt">chondrules</span>, but S should have been vaporized during <span class="hlt">chondrule</span> formation. In fact, S is extensively redistributed in the course of metamorphism, and its abundance at the end of <span class="hlt">chondrule</span> formation can only be inferred from the least equilibrated chondrites. Our study of 530 <span class="hlt">chondrules</span> from Renazzo (CR2) and Semarkona (LL3.0) shows partial volatilization of S during <span class="hlt">chondrule</span> formation and our melting experiments define conditions for total loss or partial retention of S.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.147...43C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.147...43C"><span id="translatedtitle">Titanium diffusion in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cherniak, Daniele J.; Liang, Yan</p> <p>2014-12-01</p> <p>Diffusion of Ti has been characterized in natural <span class="hlt">olivine</span> and synthetic forsterite. Experiments on the natural <span class="hlt">olivines</span> were run under buffered conditions (IW and NNO), and those on synthetic forsterite were run in air. Titanium diffusion appears relatively insensitive to crystallographic orientation and oxygen fugacity under the range of investigated conditions, and diffusivities are similar for Fe-bearing <span class="hlt">olivine</span> and forsterite. For Ti diffusion in synthetic forsterite, we obtain the following Arrhenius relation for diffusion over the temperature range 900-1400 °C:</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950012909&hterms=ip&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dip','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950012909&hterms=ip&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dip"><span id="translatedtitle"><span class="hlt">Chondrule</span> formation in the radiative accretional shock</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ruzmaikina, T. V.; Ip, W.</p> <p>1994-01-01</p> <p>The physical, mineralogical, and isotopic properties of <span class="hlt">chondrules</span> strongly indicate that they were formed by the rapid melting and resolidification of preexisting solids composed of primitive material. The <span class="hlt">chondrule</span> precursors were heated to temperatures of about 1800 K in short high-temperature events, followed by cooling with a rate of 10(exp 2)-10(exp 3) K/hr. A heat input of about 1500 J/g is required to heat <span class="hlt">chondrule</span> precursors to such a temperature and melt them. Lightning discharges and flares in the solar nebula, and heating of the <span class="hlt">chondrule</span> precursors by friction with gas decelerated in the accretional shock or in a shock (of unspecified origin) within the solar nebula, have been discussed as possible mechanisms for <span class="hlt">chondrule</span> formation. One advantage of <span class="hlt">chondrule</span> formation in large-scale shocks is that a lot of dust material can be processed. An accretional shock, which is produced by infalling gas of the presolar cloud when it collides with the solar nebula, belongs to this type of shock. In 1984 Wood considered the possibility of <span class="hlt">chondrule</span> formation in the accretional shock by heating of <span class="hlt">chondrule</span> precursors by gas drag. He concluded that the density in the accreting material is much lower than needed to melt silicates at the distance of the asteroid belt if the accreting matter had the cosmic ratio of dust to gas, and the mass of the solar nebula did not exceed 2 solar mass units. Melting of <span class="hlt">chondrule</span> precursors is difficult because of their effective cooling by thermal radiation. Suppression of the radiative cooling of individual grains in dust swarms, which are opaque to thermal emission, was considered to be the only possible means of <span class="hlt">chondrule</span> formation in solar nebula shocks. Previous models of solid grain melting in solar nebula shocks have neglected gas cooling behind the shock front, i.e., they considered adiabatic shocks. In this paper we show that large dust grains could be heated much stronger than was supposed by these authors, because of effects associated with the gas cooling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950012911&hterms=grain+condensation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgrain%2Bcondensation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950012911&hterms=grain+condensation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgrain%2Bcondensation"><span id="translatedtitle">Heating during solar nebula formation and Mg isotopic fractionation in precursor grains of CAIs and <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sasaki, S.; Nagahara, H.; Kitagami, K.; Nakagawa, Y.</p> <p>1994-01-01</p> <p>In some Ca-Al-rich inclusion (CAI) grains, mass-dependent isotopic fractionations of Mg, Si, and O are observed and large Mg isotopic fractionation is interpreted to have been produced by cosmochemical processes such as evaporation and condensation. Mass-dependent Mg isotopic fractionation was found in <span class="hlt">olivine</span> <span class="hlt">chondrules</span> of Allende meteorites. Presented is an approximate formula for the temperature of the solar nebula that depends on heliocentric distance and the initial gas distribution. Shock heating during solar nebula formation can cause evaporative fractionation within interstellar grains involved in a gas at the inner zone (a less than 3 AU) of the disk. Alternatively collision of late-accreting gas blobs might cause similar heating if Sigma(sub s) and Sigma are large enough. Since the grain size is small, the solid/gas mass ratio is low and solar (low P(sub O2)), and the ambient gas pressure is low, this heating event could not produce <span class="hlt">chondrules</span> themselves. <span class="hlt">Chondrule</span> formation should proceed around the disk midplane after dust grains would grow and sediment to increase the solid/gas ratio there. The heating source there is uncertain, but transient rapid accretion through the disk could release a large amount of heat, which would be observed as FU Orionis events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30R.519H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30R.519H"><span id="translatedtitle">An Evaluation of Microcomputer-Based Strain Analysis Techniques on Meteoritic <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hill, H. G. M.</p> <p>1995-09-01</p> <p>Introduction: <span class="hlt">Chondrule</span> flattening and distinct foliation are preserved in certain chondrites [1] and have been interpreted, by some, as evidence of shock-induced pressure through hypervelocity impacts on parent bodies [2]. Recently, mean aspect ratios of naturally and artificially shocked <span class="hlt">chondrules</span>, in the Allende (CV3) chondrite, have been correlated with shock intensity [3] using established shock stage criteria [4]. Clearly, quantification of <span class="hlt">chondrule</span> deformation and appropriate petrographic criteria can be useful tools for constraining parent body shock history and, possibly, post-shock heating [3]. Here, strain analysis techniques (R(sub)(f)/phi and Fry) normally employed in structural geology, have been adapted and evaluated [5], for measuring mean <span class="hlt">chondrule</span> strain, and orientation. In addition, the possible use of such strain data for partial shock stage classification is considered. R(sub)(f)/phi and Fry Analysis: The relationship between displacement and shape changes in rocks is known as strain [6] and assumes that an initial circle with a unit radius is deformed to form an ellipse, the finite strain ellipse (Rf). The strain ratio (Rs) is an expression of the change of shape. The orientation of the strain ellipse (phi) is the angle subtended between the semi-major axes and the direction of a fixed point of reference. Generally, log mean Rf ~ Rs and, therefore, the approximation Rf = Rs is valid. For <span class="hlt">chondrules</span>, this is reasonable as they were originally molten, or partially-molten, droplets [7]. Fry's 'center-to-center' geological strain analysis technique [8] is based on the principle that the distribution of particle centers in rocks can sometimes be used to determine the state of finite strain (Rf). Experimental Techniques: The Bovedy (L3) chondrite was chosen for investigation as it contains abundant, oriented, elliptical <span class="hlt">chondrules</span> [5]. Hardware employed consisted of a Macintosh microcomputer and a flat-bed scanner. <span class="hlt">Chondrule</span> outlines, obtained from macrophotographic tracings of four complete thin-sections (total area 8.2 cm2) and a sawn slab (49.45cm2), were digitally scanned using application Ofoto v. 1.0.0^(TM). <span class="hlt">Chondrule</span> outline (pict) files were then exported to a fabric analysis program, Image v. 1.44, and Rf values obtained thereafter exported to a spreadsheet environment for manipulation. Fry analysis was undertaken with an interactive program, Fry v. 5.0 [9] using the same pict files as before. <span class="hlt">Chondrule</span> central points were manually inserted and center-to-center distances, when calculated, were displayed on screen in a way which echoes mean <span class="hlt">chondrule</span> strain and orientation. Results and Conclusion. 364 <span class="hlt">chondrule</span> outlines (three thin-sections and a sawn slab) were analysed by R(sub)(f)/phi and Fry techniques. In its present form, the Fry technique was judged to be unsuited to <span class="hlt">chondrule</span> shape analysis as it is too dependant on grain size, i.e. the smallest grain, and the need for a planar homogenous sample bearing several hundred grains [8]. Recent developments in the Fry technique [10] may make it more suitable for <span class="hlt">chondrule</span> analysis. Representative strain (Rf) data obtained for parallel thin-sections Bovedy M5385b and M5385c (total of 158 <span class="hlt">chondrules</span>) were 1.49 and 1.41 respectively. Corresponding phi values were 115.0 degrees and 114.6 degrees respectively (with respect to a fixed reference point). Rf data together with petrographic shock features noted, mostly in <span class="hlt">olivine</span> (e.g. planar fractures, undulatory extinction and weak mosaicism), were suggestive of shock stage S3 [4]. The degree of <span class="hlt">chondrule</span> flattening and the nature of the (S3) shock effects observed are comparable with artifically flattened <span class="hlt">chondrules</span> belonging to the same shock stage [3, 11]. The R(sub)(f)/phi technique evaluated was found to be more precise and quantitative than other methods previously employed for measuring maximum and minimum <span class="hlt">chondrule</span> axes and orientation. Furthermore, it can provide reliable strain (axial, orientation) data for material subjected to very low grades of shock which would otherwise be difficult to quantify. References: [1] Cain P. M. et al. (1986) EPSL, 77, 165-175. [2] Scott E. R. D. et al. (1992) GCA, 56, 4281-4293. [3] Nakamura T. et al. (1995) Meteoritics, 30, 344-347. [4] St"ffler D. et al. (1992) GCA, 55, 3485-3867. [5] Hill H. G. M. (1994) M.Sc. thesis, Univ. of Dublin. [6] Ramsay J. G. and Huber M. I. (1983) The Techniques of Modern Structural Geology. Volume 1: Strain Analysis, Academic, London. [7] Grossman J. N. et al. (1988) in Meteorites and the Early Solar System (J. F. Kerridge and M. F. Matthews, eds.), 619-659, Univ. of Arizona, Tucson. [8] Fry N. (1979) Tectonophys., 60, 89-105. [9] De Paor D. G. (1989) J. Geol. Educ., 37, 171-180. [10] Erslev E. A. and Ge H. (1990) J. Structural Geol., 12, 1047-59 [11] Schmitt R. T. et al. (1994) Meteoritics, 29, 529-530.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010059877','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010059877"><span id="translatedtitle">On the Lower Limit of <span class="hlt">Chondrule</span> Cooling Rates: The Significance of Iron Loss in Dynamic Crystallization Experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paque, Julie M.; Connolly, Harold C., Jr.; Lofgren, Gary E.</p> <p>1998-01-01</p> <p>It is unlikely that the presence of <span class="hlt">chondrules</span>, and thus their formation, within the protoplanetary nebula would be predicted if it were not for their ubiquitous presence in most chondritic meteorites. The study of these enigmatic, igneous objects has a direct influence on how meteoritic and solar system researchers model the processes operating and the materials present within our protoplanetary nebula. Key to understanding <span class="hlt">chondrule</span> formation is a determination of constraints on their thermal histories. The three important variables in this history are their peak melting temperatures, the duration of their melting at peak temperatures, and the rate at which these object cool. Although these three variables are interdependent, it is cooling rate that provides the most powerful constraint. Cooling rate has a direct affect on the development of both crystal morphology and the elemental distributions within these grains. To date, experiments have indicated that <span class="hlt">chondrule</span> cooling rates are in the range of 10's to 100's of degrees per hour for porphyritic <span class="hlt">chondrules</span> (the most abundant type). The cooling rate for radial and <span class="hlt">barred</span> <span class="hlt">chondrules</span> is thought to be more rapid. To generate these cooling rates (rapid relative to the cooling of the nebula as a whole, but slow compared to simple black body radiation) the environment of <span class="hlt">chondrule</span> formation must have been localized, and the abundance of solid materials must have been greatly enhanced above a gas of solar composition. Thus accurate determinations of <span class="hlt">chondrule</span> cooling rates is critical in understanding both their formation and the nebular environment in which they formed. In a quest to more accurately determine the lower limit on cooling rates and to determine in more detail the effects of Fe loss from a molten sample to Pt wire loops, Weinbruch et al. have explored this issue experimentally and reevaluated the findings of Radomsky and Hewins in light of their new results. The basic conclusions of their paper are an important contribution to our understanding of how experimental techniques can affect established constraints on <span class="hlt">chondrule</span> formation and are thus of interest to a wide audience. We do believe, however, that their methodology produces results that provide inappropriate impressions of the applicability of their study to <span class="hlt">chondrule</span> formation and nebular processes. Furthermore, the extensive body of previous experimental work on <span class="hlt">chondrule</span> bulk compositions cannot be invalidated, as they suggest, by the results of Weinbruch et al. It is for these reasons that within this comment we address to applicability of the results presented by Weinbruch et al. to previous studies, and illustrate how the experimental conditions chosen for their series of experiments introduced a significant bias in their results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040059896&hterms=CAIS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DCAIS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040059896&hterms=CAIS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DCAIS"><span id="translatedtitle">Lunar and Planetary Science XXXV: <span class="hlt">Chondrules</span> and CAIs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p>The session "<span class="hlt">Chondrules</span> and CAI's" included the following reports:Metallic <span class="hlt">Chondrules</span> in NWA 1390 (H3-6): Clues to Their History from Metallic Cu; Relationship Between Bulk Chemical Composition and Formation Age of <span class="hlt">Chondrules</span> in Bishunpur and Krymka; Relict Forsterite in <span class="hlt">Chondrules</span>: Implications for Cooling Rates; An Evaluation of Quantitative Methods of Determining the Degree of Melting Experienced by a <span class="hlt">Chondrule</span>; Rare Earth Element Fractionation in <span class="hlt">Chondrules</span>; Mineralogy and Petrology of <span class="hlt">Chondrules</span> in Carbonaceous Chondrite NWA 770; Isotopic Cosmobarometry: A Synthesis of Concepts and Implications for <span class="hlt">Chondrule</span> and CAI Formation Mechanisms; Further Investigations of Minor Element Distributions in Spinels in Type B CAIs; and Trace Element Compositions of the Sublayers Making Up W-L Rims on CAI .</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000081081&hterms=petrology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dpetrology','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000081081&hterms=petrology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dpetrology"><span id="translatedtitle">Chemistry and Petrology of <span class="hlt">Chondrules</span> from the Mokoia CV Chondrite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jones, R. H.; Schilk, A. J.</p> <p>2000-01-01</p> <p>Bulk chemical compositions of 94 <span class="hlt">chondrules</span> from Mokoia have been obtained by INAA. Elemental abundances are correlated with petrology. Chemical and petrological properties are very similar to <span class="hlt">chondrules</span> from Allende and do not show strong alteration signatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22341965','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22341965"><span id="translatedtitle">Photophoretic strength on <span class="hlt">chondrules</span>. 1. Modeling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Loesche, Christoph; Wurm, Gerhard; Teiser, Jens; Friedrich, Jon M.; Bischoff, Addi</p> <p>2013-12-01</p> <p>Photophoresis is a physical process that transports particles in optically thin parts of protoplanetary disks, especially at the inner edge and at the optical surface. To model the transport and resulting effects in detail, it is necessary to quantify the strength of photophoresis for different particle classes as a fundamental input. Here, we explore photophoresis for a set of <span class="hlt">chondrules</span>. The composition and surface morphology of these <span class="hlt">chondrules</span> were measured by X-ray tomography. Based on the three-dimensional models, heat transfer through illuminated <span class="hlt">chondrules</span> was calculated. The resulting surface temperature map was then used to calculate the photophoretic strength. We found that irregularities in particle shape and variations in composition induce variations in the photophoretic force. These depend on the orientation of a particle with respect to the light source. The variation of the absolute value of the photophoretic force on average over all <span class="hlt">chondrules</span> is 4.17%. The deviation between the direction of the photophoretic force and illumination is 3.°0 ± 1.°5. The average photophoretic force can be well approximated and calculated analytically assuming a homogeneous sphere with a volume equivalent mean radius and an effective thermal conductivity. We found an analytic expression for the effective thermal conductivity. The expression depends on the two main phases of a <span class="hlt">chondrule</span> and decreases with the amount of fine-grained devitrified, plagioclase-normative mesostasis up to factor of three. For the <span class="hlt">chondrule</span> sample studied (Bjurböle chondrite), we found a dependence of the photophoretic force on <span class="hlt">chondrule</span> size.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PEPI..172....5B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PEPI..172....5B"><span id="translatedtitle">Cooling rate of <span class="hlt">chondrules</span> in ordinary chondrites revisited by a new geospeedometer based on the compensation rule</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Béjina, Frédéric; Sautter, Violaine; Jaoul, Olivier</p> <p>2009-01-01</p> <p>For several decades efforts to constrain chondrite cooling rates from diffusion zoning in <span class="hlt">olivine</span> gave rise to a range of values from 5 to 8400 K/h (Desch, S.J., Connolly Jr., H.C., 2002. A model for the thermal processing of particles in solar nebula shocks: application to cooling rates of <span class="hlt">chondrules</span>. Meteorit. Planet. Sci. 37, 183-208; Greeney, S., Ruzicka, A., 2004. Relict forsterite in <span class="hlt">chondrules</span>: implications for cooling rates. Lunar Planet. Sci. XXXV, abstract # 1246.). Such large uncertainties directly reflect the variability of diffusion data. Alternatively, from this variability results a compensation rule, log D0 = a + bE (diffusion coefficients are written D = D0 exp(- E/ RT)). We test a new geospeemetry approach, based on this rule, on cooling of <span class="hlt">chondrules</span> in chondrites, Sahara-97210 LL 3.2 and Wells LL 3.3. Greeney and Ruzicka (2004) matched Fe-Mg diffusion profiles in <span class="hlt">olivine</span> from these chondrites with cooling rates between 200 and 6000 K/h. In our geospeedometry model, the use of the compensation rule greatly reduces the uncertainties by avoiding the choice of one diffusion coefficient among many. The cooling rates we found are between 700 and 3600 K/h for Sahara and 700-1600 K/h for Wells. Finally, we discuss the influence of our analytical model parameters on our cooling rate estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10145799','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10145799"><span id="translatedtitle">On the origin of porphyritic <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blander, M.; Unger, L.; Pelton, A.; Ericksson, G.</p> <p>1994-05-01</p> <p>A computer program for the complex equilibria in a cooling nebular gas was used to explore a possible origin of porphyritic <span class="hlt">chondrules</span>, the major class of <span class="hlt">chondrules</span> in chondritic meteorites. It uses a method of accurately calculating the thermodynamic properties of molten multicomponent aluminosilicates, which deduces the silicate condensates vs temperature and pressure of a nebular gas. This program is coupled with a chemical equilibrium algorithm for systems with at least 1000 chemical species; it has a data base of over 5000 solid, liquid, and gaseous species. Results are metastable subcooled liquid aluminoscilicates with compositions resembling types IA and II porphyritic <span class="hlt">chondrules</span> at two different temperatures at any pressure between 10{sup {minus}2} and 1 (or possibly 10{sup {minus}3} to 5) atm. The different types of <span class="hlt">chondrules</span> (types I, II, III) could have been produced from the same gas and do not need a different gas for each apparent oxidation state; thus, the difficulty of current models for making porphyritic <span class="hlt">chondrules</span> by reheating different solids to just below their liquidus temperatures in different locations is not necessary. Initiation of a stage of crystallization just below liquidus is part of the natural crystallization (recalescence) process from metastable subcooled liquidus and does not require an improbably heating mechanism. 2 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..258..120P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..258..120P"><span id="translatedtitle">Detection of new <span class="hlt">olivine</span>-rich locations on Vesta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palomba, Ernesto; Longobardo, Andrea; De Sanctis, Maria Cristina; Zinzi, Angelo; Ammannito, Eleonora; Marchi, Simone; Tosi, Federico; Zambon, Francesca; Capria, Maria Teresa; Russell, Christopher T.; Raymond, Carol A.; Cloutis, Edward A.</p> <p>2015-09-01</p> <p>The discovery of <span class="hlt">olivine</span> on Vesta's surface by the VIR imaging spectrometer onboard the Dawn space mission has forced us to reconsider our views of Vestan petrogenetic models. <span class="hlt">Olivines</span> were expected to be present in the interior of Vesta: in the mantle of a vertically layered body as invoked by the magma ocean models, or at the base (or within) the mantle-crust boundary as proposed by fractionation models. <span class="hlt">Olivines</span> have been detected by VIR-Dawn in two wide areas near Arruntia and Bellicia, regions located in the northern hemisphere. Interestingly, these <span class="hlt">olivine</span>-rich terrains are far from the Rheasilvia and the more ancient Veneneia basins, which are expected to have excavated the crust down to reach the mantle. In this work we present our attempts to identify other undetected <span class="hlt">olivine</span> rich areas on Vesta by using spectral parameters sensitive to <span class="hlt">olivine</span> such as the Band Area Ratio (<span class="hlt">BAR</span>) and other specific parameters created for the detection of <span class="hlt">olivines</span> on Mars (forsterite, fayalite and a generic <span class="hlt">olivine</span> index). As a preliminary step we calibrated these parameters by means of VIS-IR spectra of different HED meteorite samples: behaviors versus sample grain size and albedo were analyzed and discussed. We selected the <span class="hlt">BAR</span> and the Forsterite Index as the best parameters that can be used on Vesta. A cross-correlation analysis has been applied in order to detect <span class="hlt">olivine</span> signature on the VIR hyperspectral cubes. These detections have then been confirmed by an anti-correlation analysis between the <span class="hlt">BAR</span> and one of the <span class="hlt">olivine</span> parameters, independent of the first method applied. In agreement with the recent discovery, Arruntia and Bellicia were found to be as the most <span class="hlt">olivine</span>-rich areas, i.e. where the parameter values are strongest. In addition we detected 6 new regions, all but one located in the Vesta north hemisphere. This result confirms again that the old petrogenetic models cannot be straightforwardly applied to Vesta and should be reshaped in the view of these new detections. An alternative and very recent option can be represented by the model according to which surface "eruption" of material from the mantle, including <span class="hlt">olivine</span> can reach the surface of Vesta.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19870066836&hterms=Empa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DEmpa','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19870066836&hterms=Empa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DEmpa"><span id="translatedtitle"><span class="hlt">Chondrules</span>, matrix and coarse-grained <span class="hlt">chondrule</span> rims in the Allende meteorite - Origin, interrelationships, and possible precursor components</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.; Wasson, John T.</p> <p>1987-01-01</p> <p>INAA and broad-beam EMPA are used to determine the bulk compositions of 20 <span class="hlt">chondrules</span>, 13 coarse-grained <span class="hlt">chondrule</span> rims, and one nonporphyritic CV <span class="hlt">chondrule</span> (NPCVC) from CV3 Allende (and of one NPCVC each from Leoville and Vigarano). The data are presented in extensive tables and graphs and analyzed in detail. Five probable <span class="hlt">chondrule</span> precursor components are deduced, and the solar-nebula processes giving rise to them (and probably to the coarse-grained rims as well) are discussed. It is suggested that the formation of the rimmed <span class="hlt">chondrules</span> involved nebular reheating in space, after the accretion of dusty coatings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf..407P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf..407P"><span id="translatedtitle">Detection of new <span class="hlt">olivine</span>-rich locations on Vesta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palomba, E.; Longobardo, A.; De Sanctis, M.; Tosi, F.; Capria, M.; Capaccioni, F.; Ammannito, E.; Raymond, C.; Russell, C.</p> <p>2014-07-01</p> <p>The recent discovery of <span class="hlt">olivines</span> on Vesta by the VIR imaging spectrometer onboard the Dawn space mission changed dramatically the vision about the Vestan petrogenetic models [1]. Before that, <span class="hlt">olivines</span> were expected to be present in the Vesta interior: in the mantle of a vertically layered body as invoked by the magma ocean models [2] or at the base of (or within) the mantle-crust boundary as claimed by fractionation models [3]. <span class="hlt">Olivines</span> were detected by VIR-Dawn in two wide areas near the Arruntia and Bellicia regions. These are located in the northern hemisphere and not in the south, where the Rheasilvia and the more ancient Veneneia huge basins should have excavated the crust down to reach the mantle. In this work, we present our attempts to retrieve other undetected <span class="hlt">olivine</span>-rich areas on Vesta by using spectral parameters sensitive to <span class="hlt">olivine</span> such as the Band Area Ratio (<span class="hlt">BAR</span>) and other specific parameters created for the detection of <span class="hlt">olivines</span> on Mars (forsterite, fayalite, and a generic <span class="hlt">olivine</span> index [4,5]). As a preliminary step, we calibrated these parameters by means of VIS-IR spectra of different HED meteorite samples: their behaviors as a function of sample grain size and albedo were retrieved and discussed. We selected the <span class="hlt">BAR</span> and the forsterite index as the best parameters that can be used on Vesta and applied two independent methods to detect <span class="hlt">olivine</span> signatures on the VIR hyperspectral cubes: a cross-correlation and an anti-correlation analysis between the <span class="hlt">BAR</span> and one of the <span class="hlt">olivine</span> parameters. In agreement with the recent discovery, Arruntia and Bellicia were the most <span class="hlt">olivine</span> rich areas. In addition, we detected 6 new regions, all but one located in Vesta's northern hemisphere. This result confirms again that the old petrogenetic models cannot be applied, in a straightforward way, to Vesta and should be reshaped in the view of these new detections. An alternative and very recent option can be represented by the model described in [4], in which surface ''eruption'' of material from the mantle, including <span class="hlt">olivine</span>, can reach the surface of Vesta.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS..tmp..247B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS..tmp..247B"><span id="translatedtitle">Uranium isotopic composition and absolute ages of Allende <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brennecka, G. A.; Budde, G.; Kleine, T.</p> <p>2015-11-01</p> <p>A handful of events, such as the condensation of refractory inclusions and the formation of <span class="hlt">chondrules</span>, represent important stages in the formation and evolution of the early solar system and thus are critical to understanding its development. Compared to the refractory inclusions, <span class="hlt">chondrules</span> appear to have a protracted period of formation that spans millions of years. As such, understanding <span class="hlt">chondrule</span> formation requires a catalog of reliable ages, free from as many assumptions as possible. The Pb-Pb chronometer has this potential; however, because common individual <span class="hlt">chondrules</span> have extremely low uranium contents, obtaining U-corrected Pb-Pb ages of individual <span class="hlt">chondrules</span> is unrealistic in the vast majority of cases at this time. Thus, in order to obtain the most accurate 238U/235U ratio possible for <span class="hlt">chondrules</span>, we separated and pooled thousands of individual <span class="hlt">chondrules</span> from the Allende meteorite. In this work, we demonstrate that no discernible differences exist in the 238U/235U compositions between <span class="hlt">chondrule</span> groups when separated by size and magnetic susceptibility, suggesting that no systematic U-isotope variation exists between groups of <span class="hlt">chondrules</span>. Consequently, <span class="hlt">chondrules</span> are likely to have a common 238U/235U ratio for any given meteorite. A weighted average of the six groups of <span class="hlt">chondrule</span> separates from Allende results in a 238U/235U ratio of 137.786 ± 0.004 (±0.016 including propagated uncertainty on the U standard [Richter et al. 2010]). Although it is still possible that individual <span class="hlt">chondrules</span> have significant U isotope variation within a given meteorite, this value represents our best estimate of the 238U/235U ratio for Allende <span class="hlt">chondrules</span> and should be used for absolute dating of these objects, unless such <span class="hlt">chondrules</span> can be measured individually.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50.1338V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50.1338V"><span id="translatedtitle">Nonporphyritic <span class="hlt">chondrules</span> and <span class="hlt">chondrule</span> fragments in enstatite chondrites: Insights into their origin and secondary processing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Varela, M. E.; Sylvester, P.; BrandstäTter, F.; Engler, A.</p> <p>2015-08-01</p> <p>Sixteen nonporphyritic <span class="hlt">chondrules</span> and <span class="hlt">chondrule</span> fragments were studied in polished thin and thick sections in two enstatite chondrites (ECs): twelve objects from unequilibrated EH3 Sahara 97158 and four objects from equilibrated EH4 Indarch. Bulk major element analyses, obtained with electron microprobe analysis (EMPA) and analytical scanning electron microscopy (ASEM), as well as bulk lithophile trace element analyses, determined by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), show that volatile components (K2O + Na2O versus Al2O3) scatter roughly around the CI line, indicating equilibration with the chondritic reservoir. All lithophile trace element abundances in the <span class="hlt">chondrules</span> from Sahara 97158 and Indarch are within the range of previous analyses of nonporphyritic <span class="hlt">chondrules</span> in unequilibrated ordinary chondrites (UOCs). The unfractionated (solar-like) Yb/Ce ratio of the studied objects and the mostly unfractionated refractory lithophile trace element (RLTE) abundance patterns indicate an origin by direct condensation. However, the objects possess subchondritic CaO/Al2O3 ratios; superchondritic (Sahara 97158) and subchondritic (Indarch) Yb/Sc ratios; and chondritic-normalized deficits in Nb, Ti, V, and Mn relative to RLTEs. This suggests a unique nebular process for the origin of these ECs, involving elemental fractionation of the solar gas by the removal of oldhamite, niningerite, and/or another phase prior to <span class="hlt">chondrule</span> condensation. A layered <span class="hlt">chondrule</span> in Sahara 97158 is strongly depleted in Nb in the core compared to the rim, suggesting that the solar gas was heterogeneous on the time scales of <span class="hlt">chondrule</span> formation. Late stage metasomatic events produced the compositional diversity of the studied objects by addition of moderately volatile and volatile elements. In the equilibrated Indarch <span class="hlt">chondrules</span>, this late process has been further disturbed, possibly by a postaccretional process (diffusion?) that preferentially mobilized Rb with respect to Cs in the studied objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020046509&hterms=Weathering&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DWeathering','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020046509&hterms=Weathering&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DWeathering"><span id="translatedtitle">Microbial Weathering of <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McKay, D. S.; Longazo, T. G.; Wentworth, S. J.; Southam, G.</p> <p>2002-01-01</p> <p>Controlled microbial weathering of <span class="hlt">olivine</span> experiments displays a unique style of nanoetching caused by biofilm attachment to mineral surfaces. We are investigating whether the morphology of biotic nanoetching can be used as a biosignature. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DPS....4641503H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DPS....4641503H"><span id="translatedtitle">Exogenous <span class="hlt">Olivine</span> on Vesta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoffmann, Martin; Nathues, Andreas; Schäfer, Michael; Thangjam, Guneshwar; Le Corre, Lucille; Vishnu, Reddy; Christensen, Ulrich; Mengel, Kurt; Sierks, Holger; Vincent, Jean-Baptist; Cloutis, Edward A.; Russell, Christopher T.; Schäfer, Tanja; Gutierrez-Marques, Pablo; Hall, Ian; Ripken, Joachim; Büttner, Irene</p> <p>2014-11-01</p> <p>Vesta has conserved an early status of planetary evolution, demonstrated by the global coverage of HED lithology on its surface. Being sufficiently large to retain some material from slow projectiles, but small enough to prevent its complete evaporation during the impacts, this unique environment is ideal for distinction and identification of exogenous material. In particular, the distribution, concentration, and geological context of <span class="hlt">olivine</span> exposures are poorly consistent with a Vestan mantle origin. Similar arguments are valid for the areas of dark carbonaceous chondrite-like lithology, and a few other features with unusual visual spectral slopes. Most <span class="hlt">olivine</span> is found close to the large impact craters Bellicia, Arruntia, and Pomponia in the northern hemisphere, whose ejecta sheet is characterized by a mixing trend from an HED lithology to S- or A-type asteroid material. The <span class="hlt">olivine</span> has diagnostic significance for the extent and duration of differentiation during the early accretion of parent bodies in the asteroid region. Sources for exogenous <span class="hlt">olivine</span> are available in Vesta’s environment among A- and S-type asteroids. It is not clear, however, if it is derived mainly from achondritic or chondritic sources. On the other hand, the lack of evidence for Vesta’s mantle material implies constraints on its inner structure, e.g. the depth of the crust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920003705','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920003705"><span id="translatedtitle">Dynamic crystallization characteristics of enstatite chondrite <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lofgren, Gary E.; Dehart, John M.; Lanier, A. B.</p> <p>1991-01-01</p> <p>Although the chemical properties of enstatite and ordinary chondrites are distinctly different, they both contain <span class="hlt">chondrules</span> with a similar array of textures. This similarity suggests like origins. Textural studies using <span class="hlt">chondrule</span> compositions from ordinary chondrites suggest that these <span class="hlt">chondrules</span> have an igneous origin: either by crystallization from melts or from partial melts of crystalline material. In contrast, the cathodoluminescence (CL) properties of the enstatite from enstatite chondrites were interpreted to mean that mechanical aggregation played an important part in their formation. An alternative interpretation of these CL properties, however, suggests that variations in the minor element content of the enstatite, a probable result of igneous fractionation processes, could also produce different CL colors. An attempt was made to evaluate the two models by performing dynamic crystallization experiments on an average enstatite <span class="hlt">chondrule</span> composition and by looking at the resultant CL. The textures grown on experimentally crystallized E-chondrite melts confirm that formational processes are similar to those for the ordinary chondrites with the obvious exception of the oxidation state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22364945','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22364945"><span id="translatedtitle">REVISITING JOVIAN-RESONANCE INDUCED <span class="hlt">CHONDRULE</span> FORMATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nagasawa, M.; Tanaka, K. K.; Tanaka, H.; Nakamoto, T.; Miura, H.; Yamamoto, T.</p> <p>2014-10-10</p> <p>It is proposed that planetesimals perturbed by Jovian mean-motion resonances are the source of shock waves that form <span class="hlt">chondrules</span>. It is considered that this shock-induced <span class="hlt">chondrule</span> formation requires the velocity of the planetesimal relative to the gas disk to be on the order of ≳ 7 km s{sup –1} at 1 AU. In previous studies on planetesimal excitation, the effects of Jovian mean-motion resonance together with the gas drag were investigated, but the velocities obtained were at most 8 km s{sup –1} in the asteroid belt, which is insufficient to account for the ubiquitous existence of <span class="hlt">chondrules</span>. In this paper, we reexamine the effect of Jovian resonances and take into account the secular resonance in the asteroid belt caused by the gravity of the gas disk. We find that the velocities relative to the gas disk of planetesimals a few hundred kilometers in size exceed 12 km s{sup –1}, and that this is achieved around the 3:1 mean-motion resonance. The heating region is restricted to a relatively narrowband between 1.5 AU and 3.5 AU. Our results suggest that <span class="hlt">chondrules</span> were produced effectively in the asteroid region after Jovian formation. We also find that many planetesimals are scattered far beyond Neptune. Our findings can explain the presence of crystalline silicate in comets if the scattered planetesimals include silicate dust processed by shock heating.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020046273&hterms=Reproduction&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DReproduction','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020046273&hterms=Reproduction&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DReproduction"><span id="translatedtitle">Experimental Reproduction of Type 1B <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lofgren, G. E.; Le, L.</p> <p>2002-01-01</p> <p>We have replicated type 1B <span class="hlt">chondrule</span> textures and compositions with crystallization experiments in which UOC material was melted at 1400 deg.C and cooled at 5-1000 deg.C/hr using graphite crucibles in evacuated silica tubes to provide a reducing environment. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2229132J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2229132J"><span id="translatedtitle">Growth of Asteroids by <span class="hlt">Chondrule</span> Accretion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johansen, Anders; Mac Low, Mordecai-Mark; Lacerda, Pedro; Bizzarro, Martin</p> <p>2015-08-01</p> <p>Planetesimals can form from solid objects constrained by the meter-size barrier through concentration by sedimentation and streaming instabilities, followed by gravitational instability. We have performed the highest-resolution numerical simulations of this scenario to date. We find that the resulting size distribution displays significant discrepancies with the currently observed size distribution that cannot be ameliorated by collisional evolution over the lifetime of the Solar System. We then examine accretion of thick layers of <span class="hlt">chondrules</span> (or similarly-sized grains) by gas drag onto the population of planetesimals predicted from the streaming instability models as they undergo orbital and collisional evolution during the lifetime of the protoplanetary gas disk. These models yield a size distribution far more consistent with the observations. The gas drag mechanism for accretion further leads to size-sorting of the accreted <span class="hlt">chondrules</span> consistent with the <span class="hlt">chondrule</span> size distributions observed in ordinary chondrites. We find that the contribution of direct collisional growth of asteroids is minor in comparison to accretion of <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008Icar..195..895W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008Icar..195..895W"><span id="translatedtitle">Evaporation of nebular fines during <span class="hlt">chondrule</span> formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wasson, John T.</p> <p>2008-06-01</p> <p>Studies of matrix in primitive chondrites provide our only detailed information about the fine fraction (diameter <2 μm) of solids in the solar nebula. A minor fraction of the fines, the presolar grains, offers information about the kinds of materials present in the molecular cloud that spawned the Solar System. Although some researchers have argued that chondritic matrix is relatively unaltered presolar matter, meteoritic <span class="hlt">chondrules</span> bear witness to multiple high-temperature events each of which would have evaporated those fines that were inside the high-temperature fluid. Because heat is mainly transferred into the interior of <span class="hlt">chondrules</span> by conduction, the surface temperatures of <span class="hlt">chondrules</span> were probably at or above 2000 K. In contrast, the evaporation of mafic silicates in a canonical solar nebula occurs at around 1300 K and FeO-rich, amorphous, fine matrix evaporates at still lower temperatures, perhaps near 1200 K. Thus, during <span class="hlt">chondrule</span> formation, the temperature of the placental bath was probably >700 K higher than the evaporation temperatures of nebular fines. The scale of <span class="hlt">chondrule</span> forming events is not known. The currently popular shock models have typical scales of about 10 km. The scale of nebular lightning is less well defined, but is certainly much smaller, perhaps in the range 1 to 1000 m. In both cases the temperature pulses were long enough to evaporate submicrometer nebular fines. This interpretation disagrees with common views that meteoritic matrix is largely presolar in character and CI-chondrite-like in composition. It is inevitable that presolar grains (both those recognized by their anomalous isotopic compositions and those having solar-like compositions) that were within the hot fluid would also have evaporated. <span class="hlt">Chondrule</span> formation appears to have continued down to the temperatures at which planetesimals formed, possibly around 250 K. At temperatures >600 K, the main form of C is gaseous CO. Although the conversion of CO to CH 4 at lower temperatures is kinetically inhibited, radiation associated with <span class="hlt">chondrule</span> formation would have accelerated the conversion. There is now evidence that an appreciable fraction of the nanodiamonds previously held to be presolar were actually formed in the solar nebula. Industrial condensation of diamonds from mixtures of CH 4 and H 2 implies that high nebular CH 4/CO ratios favored nanodiamond formation. A large fraction of chondritic insoluble organic matter may have formed in related processes. At low nebular temperatures appreciable water should have been incorporated into the smoke that condensed following dust (and some <span class="hlt">chondrule</span>) evaporation. If <span class="hlt">chondrule</span> formation continued down to temperatures as low as 250 K this process could account for the water concentration observed in primitive chondrites such as LL3.0 and CO3.0 chondrites. Higher H 2O contents in CM and CI chondrites may reflect asteroidal redistribution. In some chondrite groups (e.g., CR) the Mg/Si ratio of matrix material is appreciably (30%) lower than that of <span class="hlt">chondrules</span> but the bulk Mg/Si ratio is roughly similar to the CI or solar ratio. This has been interpreted as a kind of closed-system behavior sometimes called "complementarity." This leads to the conclusion that nebular fines were efficiently agglomerated. Its importance, however is obscured by the observation that bulk Mg/Si ratios in ordinary and enstatite chondrites are much lower than those in carbonaceous chondrites, and thus that complementarity did not hold throughout the solar nebula.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028854','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028854"><span id="translatedtitle">Alkali elemental and potassium isotopic compositions of Semarkona <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Alexander, C.M. O'D.; Grossman, J.N.</p> <p>2005-01-01</p> <p>We report measurements of K isotope ratios in 28 Semarkona <span class="hlt">chondrules</span> with a wide range of petrologic types and bulk compositions as well as the compositions of CPX-mesostasis pairs in 17 type I Semarkona <span class="hlt">chondrules</span>, including two <span class="hlt">chondrules</span> with radial alkali zonation and 19 type II <span class="hlt">chondrules</span>. Despite the wide range in K/Al ratios, no systematic variations in K isotopic compositions were found. Semarkona <span class="hlt">chondrules</span> do not record a simple history of Rayleigh-type loss of K. Experimentally determined evaporation rates suggest that considerable alkali evaporation would have occurred during <span class="hlt">chondrule</span> formation. Nevertheless, based on Na CPX-mesostasis distribution coefficients, the alkali contents of the cores of most <span class="hlt">chondrules</span> in Semarkona were probably established at the time of final crystallization. However, Na CPX-mesostasis distribution coefficients also show that alkali zonation in type I Semarkona <span class="hlt">chondrules</span> was produced by entry of alkalis after solidification, probably during parent body alteration. This alkali metasomatism may have gone to completion in some <span class="hlt">chondrules</span>. Our preferred explanation for the lack of systematic isotopic enrichments, even in alkali depleted type I <span class="hlt">chondrule</span> cores, is that they exchanged with the ambient gas as they cooled. ?? The Meteoritical Society, 2005.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19790035010&hterms=grain+condensation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dgrain%2Bcondensation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19790035010&hterms=grain+condensation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dgrain%2Bcondensation"><span id="translatedtitle">On the origin of isolated <span class="hlt">olivine</span> grains in type 2 carbonaceous chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Olsen, E.; Grossman, L.</p> <p>1978-01-01</p> <p>Two possibilities exist for the origin of aggregates and isolated grains in C2 meteorites: (1) high-temperature phases that condensed directly from a solar nebular gas accumulated as aggregates and single grains on the parent bodies of carbonaceous chondrites and remained unaltered since, or (2) all high-temperature phases in these meteorites are now, or once were, insided <span class="hlt">chondrules</span> and have been melted out. Petrographic evidence for these two alternative models is examined critically. Four different scenarios to account for the kinds of aggregates and isolated grains in the Murchison C2 meteorite are studied. It is concluded that the majority of isolated <span class="hlt">olivine</span> grains in the matrix never underwent melting in a <span class="hlt">chondrule</span>-making stage. These crystal fragments and aggregates can thus be accounted for by direct condensation from a solar nebular gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950035331&hterms=silica&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsilica','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950035331&hterms=silica&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsilica"><span id="translatedtitle">Silica-merrihueite/roedderite-bearing <span class="hlt">chondrules</span> and clasts in ordinary chondrites: New occurrences and possible origin</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krot, Alexander N.; Wasson, John T.</p> <p>1994-01-01</p> <p>Merrihueite (K,Na)2(Fe,Mg)5Si12O30 (na less than 0.5, fe greater than 0.5, where na = Na/(Na + K), fe = Fe/(Fe + Mg) in atomic ratio) is a rare mineral described only in several <span class="hlt">chondrules</span> and irregularly-shaped fragments in the Mezo-Madaras L3 chondrite (Dodd et al., 1965; Wood and Holmberg, 1994). Roedderite (Na,K)2(Mg,Fe)5Si12O30 (na greater than 0.5, fe less than 0.5) has been found only in enstatite chondrites and in the reduced, subchondritic silicate inclusions in IAB irons (Fuchs, 1966; Rambaldi et al., 1984; Olsen, 1967). We described silica-roedderite-bearing clasts in L/LL3.5 ALHA77011 and LL3.7 ALHA77278, a silica-roedderite-bearing <span class="hlt">chondrule</span> in L3 Mezo-Madaras, and a silica-merrihueite-bearing <span class="hlt">chondrule</span> in L/LL3.5 ALHA77115. The findings of merrihueite and roedderite in ALHA77011, ALHA77115, ALHA77278 and Mezo-Madaras fill the compositional gap betweeen previously described roedderite in enstatite chondrites and silicate inclusions in IAB irons and merrihueite in Mezo-Madaras, suggesting that there is a complete solid solution of roedderite and merrihueite in meteorites. We infer that the silica- and merrihueite/roedderite-bearing <span class="hlt">chondrules</span> and clasts experienced a complex formational history including: (a) fractional condensation in the solar nebular that produced Si-rich and Al-poor precursors, (b) melting of fractionated nebular solids resulting in the formation of silica-pyroxene <span class="hlt">chondrules</span>, (c) in some cases, fragmentation in the nebula or on a parent body, (d) reaction of silica with alkali-rich gas that formed merrihueite/roedderite on a parent body, (e) formation of fayalitic <span class="hlt">olivine</span> and feerosilite-rich pyroxene due to reaction of silica with oxidized Fe on a parent body, and (f) minor thermal metamorphism, possibly generated by impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8382A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8382A"><span id="translatedtitle">"Black-colored <span class="hlt">olivines</span>" in peridotites: dehydrogenation from hydrous <span class="hlt">olivines</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arai, Shoji; Hoshikawa, Chihiro; Miura, Makoto</p> <p>2015-04-01</p> <p>Fresh <span class="hlt">olivines</span> that are black to the naked eye are found in some dunites. Peridotites are easily converted to be black in color, when serpentinized, due to production of secondary fine magnetite particles. The dunites that contain fresh but black-colored <span class="hlt">olivines</span> are usually coarse-grained. These coarse <span class="hlt">olivine</span> grains are sometimes very heterogeneous in color; the blackish part grades to whitish parts in single grains. The black color is due to homegeneous distribution of minute (< 10 microns) black particles in <span class="hlt">olivine</span>. They are rod-like or plate-like in shape in thin section, sometimes being aligned under crystallographic control of the host <span class="hlt">olivine</span>. <span class="hlt">Olivines</span> are clear and free of these inclusions around primary chromian spinel inclusions or chromian spinel lamellae (Arai, 1978). Raman spectroscopy indicates the minute black particles are magnetite always associated with diopside. It is interesting to note that <span class="hlt">olivine</span> in mantle peridotites accompanied by the black-colored dunites is totally free of the black inclusions, giving the ordinary colors (pale yellow to whitish) of Mg-rich <span class="hlt">olivine</span>. It is not likely that the magnetite inclusions formed through secondary oxidation of <span class="hlt">olivine</span> by invasion of oxygen, which is possible along cracks or grain boundaries. They most probably formed due to dehydrogenation from primary OH-bearing <span class="hlt">olivines</span> upon cooling. Hydrogen was quickly diffused out from the <span class="hlt">olivines</span> to leave magnetite and excess silica. The excess silica was possibly combined with a monticellite component to form diopside. The OH-bearing (hydrous) <span class="hlt">olivines</span> can be precipitated from hydrous magmas, and the hydrous nature of the magma can promote an increase in grain size due to faster diffusion of elements. The minute inclusions of magnetite + diopside is thus an indicator of primary hydrous character of host <span class="hlt">olivine</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980037669','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980037669"><span id="translatedtitle">Partitioning of Moderately Siderophile Elements Among <span class="hlt">Olivine</span>, Silicate Melt, and Sulfide Melt: Constraints on Core Formation in the Earth and Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gaetani, Glenn A.; Grove, Timothy L.</p> <p>1997-01-01</p> <p>This study investigates the effects of Variations in the fugacities of oxygen and sulfur on the partitioning of first series transition metals (V, Cr, Mn, Fe, Co, Ni. and Cu) and W among coexisting sulfide melt, silicate melt, and <span class="hlt">olivine</span>. Experiments were performed at 1 atm pressure, 1350 C, with the fugacities of oxygen and sulfur controlled by mixing CO2, CO, and SO2 gases. Starting compositions consisted of a CaO-MgO-Al2O3-SiO2-FeO-Na2O analog for a <span class="hlt">barred</span> <span class="hlt">olivine</span> <span class="hlt">chondrule</span> from an ordinary chondrite and a synthetic komatiite. The f(sub O2)/f(sub S2), conditions ranged from log of f(sub O2) = -7.9 to - 10.6, with log of f(sub S2) values ranging from - 1.0 to -2.5. Our experimental results demonstrate that the f(sub O2)/f(sub S2) dependencies of sulfide melt/silicate melt partition coefficients for the first series transition metals arc proportional to their valence states. The f(sub O2)/f(sub S2) dependencies for the partitioning of Fe, Co, Ni, and Cu are weaker than predicted on the basis of their valence states. Variations in conditions have no significant effect on <span class="hlt">olivine</span>/melt partitioning other than those resulting from f(sub O2)-induced changes in the valence state of a given element. The strong f(sub O2)/f(sub S2) dependence for the <span class="hlt">olivine</span>/silicate melt partitioning of V is attributable to a change of valence state, from 4+ to 3+, with decreasing f(sub O2). Our experimentally determined partition coefficients are used to develop models for the segregation of sulfide and metal from the silicate portion of the early Earth and the Shergottite parent body (Mars). We find that the influence of S is not sufficient to explain the overabundance of siderophile and chalcophile elements that remained in the mantle of the Earth following core formation. Important constraints on core formation in Mars are provided by our experimental determination of the partitioning of Cu between silicate and sulfide melts. When combined with existing estimates for siderophile element abundances in the Martian mantle and a mass balance constraint from Fe, the experiments allow a determination of the mass of the Martian core (approx. 17 to 22 wt% of the planet) and its S content (approx.0.4 wt%). These modeling results indicate that Mars is depleted in S, and that its core is solid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.V33A2729J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.V33A2729J"><span id="translatedtitle">Applicability of Henry's Law to helium solubility in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.</p> <p>2013-12-01</p> <p>Applicability of Henry's Law to helium solubility in <span class="hlt">olivine</span> We have experimentally determined helium solubility in San Carlos <span class="hlt">olivine</span> across a range of helium partial pressures (PHe) with the goal of quantifying how noble gases behave during partial melting of peridotite. Helium solubility in <span class="hlt">olivine</span> correlates linearly with PHe between 55 and 1680 <span class="hlt">bar</span>. This linear relationship suggests Henry's Law is applicable to helium dissolution into <span class="hlt">olivine</span> up to 1680 <span class="hlt">bar</span> PHe, providing a basis for extrapolation of solubility relationships determined at high PHe to natural systems. This is the first demonstration of Henry's Law for helium dissolution into <span class="hlt">olivine</span>. Averaging all the data of the PHe series yields a Henry's coefficient of 3.8(×3.1)×10-12 mol g-1 <span class="hlt">bar</span>-1. However, the population of Henry's coefficients shows a positive skew (skewness = 1.17), i.e. the data are skewed to higher values. This skew is reflected in the large standard deviation of the population of Henry's coefficients. Averaging the median values from each experiment yields a lower Henry's coefficient and standard deviation: 3.2(× 2.3)×10-12 mol g-1 <span class="hlt">bar</span>-1. Combining the presently determined helium Henry's coefficient for <span class="hlt">olivine</span> with previous determinations of helium Henry's coefficients for basaltic melts (e.g. 1) yields a partition coefficient of ~10-4. This value is similar to previous determinations obtained at higher PHe (2). The applicability of Henry's Law here suggests helium is incorporated onto relatively abundant sites within <span class="hlt">olivine</span> that are not saturated by 1680 <span class="hlt">bar</span> PHe or ~5×10-9 mol g-1. Large radius vacancies, i.e. oxygen vacancies, are energetically favorable sites for noble gas dissolution (3). However, oxygen vacancies are not abundant enough in San Carlos <span class="hlt">olivine</span> to account for this solubility (e.g. 4), suggesting the 3x10-12 mol g-1 <span class="hlt">bar</span>-1 Henry's coefficient is associated with interstitial dissolution of helium. Helium was dissolved into <span class="hlt">olivine</span> using an externally heated pressure vessel (Brown University). The starting materials were prepared by cutting gem-quality San Carlos <span class="hlt">olivine</span> (~Fo90) into small blocks (~4×2×1 mm) using a diamond wafering blade saw and polishing with alumina slurries and colloidal silica. Analysis was completed by laser ablation-mass spectrometry using a 193 nm excimer laser and a MAP 215-50 specifically tuned for He (Open University, UK). Laser ablation pit depth varied from 2 to 40 μm, and no correlation between pit depth and [He] is observed after accounting for variations PHe across the different experiments. This lack of correlation indicates a close approach to equilibrium was achieved over the experimental durations. Two analyses yielded spuriously high [He] (>3 std. dev. from the population mean, n = 85), and these analyses were not used to calculate Henry's coefficients. The two spuriously high analyses, in combination with the right skew of Henry's coefficients calculated from individual data points, suggests gem-quality San Carlos <span class="hlt">olivine</span> contains volumes with anomalously high helium solubility. The nature of these volumes is currently under investigation. However, despite their presence, helium is still highly incompatible in <span class="hlt">olivine</span> during partial melting. [1] Lux GCA 1987 [2] Heber et al. GCA 2007 [3] Shcheka & Keppler Nature 2012 [4] Walker et al. PEPI 2009</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984ChJSS...4..173Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984ChJSS...4..173Y"><span id="translatedtitle">Determination of silicon in meteoritic <span class="hlt">chondrules</span> and its significance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yi, W.-X.; Ouyang, Z.-Y.; Hu, G.-H.; Zhong, H.-H.; Xu, H.-Q.</p> <p>1984-04-01</p> <p>The silicon abundances in 20 <span class="hlt">chondrules</span> from the Jilin, Xin Yang, Boxian, and Dontai meteorites and their whole rock samples were determined by 14 MeV neutron activation analysis. The silicon abundances were enriched in <span class="hlt">chondrules</span> compared to whole chondrites. A systematic increase in the silicon abundance of whole chondrites with E, H, L, LL was observed, as was a systematic increase in the silicon abundance of nonmagnetic <span class="hlt">chondrules</span> from ordinary chondrites with H, L, LL. The results indicate indirectly that <span class="hlt">chondrule</span> formation occurred earlier than matrix formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950012906&hterms=CAIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCAIS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950012906&hterms=CAIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCAIS"><span id="translatedtitle">Formation of <span class="hlt">chondrules</span> and CAIs by nebular processes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Palme, H.</p> <p>1994-01-01</p> <p><span class="hlt">Chondrules</span> are essential components of most chondritic meteorites. Carbonaceous chondrites, with the exception of CI chondrites, contain 30-50% <span class="hlt">chondrules</span>, ordinary and enstatite chondrites even more. A better understanding of <span class="hlt">chondrule</span> formation will therefore lead to an improved understanding of the origin of meteorites. Most studies of <span class="hlt">chondrules</span> are, however, concerned with their texture and mineralogy. As <span class="hlt">chondrules</span>, by definition, passed through a molten stage, their present texture and mineralogy can only provide information on conditions of crystallization from a melt and the subsequent solid-state cooling history. Information concerning <span class="hlt">chondrule</span> formation is contained in their chemical and isotopic composition. The two most important observations relevant to the chemistry of the <span class="hlt">chondrules</span> are their generally low Fe content and the large compositional variability of <span class="hlt">chondrules</span> from a single meteorite, reflected in major variations of Mg/Si ratios, of Al and other refractory element abundances, total Fe, metal (Fe, Ni), and sulfide. This large compositional variability is surprising considering the uniform and nearly solar composition of bulk chondrites, which, in some cases, consist of more than 90% of <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19820048224&hterms=NRM&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DNRM','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19820048224&hterms=NRM&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DNRM"><span id="translatedtitle">Stable NRM and mineralogy in Allende - <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wasilewski, P. J.; Saralker, C.</p> <p>1982-01-01</p> <p>The main objective of the present investigation is related to a description of the magnetic and mineralogic contrasts between <span class="hlt">chondrules</span> which have a natural remanent magnetization (NRM) vector that is ultrastable during alternating field (AF) demagnetization, and those which have unstable NRM vectors when subjected to the same treatment. The results presented in the present investigation together with new magnetic results from Allende listed in a summary provided by Wasilewski (1981) are used as a basis to argue that the stable NRM in Allende was acquired during a sulfidation event. Attention is given to magnetic phases in Allende, experimental results obtained in magnetic studies conducted with 20 <span class="hlt">chondrules</span>, and a magnetization model for Allende.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993Metic..28R.398M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993Metic..28R.398M"><span id="translatedtitle">In Situ Investigation of Preirradiated <span class="hlt">Olivines</span> in CM Chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Metzler, K.</p> <p>1993-07-01</p> <p>Most CM chondrites are breccias that contain fragments of primary rock representing densely packed agglomerates of <span class="hlt">chondrules</span>, CAIs, etc., all of which are mantled by thick layers of fine-grained mineral dust [1]. These dust mantles seem to be the result of dust sampling by the various components during their isolated existence in the solar nebula prior to the formation of the CM parent body [1]. Metzler et al. [1] concluded that these rock fragments are well-preserved remnants of the freshly accreted CM parent body(ies). There is an opposing hypothesis that favors an origin of the dust mantles in an active regolith on the CM parent body [e.g., 2]. A list of arguments against the latter view is given by Metzler et al. [1], including a hint at the absence of solar-wind-implanted gases in dust mantles and in fragments of primary rock. In analogy to brecciated ordinary chondrites and lunar breccias, the most probable residence of the solar gases in CM chondrites is their clastic matrix. The same holds for track-rich <span class="hlt">olivines</span> that were observed in CM chondrites. The occurrence of these grains in the clastic matrix and their absence in the primary rock would give an additional argument for the idea of a dust mantle origin in the solar nebula rather than in a planetary regolith. To answer this important question, mosaics of backscattered electron images of several large polished thin sections of Murchison and Cold Bokkeveld were prepared. The thin sections (1.5-5 cm^2 each) were etched in a WN solution [3] for about 4 hr to reveal the heavy ion tracks in <span class="hlt">olivines</span>. Results: The background GCR track density produced during meteoroid transit is on the order of 10^4 tracks/cm^2, as was previously observed by [4]. Following the definition given by Goswami and Lal [4], <span class="hlt">olivines</span> with track densities >10^5 tracks/cm^2 were classified as preirradiated grains and were found in both meteorites in a very small quantity. In both meteorites, 39 preirradiated isolated <span class="hlt">olivine</span> grains were found in the clastic matrix, whereas the investigated fragments of primary rock do not contain preirradiated <span class="hlt">olivines</span>. In Murchison about 1.8% (15 out of 850 investigated grains) of the isolated <span class="hlt">olivines</span> in the clastic matrix show high track densities in the range between 1.9 x 10^6 and >5 x 10^7, comparable to the results of Goswami and co-workers [4,5]. Both Fe-poor and Fe-rich <span class="hlt">olivines</span> with grain sizes between 40 and 710 micrometers were found to be preirradiated. Track gradients were found in 33% of these <span class="hlt">olivines</span>, which is very similar to the values obtained by Goswami and Lal [4] and identical to those obtained by MacDougall and Phinney [6]. About 0.4% (2 out of 530) of the investigated <span class="hlt">olivine</span>-bearing <span class="hlt">chondrules</span> and <span class="hlt">chondrule</span> fragments are preirradiated. In the case of Cold Bokkeveld, 3.7% (24 out of 650) of the isolated <span class="hlt">olivines</span> show high track densities. Thirteen of these 24 grains were found to be concentrated in a distinct inclusion (1 x 4 mm) that is characterized by its elongated appearence and clastic fabric. The track densities of its preirradiated <span class="hlt">olivines</span> show a very narrow range, indicating a common irradiation history of these grains. The petrography of this inclusion is currently under investigation. Conclusions: Track-rich (preirradiated) <span class="hlt">olivines</span> in CM chondrites occur exclusively in the clastic matrix of these meteorites, comparable to observations in brecciated ordinary chondrites. Fragments of primary rock in CM chondrites do not contain solar-wind-implanted gases [1] or preirradiated grains. This confirms the view that the dust mantles around various components of these rocks are the products of dust accretion in the solar nebula rather than of regolith processes on the parent body surface. References: [1] Metzler K. et al. (1992) GCA, 56, 2873. [2] Kerridge J. (1992) personal communication. [3] Krishnaswami S. et al. (1971) Science, 174, 287. [4] Goswami J. N. and Lal D.(1979) Icarus, 40, 510. [5] Goswami J. N. and MacDougall J. D. (1983) Proc. LPSC 13th, in JGR, 88, A755. [6] MacDougall J. D. and Phinney D. (1977) Proc. LSC 8th, 293.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5556116','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5556116"><span id="translatedtitle">Constraints on <span class="hlt">chondrule</span> origin from petrology of isotopically characterized <span class="hlt">chondrules</span> in the Allende meteorite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mcsween, H.Y. Jr.</p> <p>1985-09-01</p> <p>The petrologic and chemical properties of the ferromagnesian <span class="hlt">chondrules</span> in the Allende carbonaceous chondrite were examined in terms of the isotopic composition and the correlations between isotopic patterns. Areas of thin sections were studied with a SEM and bulk chemical fractions of 12 constituents were quantified to calculate correlations with petrologic features. A possible correlation between (CaO + Al2O2)/MgO and oxygen isotopes imply the formation of oxygen isotopic compositions in the <span class="hlt">chondrules</span> by exchanges between isotopically heavy nebular gases and O-16 enriched solids. Different rates of gaseous exchange occurred with the various types of <span class="hlt">chondrules</span>. Factors which may have controlled the exchanges are discussed. 21 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050174600','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050174600"><span id="translatedtitle">Porphyritic <span class="hlt">Olivine</span>-Pyroxene Clast in Kaidun: First Discovery of an Ordinary Chondrite Clast?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mikouchi, T.; Makishima, J.; Koizumi, E.; Zolensky, M. E.</p> <p>2005-01-01</p> <p>Kaidun is an enigmatic meteorite showing a micro-brecciated texture composed of variable kinds of lithic clasts and mineral fragments. The constituent components range from primitive chondritic materials to differentiated achondritic materials, and thus believed to have originated from a large parent body accumulating materials from many different bodies in the asteroid belt. One of the interesting observations is that no ordinary chondrite component has been found yet, although C and E chondrites components are abundant. In this abstract, we report mineralogy of the clast (Kaidun #15415- 01.3.13a) showing a porphyritic <span class="hlt">olivine</span>-pyroxene <span class="hlt">chondrule</span>-like texture similar to those found in unequilibrated ordinary chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.142..240F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.142..240F"><span id="translatedtitle"><span class="hlt">Olivine</span> in terminal particles of Stardust aerogel tracks and analogous grains in chondrite matrix</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frank, David R.; Zolensky, Michael E.; Le, Loan</p> <p>2014-10-01</p> <p>The dearth of both major and minor element analyses of anhydrous silicate phases in chondrite matrix has thus far hindered their comparison to the Wild 2 samples. We present 68 analyses of <span class="hlt">olivine</span> (Fa0-97) in the coarse-grained terminal particles of Stardust aerogel tracks and a comprehensive dataset (>103 analyses) of analogous <span class="hlt">olivine</span> grains (5-30 μm) isolated in CI, CM, CR, CH, CO, CV3-oxidized, CV3-reduced, C3-ungrouped (Acfer 094 and Ningqiang), L/LL 3.0-4, EH3, and Kakangari chondrite matrix. These compositions reveal that Wild 2 likely accreted a diverse assortment of material that was radially transported from various carbonaceous and ordinary chondrite-forming regions. The Wild 2 <span class="hlt">olivine</span> includes amoeboid <span class="hlt">olivine</span> aggregates (AOAs), refractory forsterite, type I and type II <span class="hlt">chondrule</span> fragments and/or microchondrules, and rare relict grain compositions. In addition, we have identified one terminal particle that has no known compositional analog in the meteorite record and may be a signature of low-temperature, aqueous processing in the Kuiper Belt. The generally low Cr content of FeO-rich <span class="hlt">olivine</span> in the Stardust samples indicates that they underwent mild thermal metamorphism, akin to a petrologic grade of 3.05-3.15.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5100445','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5100445"><span id="translatedtitle">Titanium isotopic anomalies in <span class="hlt">chondrules</span> from carbonaceous chondrites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Niemeyer, S.</p> <p>1988-02-01</p> <p>Isotopic analyses of Ti from <span class="hlt">chondrules</span> of carbonaceous chondrites reveal that Ti anomalies are present; anomalies are detected only at /sup 50/Ti. For a suite of eight Allende <span class="hlt">chondrules</span>, four give well-resolved anomalies which range from a /sup 50/Ti deficit of two epsilon-units to a /sup 50/Ti excess of nine epsilon-units. No clear link is evident between the structure or composition of the <span class="hlt">chondrules</span> and the Ti anomalies. However, the <span class="hlt">chondrule</span> with by far the largest Ti isotopic anomaly is also Al-rich. Yet the absence of a strict correlation between the Ca, Al, and Ti contents and the Ti anomalies, together with the similarity of the /sup 50/Ti excess for the one <span class="hlt">chondrule</span> to that of most Ca-Al-rich inclusions (CAIs), indicate that the relation between degree of refractory enrichment and the magnitude of Ti isotopic anomalies is not a simple one. Single <span class="hlt">chondrules</span> from Murchison, Kaidun, and Kakangari all fail to exhibit a well-resolved anomaly, although in the latter two the single analysis of each precludes resolving anomalies of less than three epsilon-units. These observations support the view that the Ti isotopic diversity in <span class="hlt">chondrules</span> in an inherited feature from their precursor assemblages of dust. Models which envision similar precursors for both <span class="hlt">chondrules</span> and matrix are consistent with the Ti isotopic data. But at least two distinct solid-matter reservoirs are required for the Allende <span class="hlt">chondrules</span> alone, which underscores the diversity in the nebular dust. These Ti anomalies also caution that more than one dust isotopic component may be necessary to account fully for the oxygen isotopic variations in <span class="hlt">chondrules</span>. The Ti anomalies in <span class="hlt">chondrules</span> argue strongly against models which ascribe the Ti anomalies in CAIs to unique features of their evolution; instead, heterogeneities were more common in the nebular dust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011M%26PS...46..989R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011M%26PS...46..989R"><span id="translatedtitle">Cosmogenic helium and neon in individual <span class="hlt">chondrules</span> from Allende and Murchison: Implications for the precompaction exposure history of <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roth, A. S. G.; Baur, H.; Heber, V. S.; Reusser, E.; Wieler, R.</p> <p>2011-07-01</p> <p>We analyzed cosmogenic He and Ne in more than 60 individual <span class="hlt">chondrules</span> separated from small chips from the carbonaceous chondrites Allende and Murchison. The goal of this work is to search for evidence of an exposure of <span class="hlt">chondrules</span> to energetic particles—either solar or galactic—prior to final compaction of their host chondrites and prior to the exposure of the meteoroids to galactic cosmic rays (GCR) on their way to Earth. Production rates of GCR-produced He and Ne are calculated for each <span class="hlt">chondrule</span> based on major element composition and a physical model of cosmogenic nuclide production in carbonaceous chondrites (Leya and Masarik 2009). All studied <span class="hlt">chondrules</span> in Allende show nominal exposure ages identical to each other within uncertainties of a few hundred thousand years. Allende <span class="hlt">chondrules</span> therefore show no signs of a precompaction exposure. The majority of the Murchison <span class="hlt">chondrules</span> (the "normal" <span class="hlt">chondrules</span>) also have nominal exposure ages identical within a few hundred thousand years. However, roughly 20% of the studied Murchison <span class="hlt">chondrules</span> (the "pre-exposed" <span class="hlt">chondrules</span>) contain considerably or even much higher concentrations of cosmogenic noble gases than the normal <span class="hlt">chondrules</span>, equivalent to exposure ages to GCR at present-day fluxes in a 4π irradiation of up to about 30 Myr. The data do not allow to firmly conclude whether these excesses were acquired by an exposure of the pre-exposed <span class="hlt">chondrules</span> to an early intense flux of solar energetic particles (solar cosmic rays) or rather by an exposure to GCR in the regolith of the Murchison parent asteroid. However, we prefer the latter explanation. Two major reasons are the GCR-like isotopic composition of the excess Ne and the distribution of solar flare tracks in Murchison samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880035733&hterms=radiochemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dradiochemistry','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880035733&hterms=radiochemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dradiochemistry"><span id="translatedtitle">Compositional evidence regarding the origins of rims on Semarkona <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grossman, Jeffrey N.; Wasson, John T.</p> <p>1987-01-01</p> <p>This paper presents results on neutron activation analyses of the interiors and the abraded surfaces of seven <span class="hlt">chondrules</span> from Semarkona chondrite. The results showed that six of seven <span class="hlt">chondrule</span> rims have enhanced contents of siderophiles and chalcophiles relative to <span class="hlt">chondrule</span> interiors, indicating that, during <span class="hlt">chondrule</span> formation, metal/sulfide melts migrated to the exterior of the <span class="hlt">chondrule</span>; later reheating caused this material to spread out into fine-grained rim material. For nonvolatile elements, the lithophile and siderophile element abundance patterns in the surfaces are generally similar to those in the corresponding interiors, indicating that the surface and the interior metal might have originated from a single precursor. The volatile to moderately-volatile elements K, As, and Zn tend to be enriched in the surface, compared with other elements of similar mineral affinity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988GeCoA..52..309N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988GeCoA..52..309N"><span id="translatedtitle">Titanium isotopic anomalies in <span class="hlt">chondrules</span> from carbonaceous chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niemeyer, S.</p> <p>1988-02-01</p> <p>Isotopic analyses of Ti from a suite of eight Allende <span class="hlt">chondrules</span> were conducted to determine whether any relationship exists between the composition and structure of a <span class="hlt">chondrule</span> and the Ti isotopic patterns. Four of the eight <span class="hlt">chondrules</span> displayed well-resolved anomalies with respect to Ti-50/Ti-46 ratio, which ranged from a Ti-50 deficit of two epsilon-units to a T-50 excess of nine epsilon-units. No clear link was found between the structure of the <span class="hlt">chondrules</span> and the Ti anomalies (although the <span class="hlt">chondrule</span> with by far the largest Ti isotopic anomaly was also Al-rich, suggesting that there might exist a complicated relationship between the degree of refractory enrichment and the magnitude of Ti isotopic anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22037092','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22037092"><span id="translatedtitle"><span class="hlt">CHONDRULE</span> FORMATION IN BOW SHOCKS AROUND ECCENTRIC PLANETARY EMBRYOS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Morris, Melissa A.; Desch, Steven J.; Athanassiadou, Themis; Boley, Aaron C.</p> <p>2012-06-10</p> <p>Recent isotopic studies of Martian meteorites by Dauphas and Pourmand have established that large ({approx}3000 km radius) planetary embryos existed in the solar nebula at the same time that <span class="hlt">chondrules</span>-millimeter-sized igneous inclusions found in meteorites-were forming. We model the formation of <span class="hlt">chondrules</span> by passage through bow shocks around such a planetary embryo on an eccentric orbit. We numerically model the hydrodynamics of the flow and find that such large bodies retain an atmosphere with Kelvin-Helmholtz instabilities allowing mixing of this atmosphere with the gas and particles flowing past the embryo. We calculate the trajectories of <span class="hlt">chondrules</span> flowing past the body and find that they are not accreted by the protoplanet, but may instead flow through volatiles outgassed from the planet's magma ocean. In contrast, <span class="hlt">chondrules</span> are accreted onto smaller planetesimals. We calculate the thermal histories of <span class="hlt">chondrules</span> passing through the bow shock. We find that peak temperatures and cooling rates are consistent with the formation of the dominant, porphyritic texture of most <span class="hlt">chondrules</span>, assuming a modest enhancement above the likely solar nebula average value of <span class="hlt">chondrule</span> densities (by a factor of 10), attributable to settling of <span class="hlt">chondrule</span> precursors to the midplane of the disk or turbulent concentration. We calculate the rate at which a planetary embryo's eccentricity is damped and conclude that a single planetary embryo scattered into an eccentric orbit can, over {approx}10{sup 5} years, produce {approx}10{sup 24} g of <span class="hlt">chondrules</span>. In principle, a small number (1-10) of eccentric planetary embryos can melt the observed mass of <span class="hlt">chondrules</span> in a manner consistent with all known constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014M%26PS...49.1456D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014M%26PS...49.1456D"><span id="translatedtitle">Oxygen isotope and chemical compositions of magnetite and <span class="hlt">olivine</span> in the anomalous CK3 Watson 002 and ungrouped Asuka-881595 carbonaceous chondrites: Effects of parent body metamorphism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davidson, Jemma; Krot, Alexander N.; Nagashima, Kazuhide; Hellebrand, Eric; Lauretta, Dante S.</p> <p>2014-08-01</p> <p>We report in situ O isotope and chemical compositions of magnetite and <span class="hlt">olivine</span> in <span class="hlt">chondrules</span> of the carbonaceous chondrites Watson-002 (anomalous CK3) and Asuka (A)-881595 (ungrouped C3). Magnetite in Watson-002 occurs as inclusion-free subhedral grains and rounded inclusion-bearing porous grains replacing Fe,Ni-metal. In A-881595, magnetite is almost entirely inclusion-free and coexists with Ni-rich sulfide and less abundant Ni-poor metal. Oxygen isotope compositions of <span class="hlt">chondrule</span> <span class="hlt">olivine</span> in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of Δ17O values (from approximately -3 to -6‰). One <span class="hlt">chondrule</span> from each sample was found to contain O isotopically heterogeneous <span class="hlt">olivine</span>, probably relict grains. Oxygen isotope compositions of magnetite in A-881595 plot along a mass-dependent fractionation line with a slope of 0.5 and show a range of Δ17O values from -2.4‰ to -1.1‰. Oxygen isotope compositions of magnetite in Watson-002 cluster near the CCAM line and a Δ17O value of -4.0‰ to -2.9‰. These observations indicate that magnetite and <span class="hlt">chondrule</span> <span class="hlt">olivine</span> are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre-existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in Δ17O values of magnetite between Watson-002 and A-881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060049099&hterms=sample+types&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsample%2Btypes','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060049099&hterms=sample+types&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsample%2Btypes"><span id="translatedtitle">Oxygen-isotopic Compositions of Low-FeO relicts in High-FeO Host <span class="hlt">Chondrules</span> in Acfer 094, a Type 3.0 Carbonaceous Chondrite Closely Related to CM</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.; Kunihiro, Tak; Wasson, John T.</p> <p>2006-01-01</p> <p>With one exception, the low-FeO relict <span class="hlt">olivine</span> grains within high-FeO porphyritic <span class="hlt">chondrules</span> in the type 3.0 Acfer 094 carbonaceous chondrite have DELTA O-17 ( = delta O-17 - 0.52 X delta O-18) values that are substantially more negative than those of the high-FeO <span class="hlt">olivine</span> host materials. These results are similar to observations made earlier on <span class="hlt">chondrules</span> in C03.0 chondrites and are consistent with two independent models: (1) Nebular solids evolved from low-FeO, low-DELTA O-17 compositions towards high-FeO, more positive DELTA O-17 compositions; and (2) the range of compositions resulted from the mixing of two independently formed components. The two models predict different trajectories on a DELTA O-17 vs. log Fe/Mg (<span class="hlt">olivine</span>) diagram, but our sample set has too few values at intermediate Fe/Mg ratios to yield a definitive answer. Published data showing that Acfer 094 has higher volatile contents than CO chondrites suggest a closer link to CM chondrites. This is consistent with the high modal matrix abundance in Acfer 094 (49 vol.%). Acfer 094 may be an unaltered CM chondrite or an exceptionally matrix-rich CO chondrite. <span class="hlt">Chondrules</span> in Acfer 094 and in CO and CM carbonaceous chondrites appear to sample the same population. Textural differences between Acfer 094 and CM chondrites are largely attributable to the high degree of hydrothermal alteration that the CM chondrites experienced in an asteroidal setting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50.1595R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50.1595R"><span id="translatedtitle">An American on Paris: Extent of aqueous alteration of a CM chondrite and the petrography of its refractory and amoeboid <span class="hlt">olivine</span> inclusions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rubin, Alan E.</p> <p>2015-09-01</p> <p>Paris is the least aqueously altered CM chondrite identified to date, classified as subtype 2.7; however, literature data indicate that some regions of this apparently brecciated meteorite may be subtype 2.9. The suite of CAIs in Paris includes 19% spinel-pyroxene inclusions, 19% spinel inclusions, 8% spinel-pyroxene-<span class="hlt">olivine</span> inclusions, 43% pyroxene inclusions, 8% pyroxene-<span class="hlt">olivine</span> inclusions, and 3% hibonite-bearing inclusions. Both simple and complex inclusions are present; some have nodular, banded, or distended structures. No melilite was identified in any of the inclusions in the present suite, but other recent studies have found a few rare occurrences of melilite in Paris CAIs. Because melilite is highly susceptible to aqueous alteration, it is likely that it was mostly destroyed during early-stage parent-body alteration. Two of the CAIs in this study are part of compound CAI-<span class="hlt">chondrule</span> objects. Their presence suggests that there were transient heating events (probably associated with <span class="hlt">chondrule</span> formation) in the nebula after <span class="hlt">chondrules</span> and CAIs were admixed. Also present in Paris are a few amoeboid <span class="hlt">olivine</span> inclusions (AOI) consisting of relatively coarse forsterite rims surrounding fine-grained, porous zones containing diopside and anorthite. The interior regions of the AOIs may represent fine-grained rimless CAIs that were incorporated into highly porous forsterite-rich dustballs. These assemblages were heated by an energy pulse that collapsed and coarsened their rims, but failed to melt their interiors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930028355&hterms=Cobalt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DCobalt','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930028355&hterms=Cobalt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DCobalt"><span id="translatedtitle">The effect of oxygen fugacity on the partitioning of nickel and cobalt between <span class="hlt">olivine</span>, silicate melt, and metal</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ehlers, Karin; Grove, Timothy L.; Sisson, Thomas W.; Recca, Steven I.; Zervas, Deborah A.</p> <p>1992-01-01</p> <p>The effect of oxygen fugacity, f(O2), on the partitioning behavior of Ni and Co between <span class="hlt">olivine</span>, silicate melt, and metal was investigated in the CaO-MgO-Al2O3-SiO2-FeO-Na2O system, an analogue of a <span class="hlt">chondrule</span> composition from an ordinary chondrite. The conditions were 1350 C and 1 atm, with values of f(O2) varying between 10 exp -5.5 and 10 exp -12.6 atm (i.e., the f(O2) range relevant for crystal/liquid processes in terrestrial planets and meteorite parent bodies). Results of chemical analysis showed that the values of the Ni and Co partitioning coefficients begin to decrease at values of f(O2) that are about 3.9 log units below the nickel-nickel oxide and cobalt-cobalt oxide buffers, respectively, near the metal saturation for the <span class="hlt">chondrule</span> analogue composition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050165560','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050165560"><span id="translatedtitle"><span class="hlt">Chondrules</span> and Isolated Grains in the Fountain Hills Bencubbinite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>LaBlue, A. R.; Lauretta, D. S.; Killgore, M.</p> <p>2004-01-01</p> <p>The Fountain Hills (FH) meteorite was recently classified as a Bencubbin-like (CB(sub a)) chondrite, which are part of the CR clan [1]. The FH O-isotopic composition is indistinguishable from CB(sub a) chondrites. Metal and silicate compositions are consistent with the CB(sub a) classification. Significant differences between FH and the other CB(sub a) chondrites were noted. These include abundant porphyritic <span class="hlt">chondrules</span> and complete lack of sulfide minerals. We are furthering this investigation by analyzing silicate <span class="hlt">chondrules</span> and isolated grains in FH to determine more about its composition, thermal history, and implications for <span class="hlt">chondrule</span> formation in the early solar system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19830057375&hterms=Albuquerque+al&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAlbuquerque%2Bal.','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19830057375&hterms=Albuquerque+al&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAlbuquerque%2Bal."><span id="translatedtitle">Ca-Al-rich <span class="hlt">chondrules</span> and inclusions in ordinary chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bischoff, A.; Keil, K.</p> <p>1983-01-01</p> <p>Ca-Al-rich objects, hitherto mostly found in carbonaceous chondrites, are shown to be widespread, albeit rare, constituents of type 3 ordinary chondrites. Widespread occurrence and textural similarities of Ca-Al-rich <span class="hlt">chondrules</span> to common, Mg-Fe-rich <span class="hlt">chondrules</span> suggest that they formed by related processes. It is suggested in this article that Ca-Al-rich <span class="hlt">chondrules</span> were formed by total melting and crystallization of heterogeneous, submillimeter- to submillimeter-sized dustballs made up of mixtures of high-temperature, Ca-Al-rich and lower-temperature, Na-K-rich components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGP51A1306L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGP51A1306L"><span id="translatedtitle">Rock magnetic properties of dusty <span class="hlt">olivine</span>: comparison and calibration of non-heating paleointensity methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lappe, S. L.; Harrison, R. J.; Feinberg, J. M.</p> <p>2012-12-01</p> <p>The mechanism of <span class="hlt">chondrule</span> formation is an important outstanding question in cosmochemistry. Magnetic signals recorded by Fe-Ni nanoparticles in <span class="hlt">chondrules</span> could carry clues to their origin. Recently, research in this area has focused on 'dusty <span class="hlt">olivine</span>' in ordinary chondrites as potential carriers of pre-accretionary remanence. Dusty <span class="hlt">olivine</span> is characterised by the presence of sub-micron Fe-Ni inclusions within the <span class="hlt">olivine</span> host. These metal particles form via subsolidus reduction of the <span class="hlt">olivine</span> during <span class="hlt">chondrule</span> formation and are thought to be protected from subsequent chemical and thermal alteration by the host <span class="hlt">olivine</span>. Three sets of synthetic dusty <span class="hlt">olivines</span> have been produced, using natural <span class="hlt">olivine</span> (average Ni-content of 0.3 wt%), synthetic Ni-containing <span class="hlt">olivine</span> (0.1wt% Ni) and synthetic Ni-free <span class="hlt">olivine</span> as starting materials. The starting materials were ground to powders, packed into a 8-27 mm3 graphite crucible, heated up to 1350°C under a pure CO gas flow and kept at this temperature for 10 minutes. After this the samples were held in fixed orientation and quenched into water in a range of known magnetic fields from 0.2 mT to 1.5 mT. We present a comparison of all non-heating methods commonly used for paleointensity determination of extraterrestrial material. All samples showed uni-directional, single-component demagnetization behaviour. Saturation REM ratio (NRM/SIRM) and REMc ratio show non-linear behaviour as function of applied field and a saturation value < 1. Using the REM' method the samples showed approximately constant REM' between 100 and 150 mT AF-field. Plotting the average values for this field range again shows non-linear behaviour and a saturation value < 1. Another approach we examined to obtain calibration curves for paleointensity determination is based on ARM measurents. We also present an analysis of a new FORC-based method of paleointensity determination applied to metallic Fe-bearing samples [1, 2]. The method uses a first-order reversal curve (FORC) diagram to generate a Preisach distribution of coercivities and interaction fields within the sample and then physically models the acquisition of TRM as function of magnetic field, temperature and time using thermal relaxation theory. The comparison of observed and calculated NRM demagnetisation spectra is adversely effected by a large population of particles in the single-vortex state. Comparison of observed and calculated REM' curves, however, yields much closer agreement in the high-coercivity SD-dominated range. Calculated values of the average REM' ratio show excellent agreement with the experimental values - including the observed non-linearity of the remanence acquisition curve - suggesting that this method has the potential to reduce the uncertainties in non-heating paleointensity methods for extraterrestrial samples. [1] AR Muxworthy and D Heslop(2011) A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 1. Theoretical framework. Journal of Geophysical Research, 116, B04102, doi:10.1029/2010JB007843. [2] AR Muxworthy, D Heslop, GA Paterson, and D Michalk. A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing. Journal of Geophysical Research, 116, B04103, doi:10.1029/2010JB007844.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950012910&hterms=nebular+hypothesis&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnebular%2Bhypothesis','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950012910&hterms=nebular+hypothesis&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnebular%2Bhypothesis"><span id="translatedtitle">The circumplanetary nebular environment: A possible source region for <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sanders, I. S.</p> <p>1994-01-01</p> <p>Hypotheses for the origin of <span class="hlt">chondrules</span> fall into two broad groups: nebular and planetary. Arguments against the latter have prevailed in recent years such that, by default, the less testable nebular setting for <span class="hlt">chondrule</span> formation is now generally favored. However, the recognition in ordinary chondrites of igneous clasts that probably formed on, or in, small planetoids hints that some parent bodies were still accreting after others had evolved magmatically and lost material to space, presumably by impact. If melting of planetoids can predate accretion, could the same early melting even be related to <span class="hlt">chondrule</span> production? My affirmative response to this interesting question is expanded here in a <span class="hlt">chondrule</span>-forming scenario, which incorporates both planetary and nebular features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19740057371&hterms=Spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DSpinel','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19740057371&hterms=Spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DSpinel"><span id="translatedtitle">Reinvestigation of the <span class="hlt">olivine</span>-spinel transformation in Ni2SiO4 and the incongruent melting of Ni2SiO4 <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ma, C.-B.</p> <p>1974-01-01</p> <p>The <span class="hlt">olivine</span>-spinel transformation and the melting behavior of Ni2SiO4 were investigated over the PT ranges of 20-40 kbar, 650-1200 C, and 5-13 kbar, 1600-1700 C, respectively. It was confirmed that Ni2SiO4 <span class="hlt">olivine</span> melts incongruently at high pressures and that it is a stable phase until melting occurs. The PT slope of the incongruent melting curve is approximately 105 <span class="hlt">bars</span>/deg. The <span class="hlt">olivine</span>-spinel transformation curve was shown to be a reversible univariant curve, and could be expressed by the linear equation P(<span class="hlt">bars</span>) equals 23,300 + 11.8 x T(deg C). The transformation curve determined by Akimoto et al. (1965) is nearly parallel to that of the present work, but lies at pressures about 12% lower.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/9525858','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/9525858"><span id="translatedtitle">The formation of <span class="hlt">chondrules</span>: petrologic tests of the shock wave model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Connolly Jr HC; Love</p> <p>1998-04-01</p> <p><span class="hlt">Chondrules</span> are millimeter-sized rounded igneous rocks within chondritic meteorites. Their textures and fractionated mineral chemistries suggest that they formed by repeated, localized, brief (minutes to hours) melting of cold aggregates of mineral dust in the protoplanetary nebula. Astrophysical models of <span class="hlt">chondrule</span> formation have been unable to explain the petrologically diverse nature of chondrites. However, a nebular shock wave model for <span class="hlt">chondrule</span> formation agrees with many of the observed petrologic and geochemical properties of <span class="hlt">chondrules</span> and shows how particles within the nebula are sorted by size and how rims around <span class="hlt">chondrules</span> are formed. It also explains the volatile-rich nature of <span class="hlt">chondrule</span> rims and the chondrite matrix. PMID:9525858</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030065978','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030065978"><span id="translatedtitle">Mineralogy and Petrology of Amoeboid <span class="hlt">Olivine</span> Inclusions in CO3 Chondrites: Relationship to Parent-Body Aqueous Alteration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chizmadia, Lysa J.; Rubin, Alan E.; Wasson, John T.</p> <p>2003-01-01</p> <p>Petrographic and mineralogic studies of amoeboid <span class="hlt">olivine</span> inclusions (AOIs) in CO3 carbonaceous chondrites reveal that they are sensitive indicators of parent-body aqueous and thermal alteration. As the petrologic subtype increases from 3.0 to 3.8, forsteritic <span class="hlt">olivine</span> (Fa(sub 0-1)) is systematically converted into ferroan <span class="hlt">olivine</span> (Fa(sub 60-75)). We infer that the Fe, Si and O entered the assemblage along grain boundaries, forming ferroan <span class="hlt">olivine</span> that filled fractures and voids. As temperatures increased, Fe(+2) from the new <span class="hlt">olivine</span> exchanged with Mg(+2) from the original AOI to form diffusive haloes around low-FeO cores. Cations of Mn(+2), Ca(+2) and Cr(+3) were also mobilized. The systematic changes in AOI textures and <span class="hlt">olivine</span> compositional distributions can be used to refine the classification of CO3 chondrites into subtypes. In subtype 3.0, <span class="hlt">olivine</span> occurs as small forsterite grains (Fa(sub 0-1)), free of ferroan <span class="hlt">olivine</span>. In petrologic subtype 3.2, narrow veins of FeO-rich <span class="hlt">olivine</span> have formed at forsterite grain boundaries. With increasing alteration, these veins thicken to form zones of ferroan <span class="hlt">olivine</span> at the outside AOI margin and within the AOI interior. By subtype 3.7, there is a fairly broad <span class="hlt">olivine</span> compositional distribution in the range Fa(sub 63-70), and by subtype 3.8, no forsterite remains and the high-Fa peak has narrowed, Fa(sub 64-67). Even at this stage, there is incomplete equilibration in the chondrite as a whole (e.g., data for coarse <span class="hlt">olivine</span> grains in Isna (CO3.8) <span class="hlt">chondrules</span> and lithic clasts show a peak at Fa(sub39)). We infer that the mineral changes in A01 identified in the low petrologic types required aqueous or hydrothermal fluids whereas those in subtypes greater than or equal to 3.3 largely reflect diffusive exchange within and between mineral grains without the aid of fluids.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V14A..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V14A..07S"><span id="translatedtitle">Enhanced <span class="hlt">olivine</span> carbonation within a basalt as compared to single-phase experiments: the impact of redox and bulk composition on the dissolution kinetics of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sissmann, O.; Brunet, F.; Martinez, I.; Guyot, F. J.; Verlaguet, A.; Pinquier, Y.; Garcia, B.; Chardin, M.; Kohler, E.; Daval, D.</p> <p>2014-12-01</p> <p><span class="hlt">Olivine</span> (Mg,Fe)2SiO4, which is one of the major mineral constituents of mafic and ultramafic rocks, has an attractive potential for CO2 mineral sequestration, as it possesses a high content of carbonate-forming divalent cations and exhibits one of the highest dissolution rate amongst rock-forming minerals. This study reports drastic differences in carbonation yields between experiments performed on <span class="hlt">olivine</span>-rich basalt samples and on <span class="hlt">olivine</span> separates (a more restricted chemical system). Batch experiments were conducted in water at 150°C and pCO2 = 280 <span class="hlt">bars</span> on a Mg-rich tholeiitic basalt (9.3 wt.% MgO and 12.2 wt.% CaO), composed of <span class="hlt">olivine</span>, Ti-magnetite, plagioclase and clinopyroxene. After 45 days of reaction, 56 wt.% of the initial MgO has reacted with CO2 to form Fe-bearing magnesite (Mg0.8Fe0.2)CO3 along with minor calcium carbonates. The substantial decrease of <span class="hlt">olivine</span> content upon carbonation supports the idea that ferroan magnesite formation mainly follows from <span class="hlt">olivine</span> dissolution. In contrast, in experiments performed under similar run durations and P/T conditions with a San Carlos <span class="hlt">olivine</span> separate (47.8 wt.% MgO) of similar grain size, only 5 wt.% of the initial MgO content reacted to form Fe-bearing magnesite. The overall carbonation kinetics of the basalt is enhanced by a factor of 40. It could be accounted for by differences in chemical and textural properties of the secondary-silica layer which covers reacted <span class="hlt">olivine</span> grains in both types of sample. A TEM inspection of mineral surfaces shows that the thin amorphous silica layer (~100 nm) is porous in the case of the basalt sample and that it contains significant amounts of iron and aluminum. Thus, we propose that the composition of the <span class="hlt">olivine</span> environment itself can strongly influence the <span class="hlt">olivine</span> dissolution-carbonation process. Consequently, laboratory data obtained on <span class="hlt">olivine</span> separates might yield a conservative estimate of the true carbonation potential of <span class="hlt">olivine</span>-bearing basaltic rocks. More generally, this study questions the approach which consists in evaluating the carbonation potential of a rock based on experiments on separate minerals. It also emphasizes the impact of fO2 and potential co-injected gases on the <span class="hlt">olivine</span> dissolution-carbonation process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012LPI....43.2252L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012LPI....43.2252L"><span id="translatedtitle">Relation Between Silicate <span class="hlt">Chondrules</span> and Metal-Sulfide Nodules in EH3 Chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lehner, S. W.; Petaev, M. I.; Buseck, P. R.</p> <p>2012-03-01</p> <p>We compare the composition of sulfides in MSN and <span class="hlt">chondrules</span>, report spheroidal aggregates of silicates, silica, metal, and sulfides, and the variation in the abundance of opaque and non-opaque minerals comprising MSN and silicate <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012M%26PSA..75.5228W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012M%26PSA..75.5228W"><span id="translatedtitle">Petrology of <span class="hlt">Chondrules</span> and a Diopside-Rich Inclusion in the MAC 88136 EL3 Chondrite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weisberg, M. K.; Ebel, D. S.; Kimura, M.</p> <p>2012-09-01</p> <p>MAC 88136 (EL3) contains densely-packed enstatite-rich <span class="hlt">chondrules</span>, metal-rich nodules intergrown with silicate and an unusual large, diopside-rich <span class="hlt">chondrule</span>-like object. Petrologic and chemical features suggest hot accretion for its components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...816....8H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...816....8H"><span id="translatedtitle"><span class="hlt">Chondrule</span> Formation via Impact Jetting Triggered by Planetary Accretion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hasegawa, Yasuhiro; Wakita, Shigeru; Matsumoto, Yuji; Oshino, Shoichi</p> <p>2016-01-01</p> <p><span class="hlt">Chondrules</span> are one of the most primitive elements that can serve as a fundamental clue to the origin of our solar system. We investigate a formation scenario of <span class="hlt">chondrules</span> that involves planetesimal collisions and the resultant impact jetting. Planetesimal collisions are the main agent to regulate planetary accretion that leads to the formation of terrestrial planets and cores of gas giants. The key component of this scenario is that ejected materials can melt when the impact velocity between colliding planetesimals exceeds about 2.5 km s-1. Previous simulations have shown that the process is efficient enough to reproduce the primordial abundance of <span class="hlt">chondrules</span>. We examine this scenario carefully by performing semi-analytical calculations that are developed based on the results of direct N-body simulations. As found in the previous work, we confirm that planetesimal collisions that occur during planetary accretion can play an important role in forming <span class="hlt">chondrules</span>. This arises because protoplanet-planetesimal collisions can achieve an impact velocity of about 2.5 km s-1 or higher, as protoplanets approach the isolation mass (Mp,iso). Assuming that the ejected mass is a fraction (Fch) of the colliding planetesimals’ mass, we show that the resultant abundance of <span class="hlt">chondrules</span> is expressed well by FchMp,iso, as long as the formation of protoplanets is completed within a given disk lifetime. We perform a parameter study and examine how the abundance of <span class="hlt">chondrules</span> and the timing of their formation change. We find that the impact jetting scenario generally works reasonably well for a certain range of parameters, while more dedicated work would be needed to include other physical processes that are neglected in this work and to examine their effects on <span class="hlt">chondrule</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940030915','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940030915"><span id="translatedtitle">On the possible role of elemental carbon in the formation of reduced <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Connolly, Harold C., Jr.; Hewins, Roger H.; Ash, Richard D.; Lofgren, Gary E.; Zanda, Brigitte</p> <p>1994-01-01</p> <p>Recent experiments have been designed to produce <span class="hlt">chondrule</span> textures via flash melting while simultaneously studying the nature of <span class="hlt">chondrule</span> precursors. However, these experiments have only been concerned with silicate starting material. This is a preliminary report concerning what effects elemental carbon, when added to the silicate starting material, has on the origin of <span class="hlt">chondrules</span> produced by flash melting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010044389&hterms=Albuquerque+al&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAlbuquerque%2Bal.','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010044389&hterms=Albuquerque+al&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DAlbuquerque%2Bal."><span id="translatedtitle">Trace Element Distribution in an Al-rich <span class="hlt">Chondrule</span> from the Mokoia CV3 Chondrite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jones, R. H.; Shearer, C. K.; Schilk, A. J.</p> <p>2001-01-01</p> <p>We have studied an Al-rich <span class="hlt">chondrule</span> from Mokoia. SIMS analyses of plagioclase and pyroxene show that the bulk <span class="hlt">chondrule</span> REE pattern was originally like group II CAIs. The <span class="hlt">chondrule</span> must have had precursor material that was a condensation product. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040062235&hterms=serpentine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dserpentine','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040062235&hterms=serpentine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dserpentine"><span id="translatedtitle"><span class="hlt">Chondrule</span> Glass Alteration in Type IIA <span class="hlt">Chondrules</span> in the CR2 Chondrites EET 87770 and EET 92105: Insights into Elemental Exchange Between <span class="hlt">Chondrules</span> and Matrices</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Burger, Paul V.; Brearley, Adrian J.</p> <p>2004-01-01</p> <p>CR2 carbonaceous chondrites are a primitive group of meteorites that preserve evidence of a variety of processes that occurred in the solar nebula as well as on asteroidal parent bodies. CR2 chondrites are distinct from other carbonaceous chondrites by (among other properties) their relatively high abundance of <span class="hlt">chondrules</span> (50-60 vol. %) and Fe,Ni metal (5-8 vol. %) [1]. Like the CM2 chondrites, the CRs have been affected by aqueous alteration and according to [2] show a range of degrees of alteration. In weakly- altered CR chondrites, fine-grained matrices and <span class="hlt">chondrule</span> rims have been partially altered and <span class="hlt">chondrule</span> mesostases show evidence of incipient aqueous alteration. In these meteorites, glassy mesostasis is still common. However, some CR chondrites, (e.g. Renazzo and Al Rais) show evidence of much more extensive alteration with complete replacement of <span class="hlt">chondrule</span> mesostasis [2] by chlorite and serpentine. Although the general characteristics of alteration of the CR chondrites have been described, the details of alteration reactions in these meteorites remain unclear. In addition, the setting for aqueous alteration is poorly understood: both asteroidal and preaccretionary alteration scenarios have been proposed [2].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...794...91D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...794...91D"><span id="translatedtitle">Forming <span class="hlt">Chondrules</span> in Impact Splashes. I. Radiative Cooling Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dullemond, Cornelis Petrus; Stammler, Sebastian Markus; Johansen, Anders</p> <p>2014-10-01</p> <p>The formation of <span class="hlt">chondrules</span> is one of the oldest unsolved mysteries in meteoritics and planet formation. Recently an old idea has been revived: the idea that <span class="hlt">chondrules</span> form as a result of collisions between planetesimals in which the ejected molten material forms small droplets that solidify to become <span class="hlt">chondrules</span>. Pre-melting of the planetesimals by radioactive decay of 26Al would help produce sprays of melt even at relatively low impact velocity. In this paper we study the radiative cooling of a ballistically expanding spherical cloud of <span class="hlt">chondrule</span> droplets ejected from the impact site. We present results from numerical radiative transfer models as well as analytic approximate solutions. We find that the temperature after the start of the expansion of the cloud remains constant for a time t cool and then drops with time t approximately as T ~= T 0[(3/5)t/t cool + 2/5]-5/3 for t > t cool. The time at which this temperature drop starts t cool depends via an analytical formula on the mass of the cloud, the expansion velocity, and the size of the <span class="hlt">chondrule</span>. During the early isothermal expansion phase the density is still so high that we expect the vapor of volatile elements to saturate so that no large volatile losses are expected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21464613','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21464613"><span id="translatedtitle">THERMAL HISTORIES OF <span class="hlt">CHONDRULES</span> IN SOLAR NEBULA SHOCKS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Morris, M. A.; Desch, S. J.</p> <p>2010-10-20</p> <p><span class="hlt">Chondrules</span> are important early Solar System materials that can provide a wealth of information on conditions in the solar nebula, if their formation mechanism can be understood. The theory most consistent with observational constraints, especially thermal histories, is the so-called shock model, in which <span class="hlt">chondrules</span> were melted in solar nebula shocks. However, several problems have been identified with previous shock models. These problems all pertained to the treatment of the radiation field, namely, the input boundary condition to the radiation field, the proper treatment of the opacity of solids, and the proper treatment of molecular line cooling. In this paper, we present the results of our updated shock model, which corrects for the problems listed above. Our new hydrodynamic shock code includes a complete treatment of molecular line cooling due to H{sub 2}O. Previously, shock models including line cooling predicted <span class="hlt">chondrule</span> cooling rates exceeding 10{sup 5} K hr{sup -1}. Contrary to these expectations, we have found that the effect of line cooling is minimal; after the inclusion of line cooling, the cooling rates of <span class="hlt">chondrules</span> are 10-1000 K hr{sup -1}. The reduction in the otherwise rapid cooling rates attributable to line cooling is due to a combination of factors, including buffering due to hydrogen recombination/dissociation, high column densities of water, and backwarming. Our model demonstrates that the shock model for <span class="hlt">chondrule</span> formation remains consistent with observational constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11518959','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11518959"><span id="translatedtitle">Noble-gas-rich <span class="hlt">chondrules</span> in an enstatite meteorite.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Okazaki, R; Takaoka, N; Nagao, K; Sekiya, M; Nakamura, T</p> <p>2001-08-23</p> <p><span class="hlt">Chondrules</span> are silicate spherules that are found in abundance in the most primitive class of meteorites, the chondrites. <span class="hlt">Chondrules</span> are believed to have formed by rapid cooling of silicate melt early in the history of the Solar System, and their properties should reflect the composition of (and physical conditions in) the solar nebula at the time when the Sun and planets were forming. It is usually believed that <span class="hlt">chondrules</span> lost all their noble gases at the time of melting. Here we report the discovery of significant amounts of trapped noble gases in <span class="hlt">chondrules</span> in the enstatite chondrite Yamato-791790, which consists of highly reduced minerals. The elemental ratios 36Ar/132Xe and 84Kr/132Xe are similar to those of 'subsolar' gas, which has the highest 36Ar/132Xe ratio after that of solar-type noble gases. The most plausible explanation for the high noble-gas concentration and the characteristic elemental ratios is that solar gases were implanted into the <span class="hlt">chondrule</span> precursor material, followed by incomplete loss of the implanted gases through diffusion over time. PMID:11518959</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70014150','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70014150"><span id="translatedtitle">Compositional evidence regarding the origins of rims on Semarkona <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Grossman, J.N.; Wasson, J.T.</p> <p>1987-01-01</p> <p>The compositions of the interiors and abraded surfaces of 7 <span class="hlt">chondrules</span> from Semarkona (LL3.0) were measured by neutron activation analysis. For nonvolatile elements, the lithophile and siderophile element abundance patterns in the surfaces are generally similar to those in the corresponding interiors. Siderophile and chalcophile concentrations are much higher in the surfaces, whereas lithophile concentrations are similar in both fractions. Most of the similarities in lithophile patterns and some of the similarities in siderophile patterns between surfaces and interiors may reflect incomplete separation of the fractions in the laboratory, but for 3 or 4 <span class="hlt">chondrules</span> the siderophile resemblance is inherent, implying that the surface and interior metal formed from a single precursor assemblage. Metal and sulfide-rich <span class="hlt">chondrule</span> rims probably formed when droplets of these phases that migrated to the <span class="hlt">chondrule</span> surface during melting were reheated and incorporated into matrix-like material that had accreted onto the surface. The moderately-volatile to volatile elements K, As and Zn tend to be enriched in the surfaces compared with other elements of similar mineral affinity; both enrichments and depletions are observed for other moderately volatile elements. A small fraction of <span class="hlt">chondrules</span> experienced fractional evaporation while they were molten. ?? 1987.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22370448','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22370448"><span id="translatedtitle">Forming <span class="hlt">chondrules</span> in impact splashes. I. Radiative cooling model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dullemond, Cornelis Petrus; Stammler, Sebastian Markus; Johansen, Anders</p> <p>2014-10-10</p> <p>The formation of <span class="hlt">chondrules</span> is one of the oldest unsolved mysteries in meteoritics and planet formation. Recently an old idea has been revived: the idea that <span class="hlt">chondrules</span> form as a result of collisions between planetesimals in which the ejected molten material forms small droplets that solidify to become <span class="hlt">chondrules</span>. Pre-melting of the planetesimals by radioactive decay of {sup 26}Al would help produce sprays of melt even at relatively low impact velocity. In this paper we study the radiative cooling of a ballistically expanding spherical cloud of <span class="hlt">chondrule</span> droplets ejected from the impact site. We present results from numerical radiative transfer models as well as analytic approximate solutions. We find that the temperature after the start of the expansion of the cloud remains constant for a time t {sub cool} and then drops with time t approximately as T ≅ T {sub 0}[(3/5)t/t {sub cool} + 2/5]{sup –5/3} for t > t {sub cool}. The time at which this temperature drop starts t {sub cool} depends via an analytical formula on the mass of the cloud, the expansion velocity, and the size of the <span class="hlt">chondrule</span>. During the early isothermal expansion phase the density is still so high that we expect the vapor of volatile elements to saturate so that no large volatile losses are expected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeCoA..77...86O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeCoA..77...86O"><span id="translatedtitle"><span class="hlt">Olivine</span> reactivity with CO 2 and H 2O on a microscale: Implications for carbon sequestration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olsson, J.; Bovet, N.; Makovicky, E.; Bechgaard, K.; Balogh, Z.; Stipp, S. L. S.</p> <p>2012-01-01</p> <p>The silicate mineral <span class="hlt">olivine</span>, (Mg,Fe)2SiO4, reacts exothermally with CO2 and forms secondary minerals, including carbonates. Therefore <span class="hlt">olivine</span> reaction is a promising process for carbon sequestration, to convert carbon dioxide from the atmosphere to mineral form. The purpose of this study was (1) to explore the composition, structure and reactivity of <span class="hlt">olivine</span> surfaces during exposure to air and to water at ambient conditions, (2) to investigate the effect of elevated CO2 pressure and temperature, and (3) to identify the secondary minerals. <span class="hlt">Olivine</span> surfaces have been examined with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), before and after reaction with CO2. Experiments were carried out in pure water equilibrated with CO2 at total pressures up to 80 <span class="hlt">bars</span>, at temperatures 25 °C and 120 °C and both in the absence and presence of oxygen. New formation products appeared on the <span class="hlt">olivine</span> surface as a homogeneous layer of bumps, less than 100 nm in diameter, within hours of exposure to air. <span class="hlt">Olivine</span> crystals, exposed to water, dissolved and secondary minerals formed within days. Colonies of bacteria populated <span class="hlt">olivine</span> surfaces on samples stored in water for more than 4 days at room temperature. Loosely attached material formed on <span class="hlt">olivine</span> surfaces and could easily be scraped away with the AFM tip. A red precipitate formed when crystals where reacted at increased temperatures and CO2 partial pressures for less than 4 days. The new phases were identified as goethite, hematite, silica and carbonate minerals. <span class="hlt">Olivine</span> surfaces oxidize and iron oxides form even when oxygen is absent, suggesting hydrolysis, where water is converted to hydrogen and oxygen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996LPI....27..531H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996LPI....27..531H"><span id="translatedtitle">Volatility, <span class="hlt">Chondrules</span>, and the Composition of the Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herzberg, C. T.; Hewins, R. H.</p> <p>1996-03-01</p> <p>Despite success in modelling the gravitational accretion of planetesimals into planets, understanding the prior step in which micron-sized dust is accumulated into aggregates and incorporated into planetesimals has been problematical. Dust grains form fluffy fractal aggregates whose density remains low as they grow, so they are coupled to the turbulent gas and unable to settle to the disk midplane where planetesimal formation might then follow. Transformation of aggregates into dense <span class="hlt">chondrules</span> by melting changes their aerodynamic properties dramatically. Turbulence calculations show that <span class="hlt">chondrules</span> could have been concentrated into stagnant zones between eddies, and km-size concentrations could have fallen to the midplane so that the accretion process could proceed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15994379','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15994379"><span id="translatedtitle">Supernova <span class="hlt">olivine</span> from cometary dust.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Messenger, Scott; Keller, Lindsay P; Lauretta, Dante S</p> <p>2005-07-29</p> <p>An interplanetary dust particle contains a submicrometer crystalline silicate aggregate of probable supernova origin. The grain has a pronounced enrichment in 18O/16O (13 times the solar value) and depletions in 17O/16O (one-third solar) and 29Si/28Si (<0.8 times solar), indicative of formation from a type II supernova. The aggregate contains <span class="hlt">olivine</span> (forsterite 83) grains <100 nanometers in size, with microstructures that are consistent with minimal thermal alteration. This unusually iron-rich <span class="hlt">olivine</span> grain could have formed by equilibrium condensation from cooling supernova ejecta if several different nucleosynthetic zones mixed in the proper proportions. The supernova grain is also partially encased in nitrogen-15-rich organic matter that likely formed in a presolar cold molecular cloud. PMID:15994379</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20050206573&hterms=Supernova&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DSupernova','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20050206573&hterms=Supernova&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DSupernova"><span id="translatedtitle">Supernova <span class="hlt">olivine</span> from cometary dust</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Messenger, Scott; Keller, Lindsay P.; Lauretta, Dante S.</p> <p>2005-01-01</p> <p>An interplanetary dust particle contains a submicrometer crystalline silicate aggregate of probable supernova origin. The grain has a pronounced enrichment in 18O/16O (13 times the solar value) and depletions in 17O/16O (one-third solar) and 29Si/28Si (<0.8 times solar), indicative of formation from a type II supernova. The aggregate contains <span class="hlt">olivine</span> (forsterite 83) grains <100 nanometers in size, with microstructures that are consistent with minimal thermal alteration. This unusually iron-rich <span class="hlt">olivine</span> grain could have formed by equilibrium condensation from cooling supernova ejecta if several different nucleosynthetic zones mixed in the proper proportions. The supernova grain is also partially encased in nitrogen-15-rich organic matter that likely formed in a presolar cold molecular cloud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1007079','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1007079"><span id="translatedtitle">Shape, metal abundance, chemistry, and origin of <span class="hlt">chondrules</span> in the Renazzo (CR) chondrite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ebel, D.S.; Weisberg, M.K.; Hertz, J.; Campbell, A.J.</p> <p>2009-03-31</p> <p>We used synchrotron X-ray microtomography to image in 3-dimensions (3D) eight whole <span class="hlt">chondrules</span> in a {approx}1 cm{sup 3} piece of the Renazzo (CR) chondrite at {approx}17 {micro}m per volume element (voxel) edge. We report the first volumetric (3D) measurement of metal/silicate ratios in <span class="hlt">chondrules</span> and quantify indices of <span class="hlt">chondrule</span> sphericity. Volumetric metal abundances in whole <span class="hlt">chondrules</span> range from 1 to 37 volume % in 8 measured <span class="hlt">chondrules</span> and by inspection in tomography data. We show that metal abundances and metal grain locations in individual <span class="hlt">chondrules</span> cannot be reliably obtained from single random 2D sections. Samples were physically cut to intersect representative <span class="hlt">chondrules</span> multiple times and to verify 3D data. Detailed 2D chemical analysis combined with 3D data yield highly variable whole-<span class="hlt">chondrule</span> Mg/Si ratios with a supra-chondritic mean value, yet the chemically diverse, independently formed <span class="hlt">chondrules</span> are mutually complementary in preserving chondritic (solar) Fe/Si ratios in the aggregate CR chondrite. These results are consistent with localized <span class="hlt">chondrule</span> formation and rapid accretion resulting in <span class="hlt">chondrule</span> + matrix aggregates (meteorite parent bodies) that preserve the bulk chondritic composition of source regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950012874','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950012874"><span id="translatedtitle">Papers presented to the Conference on <span class="hlt">Chondrules</span> and the Protoplanetary Disk</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1994-01-01</p> <p>The following topics are covered in the presented papers: (1) producing <span class="hlt">chondrules</span>; (2) carbons, CAI's, and <span class="hlt">chondrules</span>; (3) large scale processes in the solar nebula; (4) <span class="hlt">chondrule</span>-matrix relationships in chondritic meteorites; (5) overview of nebula models; (6) constraints placed on the nature of <span class="hlt">chondrule</span> precursors; (7) turbulent diffusion and concentration of <span class="hlt">chondrules</span> in the protoplanetary nebula; (8) heating and cooling in the solar nebula; (9) crystallization trends of precursor pyroxene in ordinary chondrites; (10) precipitation induced vertical lightning in the protoplanetary nebula; (11) the role of <span class="hlt">chondrules</span> in nebular fractionations of volatiles and other elements; (12) astronomical observations of phenomena in disks; (13) experimental constraints on models for origins of <span class="hlt">chondrules</span>, and various other topics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1411211L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1411211L"><span id="translatedtitle">Rock magnetic properties of dusty <span class="hlt">olivine</span>: a potential carrier of pre-accretionary remanence in unequilibrated ordinary chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lappe, S. C. L. L.; Harrison, R. J.; Feinberg, J. M.</p> <p>2012-04-01</p> <p>The mechanism of <span class="hlt">chondrule</span> formation is an important outstanding question in cosmochemistry. Magnetic signals recorded by Fe-Ni nanoparticles in <span class="hlt">chondrules</span> could carry clues to their origin. Recently, research in this area has focused on 'dusty <span class="hlt">olivine</span>' grains within ordinary chondrites as potential carriers of pre-accretionary remanence. Dusty <span class="hlt">olivine</span> is characterised by the presence of sub-micron Fe-Ni inclusions within the <span class="hlt">olivine</span> host. These metal particles form via subsolidus reduction of the <span class="hlt">olivine</span> during <span class="hlt">chondrule</span> formation and are thought to be protected from subsequent chemical and thermal alteration by the host <span class="hlt">olivine</span>. Three sets of synthetic dusty <span class="hlt">olivines</span> have been produced, using natural <span class="hlt">olivine</span> (average Ni-content of 0.3 wt%), synthetic Ni-containing <span class="hlt">olivine</span> (0.1wt% Ni) and synthetic Ni-free <span class="hlt">olivine</span> as starting materials. The starting materials were ground to powders, packed into a 2-3 mm3 graphite crucible, heated up to 1350 °C under a pure CO gas flow and kept at this temperature for 10 minutes. After this the samples were held in a fixed orientation and quenched into water in a range of known magnetic fields, ranging from 0.2 mT to 1.5 mT. We present here for the first time an analysis of a new FORC-based method of paleointensity determination applied to metallic Fe-bearing samples [1, 2]. The method uses a first-order reversal curve (FORC) diagram to generate a Preisach distribution of coercivities and interaction fields within the sample and then physically models the acquisition of TRM as a function of magnetic field, temperature and time using thermal relaxation theory. The comparison of observed and calculated NRM demagnetisation spectra is adversely effected by a large population of particles in the single-vortex state. Comparison of observed and calculated REM' curves, however, yields much closer agreement in the high-coercivity SD-dominated range. Calculated values of the average REM' ratio show excellent agreement with the experimental values - including the observed non-linearity of the remanence acquisition curve - suggesting that this method has the potential to reduce the uncertainties in non-heating paleointensity methods for extraterrestrial samples. [1] AR Muxworthy and D Heslop(2011) A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 1. Theoretical framework. Journal of Geophysical Research, 116, B04102, doi:10.1029/2010JB007843. [2] AR Muxworthy, D Heslop, GA Paterson, and D Michalk. A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing. Journal of Geophysical Research, 116, B04103, doi:10.1029/2010JB007844.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.139..131K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.139..131K"><span id="translatedtitle">Amoeboid <span class="hlt">olivine</span> aggregates from CH carbonaceous chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krot, Alexander N.; Park, Changkun; Nagashima, Kazuhide</p> <p>2014-08-01</p> <p>Amoeboid <span class="hlt">olivine</span> aggregates (AOAs) in CH carbonaceous chondrites are texturally and mineralogically similar to those in other carbonaceous chondrite groups. They show no evidence for alteration and thermal metamorphism in an asteroidal setting and consist of nearly pure forsterite (Fa<3; in wt%, CaO = 0.1-0.8, Cr2O3 = 0.04-0.48; MnO < 0.5), anorthite, Al-diopside (in wt%, Al2O3 = 0.7-8.1; TiO2 < 1), Fe,Ni-metal, spinel, and, occasionally, low-Ca pyroxene (Fs1Wo2-3), and calcium-aluminum-rich inclusions (CAIs). The CAIs inside AOAs are composed of hibonite, grossite, melilite (Åk13-44), spinel, perovskite, Al,Ti-diopside (in wt%, Al2O3 up to 19.6; TiO2 up to 13.9), and anorthite. The CH AOAs, including CAIs within AOAs, have isotopically uniform 16O-rich compositions (average Δ17O = -23.4 ± 2.3‰, 2SD) and on a three-isotope oxygen diagram plot along ∼slope-1 line. The only exception is a low-Ca pyroxene-bearing AOA 1-103 that shows a range of Δ17O values, from -24‰ to -13‰. Melilite, grossite, and hibonite in four CAIs within AOAs show no evidence for radiogenic 26Mg excess (δ26Mg). In contrast, anorthite in five out of six AOAs measured has δ26Mg corresponding to the inferred initial 26Al/27Al ratio of (4.3 ± 0.7) × 10-5, (4.2 ± 0.6) × 10-5, (4.0 ± 0.3) × 10-5, (1.7 ± 0.2) × 10-5, and (3.0 ± 2.6) × 10-6. Anorthite in another AOA shows no resolvable δ26Mg excess; an upper limit on the initial 26Al/27Al ratio is 5 × 10-6. We infer that CH AOAs formed by gas-solid condensation and aggregation of the solar nebula condensates (forsterite and Fe,Ni-metal) mixed with the previously formed CAIs. Subsequently they experienced thermal annealing and possibly melting to a small degree in a 16O-rich gaseous reservoir during a brief epoch of CAI formation. The low-Ca pyroxene-bearing AOA 1-103 may have experienced incomplete melting and isotope exchange in an 16O-poor gaseous reservoir. The lack of resolvable δ26Mg excess in melilite, grossite, and hibonite in CAIs within AOAs reflects heterogeneous distribution of 26Al in the solar nebula during this epoch. The observed variations of the inferred initial 26Al/27Al ratios in anorthite of the mineralogically pristine and uniformly 16O-rich CH AOAs could have recorded (i) admixing of 26Al in the protoplanetary disk during the earliest stages of its evolution and/or (ii) closed-system Mg-isotope exchange between anorthite and Mg-rich minerals (spinel, forsterite, and Al-diopside) during subsequent prolonged (days-to-weeks) thermal annealing at high temperature (∼1100 °C) and slow cooling rates (∼0.01 K h-1) that has not affected their O-isotope systematics. The proposed thermal annealing may have occurred in an impact-generated plume invoked for the origin of non-porphyritic magnesian <span class="hlt">chondrules</span> and Fe,Ni-metal grains in CH and CB carbonaceous chondrites about 5 Myr after formation of CV CAIs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020046214&hterms=Sulfur&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DSulfur','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020046214&hterms=Sulfur&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DSulfur"><span id="translatedtitle">Sulfur Isotope Composition of Putative Primary Troilite in <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tachibana, Shogo; Huss, Gary R.</p> <p>2002-01-01</p> <p>Sulfur isotope compositions of putative primary troilites in <span class="hlt">chondrules</span> from Bishunpur were measured by ion probe. These primary troilites have the same S isotope compositions as matrix troilites and thus appear to be isotopically unfractionated. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010LPI....41.1315K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010LPI....41.1315K"><span id="translatedtitle"><span class="hlt">Chondrule</span> Tieschitz XII Revisited: Reading a Very Old Logbook</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kurat, G.; Varela, M. E.; Zinner, E.</p> <p>2010-03-01</p> <p><span class="hlt">Chondrule</span> Tieschitz XII (Tie XII) was recently re-investigated with an ion micro-probe. Tie XII perfectly fit the PLC model (Varela and Kurat, 2009) and the theoretical predictions of phase condensation in a non-canonical solar nebula [Ebel 2006].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040068145&hterms=Tokyo+Story&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTokyo%2BStory','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040068145&hterms=Tokyo+Story&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTokyo%2BStory"><span id="translatedtitle">Contemporaneous Formation of <span class="hlt">Chondrules</span> in the Al-26-MG-26 System for Ordinary and CO Chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kurahashi, E.; Kita, N. T.; Nagahara, H.; Morishita, Y.</p> <p>2004-01-01</p> <p>Chronometer using the short-lived extinct-nuclide (26)Al has been applied to <span class="hlt">chondrules</span> in order to obtain of their formation ages. Previous studies were mostly performed on Al-rich <span class="hlt">chondrules</span>, which constitute only 1% of all <span class="hlt">chondrules</span>, because of their high Al/Mg ratios. Recently, (26)Al ages of major ferromagnesian <span class="hlt">chondrules</span> in least equilibrated ordinary chondrites (OC) have been obtained. However, (26)Al ages of ferromagnesian <span class="hlt">chondrules</span> in least equilibrated carbonaceous chondrites (CC) are very limited. Particularly, age data of FeO-poor (Type I) <span class="hlt">chondrules</span> in CC have been scarcely obtained, because of their fine textures and lack of phases with high Al/Mg (>100) ratios. In order to clarify the origin and formation processes of <span class="hlt">chondrules</span>, we started systematic investigations on Type I <span class="hlt">chondrules</span> in the most pristine CC (CO3.0 Yamato-81020), by examining textures, bulk chemical compositions, (26)Al ages and oxygen isotopic compositions. We find Type I <span class="hlt">chondrules</span> in CC formed contemporaneously with ferromagnesian <span class="hlt">chondrules</span> in OC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001GeCoA..65.1337L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001GeCoA..65.1337L"><span id="translatedtitle">Opaque minerals in the matrix of the Bishunpur (LL3.1) chondrite: constraints on the <span class="hlt">chondrule</span> formation environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lauretta, Dante S.; Buseck, Peter R.; Zega, Thomas J.</p> <p>2001-04-01</p> <p>The chemistry and mineralogy of a group of opaque mineral assemblages in the matrix of the Bishunpur LL3.1 ordinary chondrite provide insight into the nebular environment in which they formed. The assemblages consist of a kamacite (Fe,Ni) core that is rimmed by troilite (FeS) and fayalite (Fe 2SiO 4). Accessory phases in the rims include silica (SiO 2), chromite (FeCr 2O 4), whitlockite (Ca 3(PO 4) 2), maricite (FeNaPO 4), magnetite (Fe 3O 4), and tetrataenite (FeNi). We suggest that the metal melted in and equilibrated with an igneous <span class="hlt">chondrule</span> under high-temperature, reducing conditions. In this environment the molten alloys incorporated varied amounts of Si, Ni, P, Cr, and Co, depending on the oxygen fugacity and temperature of the melt. Some of the metal was subsequently expelled from the <span class="hlt">chondrule</span> interiors into the surrounding nebular gas. As the temperature dropped, the alloy solidified and volatile elements corroded the metal. The main reaction products were troilite and fayalite. Thermodynamic equilibrium calculations are used to constrain the conditions under which these two phases can form simultaneously in the solar nebula. Kinetic factors are used to place a lower limit on the formation temperature. We determine that the metal corroded between 1173 and 1261 K at a total pressure in the range of 10 -5.0 to 10 -4.1 <span class="hlt">bars</span> and a dust/gas ratio of 302 to 355 x relative to solar composition. These conditions are consistent with our model that the metal corroded in a dust-rich region of the solar nebula that was cooling after a <span class="hlt">chondrule</span> formation event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.420...95D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.420...95D"><span id="translatedtitle">Multiple origins for <span class="hlt">olivine</span> at Copernicus crater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dhingra, Deepak; Pieters, Carle M.; Head, James W.</p> <p>2015-06-01</p> <p>Multiple origins for <span class="hlt">olivine</span>-bearing lithologies at Copernicus crater are recognized based on integrated analysis of data from Chandrayaan-1 Moon Mineralogy Mapper (M3), Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) and Kaguya Terrain Camera (TC). We report the diverse morphological and spectral character of previously known <span class="hlt">olivine</span>-bearing exposures as well as the new <span class="hlt">olivine</span> occurrences identified in this study. Prominent albedo differences exist between <span class="hlt">olivine</span>-bearing exposures in the central peaks and a northern wall unit (the latter being ∼40% darker). The low-albedo wall unit occurs as a linear mantling deposit and is interpreted to be of impact melt origin, in contrast with the largely unmodified nature of <span class="hlt">olivine</span>-bearing peaks. Small and localized occurrences of <span class="hlt">olivine</span>-bearing lithology have also been identified on the impact melt-rich floor, representing a third geologic setting (apart from crater wall and peaks). Recent remote sensing missions have identified <span class="hlt">olivine</span>-bearing exposures around lunar basins (e.g. Yamamoto et al., 2010; Pieters et al., 2011; Kramer et al., 2013) and at other craters (e.g. Sun and Li, 2014), renewing strong interest in its origin and provenance. A direct mantle exposure has commonly been suggested in this regard. Our detailed observations of the morphological and spectral diversity in the <span class="hlt">olivine</span>-bearing exposures at Copernicus have provided critical constraints on their origin and source regions, emphasizing multiple formation mechanisms. These findings directly impact the interpretation of <span class="hlt">olivine</span> exposures elsewhere on the Moon. <span class="hlt">Olivine</span> can occur in diverse environments including an impact melt origin, and therefore it is unlikely for all <span class="hlt">olivine</span> exposures to be direct mantle occurrences as has generally been suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.424..119B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.424..119B"><span id="translatedtitle">The ascent of kimberlite: Insights from <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brett, R. C.; Russell, J. K.; Andrews, G. D. M.; Jones, T. J.</p> <p>2015-08-01</p> <p><span class="hlt">Olivine</span> xenocrysts are ubiquitous in kimberlite deposits worldwide and derive from the disaggregation of mantle-derived peridotitic xenoliths. Here, we provide descriptions of textural features in xenocrystic <span class="hlt">olivine</span> from kimberlite deposits at the Diavik Diamond Mine, Canada and at Igwisi Hills volcano, Tanzania. We establish a relative sequence of textural events recorded by <span class="hlt">olivine</span> during magma ascent through the cratonic mantle lithosphere, including: xenolith disaggregation, decompression fracturing expressed as mineral- and fluid-inclusion-rich sealed and healed cracks, grain size and shape modification by chemical dissolution and abrasion, late-stage crystallization of overgrowths on <span class="hlt">olivine</span> xenocrysts, and lastly, mechanical milling and rounding of the <span class="hlt">olivine</span> cargo prior to emplacement. Ascent through the lithosphere operates as a "kimberlite factory" wherein progressive upward dyke propagation of the initial carbonatitic melt fractures the overlying mantle to entrain and disaggregate mantle xenoliths. Preferential assimilation of orthopyroxene (Opx) xenocrysts by the silica-undersaturated carbonatitic melt leads to deep-seated exsolution of CO2-rich fluid generating buoyancy and supporting rapid ascent. Concomitant dissolution of <span class="hlt">olivine</span> produces irregular-shaped relict grains preserved as cores to most kimberlitic <span class="hlt">olivine</span>. Multiple generations of decompression cracks in <span class="hlt">olivine</span> provide evidence for a progression in ambient fluid compositions (e.g., from carbonatitic to silicic) during ascent. Numerical modelling predicts tensile failure of xenoliths (disaggregation) and <span class="hlt">olivine</span> (cracks) over ascent distances of 2-7 km and 15-25 km, respectively, at velocities of 0.1 to >4 m s-1. Efficient assimilation of Opx during ascent results in a silica-enriched, <span class="hlt">olivine</span>-saturated kimberlitic melt (i.e. SiO2 >20 wt.%) that crystallizes overgrowths on partially digested and abraded <span class="hlt">olivine</span> xenocrysts. <span class="hlt">Olivine</span> saturation is constrained to occur at pressures <1 GPa; an absence of decompression cracks within <span class="hlt">olivine</span> overgrowths suggests depths <25 km. Late stage (<25 km) resurfacing and reshaping of <span class="hlt">olivine</span> by particle-particle milling is indicative of turbulent flow conditions within a fully fluidized, gas-charged, crystal-rich magma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS..tmp..316F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS..tmp..316F"><span id="translatedtitle">Aligned <span class="hlt">olivine</span> in the Springwater pallasite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fowler-Gerace, Neva A.; Tait, Kimberly T.; Moser, Desmond E.; Barker, Ivan; Tian, Bob Y.</p> <p>2016-04-01</p> <p>The mechanism by which <span class="hlt">olivine</span> grains became embedded within iron-nickel alloy in pallasite meteorites continues to be a matter of scientific debate. Geochemical and textural observations have failed to fully elucidate the origin and history of the <span class="hlt">olivine</span> crystals; however, little research attention has been devoted to their crystallographic orientations within the metal matrix. Using electron backscatter diffraction, we have collected crystallographic orientation data for 296 crystals within ˜65 cm2 sample surface from Springwater. Though no global crystallographic preferred orientation exists, very low misorientations are observed among [100] axes of <span class="hlt">olivine</span> crystals within specific texturally defined domains. Combined with a thorough characterization of large-scale Springwater textures, the definitively nonrandom spatial distribution of <span class="hlt">olivine</span> orientations provides clues regarding the nature of the <span class="hlt">olivine</span>'s initial formation environment as well as the sequence of events subsequent to metal incorporation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26601169','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26601169"><span id="translatedtitle">Growth of asteroids, planetary embryos, and Kuiper belt objects by <span class="hlt">chondrule</span> accretion.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Johansen, Anders; Low, Mordecai-Mark Mac; Lacerda, Pedro; Bizzarro, Martin</p> <p>2015-04-01</p> <p><span class="hlt">Chondrules</span> are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of <span class="hlt">chondrules</span> into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag-assisted accretion of <span class="hlt">chondrules</span>. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of <span class="hlt">chondrules</span> within ~3 My, forming planetary embryos up to Mars's size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of <span class="hlt">chondrules</span> consistent with chondrites. Accretion of millimeter-sized <span class="hlt">chondrules</span> and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and <span class="hlt">chondrule</span> accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of <span class="hlt">chondrules</span> destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct <span class="hlt">chondrule</span> accretion and giant impacts. PMID:26601169</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4640629','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4640629"><span id="translatedtitle">Growth of asteroids, planetary embryos, and Kuiper belt objects by <span class="hlt">chondrule</span> accretion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Johansen, Anders; Low, Mordecai-Mark Mac; Lacerda, Pedro; Bizzarro, Martin</p> <p>2015-01-01</p> <p><span class="hlt">Chondrules</span> are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of <span class="hlt">chondrules</span> into asteroidal bodies must be an important step in planet formation, but the mechanism is not understood. We show that the main growth of asteroids can result from gas drag–assisted accretion of <span class="hlt">chondrules</span>. The largest planetesimals of a population with a characteristic radius of 100 km undergo runaway accretion of <span class="hlt">chondrules</span> within ~3 My, forming planetary embryos up to Mars’s size along with smaller asteroids whose size distribution matches that of main belt asteroids. The aerodynamical accretion leads to size sorting of <span class="hlt">chondrules</span> consistent with chondrites. Accretion of millimeter-sized <span class="hlt">chondrules</span> and ice particles drives the growth of planetesimals beyond the ice line as well, but the growth time increases above the disc lifetime outside of 25 AU. The contribution of direct planetesimal accretion to the growth of both asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion and <span class="hlt">chondrule</span> accretion play more equal roles in the formation of Moon-sized embryos in the terrestrial planet formation region. These embryos are isolated from each other and accrete planetesimals only at a low rate. However, the continued accretion of <span class="hlt">chondrules</span> destabilizes the oligarchic configuration and leads to the formation of Mars-sized embryos and terrestrial planets by a combination of direct <span class="hlt">chondrule</span> accretion and giant impacts. PMID:26601169</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040084634','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040084634"><span id="translatedtitle">Turbulent Concentration of <span class="hlt">Chondrules</span>: Size Distribution and Multifractal Scaling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cuzzi, Jeffrey N.; Hogan, Robert C.; Paque, Julie M.; Dobrovolskis, Anthony R.</p> <p>1999-01-01</p> <p>Size-selective concentration of particles in 3D turbulence may be related to collection of <span class="hlt">chondrules</span> and other constituents into primitive bodies in a weakly turbulent protoplanetary nebula. In the terrestrial planet region, both the characteristic size and narrow size distribution of <span class="hlt">chondrules</span> are explained, whereas "fluffier" particles would be concentrated in lower density, or more intensely turbulent, regions of the nebula. The spatial distribution of concentrated particle density obeys multifractal scaling, suggesting a dose tie to the turbulent cascade process. This scaling behavior allows predictions of the concentration probabilities to be made in the protoplanetary nebula, which are so large (> 10(exp 3) - 10(exp 4)) that further studies must be made of the role of mass loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950060235&hterms=love&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dlove','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950060235&hterms=love&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dlove"><span id="translatedtitle">Electrical discharge heating of <span class="hlt">chondrules</span> in the solar nebula</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Love, Stanley G.; Keil, Klaus; Scott, Edward R. D.</p> <p>1995-01-01</p> <p>We present a rudimentary theoretical assessment of electrical discharge heating as a candidate mechanism for the formation of <span class="hlt">chondrules</span> in the solar nebula. The discharge model combines estimates of the properties of the nebula, a mechanism for terrestrial thunderstorm electrification, and some fundamental electrical properties of gases. Large uncertainties in the model inputs limit these calculations to order-or-magnitude accuracy. Despite the uncertainty, it is possible to estimate an upper limit to the efficiency of nebular discharges at melting millimeter-sized stony objects. We find that electrical arcs analogous to terrestrial lightning could have occurred in the nebula, but that under most conditions these discharges probably could not have melted <span class="hlt">chondrules</span>. Despite our difficulties, we believe the topic worthy of further investigation and suggest some experiments which could improve our understanding of nebular discharges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1008888','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1008888"><span id="translatedtitle">Unambiguous voids in Allende <span class="hlt">chondrules</span> and refractory inclusions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Murray, J.; Boesenberg, J.S.; Ebel, D.S.</p> <p>2003-03-26</p> <p>Void space can be caused by thin section preparation. 3-dimensional tomographic analysis, prior to sectioning, shows that several very different types of voids are abundant in Allende meteorite inclusions. Formation models are proposed for each type. Void spaces in the components of chondritic meteorites have received little attention, perhaps due to ambiguities attendant upon their very existence, and also their origin. Computer-aided microtomography allows the 3-dimensional imaging and analysis of void spaces within solid objects. Several striking examples of void spaces, apparently enclosed by solid material, resulted from our observations of large <span class="hlt">chondrules</span> and CAIs from the Allende (CV3) meteorite. These voids are 'unambiguous' because their existence cannot be ascribed to plucking during sample preparation, as would be the case in traditional 2-dimensional thin section petrography. Although we focus on large objects in Allende, preliminary observations indicate that void spaces are prevalent in <span class="hlt">chondrules</span> and refractory inclusions in many meteorites. Voids remain ambiguous, however, because their structure and appearance vary between <span class="hlt">chondrules</span> and CAIs, suggesting there may be different causes of void formation in particular objects. Some voids appear to have formed as a result of dilation during cooling. Others are evidence of hydrothermal leaching on the parent body followed by partial chemical replacement. Alternatively, vapor-mediated leaching and replacement may have occurred in the nebula. Yet another possibility is internal brecciation caused by impact, while the object was still free floating in the nebula, and perhaps still partially molten.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...818..103M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...818..103M"><span id="translatedtitle">Planetary Embryo Bow Shocks as a Mechanism for <span class="hlt">Chondrule</span> Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mann, Christopher R.; Boley, Aaron C.; Morris, Melissa A.</p> <p>2016-02-01</p> <p>We use radiation hydrodynamics with direct particle integration to explore the feasibility of <span class="hlt">chondrule</span> formation in planetary embryo bow shocks. The calculations presented here are used to explore the consequences of a Mars-size planetary embryo traveling on a moderately excited orbit through the dusty, early environment of the solar system. The embryo’s eccentric orbit produces a range of supersonic relative velocities between the embryo and the circularly orbiting gas and dust, prompting the formation of bow shocks. Temporary atmospheres around these embryos, which can be created via volatile outgassing and gas capture from the surrounding nebula, can non-trivially affect thermal profiles of solids entering the shock. We explore the thermal environment of solids that traverse the bow shock at different impact radii, the effects that planetoid atmospheres have on shock morphologies, and the stripping efficiency of planetoidal atmospheres in the presence of high relative winds. Simulations are run using adiabatic and radiative conditions, with multiple treatments for the local opacities. Shock speeds of 5, 6, and 7 km s-1 are explored. We find that a high-mass atmosphere and inefficient radiative conditions can produce peak temperatures and cooling rates that are consistent with the constraints set by <span class="hlt">chondrule</span> furnace studies. For most conditions, the derived cooling rates are potentially too high to be consistent with <span class="hlt">chondrule</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5190J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5190J"><span id="translatedtitle">Assessing the Degree of Secondary Alteration in <span class="hlt">Chondrules</span> from One of the Least Altered CR Chondrites, EET 92042</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, R. H.; Brearley, A. J.; Henkel, T.; Lyon, I.</p> <p>2015-07-01</p> <p>Most <span class="hlt">chondrules</span> in EET 92042 are close to pristine. Observed alteration effects at the edges of <span class="hlt">chondrules</span>, including smooth phyllosilicate rims, are heterogeneous because they are dependent on local mineralogy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040065904&hterms=evidence+fact&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Devidence%2Bfact','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040065904&hterms=evidence+fact&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Devidence%2Bfact"><span id="translatedtitle">Clear Evidence for Fe-60 in Silicate from a Semarkona <span class="hlt">Chondrule</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huss, G. R.; Tachibana, S.</p> <p>2004-01-01</p> <p>Fe-60 (t(sub 1/2) = 1.5 Ma) is key to understanding the sources of short-lived radionuclides in the early solar system because it is the only one among those known from meteoritic material that is produced only in stars [1]. Within the last year, it has become clear that Fe-60 was present in sulfides from primitive ordinary and enstatite chondrites in amounts sufficient to require a recent stellar input [2-5]. The sulfide data indicate an initial Fe-60/Fe-56 ratio for the early solar system of between approx. 3 10(exp -7) and approx. 1.6 10(exp -6) [2-4]. However, iron (and nickel?) in sulfides is easily mobilized by very mild heating [e.g., 6], so there is considerable uncertainty over the true initial ratio. To resolve this uncertainty, we have begun a search for evidence of Fe-60 in silicates from primitive chondrites. In <span class="hlt">olivine</span> from type 3.0-3.1 ordinary chondrites, diffusive exchange of iron and magnesium has not occurred to any significant degree, and diffusive exchange in pyroxene is slower [7]. However, the relatively small elemental fractionation of iron from nickel in silicates, coupled with the fact that the daughter nuclide, Ni-60, makes up approx. 26 % of normal nickel, make detection of excesses of radiogenic Ni-60 very difficult. Fortunately, we have found a fine-grained radiating-pyroxene <span class="hlt">chondrule</span> in Semarkona (LL3.0) with a very high Fe/Ni ratio that gives clear evidence of Fe-60.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1022895','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1022895"><span id="translatedtitle">Extremely NA and CL Rich <span class="hlt">Chondrule</span> AL3509 from the Allende Meteorite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wasserburg, G J; Hutcheon, I D; Aleon, J; Ramon, E C; Krot, A N; Nagashima, K; Brearley, A J</p> <p>2011-04-07</p> <p>We report on the mineralogy, petrology, chemistry, oxygen isotopes, {sup 26}Al-{sup 26}Mg and {sup 36}Cl-{sup 36}S isotope systematics of the Allende <span class="hlt">chondrule</span> Al3509 discovered and described by [1] and [2]. This spherical object ({approx}1cm {phi}) contains {approx}10% Na and 1% Cl, and nearly pure {sup 129}Xe [({sup 129}Xe/{sup 127}I) = 1.1 x 10{sup -4} (3)]. This high enrichment in halogens makes it of interest in searching for radiogenic {sup 36}S from {sup 36}Cl (t{sub 1/2} {approx} 0.3 Ma) decay. While there is strong evidence for the presence of {sup 36}Cl in sodalite and wadalite in CV CAIs [4,5], some sodalites show no evidence for excesses of {sup 36}S ({sup 36}S*). In contrast, high inferred initial {sup 36}Cl/{sup 35}Cl = 2 x 10{sup -5} has been found in wadalite from the Allende CAI AJEF [5]. The observed {sup 36}S excesses in sodalite are not correlated with radiogenic {sup 26}Mg, decay product of {sup 26}Al (t{sub 1/2} {approx} 0.72 Ma) [4]. From the inferred initial {sup 36}Cl/{sup 35}Cl ratios and consideration of both AGB and SNe stellar sources, {sup 36}Cl must be the product of charged particle irradiation within the early solar system. However, neither the specific nuclear production mechanism nor the irradiation site have been identified. Both sodalite and wadalite are found as late stage alteration products of CAIs together with grossular, monticellite, Al-rich pyroxene, wollastonite, nepheline, ferroan <span class="hlt">olivine</span>, and ferroan pyroxenes. This late-stage alteration has been found to extensively change some CAIs in Allende, but clear residues of spinel, hibonite and Wark-Lovering rims are recognizable remnants of the original CAIs. The nature of the widespread volatile alteration process as well as that of the fluid phase remain controversial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014M%26PS...49.1440E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014M%26PS...49.1440E"><span id="translatedtitle">Crystallization kinetics of <span class="hlt">olivine</span>-phyric shergottites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ennis, Megan E.; McSween, Harry Y.</p> <p>2014-08-01</p> <p>Crystal size distribution (CSD) and spatial distribution pattern (SDP) analyses are applied to the early crystallizing phases, <span class="hlt">olivine</span> and pyroxene, in <span class="hlt">olivine</span>-phyric shergottites (Elephant moraine [EET] 79001A, Dar al Gani [DaG] 476, and dhofar [Dho] 019) from each sampling locality inferred from Mars ejection ages. Trace element zonation patterns (P and Cr) in <span class="hlt">olivine</span> are also used to characterize the crystallization history of these Martian basalts. Previously reported 2-D CSDs for these meteorites are re-evaluated using a newer stereographically corrected methodology. Kinks in the <span class="hlt">olivine</span> CSD plots suggest several populations that crystallized under different conditions. CSDs for pyroxene in DaG 476 and EET 79001A reveal single populations that grew under steady-state conditions; pyroxenes in Dho 019 were too intergrown for CSD analysis. Magma chamber residence times of several days for small grains to several months for <span class="hlt">olivine</span> megacrysts are calculated using the CSD slopes and growth rates inferred from previous experimental data. Phosphorus imaging in <span class="hlt">olivines</span> in DaG 476 and Dho 019 indicate rapid growth of skeletal, sector-zoned, or patchy cores, probably in response to delayed nucleation, followed by slow growth, and finally rapid dendritic growth with back-filling to form oscillatory zoning in rims. SPD analyses indicate that <span class="hlt">olivine</span> and pyroxene crystals grew or accumulated in clusters rather than as randomly distributed grains. These data reveal complex solidification histories for Martian basalts, and are generally consistent with the formation at depth of <span class="hlt">olivine</span> megacryst cores, which were entrained in ascending magmas that crystallized pyroxenes, small <span class="hlt">olivines</span>, and oscillatory rims on megacrysts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V53C4886M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V53C4886M"><span id="translatedtitle">Experimental Study of <span class="hlt">Olivine</span>-rich Troctolites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mu, S.; Faul, U.</p> <p>2014-12-01</p> <p>This experimental study is designed to complement field observations of <span class="hlt">olivine</span>-rich troctolites in ophiolites and from mid-ocean ridges. The <span class="hlt">olivine</span>-rich troctolites are characterized by high volume proportion of <span class="hlt">olivine</span> with interstitial plagioclase and clinopyroxene. Typically the clinopyroxene occurs in the form of few large, poikilitic grains. The primary purpose of this study is to investigate the effects of cooling process on the geometry of the interstitial phases (clinopyroxene and plagioclase). Experiments are conducted in a piston cylinder apparatus by first annealing <span class="hlt">olivine</span> plus a basaltic melt with a composition designed to be in equilibrium with four phases at ~ 1 GPa and 1250ºC. Initially, we anneal the <span class="hlt">olivine</span>-basalt aggregates at 1350 °C and 0.7 GPa for one week to produce a steady state microstructure. At this temperature only <span class="hlt">olivine</span> and minor opx are present as crystalline phases. We then cool the samples over two weeks below their solidus temperature, following different protocols. The post-run samples are sectioned, polished, and imaged at high resolution and analyzed by using a field emission SEM. Initial observations show that under certain conditions clinopyroxene nucleates distributed throughout the aggregate at many sites, forming relatively small, rounded to near euhedral grains. Under certain conditions few cpx grains nucleate and grow with a poikilitic shape, partially or fully enclosing <span class="hlt">olivine</span> grains, as is observed in natural samples. As for partially molten aggregates quenched form the annealing temperature, the microstructure will be characterized by tracing phase boundaries on screen by using ImageJ software. The geometry of the interstitial phases will be quantified by determining the grain boundary wetness, in this case the ratio of the length of polyphase to single phase (<span class="hlt">olivine-olivine</span>) boundaries. Compositional data will also be used to study the change in major element compositions before and after the cooling process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Icar..228..288S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Icar..228..288S"><span id="translatedtitle"><span class="hlt">Olivine</span>-dominated asteroids: Mineralogy and origin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanchez, Juan A.; Reddy, Vishnu; Kelley, Michael S.; Cloutis, Edward A.; Bottke, William F.; Nesvorný, David; Lucas, Michael P.; Hardersen, Paul S.; Gaffey, Michael J.; Abell, Paul A.; Corre, Lucille Le</p> <p>2014-01-01</p> <p><span class="hlt">Olivine</span>-dominated asteroids are a rare type of objects formed either in nebular processes or through magmatic differentiation. The analysis of meteorite samples suggest that at least 100 parent bodies in the main belt experienced partial or complete melting and differentiation before being disrupted. However, only a few <span class="hlt">olivine</span>-dominated asteroids, representative of the mantle of disrupted differentiated bodies, are known to exist. Due to the paucity of these objects in the main belt their origin and evolution have been a matter of great debate over the years. In this work we present a detailed mineralogical analysis of twelve <span class="hlt">olivine</span>-dominated asteroids. We have obtained near-infrared (NIR) spectra (0.7-2.4 μm) of asteroids (246) Asporina, (289) Nenetta, (446) Aeternitas, (863) Benkoela, (4125) Lew Allen and (4490) Bamberry. Observations were conducted with the Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i. This sample was complemented with spectra of six other <span class="hlt">olivine</span>-dominated asteroids including (354) Eleonora, (984) Gretia, (1951) Lick, (2501) Lohja, (3819) Robinson and (5261) Eureka obtained by previous workers. Within our sample we distinguish two classes, one that we call monomineralic-<span class="hlt">olivine</span> asteroids, which are those whose spectra only exhibit the 1 μm feature, and another referred to as <span class="hlt">olivine</span>-rich asteroids, whose spectra exhibit the 1 μm feature and a weak (Band II depth ˜4%) 2 μm feature. For the monomineralic-<span class="hlt">olivine</span> asteroids the <span class="hlt">olivine</span> chemistry was found to range from ˜Fo49 to Fo70, consistent with the values measured for brachinites and R chondrites. In the case of the <span class="hlt">olivine</span>-rich asteroids we determined their <span class="hlt">olivine</span> and low-Ca pyroxene abundance using a new set of spectral calibrations derived from the analysis of R chondrites spectra. We found that the <span class="hlt">olivine</span> abundance for these asteroids varies from 0.68 to 0.93, while the fraction of low-Ca pyroxene to total pyroxene ranges from 0.6 to 0.9. A search for dynamical connections between the <span class="hlt">olivine</span>-dominated asteroids and asteroid families found no genetic link (of the type core-mantel-crust) between these objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010LPI....41.1961D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010LPI....41.1961D"><span id="translatedtitle">Cosmogenic Neon in Individual <span class="hlt">Chondrule</span> Fragments: Records of Pre-Compaction Exposure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, J. P.; Goswami, J. N.; Pravdivtseva, O. V.; Meshik, A. P.; Hohenberg, C. M.</p> <p>2010-03-01</p> <p>This first ever study on 41 splits of <span class="hlt">chondrules</span> show that 21Ne CRE ages in 11 splits are high compared to that of host, ranging from 5-35 Ma. Splits from same <span class="hlt">chondrule</span> show different CRE ages. We conclude that the excess is due to early active Sun.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19800056699&hterms=metamorphism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmetamorphism','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19800056699&hterms=metamorphism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmetamorphism"><span id="translatedtitle">Metamorphism of the H-group chondrites - Implications from compositional and textural trends in <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lux, G.; Keil, K.; Taylor, G. J.</p> <p>1980-01-01</p> <p>The paper discusses element bulk compositions of 373 <span class="hlt">chondrules</span> from 18 H3 to H6 chondrites determined by broad-beam electron probe analysis. Bulk <span class="hlt">chondrule</span> FeO and Al2O3 amounts increase and TiO2 and Cr2O3 decrease with increasing petrologic type; normative faylite, albite, and plagioclase amounts increase through the petrologic sequence. <span class="hlt">Chondrule</span> diameters correlate with phenocryst sizes in porphyritic <span class="hlt">chondrules</span> of type 3 chondrites, but this correlation is diminished in the higher petrologic types. The compositional trends in <span class="hlt">chondrules</span> through the petrologic sequence are attributed to diffusion and equilibration among <span class="hlt">chondrules</span>, and between <span class="hlt">chondrules</span> and matrix in response to increasing degrees of thermal metamorphism. It is suggested that H-group chondrites are formed by accretion of high-temperature (<span class="hlt">chondrules</span>) and low-temperature (matrix) materials. Internal reheating of the parent materials to different temperatures caused compositional equilibration, grain coarsening, and reduction of FeO to Fe(0) by carbon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002GeCoA..66..347W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002GeCoA..66..347W"><span id="translatedtitle">Iodine-Xenon dating of <span class="hlt">chondrules</span> from the Qingzhen and Kota Kota enstatite chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whitby, J. A.; Gilmour, J. D.; Turner, G.; Prinz, M.; Ash, R. D.</p> <p>2002-01-01</p> <p>Initial 129I/ 127I values (I-Xe ages) have been obtained for individual mineralogically characterized <span class="hlt">chondrules</span> and interchondrule matrix from the enstatite chondrites Qingzhen (EH3) and Kota Kota (EH3). In view of the absence of aqueous alteration and the low-peak metamorphic temperatures experienced by these meteorites, we suggest that the I-Xe ages for the <span class="hlt">chondrules</span> record the event in which they were formed. These ages are within the range recorded for <span class="hlt">chondrules</span> from ordinary chondrites, demonstrating that <span class="hlt">chondrules</span> formed during the same time interval in the source regions of both ordinary chondrites and enstatite chondrites. The timing of this <span class="hlt">chondrule</span>-forming episode or episodes brackets the I-Xe closure age of planetesimal bodies such as the Shallowater aubrite parent body. Although <span class="hlt">chondrule</span> formation need not have occurred close to planetesimals, the existence of planetesimals at the same time as <span class="hlt">chondrule</span> formation provides constraints on models of this process. Whichever mechanisms are proposed to form and transport <span class="hlt">chondrules</span>, they must be compatible with models of the protosolar nebula which predict the formation of differentiated bodies on the same timescale at the same heliocentric distance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010LPI....41.1756W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010LPI....41.1756W"><span id="translatedtitle">Petrology and Oxygen Isotopes of <span class="hlt">Chondrules</span> in the Kota Kota EH3 Chondrite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weisberg, M. K.; Ebel, D. S.; Kimura, M.; Kita, N. T.; Nakashima, D.</p> <p>2010-03-01</p> <p>Oxygen isotopes of most Kota Kota <span class="hlt">chondrules</span> plot along the TF line and some overlap the OC field on a 3-isotope plot. 16O-rich values in EH3s form a new mixing line. EH3 <span class="hlt">chondrules</span> formed from a distinct oxygen reservoir and show mixing behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985Metic..20..103W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985Metic..20..103W"><span id="translatedtitle"><span class="hlt">Chondrule</span> volume percents - Statistical behavior and visual-estimation guides produced by numerical simulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woronow, A.; King, E. A.</p> <p>1985-03-01</p> <p>A set of reference figures for point counts of <span class="hlt">chondrule</span> volume-percent abundances chondrites have been developed, on the basis of a numerical simulation. The simulation was based on the known volume-percent abundances of <span class="hlt">chondrules</span> having a realistic size-frequency distribution. In the process of generating and sectioning the rock samples, information was obtained regarding the variation of <span class="hlt">chondrule</span> abundances in different thin sections of the same rock. It is shown that, regardless of the actual abundance of the <span class="hlt">chondrules</span>, point counts of a single random section through a chondrite should have a probable error of about 1 percent. A series of computer generated chondrite thin sections is provided which shows the volume-percent <span class="hlt">chondrule</span> densities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19850054070&hterms=graph+minor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgraph%2Bminor','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19850054070&hterms=graph+minor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgraph%2Bminor"><span id="translatedtitle">The origin and history of the metal and sulfide components of <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grossman, J. N.; Wasson, J. T.</p> <p>1985-01-01</p> <p>Instrumental and radiochemical neutron activation analysis is used to determine the concentrations of 14 siderophile and other nonlithophilic elements in 31 <span class="hlt">chondrules</span> from the extremely unequilibrated chondrite Semarkona. The results are presented in tables and graphs, characterized in detail, and compared with the results obtained for lithophile elements in the same samples by Grossman and Wasson (1983). The elements studied are found to be significantly more fractionated than the lithophile elements, with variations in <span class="hlt">chondrule</span>/whole-rock abundances of up to a factor of 1000, a mean ratio of 0.2, and differences between Ni-rich and Ni-depleted <span class="hlt">chondrules</span>. It is argued that the metal and sulfides in the <span class="hlt">chondrules</span> represent the composition of the solar nebula before <span class="hlt">chondrule</span> formation and already contained the siderophile and chalcophile elements, although some Fe was contained in silicates along with Ni, Co, Au, Ge and Se. The segregation of metals during a molten stage is considered of minor importance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100008965','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100008965"><span id="translatedtitle"><span class="hlt">Olivine</span> in Almahata Sitta - Curiouser and Curiouser</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zolensky, M. E.; Herrin, J.; Mikouchi, T.; Satake, W.; Kurihara, T.; Sandford, S. A.; Milam, S. N.; Hagiya, K.; Ohsumi, K.; Friedrich, J. M.; Jeniskens, P.; Shaddad, M. H.; Le, L.; Robinson, G. A.</p> <p>2010-01-01</p> <p>Almahata Sitta (hereafter Alma) is an anomalous, polymict ureilite. Anomalous features include low abundance of <span class="hlt">olivine</span>, large compositional range of silicates, high abundance and large size of pores, crystalline pore wall linings, and overall finegrained texture. Tomography suggests the presence of foliation, which is known from other ureilites. Alma pyroxenes and their interpretation are discussed in two companion abstracts. In this abstract we discuss the composition of <span class="hlt">olivine</span> in Alma, which is indicative of the complexity of this meteorite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160003881','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160003881"><span id="translatedtitle">An Amoeboid <span class="hlt">Olivine</span> Aggregate in LEW 85300</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Komatsu, M. D.; Yamaguchi, A.; Fagan, T. J.; Zolensky, M. E.; Shiran, N.; Mikouchi, T.</p> <p>2016-01-01</p> <p>Amoeboid <span class="hlt">Olivine</span> aggregates (AOAs) are irregularly shaped objects commonly observed in carbonaceous chondrites. Because they are composed of fine-grained <span class="hlt">olivine</span> and Ca-Al-rich minerals, they are sensitive indicators for nebular process and parent body alteration of their parent bodies. Recently an AOA was found in a carbonaceous clast in polymict eucrite LEW 85300. The bulk major element composition of the clast matrix in LEW 85300 suggests a relation to CM, CO and CV chondrites, whereas bulk clast trace and major element compositions do not match any carbonaceous chondrite, suggesting they have a unique origin. Here we characterize the mineralogy of AOA in LEW 85300 and discuss the origin of the carbonaceous clasts. Results and Discussion: The AOA is located in an impact melt vein. Half of the aggregate shows recrystallization textures (euhedral pyroxene and molten metal/FeS) due to impact melting, but the remaining part preserves the original texture. The AOA is composed of <span class="hlt">olivine</span>, FeS and Mg,Al-phyllosilicate. Individual <span class="hlt">olivine</span> grains measure 1-8 microns, with Fe-rich rims, probably due to impact heating. <span class="hlt">Olivines</span> in the AOA are highly forsteritic (Fo95-99), indicating that the AOA escaped thermal metamorphism [4]. Although no LIME (Low-Fe, Mn-Enriched) <span class="hlt">olivine</span> is observed, forsterite composition and the coexistence of Mg,Al-phyllosilicate suggest that the AOA is similar to those in the Bali-type oxidized CV (CVoxB) and CR chondrites. However, it should be noted that fayalitic <span class="hlt">olivine</span>, which commonly occurs in CVoxB AOA, is not observed in this AOA. Also, the smaller grain size (<8 microns) of <span class="hlt">olivine</span> suggests they may be related to CM or CO chondrites. Therefore, we cannot exclude the possibility that the AOA originated from a unique carbonaceous chondrite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.P51A3903F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.P51A3903F"><span id="translatedtitle">Aligned <span class="hlt">Olivine</span> in the Springwater Pallasite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fowler-Gerace, N.; Tait, K.; Moser, D.; Barker, I.; Tian, B. Y.</p> <p>2014-12-01</p> <p>The mechanism by which <span class="hlt">olivine</span> grains became embedded within iron-nickel alloy in pallasite meteorites continues to be a matter of scientific debate. Geochemical and textural observations have failed to fully elucidate the origin and history of the <span class="hlt">olivine</span> crystals; however, little research attention has been devoted to their crystallographic orientations within the metal matrix. Klosterman and Buseck [1] found no crystallographic preferred orientation of <span class="hlt">olivine</span> in nine pallasites, but the Leitz five-axis universal stage method imposed limitations on precision (estimated within ˜4◦) and sample size (only 10 crystals were measured in the Springwater pallasite, for instance). Using Electron Backscatter Diffraction, we have collected crystallographic orientation data (accurate to ±0.5◦ [2]) for 343 crystals within ˜65 cm2 sample surface from Springwater. Though no global crystallographic preferred orientation exists, very low misorientations are observed among [100] axes of <span class="hlt">olivine</span> crystals within specific texturally-defined domains. Combined with our thorough characterization of large-scale Springwater textures, the definitively non-random spatial distribution of <span class="hlt">olivine</span> orientations reveals the nature of the <span class="hlt">olivine</span>'s initial formation environment as well as the sequence of events subsequent to metal incorporation. [1] Klosterman and Buseck. 1973. J Geophys Res 78(32):7581-7588. [2] Oxford Instruments. 2013. http://www.ebsd.com/.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995Metic..30Q.561P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995Metic..30Q.561P"><span id="translatedtitle">Exsolved Ferromagnesian <span class="hlt">Olivine</span>: Why Only in Divnoe?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petaev, M. I.</p> <p>1995-09-01</p> <p>Recently Petaev and Brearley [1] showed that lamellar structure in <span class="hlt">olivine</span> grains in the Divnoe meteorite was produced by the low-temperature exsolution of primary homogeneous grains. Exsolved <span class="hlt">olivine</span> in Divnoe is in accordance with the thermodynamic model of <span class="hlt">olivine</span> solid solution of [2], which predicts a miscibility gap in ferromagnesian <span class="hlt">olivines</span> below ~340 degrees C within a compositional range that widens with decreasing temperature. Experiments on the coexistence of <span class="hlt">olivines</span> having a range of compositions with aqueous solutions of (Fe,Mg)Cl2 [3] suggest that exsolution in ferromagnesian <span class="hlt">olivines</span> could occur even at temperatures as high as ~400 - 450 degrees C. However, [1] remains the only observation of exsolution in natural <span class="hlt">olivines</span> so far. This means either that (1) the exsolution in Divnoe <span class="hlt">olivine</span> is unique, or (2) <span class="hlt">olivine</span> grains in other slowly cooled coarse-grained rocks has not been studied closely enough to detect them. This work attempts to clarify the issue. <span class="hlt">Olivine</span> grains from selected meteorites (Springwater pallasite, Lowitz mesosiderite, ALHA 84025 brachinite, Gorlovka H3-4 chondrite and Krymka L3 chondrite, and the Calcalong Creek lunar meteorite) and terrestrial rocks (San Carlos forsterite and Rockport fayalite) were studied by EPMA using the same equipment and technique as in [1]. Among meteorites, pallasites and mesosiderites are known to have slowest cooling rates at low temperatures. <span class="hlt">Olivines</span> in the Springwater pallasite (Fa18) [4] and the Lowitz mesosiderite (Fa15-37) [5] are compositionally comparable with that of Divnoe (Fa23-29) [1], and it was expected that exsolved <span class="hlt">olivine</span> grains would be found there. <span class="hlt">Olivines</span> from other samples were studied for comparison. No lamellar structure was observed in BSE images of the <span class="hlt">olivine</span> grains studied. The variations of Fa contents in <span class="hlt">olivine</span> grains from all samples but Springwater and Lowitz meteorites display no regular pattern, and are basically within the 2sigma uncertainty range (+/-0.2 mole % Fa). As expected, <span class="hlt">olivines</span> from the Lowitz mesosiderite and, especially, from the Springwater pallasite display somewhat larger variations, within the ranges of 20.1 - 21.0 and 15.8 -17.7 mole % Fa, respectively. The <span class="hlt">olivine</span> in Springwater shows a surprisingly regular pattern of minima spaced at ~ 16 micrometers. For reasons that are unclear all 'minima' analyses have low totals (90.47-94.31 wt.%), whereas most other analyses have totals > 97%. However, stoichiometry of all analyses is perfect; cation totals per 4 oxygens are 3.00+/-0.01, with very minor excess of Si over Mg+Fe in the 'minima' analyses. The results obtained so far suggest that lamellar structure of <span class="hlt">olivine</span> grains in the Divnoe meteorite is unique. While chemical variability is found in the Springwater and Lowitz <span class="hlt">olivines</span>, there is no lamellar structure, and the magnitude of the variations is 1.5 - 2 times smaller than it is in Divnoe <span class="hlt">olivines</span>. Since <span class="hlt">olivine</span> compositions in Divnoe, Lowitz and Springwater are similar, the structural differences among them must be due to different thermal histories. The lack of lamellar structure in the Lowitz <span class="hlt">olivine</span> implies that even the slowest cooling down to 250 degrees C recorded in mesosiderites [6] does not result in <span class="hlt">olivine</span> exsolution. It is possible that Divnoe experienced secondary reheating followed by prolonged low-temperature annealing. This would also account for the lack of shock features in the Divnoe opaque minerals [7] and the difference in distributions of cosmic-ray track lengths and densities between <span class="hlt">olivine</span> and pyroxene [8]. References: [1] Petaev M. I. and Brearley A. J. (1994) Science, 266, 1545-1547. [2] Sack R. O. and Ghiorso M. S. (1989) Contrib. Mineral. Petrol., 102, 41-68. [3] Schulien S. (1980) Contrib. Mineral. Petrol., 74, 85-91. [4] Buseck P. R. (1977) GCA, 41, 711-740. [5] Delaney J. S. et al. (1980) Proc. LPSC 11th, 1073-1087. [6] Ganguly J. et al. (1994) GCA, 58, 2711-2723. [7] Petaev M. I. et al. (1994) Meteoritics, 29, 182-199. [8] Petaev M. I. et al. (1990) LPS XXI, 950-951.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19770034711&hterms=experimental+study+specific&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dexperimental%2Bstudy%2Bspecific','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19770034711&hterms=experimental+study+specific&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dexperimental%2Bstudy%2Bspecific"><span id="translatedtitle">An experimental investigation of <span class="hlt">olivine</span> morphology</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Donaldson, C. H.</p> <p>1976-01-01</p> <p>Results are reported for a morphological study of <span class="hlt">olivine</span> and an experimental investigation performed to determine the degrees of supercooling and the cooling rates necessary to crystallize particular morphologies. Ten arbitrary categories of three-dimensional <span class="hlt">olivine</span> crystal shape are identified: polyhedral, granular, hopper, chain, lattice, plate, branching, radiate, feather, and swallow-tail. The morphological study establishes that equant and tabular crystals are the common shapes of <span class="hlt">olivine</span>, nonequant crystals are elongate parallel to the a or c axis, and skeletal crystals result when a particular form is missing or only partially developed. In the experiment, <span class="hlt">olivine</span> crystals were grown by melting rock samples above their liquidus temperatures before initiating crystallization. The results show that <span class="hlt">olivine</span> morphology changes systematically as a function of the degree of melt supercooling, the melt cooling rate, and the normative <span class="hlt">olivine</span> and water contents of the melt. It is also found that each shape has a specific range of temperature stability which is essentially independent of melt composition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012M%26PS...47.2170S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012M%26PS...47.2170S"><span id="translatedtitle">The origin of <span class="hlt">chondrules</span> and chondrites: Debris from low-velocity impacts between molten planetesimals?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sanders, Ian S.; Scott, Edward R. D.</p> <p>2012-12-01</p> <p>We investigate the hypothesis that many <span class="hlt">chondrules</span> are frozen droplets of spray from impact plumes launched when thin-shelled, largely molten planetesimals collided at low speed during accretion. This scenario, here dubbed "splashing," stems from evidence that such planetesimals, intensely heated by 26Al, were abundant in the protoplanetary disk when <span class="hlt">chondrules</span> were being formed approximately 2 Myr after calcium-aluminum-rich inclusions (CAIs), and that chondrites, far from sampling the earliest planetesimals, are made from material that accreted later, when 26Al could no longer induce melting. We show how "splashing" is reconcilable with many features of <span class="hlt">chondrules</span>, including their ages, chemistry, peak temperatures, abundances, sizes, cooling rates, indented shapes, "relict" grains, igneous rims, and metal blebs, and is also reconcilable with features that challenge the conventional view that <span class="hlt">chondrules</span> are flash-melted dust-clumps, particularly the high concentrations of Na and FeO in <span class="hlt">chondrules</span>, but also including <span class="hlt">chondrule</span> diversity, large phenocrysts, macrochondrules, scarcity of dust-clumps, and heating. We speculate that type I (FeO-poor) <span class="hlt">chondrules</span> come from planetesimals that accreted early in the reduced, partially condensed, hot inner nebula, and that type II (FeO-rich) <span class="hlt">chondrules</span> come from planetesimals that accreted in a later, or more distal, cool nebular setting where incorporation of water-ice with high Δ17O aided oxidation during heating. We propose that multiple collisions and repeated re-accretion of <span class="hlt">chondrules</span> and other debris within restricted annular zones gave each chondrite group its distinctive properties, and led to so-called "complementarity" and metal depletion in chondrites. We suggest that differentiated meteorites are numerically rare compared with chondrites because their initially plentiful molten parent bodies were mostly destroyed during <span class="hlt">chondrule</span> formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeCoA.164..543T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeCoA.164..543T"><span id="translatedtitle">Redistribution of <span class="hlt">chondrules</span> in a carbonaceous chondrite parent body: A model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomeoka, Kazushige; Ohnishi, Ichiro</p> <p>2015-09-01</p> <p>Carbonaceous chondrites mainly consist of <span class="hlt">chondrules</span> and inclusions embedded in a fine-grained matrix. This texture is widely believed to have formed primarily by direct accretion of solar nebular materials, although it may have been modified to various extents by subsequent parent-body processes. Recently, we studied all <span class="hlt">chondrules</span> and inclusions larger than 400 μm in diameter and their rims (referred to as <span class="hlt">chondrules</span>/rims) in the Mokoia CV3 carbonaceous chondrite using a scanning electron microscope, and found that the <span class="hlt">chondrules</span>/rims experienced various degrees of aqueous alteration and that some also exhibit evidence of thermal metamorphism. The mineralogical and petrographic characteristics of the <span class="hlt">chondrules</span>/rims suggest that the alteration and metamorphism occurred within the meteorite parent body. In contrast, however, the surrounding matrix does not show evidence of such alteration and metamorphism. These findings indicate that the alteration and metamorphism of the <span class="hlt">chondrules</span>/rims did not occur in situ. Based on these results, we proposed a model that the <span class="hlt">chondrules</span>/rims are actually clasts transported from regions in the parent body different from the location where the host meteorite was finally lithified. If it can be assumed that the <span class="hlt">chondrules</span> and inclusions studied are representative of all <span class="hlt">chondrules</span> and inclusions in Mokoia, the results and interpretation pose a fundamental challenge regarding the formation of the whole Mokoia lithology; that is, it cannot be explained by either direct accretion of the solar nebula or conventional parent-body brecciation. We propose a model for the development of the Mokoia lithology through formation of <span class="hlt">chondrules</span>/rims and fine matrix grains by fragmentation in different regions in the parent body, followed by transportation, mixing, and accumulation in a fluid state, and finally lithification of those objects. These processes may have been repeated, cyclically, within the parent body.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.V43F..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.V43F..07P"><span id="translatedtitle">Atom Probe Tomography of <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parman, S. W.; Gorman, B.; Jackson, C.; Cooper, R. F.; Jaeger, D.</p> <p>2010-12-01</p> <p>Here we present atom probe tomographic (APT) analyses of natural <span class="hlt">olivine</span>. APT provides three-dimensional trace element and isotopic analysis with sub-nanometer spatial resolution. It has been used for many years in engineering and materials science, but has not been applied to geological materials because traditional APT can only be used on conducting (usually metal) samples. The recent development of laser assisted APT has changed this situation, and now semi-conductors and insulators can be analyzed (Marquis et al., 2009, Kelly et al 2007). Potentially, this opens APT to extensive use in geoscience as many Fe-bearing silicates are semi-conductors. In this study, we explore the capability of the new class of APT instrumentation to analyze geological materials. APT involves the controlled evaporation of small, cylindrical specimens (100's nm in diameter) within an electric field. Specimens are typically prepared using in-situ focused-ion-beam (FIB) liftout and shaping techniques. Evaporated atoms are accelerated to a detector plate that records the position of the atom with sub-nm precision. Evaporated atoms are measured using time-of-flight mass spectrometry, allowing both elemental and isotopic determination. Since the method progressively ablates into the needle, the final analytical result is a nm-scale 3-dimensional image in which the position and identity of each detected atom is known. Typical mass resolution is between 200 and 1200 (full-width at half maximum) and typical concentration detection limits are 10 ppm. The number of potential applications of APT to igneous, metamorphic and sedimentary materials is large, ranging from studies of mineral and melt inclusions, to fine scale layering in minerals, to reaction surfaces and diffusion profiles. Much recent progress in the geochemical and petrologic fields has been driven by the increasing spatial resolution of the ion probe and laser ablation ICPMS. The ability of APT to provide atom-scale mass spectrometry should continue this trend. The main limitations to atom probe analysis of geological materials are the ability to control heat flow during laser pulsing and the associated ability to control clustering during field evaporation. Both of these factors can be controlled through specimen preparation and varying the atom probe experimental factors. <span class="hlt">Olivine</span> specimens were properly analyzed using laser pulsed APT through the use of shallow (nominally 1mm) FIB liftouts and wide shank angle specimen apices. APT settings were found to give the best mass resolution using low specimen temperatures, 0.2 nJ laser energy, and 50 kHz pulse repetition rate. Increasing any of these values increases the amount of thermal tails due to excessive heat buildup, reducing the mass spectrum resolution, and ultimately affecting the spatial resolution of the reconstruction. Marquis EA, Miller MK, Blavette D, Ringer SP, Sudbrack CK and Smith DW (2009). MRS Bulletin 34: 725-730. Thomas F. Kelly, David J. Larson, Keith Thompson, Roger L. Alvis, Joseph H. Bunton, Jesse D. Olson, Brian P. Gorman, Ann. Rev. Mat. Res. 37: 681-727.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984GeCoA..48.1189S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984GeCoA..48.1189S"><span id="translatedtitle">Chemical and physical studies of type 3 chondrites. III <span class="hlt">Chondrules</span> from the Dhajala H3.8 chondrite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sears, D. W. G.; Sparks, M. H.; Rubin, A. E.</p> <p>1984-06-01</p> <p>Thermoluminescence (TL) properties have been measured in 58 <span class="hlt">chondrules</span> separated from the Dhajala H3.8 chondrite. The pyrolytic <span class="hlt">chondrules</span> are noted to have higher mass-normalized TL values than nonpyrolytic ones. Significant correlations are noted between log(TL) and the bulk CaO, Al2O3, and MnO content of the <span class="hlt">chondrules</span>. These, together with correlations of log(TL) with the CaO, Al2O3, SiO2 and normative anorthite content of the <span class="hlt">chondrule</span> glass, indicate an association of the TL and the abundance and position of mesostasis. It is suggested that the TL level in a given <span class="hlt">chondrule</span> is governed by its bulk composition and metamorphism, and it is hypothesized that the devitrification resistance of unequilibrated <span class="hlt">chondrule</span> mesostasis explains the unequilibration of certain <span class="hlt">chondrules</span> in type 3 ordinary chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16724060','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16724060"><span id="translatedtitle"><span class="hlt">Chondrule</span> formation in particle-rich nebular regions at least hundreds of kilometres across.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cuzzi, Jeffrey N; Alexander, Conel M O'D</p> <p>2006-05-25</p> <p><span class="hlt">Chondrules</span> are millimetre-sized spherules (mostly silicate) that dominate the texture of primitive meteorites. Their formation mechanism is debated, but their sheer abundance suggests that the mechanism was both energetic and ubiquitous in the early inner Solar System. The processes suggested--such as shock waves, solar flares or nebula lightning--operate on different length scales that have been hard to relate directly to <span class="hlt">chondrule</span> properties. <span class="hlt">Chondrules</span> are depleted in volatile elements, but surprisingly they show little evidence for the associated loss of lighter isotopes one would expect. Here we report a model in which molten <span class="hlt">chondrules</span> come to equilibrium with the gas that was evaporated from other <span class="hlt">chondrules</span>, and which explains the observations in a natural way. The regions within which the <span class="hlt">chondrules</span> formed must have been larger than 150-6,000 km in radius, and must have had a precursor number density of at least 10 m(-3). These constraints probably exclude nebula lightning, and also make formation far from the nebula midplane problematic. The wide range of <span class="hlt">chondrule</span> compositions may be the result of different combinations of the local concentrations of precursors and the local abundance of water ice or vapour. PMID:16724060</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMMR11A2469D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMMR11A2469D"><span id="translatedtitle">Effect of fO2 on the incorporation and diffusivity of Li in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dohmen, R.; Coogan, L. A.</p> <p>2012-12-01</p> <p>Over the last decade the geochemical behaviour of Li has become of special interest since it was speculated that Li stable isotopes could be a promising tracer for subduction zone processes. However, there have been many studies of natural samples but our experimental and theoretical basis for interpreting these data is still lacking. Two diffusion mechanisms were identified for Li in <span class="hlt">olivine</span> [1]. Their contribution to the net flux of Li in <span class="hlt">olivine</span> depends on the vacancy concentration on the metal sites, which is sensitive to the fO2. Therefore we have studied the effect of fO2 on Li solubility and diffusion in <span class="hlt">olivine</span>. Experimental approach: thin plates of crushed, natural <span class="hlt">olivine</span> single crystals were embedded into two different kind of powders, ground plagioclase with about 2.5 ppm Li or a pre-annealed powder mixture of San Carlos <span class="hlt">olivine</span> and isotopically enriched Li. All runs were performed in a gas-mixing furnace with fO2 controlled by flowing CO/CO2 mixture. In each run we simultaneously annealed about 100 micrometer-sized samples of Pakistan <span class="hlt">olivine</span> and San Carlos <span class="hlt">olivine</span>. In addition we have added to each run a mm sized crystallographically oriented parallelepiped of San Carlos <span class="hlt">olivine</span>. For each powder reservoir we have performed a set of three anneals at 1200 C and different fO2. Cross sections of the run products were polished and analyzed with LA-ICP-MS. Results: In all cases the Li isotopes and concentrations were homogeneous in the 100 micrometer sized grains with one exception, the experiment at 1.e-10 <span class="hlt">bar</span> with the highly enriched Li reservoir. The final Li concentration was slightly lower in the Pakistan than San Carlos <span class="hlt">olivine</span> and was much lower in general if buffered by the plagioclase powder. Most importantly, the Li concentration increased systematically with increasing oxygen fugacity, indicating that the incorporation of Li in <span class="hlt">olivine</span> is fO2 dependent. The mm-sized, oriented crystal was in most cases zoned and the extent of zoning depends on the diffusion direction. In addition the profiles became systematically longer with decreasing fugacity and at the most reducing conditions the crystal was almost homogenous. However, the isotopes were in all cases completely homogenized and equilibrated with the isotopically enriched reservoir. Thermodynamic model: We extended the quantitative point defect model for <span class="hlt">olivine</span> [2] and reproduced the effect of fO2 on the solubility of Li when we assume it is mainly on the metal site and charge balanced by the formation of Fe3+ on the metal site. Conclusions: Our results strongly indicate that incorporation of Li is dependent on the fO2, less dependent on the trace element content. Diffusion of Li in <span class="hlt">olivine</span> is anisotropic and dependent on fO2. Our quantitative point defect model for <span class="hlt">olivine</span> underpins the experimental results. This will allow us to develop a multi-component diffusion model considering relevant point defects, e.g. Fe3+ and metal vacancies. Such a model will hopefully help us to simulate diffusion of Li at various natural circumstances including fO2 as a critical parameter. References: [1] Dohmen et al. (2010) Geochim Cosmochim Acta 74, 274-292; [2] Dohmen and Chakraborty (2007), Phys Chem Minerals 34, 597- 598.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19760036497&hterms=perovskite+solar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dperovskite%252C%2Bsolar','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19760036497&hterms=perovskite+solar&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dperovskite%252C%2Bsolar"><span id="translatedtitle">Amoeboid <span class="hlt">olivine</span> aggregates in the Allende meteorite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Grossman, L.; Steele, I. M.</p> <p>1976-01-01</p> <p>Greyish-brown irregularly-shaped aggregates composed predominantly of <span class="hlt">olivine</span> make up nearly 2% of the Allende meteorite by volume. Many of the aggregates are constructed of subspherical lumps of micron-sized crystals of <span class="hlt">olivine</span>, pyroxene, nepheline and sodalite surrounded by coarser-grained <span class="hlt">olivine</span>. Rarely, anorthite, spinel and perovskite are also present. The <span class="hlt">olivine</span> ranges in composition from Fo64 to Fo99. Pyroxenes range from aluminous diopside to hedenbergite to very Al-rich and Ti-Al-rich varieties. The nepheline contains 1.6-2.4% K2O and 1.6-5.2% CaO but the sodalite is significantly poorer in these elements. The spinel contains 2.1-13.4% FeO. Textural information and oxygen isotopic data suggest that the aggregates are composed of primary, solid condensates from the solar nebula. The perovskite, spinel and Ti-Al-rich pyroxenes are the remains of high-temperature condensates, but the <span class="hlt">olivine</span> compositions and the presence of feldspathoids indicate that some of the grains continued to react with the solar nebular vapor in the temperature range 500-900 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMMR22A..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMMR22A..07C"><span id="translatedtitle">Diffusion of highly charged cations in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cherniak, D. J.; Watson, E. B.; Liang, Y.</p> <p>2012-12-01</p> <p>Diffusion of tungsten, titanium and phosphorus have been measured in natural iron-bearing <span class="hlt">olivine</span> (~Fo90) and synthetic forsterite. Experiments were run under buffered conditions (with iron-wustite or Ni-NiO buffers) in 1-atm furnaces. The sources of diffusant for experiments were MgWO4 for tungsten diffusion, Mg2TiO4 for Ti diffusion, and AlPO4 for P diffusion; in all cases these compounds were pre-reacted at high temperature with Mg2SiO4 or Fe-bearing <span class="hlt">olivine</span> prior to diffusion anneals. Samples were placed with the source materials in noble metal or silica capsules, which were sealed under vacuum in silica glass ampoules with solid buffers. Rutherford backscattering spectrometry (RBS) was used to measure depth profiles for all sets of experiments; measurements of P were also made with Nuclear Reaction Analysis using the 31P(α,p)34S reaction. These new data suggest marked differences among diffusivities of these cations, with titanium diffusion faster than diffusion of tungsten, but slower than diffusion of phosphorus over the conditions investigated. Diffusivities of all of these elements appear significantly slower than those of divalent cations in <span class="hlt">olivine</span>. These results will be discussed in context with extant diffusion data for major, trace and minor elements in <span class="hlt">olivine</span>. The effects of oxygen fugacity and <span class="hlt">olivine</span> composition on diffusion, and potential implications for diffusion mechanisms will also be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910025734&hterms=Hanford+Washington&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DHanford%252C%2BWashington','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910025734&hterms=Hanford+Washington&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DHanford%252C%2BWashington"><span id="translatedtitle"><span class="hlt">Chondrule</span>-like objects and brown glasses in howardites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Olsen, Edward J.; Fredriksson, Kurt; Rajan, Sundar; Noonan, Albert</p> <p>1990-01-01</p> <p>Chondrulelike objects and brown glasses were analyzed in the howardites, Bununu, Malvern, Monticello, Pavlovka, and Yamato 7308. The objects are very similar to <span class="hlt">chondrules</span> in ordinary and carbonaceous chondrites. Like the brown glasses, the chondrulelike objects could have been produced by impact melting that left some crystalline nuclei, followed by a slower cooling rate than for the glasses. Alternatively, these objects are <span class="hlt">chondrules</span> implanted from chondrite impactors. They are, however, without rims or any adhering matrix. The brown glasses appear to represent melting of average regolithic surface material, except for Monticello and Y7308, both of which have some siliceous glasses. The siliceous glasses could not have been produced by vapor fractionation but by melting of differentiated lithologies such as fayalitic granites. Impact mechanics indicates that howardites with abundant brown glasses came from an asteroid larger than Vesta (greater than 400 km radius), upon which impacts occurred at relative velocities of up to 5 km/s. Howardites with little or no brown glasses came from a smaller parent body. It is concluded that at least two parent bodies are likely sources for the basaltic achondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19780034366&hterms=Peridots&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DPeridots','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19780034366&hterms=Peridots&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DPeridots"><span id="translatedtitle">Shock-produced <span class="hlt">olivine</span> glass - First observation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jeanloz, R.; Ahrens, T. J.; Lally, J. S.; Nord, G. L., Jr.; Christie, J. M.; Heuer, A. H.</p> <p>1977-01-01</p> <p>Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, /Mg(0.88)Fe(0.12)/2SiO4, recovered from peak pressures of about 56 billion pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation of <span class="hlt">olivine</span> glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that <span class="hlt">olivine</span> glass may be formed as a result of shock at pressures above about 50 to 55 billion pascals and that further TEM observations of naturally shocked <span class="hlt">olivines</span> may demonstrate the presence of glass.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992Metic..27R.256M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992Metic..27R.256M"><span id="translatedtitle">Constraints to the Formation of Matrix Reduced <span class="hlt">Olivine</span> in Yamato-691 (EH3) Chondrite: Implications for the Evolution of EH Chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsunami, S.; El Goresy, A.</p> <p>1992-07-01</p> <p>In order to understand the origin of oxidized components in enstatite chondrites, matrix reduced <span class="hlt">olivine</span> (RO) (<~60 micrometers in diameter) in Yamato-691 (EH3) chondrite has been examined in detail using EPMA. It commonly shows a lamellar structure, composed of alternation (with the spacing of about 1 micrometer) of "reduced <span class="hlt">olivine</span>," which is a mixture of forsterite, metallic Fe, and probably unreacted <span class="hlt">olivine</span> (relict), and sub-grain boundaries (SB) partly filled with decomposition products (Fe-metal, troilite, enstatite, and siliceous melt) due to reduction, strongly suggesting that the reduction of high-FeO <span class="hlt">olivine</span> took place along SB (Boland and Duba, 1986). The presence of RO with bended SB is also suggestive of plastic deformation of the <span class="hlt">olivine</span> before reduction. We estimated the rate of reduction of (Mg,Fe)-<span class="hlt">olivine</span> as a function of temperature, composition of <span class="hlt">olivine</span> (X(sub)Fe) and PO(sub)2 of reducing gas. We assumed that PO(sub)2 of the reducing gas was buffered by Si-bearing Fe-Ni metal + quartz assemblage. A mean Si- and Ni-contents of kamacite in Y-691 (Si=2.09 wt%; Ni=2.90 wt%) was adopted (El Goresy et al., 1988). To form RO with the SB spacing of 1 micrometer within 10^6-7 yr, which is a typical time-scale of thermal metamorphism at shallow parts of meteorite parent bodies (Wood, 1979), the temperature during reduction must have exceeded 700 K. From these results, the formational history of matrix RO and other coexisting phases in Y-691 could be summarized as follows: (1) High-FeO <span class="hlt">chondrule</span> <span class="hlt">olivines</span> crystallized in <span class="hlt">chondrule</span> melts enriched in oxidized components. (2a) A severe impact process deformed them plastically and generated numerous dislocations (>10^9/cm^2) in them. (2b) Post-shock high-T (>~1100 K) annealing process formed SB in them due to dislocation climb. (3) The <span class="hlt">olivine</span> grains were then mixed with E-chondritic materials containing at least both Si-bearing Fe- Ni metals and silica. (4) During metamorphism and/or impact heating process (T>~700 K), reduction of the <span class="hlt">olivine</span> proceeded along SB to precipitate reduction products. (5) After reduction, the ROs were comminuted to grain sizes less than ~60 micrometers. (6) Finally, the fine- grained ROs were assembled with other E-chondritic components (e.g., sulfides) to form Y-691 chondrite at temperatures lower than ~500 degrees C (Nagel, 1991). Boland J.N. and Duba A.G. (1986) Jour. Geophys. Res. 91, 4711- 4722. El Goresy A. et al. (1988) Proc. NIPR Symp. Antarct. Meteorites 13th, 65-101. Nagel H.-J. (1991) Ph.D. Thesis, Univ. of Heidelberg, 117 pp. Wood J.A. (1979) In Asteroids (ed. T. Gehrels), pp. 849-891. Univ. Arizona Press, Tucson, Arizona.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140012796','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140012796"><span id="translatedtitle">Contrasting Size Distributions of <span class="hlt">Chondrules</span> and Inclusions in Allende CV3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fisher, Kent R.; Tait, Alastair W.; Simon, Jusin I.; Cuzzi, Jeff N.</p> <p>2014-01-01</p> <p>There are several leading theories on the processes that led to the formation of chondrites, e.g., sorting by mass, by X-winds, turbulent concentration, and by photophoresis. The juxtaposition of refractory inclusions (CAIs) and less refractory <span class="hlt">chondrules</span> is central to these theories and there is much to be learned from their relative size distributions. There have been a number of studies into size distributions of particles in chondrites but only on relatively small scales primarily for <span class="hlt">chondrules</span>, and rarely for both Calcium Aluminum-rich Inclusions (CAIs) and <span class="hlt">chondrules</span> in the same sample. We have implemented macro-scale (25 cm diameter sample) and high-resolution microscale sampling of the Allende CV3 chondrite to create a complete data set of size frequencies for CAIs and <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020046279&hterms=nettle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dnettle','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020046279&hterms=nettle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dnettle"><span id="translatedtitle">Recycled Chondroids in LEW86018: A Petrographic Study of <span class="hlt">Chondrule</span> Precursors</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nettles, J. W.; Lofgren, G. E.; McSween, H. Y., Jr.</p> <p>2002-01-01</p> <p>Chondroids are any kind of nebular particle that would melt to become <span class="hlt">chondrules</span>. We describe the petrography and basic chemistry of chondroids in LEW86018 (L3.1). Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996LPI....27..207C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996LPI....27..207C"><span id="translatedtitle">Boron and Lithium Isotope Variations in <span class="hlt">Chondrules</span>: The Signature of Presolar Nucleosynthesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chaussidon, M.; Robert, F.</p> <p>1996-03-01</p> <p>We report here the preliminary results of tests concerning two major implications of the boron isotope variations that were recently found in meteoritic <span class="hlt">chondrules</span> (Chaussidon and Robert 1995, Nature 374, 337-339). (1) Freshly nucleosynthetized boron with variable 11B/10B ratios must have been preserved as solid grains in the solar nebula and implanted or embedded in the newly formed <span class="hlt">chondrules</span>. Therefore, <span class="hlt">chondrules</span> cooling rates do not allow a complete isotopic homogenisation which can be tested experimentally. (2) Another element, lithium, is also formed by the spallogenic reactions occurring in the presolar cloud with a spallogenic isotopic ratio (7Li/6Li) between 2 and 5 according to different models, which is lower than the bulk solar system ratio of ~12.5. Therefore, a negative correlation between the isotopic compositions of Li and B should be present in <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011823','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011823"><span id="translatedtitle">Different radiation and metamorphic history of the Kainsaz CO 3.2 <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kashkarov, L. L.; Kalinina, G. V.</p> <p>1993-01-01</p> <p>Track and thermoluminescence parameters in <span class="hlt">chondrules</span> from the Kainsaz CO 3.2 chondrite have been studied. Obtained results elucidate their individual shock-thermal history and the early pre-accretion stage of the meteorite parent body formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19840043308&hterms=Spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DSpinel','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19840043308&hterms=Spinel&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DSpinel"><span id="translatedtitle">Origin of spinel-rich <span class="hlt">chondrules</span> and inclusions in carbonaceous and ordinary chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kornacki, A. S.; Fegley, B., Jr.</p> <p>1984-01-01</p> <p>The evaluation of three models of the origin of spinel-rich <span class="hlt">chondrules</span> and inclusions presented here includes new calculations of the major-element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval. Condensation calculations show that spinel-rich <span class="hlt">chondrules</span> did not crystallize from metastable liquid condensates, and that spinel-rich inclusions are not aggregates of refractory nebular condensates. It is proposed that spinel-rich objects are fractionated distillation residues of small aggregates of primitive dust that lost Ca, Si-rich partial melts by evaporation, ablation, or splashing during collisions. This model also explains why spinel-rich <span class="hlt">chondrules</span> and inclusions (1) are usually smaller than melilite-rich <span class="hlt">chondrules</span> and inclusions; (2) often have highly fractionated trace-element compositions; and (3) usually do not contain Pt-metal nuggets even when they are more enriched in the Pt-group metals than nugget-bearing melilite-rich objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030110823&hterms=CAIS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DCAIS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030110823&hterms=CAIS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DCAIS"><span id="translatedtitle">Al-rich <span class="hlt">Chondrules</span>: Petrologic Basis for Their Diversity, and Relation to Type C CAIs</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>MacPherson, G. J.; Huss, G. R.</p> <p>2003-01-01</p> <p>Al-rich <span class="hlt">chondrules</span> share mineralogical and chemical properties with, and are intermediate in a volatility sense between, CAIs and ferromagnesian <span class="hlt">chondrules</span>. In some way they must be petrogenetic links between the two. A recent upsurge of interest in Al-rich <span class="hlt">chondrules</span> is due to their constituent plagioclase feldspar and Al-rich glass being amenable to successful ion microprobe searches for radiogenic Mg-26, the decay product of Al-26 (t(sub 1/2) = 720,000 y). This has allowed estimates to be made of the time duration between CAI formation and the onset of Al-rich (and possibly, by extension, ferromagnesian) <span class="hlt">chondrule</span> formation, on the order of 1.5-2.5 million years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5148T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5148T"><span id="translatedtitle">Redistribution of <span class="hlt">Chondrules</span> and Matrix Grains in the Mokoia Chondrite Parent Body: A Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomeoka, K.; Ohnishi, I.</p> <p>2015-07-01</p> <p>Based on our recent studies of the Mokoia CV3 chondrite, we propose a model that the lithology of this meteorite formed through redistribution of <span class="hlt">chondrules</span> and matrix grains in the meteorite parent body.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005GeCoA..69.1873K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005GeCoA..69.1873K"><span id="translatedtitle">Origin of low-Ca pyroxene in amoeboid <span class="hlt">olivine</span> aggregates: Evidence from oxygen isotopic compositions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krot, Alexander N.; Fagan, Timothy J.; Nagashima, Kazuhide; Petaev, Michael I.; Yurimoto, Hisayoshi</p> <p>2005-04-01</p> <p>Amoeboid <span class="hlt">olivine</span> aggregates (AOAs) in primitive carbonaceous chondrites consist of forsterite (Fa <2), Fe,Ni-metal, spinel, Al-diopside, anorthite, and rare gehlenitic melilite (Åk <15). ˜10% of AOAs contain low-Ca pyroxene (Fs 1-3Wo 1-5) that is in corrosion relationship with forsterite and is found in three major textural occurrences: ( i) thin (<15 μm) discontinuous layers around forsterite grains or along forsterite grain boundaries in AOA peripheries; ( ii) 5-10-μm-thick haloes and subhedral grains around Fe,Ni-metal nodules in AOA peripheries, and ( iii) shells of variable thickness (up to 70 μm), commonly with abundant tiny (3-5 μm) inclusions of Fe,Ni-metal grains, around AOAs. AOAs with the low-Ca pyroxene shells are compact and contain euhedral grains of Al-diopside surrounded by anorthite, suggesting small (10%-20%) degree of melting. AOAs with other textural occurrences of low-Ca pyroxene are rather porous. Forsterite grains in AOAs with low-Ca pyroxene have generally 16O-rich isotopic compositions (Δ 17O < -20‰). Low-Ca pyroxenes of the textural occurrences ( i) and ( ii) are 16O-enriched (Δ 17O < -20‰), whereas those of ( iii) are 16O-depleted (Δ 17O = -6‰ to -4‰). One of the extensively melted (>50%) objects is texturally and mineralogically intermediate between AOAs and Al-rich <span class="hlt">chondrules</span>. It consists of euhedral forsterite grains, pigeonite, augite, anorthitic mesostasis, abundant anhedral spinel grains, and minor Fe,Ni-metal; it is surrounded by a coarse-grained igneous rim largely composed of low-Ca pyroxene with abundant Fe,Ni-metal-sulfide nodules. The mineralogical observations suggest that only spinel grains in this igneous object were not melted. The spinel is 16O-rich (Δ 17O ˜ -22‰), whereas the neighboring plagioclase mesostasis is 16O-depleted (Δ 17O ˜ -11‰). We conclude that AOAs are aggregates of solar nebular condensates (forsterite, Fe,Ni-metal, and CAIs composed of Al-diopside, anorthite, spinel, and ±melilite) formed in an 16O-rich gaseous reservoir, probably CAI-forming region(s). Solid or incipiently melted forsterite in some AOAs reacted with gaseous SiO in the same nebular region to form low-Ca pyroxene. Some other AOAs appear to have accreted 16O-poor pyroxene-normative dust and experienced varying degrees of melting, most likely in <span class="hlt">chondrule</span>-forming region(s). The most extensively melted AOAs experienced oxygen isotope exchange with 16O-poor nebular gas and may have been transformed into <span class="hlt">chondrules</span>. The original 16O-rich signature of the precursor materials of such <span class="hlt">chondrules</span> is preserved only in incompletely melted grains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120001957','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120001957"><span id="translatedtitle">Mineralogy of Stardust Track 112 Particle: Relation to Amoeboid <span class="hlt">Olivine</span> Aggregates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Komatsu, M.; Fagan, T.; Mikouchi, T.; Miyamoto, M.; Zolensky, M.; Ohsumi, K.</p> <p>2012-01-01</p> <p>The successful analysis of comet 81P/Wild 2 particles returned by the Stardust mission has revealed that the Wild 2 dust contains abundant silicate grains that are much larger than interstellar grains and appear to have formed in the inner regions of the solar nebula [1]. Wild 2 particles include minerals which are isotopically and mineralogically similar to CAIs [e.g., 2, 3] and <span class="hlt">chondrules</span> [e.g., 4] in chondrites. In addition, particles similar to amoeboid <span class="hlt">olivine</span> aggregates (AOAs) also have been discovered [5, 6,7]. C2067,2,112,1 is a terminal particle recovered from track #112 (T112). Nakamura-Messenger et al. [7] showed that the forsterite grain in T112 has O-16 enrichment of approximately 40 0/00 (vs. SMOW) and possibly formed together with AOAs. In this study, we have examined the mineralogy of the T112 particle and compared the possible relationships between T112 and AOAs in primitive meteorites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..267..364H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..267..364H"><span id="translatedtitle">A new mechanism for <span class="hlt">chondrule</span> formation: Radiative heating by hot planetesimals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herbst, William; Greenwood, James P.</p> <p>2016-03-01</p> <p>We propose that <span class="hlt">chondrules</span> are formed by radiative heating of pre-existing dust clumps during close fly-bys of planetesimals with incandescent lava at their surfaces. We show that the required temperatures and cooling rates are easily achieved in this scenario and discuss how it is consistent with bulk aspects of chondritic meteorites, including complementarity and the co-mingling of FeO-poor and FeO-rich <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24735106','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24735106"><span id="translatedtitle">Enhanced <span class="hlt">olivine</span> carbonation within a basalt as compared to single-phase experiments: reevaluating the potential of CO2 mineral sequestration.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sissmann, Olivier; Brunet, Fabrice; Martinez, Isabelle; Guyot, François; Verlaguet, Anne; Pinquier, Yves; Daval, Damien</p> <p>2014-05-20</p> <p>Batch experiments were conducted in water at 150 °C and PCO2 = 280 <span class="hlt">bar</span> on a Mg-rich tholeiitic basalt (9.3 wt % MgO and 12.2 wt % CaO) composed of <span class="hlt">olivine</span>, Ti-magnetite, plagioclase, and clinopyroxene. After 45 days of reaction, 56 wt % of the initial MgO had reacted with CO2 to form Fe-bearing magnesite, (Mg0.8Fe0.2)CO3, along with minor calcium carbonates. The substantial decrease in <span class="hlt">olivine</span> content upon carbonation supports the idea that ferroan magnesite formation mainly follows from <span class="hlt">olivine</span> dissolution. In contrast, in experiments performed under similar run durations and P/T conditions with a San Carlos <span class="hlt">olivine</span> separate (47.8 wt % MgO) of similar grain size, only 5 wt % of the initial MgO content reacted to form Fe-bearing magnesite. The overall carbonation kinetics of the basalt was enhanced by a factor of ca. 40. This could be explained by differences in the chemical and textural properties of the secondary silica layer that covers reacted <span class="hlt">olivine</span> grains in both types of sample. Consequently, laboratory data obtained on <span class="hlt">olivine</span> separates might yield a conservative estimate of the true carbonation potential of <span class="hlt">olivine</span>-bearing basaltic rocks. PMID:24735106</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930055819&hterms=magnetite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmagnetite','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930055819&hterms=magnetite&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmagnetite"><span id="translatedtitle">Magnetite-sulfide <span class="hlt">chondrules</span> and nodules in CK carbonaceous chondrites - Implications for the timing of CK oxidation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rubin, Alan E.</p> <p>1993-01-01</p> <p>CK carbonaceous chondrites contain rare (about 0.1 vol pct) magnetite-sulfide <span class="hlt">chondrules</span> that range from about 240 to 500 microns in apparent diameter and have ellipsoidal to spheroidal morphologies, granular textures, and concentric layering. They resemble the magnetite-sulfide nodules occurring inside mafic silicate <span class="hlt">chondrules</span> in CK chondrites. It seems likely that the magnetite-sulfide <span class="hlt">chondrules</span> constitute the subset of magnetite-sulfide nodules that escaped as immiscible droplets from their molten silicate <span class="hlt">chondrule</span> hosts during <span class="hlt">chondrule</span> formation. The intactness of the magnetite-sulfide <span class="hlt">chondrules</span> and nodules implies that oxidation of CK metal occurred before agglomeration. Hence, the pervasive silicate darkening of CK chondrites was caused by the shock mobilization of magnetite and sulfide, not metallic Fe-Ni and sulfide as in shock-darkened ordinary chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050173926','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050173926"><span id="translatedtitle">I-Xe Dating: The Time Line of <span class="hlt">Chondrule</span> Formation and Metamorphism in LL Chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pravdivtseva, O. V.; Hohenberg, C. M.; Meshik, A. P.</p> <p>2005-01-01</p> <p>Refractory inclusions, considered to be the oldest solids formed in the solar nebula. (4567.2 0.6 Ma) [1], are common in many carbonaceous and in some ordinary and enstatite chondrites. High-precision Pb- Pb ages for CAI s and <span class="hlt">chondrules</span> (from different meteorites) suggested that <span class="hlt">chondrule</span> formation appeared to have started about 2 Ma later than that of CAIs [1]. However, recent 26Al/26Mg data suggest simultaneous formation of CAI s and <span class="hlt">chondrules</span> in Allende [2]. The I-Xe ages of CAI s in Allende are about 2 Ma younger than the I-Xe ages of Allende <span class="hlt">chondrules</span> [3] but, like all chronometers, the I-Xe system records closure time of its particular host phase. In the case of Allende CAI s, the major iodine-bearing phase is sodalite, a secondary phase presumably formed by aqueous alteration, so I-Xe reflects the post-formational processes in these objects. In <span class="hlt">chondrules</span> the iodine host phases vary and can reflect formation and/or alteration but, to put <span class="hlt">chondrule</span> ages on a quantative basis, some problems should first be addressed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20050202069&hterms=SIMUlation+micrometeorite+impacts&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSIMUlation%2Bmicrometeorite%2Bimpacts','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20050202069&hterms=SIMUlation+micrometeorite+impacts&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSIMUlation%2Bmicrometeorite%2Bimpacts"><span id="translatedtitle">A Chemical Model of Micrometeorite Impact into <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sheffer, A. A.; Melosh, H. J.</p> <p>2005-01-01</p> <p>Laboratory simulations of space weathering using laser irradiation have been successful in reproducing space weathering characteristics such as the reduction of <span class="hlt">olivine</span> to form nanophase iron particles. However, the chemistry of the reduction of Fe2+ in <span class="hlt">olivine</span> to Fe metal has not been fully explored. We present a thermodynamic model of <span class="hlt">olivine</span> undergoing post-impact cooling and decompression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/907835','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/907835"><span id="translatedtitle">Constraints on the Origin of <span class="hlt">Chondrules</span> and CAIs from Short-Lived and Long-Lived Radionuclides</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kita, N T; Huss, G R; Tachibana, S; Amelin, Y; Nyquist, L E; Hutcheon, I D</p> <p>2005-10-24</p> <p>The high time resolution Pb-Pb ages and short-lived nuclide based relative ages for CAIs and <span class="hlt">chondrules</span> are reviewed. The solar system started at 4567.2 {+-} 0.6Ma inferred from the high precision Pb-Pb ages of CAIs. Time scales of CAIs ({le}0.1Myr), <span class="hlt">chondrules</span> (1-3Myr), and early asteroidal differentiation ({ge}3Myr) inferred from {sup 26}Al relative ages are comparable to the time scale estimated from astronomical observations of young star; proto star, classical T Tauri star and week-lined T Tauri star, respectively. Pb-Pb ages of <span class="hlt">chondrules</span> also indicate <span class="hlt">chondrule</span> formation occur within 1-3 Myr after CAIs. Mn-Cr isochron ages of <span class="hlt">chondrules</span> are similar to or within 2 Myr after CAI formation. <span class="hlt">Chondrules</span> from different classes of chondrites show the same range of {sup 26}Al ages in spite of their different oxygen isotopes, indicating that <span class="hlt">chondrule</span> formed in the localized environment. The {sup 26}Al ages of <span class="hlt">chondrules</span> in each chondrite class show a hint of correlation with their chemical compositions, which implies the process of elemental fractionation during <span class="hlt">chondrule</span> formation events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015934','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015934"><span id="translatedtitle">Transmission electron microscopy of subsolidus oxidation and weathering of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Banfield, J.F.; Veblen, D.R.; Jones, B.F.</p> <p>1990-01-01</p> <p><span class="hlt">Olivine</span> crystals in basaltic andesites which crop out in the Abert Rim, south-central Oregon have been studied by high-resolution and analytical transmission electron microscopy. The observations reveal three distinct assemblages of alteration products that seem to correspond to three episodes of <span class="hlt">olivine</span> oxidation. The <span class="hlt">olivine</span> crystals contain rare, dense arrays of coherently intergrown Ti-free magnetite and inclusions of a phase inferred to be amorphous silica. We interpret this first assemblage to be the product of an early subsolidus oxidation event in the lava. The second <span class="hlt">olivine</span> alteration assemblage contains complex ordered intergrowths on (001) of forsterite-rich <span class="hlt">olivine</span> and laihunite (distorted <span class="hlt">olivine</span> structure with Fe3+ charge balanced by vacancies). Based on experimental results for laihunite synthesis (Kondoh et al. 1985), these intergrowths probably formed by <span class="hlt">olivine</span> oxidation between 400 and 800??C. The third episode of alteration involves the destruction of <span class="hlt">olivine</span> by low-temperature hydrothermal alteration and weathering. Elongate etch-pits and channels in the margins of fresh <span class="hlt">olivine</span> crystals contain semi-oriented bands of smectite. <span class="hlt">Olivine</span> weathers to smectite and hematite, and subsequently to arrays of oriented hematite crystals. The textures resemble those reported by Eggleton (1984) and Smith et al. (1987). We find no evidence for a metastable phase intermediate between <span class="hlt">olivine</span> and smectite ("M" - Eggleton 1984). The presence of laihunite exerts a strong control on the geometry of <span class="hlt">olivine</span> weathering. Single laihunite layers and laihunite-forsteritic <span class="hlt">olivine</span> intergrowths increase the resistance of crystals to weathering. Preferential development of channels between laihunite layers occurs where growth of laihunite produced compositional variations in <span class="hlt">olivine</span>, rather than where coherency-strain is associated with laihunite-<span class="hlt">olivine</span> interfaces. ?? 1990 Springer-Verlag.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70022620','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70022620"><span id="translatedtitle">Bleached <span class="hlt">chondrules</span>: Evidence for widespread aqueous processes on the parent asteroids of ordinary chondrites</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Grossman, J.N.; Alexander, C.M. O'D.; Wang, Jingyuan; Brearley, A.J.</p> <p>2000-01-01</p> <p>We present the first detailed study of a population of texturally distinct <span class="hlt">chondrules</span> previously described by Kurat (1969), Christophe Michel-Levy (1976), and Skinner et al. (1989) that are sharply depleted in alkalis and Al in their outer portions. These 'bleached' <span class="hlt">chondrules</span>, which are exclusively radial pyroxene and cryptocrystalline in texture, have porous outer zones where mesostasis has been lost. Bleached <span class="hlt">chondrules</span> are present in all type 3 ordinary chondrites and are present in lower abundances in types 4-6. They are most abundant in the L and LL groups, apparently less common in H chondrites, and absent in enstatite chondrites. We used x-ray mapping and traditional electron microprobe techniques to characterize bleached <span class="hlt">chondrules</span> in a cross section of ordinary chondrites. We studied bleached <span class="hlt">chondrules</span> from Semarkona by ion microprobe for trace elements and H isotopes, and by transmission electron microscopy. <span class="hlt">Chondrule</span> bleaching was the result of low-temperature alteration by aqueous fluids flowing through fine-grained chondrite matrix prior to thermal metamorphism. During aqueous alteration, interstitial glass dissolved and was partially replaced by phyllosilicates, troilite was altered to pentlandite, but pyroxene was completely unaffected. Calcium-rich zones formed at the inner margins of the bleached zones, either as the result of the early stages of metamorphism or because of fluid-<span class="hlt">chondrule</span> reaction. The mineralogy of bleached <span class="hlt">chondrules</span> is extremely sensitive to thermal metamorphism in type 3 ordinary chondrites, and bleached zones provide a favorable location for the growth of metamorphic minerals in higher petrologic types. The ubiquitous presence of bleached <span class="hlt">chondrules</span> in ordinary chondrites implies that they all experienced aqueous alteration early in their asteroidal histories, but there is no relationship between the degree of alteration and metamorphic grade. A correlation between the oxidation state of chondrite groups and their degree of aqueous alteration is consistent with the source of water being either accreted ices or water released during oxidation of organic matter. Ordinary chondrites were probably open systems after accretion, and aqueous fluids may have carried volatile elements with them during dehydration. Individual radial pyroxene and cryptocrystalline <span class="hlt">chondrules</span> were certainly open systems in all chondrites that experienced aqueous alteration leading to bleaching.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70009984','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70009984"><span id="translatedtitle">Shock-produced <span class="hlt">olivine</span> glass: First observation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jeanloz, R.; Ahrens, T.J.; Lally, J.S.; Nord, G.L., Jr.; Christie, J.M.; Heuer, A.H.</p> <p>1977-01-01</p> <p>Transmission electron microscope (TEM) observations of an experimentally shock-deformed single crystal of natural peridot, (Mg0.88Fe 0.12SiO4 recovered from peak pressures of about 56 ?? 109 pascals revealed the presence of amorphous zones located within crystalline regions with a high density of tangled dislocations. This is the first reported observation ofolivine glass. The shocked sample exhibits a wide variation in the degree of shock deformation on a small scale, and the glass appears to be intimately associated with the highest density of dislocations. This study suggests that <span class="hlt">olivine</span> glass may be formed as a result of shock at pressures above about 50 to 55 ?? 109 pascals and that further TEM observations of naturally shocked <span class="hlt">olivines</span> may demonstrate the presence of glass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995GeCoA..59.2095Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995GeCoA..59.2095Y"><span id="translatedtitle">Experimental study of high temperature oxygen isotope exchange during <span class="hlt">chondrule</span> formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yang; Hewins, Roger H.; Clayton, Robert N.; Mayeda, Toshiko K.</p> <p>1995-05-01</p> <p>Laboratory experiments have been conducted to determine rates and other details of the oxygen isotopic exchange process between meteoritic material and water vapor. The meteoritic samples were totally or partially melted, or completely unmelted. The furnace atmosphere consisted of water vapor and hydrogen, and was diluted with helium for some of the experiments. Both isothermal and flash heating experiments were performed. Extensive oxygen isotope exchange has been observed between <span class="hlt">chondrule</span> analogue melt and surrounding dilute water vapor, such that 50% equilibration occurs in charges near their liquidus in five minutes or less. The principal rate-limiting mechanism of the exchange is diffusion within the melt. The initial exchange rate also depends on the partial pressure of water, which points to the effect of the surface exchange process. The kinetics of the surface reaction have not been determined due to the restrictions of our experimental configuration. The extent of exchange observed in short time isothermal runs and in flash heating runs suggests that much of the isotopic variability of natural <span class="hlt">chondrules</span> can be produced during <span class="hlt">chondrule</span>-forming events by the gas/melt isotopic exchange processes. However, due to the very low gas densities in the nebula, multiple melting events might be needed to produce the <span class="hlt">chondrules</span> with highly exchanged isotopic compositions. For a partially melted sample, as is often the case in natural <span class="hlt">chondrules</span>, the rate of isotopic change of the bulk sample is determined by the exchange rates of both the melt and unmelted relict minerals. If the melt and relict minerals have a large difference in isotopic compositions, the exchange trajectory becomes markedly nonlinear. These observations are consistent with the observed dependence of extent of exchange in natural <span class="hlt">chondrules</span> on the degree of melting, and imply that for each of the linear trends on the three-isotope diagram observed for natural <span class="hlt">chondrules</span>, only two initial isotopic reservoirs might have existed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982tcsc.meet..142G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982tcsc.meet..142G"><span id="translatedtitle">Evaluation of <span class="hlt">olivine</span> refractories for TES</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gay, B. M.; Cochrane, R. L.; Palmour, H., III; Paisley, M. J.</p> <p>1982-02-01</p> <p>The principal objectives of this program are to (1) experimentally determine the degree of improvement in thermal and mechanical performance that can be obtained with an <span class="hlt">olivine</span> thermal storage brick made of domestic materials using advanced processing techniques compared with state-of-the-art as represented by commercial European bricks, (2) conduct an assessment of existing German ceramic process technology and determine its adaptability to domestic raw materials and manufacturing practices, and (3) investigate, on a limited basis, method for further improvement of domestic-<span class="hlt">olivine</span> brick. To date, accomplishments include (1) installation of improved, computer-based instrumentation, (2) the use of this system to determine performance characteristics of a set of heat storage refractories under cyclic use conditions, (3) acquisition of the services of a knowledgeable European consultant, (4) continued lab-scale process/property optimization studies, and (5) comparative testing of <span class="hlt">olivine</span>-based and magnesite-based heat storage refractories in the calorimetric test facility at Purdue University.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150002979','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150002979"><span id="translatedtitle">Na, K-Rich Rim Around a <span class="hlt">Chondrule</span> in Unequilibrated Ordinary Chondrite Lew 86018 (L3.1)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mishra, R. K.; Simon, J. I.; Ross, D. K.; Needham, A. W.; Messenger, S.; Keller, L. P.; Han, J.; Marhas, K. K.</p> <p>2015-01-01</p> <p>Ordinary chondrites represent the most abundant early Solar system extra-terrestrial (approximately 85% abundance) material available for laboratory studies and expectedly record the most extensive range of alterations effects from unmetamorphosed chondritic material to the highest temperatures of thermal metamorphism. The least metamorphosed chondrites belonging to petrologic type 3, the so called unequili-brated ordinary chondrites (UOCs), provide insights into alteration that happened during the primeval, ear-liest stage of Solar system formation. The higher grade petrologic types 4-6 ordinary chondrites on the other hand document up to near textural equilibrium (in type 6) extensive thermal metamorphism consisting of minerals and phases providing evidence of equilibration of heterogeneous mineral composition, solid-state recrystallization. Despite being the most abundant, the effect of alteration is less explicitly understood in ordinary chondrites (even less in UOCs) compared to other groups (e.g. CV, CO, CR). Additionally, the relationship between metasomatism (also referred as aqueous alteration or fluid-assisted metamorphism) and metamorphism (primarily thermal driven) has not been studied and alterations in the ordinary chondrites have been considered to have occurred in absence of fluids in general. Despite this conventional view, UOCs of lowest grades (3.0-3.2) show some evidence of low temperature (approximately 200 C), fluid assisted metamorphism in the form of the presence of phyllosilicates, ferroan <span class="hlt">olivine</span>, and magnetites in their matrices and occasionally in <span class="hlt">chondrules</span>. Here, we present petrographic and mineralogical studies of UOC, Lewis Hills (LEW) 86018 to further our understanding of the extent and relative importance of metasomatism and/or metamorphism in UOCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V51E1770G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V51E1770G"><span id="translatedtitle">Mechanisms and Timescales for Reequilibration of Water in <span class="hlt">Olivine</span>-Hosted Melt Inclusions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaetani, G. A.; O'Leary, J. A.; Shimizu, N.</p> <p>2009-12-01</p> <p>Water solubility in silicate melts drops substantially with decreasing pressure. A magma containing several weight % dissolved H2O in the shallow crust is left with only a few thousand ppm following eruption. <span class="hlt">Olivine</span>-hosted melt inclusions provide information on the pre-eruptive H2O contents of degassed magmas because the strength of the host crystal protects the melt inclusion from the decompression experienced by the entraining magma. The principal uncertainty involved with interpreting pre-eruptive H2O concentrations from melt inclusions is the potential for diffusive loss or gain of H+ (protons) through the host <span class="hlt">olivine</span>. It has been proposed that Fe redox reactions severely limit the proton flux, and that episodes of H2O loss/gain are easily identifiable through changes in oxidation state of the inclusion [1,2]. Results from hydration and dehydration experiments carried out on natural inclusion-bearing <span class="hlt">olivines</span> and analyzed by SIMS confirm that H2O re-equilibratrion occurs rapidly via proton diffusion through the host <span class="hlt">olivine</span>, and demonstrate that re-equilibration of oxygen fugacity within the inclusions occurs on comparable timescales via diffusion of point defects. Therefore, an <span class="hlt">olivine</span>-hosted melt inclusion only provides a reliable record for the H2O content of the external melt with which it most recently equilibrated. Hydration experiments were performed on <span class="hlt">olivines</span> from Puu Wahi, a scoria cone on the NE rift zone of Mauna Loa volcano. Melt inclusions initially containing 0.36±0.05 wt% H2O were held at 1 GPa and 1250°C in water enriched in 18O (18O/ΣO = 0.977) and D (2H/ΣH = 0.998) to map the transport of protons and oxygen during equilibration of melt inclusions with an external fluid. Dehydration experiments were carried out for 1 to 18 hrs at 1 <span class="hlt">bar</span> and 1250 °C on inclusion-bearing <span class="hlt">olivines</span> in scoria erupted from Cerro Negro volcano, Nicaragua, in 1999. The initial concentration of H2O in these melt inclusions is uniformly high (3.6±0.6 wt%). All run products were analyzed by SIMS on the Cameca 1280 ion microprobe at WHOI. Results from our experiments confirm that the mechanism for loss or gain of H2O from <span class="hlt">olivine</span>-hosted melt inclusions is lattice diffusion of protons. This process leaves behind an O2- for every 2 protons lost, and scavenges an O2- for every 2 protons gained, producing an increase or decrease, respectively, of the fugacity of oxygen within the inclusion. However, H2O loss/gain for <span class="hlt">olivine</span>-hosted melt inclusions is coupled with point defect-mediated oxygen fugacity re-equilibration. Therefore, Fe redox reactions do not limit either the amount or rate of water loss or gain by the inclusion. The H2O concentration of an <span class="hlt">olivine</span>-hosted melt inclusion can change rapidly, and that change is not recorded by the oxygen fugacity of the melt. References: [1] A. V. Sobolev, L. V. Danyushevsky, J Petrol 35, 1183 (1994); [2] L. V. Danyushevsky, A. W. McNeill, A. V. Sobolev, Chem Geol 183, 5 (2002).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..258..483L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..258..483L"><span id="translatedtitle">Exploring exogenic sources for the <span class="hlt">olivine</span> on Asteroid (4) Vesta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Corre, Lucille; Reddy, Vishnu; Sanchez, Juan A.; Dunn, Tasha; Cloutis, Edward A.; Izawa, Matthew R. M.; Mann, Paul; Nathues, Andreas</p> <p>2015-09-01</p> <p>The detection of <span class="hlt">olivine</span> on Vesta is interesting because it may provide critical insights into planetary differentiation early in our Solar System's history. Ground-based and Hubble Space Telescope (HST) observations of Asteroid (4) Vesta have suggested the presence of <span class="hlt">olivine</span> on the surface. These observations were reinforced by the discovery of <span class="hlt">olivine</span>-rich HED meteorites from Vesta in recent years. However, analysis of data from NASA's Dawn spacecraft has shown that this "<span class="hlt">olivine</span>-bearing unit" is actually impact melt in the ejecta of Oppia crater. The lack of widespread mantle <span class="hlt">olivine</span>, exposed during the formation of the 19 km deep Rheasilvia basin on Vesta's South Pole, further complicated this picture. Ammannito et al. (Ammannito, E. et al. [2013a]. Nature 504, 122-125) reported the discovery of local scale <span class="hlt">olivine</span>-rich units in the form of excavated material from the mantle using the Visible and InfraRed spectrometer (VIR) on Dawn. These sites are concentrated in the walls and ejecta of craters Arruntia (10.5 km in diameter) and Bellicia (41.7 km in diameter), located in the northern hemisphere, 350-430 km from Rheasilvia basin's rim. Here we explore alternative sources for the <span class="hlt">olivine</span> in the northern hemisphere of Vesta by reanalyzing the data from the VIR instrument using laboratory spectral measurements of meteorites. Our rationale for using the published dataset was to bypass calibration issues and ensure a consistent dataset between the two studies. Our analysis of the VIR data shows that while the interpretation of their spectra as an <span class="hlt">olivine</span>-rich unit is correct, the nature and origin of that <span class="hlt">olivine</span> could be more complicated. We suggest that these <span class="hlt">olivine</span> exposures could also be explained by the delivery of <span class="hlt">olivine</span>-rich exogenic material. This hypothesis is supported by meteoritical evidence in the form of exogenic xenoliths containing significant amount of <span class="hlt">olivine</span> in some of the HED meteorites from Vesta. Previous laboratory work on HEDs show that potential sources of <span class="hlt">olivine</span> on Vesta could be different types of <span class="hlt">olivine</span>-rich meteorites, either primitive achondrites (acapulcoites, lodranites, ureilites), ordinary chondrites (H, L, LL), pallasites, or carbonaceous chondrites (e.g., CV). Based on our spectral band parameters analysis, the lack of correlation between the location of these <span class="hlt">olivine</span>-rich terrains and possible mantle-excavating events, and supported by observations of HED meteorites, we propose that a probable source for the <span class="hlt">olivine</span> seen in the northern hemisphere corresponds to remnants of impactors made of <span class="hlt">olivine</span>-rich meteorites. The best curve-matching results with laboratory spectra suggest these units are HED material mixed with either ordinary chondrites, or with some <span class="hlt">olivine</span>-dominated meteorites such as R-chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070003472','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070003472"><span id="translatedtitle">Turbulent Size Selection and Concentration of <span class="hlt">Chondrule</span>-Sized Objects: Reynolds Number Invariance and Implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cuzzi, J. N.; Hogan, R.; Dobrovolskis, A.; Paque, J.</p> <p>2006-01-01</p> <p>It is generally agreed that individual <span class="hlt">chondrules</span> formed as entities in a gaseous nebula prior to being accumulated into a meteorite parent body, within which they incur various forms of modification before arriving in our labs. While there are major unanswered questions about the properties of the nebula environment in which <span class="hlt">chondrules</span> formed, the process by which the most primitive meteorites are formed overwhelmingly from <span class="hlt">chondrules</span> must then be an aspect of "nebula processing". Textures in certain fragments of primitive meteorites might be summarized as being primarily <span class="hlt">chondrules</span> and clastic, <span class="hlt">chondrule</span>-sized, fragments of other minerals, each covered with a rim of fine dust with physical and chemical properties which are essentially independent of the composition and mineralogy of the underlying <span class="hlt">chondrule</span>. This (unfortunately rather rare) texture was called "primary accretionary texture" to reflect their belief that it precedes subsequent stages in which fragmentation, comminution, mixing, heating, and other forms of alteration occur on the parent body(-ies). The size distribution of these <span class="hlt">chondrules</span> and fragments, and the properties of their dusty rims, are key clues regarding the primary nebula accretion process. Even in the much more abundant meteorites which have clearly suffered internal mixing, abrasion, grinding, and even mineralogical alteration or replacement (due presumably to the collisional growth and heating process itself), key <span class="hlt">chondrule</span> properties such as mean size and density remain relatively well defined, and well defined rims persist in many cases. It has been our goal to infer the key nebula processes indirectly from the properties of these very earliest primitive meteorites by making use of a theoretical framework in which the nebula possesses a plausible level of isotropic turbulence. We have shown that turbulence has the property of concentrating one particular particle size by orders of magnitude, where the preferentially concentrated size depends primarily on the intensity of the turbulent kinetic energy (represented by the Reynolds number of the nebula). Specifically, the preferentially concentrated particle is that which has a stopping time equal to the turnover time of the smallest eddy. The intensity level of turbulence implied by <span class="hlt">chondrule</span> sizes can be maintained by even a small fraction of the energy released by the radially evolving disk (it must be noted that the details of how this transfer of energy actually occurs remain obscure, however).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16107841','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16107841"><span id="translatedtitle">Young <span class="hlt">chondrules</span> in CB chondrites from a giant impact in the early Solar System.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krot, Alexander N; Amelin, Yuri; Cassen, Patrick; Meibom, Anders</p> <p>2005-08-18</p> <p><span class="hlt">Chondrules</span>, which are the major constituent of chondritic meteorites, are believed to have formed during brief, localized, repetitive melting of dust (probably caused by shock waves) in the protoplanetary disk around the early Sun. The ages of primitive <span class="hlt">chondrules</span> in chondritic meteorites indicate that their formation started shortly after that of the calcium-aluminium-rich inclusions (4,567.2 +/- 0.7 Myr ago) and lasted for about 3 Myr, which is consistent with the dissipation timescale for protoplanetary disks around young solar-mass stars. Here we report the 207Pb-206Pb ages of <span class="hlt">chondrules</span> in the metal-rich CB (Bencubbin-like) carbonaceous chondrites Gujba (4,562.7 +/- 0.5 Myr) and Hammadah al Hamra 237 (4,562.8 +/- 0.9 Myr), which formed during a single-stage, highly energetic event. Both the relatively young ages and the single-stage formation of the CB <span class="hlt">chondrules</span> are inconsistent with formation during a nebular shock wave. We conclude that <span class="hlt">chondrules</span> and metal grains in the CB chondrites formed from a vapour-melt plume produced by a giant impact between planetary embryos after dust in the protoplanetary disk had largely dissipated. These findings therefore provide evidence for planet-sized objects in the earliest asteroid belt, as required by current numerical simulations of planet formation in the inner Solar System. PMID:16107841</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014LPICo1800.5005P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014LPICo1800.5005P"><span id="translatedtitle">2D Size Distribution of <span class="hlt">Chondrules</span> and Chondritic Fragments of an Ordinary Chondrite from Lut Desert (Iran)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pourkhorsandi, H.; Mirnejad, H.</p> <p>2014-09-01</p> <p>2D size measurement of <span class="hlt">chondrules</span> and chondiritic fragments of a meteorite from Lut desert of Iran is conducted. <span class="hlt">Chondrules</span> exhibit a size range of 55-1800 µm (average 437 µm). Chondiritic fragments show a size range of 46-1220 µm (average 261 µm).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5062E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5062E"><span id="translatedtitle">Formation of Na-Rich <span class="hlt">Chondrules</span> by Melting of Na-Rich and Condensed (Ultra)-Refractory Precursors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ebert, S.; Bischoff, A.</p> <p>2015-07-01</p> <p>We analyzed 33 Na-rich <span class="hlt">chondrules</span> (Na2O >4.0 wt%) from 15 different chondrites. These <span class="hlt">chondrules</span> must have formed by melting of precursors including Na-rich materials (like nepheline) as well as condensed (ultra)-refractory components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/980204','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/980204"><span id="translatedtitle">Experimental Deformation of <span class="hlt">Olivine</span> Single Crystals at Mantle Pressures and Temperatures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Raterron, P.; Amiguet, E; Chen, J; Li, L; Cordier, P</p> <p>2008-01-01</p> <p>Deformation experiments were carried out in a deformation-DIA high-pressure apparatus (D-DIA) on oriented San Carlos <span class="hlt">olivine</span> single crystals, at pressure (P) ranging from 3.5 to 8.5 GPa, temperature (T) from 1373 to 1673 K, and in poor water condition. Oxygen fugacity (fO2) was maintained within the <span class="hlt">olivine</span> stability field and contact with enstatite powder ensured an orthopyroxene activity aopx = 1. Two compression directions were tested, promoting either [1 0 0] slip alone or [0 0 1] slip alone in (0 1 0) crystallographic plane, here called, respectively, a-slip and c-slip. Constant applied stress (s) and specimen strain rates ({<span class="hlt">bar</span> {var_epsilon}}) were monitored in situ using time-resolved X-ray synchrotron diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of run products revealed that dislocation creep was responsible for sample deformation. Comparison of the obtained high-P deformation data with the data obtained at room-P by Bai et al. [Bai, Q., Mackwell, S.L., Kohlstedt D.L., 1991, High-temperature creep of <span class="hlt">olivine</span> single crystals. 1. Mechanical results for buffered samples, Journal of Geophysical Research, 96, 2441-2463] - on identical materials deformed at comparable T-sefO2-aopx conditions - allowed quantifying the P effect on a-slip and c-slip rheological laws. A slip transition with increasing pressure, from dominant a-slip to dominant c-slip, is documented. a-slip appears sensitive to pressure, which translates into the high activation volume V*{sub a} = 12 {+-} 4 cm{sup 3}/mol in the corresponding rheological law, while pressure has little effect on c-slip with V*{sub c} = 3 {+-} 4 cm{sup 3}/mol. These results may explain the discrepancy between <span class="hlt">olivine</span> low-P and high-P deformation data which has been debated in the literature for more than a decade.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993Metic..28..334B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993Metic..28..334B"><span id="translatedtitle">Meteorite Ablation Rinds as Analogs for the Origin of Rims on <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bunch, T.; Paque, J. M.; Reynolds, R.; Podolak, M.; Prialnik, D.</p> <p>1993-07-01</p> <p>Conventional wisdom holds that UOC <span class="hlt">chondrule</span> rims were formed in the nebula by dust accretion. Following the accretion stage, some investigators suggest that these porous rims were subjected to thermal alteration that ranged from sintering to melting [e. g., 1-3]. To understand the evolutionary history of <span class="hlt">chondrules</span> we need to ask: (1) What nebular mechanism(s) concentrated the dust for rapid accretion? (Addressed in a companion paper at this meeting [4]). (2) What thermal event(s) welded or melted the dust? (3) Is this dust solely responsible for the rim composition, or are some rims composed, in part, of the parent <span class="hlt">chondrule</span>? Production and/or modification of rims during atmospheric entry onto a parent body is a scenario that is testable by examination of ablation rinds produced on meteorites during entry into Earth's atmosphere. Comparison of ablation rind features with opaque rims on UOC <span class="hlt">chondrules</span> will indicate whether this is a viable method for the production of <span class="hlt">chondrule</span> rims. Terrestrial ablation rinds on UOCs and carbonaceous chondrites have been examined both texturally and chemically. Ablation rinds have these distinct characteristics: (1) The bulk composition of the rind is a reflection of the bulk chemistry of the host object, including Na, K, and P, but with the exception of much lower S. (2) Boundaries between unmelted bulk meteorite and rind silicates are physically sharp over distances of microns, similar to boundaries between rims and their <span class="hlt">chondrules</span>. However, compositional transition zones extend inward from the boundaries for 10s of microns. (3) Melted meteorite matrix in the rind is compositionally similar to unmelted matrix and is texturally and chemically similar to rims. (4) Mineral texture and chemistry at <span class="hlt">chondrule</span>/rim and meteorite/rind interfaces indicate significant thermal processing has occurred. For example, sulfides show high concentrations of included, more refractory phases at the melt interface with a corresponding loss of S. Overall, the comparison of ablation rinds with rims strongly suggests that opaque rims formed by melting of dusty accretion mantles. This melting event may have continued into the outer margins of host <span class="hlt">chondrules</span>, or may be restricted to the accreted dust. SEM examination of the boundaries between <span class="hlt">chondrules</span> and rims indicate that both cases probably occur. The major and minor element composition of opaque rims is similar to "accretionary" rims on objects in CM meteorites [5]. We suggest that both types of rims were formed from the same basic anhydrous dust, although CM rims acquired more O^16-bearing component than UOCs. From here, their evolutionary paths diverged: Opaque rims were thermally processed and CM rims were aqueously altered. Calculations of rim melting due to entry into a transient atmosphere of low scale height [6] indicate that encounter velocities in the range 2-4 km/sec are sufficient to melt the outer parts of <span class="hlt">chondrules</span>. If the thermal conductivity of porous accretionary rims is as low as that of powdered chondrite [7], gas dynamic deceleration can produce totally or partially melted rims on <span class="hlt">chondrules</span> without melting the <span class="hlt">chondrule</span> itself. References: [1] Rubin A. and Wasson J. (1987) GCA, 51, 1923-1937. [2] Podolak et al. (1990) Icarus, 84, 254-260. [3] Bunch T. et al (1991) Meteoritics, 26, 326. [4] Cuzzi J. and Dobrovolskis A. (1993) this meeting. [5] Metzler et al. (1992) GCA, 56, 2873- 2898. [6] Podolak et al. (1993) Icarus, in press. [7] Wechsler A. E. and Glaser P. E. (1965) Icarus, 4, 335.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1114889','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1114889"><span id="translatedtitle">Water and Carbon Dioxide Adsorption at <span class="hlt">Olivine</span> Surfaces</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kerisit, Sebastien N.; Bylaska, Eric J.; Felmy, Andrew R.</p> <p>2013-11-14</p> <p>Plane-wave density functional theory (DFT) calculations were performed to simulate water and carbon dioxide adsorption at the (010) surface of five <span class="hlt">olivine</span> minerals, namely, forsterite (Mg2SiO4), calcio-<span class="hlt">olivine</span> (Ca2SiO4), tephroite (Mn2SiO4), fayalite (Fe2SiO4), and Co-<span class="hlt">olivine</span> (Co2SiO4). Adsorption energies per water molecule obtained from energy minimizations varied from -78 kJ mol-1 for fayalite to -128 kJ mol-1 for calcio-<span class="hlt">olivine</span> at sub-monolayer coverage and became less exothermic as coverage increased. In contrast, carbon dioxide adsorption energies at sub-monolayer coverage ranged from -20 kJ mol-1 for fayalite to -59 kJ mol-1 for calcio-<span class="hlt">olivine</span>. Therefore, the DFT calculations show a strong driving force for carbon dioxide displacement by water at the surface of all <span class="hlt">olivine</span> minerals in a competitive adsorption scenario. Additionally, adsorption energies for both water and carbon dioxide were found to be more exothermic for the alkaline-earth (AE) <span class="hlt">olivines</span> than for the transition-metal (TM) <span class="hlt">olivines</span> and to not correlate with the solvation enthalpies of the corresponding divalent cations. However, a correlation was obtained with the charge of the surface divalent cation indicating that the more ionic character of the AE cations in the <span class="hlt">olivine</span> structure relative to the TM cations leads to greater interactions with adsorbed water and carbon dioxide molecules at the surface and thus more exothermic adsorption energies for the AE <span class="hlt">olivines</span>. For calcio-<span class="hlt">olivine</span>, which exhibits the highest divalent cation charge of the five <span class="hlt">olivines</span>, ab initio molecular dynamics simulations showed that this effect leads both water and carbon dioxide to react with the surface and form hydroxyl groups and a carbonate-like species, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.S44B..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.S44B..07C"><span id="translatedtitle">Effect of <span class="hlt">Olivine</span> Alteration on Seismic Velocities in Oceanic Gabbros</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carlson, R. L.; Newman, J.; Miller, D. J.</p> <p>2006-12-01</p> <p>Seismic velocities in oceanic gabbros are expected to increase with increasing <span class="hlt">olivine</span> content, but this relationship is has not been observed in gabbros recovered by drilling, and inverse methods yield elastic moduli that are anomalously low. Two hypotheses have been advanced to explain these observations: one is that the <span class="hlt">olivine</span> grains in these rocks may contain a high concentration of cracks that affect their elastic moduli, and the other is that the <span class="hlt">olivines</span> in the gabbros have lower Mg numbers (median Fo73) and hence lower moduli than <span class="hlt">olivines</span> that are typical of upper mantle rocks (~Fo90). Our SEM analyses of gabbro samples show that cracks in the <span class="hlt">olivine</span> grains are sealed by serpentine; because they are sealed in situ, cracks cannot explain the low moduli. The elastic moduli of Fo73 are higher than effective moduli of <span class="hlt">olivine</span> in the samples. However, though very little alteration of <span class="hlt">olivine</span> to serpentine was reported in the modal analyses of these rocks, our SEM analysis of gabbros from ODP Hole 923A shows significant alteration of <span class="hlt">olivine</span> to serpentine and magnetite. To explore the effect of this alteration on the relationship between seismic velocities and modal mineral content, we have used the known properties of <span class="hlt">olivine</span> (Fo73), serpentine, magnetite, plagioclase, pyroxene and amphibole to match VRH model velocities to measured velocities by adjusting the degree of alteration of <span class="hlt">olivine</span> in the gabbro samples from Hole 923A. We assume that the alteration products are 95% serpentine and 5% magnetite. Our analysis of the 25 samples from Hole923A indicates that an average of 10-30% alteration of Fo73 to serpentine and magnetite is sufficient to explain the low elastic moduli, and suggest that the lack of correlation between seismic velocities and <span class="hlt">olivine</span> contents arises from variable alteration that is not correlated with initial <span class="hlt">olivine</span> content.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002880','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002880"><span id="translatedtitle">Search for <span class="hlt">Olivine</span> Spectral Signatures on the Surface of Vesta</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Palomba, E.; De Sanctis, M. C.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Longobardo, A.; Tosi, F.; Zambon, F.; McSween, H. Y.; Mittlefehldt, D. W.; Russell, C. T.; Raymond, C. A.; Sunshine, J.; McCord, T. B.</p> <p>2012-01-01</p> <p>The occurrence of <span class="hlt">olivines</span> on Vesta were first postulated from traditional petrogenetic models which suggest the formation of <span class="hlt">olivine</span> as lower crustal cumulates. An indirect confirmation is given by their presence as a minor component in some samples of diogenite meteorites, the harzburgitic diogenites and the dunitic diogenites, and as <span class="hlt">olivine</span> mineral clasts in howardites. Another indication for this mineral was given by interpretations of groundbased and Hubble Space Telescope observations that suggested the presence of local <span class="hlt">olivine</span>-bearing units on the surface of Vesta. The VIR instrument onboard the DAWN mission has been mapping Vesta since July 2011. VIR acquired hyperspectral images of Vesta s surface in the wavelength range from 0.25 to 5.1 m during Approach, Survey and High Altitude Mapping (HAMO) orbits that allowed a 2/3 of the entire asteroid surface to be mapped. The VIR operative spectral interval, resolution and coverage is suitable for the detection and mapping of any <span class="hlt">olivine</span> rich regions that may occur on the Vesta surface. The abundance of <span class="hlt">olivine</span> in diogenites is typically lower than 10% but some samples richer in <span class="hlt">olivine</span> are known. However, we do not expect to have extensive exposures of <span class="hlt">olivine</span>-rich material on Vesta. Moreover, the partial overlap of <span class="hlt">olivine</span> and pyroxene spectral signatures will make <span class="hlt">olivine</span> difficult to detect. Different spectral parameters have been used to map <span class="hlt">olivine</span> on extraterrestrial bodies, and here we discuss the different approaches used, and develop new ones specifically for Vesta. Our new methods are based on combinations of the spectral parameters relative to the 1 and 2 micron bands (the most prominent spectral features of Vesta surface in the visible and the infrared), such as band center locations, band depths, band areas, band area ratios. Before the direct application to the VIR data, the efficiency of each approach is evaluated by means of analysis of laboratory spectra of HED meteorites, pyroxenes, <span class="hlt">olivines</span> and their mixtures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V33A4821H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V33A4821H"><span id="translatedtitle">Diffusive Fractionation of Lithium Isotopes in <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Homolova, V.; Richter, F. M.; Watson, E. B.; Chaussidon, M.</p> <p>2014-12-01</p> <p>Systematic lithium isotope variations along concentration gradients found in <span class="hlt">olivine</span> and pyroxene grains from terrestrial, lunar and martian rocks have been attributed to diffusive isotopic fractionation [Beck et al., 2006; Tang et al., 2007]. In some cases, these isotopic excursions are so large that a single grain may display isotopic variability that spans almost the entire range of documented terrestrial values [Jeffcoate et al., 2007]. In this study, we present the results of experiments to examine diffusive isotopic fractionation of lithium in <span class="hlt">olivine</span>. The experiments comprised crystallographically oriented slabs of San Carlos <span class="hlt">olivine</span> juxtaposed with either spodumene powder or a lithium rich pyroxene crystal. Experiments were conducted at 1 GPa and 0.1MPa over a temperature range of 1000 to 1125⁰C. Oxygen fugacity in the 0.1MPa experiments was controlled using the wustite-magnetite and nickel-nickel oxide solid buffer assemblages. Lithium concentrations generally decrease smoothly away from the edges of the grains; however, experiments involving diffusion parallel to the a-axis consistently show peculiar wavy or segmented concentration profiles. Lithium diffusivity parallel to the c-axis is on the order of 1E-14m2/s at 1100⁰C. The diffusivity parallel to the c-axis is more than an order of magnitude faster than diffusion parallel to the b-axis and correlates positively with oxygen fugacity. The lithium isotopic composition, δ7Li = 1000‰ * ((δ7Lisample- δ7Ligrain center)/ δ7Ligrain center), shows a decrease away from the edge of the grain to a minimum value (up to 70‰ lighter) and then an abrupt increase back to the initial isotopic composition of the <span class="hlt">olivine</span> grain. This isotopic profile is similar to those found in natural grains and an experimental study on diffusive fractionation of lithium isotopes in pyroxene [Richter et al., 2014]. Results from the present study are modeled using the approach of Dohmen et al. [2010], which assumes lithium diffusion occurs on both a metal and interstitial site and that lithium is able to jump between these two sites. The best fits to the results show that diffusive isotopic fractionation may occur on both the interstitial and metal site but the degree of diffusive isotopic fractionation is always greater on the interstitial site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.423...13B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.423...13B"><span id="translatedtitle">Early cosmic ray irradiation of <span class="hlt">chondrules</span> and prolonged accretion of primitive meteorites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beyersdorf-Kuis, Uta; Ott, Ulrich; Trieloff, Mario</p> <p>2015-08-01</p> <p><span class="hlt">Chondrules</span>, together with Ca-Al-rich inclusions (CAIs) and matrix, are the major constituents of primitive meteorites. It is clear that <span class="hlt">chondrules</span> formed as molten objects and the conditions under which this happened seem well constrained. Partially overlapping in age, but mostly ∼2-3 million years younger than the CAIs, they appear to have formed over an extended period of time (e.g., Kita et al., 2013). We have analyzed <span class="hlt">chondrules</span> in two highly primitive CR3 meteorites, QUE 99177 and MET 00426, and find that they contain highly variable amounts of noble gases produced by irradiation with cosmic rays. The lack of implanted solar wind and the composition of the cosmogenic component in QUE 99177 <span class="hlt">chondrules</span> argue against irradiation in a parent body regolith, which leaves irradiation in the early solar system as the most likely explanation. The cosmogenic composition also points to irradiation primarily by galactic cosmic rays (GCR), not solar cosmic rays (SCR), i.e. not by an active early sun. To allow effective production of cosmogenic isotopes by GCR, but not SCR, this should have happened rather "late" in a largely, but not completely, dust-free environment. Our results support the suggestion that <span class="hlt">chondrules</span> formed as free-floating objects in the solar nebula; also consistent with the noble gas data is pre-irradiation in small (∼dm-size) aggregates that broke up before or during accretion to the CR parent body. In both cases, <span class="hlt">chondrules</span> spent an extended period of time before incorporation into the most primitive meteorite parent bodies, which puts constraints on accretion time scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P11C1603N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P11C1603N"><span id="translatedtitle">Oxygen Isotopic Analyses of Water in Bjurböle Matrix and <span class="hlt">Chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nunn, M.; Thiemens, M. H.</p> <p>2011-12-01</p> <p>Past oxygen isotopic analyses of the Bjurböle meteorite have been limited to whole rock and <span class="hlt">chondrule</span> studies. We present here the first oxygen isotopic measurements of water contained in the matrix and <span class="hlt">chondrules</span> of the L4 equilibrated ordinary chondrite Bjurböle. Water was extracted by vacuum pyrolysis from samples of separated matrix and <span class="hlt">chondrules</span> from Bjurböle. A new, low volume, ultra low blank system was built specifically for these measurements. Each fraction was pumped overnight on a vacuum line to remove as much adsorbed terrestrial water as possible before heating step-wise to 150, 350, 600 and 1000°C. While heating, evaporated volatiles were collected in a liquid nitrogen cold trap. Water was quantitatively converted to molecular oxygen with bromine pentafluoride. Isotopic abundances were measured on a double-collecting isotope ratio mass spectrometer. The Δ 17O values obtained from direct fluorination of Bjurböle <span class="hlt">chondrules</span> and whole rock and UV laser probe analyses of individual Bjurböle <span class="hlt">chondrules</span> all cluster around one [1, 2]. Compared to these data, water extracted from the Bjurböle matrix and <span class="hlt">chondrules</span> is isotopically light (Δ 17O = 0.5 and 0.7, respectively), presumably reflecting different equilibration histories of water and oxygen-bearing minerals in each component. Additionally, the proximity of Δ 17O values of water extracted at lower temperatures to zero indicates low-temperature heating is necessary to remove all adsorbed terrestrial water and obtain the true isotopic signature of extraterrestrial water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50..229H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50..229H"><span id="translatedtitle">Fe and O isotope composition of meteorite fusion crusts: Possible natural analogues to <span class="hlt">chondrule</span> formation?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hezel, Dominik C.; Poole, Graeme M.; Hoyes, Jack; Coles, Barry J.; Unsworth, Catherine; Albrecht, Nina; Smith, Caroline; RehkäMper, Mark; Pack, Andreas; Genge, Matthew; Russell, Sara S.</p> <p>2015-02-01</p> <p>Meteorite fusion crust formation is a brief event in a high-temperature (2000-12,000 K) and high-pressure (2-5 MPa) regime. We studied fusion crusts and bulk samples of 10 ordinary chondrite falls and 10 ordinary chondrite finds. The fusion crusts show a typical layering and most contain vesicles. All fusion crusts are enriched in heavy Fe isotopes, with δ56Fe values up to +0.35‰ relative to the solar system mean. On average, the δ56Fe of fusion crusts from finds is +0.23‰, which is 0.08‰ higher than the average from falls (+0.15‰). Higher δ56Fe in fusion crusts of finds correlate with bulk chondrite enrichments in mobile elements such as Ba and Sr. The δ56Fe signature of meteorite fusion crusts was produced by two processes (1) evaporation during atmospheric entry and (2) terrestrial weathering. Fusion crusts have either the same or higher δ18O (0.9-1.5‰) than their host chondrites, and the same is true for Δ17O. The differences in bulk chondrite and fusion crust oxygen isotope composition are explained by exchange of oxygen between the molten surface of the meteorites with the atmosphere and weathering. Meteorite fusion crust formation is qualitatively similar to conditions of <span class="hlt">chondrule</span> formation. Therefore, fusion crusts may, at least to some extent, serve as a natural analogue to <span class="hlt">chondrule</span> formation processes. Meteorite fusion crust and <span class="hlt">chondrules</span> exhibit a similar extent of Fe isotope fractionation, supporting the idea that the Fe isotope signature of <span class="hlt">chondrules</span> was established in a high-pressure environment that prevented large isotope fractionations. The exchange of O between a <span class="hlt">chondrule</span> melt and an 16O-poor nebula as the cause for the observed nonmass dependent O isotope compositions in <span class="hlt">chondrules</span> is supported by the same process, although to a much lower extent, in meteorite fusion crusts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150002321','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150002321"><span id="translatedtitle">Vaporization Studies of <span class="hlt">Olivine</span> via Knudsen Effusion Mass Spectrometry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Costa, G. C. C.; Jacobson, N. S.</p> <p>2014-01-01</p> <p><span class="hlt">Olivine</span> is the major mineral in the Earth's upper mantle occurring predominantly in igneous rocks and has been identified in meteorites, asteroids, the Moon and Mars. Among many other important applications in planetary and materials sciences, the thermodynamic properties of vapor species from <span class="hlt">olivine</span> are crucial as input parameters in computational modelling of the atmospheres of hot, rocky exoplanets (lava planets). There are several weight loss studies of <span class="hlt">olivine</span> vaporization in the literature and one Knudsen Effusion Mass Spectrometry (KEMS) study. In this study, we examine a forsterite-rich <span class="hlt">olivine</span> (93% forsterite and 7% fayalite, Fo93Fa7) with KEMS to further understand its vaporization and thermodynamic properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70025525','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70025525"><span id="translatedtitle">Discovery of <span class="hlt">Olivine</span> in the Nili Fossae Region of Mars</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hoefen, T.M.; Clark, R.N.; Bandfield, J.L.; Smith, M.D.; Pearl, J.C.; Christensen, P.R.</p> <p>2003-01-01</p> <p>We have detected a 30,000-square-kilometer area rich in <span class="hlt">olivine</span> in the Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of grabens and fractures related to the formation of the Isidis impact basin. We propose that post-impact faulting of this area has exposed subsurface layers rich in <span class="hlt">olivine</span>. Linear mixture analysis of Thermal Emission Spectrometer spectra shows surface exposures of 30% <span class="hlt">olivine</span>, where the composition of the <span class="hlt">olivine</span> ranges from Fo30 to Fo70.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19910046580&hterms=Iodine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DIodine','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19910046580&hterms=Iodine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DIodine"><span id="translatedtitle">Iodine-xenon studies of petrographically and chemically characterized Chainpur <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Swindle, T. D.; Caffee, M. W.; Hohenberg, C. M.; Lindstrom, M. M.; Taylor, G. J.</p> <p>1991-01-01</p> <p>INAA, noble gas, and petrographic studies conducted on samples of 18 <span class="hlt">chondrules</span> and matric material from the Chainpur (LL3) indicate that the I-129/I-127 ratio, R(0), varies by a factor of more than 10 among the <span class="hlt">chondrules</span>. This corresponds to a greater-than-50 Ma span in apparent I-Xe ages. Models which invoke either gas-dust mixing or nebular heterogeneity cannot satisfactorily explain these data, any more than can hypotheses which attribute the variations to differences in formation age, metamorphic rate, or time of aqueous alteration. It is alternatively suggested that the variations represent periods of low-grade shock events.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950055059&hterms=ivanova&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Divanova','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950055059&hterms=ivanova&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Divanova"><span id="translatedtitle">The origin of chromitic <span class="hlt">chondrules</span> and the volatility of Cr under a range of nebular conditions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krot, Alexander; Ivanova, Marina A.; Wasson, John T.</p> <p>1993-01-01</p> <p>We characterize ten chromatic <span class="hlt">chondrules</span>, two spinelian <span class="hlt">chondrules</span> andd one spinel-bearing <span class="hlt">chondrule</span> and summarize data for 120 chromitic inclusions discovered in an extensive survey of ordinary chondrites. Compositional and petrographic evidence suggests that chromitic <span class="hlt">chondrules</span> and inclusions are closely related. The Cr/(Cr + Al) ratios in the spinal of these objects range from 0.5 to 0.9 and bulk Al2O3 contents are uniformly high (greater than 10 wt%, except for one with 8 wt%). No other elements having comparable solar abundances are so stongly enriched, and alkali feldspar and merrillite are more common than in normal <span class="hlt">chondrules</span>. The Cr/Mg ratios in chromitic <span class="hlt">chondrules</span> are 180-750 times the ratios in the bulk chondrite. With the possible exception of magnetic clumping of chromite in the presolar cloud, mechanical processes cannot account for this enrichment. Examination of nebular equilibrium processes shows that 50%-condensation temperatures of Cr at pH2/pH2O of 1500 are several tens of degrees below those of Mg as Mg2SiO4; the condensation of Cr is primarily as MgCr2O4 dissolved in MgAl2O4 at nebular pressures of 10(exp -4) atm or below. At pH2 = 10(exp -3) atm condesation as Cr in Fe-Ni is favored. Making the nebula much more oxidizing reduces the difference in condensation temperatures but Mg remains more refractory. We conclude that nebular equilibrium processes are not responsible for the enhanced Cr/Mg ratios. We propose that both Cr and Al became enriched in residues formed by incomplete evaporation of presolar lumps. We suggest that spinals remained as solid phases when the bulk of the silicates were incorporated into the evaporating melt; vaporization of Al and Cr were inhibited by the slow kinetics of diffusion. Subsequent melting and crystallization of these residues fractionated Cr from Al. The resulting materials constituted major components in the precursors of chromitic <span class="hlt">chondrules</span>. Our model implies that chromitic <span class="hlt">chondrules</span> and inclusions preserve the Cr isotopic record of presolar sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/877839','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/877839"><span id="translatedtitle">Anisotropy of electrical conductivity in dry <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Du Frane, W L; Roberts, J J; Toffelmier, D A; Tyburczy, J A</p> <p>2005-04-13</p> <p>[1] The electrical conductivity ({sigma}) was measured for a single crystal of San Carlos <span class="hlt">olivine</span> (Fo{sub 89.1}) for all three principal orientations over oxygen fugacities 10{sup -7} < fO{sub 2} < 10{sup 1} Pa at 1100, 1200, and 1300 C. Fe-doped Pt electrodes were used in conjunction with a conservative range of fO{sub 2}, T, and time to reduce Fe loss resulting in data that is {approx}0.15 log units higher in conductivity than previous studies. At 1200 C and fO{sub 2} = 10{sup -1} Pa, {sigma}{sub [100]} = 10{sup -2.27} S/m, {sigma}{sub [010]} = 10{sup -2.49} S/m, {sigma}{sub [001]} = 10{sup -2.40} S/m. The dependences of {sigma} on T and fO{sub 2} have been simultaneously modeled with undifferentiated mixed conduction of small polarons and Mg vacancies to obtain steady-state fO{sub 2}-independent activation energies: Ea{sub [100]} = 0.32 eV, Ea{sub [010]} = 0.56 eV, Ea{sub [001]} = 0.71 eV. A single crystal of dry <span class="hlt">olivine</span> would provide a maximum of {approx}10{sup 0.4} S/m azimuthal {sigma} contrast for T < 1500 C. The anisotropic results are combined to create an isotropic model with Ea = 0.53 eV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150001926','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150001926"><span id="translatedtitle">Mineralogical Comparison of <span class="hlt">Olivine</span> in Shergottites and A Shocked L Chondrite: Implications for Shock Histories of Brown <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Takenouchi, A.; Mikouchi, T.; Yamaguchi, A.; Zolensky, M. E.</p> <p>2015-01-01</p> <p>Most Martian meteorites are heavily shocked, exhibiting numerous shock features, for example undulatory extinction of <span class="hlt">olivine</span> and pyroxene, the presence of diaplectic glass ("maskelynite") and the formation of shock melt. Among these shock features, <span class="hlt">olivine</span> darkening ("brown" <span class="hlt">olivine</span>) is unique in Martian meteorites because no other meteorite group shows such a feature. Although the presence of brown <span class="hlt">olivine</span> in shergottites was reported thirty years ago, detailed observation by TEM has not been performed until the NWA 2737 chassignite was discovered, whose <span class="hlt">olivine</span> is darkened, being completely black in hand specimen. Fe metal nano-particles were found in NWA 2737 <span class="hlt">olivine</span> which are considered to have been formed by <span class="hlt">olivine</span> reduction during heavy shock. Subsequently, magnetite nano-particles were also found in other Martian meteorites and the coexistence of Fe metal and magnetite nano-particles was reported in the NWA 1950 shergottite and some Fe metal nano-particles were mantled by magnetite. Therefore, the formation process of nano-particles seems to be complex. Because "brown" <span class="hlt">olivine</span> is unique to Martian meteorites, they have a potential to constrain their shock conditions. In order to better understand the shock history of Martian meteorites, we compared <span class="hlt">olivine</span> in several shergottites with that in a highly-shocked L chondrite which contains ringwoodite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70011043','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70011043"><span id="translatedtitle">Geobarometry of ultramafic xenoliths from Loihi Seamount, Hawaii, on the basis of CO2 inclusions in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Roedder, E.</p> <p>1983-01-01</p> <p>Abundant fluid inclusions in <span class="hlt">olivine</span> of dunite xenoliths (???1-3 cm) in basalt dredged from the young Loihi Seamount, 30 km southeast of Hawaii, are evidence for three coexisting immiscible fluid phases-silicate melt (now glass), sulfide melt (now solid), and dense supercritical CO2 (now liquid + gas)-during growth and later fracturing of some of these <span class="hlt">olivine</span> crystals. Some <span class="hlt">olivine</span> xenocrysts, probably from disaggregation of xenoliths, contain similar inclusions. Most of the inclusions (2-10 ??m) are on secondary planes, trapped during healing of fractures after the original crystal growth. Some such planes end abruptly within single crystals and are termed pseudosecondary, because they formed during the growth of the host <span class="hlt">olivine</span> crystals. The "vapor" bubble in a few large (20-60 ??m), isolated, and hence primary, silicate melt inclusions is too large to be the result of simple differential shrinkage. Under correct viewing conditions, these bubbles are seen to consist of CO2 liquid and gas, with an aggregate ??{variant} = ??? 0.5-0.75 g cm-3, and represent trapped globules of dense supercritical CO2 (i.e., incipient "vesiculation" at depth). Some spinel crystals enclosed within <span class="hlt">olivine</span> have attached CO2 blebs. Spherical sulfide blebs having widely variable volume ratios to CO2 and silicate glass are found in both primary and pseudosecondary inclusions, demonstrating that an immiscible sulfide melt was also present. Assuming <span class="hlt">olivine</span> growth at ??? 1200??C and hydrostatic pressure from a liquid lava column, extrapolation of CO2 P-V-T data indicates that the primary inclusions were trapped at ??? 220-470 MPa (2200-4700 <span class="hlt">bars</span>), or ??? 8-17 km depth in basalt magma of ??{variant} = 2.7 g cm-3. Because the temperature cannot change much during the rise to eruption, the range of CO2 densities reveals the change in pressure from that during original <span class="hlt">olivine</span> growth to later deformation and rise to eruption on the sea floor. The presence of numerous decrepitated inclusions indicates that the inclusion sample studied is biased by the loss of higher-density inclusions and suggests that some part of these <span class="hlt">olivine</span> xenoliths formed at greater depths. ?? 1983.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS...51..884D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS...51..884D"><span id="translatedtitle">Microchondrules in two unequilibrated ordinary chondrites: Evidence for formation by splattering from <span class="hlt">chondrules</span> during stochastic collisions in the solar nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dobricǎ, E.; Brearley, A. J.</p> <p>2016-05-01</p> <p>The diversity of silicate, glassy spherules analogous to <span class="hlt">chondrules</span>, called microchondrules, and the implications for their presence in unequilibrated ordinary chondrites (UOCs) were investigated using different electron microscope techniques. Our observations show that the abundance of microchondrules in UOCs is much larger than the values proposed by previous studies. We identified two different types of microchondrules, porous and nonporous, embedded within fine-grained matrices and type I <span class="hlt">chondrule</span> rims. The porous microchondrules are characterized by distinctive textures and chemical compositions that have not been recognized previously. Additionally, we show detailed textures and chemical compositions of protuberances of silicate materials, connected to the <span class="hlt">chondrules</span> and ending with microchondrules. We suggest that microchondrules and protuberances formed from materials splattered from the <span class="hlt">chondrules</span> during stochastic collisions when they were still either completely or partially molten. The occurrence and distinct morphologies of microchondrules and protuberances suggest that rather than just a passive flash melting of <span class="hlt">chondrules</span>, an additional event perturbed the molten <span class="hlt">chondrules</span> before they underwent cooling. The bulk chemical compositions suggest that (1) nonporous microchondrules and protuberances were formed by splattering of materials that are compositionally similar to the bulk silicate composition of type I <span class="hlt">chondrules</span>, and (2) the porous microchondrules could represent the splattered melt products of a less evolved, fine-grained dust composition. The preservation of protuberances and microchondrules in the rims suggests that the cooling and accretion rates were exceptionally fast and that they represent the last objects that were formed before the accretion of the parent bodies of OCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS..tmp..303D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS..tmp..303D"><span id="translatedtitle">Microchondrules in two unequilibrated ordinary chondrites: Evidence for formation by splattering from <span class="hlt">chondrules</span> during stochastic collisions in the solar nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dobricǎ, E.; Brearley, A. J.</p> <p>2016-03-01</p> <p>The diversity of silicate, glassy spherules analogous to <span class="hlt">chondrules</span>, called microchondrules, and the implications for their presence in unequilibrated ordinary chondrites (UOCs) were investigated using different electron microscope techniques. Our observations show that the abundance of microchondrules in UOCs is much larger than the values proposed by previous studies. We identified two different types of microchondrules, porous and nonporous, embedded within fine-grained matrices and type I <span class="hlt">chondrule</span> rims. The porous microchondrules are characterized by distinctive textures and chemical compositions that have not been recognized previously. Additionally, we show detailed textures and chemical compositions of protuberances of silicate materials, connected to the <span class="hlt">chondrules</span> and ending with microchondrules. We suggest that microchondrules and protuberances formed from materials splattered from the <span class="hlt">chondrules</span> during stochastic collisions when they were still either completely or partially molten. The occurrence and distinct morphologies of microchondrules and protuberances suggest that rather than just a passive flash melting of <span class="hlt">chondrules</span>, an additional event perturbed the molten <span class="hlt">chondrules</span> before they underwent cooling. The bulk chemical compositions suggest that (1) nonporous microchondrules and protuberances were formed by splattering of materials that are compositionally similar to the bulk silicate composition of type I <span class="hlt">chondrules</span>, and (2) the porous microchondrules could represent the splattered melt products of a less evolved, fine-grained dust composition. The preservation of protuberances and microchondrules in the rims suggests that the cooling and accretion rates were exceptionally fast and that they represent the last objects that were formed before the accretion of the parent bodies of OCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24196707','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24196707"><span id="translatedtitle"><span class="hlt">Olivine</span> in an unexpected location on Vesta's surface.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ammannito, E; De Sanctis, M C; Palomba, E; Longobardo, A; Mittlefehldt, D W; McSween, H Y; Marchi, S; Capria, M T; Capaccioni, F; Frigeri, A; Pieters, C M; Ruesch, O; Tosi, F; Zambon, F; Carraro, F; Fonte, S; Hiesinger, H; Magni, G; McFadden, L A; Raymond, C A; Russell, C T; Sunshine, J M</p> <p>2013-12-01</p> <p><span class="hlt">Olivine</span> is a major component of the mantle of differentiated bodies, including Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower-crust and possibly ultramafic-mantle samples of asteroid Vesta, which is the lone surviving, large, differentiated, basaltic rocky protoplanet in the Solar System. Only a few of these meteorites, the orthopyroxene-rich diogenites, contain <span class="hlt">olivine</span>, typically with a concentration of less than 25 per cent by volume. <span class="hlt">Olivine</span> was tentatively identified on Vesta, on the basis of spectral and colour data, but other observations did not confirm its presence. Here we report that <span class="hlt">olivine</span> is indeed present locally on Vesta's surface but that, unexpectedly, it has not been found within the deep, south-pole basins, which are thought to be excavated mantle rocks. Instead, it occurs as near-surface materials in the northern hemisphere. Unlike the meteorites, the <span class="hlt">olivine</span>-rich (more than 50 per cent by volume) material is not associated with diogenite but seems to be mixed with howardite, the most common surface material. <span class="hlt">Olivine</span> is exposed in crater walls and in ejecta scattered diffusely over a broad area. The size of the <span class="hlt">olivine</span> exposures and the absence of associated diogenite favour a mantle source, but the exposures are located far from the deep impact basins. The amount and distribution of observed <span class="hlt">olivine</span>-rich material suggest a complex evolutionary history for Vesta. PMID:24196707</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeCoA.162..259S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeCoA.162..259S"><span id="translatedtitle">Fast grain growth of <span class="hlt">olivine</span> in liquid Fe-S and the formation of pallasites with rounded <span class="hlt">olivine</span> grains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Solferino, Giulio F. D.; Golabek, Gregor J.; Nimmo, Francis; Schmidt, Max W.</p> <p>2015-08-01</p> <p>Despite their relatively simple mineralogical composition (<span class="hlt">olivine</span> + Fe-Ni metal + FeS ± pyroxene), the origin of pallasite meteorites remains debated. It has been suggested that catastrophic mixing of <span class="hlt">olivine</span> fragments with Fe-(Ni)-S followed by various degrees of annealing could explain pallasites bearing solely or prevalently fragmented or rounded <span class="hlt">olivines</span>. In order to verify this hypothesis, and to quantify the grain growth rate of <span class="hlt">olivine</span> in a liquid metal matrix, we performed a series of annealing experiments on natural <span class="hlt">olivine</span> plus synthetic Fe-S mixtures. The best explanation for the observed <span class="hlt">olivine</span> grain size distributions (GSD) of the experiments are dominant Ostwald ripening for small grains followed by random grain boundary migration for larger grains. Our results indicate that <span class="hlt">olivine</span> grain growth in molten Fe-S is significantly faster than in solid, sulphur-free metal. We used the experimentally determined grain growth law to model the coarsening of <span class="hlt">olivine</span> surrounded by Fe-S melt in a 100-600 km radius planetesimal. In this model, an impact is responsible for the mixing of <span class="hlt">olivine</span> and Fe-(Ni)-S. Numerical models suggest that annealing at depths of up to 50 km allow for (i) average grain sizes consistent with the observed rounded <span class="hlt">olivine</span> in pallasites, (ii) a remnant magnetisation of Fe-Ni <span class="hlt">olivine</span> inclusions as measured in natural pallasites and (iii) for the metallographic cooling rates derived from Fe-Ni in pallasites. This conclusion is valid even if the impact occurs several millions of years after the differentiation of the target body was completed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012Icar..218..701B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012Icar..218..701B"><span id="translatedtitle">Free collisions in a microgravity many-particle experiment - II: The collision dynamics of dust-coated <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beitz, E.; Güttler, C.; Weidling, R.; Blum, J.</p> <p>2012-03-01</p> <p>The formation of planetesimals in the early Solar System is hardly understood, and in particular the growth of dust aggregates above millimeter sizes has recently turned out to be a difficult task in our understanding (Zsom, A., Ormel, C.W., Güttler, C., Blum, J., Dullemond, C.P. [2010]. Astron. Astrophys., 513, A57). Laboratory experiments have shown that dust aggregates of these sizes stick to one another only at unreasonably low velocities. However, in the protoplanetary disk, millimeter-sized particles are known to have been ubiquitous. One can find relics of them in the form of solid <span class="hlt">chondrules</span> as the main constituent of chondrites. Most of these <span class="hlt">chondrules</span> were found to feature a fine-grained rim, which is hypothesized to have formed from accreting dust grains in the solar nebula. To study the influence of these dust-coated <span class="hlt">chondrules</span> on the formation of chondrites and possibly planetesimals, we conducted collision experiments between millimeter-sized, dust-coated <span class="hlt">chondrule</span> analogs at velocities of a few cm s-1. For 2 and 3 mm diameter <span class="hlt">chondrule</span> analogs covered by dusty rims of a volume filling factor of 0.18 and 0.35-0.58, we found sticking velocities of a few cm s-1. This velocity is higher than the sticking velocity of dust aggregates of the same size. We therefore conclude that <span class="hlt">chondrules</span> may be an important step towards a deeper understanding of the collisional growth of larger bodies. Moreover, we analyzed the collision behavior in an ensemble of dust aggregates and non-coated <span class="hlt">chondrule</span> analogs. While neither the dust aggregates nor the solid <span class="hlt">chondrule</span> analogs show sticking in collisions among their species, we found an enhanced sicking efficiency in collisions between the two constituents, which leads us to the conjecture that <span class="hlt">chondrules</span> might act as “catalyzers” for the growth of larger bodies in the young Solar System.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=PIA09348&hterms=fingerprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dfingerprint','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=PIA09348&hterms=fingerprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dfingerprint"><span id="translatedtitle"><span class="hlt">Olivine</span> in the Southern Isidis Basin</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p><p/> The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this observation of the transition region between Libya Montes and the Isidis Basin on Mars at 17:16 UTC (12:16 p.m. EST) on January 2, 2007, near 3.6 degrees north latitude, 84.1 degrees east longitude. The image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 18 meters (60 feet) across. The image is about 11 kilometers (7 miles) wide at its narrowest point. <p/> The Isidis Basin resulted from of a gigantic impact on the surface of Mars early in the planet's history. The southern rim, where this target is located, is a region of complex geology and part of the planetary dichotomy boundary that separates the older southern highlands from the lower, younger northern plains. The image on the left was constructed from three visible wavelengths (RGB: 0.71, 0.60, 0.53 microns) and is a close approximation of how the surface would appear to the human eye. The image on the right was constructed from three infrared wavelengths (RGB: 2.49, 1.52, 1.08 microns) chosen to highlight variations in the mineralogy of the area. Of interest is that features in this image not only differ in color, but also in texture and morphology. The gray areas absorb similarly at all wavelengths used in this image, but display absorptions at other wavelengths related to the iron- and magesium-rich mineral pyroxene. The reddest areas absorb strongly at the wavelengths used for green and blue, which is attributable to another iron- and magesium-rich mineral, <span class="hlt">olivine</span>. The brownish areas show subdued mineral absorptions and could represent some type of mixture between the other two materials. The presence of the mineral <span class="hlt">olivine</span> is particularly interesting because <span class="hlt">olivine</span> easily weathers to other minerals; thus, its presence indicates either the lack of weathering in this region or relatively recent exposure. <p/> CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials -- leading to new understanding of the climate. <p/> The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890023498&hterms=chemical+separations&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dchemical%2Bseparations','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890023498&hterms=chemical+separations&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dchemical%2Bseparations"><span id="translatedtitle">Chemical dispersion among Apollo 15 <span class="hlt">olivine</span>-normative mare basalts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ryder, Graham; Steele, Alison</p> <p>1988-01-01</p> <p>Analysis of Apollo 15 <span class="hlt">olivine</span>-normative mare basalts for major and minor elements suggests that the hypothesis that the coarser-grained varieties (<span class="hlt">olivine</span> microgabbros) consist of two chemical groups is incorrect. Instead, it is found that there is a single group including vesicular, coarse-grained, and fine-grained basalts. For the entire suite, the dispersion of compositions along the <span class="hlt">olivine</span> trend is too great to be explained by short-range unmixing of an unfractionated flow. It is suggested that the general trend for the suite is <span class="hlt">olivine</span> separation, probably through crystal settling. The textures, mineralogical characteristics, and chemical variation of the <span class="hlt">olivine</span>-normative basalts are shown to be consistent with a sequence of thin fractionating flows, all from a common parent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020046135&hterms=oxygen+isotopes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Doxygen%2Bisotopes','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020046135&hterms=oxygen+isotopes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Doxygen%2Bisotopes"><span id="translatedtitle">Forsterite from <span class="hlt">Chondrules</span> in the Mokoia (CV3) Chondrite: Cathodoluminescence, Chemistry and Oxygen Isotopes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jones, R. H.; Carey, R.; Leshin, L. A.; Guan, Y.</p> <p>2002-01-01</p> <p>Forsterite in Mokoia <span class="hlt">chondrules</span> shows CL zoning which can be quite complex. Oxygen isotope analyses in forsterite with different CL intensities are homogeneous, showing that refractory and melt-grown forsterites are isotopically indistinguishable. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22048076','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22048076"><span id="translatedtitle">INCORPORATION OF A LATE-FORMING <span class="hlt">CHONDRULE</span> INTO COMET WILD 2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ogliore, R. C.; Huss, G. R.; Nagashima, K.; Butterworth, A. L.; Gainsforth, Z.; Stodolna, J.; Westphal, A. J.; Joswiak, D.; Tyliszczak, T.</p> <p>2012-02-15</p> <p>We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a <span class="hlt">chondrule</span> fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II <span class="hlt">chondrule</span> that formed from an evolved oxygen isotopic reservoir. No evidence for extinct {sup 26}Al was found, with ({sup 26}Al/{sup 27}Al){sub 0} < 3.0 Multiplication-Sign 10{sup -6}. Assuming homogenous distribution of {sup 26}Al in the solar nebula, this particle crystallized at least 3 Myr after the earliest solar system objects-relatively late compared to most <span class="hlt">chondrules</span> in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary <span class="hlt">chondrule</span>) to be more than 3 Myr after calcium-aluminum-rich inclusions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950031756&hterms=American+Museum+of+Natural+History&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D%2528%2528%2528%2528American%2BMuseum%2529%2Bof%2529%2BNatural%2529%2BHistory%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950031756&hterms=American+Museum+of+Natural+History&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D%2528%2528%2528%2528American%2BMuseum%2529%2Bof%2529%2BNatural%2529%2BHistory%2529"><span id="translatedtitle">The evolution of enstatite and <span class="hlt">chondrules</span> in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weisberg, Michael K.; Prinz, Martin; Fogel, Robert A.</p> <p>1994-01-01</p> <p>FeO-rich (Fs(sub 6)-34) pyroxene lacking cathodoluminescence (CL), hereafter black pyroxene, is a major constituent of some of the <span class="hlt">chondrules</span> and fragments in unequilibrated (type 3) enstatite chondrites (UECs). It contains structurally oriented zones of Cr-, Mn-, V-rich, FeO-poor enstatite with red CL, associated with mm-sized blebs of low-Ni, Fe-metal and, in some cases, silica. These occurrences represent clear evidence of pyroxene reduction. The black pyroxene is nearly always rimmed by minor element (Cr, Mn, V)-poor enstatite having a blue CL. More commonly, red and blue enstatites, unassociated with black pyroxene, occur as larger grains in <span class="hlt">chondrules</span> and fragments, and these constitute the major silicate phases in UECs. The rare earth element (REE) abundance patterns of the black pyroxene are LREE-depleted. The blue enstatite rims, however, have a near-flat to LREE-enriched pattern, approx. 0.5-4x chondritic. The petrologic and trace element data indicate that the black pyroxene is from an earlier generation of <span class="hlt">chondrules</span> that formed in a nebular region that was more oxidizing than that of the enstatite chondrites. Following solidification, these <span class="hlt">chondrules</span> experienced a more reducing nebular environment and underwent reduction. Some, perhaps most, of the red enstatite that is common throughout the UECs may be the product of solid-state reduction of black pyroxene. The blue enstatite rims grew onto the surfaces of the black pyroxene and red enstatite as a result of condensation from a nebular gas. The evolutionary history of some of the enstatite and <span class="hlt">chondrules</span> in enstatite chondrites can be expressed in a four-stage model that includes: Stage 1. Formation of <span class="hlt">chondrules</span> in an oxidizing nebular environment. Stage 2. Solid-state reduction of the more oxidized <span class="hlt">chondrules</span> and fragments to red enstatite in a more reducing nebular environment. Stage 3. Formation of blue enstatite rims on the black pyroxene as well as on the red enstatite. Stage 4. Reprocessing, by various degrees of melting, of many of the earlier-formed materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70030455','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70030455"><span id="translatedtitle">Cotectic proportions of <span class="hlt">olivine</span> and spinel in <span class="hlt">olivine</span>-tholeiitic basalt and evaluation of pre-eruptive processes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Roeder, P.; Gofton, E.; Thornber, C.</p> <p>2006-01-01</p> <p>The volume %, distribution, texture and composition of coexisting <span class="hlt">olivine</span>, Cr-spinel and glass has been determined in quenched lava samples from Hawaii, Iceland and mid-oceanic ridges. The volume ratio of <span class="hlt">olivine</span> to spinel varies from 60 to 2800 and samples with >0.02% spinel have a volume ratio of <span class="hlt">olivine</span> to spinel of approximately 100. A plot of wt % MgO vs ppm Cr for natural and experimental basaltic glasses suggests that the general trend of the glasses can be explained by the crystallization of a cotectic ratio of <span class="hlt">olivine</span> to spinel of about 100. One group of samples has an <span class="hlt">olivine</span> to spinel ratio of approximately 100, with skeletal <span class="hlt">olivine</span> phenocrysts and small (100 ??m) spinel crystals that show evidence of two stages of growth, and a volume ratio of <span class="hlt">olivine</span> to spinel of 100 to well over 1000. The <span class="hlt">olivine</span> and spinel in this group have crystallized more slowly with little physical interaction, and show evidence that they have accumulated in a magma chamber. ?? 2006 Oxford University Press.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/576752','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/576752"><span id="translatedtitle">Boron, beryllium, and lithium, partitioning in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Neroda, Elizabeth</p> <p>1996-05-01</p> <p>A one atmosphere experimental study was performed to determine the mineral/melt partition coefficients for B, Be, and Li in forsteritic <span class="hlt">olivine</span>. Two compositions were chosen along the 1350{degrees}C isotherm, 1b (Fo{sub 17.3} Ab{sub 82.7} An{sub 0} by weight) and 8c (Fo{sub 30} Ab{sub 23.3} An{sub 47.8}, by weight) were then combined in equal amounts to form a composition was doped with 25ppm Li, B, Yb, Nb, Zr, Sr, and Hf, 50ppm Sm, and 100ppm Be, Nd, Ce, and Rb. Electron and ion microprobe analyses showed that the <span class="hlt">olivine</span> crystals and surrounding glasses were homogeneous with respect to major and trace elements. Partition coefficients calculated from these analyses are as follows: 1b: D{sub B} = 4.41 ({+-} 2.3) E-03, D{sub Be} = 2.86 ({+-} 0.45) E-03, D{sub Li} = 1.54 ({+-} 0.21) E-01, 50/50: D{sub B} = 2.86 ({+-} 0.5) E-03, D{sub Be} = 2.07 ({+-} 0.09) E-03, D{sub Li} = 1.51 ({+-} 0.18) E-01, 8c: D{sub B} = 6.05 ({+-} 1.5) E-03, D{sub Be} = 1.81 ({+-} 0.03) E-03, D{sub Li} = 1.31 ({+-} 0.09) E-01. The results of this study will combined with similar data for other minerals as part of a larger study to understand the partitioning behavior of B, Be, and Li in melting of the upper mantle at subduction zones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeCoA.148..402V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeCoA.148..402V"><span id="translatedtitle">Replacement of <span class="hlt">olivine</span> by serpentine in the Queen Alexandra Range 93005 carbonaceous chondrite (CM2): Reactant-product compositional relations, and isovolumetric constraints on reaction stoichiometry and elemental mobility during aqueous alteration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velbel, Michael A.; Tonui, Eric K.; Zolensky, Michael E.</p> <p>2015-01-01</p> <p>Isovolumetric replacement of euhedral and anhedral <span class="hlt">olivine</span> by serpentine produced both centripetal and meshwork textures in the CM2 chondrites ALH 81002 and Nogoya. The compositions of these textural varieties of serpentine are uniform within narrow limits within each previously studied meteorite, independent of the composition of <span class="hlt">olivine</span> being replaced, and different between the two meteorites. In QUE 93005 (CM2), coarse <span class="hlt">olivines</span> of widely varying compositions (Fo<76-99) are replaced in a texturally similar manner by compositionally uniform serpentine (Mg0.73±0.05Fe0.27±0.05)3Si2O5(OH)4. The narrow compositional range of serpentine replacing coarse <span class="hlt">olivine</span> indicates that the aqueous solution from which the serpentine formed was compositionally uniform on scales at least as large as the meteorite (∼2.5 cm in longest dimension). Isovolumetric textures and compositional observations constrain elemental redistribution from coarse <span class="hlt">olivine</span> to serpentine and to surrounding phases during serpentinization. Regardless of <span class="hlt">olivine</span>'s composition, isovolumetric replacement of coarse <span class="hlt">olivines</span> by serpentine of the observed composition released more Mg and Si from <span class="hlt">olivine</span> than was required to form the serpentine. Excess Mg and Si released by <span class="hlt">olivine</span> destruction and not retained in serpentine were exported from the replaced volume. <span class="hlt">Olivines</span> with different Fa/Fo proportions contributed different amounts of Fe and Mg to the serpentine. Ferroan <span class="hlt">olivines</span> released more Fe than required to form the serpentines replacing them, so some of the Fe released from ferroan <span class="hlt">olivine</span> was exported from the replaced volumes. Forsteritic <span class="hlt">olivines</span> released less Fe than required to form the serpentines replacing them, so some Fe was imported into the replaced volumes augmenting the small amount of Fe released from forsteritic <span class="hlt">olivine</span>. In QUE 93005 Fo83.8 is the threshold composition between Fe-exporting and Fe-importing behavior in individual <span class="hlt">olivine</span>-serpentine pairs, which released exactly the amount of Fe required to form serpentine of the observed uniform composition. Compositions of serpentines isovolumetrically replacing <span class="hlt">olivines</span>, and threshold <span class="hlt">olivine</span> compositions, in QUE 93005 differ from the corresponding values in Nogoya. Solvent and solute species diffused through the serpentine between the <span class="hlt">olivine</span>-serpentine interface and the aqueous solution outside the isovolumetrically replaced volume. In QUE 93005, some of the Fe released from ferroan <span class="hlt">olivine</span> in excess of the amount required to form serpentine reacted with S sourced from outside the pseudomorphs to form Fe-sulfide decorating the margins of the pseudomorphs of serpentine after fayalitic <span class="hlt">olivine</span>. Such Fe-sulfide-decorated outlines after fayalitic <span class="hlt">olivine</span> do not occur in ALH 81002 or Nogoya, indicating different Fe and S mass transfer regimes in different CM2 chondrites. Mg, Fe, Si, and S in the aqueous solution, including the excess Mg and Si exported from all serpentine pseudomorphs after <span class="hlt">olivine</span> of any composition, were available to be incorporated into other phases spatially separate from the pseudomorphs after <span class="hlt">olivine</span>, including regularly interstratified serpentine-tochilinite. Serpentines that replaced coarse <span class="hlt">olivines</span> in QUE 93005 and ALH 81002 are less magnesian than those in Nogoya, indicating that the Nogoya aqueous-alteration environment was more evolved toward Mg-rich solutions. This easily located and characterized phase assemblage may be potentially useful for characterizing clasts of varying degrees of alteration in brecciated and heterogeneous CM chondrites, and future returned samples from mineralogically similar asteroids. partial and complete pseudomorphic and alteromorphic replacement (after euhedral and anhedral primary minerals, respectively; the terminology of Delvigne, 1998, is used sensu stricto where the distinction is important in this paper, and the more familiar term pseudomorph is used elsewhere sensu lato in the interest of brevity),</ce:para> meshwork serpentinization textures (Wicks and Whittaker, 1977),</ce:para> and "centripetal replacement" in which entire grains or fracture-bounded remnants are replaced from the margin inward (e.g., Velbel, 1984, 1993).</ce:para> </ce:para>More papers reported alteromorphic replacement of (anhedral) coarse anhydrous chondritic silicates (subhedral/anhedral silicates in <span class="hlt">chondrules</span>; isolated monocrystalline <span class="hlt">olivine</span> in matrix) than pseudomorphic replacement of euhedral <span class="hlt">olivine</span> (Fuchs et al., 1973; McSween, 1979a,b; Bunch and Chang, 1980; Zolensky and McSween, 1988; Browning et al., 1996, 2000; Zolensky et al., 1997; Hanowski and Brearley, 2001; Zolensky and Ivanov, 2003; Rubin et al., 2007; MacPherson et al., 2009; Velbel et al., 2012). Centripetal replacement of <span class="hlt">olivine</span> by serpentine during terrestrial serpentinization has been elegantly described by Boudier et al. (2010). Simple centripetal replacement of <span class="hlt">olivine</span> by serpentine in CM chondrites has been observed and illustrated by Hanowski and Brearley (2001) and Rubin et al. (2007). Meshwork serpentines mark the former distribution of grain boundaries and intragranular fractures, and separate remnants of unreplaced primary mineral (e.g., Wicks and Whittaker, 1977; Delvigne, 1998).</ce:para>Bunch and Chang (1980), Hanowski and Brearley (2001), Zolensky and Ivanov (2003), and Velbel et al. (2012) describe serpentine occurring both as meshwork and pseudomorphic after <span class="hlt">olivine</span> in altered CM2 chondrites. Velbel et al. (2012) found meshwork serpentinization textures in near end-member forsteritic <span class="hlt">olivine</span> to be both common and similar to their terrestrial counterparts, to a much greater degree than in ferroan <span class="hlt">olivine</span>. In both meshwork and centripetal replacement, <span class="hlt">olivine</span> and pyroxene remnants, with maximum dimensions of tens of micrometers and rarely up to 250 μm, survive in the centers of some pseudomorphs and alteromorphs (including meshworks) of phyllosilicate after the anhydrous primary silicate (Hanowski and Brearley, 2001; Velbel et al., 2012).</ce:para>Serpentinization of coarse-grained <span class="hlt">olivine</span> (and pyroxene) appears to represent an advanced intermediate stage of aqueous alteration (Hanowski and Brearley, 2001; Velbel et al., 2012; Velbel, 2014); it occurs abundantly only in CM chondrites in which essentially all other primary silicate phases in matrix, rims, and mesostasis are already extensively altered to increasingly Mg-rich serpentine (Browning and other, 1996; Hanowski and Brearley, 2001; Brearley, 2003, 2006; Rubin et al., 2007; Chizmadia and Brearley, 2008; Howard et al., 2009, 2011). Hanowski and Brearley (2001) proposed a four-stage model relating the textures and compositions of phyllosilicates replacing coarse CM2 <span class="hlt">olivine</span>, the extent and degree of <span class="hlt">olivine</span> alteration to serpentine, and the chemical evolution of the co-existing aqueous solutions, culminating in the observed properties of ALH 81002. Following on their four-stage model, Velbel et al. (2012) added observations and inferences from Nogoya, extending the model of Hanowski and Brearley (2001) to an even more altered, fifth stage. The expanded version as presented by Velbel et al. (2012) and Velbel (2014) is shown in Table 1. Velbel et al. (2012) summarized the initial conditions and Stages 1-3 of the Hanowski and Brearley (2001) model. Stages 4 and 5 are most relevant to the work presented in the present paper, and a brief updated summary of these stages is presented here.</ce:para></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS..tmp..301M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS..tmp..301M"><span id="translatedtitle">The effect of multiple particle sizes on cooling rates of <span class="hlt">chondrules</span> produced in large-scale shocks in the solar nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, Melissa A.; Weidenschilling, Stuart J.; Desch, Steven J.</p> <p>2016-03-01</p> <p><span class="hlt">Chondrules</span> represent one of the best probes of the physical conditions and processes acting in the early solar nebula. Proposed <span class="hlt">chondrule</span> formation models are assessed based on their ability to match the meteoritic evidence, especially experimental constraints on their thermal histories. The model most consistent with <span class="hlt">chondrule</span> thermal histories is passage through shock waves in the solar nebula. Existing models of heating by shocks generally yield a good first-order approximation to inferred <span class="hlt">chondrule</span> cooling rates. However, they predict prolonged heating in the preshock region, which would cause volatile loss and isotopic fractionation, which are not observed. These models have typically included particles of a single (large) size, i.e., <span class="hlt">chondrule</span> precursors, or at most, large particles accompanied by micron-sized grains. The size distribution of solids present during <span class="hlt">chondrule</span> formation controls the opacity of the affected region, and significantly affects the thermal histories of <span class="hlt">chondrules</span>. Micron-sized grains evaporate too quickly to prevent excessive heating of <span class="hlt">chondrule</span> precursors. However, isolated grains in <span class="hlt">chondrule</span>-forming regions would rapidly coagulate into fractal aggregates. Preshock heating by infrared radiation from the shock front would cause these aggregates to melt and collapse into intermediate-sized (tens of microns) particles. We show that inclusion of such particles yields <span class="hlt">chondrule</span> cooling rates consistent with petrologic and isotopic constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016M%26PS...51..870M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016M%26PS...51..870M"><span id="translatedtitle">The effect of multiple particle sizes on cooling rates of <span class="hlt">chondrules</span> produced in large-scale shocks in the solar nebula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, Melissa A.; Weidenschilling, Stuart J.; Desch, Steven J.</p> <p>2016-05-01</p> <p><span class="hlt">Chondrules</span> represent one of the best probes of the physical conditions and processes acting in the early solar nebula. Proposed <span class="hlt">chondrule</span> formation models are assessed based on their ability to match the meteoritic evidence, especially experimental constraints on their thermal histories. The model most consistent with <span class="hlt">chondrule</span> thermal histories is passage through shock waves in the solar nebula. Existing models of heating by shocks generally yield a good first-order approximation to inferred <span class="hlt">chondrule</span> cooling rates. However, they predict prolonged heating in the preshock region, which would cause volatile loss and isotopic fractionation, which are not observed. These models have typically included particles of a single (large) size, i.e., <span class="hlt">chondrule</span> precursors, or at most, large particles accompanied by micron-sized grains. The size distribution of solids present during <span class="hlt">chondrule</span> formation controls the opacity of the affected region, and significantly affects the thermal histories of <span class="hlt">chondrules</span>. Micron-sized grains evaporate too quickly to prevent excessive heating of <span class="hlt">chondrule</span> precursors. However, isolated grains in <span class="hlt">chondrule</span>-forming regions would rapidly coagulate into fractal aggregates. Preshock heating by infrared radiation from the shock front would cause these aggregates to melt and collapse into intermediate-sized (tens of microns) particles. We show that inclusion of such particles yields <span class="hlt">chondrule</span> cooling rates consistent with petrologic and isotopic constraints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeCoA..74..784L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeCoA..74..784L"><span id="translatedtitle">The pattern of Ni and Co abundances in lunar <span class="hlt">olivines</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Longhi, John; Durand, Sedelia R.; Walker, David</p> <p>2010-01-01</p> <p>Near liquidus experiments on peridotite and other <span class="hlt">olivine</span> normative compositions from 1.7 to 6 GPa confirm the applicability of exchange-based empirical models of Ni and Co partitioning between <span class="hlt">olivine</span> and silicate liquids with compositions close to the liquidus of peridotite. Given that most estimates of lunar bulk composition are peridotitic, the partitioning models thus lend themselves to calculation of <span class="hlt">olivine</span> compositions produced during the early stages of magma ocean crystallization. Calculation of <span class="hlt">olivine</span> compositions produced by fractional crystallization of a model lunar magma ocean, initially 700 km deep, reveals a prominent maximum in Ni concentration versus fraction crystallized or Mg' (molar MgO/(MgO + FeO)), but a pattern of monotonically increasing Co concentration. These patterns qualitatively match the puzzling patterns of Ni and Co concentrations observed in lunar rocks in which forsteritic <span class="hlt">olivines</span> in magnesian suite cumulates have lower Ni and Co abundances than do less magnesian <span class="hlt">olivines</span> from low-Ti mare basalts, and <span class="hlt">olivines</span> from the ferroan anorthosite suite (FAS) have lower Ni, but similar Co to mare basalt <span class="hlt">olivines</span>. The Ni and Co abundances in <span class="hlt">olivines</span> from the magnesian suite cumulates can be reconciled in terms of fractional crystallization of a deep magma ocean which initially produces a basal dunite comprised of the hottest and most magnesian <span class="hlt">olivine</span> overlain by an <span class="hlt">olivine</span>-orthopyroxene (harzburgite) layer that is in turn overlain by an upper zone of plagioclase-bearing cumulates. The ultramafic portion of the cumulate pile overturns sending the denser harzburgite layer, which later becomes a portion of the green glass source region, to the bottom of the cumulate pile with Ni- and Co-rich <span class="hlt">olivine</span>. Meanwhile, the less dense, but hottest, most magnesian <span class="hlt">olivines</span> with much lower Ni and Co abundances are transported upward to the base of the plagioclase-bearing cumulates where subsequent heat transfer leads to melting of mixtures of primary dunite, norite, and gabbronorite with KREEP (a K-REE-P enriched component widely believed to be derived from the very latest stage magma ocean liquid). These hybrid melts have Al 2O 3, Ni, and Co abundances and Mg' appropriate for parent magmas of the magnesian suite. Ni and Co abundances in the FAS are consistent with either direct crystallization from the magma ocean or crystallization of melts of primary dunite-norite mixtures without KREEP.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19860058985&hterms=PYRRHOTITE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DPYRRHOTITE','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19860058985&hterms=PYRRHOTITE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DPYRRHOTITE"><span id="translatedtitle">Mineralogy of interplanetary dust particles from the '<span class="hlt">olivine</span>' infrared class</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Christoffersen, R.; Buseck, P. R.</p> <p>1986-01-01</p> <p>Analytical electron microscopy observations establish that <span class="hlt">olivine</span> is abundant and the predominant silicate phase in three interplanetary dust particles (IDPs) from the '<span class="hlt">olivine</span>' infrared spectra category. Two of the particles have microstructures resembling those of most nonhydrous chondritic IDPs, consisting of micron to submicron grains together with a matrix composed of amorphous carbonaceous material and sub-500 A grains. In addition to <span class="hlt">olivine</span> these particles respectively contain enstatite and magnetite, and pentlandite plus Ca-rich clinopyroxene. The third IDP consists mostly of <span class="hlt">olivine</span> and pyrrhotite with little or no matrix material. <span class="hlt">Olivine</span> grains in this particle contain prominent solar-flare ion tracks with densities corresponding to a space-exposure age between 1000 to 100,000 years. Although the three particles have <span class="hlt">olivine</span>-rich mineralogies in common, other aspects of their mineralogies and microstructures suggest that they experienced different formation histories. The differences between the particles indicate that the <span class="hlt">olivine</span> infrared spectral category is a diverse collection of IDPs that probably incorporates several genetic groups.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Litho.220..238B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Litho.220..238B"><span id="translatedtitle">The <span class="hlt">olivine</span> macrocryst problem: New insights from minor and trace element compositions of <span class="hlt">olivine</span> from Lac de Gras kimberlites, Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bussweiler, Yannick; Foley, Stephen F.; Prelević, Dejan; Jacob, Dorrit E.</p> <p>2015-04-01</p> <p>This study presents detailed petrographical and geochemical investigations on remarkably fresh <span class="hlt">olivines</span> in kimberlites from the EKATI Diamond Mine™ located in the Tertiary/Cretaceous Lac de Gras kimberlite field within the Slave craton of Canada. <span class="hlt">Olivine</span>, constituting about 42 vol.% of the analyzed samples, can be divided into two textural groups: (i) macrocrystic <span class="hlt">olivines</span>, > 100 μm sub-rounded crystals and (ii) groundmass <span class="hlt">olivines</span>, < 100 μm subhedral crystals. <span class="hlt">Olivines</span> from both populations define two distinct chemical trends; a "mantle trend" with angular cores, showing low Ca (< 0.1 wt.% CaO) and high Ni (0.3-0.4 wt.% NiO) at varying Mg# (0.86-0.93), contrasts with a "melt trend" typified by thin (< 100 μm) rims with increasing Ca (up to 1.0 wt.% CaO) and decreasing Ni (down to 0.1 wt.% NiO) contents at constant Mg# (~ 0.915). These findings are in agreement with recent studies suggesting that virtually all <span class="hlt">olivine</span> is composed of xenocrystic (i.e. mantle-related) cores with phenocrystic (i.e. melt-related) overgrowths, thereby challenging the traditional view that the origin of kimberlitic <span class="hlt">olivine</span> can be distinguished based on size and morphology. The two main trends can be further resolved into sub-groups refining the crystallization history of <span class="hlt">olivine</span>; the mantle trend indicates a multi-source origin that samples the layered lithosphere below the Slave craton, whereas the melt trend represents multi-stage crystallization comprising a differentiation trend starting at mantle conditions and a second trend controlled by the crystallization of additional phases (e.g. chromite) and changing magma conditions (e.g. oxidation). These trends are also seen in the concentrations of trace elements not routinely measured in <span class="hlt">olivine</span> (e.g. Na, P, Ti, Co, Sc, Zr). Trace element mapping with LA-ICP-MS reveals the distribution of these elements within <span class="hlt">olivine</span> grains. The trace element distribution between the two trends appears to be consistent with phenocrystic <span class="hlt">olivine</span> overgrowths mainly originating from dissolved orthopyroxene, showing enrichment in Zr, Ga, Nb, Sc, V, P, Al, Ti, Cr, Ca and Mn in the melt trend. In a sample of magmatic kimberlite from the Leslie pipe, the amount of xenocrystic and phenocrystic <span class="hlt">olivine</span> is estimated to be around 23 vol.% and 19 vol.%, respectively. Subtraction of this xenocrystic <span class="hlt">olivine</span> from the Leslie bulk composition, aimed at estimating the parental kimberlite melt, results in a minor decrease of Mg# (by about 0.01) and SiO2 content (by about 3 wt.%), whereas CaO increases (by about 3 wt.%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20781536','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20781536"><span id="translatedtitle">Carbon sequestration via aqueous <span class="hlt">olivine</span> mineral carbonation: role of passivating layer formation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hamdallah Bearat; Michael J. McKelvy; Andrew V.G. Chizmeshya; Deirdre Gormley; Ryan Nunez; R.W. Carpenter; Kyle Squires; George H. Wolf</p> <p>2006-08-01</p> <p>CO{sub 2} sequestration via carbonation of widely available low-cost minerals, such as <span class="hlt">olivine</span>, can permanently dispose of CO{sub 2} in an environmentally benign and a geologically stable form. The paper reports the results of studies of the mechanisms that limit aqueous <span class="hlt">olivine</span> carbonation reactivity under the optimum sequestration reaction conditions observed to date: 1 M NaCl + 0.64 M NaHCO{sub 3} at T {approx} 185{sup o}C and P{sub CO{sub 2}} {approx} 135 <span class="hlt">bar</span>. A reaction limiting silica-rich passivating layer (PL) forms on the feedstock grains, slowing carbonate formation and raising process cost. The morphology and composition of the passivating layers are investigated using scanning and transmission electron microscopy and atomic level modeling. Postreaction analysis of feedstock particles, recovered from stirred autoclave experiments at 1500 rpm, provides unequivocal evidence of local mechanical removal (chipping) of PL material, suggesting particle abrasion. This is corroborated by the observation that carbonation increases dramatically with solid particle concentration in stirred experiments. Multiphase hydrodynamic calculations are combined with experiment to better understand the associated slurry-flow effects. Large-scale atomic-level simulations of the reaction zone suggest that the PL possesses a 'glassy' but highly defective SiO{sub 2} structure that can permit diffusion of key reactants. Mitigating passivating layer effectiveness is critical to enhancing carbonation and lowering sequestration process cost. 30 refs., 7 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5771518','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5771518"><span id="translatedtitle">Composite carrier <span class="hlt">bar</span> device</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Felder, D.W.</p> <p>1981-09-01</p> <p>A composite carrier <span class="hlt">bar</span> is disclosed for oil well pumping units that utilize sucker rod to operate bottom hole pumps. The <span class="hlt">bar</span> includes a recessed cavity for receiving a hydraulic ram to operate as a polish rod jack and also a secondary carrier <span class="hlt">bar</span> for receiving a secondary polish rod clamp for use in respacing bottom hole pumps and serve as a safety clamp during operation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRB..116.1203F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRB..116.1203F"><span id="translatedtitle">Dislocation creep of fine-grained <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faul, U. H.; Fitz Gerald, J. D.; Farla, R. J. M.; Ahlefeldt, R.; Jackson, I.</p> <p>2011-01-01</p> <p>Deformation experiments conducted in a gas medium apparatus at temperatures from 1200 to 1350°C with a fine-grained, solution-gelation derived Fe-bearing <span class="hlt">olivine</span> show a stress dependence of the strain rate at stresses above ˜150 MPa, which is much stronger than previously reported for polycrystalline samples. The data can be fit by a power law with ??σn with n ˜ 7-8, or equally well by a Peierls creep law with exponential stress dependence. Due to the observed strong stress dependence the samples deform at significantly higher strain rates at a given stress than single crystals or coarse-grained polycrystals with n ˜ 3.5. TEM observations indicate the presence of dislocations with at least two different Burgers vectors, with free dislocations predominantly of screw character. Subgrain walls are present but are only weakly developed and have small misorientation angles. Both the rheology and dislocation structures are consistent with creep rate-limited by dislocation glide or cross slip for aggregates with grain sizes smaller than or approaching the recrystallized grain size. Deformation mechanism maps extrapolated to lithospheric temperatures using the melt-free diffusion creep rheology of Faul and Jackson (2007), the dislocation creep rheology of Hirth and Kohlstedt (2003), and the results described here indicate that deformation conditions of ultramylonitic shear zones fall near the triple point of Peierls, dislocation, and diffusion creep.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeCoA..70..206F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeCoA..70..206F"><span id="translatedtitle">Vapor pressures and evaporation coefficients for melts of ferromagnesian <span class="hlt">chondrule</span>-like compositions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fedkin, A. V.; Grossman, L.; Ghiorso, M. S.</p> <p>2006-01-01</p> <p>To determine evaporation coefficients for the major gaseous species that evaporate from silicate melts, the Hertz-Knudsen equation was used to model the compositions of residues of <span class="hlt">chondrule</span> analogs produced by evaporation in vacuum by Hashimoto [Hashimoto A. (1983) Evaporation metamorphism in the early solar nebula-evaporation experiments on the melt FeO-MgO-SiO 2-CaO-Al 2O 3 and chemical fractionations of primitive materials. Geochem. J. 17, 111-145] and Wang et al. [Wang J., Davis A. M., Clayton R. N., Mayeda T. K., Hashimoto A. (2001) Chemical and isotopic fractionation during the evaporation of the FeO-MgO-SiO 2-CaO-Al 2O 3-TiO 2 rare earth element melt system. Geochim. Cosmochim. Acta 65, 479-494], in vacuum and in H 2 by Yu et al. [Yu Y., Hewins R. H., Alexander C. M. O'D., Wang J. (2003) Experimental study of evaporation and isotopic mass fractionation of potassium in silicate melts. Geochim. Cosmochim. Acta 67, 773-786], and in H 2 by Cohen et al. [Cohen B. A., Hewins R. H., Alexander C. M. O'D. (2004) The formation of <span class="hlt">chondrules</span> by open-system melting of nebular condensates. Geochim. Cosmochim. Acta 68, 1661-1675]. Vapor pressures were calculated using the thermodynamic model of Ghiorso and Sack [Ghiorso M. S., Sack R. O. (1995) Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures. Contrib. Mineral. Petrol. 119, 197-212], except for the late, FeO-free stages of the Wang et al. (2001) and Cohen et al. (2004) experiments, where the CMAS activity model of Berman [Berman R. G. (1983) A thermodynamic model for multicomponent melts, with application to the system CaO-MgO-Al 2O 3-SiO 2. Ph.D. thesis, University of British Columbia] was used. From these vapor pressures, evaporation coefficients ( α) were obtained that give the best fits to the time variation of the residue compositions. Evaporation coefficients derived for Fe (g), Mg (g), and SiO (g) from the Hashimoto (1983) experiments are similar to those found by Alexander [Alexander C. M. O'D. (2004) Erratum. Meteoritics Planet. Sci. 39, 163] in his EQR treatment of the same data and also adequately describe the FeO-bearing stages of the Wang et al. (2001) experiments. From the Yu et al. (2003) experiments at 1723 K, αNa = 0.26 ± 0.05, and αK = 0.13 ± 0.02 in vacuum, and αNa = 0.042 ± 0.020, and αK = 0.017 ± 0.002 in 9 × 10 -5 <span class="hlt">bar</span> H 2. In the FeO-free stages of the Wang et al. (2001) experiments, αMg and αSiO are significantly different from their respective values in the FeO-bearing portions of the same experiments and from the vacuum values obtained at the same temperature by Richter [Richter F. M., Davis A. M., Ebel D. S., Hashimoto A. (2002) Elemental and isotopic fractionation of Type B calcium-, aluminum-rich inclusions: experiments, theoretical considerations, and constraints on their thermal evolution. Geochim. Cosmochim. Acta 66, 521-540] for CMAS compositions much lower in MgO. When corrected for temperature, the values of αMg and αSiO that best describe the FeO-free stages of the Wang et al. (2001) experiments also adequately describe the FeO-free stage of the Cohen et al. (2004) H 2 experiments, but αFe that best describes the FeO-bearing stage of the latter experiment differs significantly from the temperature-corrected value derived from the Hashimoto (1983) vacuum data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P31E1738O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P31E1738O"><span id="translatedtitle"><span class="hlt">Olivine</span> Deposits Associated with Impact Basins and Craters on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ody, A.; Poulet, F.; Langevin, Y.; Gondet, B.; Bibring, J.; Carter, J.</p> <p>2011-12-01</p> <p>An analysis of the 1?m <span class="hlt">olivine</span> spectral signature applied to the entire and final OMEGA dataset [1] shows numerous <span class="hlt">olivine</span>-bearing deposits in the 3 main basins of Mars (Argyre, Isidis and Hellas). These signatures are among the strongest of Mars, which suggests compositions with higher iron content and/or larger grain size and/or larger abundance than the ones of widespread <span class="hlt">olivine</span>-bearing deposits observed on large parts of the southern highlands [1]. A spectral modeling based on a radiative transfer model [2] indicates that their compositions are still close to the forsterite one with abundance in the range of [15,40%] and grain sizes of a few hundreds of ?m. These deposits are exclusively localized on Noachian terrains. Distribution of these deposits around Argyre basin clearly takes the form of discontinuous patches of <span class="hlt">olivine</span>-bearing rocks on the basin terrace, which strongly suggest that their formation is related to the basin formation event. Recent numerical simulations of basin formation show that impact that formed the Argyre basin could have excavated upper mantle materials and emplaced discontinuous patches of melted mantle on the basin terraces [3]. The observed <span class="hlt">olivine</span> deposits in Argyre are thus interpreted as <span class="hlt">olivine</span>-bearing material excavated from the upper mantle during the impact. <span class="hlt">Olivine</span> deposits distribution around the Hellas basin is not as clear as for Argyre because of young resurfacing processes that strongly affected its region. <span class="hlt">Olivine</span> deposits are fewer and mainly localized on the northern terrace of Hellas. Most of them are detected in crater ejecta, while a few similar to Argyre <span class="hlt">olivine</span> discontinuous patches are also observed suggesting that a mantle origin as for Argyre is possible. <span class="hlt">Olivine</span> has been detected by several datasets in the Nili Fossae region and in the south of Isidis basin. The spectral modeling of OMEGA spectra indicates an <span class="hlt">olivine</span> abundance of about 40% and megacrysts of several millimeters for the region of Nili Fossae [2]. Several plausible hypotheses has been discussed to explain this unusual concentration of <span class="hlt">olivine</span>-rich outcrops in Nili Fossae assuming three possibilities for their emplacement relative to the formation of the Isidis basin : pre-impact [4,5], contemporaneous [6], or post-impact [7]. The pretty unique settings and compositions of these deposits in comparison to the two other major basins indicate a different origin, with the post-impact one as the preferred one. Other several localized exposures with strong <span class="hlt">olivine</span> signature are also found throughout the southern highlands and the northern plains mostly associated with craters. <span class="hlt">Olivine</span>-bearing material is found in craters floors but also in some crater ejecta implying the presence of an <span class="hlt">olivine</span>-rich underlying layer. Of special interest are some craters totally filled by <span class="hlt">olivine</span>-rich lava lakes, which could have erupted through local (impact-related) fractures. [1] A. Ody et al. (2011) LPSC XXXXII.[2] F. Poulet et al. (2009), Icarus 201, 84-101.[3] Stewart S. (2010) AGU, San Francisco, abstract #P43A-08. [4] Hoefen et al. (2003) Science,302,627-630.[5] Hamilton and Christensen (2005), Geology,33,433-436.[6]J.F. Mustard et al. (2007), JGR, 112, E08S03.[7] L.L Tornabene et al. (2008), JGR, 113, E10001.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020045838&hterms=Basalt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBasalt','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020045838&hterms=Basalt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBasalt"><span id="translatedtitle">Systematics of Vanadium in <span class="hlt">Olivine</span> from Planetary Basalts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Karner, J. M.; Papike, J. J.; Shearer, C. K.</p> <p>2002-01-01</p> <p>The systematics of vanadium in <span class="hlt">olivines</span> from the Earth, Moon and Mars allows for the comparison of planetary basalt origin and igneous setting and process. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010045242&hterms=Weathering&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DWeathering','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010045242&hterms=Weathering&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DWeathering"><span id="translatedtitle"><span class="hlt">Olivine</span> Weathering: Abiotic Versus Biotic Processes as Possible Biosignatures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Longazo, T. G.; Wentworth, S. J.; McKay, D. S.; Southam, G.; Clemett, S. J.</p> <p>2001-01-01</p> <p>A preliminary study to determine how abiotic versus biotic processes affect the weathering of <span class="hlt">olivine</span> crystals. Perhaps the differences between these weathering processes could be used as biosignatures. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008047','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008047"><span id="translatedtitle"><span class="hlt">Olivine</span> and Pyroxene Compositions in Fine-Grained Chondritic Materials</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zolensky, Michael E.; Frank, D.</p> <p>2011-01-01</p> <p>Our analyses of the Wild-2 samples returned by the Stardust Mission have illuminated critical gaps in our understanding of related astromaterials. There is a very large database of <span class="hlt">olivine</span> and low-calcium pyroxene compositions for coarse-grained components of chondrites, but a sparse database for anhydrous silicate matrix phases. In an accompanying figure, we present comparisons of Wild-2 <span class="hlt">olivine</span> with the available chondrite matrix <span class="hlt">olivine</span> major element data. We thus have begun a long-term project measuring minor as well as major element compositions for chondrite matrix and chondritic IDPs, and Wild 2 grains. Finally, we wish to re-investigate the changes to fine-grained <span class="hlt">olivine</span> and low-Ca pyroxene composition with progressive thermal metamorphism. We have examined the LL3-4 chondrites which because of the Hayabusa Mission have become very interesting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1878.2034N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1878.2034N"><span id="translatedtitle">The Microstructure of a Micrometeorite Impact into Lunar <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noble, S. K.; Keller, L. P.; Christoffersen, R.; Rahman, Z.</p> <p>2015-11-01</p> <p>Through TEM analysis of the cross-section of a ~20 µm diameter crater into an <span class="hlt">olivine</span> single crystal we can see first-hand the effects of a single impact, including the creation of nanophase iron in the melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.8517A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.8517A"><span id="translatedtitle">Aluminum speeds up the hydrothermal alteration of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andreani, Muriel; Daniel, Isabelle; Pollet-Villard, Marion</p> <p>2014-05-01</p> <p>The reactivity of ultramafic rocks toward hydrothermal fluids controls chemical fluxes at the interface between the internal and external reservoirs of silicate planets. On Earth, hydration of ultramafic rocks is ubiquitous and operates from deep subduction zones to shallow lithospheric environments where it considerably affects the physical and chemical properties of rocks and can interact with the biosphere. This process also has key emerging societal implications, such as the production of hydrogen as a source of carbon-free energy. To date, the chemical model systems used to reproduce <span class="hlt">olivine</span> hydrothermal alteration lead to the formation of serpentine with sluggish reaction rates. Although aluminum is common in geological environments and in hydrothermal systems in particular, its role in serpentinization or <span class="hlt">olivine</span> dissolution has not been investigated under hydrothermal conditions. Nevertheless, abundant Al supply is expected in fluids released from dehydration of metapelites in subduction zones as well as during the hydrothermal alteration of gabbros at mid-ocean ridges. Aluminum was also abundant in primitive environments of both the Earth and Mars, stored in either Al-rich minerals like plagioclase or Al-enriched ultramafic lavas. We have investigated the role of Al on the hydrothermal alteration of <span class="hlt">olivine</span> in a series of experiments performed in a low-pressure diamond anvil cell while following the reaction progress in situ by optical imaging and Raman spectroscopy. Experiments were run for 4.5 to 7.5 days with two <span class="hlt">olivine</span> grains reacted in saline water (0.5 molal NaCl) at 200C and 300C, and P=200 MPa. After two days, <span class="hlt">olivine</span> crystals were fully transformed to an aluminous serpentine, also enriched in iron. The presence of Al in the hydrothermal fluid increases the rate of <span class="hlt">olivine</span> serpentinization by more than one order of magnitude by enhancing <span class="hlt">olivine</span> solubility and serpentine precipitation. The mechanism responsible for this increased solubility has to be further investigated but this result motivates a re-evaluation of the natural rates of <span class="hlt">olivine</span> serpentinization and of <span class="hlt">olivine</span> hydrolysis in general in a wide range of settings where <span class="hlt">olivines</span> or peridotites are intimately associated with Al-providers. Such a fast reaction rate may affect the contribution of reaction-enhanced processes at the micrometer-scale, such as reaction-driven cracking, already proposed for enhancing serpentinization or carbonation of <span class="hlt">olivine</span>. The effect of Al on lower crust and upper mantle metasomatism is expected to be even stronger at higher pressure in subduction zones where those reactions control the rheology and physical properties of the subducting plate and mantle wedge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70012903','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70012903"><span id="translatedtitle">Dissolution of <span class="hlt">olivine</span> in basaltic liquids: experimental observations and applications.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Thornber, C.R.; Huebner, J.S.</p> <p>1985-01-01</p> <p>Rates of <span class="hlt">olivine</span> dissolution in synthetic lunar basalt 77115 and a silica-enriched 77115 composition (Sil-77115) at superliquidus temperatures have been determined. Dissolution-rate data have been applied to the problem of the thermal history of fragment-laden impact-melt rocks of the lunar highlands. Textural and chemical criteria are discussed for the recognition of <span class="hlt">olivine</span> resorption (and growth) phenomena in igneous rocks. -J.A.Z.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.V31D0972A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.V31D0972A"><span id="translatedtitle">Microstructures of <span class="hlt">Olivine</span> in the Weakly Shocked Divnoe Meteorite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ando, J.; Tomioka, N.; Petaev, M. L.; Kanagawa, K.; Honda, K.; Shibata, Y.; Yamanaka, S.</p> <p>2003-12-01</p> <p>Many microstructural observations of minerals in meteorites show evidences of shock effect, but rarely give data about the parent body. However, the microstructures of minerals in achondrites may retain the important information about the parent body which gives a basic idea about the formation of internal structural of the Earth. We carried out microstructural and microfabric analyses of <span class="hlt">olivine</span> grains in the Divnoe meteorite by optical microscopy, electron probe microanalysis, electron back-scattered diffraction (EBSD) analysis, and transmission electron microscopy (TEM) with the selected area electron diffraction, in order to search the microstructures produced in the parent body. The Divnoe meteorite is a granoblastic, <span class="hlt">olivine</span>-rich primitive achondrite. Neither black shock veins nor pockets of silicate melt typical of heavily shocked meteorites were found. Most <span class="hlt">olivine</span> grains exhibit weak undulose extinction. Some grains show mosaic extinction though this is not as pronounced as in heavily shocked meteorites, and lamellar Fe-Mg zoning (2 to 4 mole percent Fa). The weak shock metamorphism experienced by Divnoe is consistent with the shock stage S3. The EBSD analysis of the Divnoe <span class="hlt">olivine</span> grains reveals a distinct crystallographic preferred orientation (CPO) characterized by a [001] density maximum and girdle distributions of [100] and [010] around the [001] maximum. This type of fabric is not known in crystal-plastically deformed Earths mantle rocks, and can be explained by rigid body rotation of <span class="hlt">olivines</span> in matrix flow. It suggests that this CPO was formed by rotation of <span class="hlt">olivine</span> grains in strong melt flows on the meteorite parent bodies, so that their longest [001] axes were aligned parallel to the flow direction. Therefore, Divnoe should preserve an initial CPO of <span class="hlt">olivine</span> formed during crystallization in the parent body that has not been significantly disturbed by later processes such as thermal and shock metamorphism. Now, the microstructures such as dislocations and inclusions within the single crystal <span class="hlt">olivines</span> showing the CPO which should retain the important information about the parent body are examining by TEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990091993&hterms=boo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dboo','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990091993&hterms=boo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dboo"><span id="translatedtitle">Thermal Emission Spectroscopy of 1 Ceres: Evidence for <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Witteborn, F. C.; Roush, T. L.; Cohen, M.</p> <p>1999-01-01</p> <p>Thermal emission spectra of the largest asteroid 1 Ceres obtained from the Kuiper Airborne Observatory display features that may provide information on its surface mineralogy. A plot of the Ceres spectrum (calibrated using alpha Boo as a standard) divided by a standard thermal model (STM) is shown. Also shown is the emissivity spectrum deduced from reflectivity measurements for <span class="hlt">olivine</span> grains <5 microns in diameter. The general shape of the Ceres and the <span class="hlt">olivine</span> curves agree in essential details, such as the maxima from 8 to 12 microns, the minimum between 12 and 14 microns, the broad peak near 17.5 micron, and the slope beyond 22 micron. (Use of the 10 to 15-micron grain reflectivities provides a better match to the 12- to 14-micron dip. We used a value of unity for beta, the beaming factor associated with small-scale surface roughness in our STM. Adjustment of beta to a lower value raises the long-wavelength side of the Ceres spectrum, providing an even better match to the <span class="hlt">olivine</span> curve.) The emissivity behavior roughly matches the emission coefficients which were calculated for <span class="hlt">olivine</span> particles with a particle radius of 3 microns. Their calculations show not only the negative slope from 23 to 25 pm, but a continued decrease past 30 micron. The Ceres emissivity is thus similar to that of small <span class="hlt">olivine</span> grains from 8 to 30 micron, but <span class="hlt">olivine</span>'s emissivity is lower from 5 to 8 pm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160002410','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160002410"><span id="translatedtitle"><span class="hlt">Chondrules</span> and Opaque Phases in Unequilibrated R Chondrites: A Comprehensive Assessment of Their Formation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, K. E.; Lauretta, D. S.; Connolly, H. C., Jr.; Berger, E. L.; Domanik, K.</p> <p>2016-01-01</p> <p>Equilibrated Rumuruti (R) chondrites record an oxygen fugacity between 0 and 3.5 log units below the fayalite-magnetite-quartz buffer, and a sulfur fugacity (fS2) 2 log units above the iron-troilite buffer. They are more than an order of magnitude more oxidized than the ordinary chondrites [1], and orders of magnitude more sulfidized than solar values. Although the R chondrites have the highest (delta)O-17 value of any meteorites, analyses of unequilibrated R chondrites indicate <span class="hlt">chondrule</span> formation in an oxygen isotope reservoir similar to that of the ordinary chondrite <span class="hlt">chondrules</span>. We present the relationship of the R chondrite parent body to pre-accretionary volatiles O and S based on our analyses of unequilibrated R chondrite material in two thin sections from the meteorite Mount Prestrud (PRE) 95404.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930068398&hterms=CAIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCAIS','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930068398&hterms=CAIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DCAIS"><span id="translatedtitle">Secondary processing of <span class="hlt">chondrules</span> and refractory inclusions (CAIs) by gasdynamic heating</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Podolak, M.; Prialnik, D.; Bunch, T. E.; Cassen, P.; Reynolds, R.</p> <p>1993-01-01</p> <p>Results of calculations performed to determine the conditions necessary for producing the opaque rims on <span class="hlt">chondrules</span> and CAI rims by high-speed entry into the transient atmosphere of an accreting meteorite parent body are presented. The sensitivity of these results to variations in critical parameters is investigated. The range of entry velocities which can produce such rims is shown to depend on the size, melting temperature, and thermal conductivity of the particles. For particles greater than 2 mm in radius, with thermal conductivities of 20,000 ergs/sm s K or lower, entry velocities of about 3 km/s suffice. For particle sizes less than 1 mm in radius, the range of encounter velocities that can produce rims is narrow or vanishing, regardless of the thermal conductivity, unless the melting temperature in the outer part of the <span class="hlt">chondrule</span> has been reduced by compositional heterogeneity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=205105','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=205105"><span id="translatedtitle"><span class="hlt">Bar</span>-biting</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p><span class="hlt">Bar</span> biting is regarded as a stereotypic behavior in which the animal carries out repetitive mouthing and biting of the metal <span class="hlt">bars</span> in its environmental enclosure. It is commonly seen in sows housed in close confinement, in barren environments, and with restricted access to food. However, it has also ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeCoA.164...17D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeCoA.164...17D"><span id="translatedtitle">Triple oxygen isotope exchange between <span class="hlt">chondrule</span> melt and water vapor: An experimental study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Rocco, Tommaso; Pack, Andreas</p> <p>2015-09-01</p> <p>We have conducted time and ƒO2-dependent oxygen isotope exchange experiments between <span class="hlt">chondrule</span> analogue melts and H2O in the phase. The aim of our study is to address the question whether the oxygen isotope composition of <span class="hlt">chondrules</span> is the result of exchange with the ambient nebular gas or has been inherited from the precursor material. The silicate melt-H2O vapor exchange experiments were carried out in a vertical gas-mixing furnace using the metal loop technique at 1500 °C. The duration ranged from 5 to 1440 min and ƒO2 was set between IW - 3.8 and IW - 1.3 using the H2O/H2 buffer. Our experiments show that 50% exchange between H2O gas and silicate melt occurs in ∼4 h at ƒO2 = IW - 3.8 and in ∼1 h at ƒO2 = IW - 1.3. At solar nebula conditions, significant exchange occurs only if <span class="hlt">chondrule</span>-melting times were several hours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20010000046&hterms=multifractal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmultifractal','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20010000046&hterms=multifractal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmultifractal"><span id="translatedtitle">Size-Selective Concentration of <span class="hlt">Chondrules</span> and Other Small Particles in Protoplanetary Nebula Turbulence</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cuzzi, Jeffrey N.; Hogan, Robert C.; Paque, Julie M.; Dobrovolskis, Anthony R.; DeVincenzi, Donald L. (Technical Monitor)</p> <p>2000-01-01</p> <p>Size-selective concentration of particles in a weakly turbulent protoplanetary nebula may be responsible for the initial collection of <span class="hlt">chondrules</span> and other constituents into primitive bodY precursors. This paper presents the main elements of this process of turbulent concentration. In the terrestrial planet region. both the characteristic size and size distribution of <span class="hlt">chondrules</span> are explained. "Fluffier" particles would be concentrated in nebula regions which were at a lower density and/or more intensely turbulent. The spatial distribution of concentrated particle density obeys multifractal scaling, suggesting a close tie to the turbulent cascade process. This scaling behavior allows predictions of the probability distributions for concentration in the protoplanetary nebula to be made. Large concentration factors (less than 10(exp 5)) are readily obtained, implying that numerous zones of particle density significantly exceeding the gas density could exist. If most of the available solids were actually in <span class="hlt">chondrule</span> sized particles, the ensuing particle mass density would become so large that the feedback effects on gas turbulence due to mass loading could no longer be neglected. This paper describes the process, presenting its basic elements and some implications, without including the effects of mass loading.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013M%26PS...48.2430S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013M%26PS...48.2430S"><span id="translatedtitle">81Kr-Kr cosmic ray exposure ages of individual <span class="hlt">chondrules</span> from Allegan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strashnov, I.; Gilmour, J. D.</p> <p>2013-12-01</p> <p>81Kr-Kr cosmic ray exposure (CRE) ages of individual <span class="hlt">chondrules</span> (6-10 mg) and adjacent matrix samples (5-10 mg) from the Allegan H5 chondrite have been measured using a new highly sensitive resonance ionization mass spectrometer. No conclusive evidence of variations among the CRE ages of individual <span class="hlt">chondrules</span> or between <span class="hlt">chondrules</span> and matrix has been observed—average CRE ages of 5.90 ± 0.42 Ma (81Kr-78Kr) and 5.04 ± 0.37 Ma (81Kr-80+82Kr) are identical within error to those determined for the matrix (7.42 ± 1.27 Myr, 81Kr-80+82Kr) and agree well with the literature value for bulk Allegan. If any accumulation of cosmogenic krypton in the early solar system took place, either it was below our detection limit in these samples (<100 atoms), or any such gas was lost during parent body metamorphism. However, this demonstration that useful 81Kr-Kr ages can be obtained from few milligram samples of chondritic material has clear relevance to the analysis of samples returned by planned missions to asteroids and to the search for a signature of pre-exposure in other, less processed meteorites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16174733','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16174733"><span id="translatedtitle">Volatile fractionation in the early solar system and <span class="hlt">chondrule</span>/matrix complementarity.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bland, Philip A; Alard, Olivier; Benedix, Gretchen K; Kearsley, Anton T; Menzies, Olwyn N; Watt, Lauren E; Rogers, Nick W</p> <p>2005-09-27</p> <p>Bulk chondritic meteorites and terrestrial planets show a monotonic depletion in moderately volatile and volatile elements relative to the Sun's photosphere and CI carbonaceous chondrites. Although volatile depletion was the most fundamental chemical process affecting the inner solar nebula, debate continues as to its cause. Carbonaceous chondrites are the most primitive rocks available to us, and fine-grained, volatile-rich matrix is the most primitive component in these rocks. Several volatile depletion models posit a pristine matrix, with uniform CI-like chemistry across the different chondrite groups. To understand the nature of volatile fractionation, we studied minor and trace element abundances in fine-grained matrices of a variety of carbonaceous chondrites. We find that matrix trace element abundances are characteristic for a given chondrite group; they are depleted relative to CI chondrites, but are enriched relative to bulk compositions of their parent meteorites, particularly in volatile siderophile and chalcophile elements. This enrichment produces a highly nonmonotonic trace element pattern that requires a complementary depletion in <span class="hlt">chondrule</span> compositions to achieve a monotonic bulk. We infer that carbonaceous chondrite matrices are not pristine: they formed from a material reservoir that was already depleted in volatile and moderately volatile elements. Additional thermal processing occurred during <span class="hlt">chondrule</span> formation, with exchange of volatile siderophile and chalcophile elements between <span class="hlt">chondrules</span> and matrix. This chemical complementarity shows that these chondritic components formed in the same nebula region. PMID:16174733</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008Icar..197..269M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008Icar..197..269M"><span id="translatedtitle">Origin of three-dimensional shapes of <span class="hlt">chondrules</span>. I. Hydrodynamics simulations of rotating droplet exposed to high-velocity rarefied gas flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miura, Hitoshi; Nakamoto, Taishi; Doi, Masao</p> <p>2008-09-01</p> <p>The origin of three-dimensional shapes of <span class="hlt">chondrules</span> is an important information to identify their formation mechanism in the early solar nebula. The measurement of their shapes by using X-ray computed topography suggested that they are usually close to perfect spheres, however, some of them have rugby-ball-like (prolate) shapes [Tsuchiyama, A., Shigeyoshi, R., Kawabata, T., Nakano, T., Uesugi, K., Shirono, S., 2003. Lunar Planet. Sci. 34, 1271-1272]. We considered that the prolate shapes reflect the deformations of <span class="hlt">chondrule</span> precursor dust particles when they are heated and melted in the high velocity gas flow. In order to reveal the origin of <span class="hlt">chondrule</span> shapes, we carried out the three-dimensional hydrodynamics simulations of a rotating molten <span class="hlt">chondrule</span> exposed to the gas flow in the framework of the shock-wave heating model for <span class="hlt">chondrule</span> formation. We adopted the gas ram pressure acting on the <span class="hlt">chondrule</span> surface of p=10 dyncm in a typical shock wave. Considering that the <span class="hlt">chondrule</span> precursor dust particle has an irregular shape before melting, the ram pressure causes a net torque to rotate the particle. The estimated angular velocity is ω=140 rads for the precursor radius of r=1 mm, though it has a different value depending on the irregularity of the shape. In addition, the rotation axis is likely to be perpendicular to the direction of the gas flow. Our calculations showed that the rotating molten <span class="hlt">chondrule</span> elongates along the rotation axis, in contrast, shrinks perpendicularly to it. It is a prolate shape. The reason why the molten <span class="hlt">chondrule</span> is deformed to a prolate shape was clearly discussed. Our study gives a complementary constraint for <span class="hlt">chondrule</span> formation mechanisms, comparing with conventional chemical analyses and dynamic crystallization experiments that have mainly constrained the thermal evolutions of <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.178...87T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.178...87T"><span id="translatedtitle">Mobility of iron and nickel at low temperatures: Implications for 60Fe-60Ni systematics of <span class="hlt">chondrules</span> from unequilibrated ordinary chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Telus, Myriam; Huss, Gary R.; Ogliore, Ryan C.; Nagashima, Kazuhide; Howard, Daryl L.; Newville, Matthew G.; Tomkins, Andrew G.</p> <p>2016-04-01</p> <p>The Fe and Ni isotopic composition of ferromagnesian silicates in <span class="hlt">chondrules</span> from unequilibrated ordinary chondrites (UOCs) have been used to estimate the initial abundance of the short-lived radionuclide, 60Fe, in the early Solar System. However, these estimates vary widely, and there are systematic discrepancies in initial 60Fe/56Fe ratios inferred from in situ and bulk analyses of <span class="hlt">chondrules</span>. A possible explanation is that the Fe-Ni isotope system in UOC <span class="hlt">chondrules</span> has not remained closed (a necessary condition for isotopic dating), and Fe and Ni have been redistributed since the <span class="hlt">chondrules</span> formed. In order to evaluate this, we collected high-spatial-resolution X-ray fluorescence (XRF) maps of UOC <span class="hlt">chondrules</span> to better understand the distribution and mobility of Fe and Ni at the low metamorphic temperatures of these chondrites. We used synchrotron X-ray-fluorescence microscopy to map the distribution of Fe, Ni and other elements in portions of 71 <span class="hlt">chondrules</span> from 8 UOCs (types 3.00-3.2). The synchrotron XRF maps show clear enrichment of Fe and/or Ni in fractures ranging down to micrometer scale in <span class="hlt">chondrules</span> from all UOCs analyzed for this study regardless of petrologic type and regardless of whether fall or find, indicating that there was significant exchange of Fe and Ni between <span class="hlt">chondrules</span> and matrix and that the Fe-Ni system was not closed. Sixty percent of <span class="hlt">chondrules</span> in Semarkona (LL3.00) have Fe and Ni enrichment along fractures, while 80-100% of <span class="hlt">chondrules</span> analyzed from the other UOCs show these enrichments. Mobilization was likely a result of fluid transport of Fe and Ni during aqueous alteration on the parent body and/or during terrestrial weathering. In situ and bulk Fe-Ni analyses that incorporate extraneous Fe and Ni from <span class="hlt">chondrule</span> fractures will result in lowering the inferred initial 60Fe/56Fe ratios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR33C..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR33C..06M"><span id="translatedtitle">Grain boundary diffusion in <span class="hlt">olivine</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marquardt, K.; Dohmen, R.</p> <p>2013-12-01</p> <p><span class="hlt">Olivine</span> is the main constituent of Earth's upper mantle. The individual mineral grains are separated by grain boundaries that have very distinct properties compared to those of single crystals and strongly affect large-scale physical and chemical properties of rocks, e.g. viscosity, electrical conductivity and diffusivity. Knowledge on the grain boundary physical and chemical properties, their population and distribution in polycrystalline materials [1] is a prerequisite to understand and model bulk (rock) properties, including their role as pathways for element transport [2] and the potential of grain boundaries as storage sites for incompatible elements [3]. Studies on selected and well characterized single grain boundaries are needed for a detailed understanding of the influence of varying grain boundaries. For instance, the dependence of diffusion on the grain boundary structure (defined by the lattice misfit) and width in silicates is unknown [2, 4], but limited experimental studies in material sciences indicate major effects of grain boundary orientation on diffusion rates. We characterized the effect of grain boundary orientation and temperature on element diffusion in forsterite grain boundaries by transmission electron microscopy (TEM).The site specific TEM-foils were cut using the focused ion beam technique (FIB). To study diffusion we prepared amorphous thin-films of Ni2SiO4 composition perpendicular to the grain boundary using pulsed laser deposition. Annealing (800-1450°C) leads to crystallization of the thin-film and Ni-Mg inter-diffuse into the crystal volume and along the grain boundary. The inter-diffusion profiles were measured using energy dispersive x-ray spectrometry in the TEM, standardized using the Cliff-Lorimer equation and EMPA measurements. We obtain volume diffusion coefficients that are comparable to Ni-Mg inter-diffusion rates in forsterite determined in previous studies at comparable temperatures, with similar activation energies. Grain boundary diffusion perpendicular to the dislocation lines of the small angle grain boundaries proved to be about an order of magnitude faster than volume diffusion, whereas diffusion in high angle grain boundaries is several orders of magnitude faster. We will discuss the variation of element diffusion rates with grain boundary orientation and the temperature- and/or time-induced transition from one diffusion regime to the next regime. This is done using time series experiments and two-dimensional grain boundary diffusion simulations. Finally, we will debate the differences between our data and other data sets that result from different experimental setups, conditions and analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.V13D..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.V13D..04D"><span id="translatedtitle">A Method for the Flux Growth of Intermediate Composition <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deangelis, M. T.; Anovitz, L. M.; Labotka, T. C.; Frederick, D. A.</p> <p>2009-05-01</p> <p>Though solid solution of iron and magnesium between forsterite (Mg2SiO4) and fayalite (Fe2SiO4) is possible in the <span class="hlt">olivine</span> crystal structure, the high oxygen fugacity condition of the terrestrial mantle inhibits the widespread crystallization of intermediate (Fo40-Fo60) composition <span class="hlt">olivine</span>. This limitation is not the same for some other inner solar system bodies (e.g. the Moon and Mars), where conditions are reducing and <span class="hlt">olivine</span> compositions are wide ranging. Unfortunately, the amount of samples from the Moon and Mars is extremely limited; with only Apollo and Luna mission samples, lunar meteorites, and Martian meteorites available for direct mineralogic and petrologic characterization. These characterizations have provided a useful basis for many spectroscopic and modeling interpretations, but many fundamental questions remain and may only be answerable through either direct observation of rocks or by analog experimentation. The motivation for our work on growth of intermediate <span class="hlt">olivine</span> crystals, therefore, is to create realistic starting material for use in Mars and Moon analog experiments. A variety of crystal growth methods have been previously used to synthesize <span class="hlt">olivine</span>, including: the Czochralski-pulling (CZ) method, the floating-zone image furnace (FZ) method, and sol-gel processing techniques. Both the CZ and FZ methods have the advantage of producing large crystals, but the growth apparatus and regulation of reduced atmospheric conditions during growth can make these techniques both time and cost intensive. Sol-gel processing to produces <span class="hlt">olivine</span> fibers is a useful chemical technique, but obtaining larger grain sizes can be difficult. An alternative method for crystal growth is through the use a flux, which can grow crystals relatively quickly and inexpensively. We have grown synthetic crystals of intermediate composition (Fo30-Fo70) <span class="hlt">olivine</span> using a lithium borate (B5Li3O9) flux. The starting material was a mixture of magnesite (MgCO3), siderite (FeCO3), and quartz (SiO2) powder in a 1:1:1 ratio. The advantage of using siderite is that the iron is already present in the ferrous form. Upon heating and decarbonation, this mixture represents a bulk composition of Fo50 (FeMgSiO4) <span class="hlt">olivine</span>. Flux was then added to the starting material mixture so that the final mixture was 50% starting material and 50% flux by weight. This final mix was then placed in a platinum crucible that was heated to 1100 °C in a vacuum furnace for three days. The use of a vacuum furnace ensured that conditions remained reducing during crystal growth. The result was growth of <span class="hlt">olivine</span> crystals that are generally small (< 1 mm in length) and have euhedral crystal form. These crystals have been analyzed by electron microprobe, and are systematically zoned from core to rim with Mg-rich cores (˜Fo70) transitioning to Fe-rich rims (˜Fo30). This zoning represents an expected heterogeneity due to <span class="hlt">olivine</span> growth from a finite reservoir of starting material. The flux growth of this intermediate composition <span class="hlt">olivine</span> was primarily a 'proof of concept' experiment, and showed that <span class="hlt">olivine</span> crystals can be grown using a flux under sub-solidus conditions. Additional crystal growth experiments would be useful to gauge the response of <span class="hlt">olivine</span> to changes in temperature, duration, and composition of the flux + starting material mixture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/573752','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/573752"><span id="translatedtitle">Formation of a metastable <span class="hlt">olivine</span> wedge in a descending slab</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Devaux, J.P.; Schubert, G.; Anderson, C.</p> <p>1997-11-01</p> <p>We present a thermal model of a descending slab in which the transformation of <span class="hlt">olivine</span> to spinel is controlled by pressure- and temperature-dependent reaction kinetics. Two different formulations of the kinetics are considered with the main discriminant being the temperature range over which <span class="hlt">olivine</span> converts to spinel at pressures of about 15 GPa (about 500{degree}{endash}515{degree}C and 560{degree}{endash}650{degree}C). We use a finite element method to solve the coupled heat conduction (perpendicular and parallel to the dip of the slab) and kinetics equations, and we include the latent heat of the phase transformation. Latent heat release together with heat conduction parallel to the dip of the slab reduces significantly the length of the metastable <span class="hlt">olivine</span> wedge and results in a very thin ({approx_lt}5km) two-phase region. We employ the thermal parameter v{tau}sin{delta} (v is the velocity of the descending slab, {tau} is the age of the slab, and {delta} is the dip of the slab to the horizontal) to interpret the results for the length of the metastable wedge. For values of the thermal parameter smaller than about 4000 and 7000 km, depending on the model of the kinetics, no metastable <span class="hlt">olivine</span> wedge exists (the critical value of 7000 km for the thermal parameter corresponds to the kinetics model with the lowest transition temperature range). The length of the metastable <span class="hlt">olivine</span> wedge is also found to be very sensitive to the model of the kinetics and to the effects of adiabatic heating. If the occurrence of deep earthquakes is related to the transformation of metastable <span class="hlt">olivine</span> to spinel, then data on earthquake depth versus thermal parameter require that the onset of the reaction takes place at temperatures of about 550{degree}{endash}575{degree}C. In this case the slab thermal parameter must be larger than 10,000 km for the metastable <span class="hlt">olivine</span> wedge to extend down to 660 km depth. But deep earthquakes occur near 660 km depth in slabs with thermal parameter as small as about 5000 km (South America, for example). Either some deep earthquakes are unrelated to <span class="hlt">olivine</span> metastability or our knowledge of <span class="hlt">olivine</span>-spinel reaction kinetics is incomplete.{copyright} 1997 American Geophysical Union</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70037122','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70037122"><span id="translatedtitle">Extraction of in situ cosmogenic 14C from <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pigati, J.S.; Lifton, N.A.; Timothy, Jull A.J.; Quade, Jay</p> <p>2010-01-01</p> <p>Chemical pretreatment and extraction techniques have been developed previously to extract in situ cosmogenic radiocarbon (in situ 14C) from quartz and carbonate. These minerals can be found in most environments on Earth, but are usually absent from mafic terrains. To fill this gap, we conducted numerous experiments aimed at extracting in situ 14C from <span class="hlt">olivine</span> ((Fe,Mg)2SiO4). We were able to extract a stable and reproducible in situ 14C component from <span class="hlt">olivine</span> using stepped heating and a lithium metaborate (LiBO2) flux, following treatment with dilute HNO3 over a variety of experimental conditions. However, measured concentrations for samples from the Tabernacle Hill basalt flow (17.3 ?? 0.3 ka4) in central Utah and the McCarty's basalt flow (3.0 ?? 0.2 ka) in western New Mexico were significantly lower than expected based on exposure of <span class="hlt">olivine</span> in our samples to cosmic rays at each site. The source of the discrepancy is not clear. We speculate that in situ 14C atoms may not have been released from Mg-rich crystal lattices (the <span class="hlt">olivine</span> composition at both sites was ~Fo65Fa35). Alternatively, a portion of the 14C atoms released from the <span class="hlt">olivine</span> grains may have become trapped in synthetic spinel-like minerals that were created in the <span class="hlt">olivine</span>-flux mixture during the extraction process, or were simply retained in the mixture itself. Regardless, the magnitude of the discrepancy appears to be inversely proportional to the Fe/(Fe+Mg) ratio of the <span class="hlt">olivine</span> separates. If we apply a simple correction factor based on the chemical composition of the separates, then corrected in situ 14C concentrations are similar to theoretical values at both sites. At this time, we do not know if this agreement is fortuitous or real. Future research should include measurement of in situ 14C concentrations in <span class="hlt">olivine</span> from known-age basalt flows with different chemical compositions (i.e. more Fe-rich) to determine if this correction is robust for all <span class="hlt">olivine</span>-bearing rocks. ?? 2010 by the Arizona Board of Regents on behalf of the University of Arizona.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeCoA.135..170D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeCoA.135..170D"><span id="translatedtitle">Weathering of <span class="hlt">olivine</span> under CO2 atmosphere: A martian perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dehouck, E.; Gaudin, A.; Mangold, N.; Lajaunie, L.; Dauzères, A.; Grauby, O.; Le Menn, E.</p> <p>2014-06-01</p> <p>Recent analyses from the Curiosity rover at Yellowknife Bay (Gale crater, Mars) show sedimentary rocks deposited in a lacustrine environment and containing smectite clays thought to derive from the alteration of <span class="hlt">olivine</span>. However, little is known about the weathering processes of <span class="hlt">olivine</span> under early martian conditions, and about the stability of smectite clays in particular. Here, we present a 3-month experiment investigating the weathering of forsteritic <span class="hlt">olivine</span> powders (Fo90) under a dense CO2 atmosphere, and under present-day terrestrial conditions for comparison. The experiment also evaluates the potential effects of hydrogen peroxide (H2O2), as a representation of the highly oxidizing compounds produced by photochemical reactions throughout martian history. The weathered samples were characterized by means of near-infrared spectroscopy (NIR), X-ray diffraction (XRD), transmission electron microscopy with energy dispersive X-ray spectrometry (TEM-EDX), Mössbauer spectroscopy and thermogravimetry. The results show that a Mg-rich smectite phase formed from the weathering of <span class="hlt">olivine</span> under CO2 conditions, although in lower abundance than under terrestrial conditions. The main secondary phase formed under CO2 turns out to be a silica-rich phase (possibly acting as a “passivating” layer) with a non-diagnostic near-infrared spectral signature. The use of H2O2 highlights the critical importance of both the redox conditions and Fe content of the initial <span class="hlt">olivine</span> on the nature of the secondary phases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050175999','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050175999"><span id="translatedtitle">Tracing Oxygen Fugacity in Asteroids and Meteorites Through <span class="hlt">Olivine</span> Composition</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sunshine, J. M.; Bus, S. J.; Burbine, T. H.; McCoy, T. J.</p> <p>2005-01-01</p> <p><span class="hlt">Olivine</span> absorptions are known to dominate telescopic spectra of several asteroids. Among the meteorite collection, three groups (excluding Martian meteorites), the pallasites, brachinites, and R group chondrites are plausible analogs to <span class="hlt">olivine</span>-rich asteroids in that they are dominated by <span class="hlt">olivine</span>. These meteorite groups have distinct petrologic origins. The primitive achondrite brachinites (which include both depleted and undeleted subgroups) are products of relatively minor differentiation and evolved in oxidizing environments. R chondrites are also thought to have formed in high oxygen states, but are closely related to ordinary chondrites (yet with their own distinct compositions and oxygen isotopic signatures). In contrast, pallasites, widely thought to be mantle components from much more evolved bodies, formed in more reducing environments. Petrologic indicators that are identifiable in spectral data must be used in order to infer the petrologic history of asteroids from surveys of their actual population. As discussed below, <span class="hlt">olivine</span> composition (e.g. Fa#) can provide key constraints in exploring the origin and significance of <span class="hlt">olivine</span> dominated asteroids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1051809','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1051809"><span id="translatedtitle"><span class="hlt">Olivine</span> Composite Cathode Materials for Improved Lithium Ion Battery Performance</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ward, R.M.; Vaughey, J.T.</p> <p>2006-01-01</p> <p>Composite cathode materials in lithium ion batteries have become the subject of a great amount of research recently as cost and safety issues related to LiCoO2 and other layered structures have been discovered. Alternatives to these layered materials include materials with the spinel and <span class="hlt">olivine</span> structures, but these present different problems, e.g. spinels have low capacities and cycle poorly at elevated temperatures, and <span class="hlt">olivines</span> exhibit extremely low intrinsic conductivity. Previous work has shown that composite structures containing spinel and layered materials have shown improved electrochemical properties. These types of composite structures have been studied in order to evaluate their performance and safety characteristics necessary for use in lithium ion batteries in portable electronic devices, particularly hybrid-electric vehicles. In this study, we extended that work to layered-<span class="hlt">olivine</span> and spinel-<span class="hlt">olivine</span> composites. These materials were synthesized from precursor salts using three methods: direct reaction, ball-milling, and a coreshell synthesis method. X-ray diffraction spectra and electrochemical cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-<span class="hlt">olivine</span> composites make them a promising class for the next generation of lithium ion battery cathodes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000081089&hterms=Condensation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DCondensation','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000081089&hterms=Condensation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DCondensation"><span id="translatedtitle"><span class="hlt">Chondrules</span> of the Very First Generation in Bencubbin/CH-like Meteorites QUE94411 and Hammadah Al Hamra 237: Condensation Origin at High Ambient Nebular Temperatures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krot, Alexander N.; Meibom, Anders; Russell, Sara S.; Young, Edward; Alexander, Conel M.; McKeegan, Kevin D.; Lofgren, Gary; Cuzzi, Jeff; Zipfel, Jutta; Keil, Klaus</p> <p>2000-01-01</p> <p><span class="hlt">Chondrules</span> in QUE94411 and HH 237 formed at high ambient T prior to condensation of Fe,Ni-metal following a large scale thermal event that resulted in complete vaporization of a solar nebula region. These <span class="hlt">chondrules</span> escaped subsequent remelting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870017808','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870017808"><span id="translatedtitle">Mass modeling for <span class="hlt">bars</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Butler, Thomas G.</p> <p>1987-01-01</p> <p>Methods of modeling mass for <span class="hlt">bars</span> are surveyed. A method for extending John Archer's concept of consistent mass beyond just translational inertia effects is included. Recommendations are given for various types of modeling situations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010000326','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010000326"><span id="translatedtitle">Thermal Emission Spectroscopy of 1 Ceres: Evidence for <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Witteborn, Fred. C.; Roush, Ted L.; Cohen, Martin</p> <p>1999-01-01</p> <p>Thermal emission spectra of the largest asteroid, 1 Ceres, obtained from the Kuiper Airborne Observatory display features that may provide information about its surface mineralogy. The emissivity, obtained by dividing the spectra by a standard thermal model, is compared with emissivity spectra of <span class="hlt">olivines</span> and phyllosilicates deduced via Kirchoff's law from reflectivity measurements. The spectra provide a fairly good match to fine grained <span class="hlt">olivines</span> (0 to 5 micrometer size range). The smoothness of the spectrum beyond 18 micrometers is an indication of particles smaller than 50 micrometers. While the abrupt rise in emissivity near 8 micrometers matches many silicates, the distinct emissivity minimum centered near 12.8 micrometers is consistant with iron-poor <span class="hlt">olivines</span>, but not with phyllosilicates. It suggests the presence of opaques and does not exclude a mixture with organics and fine-grained phyllosilicates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..258..467N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..258..467N"><span id="translatedtitle">Exogenic <span class="hlt">olivine</span> on Vesta from Dawn Framing Camera color data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nathues, Andreas; Hoffmann, Martin; Schäfer, Michael; Thangjam, Guneshwar; Le Corre, Lucille; Reddy, Vishnu; Christensen, Ulrich; Mengel, Kurt; Sierks, Holger; Vincent, Jean-Baptist; Cloutis, Edward A.; Russell, Christopher T.; Schäfer, Tanja; Gutierrez-Marques, Pablo; Hall, Ian; Ripken, Joachim; Büttner, Irene</p> <p>2015-09-01</p> <p>In this paper we present the results of a global survey of <span class="hlt">olivine</span>-rich lithologies on (4) Vesta. We investigated Dawn Framing Camera (FC) High Altitude Mapping Orbit (HAMO) color cubes (∼60 m/pixel resolution) by using a method described in Thangjam et al. (Thangjam, G., Nathues, A., Mengel, K., Hoffmann, M., Schäfer, M., Reddy, V., Cloutis, E.A., Christensen, U., Sierks, H., Le Corre, L., Vincent, J.-B, Russell, C.T. [2014b]. Meteorit. Planet. Sci. arXiv:1408.4687 [astro-ph.EP]). In total we identified 15 impact craters exhibiting <span class="hlt">olivine</span>-rich (>40 wt.% ol) outcrops on their inner walls, some showing <span class="hlt">olivine</span>-rich material also in their ejecta and floors. <span class="hlt">Olivine</span>-rich sites are concentrated in the Bellicia, Arruntia and Pomponia region on Vesta's northern hemisphere. From our multi-color and stratigraphic analysis, we conclude that most, if not all, of the <span class="hlt">olivine</span>-rich material identified is of exogenic origin, i.e. remnants of A- or/and S-type projectiles. The <span class="hlt">olivine</span>-rich lithologies in the north are possibly ejecta of the ∼90 km diameter Albana crater. We cannot draw a final conclusion on their relative stratigraphic succession, but it seems that the dark material (Nathues, A., Hoffmann, M., Cloutis, E.A., Schäfer, M., Reddy, V., Christensen, U., Sierks, H., Thangjam, G.S., Le Corre, L., Mengel, K., Vincent, J.-B., Russell, C.T., Prettyman, T., Schmedemann, N., Kneissl, T., Raymond, C., Gutierrez-Marques, P., Hall, I. Büttner, I. [2014b]. Icarus (239, 222--237)) and the <span class="hlt">olivine</span>-rich lithologies are of a similar age. The origin of some potential <span class="hlt">olivine</span>-rich sites in the Rheasilvia basin and at crater Portia are ambiguous, i.e. these are either of endogenic or exogenic origin. However, the small number and size of these sites led us to conclude that <span class="hlt">olivine</span>-rich mantle material, containing more than 40 wt.% of <span class="hlt">olivine</span>, is basically absent on the present surface of Vesta. In combination with recent impact models of Veneneia and Rheasilvia (Clenet, H., Jutzi, M., Barrat, J.-A., Gillet, Ph. [2014]. Lunar Planet Sci. 45, #1349; Jutzi, M., Asphaug, E., Gillet, P., Barrat, J.-A., Benz, W. [2013]. Nature 494, 207-210), which predict an excavation depth of up to 80 km, we are confident that the crust-mantle depth is significantly deeper than predicted by most evolution models (30 km; Mittlefehldt, D.W. [2014]. Asteroid 4 Vesta: A Fully Differentiated Dwarf Planet. NASA Technical Reports Server (20140004857.pdf)) or, alternatively, the <span class="hlt">olivine</span>-content of the (upper) mantle is lower than our detection limit, which would lead to the conclusion that Vesta's parent material was already depleted in <span class="hlt">olivine</span> compared to CI meteorites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/15800614','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/15800614"><span id="translatedtitle">An <span class="hlt">olivine</span>-free mantle source of Hawaiian shield basalts.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sobolev, Alexander V; Hofmann, Albrecht W; Sobolev, Stephan V; Nikogosian, Igor K</p> <p>2005-03-31</p> <p>More than 50 per cent of the Earth's upper mantle consists of <span class="hlt">olivine</span> and it is generally thought that mantle-derived melts are generated in equilibrium with this mineral. Here, however, we show that the unusually high nickel and silicon contents of most parental Hawaiian magmas are inconsistent with a deep <span class="hlt">olivine</span>-bearing source, because this mineral together with pyroxene buffers both nickel and silicon at lower levels. This can be resolved if the <span class="hlt">olivine</span> of the mantle peridotite is consumed by reaction with melts derived from recycled oceanic crust, to form a secondary pyroxenitic source. Our modelling shows that more than half of Hawaiian magmas formed during the past 1 Myr came from this source. In addition, we estimate that the proportion of recycled (oceanic) crust varies from 30 per cent near the plume centre to insignificant levels at the plume edge. These results are also consistent with volcano volumes, magma volume flux and seismological observations. PMID:15800614</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000ASPC..196..197W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000ASPC..196..197W"><span id="translatedtitle">Thermal Emission Spectroscopy of 1 Ceres: Evidence For <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Witteborn, Fred C.; Roush, Ted L.; Cohen, Martin</p> <p>2000-03-01</p> <p>Thermal emission spectra of the largest asteroid, 1 Ceres, obtained from the Kuiper Airborne Observatory display features that may provide information about its surface mineralogy. The emissivity, obtained by dividing the spectra by a standard thermal model, is compared with emissivity spectra of <span class="hlt">olivines</span> and phyllosilicates deduced via Kirchoff's law from reflectivity measurements. The spectra provide a fairly good match to fine grained <span class="hlt">olivines</span> (0 to 5 μm size range). The smoothness of the spectrum beyond 18 μm is an indication of particles smaller than 50 μm. While the abrupt rise in emissivity near 8 μm matches many silicates, the distinct emissivity minimum centered near 12.8 μm is consistant with iron-poor <span class="hlt">olivines</span>, but not with phyllosilicates. It suggests the presence of opaques and does not exclude a mixture with organics and fine-grained phyllosilicates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930028356&hterms=metamorphism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmetamorphism','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930028356&hterms=metamorphism&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmetamorphism"><span id="translatedtitle">Chemical and physical studies of chondrites. X - Cathodoluminescence and phase composition studies of metamorphism and nebular processes in <span class="hlt">chondrules</span> of type 3 ordinary chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dehart, John M.; Lofgren, Gary E.; Jie, LU; Benoit, Paul H.; Sears, Derek W. G.</p> <p>1992-01-01</p> <p>The cathodoluminescence (CL) characteristics of eight type-3 ordinary chondrites and one L5 chondrite were investigated with particular emphasis on detailed compositions of the relevant phases in four of these chondrites: Semarkona (type-3.0); Krymka (3.1); Allan Hills A77214 (3.5); and Dhajala (3.8). By sorting the <span class="hlt">chondrules</span> into eight groups according to the CL of mesostasis and to certain compositional criteria and by determining the number of <span class="hlt">chondrules</span> in these groups as a function of petrological type, it was possible to deduce genetic/evolutionary sequences of the <span class="hlt">chondrules</span>. It is shown that there are major compositional differences in <span class="hlt">chondrules</span>, which account for their CL properties and the <span class="hlt">chondrule</span> groups.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040059918&hterms=olivine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dolivine','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040059918&hterms=olivine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dolivine"><span id="translatedtitle">A Survey of <span class="hlt">Olivine</span> Alteration Products Using Raman Spectroscopy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuebler, K.; Jolliff, B. L.; Wang, A.; Haskin, L. A.</p> <p>2004-01-01</p> <p>Identification of mineral alteration products will aid in the crucial task of interpreting past Martian environmental conditions, especially aqueous environments. <span class="hlt">Olivine</span> has been identified at the surface of Mars and is readily altered in aqueous environments. Using Raman spectroscopy, we studied three rocks with altered <span class="hlt">olivine</span> and compared the data with mineral chemistry from electron microprobe analysis. Although the alteration in all three samples has loosely been called iddingsite their appearances and modes of occurrences differ as described. Alteration products in all three samples are likely fine-grained mixtures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/898859','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/898859"><span id="translatedtitle">Grinding methods to enhance the reactivity of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Summers, Cathy A.; Dahlin, David C.; Rush, Gilbert E.; O'Connor, William K.; Gerdemann, Stephen J.</p> <p>2004-01-01</p> <p>The Albany Research Center (ARC) conducted studies of mechanical activation by conventional and ultra-fine grinding techniques to enhance <span class="hlt">olivine</span> reactivity in mineral carbonation reactions. Activated <span class="hlt">olivine</span> is one of several solid feed materials used at ARC in reactions with carbon dioxide to form carbonate minerals. This paper compares grinding techniques via energy demand data and product characteristics, including particle size distributions, surface areas, full width at half maximum (FWHM) XRD analyses, and particle morphology by SEM analyses. Reactivity was gauged by percent conversion to carbonate in subsequent carbonation tests.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRE..118..234O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRE..118..234O"><span id="translatedtitle">Global investigation of <span class="hlt">olivine</span> on Mars: Insights into crust and mantle compositions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ody, A.; Poulet, F.; Bibring, J.-P.; Loizeau, D.; Carter, J.; Gondet, B.; Langevin, Y.</p> <p>2013-02-01</p> <p>present the distribution of <span class="hlt">olivine</span> on Mars, derived from spectral parameters based on the 1 µm <span class="hlt">olivine</span> absorption band. The <span class="hlt">olivine</span> can be defined with respect to two spectral end-members: type 1 corresponds to <span class="hlt">olivine</span> with low iron content and/or small grain size and/or small abundance, and type 2, which corresponds to <span class="hlt">olivine</span> with higher iron content and/or larger grain size and/or larger abundance. The spatial and statistical analysis of the global <span class="hlt">olivine</span> distribution points out five major geological settings where <span class="hlt">olivine</span> is detected: (1) Early Hesperian <span class="hlt">olivine</span>-bearing smooth crater floors and flat intercrater plains throughout the southern highlands; (2) <span class="hlt">olivine</span> deposits around the three main basins Argyre, Hellas, and Isidis; (3) <span class="hlt">olivine</span> in intercrater dunes, crater ejecta, or extended deposits in the northern plains; (4) <span class="hlt">olivine</span> associated with outcrops and sand in the floor of Valles Marineris; and (5) <span class="hlt">olivine</span>-bearing butte outcrops in the vicinity of Hellas. The geological context, the age, and the composition of the <span class="hlt">olivine</span> detections associated with these five major geological settings are detailed. Their origin and the implication of their occurrence on the composition of the Martian mantle and crust, as well as on the evolution of Mars volcanism are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMGP43A0886K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMGP43A0886K"><span id="translatedtitle">Magnetic Paleofield of Avanhandava H4 Chondrite's Matrix and <span class="hlt">Chondrules</span> - Implications on Magnetic Fields in Early Solar System.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kohout, T.; Pesonen, L. J.</p> <p>2005-12-01</p> <p>The Avanhandava (H4) fall occurred in 1952 in Brazil. A total of 9.33 kg had been preserved after the meteorite brake up during the impact [1]. The meteorite contains large (0.1 - 2.0 mm) <span class="hlt">chon-drules</span> that have clearly delineated boundaries with matrix. This characteristic allows us to pick up oriented individual <span class="hlt">chondrules</span> and study their magnetic properties. The <span class="hlt">chondrules</span> of the Avanhandava meteorite show a low and randomly oriented NRM (10-2 - 10-1 mAm2/kg). In contrast the matrix is strongly (100 - 101 mAm2/kg) and uniformly magnet-ized [2]. Various methods for paleofield determination have been applied on matrix and individual <span class="hlt">chondrules</span> in order to determine possi-ble magnetizing processes and paleofields in early solar systems.. The laboratory experiments reveal approximate paleofields for matrix similar to present geomagnetic field. The paleofield de-termined for <span class="hlt">chondrules</span> is approximately one order of magnitude lower comparing to values obtained for matrix. That suggests that <span class="hlt">chondrules</span> are not magnetically contaminated by geomagnetic or artificial fields and they acquired their NRM prior their aggregation to Avanhandava parent body (random NRM directions). The matrix shows remarkable traces of terres-trial weathering and is uniformly magnetized. The paleofield re-sult for matrix indicates possible remagnetization caused by ter-restrial weathering. The terrestrial weathering of ordinary chon-drites is observed even on falls stored in museums and can sig-nificantly influence meteorite magnetic records [3, 4]. References: [1] Paar W. et al. 1976. Revista Brasileira de Geo-ciencias 6: 201-210. [2] Kohout T. and Pesonen L. J. 2005. 68th Annual Meteoritical Society Meeting: 5202. [3] Kohout T. et al. 2004. Physics and Chemistry of the Earth 29: 885-897. [4] Lee M. R. and Bland P. A. 2004. Geochimica et Cosmochimica Acta 68: 893-916.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120007401','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120007401"><span id="translatedtitle">Trace Element Compositions of Pallasite <span class="hlt">Olivine</span> Grains and Pallasite Origin</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mittlefehldt, David W.; Herrin, J. S.</p> <p>2010-01-01</p> <p>Pallasites are mixtures of metal with magnesian <span class="hlt">olivine</span>. Most have similar metal compositions and <span class="hlt">olivine</span> oxygen isotopic compositions; these are the main-group pallasites (PMG). The Eagle Station grouplet of pallasites (PES) have distinctive metal and <span class="hlt">olivine</span> compositions and oxygen isotopic compositions. Pallasites are thought to have formed at the core-mantle boundary of their parent asteroids by mixing molten metal with solid <span class="hlt">olivine</span> of either cumulatic or restitic origin. We have continued our investigation of pallasite <span class="hlt">olivines</span> by doing in situ trace element analyses in order to further constrain their origin. We determined Al, P, Ca, Ga and first row transition element contents of <span class="hlt">olivine</span> grains from suite of PMG and PES by LA-ICP-MS at JSC. Included in the PMG suite are some that have anomalous metal compositions (PMG-am) and atypically ferroan <span class="hlt">olivines</span> (PMG-as). Our EMPA work has shown that there are unanticipated variations in <span class="hlt">olivine</span> Fe/Mn, even within those PMG that have uni-form Fe/Mg. Manganese is homologous with Fe2+, and thus can be used the same way to investigate magmatic fractionation processes. It has an advantage for pallasite studies in that it is unaffected by redox exchange with the metal. PMG can be divided into three clusters on the basis of Mn/Mg; low, medium and high that can be thought of as less, typically and more fractionated in an igneous sense. The majority of PMG have medium Mn/Mg ratios. PMG-am occur in all three clusters; there does not seem to be any relationship between putative <span class="hlt">olivine</span> igneous fractionation and metal composition. The PMG-as and one PMG-am make up the high Mn/Mg cluster; no PMG are in this cluster. The high Mn/Mg cluster ought to be the most fractionated (equivalent to the most Fe-rich in igneous suites), yet they have among the lowest contents of incompatible lithophile elements Al and Ti and the two PMG-as in this cluster also have low Ca and Sc contents. This is inconsistent with simple igneous fractionation on a single, initially homogeneous parent asteroid. For Al and Ti, the low and high Mn/Mg clusters have generally uniform contents, while the medium cluster has wide ranges. This is also true of analyses of duplicate grains from the medium cluster pallasites which can have very different Al and Ti contents. Those from the low and high clusters do not. These observations suggest that pallasite <span class="hlt">olivines</span> are not cumulates, but rather are restites from high degrees of melting. The moderately siderophile elements P and Ga show wide ranges in the high Mn/Mg cluster, but very uniform compositions in the medium cluster, opposite the case for Al and Ti. There is no correlation of P or Ga and Fe/Mn as might be expected if redox processes controlled the contents of moderately siderophile elements in the <span class="hlt">olivines</span>. The lack of correlation of P could reflect equilibration with phosphates, although there is no correlation of Ca with P as might be expected</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR33B2335A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR33B2335A"><span id="translatedtitle">Influence of aluminum on the hydrothermal alteration rate of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andreani, M.; Daniel, I.; Pollet-Villard, M.</p> <p>2013-12-01</p> <p>The reactivity of ultramafic rocks under hydrothermal conditions controls chemical fluxes at the interface between the internal and external reservoirs of silicate planets. On Earth, hydration of ultramafic rocks is ubiquitous and operates from deep subduction zones to shallow lithospheric environments where it considerably affects the physical and chemical properties of rocks and can interact with the biosphere. This process also has key emerging societal implications, such as the production of hydrogen as a source of carbon-free energy. To date, the chemical model systems used to reproduce <span class="hlt">olivine</span> hydrothermal alteration lead to the formation of serpentine with sluggish reaction rates. Although aluminum is common in geological environments and in hydrothermal systems in particular, its role in serpentinization or <span class="hlt">olivine</span> dissolution has not been investigated under hydrothermal conditions. Nevertheless, abundant Al supply is expected in fluids released from dehydration of metapelites in subduction zones as well as during the hydrothermal alteration of gabbros at mid-ocean ridges. Aluminum was also abundant in primitive environments of both the Earth and Mars, stored in either Al-rich minerals like plagioclase or Al-enriched ultramafic lavas. We have investigated the role of Al on the hydrothermal alteration of <span class="hlt">olivine</span> in a series of experiments performed in a low-pressure diamond anvil cell while following the reaction progress in situ by optical imaging and by confocal Raman spectroscopy. Experiments were run for 4.5 to 7.5 days with two <span class="hlt">olivine</span> grains reacted in saline water (0.5 molal NaCl) at 200C and 300C, and P=200 MPa. After two days, <span class="hlt">olivine</span> crystals were fully transformed to an aluminous serpentine, also enriched in iron. The very fast precipitation of serpentine may inhibit magnetite nucleation here. However, this does not rule out an H2 production since serpentines classically incorporate non negligible amount of ferric iron in their structure. The presence of Al in the hydrothermal fluid increases the rate of <span class="hlt">olivine</span> serpentinization by more than one order of magnitude by increasing <span class="hlt">olivine</span> solubility and enhancing serpentine precipitation. The mechanism responsible for this increased solubility has to be investigated further but this result motivates a re-evaluation of the natural rates of <span class="hlt">olivine</span> serpentinization and of <span class="hlt">olivine</span> hydrolysis in general in a wide range of settings where <span class="hlt">olivines</span> or peridotites are intimately associated with Al-providers. Such a fast reaction rate may affect the contribution of reaction-enhanced processes at the micrometer-scale, such as reaction-driven cracking, already proposed for enhancing serpentinization or carbonation of <span class="hlt">olivine</span>. The effect of Al on lower crust and upper mantle metasomatism is expected to be even stronger at higher pressure in subduction zones where those reactions control the rheology and physical properties of the subducting plate and mantle wedge. Finally, this study also provides a way to accelerate serpentinization reactions towards economically feasible time-scale and temperature for industrial H2 production and/or CO2 remediation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CoMP..168.1030N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CoMP..168.1030N"><span id="translatedtitle">Chemical zonation in <span class="hlt">olivine</span>-hosted melt inclusions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Newcombe, M. E.; Fabbrizio, A.; Zhang, Youxue; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.</p> <p>2014-07-01</p> <p>Significant zonation in major, minor, trace, and volatile elements has been documented in naturally glassy <span class="hlt">olivine</span>-hosted melt inclusions from the Siqueiros Fracture Zone and the Galapagos Islands. Components with a higher concentration in the host <span class="hlt">olivine</span> than in the melt (e.g., MgO, FeO, Cr2O3, and MnO) are depleted at the edges of the zoned melt inclusions relative to their centers, whereas except for CaO, H2O, and F, components with a lower concentration in the host <span class="hlt">olivine</span> than in the melt (e.g., Al2O3, SiO2, Na2O, K2O, TiO2, S, and Cl) are enriched near the melt inclusion edges. This zonation is due to formation of an <span class="hlt">olivine</span>-depleted boundary layer in the adjacent melt in response to cooling and crystallization of <span class="hlt">olivine</span> on the walls of the melt inclusions, concurrent with diffusive propagation of the boundary layer toward the inclusion center. Concentration profiles of some components in the melt inclusions exhibit multicomponent diffusion effects such as uphill diffusion (CaO, FeO) or slowing of the diffusion of typically rapidly diffusing components (Na2O, K2O) by coupling to slow diffusing components such as SiO2 and Al2O3. Concentrations of H2O and F decrease toward the edges of some of the Siqueiros melt inclusions, suggesting either that these components have been lost from the inclusions into the host <span class="hlt">olivine</span> late in their cooling histories and/or that these components are exhibiting multicomponent diffusion effects. A model has been developed of the time-dependent evolution of MgO concentration profiles in melt inclusions due to simultaneous depletion of MgO at the inclusion walls due to <span class="hlt">olivine</span> growth and diffusion of MgO in the melt inclusions in response to this depletion. Observed concentration profiles were fit to this model to constrain their thermal histories. Cooling rates determined by a single-stage linear cooling model are 150-13,000 C h-1 from the liquidus down to ~1,000 C, consistent with previously determined cooling rates for basaltic glasses; compositional trends with melt inclusion size observed in the Siqueiros melt inclusions are described well by this simple single-stage linear cooling model. Despite the overall success of the modeling of MgO concentration profiles using a single-stage cooling history, MgO concentration profiles in some melt inclusions are better fit by a two-stage cooling history with a slower-cooling first stage followed by a faster-cooling second stage; the inferred total duration of cooling from the liquidus down to ~1,000 C ranges from 40 s to just over 1 h. Based on our observations and models, compositions of zoned melt inclusions (even if measured at the centers of the inclusions) will typically have been diffusively fractionated relative to the initially trapped melt; for such inclusions, the initial composition cannot be simply reconstructed based on <span class="hlt">olivine</span>-addition calculations, so caution should be exercised in application of such reconstructions to correct for post-entrapment crystallization of <span class="hlt">olivine</span> on inclusion walls. Off-center analyses of a melt inclusion can also give results significantly fractionated relative to simple <span class="hlt">olivine</span> crystallization. All melt inclusions from the Siqueiros and Galapagos sample suites exhibit zoning profiles, and this feature may be nearly universal in glassy, <span class="hlt">olivine</span>-hosted inclusions. If so, zoning profiles in melt inclusions could be widely useful to constrain late-stage syneruptive processes and as natural diffusion experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940011778','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940011778"><span id="translatedtitle">Gas-grain energy transfer in solar nebula shock waves: Implications for the origin of <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hood, L. L.; Horanyi, M.</p> <p>1993-01-01</p> <p>Meteoritic <span class="hlt">chondrules</span> provide evidence for the occurrence of rapid transient heating events in the protoplanetary nebula. Astronomical evidence suggests that gas dynamic shock waves are likely to be excited in protostellar accretion disks by processes such as protosolar mass ejections, nonaxisymmetric structures in an evolving disk, and impact on the nebula surface of infalling 'clumps' of circumstellar gas. Previous detailed calculations of gas-grain energy and momentum transfer have supported the possibility that such shock waves could have melted pre-existing <span class="hlt">chondrule</span>-sized grains. The main requirement for grains to reach melting temperatures in shock waves with plausibly low Mach numbers is that grains existed in dust-rich zones (optical depth greater than 1) where radiative cooling of a given grain can be nearly balanced by radiation from surrounding grains. Localized dust-rich zones also provide a means of explaining the apparent small spatial scale of heating events. For example, the scale size of at least some optically thick dust-rich zones must have been relatively small (less than 10 kilometers) to be consistent with petrologic evidence for accretion of hot material onto cold <span class="hlt">chondrules</span>. The implied number density of mm-sized grains for these zones would be greater than 30 m(exp -3). In this paper, we make several improvements of our earlier calculations to include radiation self-consistently in the shock jump conditions, and we include heating of grains due to radiation from the shocked gas. In addition, we estimate the importance of momentum feedback of dust concentrations onto the shocked gas which would tend to reduce the efficiency of gas dynamic heating of grains in the center of the dust cloud.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC41B0537K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC41B0537K"><span id="translatedtitle">Solar Radiation Management and <span class="hlt">Olivine</span> Dissolution Methods in Climate Engineering</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kone, S.</p> <p>2014-12-01</p> <p>An overview of solar radiation management and <span class="hlt">olivine</span> dissolution methods allows to discuss, comparatively, the benefits and consequences of these two geoengineering techniques. The combination of those two techniques allows to concomitantly act on the two main agents intervening in global warming: solar radiation and carbon dioxide. The earth surface temperature increases due mainly to carbon dioxide (a greenhouse gas) that keeps the solar radiation and causes the global warming. Two complementary methods to mitigate climate change are overviewed: SRM method, which uses injected aerosols, aims to reduce the amount of the inbound solar radiation in atmosphere; and <span class="hlt">olivine</span> dissolution in water, a key chemical reaction envisaged in climate engineering , aiming to reduce the amount of the carbon dioxide in extracting it from atmosphere. The SRM method works on scenarios of solar radiation decrease and the <span class="hlt">olivine</span> dissolution method works as a carbon dioxide sequestration method. <span class="hlt">Olivine</span> dissolution in water impacts negatively on the pH of rivers but positively in counteracting ocean acidification and in transporting the silica in ocean, which has benefits for diatom shell formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EP%26S...65.1139M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EP%26S...65.1139M"><span id="translatedtitle">Far-infrared continuum absorption of <span class="hlt">olivine</span> at low temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mutschke, H.; Zeidler, S.; Chihara, H.</p> <p>2013-10-01</p> <p>The far-infrared continuum opacity of cold dust is an important quantity for the study of debris disks in planetary systems and of protoplanetary disks. <span class="hlt">Olivine</span> is considered the most abundant crystalline dust species in such environments. We present spectroscopic absorption measurements on <span class="hlt">olivine</span> plates of the order of a millimeter thickness at wavelengths between 60 and 400 μ m for temperatures down to 10 K. Our data reveal a strong temperature dependence of the continuum absorption coefficient, i.e. more than an order of magnitude decrease at 100 μ m for 10 K compared to room temperature. The absolute values are generally much lower than those measured with <span class="hlt">olivine</span> powders embedded into polyethylene pellets, even if the difference between plate and powder samples is taken into account by theoretical models. In contrast to this, the room temperature data are in relatively good agreement with simulations using optical constants determined from reflection measurements. At low temperatures, the absorption coefficient of <span class="hlt">olivine</span> was measurable with sufficient accuracy only up to 90 μ m for 10 K and up to 110 μ m for 100 K. These data reveal a drastic change in the spectral slope (from β ~ 2.0 to β > 5.0) for the continuum underlying the 69-μ m band, which is not predicted by the low-temperature optical constants determined for forsterite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030110932&hterms=alian&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dalian','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030110932&hterms=alian&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dalian"><span id="translatedtitle">A Study of <span class="hlt">Olivine</span> Alteration to Iddingsite Using Raman Spectroscopy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuebler, K. E.; Wang, Alian; Haskin, L. A.; Jolliff, B. L.</p> <p>2003-01-01</p> <p>A crucial task of Mars surface science is to determine past environmental conditions, especially aqueous environments and their nature. Identification of mineral alteration by water is one way to do this. Recent work interprets TES spectra as indicating altered basalt on Mars. <span class="hlt">Olivine</span>, a primary basaltic mineral, is easily altered by aqueous solutions. Alteration assemblages of <span class="hlt">olivine</span> may be specific to deuteric, hydrothermal, surface water, or metamorphic environments. Raman spectra are produced by molecular vibrations and provide direct means for studying and identifying alteration products. Here, we present a combined study of changes in the chemical composition and Raman spectra of an <span class="hlt">olivine</span> as it alters to iddingsite. Iddingsite is found in some SNC meteorites and is presumably present on Mars. The term 'iddingsite' has been used as a catch-all term to describe reddish alteration products of <span class="hlt">olivine</span>, although some authors ascribe a narrower definition: an angstrom-scale intergrowth of goethite and smectite (presumably saponite) formed in an oxidizing and fluid-rich environment. Alteration conserves Fe (albeit oxidized) but requires addition of Al and H2O and removal of Mg and Si. The smectite that forms may be removed by continued alteration. Dehydration of the goethite forms hematite. Our purpose is to study the mineral assemblage, determine the structural and chemical variability of the components with respect to the degree of alteration, and to find spectral indicators of alteration that will be useful during in-situ analyses on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996M%26PS...31..807P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996M%26PS...31..807P"><span id="translatedtitle">The search for exsolved ferromagnesian <span class="hlt">olivines</span>: A meteoritic survey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petaev, Michail I.</p> <p>1996-11-01</p> <p><span class="hlt">Olivine</span> grains from selected meteorites (the Springwater pallasite, the Lowicz mesosiderite, the ALH 84025 brachinite, the Krymka LL3 chondrite, and the Calcalong Creek lunar meteorite) and terrestrial rocks (San Carlos forsterite and Rockport fayalite) were studied by optical microscopy and high-precision electron microprobe analysis. Detailed microprobe traverses revealed regular igneous zoning in the Krymka and Calcalong Creek <span class="hlt">olivines</span>. Traverses across the San Carlos forsterite grain are flat and display no chemical variations larger than the 2? range of counting error (0.2 mol% Fa). Traverses across <span class="hlt">olivine</span> grains in the ALH 84025, Lowicz, and Springwater meteorites show regular patterns of periodic or wavy chemical variations well exceeding the 2? uncertainty range. However, no lamellar structure was seen in backscattered electron images. It is suggested that the periodic chemical variations may be due to spinodal decomposition of primary, more or less homogeneous grains. I conclude that the absence of earlier reports of such variations simply means that <span class="hlt">olivine</span> grains in equilibrated meteorites have not been examined closely enough to detect them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P43A1904T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P43A1904T"><span id="translatedtitle">Near-Infrared Optical Constants of <span class="hlt">Olivine</span> and Pyroxene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trang, D.; Lucey, P. G.; Gillis-Davis, J.; Cahill, J. T.; Klima, R. L.; Isaacson, P.</p> <p>2012-12-01</p> <p>Producing mineral maps of planetary bodies is useful for petrological studies, future colonization, and resources. Estimating the physical and chemical properties of a surface, however, is complicated due to parameters such as, grain size and shape, mineral chemistry, space weathering, and ambient temperature. Radiative transfer modeling is one method to calculate mineral proportions and chemistry from reflectance spectra. However, radiative transfer modeling requires knowledge of the optical constants of minerals of interest. In this study, we characterized the near-infrared optical constants of two common mafic minerals, <span class="hlt">olivine</span> and pyroxene, with a wide distribution of chemistries. Particularly, we parameterized the imaginary index of refraction, k, in the near-infrared portion of the spectrum of natural <span class="hlt">olivines</span> as a function of foresterite content and synthetic pyroxenes as a function of wollastonite and ferrosilite content. For each k-spectrum, we modeled each absorption features and continuum using the Modified Gaussian Model (MGM) with three Gaussians and an inverse linear function respectively. We find that our fitting routine characterizes the k-spectra of <span class="hlt">olivine</span> and pyroxene consistently. Additionally, we described each parameter of MGM and the continuum with a regression or multiple regressions as a function of mineral chemistry. Thus providing the optical parameters of <span class="hlt">olivine</span> and pyroxene needed for radiative transfer modeling. Scatter observed between optical parameters and mineral chemistry could be the result of minor cations (e.g., Mn2+), grain size, and cation ordering. Future work will seek to characterize these effects on derived optical parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16..573Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16..573Z"><span id="translatedtitle">The effect of mineral paragenesis on Al diffusion in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhukova, Irina; O'Neill, Hugh; Capbell, Ian</p> <p>2014-05-01</p> <p>Al is the most abundant trivalent impurity of <span class="hlt">olivine</span> and is particularly important because its concentration in <span class="hlt">olivine</span> is temperature dependant, and it therefore has potential as a geothermometer (Wan, et al. 2008). Furthermore recent studies show that the incorporation of water into the <span class="hlt">olivine</span> lattice is affected by the presents of trivalent cations such as Al3+ (Berry, et al. 2007; Hauri, et al. 2006). The Al distribution in <span class="hlt">olivines</span> from volcanic rocks is often zoned and mantle <span class="hlt">olivines</span> may also show an inhomogeneous distribution of Al, whereas the majority of other trace elements homogenized by diffusion (Mallmann, et al. 2009; McKibbin, et al.). However, there are no quantitative experimental data for Al diffusion in <span class="hlt">olivine</span>, probably because the combination of low concentration rate and low diffusion rate make measurement difficult. We investigated the effect of silica activity on the diffusion rate of Al in forsterite at varying temperatures using solid-state buffer assemblages. Our study aimed to quantify the effect of major cation activities on the diffusion and concentration of Al in forsterite and also provide insights into the mechanism of Al substitution into the <span class="hlt">olivine</span> lattice. The activities of SiO2, MgO and Al2O3 were buffered in each experiment by four different mineral associations: forsterite + periclase + spinel (fo+per+sp); forsterite + spinel + sapphirine (fo+sp+spr); forsterite + sapphirine + cordierite (fo+spr+cor); forsterite + cordierite + enstatite (fo+cor+en). Iron oxide in proportion of FeO/(FeO+MgO) = 0.1 was added to mixtures for San Carlos <span class="hlt">olivine</span> experiments. Diffusion experiments were performed at the one-atmosphere vertical tube furnaces modified to control the fO2 by CO-CO2 gas mixing or in a box furnace in air for 10 - 28 days at temperatures from 1100 to 1500oC and logfO2 -0.7 and -5.7. The experiment with the San Carlos <span class="hlt">olivine</span> was performed at 1300oC and at logfO2 = -5.7. In order to obtain equilibrium concentrations of the point defects we performed some experiments with pre-annealing. Diffusion profiles were measured by LA-ICP-MS in a traverse mode. The Al content of forsterite decreases with temperature dependence, increasing the potential of Al in <span class="hlt">olivine</span> as a geothermometer. We obtain the activation energy of 379 kJ/mol for the high aSiO2 experiments, which is close within error of the value of 364 kJ/mol for the low aSiO2 experiments implying a common diffusion mechanism. The pre-exponential factor, however, increases by 5 orders of magnitude from low aSiO2 (fo+per+sp buffer) to high aSiO2 (fo+cor+en buffer). The much higher diffusivity at high aSiO2 indicates that Al diffusion occurs through octahedral cation site vacancies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2996662','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2996662"><span id="translatedtitle">Geoengineering potential of artificially enhanced silicate weathering of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Köhler, Peter; Hartmann, Jens; Wolf-Gladrow, Dieter A.</p> <p>2010-01-01</p> <p>Geoengineering is a proposed action to manipulate Earth’s climate in order to counteract global warming from anthropogenic greenhouse gas emissions. We investigate the potential of a specific geoengineering technique, carbon sequestration by artificially enhanced silicate weathering via the dissolution of <span class="hlt">olivine</span>. This approach would not only operate against rising temperatures but would also oppose ocean acidification, because it influences the global climate via the carbon cycle. If important details of the marine chemistry are taken into consideration, a new mass ratio of CO2 sequestration per <span class="hlt">olivine</span> dissolution of about 1 is achieved, 20% smaller than previously assumed. We calculate that this approach has the potential to sequestrate up to 1 Pg of C per year directly, if <span class="hlt">olivine</span> is distributed as fine powder over land areas of the humid tropics, but this rate is limited by the saturation concentration of silicic acid. In our calculations for the Amazon and Congo river catchments, a maximum annual dissolution of 1.8 and 0.4 Pg of <span class="hlt">olivine</span> seems possible, corresponding to the sequestration of 0.5 and 0.1 Pg of C per year, but these upper limit sequestration rates come at the environmental cost of pH values in the rivers rising to 8.2. Open water dissolution of fine-grained <span class="hlt">olivine</span> and an enhancement of the biological pump by the rising riverine input of silicic acid might increase our estimate of the carbon sequestration, but additional research is needed here. We finally calculate with a carbon cycle model the consequences of sequestration rates of 1–5 Pg of C per year for the 21st century by this technique. PMID:21059941</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015E%26PSL.425..168H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015E%26PSL.425..168H"><span id="translatedtitle">Diffusive over-hydration of <span class="hlt">olivine</span>-hosted melt inclusions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartley, Margaret E.; Neave, David A.; Maclennan, John; Edmonds, Marie; Thordarson, Thor</p> <p>2015-09-01</p> <p>The pre-eruptive water content of magma is often estimated using crystal-hosted melt inclusions. However, <span class="hlt">olivine</span>-hosted melt inclusions are prone to post-entrapment modification by H+ diffusion as they re-equilibrate with their external environment. This effect is well established for the case of H+ loss from <span class="hlt">olivine</span>-hosted inclusions that have cooled slowly in degassed magma. Here we present evidence for the opposite effect: the addition of H+ into inclusions that are held in melts that are enriched in H2O with respect to the trapped melts. The compositional variability in a suite of 211 <span class="hlt">olivine</span>-hosted inclusions from the Laki and Skuggafjöll eruptions in Iceland's Eastern Volcanic Zone indicates that diffusive H+ gain governs the H2O content of incompatible trace element depleted inclusions. Individual eruptive units contain <span class="hlt">olivine</span>-hosted inclusions with widely varying incompatible element concentrations but near-constant H2O. Furthermore, over 40% of the inclusions have H2 O /Ce > 380, significantly higher than the H2O/Ce expected in primary Icelandic melts or mid-ocean ridge basalts (150-280). The fact that the highest H2O/Ce ratios are found in the most incompatible element depleted inclusions indicates that hydration is a consequence of the concurrent mixing and crystallisation of compositionally diverse primary melts. Hydration occurs when <span class="hlt">olivines</span> containing depleted inclusions with low H2O contents are juxtaposed against more hydrous melts during mixing. Melt inclusions from a single eruption may preserve evidence of both diffusive H+ loss and H+ gain. Trace element data are therefore vital for determining H2O contents of melt inclusions at the time of inclusion trapping and, ultimately, the H2O content of the mantle source regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V11H..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V11H..01G"><span id="translatedtitle"><span class="hlt">Olivine</span> as a key to unlocking Kilauea's magmatic history</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garcia, M. O.; Norman, M. D.</p> <p>2011-12-01</p> <p><span class="hlt">Olivine</span> is a ubiquitous mineral in Hawaiian basalts. It is on the liquidus at pressures <0.5 GPa and has the potential to record numerous petrologic processes including the histories of parental magma composition changes, crystal fractionation, magma mixing and crustal contamination. These processes are recorded in <span class="hlt">olivine</span> composition (major and trace elements, and isotopes) and by melt inclusions trapped within <span class="hlt">olivine</span>. Here we focus on Kilauea's historical lavas (1820-present) to evaluate the magmatic history one of world's most active volcanoes. Kilauea has shown dramatic variations in it eruptive rate and style (from vigorous, quiescent effusion in 1820 to infrequent explosive activity in 1924 and then to its highest effusion during the last decade). Eruption rates correlate with whole-rock compositional and isotopic variations (P-G 1999). Most Kilauea lavas have normally zoned <span class="hlt">olivine</span> in equilibrium with whole-rock compositions which belies complex magma chamber processes. Parental magma composition changed rapidly based on the heterogeneity of melt inclusion compositions in higher Mg <span class="hlt">olivine</span> (>86 forsterite). Melt inclusions from single eruptions show wider variation in ratios of Ca/Al and Nb/Y than observed in lavas for the historical period. Thus, the mantle source is heterogeneous on a small scale and small batches of compositionally distinct melt are frequently delivered to the volcano. These magma batches undergo mixing, fractionation and after caldera collapses (e.g.1924), crustal contamination in the summit reservoir. This work demonstrates that an Ernstonian approach, using minerals to understand petrologic processes, is key to unlocking Kilauea's magmatic processes. Pietruszka, A.P. and Garcia, M.O., 1999, J. Petrol. 40, 1321-1342.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994Metic..29R.518P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994Metic..29R.518P"><span id="translatedtitle">Exsolution of ferromagnesian <span class="hlt">olivine</span> in the Divnoe meteorite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petaev, M. I.; Brearley, A. J.</p> <p>1994-07-01</p> <p>The Divnoe meteorite is a granoblastic <span class="hlt">olivine</span>-rich primitive achondrite whose textural and mineralogical characteristics suggest extensive recrystallization during slow cooling in the temperature range from approximately 1000 to approximately 500 C and lower. <span class="hlt">Olivine</span> grains in this meteorite show a lamellar appearance in BSE images, caused by minor micrometer-scale chemical variations in Fe, Mg, and Mn contents between adjacent lamellae. Ten grains of lamellar <span class="hlt">olivine</span> were studied in detail by Electron Probe Microanalysis (EPMA) and optical microscopy and two of these by Transmission Electron Microscopy (TEM). The <span class="hlt">olivine</span> grains studied are essentially free of minor elements (Ti, Al, Cr, Ni, Ca, Na) except for Mn, and fall in the compositional range found by an earlier study. While the compositional ranges of Fe-poor and Fe-rich lamellae overlap, the differences between lamellae richest and poorest in Fe are quite similar, suggestive of their formation by an equilibrium process. Fine-scale microprobing has confirmed earlier compositional data, but has reduced lamella thicknesses to a few micrometers, which is in a good agreement with TEM observations. The structural and compositional data obtained strongly suggest that the lamellar structure in these <span class="hlt">olivine</span> grains was produced by an exsolution process, which is in qualitative agreement with a recent thermodynamic analysis of phrase relations in the system Mg2SiO4-FeSiO2. Cracks in Fe-rich lamellae could result from expansion during the exsolution process due to the volume difference between Fe-rich and Fe-poor lamellae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.6986K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.6986K"><span id="translatedtitle">The geoengineering potential of artificially enhanced silicate weathering of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Köhler, Peter; Hartmann, Jens; Wolf-Gladrow, Dieter A.</p> <p>2010-05-01</p> <p>Geoengineering is a proposed action to manipulate Earth's climate in order to counteract global warming from anthropogenic greenhouse gas emissions. We investigate in more detail the potential of a specific geoengineering technique, the carbon sequestration by artificially enhanced silicate weathering via the dissolution of <span class="hlt">olivine</span>. This approach would not only operate against rising temperatures but would also oppose ocean acidification, because it influences the global climate via the carbon cycle. We here show the consequences of this technique for the chemistry of the surface ocean at rates necessary for geoengineering. We calculate that <span class="hlt">olivine</span> dissolution has the potential to sequestrate up to one Pg C yr-1 directly, if <span class="hlt">olivine</span> is distributed as fine powder over land areas of the humid tropics. The carbon sequestration potential is limited by the saturation concentration of silicic acid. In our calculations for the Amazon and Congo river catchments a maximum annual dissolution of 1.8 and 0.4 Pg of <span class="hlt">olivine</span> seems possible, corresponding to the sequestration of 0.5 and 0.1 Pg C yr-1. Open water dissolution of fine grained <span class="hlt">olivine</span> and an enhancement of the biological pump by the rising riverine input of silicic acid might increase our estimate of the carbon sequestration, but additional research is needed here. We finally calculate with a carbon cycle model the consequences of sequestration rates of 1 to 5 Pg C yr-1 for the 21st century by this technique. At maximum this technique would reduce global warming by 1 K and counteract ocean acidification by a rise in surface ocean pH by 0.1 in the year 2100.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015313','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015313"><span id="translatedtitle">Evidence for equilibrium conditions during the partitioning of nickel between <span class="hlt">olivine</span> and komatiite liquids.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Budahn, J.R.</p> <p>1986-01-01</p> <p><span class="hlt">Olivine</span>-liquid partition coefficients for Ni(DNi), calculated from Ni vs MgO abundance variations in komatiite series basalts, compare favourably with experimentally determined values, if Ni variations in <span class="hlt">olivine</span>-controlled basalts can be modelled with an equation that assumes equilibrium between the entire <span class="hlt">olivine</span> crystal and its coexisting liquid.-J.A.Z.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMMR33B1858P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMMR33B1858P"><span id="translatedtitle">Experimental Deformation of <span class="hlt">Olivine</span> Single Crystal at Mantle P and T: Pressure Effect on <span class="hlt">Olivine</span> Dislocation Slip-System Activities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paul, R.; Girard, J.; Chen, J.; Amiguet, E.</p> <p>2008-12-01</p> <p>Seismic velocity anisotropies observed in the upper mantle are interpreted from lattice preferred orientations (LPO) produced experimentally in <span class="hlt">olivine</span>, which depends on the dominant dislocation slip systems. At low pressure P<3 GPa, mantle temperature (T) and in dry conditions, <span class="hlt">olivine</span> [100] dislocation slip dominates the less active [001] slip. This tends to align crystal fast velocity [100] axis with the principal shear direction. Yet recent high-pressure deformation experiments (Couvy et al., 2004, EJM, 16, 877; Raterron et al., 2007, Am. Min., 92, 1436; Raterron et al., 2008, Phys. Earth Planet. Int., doi:10.1016/j.pepi.2008.07.026) show that [001](010) slip system dominates [100](010) system in the (P,T) range of the deep upper mantle. This may promote a shear-parallel slow-velocity [001] axis and may explain the seismic-velocity attenuation observed at depth >200 km (Mainprice et al., 2005, Nature, 433, 731). In order to further constrain the effect of P on <span class="hlt">olivine</span> slip system activities, which is classically quantified by the activation volume V* in power creep laws, deformation experiments were carried out in poor water condition, at P>5 GPa and T=1400°C, on pure forsterite (Fo100) and San Carlos <span class="hlt">olivine</span> crystals, using the Deformation-DIA apparatus at the X17B2 beamline of the NSLS (Upton, NY). Ten crystals were oriented in order to active either [100] slip alone or [001] slip alone in (010) plane, or both [100](001) and [001](100) systems together. Constant applied stress σ <300 MPa and specimen strain rates were monitored in situ using time-resolved x-ray diffraction and radiography, respectively, for a total of 27 investigated steady state conditions. The obtained rheological data were compared with data previously obtained in comparable T and σ conditions, but at room P, by Darot and Gueguen (1981, JGR, 86, 6219) for Fo100 and by Bai et al. (1991, JGR, 96, 2441) for San Carlos <span class="hlt">olivine</span>. This new set of data confirms previous deformation data obtained at high pressure, i.e., it translates into a high activation volume V*>14 cm3/mol for [100](010) and a low V*<9 cm3/mol for [001](010)in both Fo100 and Fe-bearing <span class="hlt">olivine</span>. We also show that the combined activity of [100](001) and [001](100) systems translates into V*=12± 3 cm3/mol, suggesting that pressure also reduces both system activities. All together, our data show that <span class="hlt">olivine</span> [001](010) system dominates deformation at the mantle P and T.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeCoA..98....1T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeCoA..98....1T"><span id="translatedtitle">Fine-grained rims surrounding <span class="hlt">chondrules</span> in the Tagish Lake carbonaceous chondrite: Verification of their formation through parent-body processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takayama, Akiko; Tomeoka, Kazushige</p> <p>2012-12-01</p> <p>A petrographic and electron microscopic study of the carbonate-poor lithology of the Tagish Lake carbonaceous chondrite reveals that most <span class="hlt">chondrules</span> contain many pseudomorphs of opaque nodules and are surrounded by phyllosilicate-rich altered zones that were formed by replacing enstatite and opaque nodules along the <span class="hlt">chondrule</span> peripheries. Most <span class="hlt">chondrules</span> and other coarse-grained components are surrounded by fine-grained rims, which are commonly disaggregated and partly lacking. The altered zones and the rims are compositionally and texturally similar, although they exhibit some differences in secondary minerals. In comparison, the rims and the host matrix show more significant differences in bulk chemical composition, texture, and mineralogy. The observations suggest that the <span class="hlt">chondrules</span> and the rims experienced aqueous alteration simultaneously, whereas the rims and the matrix experienced aqueous alteration under distinct conditions. We also found a clast that contains multiple coarse-grained components embedded in a matrix and numerous smaller matrix clasts. The coarse-grained components in the clast have no rims, and the matrices of the clasts are mineralogically identical to the rims. The results suggest that the <span class="hlt">chondrules</span>, other coarse-grained components, and their rims (generically referred to as <span class="hlt">chondrules</span>/rims) and the clasts originated from a common precursor region in the meteorite parent-body that was different from the location where the host meteorite was finally lithified. That is, the <span class="hlt">chondrules</span>/rims are actually clasts produced by brecciation and later transported and incorporated into the present host matrix. The rims are, therefore, remnants of matrix material that formerly filled interspaces between the <span class="hlt">chondrules</span> and other coarse-grained components. This model is essentially consistent with those previously proposed for the carbonate-rich lithology of Tagish Lake and the hydrated <span class="hlt">chondrules</span>/rims in the Vigarano and Mokoia CV3 chondrites.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.434..117L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.434..117L"><span id="translatedtitle">Ancient stardust in fine-grained <span class="hlt">chondrule</span> dust rims from carbonaceous chondrites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leitner, Jan; Vollmer, Christian; Floss, Christine; Zipfel, Jutta; Hoppe, Peter</p> <p>2016-01-01</p> <p>Carbonaceous chondrites are fragments from primitive parent asteroids, which represent some of the most primitive meteorites accessible for laboratory analysis and offer therefore the best opportunity to explore the chemical and physical conditions in the early Solar System. Here, we report the identification of presolar grains, which are circumstellar condensates that date back from before the formation of our Solar System, in fine-grained dust rims around <span class="hlt">chondrules</span> in carbonaceous chondrites. Average presolar grain abundances in the rims of aqueously altered chondrites (petrologic type 2) are three times higher than in the respective interchondrule matrices, while for the most pristine specimens (petrologic type 3), the opposite is observed. The presence of these grains implies a nebular origin of the rim material, and gives evidence for differing alteration pathways for different reservoirs of fine-grained material found in primitive meteorites. Moreover, our findings indicate formation of the fine-grained rims in the solar nebula prior to parent-body accretion, giving support to accretionary scenarios for parent-bodies in the presence of dust-rimmed <span class="hlt">chondrules</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030018906','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030018906"><span id="translatedtitle">Blowing in the Wind: I. Velocities of <span class="hlt">Chondrule</span>-sized Particles in a Turbulent Protoplanetary Nebula</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cuzzi, Jeffrey N.; Hogan, Robert C.; Fonda, Mark (Technical Monitor)</p> <p>2003-01-01</p> <p>Small but macroscopic particles - <span class="hlt">chondrules</span>, higher temperature mineral inclusions, metal grains, and their like - dominate the fabric of primitive meteorites. The properties of these constituents, and their relationship to the fine dust grains which surround them, suggest that they led an extended existence in a gaseous protoplanetary nebula prior to their incorporation into their parent primitive bodies. In this paper we explore in some detail the velocities acquired by such particles in a turbulent nebula. We treat velocities in inertial space (relevant to diffusion), velocities relative to the gas and entrained microscopic dust (relevant to accretion of dust rims), and velocities relative to each other (relevant to collisions). We extend previous work by presenting explicit, closed-form solutions for the magnitude and size dependence of these velocities in this important particle size regime, and compare these expressions with new numerical calculations. The magnitude and size dependence of these velocities have immediate applications to <span class="hlt">chondrule</span> and CAI rimming by fine dust, and to their diffusion in the nebula, which we explore separately.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=furniture&pg=4&id=EJ877409','ERIC'); return false;" href="http://eric.ed.gov/?q=furniture&pg=4&id=EJ877409"><span id="translatedtitle">Toll <span class="hlt">Bar</span> on Sea</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hunter, Dave</p> <p>2008-01-01</p> <p>In the summer of 2007 the United Kingdom experienced some of the heaviest rainfall since records began. Toll <span class="hlt">Bar</span> in South Yorkshire featured prominently in media coverage as the village and the homes surrounding it began to flood. Many people lost everything: their homes, their furniture, their possessions. In an effort to come to terms with what</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6230565','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6230565"><span id="translatedtitle"><span class="hlt">BARS</span>/SSC/SPHINX</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Herrmann, W. )</p> <p>1993-06-06</p> <p><span class="hlt">BARS</span> is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shoch compression of condensed media, high rate deformation of solids, and detonation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6958270','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6958270"><span id="translatedtitle"><span class="hlt">BARS</span>/SSC/SPHINX</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Herrmann, W. )</p> <p>1993-06-06</p> <p><span class="hlt">BARS</span> is a program which allows retrieval of information from suitable bibliographic databases. Two databases are included, SSC and SPHINX, which together list bibliographic information for some 12,000 references related to the fields of shock compression of condensed media, high rate deformation of solids, and detonation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999SPIE.3876..267W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999SPIE.3876..267W"><span id="translatedtitle">Polysilicon xylophone <span class="hlt">bar</span> magnetometers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wickenden, Dennis K.; Champion, John L.; Givens, Robert B.; Kistenmacher, Thomas J.; Lamb, James L., III; Osiander, Robert</p> <p>1999-08-01</p> <p>The recently developed JHU/APL magnetometer, which is based on a free-free (xylophone) resonating <span class="hlt">bar</span>, is simple, small, light weight, has a low power consumption and utilizes the Lorentz force to measure vector magnetic fields. The device is intrinsically linear and has a wide dynamic range such that it can measure magnetic field strengths from nanoteslas to teslas. Furthermore, its sensitivity is independent of size for resonating <span class="hlt">bars</span> of the same material and aspect ratio. This makes it ideally suited for miniaturization using MEMS techniques. Various polysilicon xylophone <span class="hlt">bars</span> have been designed, processed, and characterized. The output response has verified the size-independent scaling law and sensitivities of the order of 100 nanoTesla have been achieved with drive currents as low as 20 microamps. This drive current is limited by the sheet resistance of the polysilicon support electrodes and directly affects the sensitivity. The electrodes also have a dramatic effect on the resonant frequency since they act as torsional stiffening members on the resonating <span class="hlt">bar</span>. For example, for a 500 X 50 micron xylophone the resonant frequency varies from the designed 69 kHz to over 95 kHz for 10 micron wide support electrodes. The electrodes do not affect the mechanical Q-factors observed and values in excess of 20,000 at reduced pressures have been routinely obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Flood&pg=4&id=EJ877409','ERIC'); return false;" href="http://eric.ed.gov/?q=Flood&pg=4&id=EJ877409"><span id="translatedtitle">Toll <span class="hlt">Bar</span> on Sea</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hunter, Dave</p> <p>2008-01-01</p> <p>In the summer of 2007 the United Kingdom experienced some of the heaviest rainfall since records began. Toll <span class="hlt">Bar</span> in South Yorkshire featured prominently in media coverage as the village and the homes surrounding it began to flood. Many people lost everything: their homes, their furniture, their possessions. In an effort to come to terms with what…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015HiA....16..327S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015HiA....16..327S"><span id="translatedtitle">Multiple <span class="hlt">bars</span> and secular evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Juntai</p> <p>2015-03-01</p> <p><span class="hlt">Bars</span> are the most important driver of secular evolution. A significant fraction of <span class="hlt">barred</span> galaxies also harbor small secondary <span class="hlt">bars</span>. Secondary <span class="hlt">bars</span> are visible even in near-infrared images, so they are not just dusty and blue, but stellar features (Erwin & Sparke 2002). Since they are quite common, secondary <span class="hlt">bars</span> are probably long-lived stellar features. The random relative orientation of the two <span class="hlt">bars</span> indicates that they are dynamically decoupled with different pattern speeds (Buta & Crocker 1993). Corsini et al. (2003) presented conclusive direct kinematic evidence for a decoupled secondary <span class="hlt">bar</span> in NGC 2950. Dynamically decoupled secondary <span class="hlt">bars</span> have long been hypothesized to be a mechanism to drive gas past the ILR of primary <span class="hlt">bars</span> to feed active galactic nuclei (Shlosman et al. 1989). However, the dynamics of secondary <span class="hlt">bars</span> are still not well understood, and it is still unclear what role secondary <span class="hlt">bars</span> play in the AGN fueling process. Numerical simulations offer the best approach to understanding double-<span class="hlt">barred</span> systems. Decoupled secondary <span class="hlt">bar</span> in the earlier gaseous simulations only last a short time (< 1 Gyr, e.g. Friedli & Martinet 1993). Orbital studies of double-<span class="hlt">barred</span> systems discovered a family of loop orbits that may be building blocks of long-lived nuclear stellar <span class="hlt">bars</span> (Maciejewski & Sparke 1997, 2000). To complement orbital studies, which are not fully self-consistent, N-body simulations are preferred to further our understanding of double-<span class="hlt">barred</span> systems. Debattista & Shen (2007) and Shen & Debattista (2009) managed to form long-lived double-<span class="hlt">barred</span> systems with purely collisionless simulations, where a pre-existing rotating pseudo-bulge is introduced initially. The shape and size of secondary <span class="hlt">bars</span> in the models are comparable to observed ones. They found that the rotation of the two <span class="hlt">bars</span> is not rigid. The amplitude and pattern speed of the secondary <span class="hlt">bars</span> oscillate as they rotate through their primary counterparts. Although the secondary <span class="hlt">bar</span> rotates faster than the primary <span class="hlt">bar</span> in this model, the stellar velocity field in the central region only shows a weakly twisted kinematic minor axis. Recently more simulations of double-<span class="hlt">barred</span> galaxies with simpler initial conditions are explored (Du, Shen & Debattista 2014). We expect that the new models can be used to cross-check with the kinematic properties of double-<span class="hlt">barred</span> galaxies from IFU observations such as SAURON and Atlas3D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V41C2509S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V41C2509S"><span id="translatedtitle">Lattice preferred orientations of <span class="hlt">olivine</span> in the schistosed antigorite serpentinite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soda, Y.; Ando, J.; Mizukami, T.; Morishita, T.</p> <p>2011-12-01</p> <p>The lattice preferred orientation (LPO) of the schistosed antigorite serpentinite is considered as causes of the seismic anisotropy observed at the subduction zones (Katayama et al., 2009; Jung, 2011) and the natural examples are reported by several researchers (Bezacier et al., 2010; Hirauchi et al., 2010; Soda and Takagi, 2010). Formation process of the antigorite LPO is unclear, especially at primary serpentinized stage. To understand the development of micro-structures of antigorite serpentinite, we made structural analyses of serpentinite schist and the former peridotite fabric. Samples were taken from lenticular serpentinite bodies (< 1km) stack in Jurassic accretionary complex, Toba area, Southwest Japan. The serpentinite consist of <span class="hlt">olivine</span>, antigorite, meta-clinopyroxene and Cr-spinel. The foliation and lineation of serpentinite is defined by parallel alignment of elongated <span class="hlt">olivine</span> grain and antigorite blades, which make up mylonitic textures, such as a porphyroclast system and composite planar fabric. Antigorite blades show syn-kinematic growth in pressure shadows and pull-apart of <span class="hlt">olivine</span> porphyroclast. In the less serpentinized part, antigorite blades are crystallized along the grain boundary of <span class="hlt">olivine</span>. We measure the LPOs of coarse <span class="hlt">olivine</span> grains in the serpentinite schist using a u-stage. The X, Y and Z directions represent directions of lineation, normal to lineation within the foliation and normal to foliation, respectively. The LPOs of <span class="hlt">olivine</span> show point maximum or partial girdle distribution, and these concentrated crystal axes are incongruous with X, Y and Z direction. The a[100] axes of <span class="hlt">olivine</span> are parallel to the serpentinite foliation, and form a point maximum several degrees away from the Y direction. The b[010] axes and the c[001] axes are concentrated Z and X direction forming a partial girdle normal to Y direction, respectively. Boudier et al. (2010) have reported the topotactic relationship between <span class="hlt">olivine</span> and antigorite. They show that the (100)ol is parallel to the (001)atg or the (010)ol is parallel to the (001)atg. And, the a[100] axes of <span class="hlt">olivine</span> are normal to serpentinite foliation with point maximum in the thin section scale. However, in the case of this study, the simple topotactic relationship does not connect the fabric in the thin section scale of serpentinite schist. Although, more detail analysis need to discuss the formation of antigorite LPO, the other mechanisms, such as crystal plastic deformation or diffusion-precipitation, might cause rearrangement of antigorite fabric. References Bezacier, L. et al., 2010, Earth and Planetary Science Letters, 289, 198-208. Boudier, F. et al., 2010, Journal of Petrology 51, 495-512. Hirauchi et al., 2010, Earth and Planetary Science Letters, 299, 196-206. Jung, H., 2011, Earth and Planetary Science Letters, 307, 535-543. Katayama, I., et al., 2009, Nature, 461, 1114-1118. Soda, Y. and Takagi, H., 2010, Journal of Structural Geology, 32, 792-802.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5250C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5250C"><span id="translatedtitle">A <span class="hlt">Chondrule</span> from the Mokoia (CV3) Chondrite with Anomalously Low 26Mg*: Evidence for a Multi-Stage History-</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Claydon, J. L.; Elliott, T.; Coath, C. D.; Chen, H. W.; Taylor, C. A.; Russell, S. S.</p> <p>2015-07-01</p> <p>MC-ICP-MS measurements of Mg isotopes in <span class="hlt">chondrule</span> MOK13B reveal that it may have formed from low-Al/Mg material that underwent chemical fractionation to increase Al/Mg after decay of 26-Al, or it may sample a region with anomalous Al or Mg isotopes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000085861','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000085861"><span id="translatedtitle">On the Lower Limit of <span class="hlt">Chondrule</span> Cooling Rates: The Significance of Iron Loss in Dynamic Crystallization Experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paque, Julie M.; Connolly, Harold C., Jr.; Lofgren, Gary E.</p> <p>1999-01-01</p> <p>Lofgren (1989) and the further analysis of Lofgren's 1989 experiments by Jones and Lofgren (1993) established that cooling rates as slow as 5 C/hour produced analog textures and major and minor element zoning profiles in minerals, implying that a lower limit on <span class="hlt">chondrule</span> cooling rate may be approximately 5 C/hour These results, however, are in conflict with those reported by Radomsky and Hewins (1990). In their paper, Radomsky and Hewins (1990) established a lower limit on <span class="hlt">chondrule</span> cooling rates of I 100 C/hour a factor of 20 higher than that suggested by Jones and Lofgren (1993). The higher cooling rates suggested by Radomsky and Hewins (1990) have gained considerable favor within the meteoritic community largely because it appears more consistent with the preservation of Na in <span class="hlt">chondrules</span>, which tends to volatilize at the slower cooling rates. In their study, however, Radomsky and Hewins (1990) did not use Pt hang wires that were coated or saturated with Fe. The lack of such techniques likely facilitated Fe loss from their experimental <span class="hlt">chondrules</span> to the hang wire during formation (Jones and Lofgren, 1993). The effect of Fe loss could produce an inaccurate determination of cooling rates since these rates are largely determined by the Mg-Fe distributions in individual crystals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5082B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5082B"><span id="translatedtitle">Overgrowth Layers on Pyroxene in an FeO-Rich Porphyritic <span class="hlt">Chondrule</span> in CO3.0 Y-81020</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baecker, B.; Rubin, A. E.; Wasson, J. T.</p> <p>2015-07-01</p> <p>A POP <span class="hlt">chondrule</span> in CO3.0 Y-81020 contains pyroxene phenocrysts with BSE-dark to BSE-bright overgrowth layers. FeO and CaO gradually increase from the center to the edge of the grains, but exhibit "sawtooth" compositional zoning patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150001936','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150001936"><span id="translatedtitle">Early Size Distributions of <span class="hlt">Chondrule</span> Subgroups Overprinted by the Final Accumulation Process of Particle Components in Allende</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>McCain, K. A.; Simon, J. I.; Cuzzi, J. N</p> <p>2015-01-01</p> <p>Populations of compositionally distinct particles are fundamental components of undifferentiated chondritic meteorites. Many theories explain the formation of chondrites, one class of which includes mechanisms for sorting the component particles in the solar nebula prior to their accretion. Mechanisms include sorting by mass, turbulent concentration, X-winds, and photophoresis, which will produce characteristic distributions of observable properties such as particle size. Distinguishing processes that occur in specific astrophysical environments requires characterization of particle types, which include refractory Ca-Al-rich Inclusions (CAIs) and less-refractory <span class="hlt">chondrules</span>. Previous investigations of modal abundances of CAIs and <span class="hlt">chondrules</span> exist, but differences within and between these two groups, both of which are made up of diverse subgroups with different thermal histories and chemical compositions, remain mostly unstudied. The presence of rims, a significant event occurring after the formation of at least some <span class="hlt">chondrules</span>, have also yet to be considered with respect to sorting. Here we present the sizes of CAIs and <span class="hlt">chondrules</span> in Allende with attention to the smallest sizes, subgroups, and particle rims.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50.1197B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50.1197B"><span id="translatedtitle">Pb-Pb dating of individual <span class="hlt">chondrules</span> from the CBa chondrite Gujba: Assessment of the impact plume formation model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bollard, Jean; Connelly, James N.; Bizzarro, Martin</p> <p>2015-07-01</p> <p>The CB chondrites are metal-rich meteorites with characteristics that sharply distinguish them from other chondrite groups. Their unusual chemical and petrologic features and a young formation age of bulk <span class="hlt">chondrules</span> dated from the CBa chondrite Gujba are interpreted to reflect a single-stage impact origin. Here, we report high-precision internal isochrons for four individual <span class="hlt">chondrules</span> of the Gujba chondrite to probe the formation history of CB chondrites and evaluate the concordancy of relevant short-lived radionuclide chronometers. All four <span class="hlt">chondrules</span> define a brief formation interval with a weighted mean age of 4562.49 ± 0.21 Myr, consistent with its origin from the vapor-melt impact plume generated by colliding planetesimals. Formation in a debris disk mostly devoid of nebular gas and dust sets an upper limit for the solar protoplanetary disk lifetime at 4.8 ± 0.3 Myr. Finally, given the well-behaved Pb-Pb systematics of all four <span class="hlt">chondrules</span>, a precise formation age and the concordancy of the Mn-Cr, Hf-W, and I-Xe short-lived radionuclide relative chronometers, we propose that Gujba may serve as a suitable time anchor for these systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5360K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5360K"><span id="translatedtitle">Why Do U-Pb Ages of <span class="hlt">Chondrules</span> and CAIs Have More Spread than Their 26Al Ages?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kita, N. T.; Tenner, T. J.; Ushikubo, T.; Bouvier, A.; Wadhwa, M.; Bullock, E. S.; MacPherson, G. J.</p> <p>2015-07-01</p> <p>To test 26Al homogeneity in the early solar system, we compare relative 26Al ages of <span class="hlt">chondrules</span> and CAIs with their absolute U-Pb ages. We will summarize the relevant data and discuss possible causes of discrepancies between the two chronometers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050176447','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050176447"><span id="translatedtitle"><span class="hlt">Olivine</span> and Carbonate Globules in ALH84001: A Terrestrial Analog, and Implications for Water on Mars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Treiman, A. H.</p> <p>2005-01-01</p> <p>Carbonate globules in ALH84001 are associated with small <span class="hlt">olivine</span> grains an unexpected finding because the <span class="hlt">olivines</span> equilibrated at high T while the carbonate is chemically zoned and unequilibrated. A possible explanation comes from a terrestrial analog on Spitsbergen (Norway), where some carbonate globules grew in cavities left by aqueous dissolution of <span class="hlt">olivine</span>. For ALH84001, the same process may have acted, with larger <span class="hlt">olivines</span> dissolved out and smaller ones shielded inside orthopyroxene. Carbonate would have been deposited in holes where the <span class="hlt">olivine</span> had been. Later shocks crushed remaining void space, and mobilized feldspathic glass around the carbonates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19890023485&hterms=Breccia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DBreccia','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19890023485&hterms=Breccia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DBreccia"><span id="translatedtitle"><span class="hlt">Olivine</span> vitrophyres - A nonpristine high-Mg component in lunar breccia 14321</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shervais, John W.; Taylor, Lawrence A.; Lindstrom, Marilyn M.</p> <p>1988-01-01</p> <p>The presence of <span class="hlt">olivine</span> vitrophyres in breccia 14321 is discussed, suggesting that <span class="hlt">olivine</span> vitrophyres could account for the high-Mg component of soils and breccias in the lunar highlands. The <span class="hlt">olivine</span> vitrophyre clasts from 14321 have high bulk MgO and the Mg/(Mg+Fe) ratio is 78 percent. The <span class="hlt">olivine</span> vitrophyres are impact melt rocks and are rich in KREEP. The high MgO concentration is manifest by skeletal quench crystals of <span class="hlt">olivine</span> that constitute about 30 percent of the mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMDI24A..01P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMDI24A..01P"><span id="translatedtitle">Evidences and consequences of slow hydrogen diffusion in <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Padron-Navarta, J. A.; Hermann, J.; O'Neill, H. S.</p> <p>2014-12-01</p> <p>In the most abundant upper mantle phase, <span class="hlt">olivine</span>, the presence of hydrogen significantly modifies the timescale of chemical diffusion, plastic deformation, electrical conductivity and the attenuation of seismic waves. Early experiments showed that hydrogen is the fastest species able to diffuse through the <span class="hlt">olivine</span> lattice. We have found, however, experimental and natural evidence suggesting that hydrogen diffusion can also be orders of magnitude slower. In <span class="hlt">olivine</span> there are four different hydrogen substitution mechanisms, associated with Mg vacancies, Si vacancies, trivalent cations and titanium substitution, hereafter referred to as H[Mg], H[Si], H[triv] and H[Ti] respectively. We experimentally investigated the dehydroxylation of synthetic forsterite with two contrasting hydrous defect populations: (1) dominated by H[Si], and H[Ti] with subsidiary H[Mg] and H[triv]; and (2) H[Si] exclusively. The loss rates of H[Mg] and H[triv] are in agreement with previous measurements of bulk hydrogen diffusion in forsterite, but the decrease in H[Ti] and H[Si] are ~1.5 and ~ 3 orders of magnitude slower, respectively. The activation energy and pre-exponential terms derived in these experiments are in agreement with the empirical correlation recently proposed based on the Meyer-Nedel compensation law (Jones 2014, G3, 15, 2616-2631). Natural observations attest further to slow hydrogen diffusivity in <span class="hlt">olivine</span> dominated by H[Ti] and H[Si]. Metamorphic <span class="hlt">olivines</span> formed after dehydration reactions in the Alpine orogeny preserve their original water contents despite long times of exhumation (2-3 Ma). Closure temperature calculations suggest that using previous fast diffusion rates, these <span class="hlt">olivines</span> should reequilibrate down to 400C. Only slow hydrogen diffusion coefficients such as those corresponding to H[Si] are able to explain the observed preservation of water content at the peak metamorphic temperature (700-800C). These findings have implications for estimating the ascent rate of xenoliths, which are more consistent with other independent constrains, as recently noted (Hilchie et al. 2014, Lithos, 202-203, 429-441). They are also required to assess the time necessary to equilibrate experimental charges, since for the different hydrous defects this time would vary by orders of magnitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V52A..08Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V52A..08Z"><span id="translatedtitle">Real Time Pore Structure Evolution during <span class="hlt">Olivine</span> Mineral Carbonation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.</p> <p>2014-12-01</p> <p>Aqueous carbonation of ultramafic rocks has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. While chemical kinetics data indicate that carbonation reaction in <span class="hlt">olivine</span> is one of the fastest among the mg-bearing minerals, in practice, the factors that limit the extent and rate of carbonation in ultramafic rocks are fluid supply and flux. On the one hand, reaction products could produce passivating layer that prohibits further reactions. On the other hand, the increases in solid volume during carbonation could lead to cracking and create new fluid paths. Whether carbonation in ultramafic rocks is self-limiting or self-sustaining has been hotly debated. Experimental evidence of precipitation of reaction products during <span class="hlt">olivine</span> carbonation was reported. To date, reaction-driven cracking has not been observed. In this paper, we present the first real-time pore structure evolution data using the x-ray synchrotron microtomography. Sodium bicarbonate (NaHCO3) solution was injected into porous <span class="hlt">olivine</span> aggregates and in-situ pore structure change during <span class="hlt">olivine</span> carbonation at a constant confining pressure (12 MPa) and a temperature of 200oC was captured at 30 min. interval for ~160 hours. Shortly after the experiment started, filling-in of the existing pores by precipitation of reaction products was visible. The size of the in-fills kept increasing as reactions continued. After ~48 hours, cracking around the in-fill materials became visible. After ~60 hours, these cracks started to show a clear polygonal pattern, similar to the crack patterns usually seen on the surface of drying mud. After ~72 hours, some of the cracks coalesced into large fractures that cut-through the <span class="hlt">olivine</span> aggregates. New fractures continued to develop and at the end of the experiment, the sample was completely disintegrated by these fractures. We also conducted nanotomography experiments on a sub-volume of the reacted <span class="hlt">olivine</span> aggregate. Orthogonal sets of incipient cracks were observed, providing clear evidence that these cracks are generated by isotropic tensile stresses. This strongly indicates that the observed cracking was caused by volume expansion during mineral carbonation. The experimental results provide a mechanism for near 100% alteration of ultramafic rocks observed in nature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMMR33A1844R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMMR33A1844R"><span id="translatedtitle">Diffusion of REE, Hf and Sr in <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Remmert, P.; Dohmen, R.; Chakraborty, S.</p> <p>2008-12-01</p> <p>We have determined diffusion coefficients of the rare earth elements Ce, Nd, Sm, Eu, Lu, and also of Sr and Hf, in single crystals of natural <span class="hlt">olivine</span> at atmospheric pressure, at an oxygen fugacity of 10-5 Pa and a temperature of 1275 °C. Sources of diffusants were thin films of <span class="hlt">olivine</span> composition doped with the relevant elements. Thin films were produced by PLD (pulsed laser deposition) and RBS (Rutherford backscattering) was used to measure thickness and stoichiometry of the films as well as to analyze the concentration profiles. The concentration profiles were numerically fitted to yield the following diffusion coefficients (D, in m2/s): log DCe: -19.61 ± 0.21; log DNd: -19.54 ± 0.11; log DSm: -19.15 ± 0.05; log DEu: -19.10; log DLu: -19.00, log DHf: -20.23 ± 0.07; log DSr: -18.7. Diffusion coefficients of the rare-earth elements increase from Ce to Lu, demonstrating the role of ionic radius in controlling diffusion because all REE are trivalent. The tetravalent and divalent cations hafnium and strontium diffuse an order of magnitude slower and faster, respectively, than the REE in <span class="hlt">olivine</span>. This highlights the important influence of ionic charge on diffusion rates. The diffusion coefficients of the REE are slower by a few orders of magnitudes than the diffusion rate of Cr in <span class="hlt">olivine</span> [1]. The rates found in this study are slower than those assumed by a model [2] for compositional modification of melt inclusions in <span class="hlt">olivine</span>. Use of our data in their calculations indicates that it will take longer to modify the composition of melt inclusions in <span class="hlt">olivine</span> (millions of years rather than thousands of years) but the fractionation of HREE from LREE will be larger. [1] Ganguly J, Ito M (2006) Geochim Cosmochim Acta, 70, 799-809. [2] Cottrell E, Spiegelman M, Langmuir CH (2002) Geochem Geophys Geosyst, doi:10.1029/2001GC000205</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20719461','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20719461"><span id="translatedtitle">Measurements of vertical <span class="hlt">bar</span> Vcb vertical <span class="hlt">bar</span> and vertical <span class="hlt">bar</span> Vub vertical <span class="hlt">bar</span> at Ba<span class="hlt">Bar</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rotondo, M.</p> <p>2005-10-12</p> <p>We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical <span class="hlt">bar</span> Vub vertical <span class="hlt">bar</span> matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19790063561&hterms=ionic+liquids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dionic%2Bliquids','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19790063561&hterms=ionic+liquids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dionic%2Bliquids"><span id="translatedtitle">The solubility of <span class="hlt">olivine</span> in basaltic liquids - An ionic model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Herzberg, C. T.</p> <p>1979-01-01</p> <p>A model is presented which enables the temperature at which <span class="hlt">olivine</span> is in equilibrium with any alkali-depleted basaltic compound to be calculated to within + or - 30 C. It is noted that the error increases substantially when applied to terrestrial basalts which contain several weight percent alkalis. In addition the model predicts and quantifies the reduced activity of SiO4(4-) monomers due to increasing SiO2 concentrations in the melt. It is shown that the coordination of alumina in melts which precipitate <span class="hlt">olivine</span> only appears to be dominantly octahedral, while titanium acts as a polmerizing agent by interconnecting previously isolated SiO4(4-) monomers. It is concluded that the model is sufficiently sensitive to show that there are small repulsive forces between Mg(2+) and calcium ions which are in association with normative diopside in the melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeCoA.156..145W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeCoA.156..145W"><span id="translatedtitle">Helium diffusion in <span class="hlt">olivine</span> based on first principles calculations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Kai; Brodholt, John; Lu, Xiancai</p> <p>2015-05-01</p> <p>As a key trace element involved in mantle evolution, the transport properties of helium in the mantle are important for understanding the thermal and chemical evolution of the Earth. However, the mobility of helium in the mantle is still unclear due to the scarcity of measured diffusion data from minerals under mantle conditions. In this study, we used first principles calculations based on density functional theory to calculate the absolute diffusion coefficients of the helium in <span class="hlt">olivine</span>. Using the climbing images nudged elastic band method, we defined the diffusion pathways, the activation energies (Ea), and the prefactors. Our results demonstrate that the diffusion of helium has moderate anisotropy. The directionally dependent diffusion of helium in <span class="hlt">olivine</span> can be written in Arrhenius form as follows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMMR22A..03I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMMR22A..03I"><span id="translatedtitle">H defects in forsterite and <span class="hlt">olivine</span>: A critical review</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ingrin, J.</p> <p>2012-12-01</p> <p>The current state of knowledge of hydrogen defects in <span class="hlt">olivine</span>, highlighted by the recent results of numerical modelling, infrared measurements and experiments is presented. In laboratory's experiments, two types of defects control the solubility of water at high pressure: a defect associated with silicon vacancies and a defect of unknown origin identified in infrared by a single OH band at 3555 cm-1. At low pressure and in natural samples, the dominant defects are linked to Ti4+ and trivalent substitutions and more occasionally to defects associated to Si vacancies, Mg vacancies or even the unknown defect at 3555 cm-1. Mosenfelder et al. (2006) [1] already pointed out the difference of incorporation mechanisms between low and high-pressure experiments. We speculate on the impact of different defects on the solubility laws of hydrogen in <span class="hlt">olivine</span> and their consequences for mantle solubility. [1] Mosenfelder et al. (2006) Amer. Min., 91, 285-294.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/898860','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/898860"><span id="translatedtitle">Grinding methods to enhance the reactivity of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Summers, Cathy A.; Dahlin, David C.; Rush, Gilbert E.; O'Connor, William K.; Gerdemann, Stephen J.</p> <p>2005-08-01</p> <p>The Albany Research Center (ARC) conducted studies of mechanical activation by conventional and ultrafine grinding techniques to enhance <span class="hlt">olivine</span> reactivity in mineral carbonation reactions. Activated <span class="hlt">olivine</span> is one of several solid feed materials used at ARC in reactions with carbon dioxide to form carbonate minerals. This paper compares grinding techniques via energy demand data and product characteristics, including particle size distributions, surface areas, full-width-at-half-maximum (FWHM) XRD analyses, and particle morphology by SEM analyses. Reactivity was calculated by percent conversion to carbonate in subsequent carbonation tests. Particle size reduction has the greatest impact on reactivity, and wet grinding is more energy efficient than dry grinding. Large additional inputs of energy to increase surface area or reduce crystallinity do not result in proportional improvements in reactivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.V51A2774Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.V51A2774Q"><span id="translatedtitle">Experimental study of Mg isotope fractionation during <span class="hlt">olivine</span> dissolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qiu, L.; Wang, Z.</p> <p>2012-12-01</p> <p>The dissolution of silicate minerals plays important roles in modifying the chemical composition of the ocean and earth crust. Previous studies show secondary clay minerals produced as a by-product of dissolution are enriched in heavy Mg isotopes compared with their protolith. In this study, batch <span class="hlt">olivine</span> dissolution experiments were conducted in an autoclave to understand the evolution of Mg isotope composition in the solution as a function of controlled experimental conditions, including initial pH of the fluid (10.02 or 2.02), temperature (50, 100, or 200oC), <span class="hlt">olivine</span>-grain size (<30μm powder or single <span class="hlt">olivine</span> grain of ~0.2g/each), and duration of the experiments (up to ~60 hours). At the end of experiments, solid minerals were characterized by SEM and EM, and the solution was analyzed for major and trace element, and Mg isotope compositions by Element-XR and Neptune at Yale University. The Mg/Si ratio of the solution and the SEM and EM characterization of the solid phases indicate the formation of secondary mineral-talc in experiments with alkaline solutions, is consistent with the calculated saturation index. Significant Mg isotope fractionations were also observed in these experiments, which decrease with increasing temperature (e.g., up to ~ -5.8‰ at 50oC vs. -0.72 ‰ at 200oC), but increase with increasing the duration of the experiments. In contrast, little fractionation was observed in experiments with acidic solutions at low temperatures, or short duration of the experiments at high temperatures. These results indicate that dissolution of <span class="hlt">olivine</span> (even in our closed system experiments) is a surface controlled process, during which Mg isotopes fractionate insignificantly, whereas secondary minerals formed during the process are strongly enriched in heavy Mg isotopes, leaving the solutions depleted in 26Mg. The fractionation factors between solution and talc have been estimated for these experiments as well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890001422','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890001422"><span id="translatedtitle">Chemical frost weathering of <span class="hlt">olivine</span>: Experimental study and implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Harris, S. L.; Huguenin, R. L.</p> <p>1987-01-01</p> <p>New experimental results are reported on the frost weathering of <span class="hlt">olivine</span>. After first weathering, a decrease in Fe sup 2(+)M(2) absorption bands were noted. This decrease is related to the protonation of O(+) in the mineral. It is contented that this reaction may result in the regolith storage of 100 to 1000 m of H(sub 2) over the history of Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=lobbying&pg=4&id=EJ920878','ERIC'); return false;" href="http://eric.ed.gov/?q=lobbying&pg=4&id=EJ920878"><span id="translatedtitle">Breaking through the <span class="hlt">Bar</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gray, Katti</p> <p>2011-01-01</p> <p>Howard University School of Law had a problem, and school officials knew it. Over a 20-year period, 40 percent of its graduates who took the Maryland <span class="hlt">bar</span> exam failed it on their first try. During the next 24 months--the time frame required to determine its "eventual pass rate"--almost 90 percent of the students did pass. What they did not know was…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17066032','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17066032"><span id="translatedtitle">The effect of water on the electrical conductivity of <span class="hlt">olivine</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Duojun; Mookherjee, Mainak; Xu, Yousheng; Karato, Shun-ichiro</p> <p>2006-10-26</p> <p>It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of <span class="hlt">olivine</span>, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of <span class="hlt">olivine</span> aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline <span class="hlt">olivine</span> was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%. PMID:17066032</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeoRL..36.4304D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeoRL..36.4304D"><span id="translatedtitle">Experimental deformation of <span class="hlt">olivine</span> single crystals at lithospheric temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Demouchy, Sylvie; Schneider, Stephen E.; Mackwell, Stephen J.; Zimmerman, Mark E.; Kohlstedt, David L.</p> <p>2009-02-01</p> <p>Rheological properties of mantle minerals and rocks at temperatures (T) appropriate to much of Earth's lithosphere have remained poorly constrained, even though past experimental studies on <span class="hlt">olivine</span> single crystals and polycrystalline aggregates have quantified the high-temperature creep mechanisms (T > 1200°C). Consequently, we have performed deformation experiments on crystals of San Carlos <span class="hlt">olivine</span> at lower temperatures, from 900° to 1200°C, in triaxial compression along the [101]c direction. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at differential stresses of 100 to 500 MPa. Several samples were deformed at constant displacement rate and others at constant load, in order to provide insight into possible effects of work-hardening. Under the deformation conditions investigated, little evidence of work-hardening was observed. The data follow a power-law dependence on stress, as in previous high-temperature deformation studies. The samples were, however, considerably weaker than predicted by the experimentally determined high-temperature constitutive equation for <span class="hlt">olivine</span> crystals of this orientation from the study of Bai et al. (1991). The mechanical behavior correlates instead with the weaker of the two mechanisms (flow laws) that contribute to the high-temperature constitutive equation. Thus, our experiments demonstrate that published high-temperature constitutive equations overestimate the strength of lithospheric mantle and that the transition to low-temperature creep occurs at lower temperatures than previously inferred.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PEPI..172...67D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PEPI..172...67D"><span id="translatedtitle">New measurements of activation volume in <span class="hlt">olivine</span> under anhydrous conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Durham, W. B.; Mei, S.; Kohlstedt, D. L.; Wang, L.; Dixon, N. A.</p> <p>2009-01-01</p> <p>A new cell assembly for the deformation-DIA (D-DIA) shows promise for limiting the water content of samples and providing a more mechanically stable environment for deformation. The 6-mm cubic cell consists of a 6-mm diameter mullite sphere cradled in a web of unfired pyrophyllite. The pyrophyllite flows during initial compression of the D-DIA to form gaskets between the six anvils while the mullite flows to become a nearly cubic-shaped pressure medium. Measurements on <span class="hlt">olivine</span> indicate more than one order of magnitude drop in water content to <40 ppm H/Si compared with the boron-epoxy medium. Improved mechanical stability is achieved by elimination of the thermocouple from the assembly and determination of temperature from calibration curves of furnace power vs. temperature. Three samples of polycrystalline orthopyroxene-buffer San Carlos <span class="hlt">olivine</span> have been deformed in high-temperature creep in the new cell, at pressures of 2.7-4.9 GPa and temperatures near 1473 K. Strength is consistent with that measured in the gas-apparatus at lower pressures. Over the pressure range investigated we resolve an activation volume for creep of dry <span class="hlt">olivine</span> of V* = 9.5 ± 7 × 10 -6 m 3/mol.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DPS....4730108D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DPS....4730108D"><span id="translatedtitle"><span class="hlt">Olivine</span>-rich asteroids in the main asteroid belt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>DeMeo, Francesca E.; Polishook, David; Carry, Benoit; Moskovitz, Nick; Burt, Brian; Binzel, Rick</p> <p>2015-11-01</p> <p><span class="hlt">Olivine</span>-dominated asteroids, classified as A-types with near-infrared spectral measurements are largely thought to be the mantle remnants of disrupted differentiated small bodies. These A-type asteroids hold clues to asteroid differentiation and to the collisional history of those differentiated bodies. Preliminary studies of the abundance and distribution of A-type asteroids were performed by Carvano et al. (2010) and DeMeo & Carry (2013, 2014) using the Sloan Digital Sky Survey (SDSS). To confidently identify these <span class="hlt">olivine</span>-dominated A-type asteroids, however, near-infrared spectral measurements are needed to identify the distinct broad and deep 1-micron <span class="hlt">olivine</span> absorption feature. Using the Sloan Digital Sky Survey Moving Object Catalog to select A-type asteroid candidates, we have performed a near-infrared spectral survey of over 70 asteroids with SpeX on the IRTF. We present the abundance and distribution of A-type asteroids throughout the main asteroid belt and compare these results with similar surveys for basalt-rich V-type asteroids (e.g. Moskovitz et al. 2008). This work is supported by NASA under grant number NNX12AL26G issued through the Planetary Astronomy Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120.6039T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120.6039T"><span id="translatedtitle">Creep behavior of Fe-bearing <span class="hlt">olivine</span> under hydrous conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tasaka, Miki; Zimmerman, Mark E.; Kohlstedt, David L.</p> <p>2015-09-01</p> <p>To understand the effect of iron content on the creep behavior of <span class="hlt">olivine</span>, (MgxFe(1 - x))2SiO4, under hydrous conditions, we have conducted tri-axial compressive creep experiments on samples of polycrystalline <span class="hlt">olivine</span> with Mg contents of x = 0.53, 0.77, 0.90, and 1. Samples were deformed at stresses of 25 to 320 MPa, temperatures of 1050° to 1200°C, a confining pressure of 300 MPa, and a water fugacity of 300 MPa using a gas-medium high-pressure apparatus. Under hydrous conditions, our results yield the following expression for strain rate as a function of iron content for 0.53 ≤ x ≤ 0.90 in the dislocation creep regime: ɛ˙=ɛ˙0.90((1-x/0.1))1/2exp[226×1030.9-x/RT]. In this equation, the strain rate of San Carlos <span class="hlt">olivine</span>, ɛ˙0.90, is a function of T, σ, and fH2O. As previously shown for anhydrous conditions, an increase in iron content directly increases creep rate. In addition, an increase in iron content increases hydrogen solubility and therefore indirectly increases creep rate. This flow law allows us to extrapolate our results to a wide range of mantle conditions, not only for Earth's mantle but also for the mantle of Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GeoOD..52..566B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GeoOD..52..566B"><span id="translatedtitle">Ontogenetic analysis of individual <span class="hlt">olivine</span> grains in ultramafic rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brodskaya, R. L.; Bilskaya, I. V.; Markovsky, B. A.</p> <p>2010-12-01</p> <p>The morphology and internal structure of individual <span class="hlt">olivine</span> grains from ultramafic rocks in the Guli and Gal'moenan dunite massifs differing in origin are considered. To restore the ontogeny of mineral aggregates, traces of elastic deformation retained in mineral grains have been used. Comparison of anatomy of <span class="hlt">olivine</span> grains from these two massifs showed that the mechanism of accommodation of rocks to changing geological settings is expressed as the response of the mineral aggregate structure and variation in the anatomy of individual mineral grains. At the level of individual grains, this is annihilation of older defects and origination of younger dislocations; refinement of the crystal lattice; exsolution; formation and transformation of new mineral phases; and creep and migration of subboundaries within grains. At the aggregate level, this is rotation and migration creep of the internal boundaries of rock; formation of new boundaries of mineral intergrowths; reorientation of boundaries; and variation in their extent, density, and grain dimensions. The prehistory of massifs controls the manifestation and abundance of various elastic deformations and related types of recrystallization of <span class="hlt">olivine</span> grain boundaries and subboundaries in aggregates. New conditions and accommodation of mineral aggregates to these conditions have instigated specific schemes of recrystallization, which bear information on the history of rocks and their massifs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012IJMMM..19..185K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012IJMMM..19..185K"><span id="translatedtitle">Value enhancement of <span class="hlt">olivine</span> process dust through air classification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kleiv, R. A.</p> <p>2012-03-01</p> <p>As a result of the production of dry <span class="hlt">olivine</span> sand products at A/S <span class="hlt">Olivin</span>'s production plant at Åheim in western Norway, an annual quantity of some 20000-30000 t of process dust is produced. The bulk of this material is currently being sold as a slag conditioner at a relatively low price; hence, alternative uses of the process dust are now being sought. Information regarding the chemical composition of the material as a function of particle size facilitates product modifications through exclusion or mixing of individual size fractions. This paper demonstrates how such information can be obtained from air classification experiments when these are combined with chemical analysis of the produced size fractions. The classification and subsequent analysis of the <span class="hlt">olivine</span> process dust revealed that the finer size fractions had high loss on ignition (LOI) values and were relatively low in MgO when compared with the bulk analysis. Removal of the finer fractions resulted in a remaining coarse product of significantly higher quality. The coarse material could be used as a raw material for further processing; it could be recycled or it could constitute a new product in itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PNAS..10213755B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PNAS..10213755B"><span id="translatedtitle">Volatile fractionation in the early solar system and <span class="hlt">chondrule</span>/matrix complementarity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bland, Philip A.; Alard, Olivier; Benedix, Gretchen K.; Kearsley, Anton T.; Menzies, Olwyn N.; Watt, Lauren E.; Rogers, Nick W.</p> <p>2005-09-01</p> <p>Bulk chondritic meteorites and terrestrial planets show a monotonic depletion in moderately volatile and volatile elements relative to the Sun's photosphere and CI carbonaceous chondrites. Although volatile depletion was the most fundamental chemical process affecting the inner solar nebula, debate continues as to its cause. Carbonaceous chondrites are the most primitive rocks available to us, and fine-grained, volatile-rich matrix is the most primitive component in these rocks. Several volatile depletion models posit a pristine matrix, with uniform CI-like chemistry across the different chondrite groups. To understand the nature of volatile fractionation, we studied minor and trace element abundances in fine-grained matrices of a variety of carbonaceous chondrites. We find that matrix trace element abundances are characteristic for a given chondrite group; they are depleted relative to CI chondrites, but are enriched relative to bulk compositions of their parent meteorites, particularly in volatile siderophile and chalcophile elements. This enrichment produces a highly nonmonotonic trace element pattern that requires a complementary depletion in <span class="hlt">chondrule</span> compositions to achieve a monotonic bulk. We infer that carbonaceous chondrite matrices are not pristine: they formed from a material reservoir that was already depleted in volatile and moderately volatile elements. Additional thermal processing occurred during <span class="hlt">chondrule</span> formation, with exchange of volatile siderophile and chalcophile elements between <span class="hlt">chondrules</span> and matrix. This chemical complementarity shows that these chondritic components formed in the same nebula region. Author contributions: P.A.B. designed research; P.A.B., O.A., G.K.B., A.T.K., O.N.M., L.E.W., and N.W.R. performed research; P.A.B., O.A., G.K.B., and A.T.K. analyzed data; and P.A.B. wrote the paper.This paper was submitted directly (Track II) to the PNAS office.Freely available online through the PNAS open access option.Abbreviations: CAI, Ca-Al-rich refractory inclusion; LA, laser ablation; ICP, inductively coupled plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20060049097&hterms=inclusion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dinclusion','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20060049097&hterms=inclusion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dinclusion"><span id="translatedtitle">Non-nebular Origin of Dark Mantles Around <span class="hlt">Chondrules</span> and Inclusions in CM Chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Trigo-Rodriquez, Josep M.; Rubin, Alan E.; Wasson, John T.</p> <p>2006-01-01</p> <p>Our examination of nine CM chondrites that span the aqueous alteration sequence leads us to conclude that compact dark fine mantles surrounding <span class="hlt">chondrules</span> and inclusions in CM chondrites are not discrete fine-grained rims acquired in the solar nebula as modeled by Metzler et al. [Accretionary dust mantles in CM chondrites: evidence for solar nebula processes. Geochim. Cosmochim. Acta 56, 1992, 2873-28971. Nebular processes that lead to agglomeration produce materials with porosities far higher than those in the dark mantles. We infer that the mantles were produced from porous nebular materials on the CM parent asteroid by impact-compaction (a process that produces the lowest porosity adjacent to <span class="hlt">chondrules</span> and inclusions). Compaction was followed by aqueous alteration that formed tochilinite, serpentine, Ni-bearing sulfide, and other secondary products in voids in the interchondrule regions. Metzler et al. reported a correlation between mantle thickness and the radius of the enclosed object. In Yamato 791 198 we find no correlation when all sizes of central objects and dark lumps are included but a significant correlation (r(sup 2) = 0.44) if we limit consideration to central objects with radii >35 microns; a moderate correlation is also found in QUE 97990. We suggest that impact-induced shear of a plum-pudding-like precursor produced the observed "mantles"; these were shielded from comminution during impact events by the adjacent stronger <span class="hlt">chondrules</span> and inclusions. Some mantles in CM chondrites with low degrees of alteration show distinct layers that may largely reflect differences in porosity. Typically, a gray, uniform inner layer is surrounded by an outer layer consisting of darker silicates with BSE-bright speckles. The CM-chondrite objects characterized as "primary accretionary rocks" by Metzler et al. did not form in the nebula, but rather on the parent body. The absence of solar-flare particle tracks and solar-wind-implanted rare gases in these clasts reflect their lithified nature and low surface/volume ratios during the period when they resided in the regolith and were subject to irradiation by solar particles. The clasts are analogous to the light-colored metamorphosed clasts in ordinary-chondrite regolith breccias (which also lack solar-flare particle tracks and solar-wind gas).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/872825','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/872825"><span id="translatedtitle"><span class="hlt">Bar</span> coded retroreflective target</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Vann, Charles S.</p> <p>2000-01-01</p> <p>This small, inexpensive, non-contact laser sensor can detect the location of a retroreflective target in a relatively large volume and up to six degrees of position. The tracker's laser beam is formed into a plane of light which is swept across the space of interest. When the beam illuminates the retroreflector, some of the light returns to the tracker. The intensity, angle, and time of the return beam is measured to calculate the three dimensional location of the target. With three retroreflectors on the target, the locations of three points on the target are measured, enabling the calculation of all six degrees of target position. Until now, devices for three-dimensional tracking of objects in a large volume have been heavy, large, and very expensive. Because of the simplicity and unique characteristics of this tracker, it is capable of three-dimensional tracking of one to several objects in a large volume, yet it is compact, light-weight, and relatively inexpensive. Alternatively, a tracker produces a diverging laser beam which is directed towards a fixed position, and senses when a retroreflective target enters the fixed field of view. An optically <span class="hlt">bar</span> coded target can be read by the tracker to provide information about the target. The target can be formed of a ball lens with a <span class="hlt">bar</span> code on one end. As the target moves through the field, the ball lens causes the laser beam to scan across the <span class="hlt">bar</span> code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020046564&hterms=dating&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Ddating','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020046564&hterms=dating&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Ddating"><span id="translatedtitle">I-Xe Dating: Comparison of I-Xe and Pb-Pb Ages of Richardton <span class="hlt">Chondrules</span> and Separated Mineral Phases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pravdivtseva, O. V.; Amelin, Y.; Hohenberg, C. M.; Meshik, A. P.</p> <p>2002-01-01</p> <p>I-Xe and Pb-Pb ages of individual Richardton <span class="hlt">chondrules</span> and different mineral phases were compared in order to test the absolute I-Xe age normalization. Additional information is contained in the original extended abstract.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015LPICo1856.5112A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015LPICo1856.5112A"><span id="translatedtitle">Quantifying the Deformation of Leoville <span class="hlt">Chondrules</span> in 3D: Implications for the Post-Accretional History of the CV3 Parent Body</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Almeida, N. V.; Smith, C. L.; Sykes, D.; Downes, H.; Ahmed, F.; Russell, S. S.</p> <p>2015-07-01</p> <p>Micro-CT scanning allows for the three-dimensional analysis of both degree of deformation and direction of preferred orientation of <span class="hlt">chondrules</span> in the Leoville CV3 meteorite, indicating post-accretional impact as the cause for the foliation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR33B2333J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR33B2333J"><span id="translatedtitle">Si-rich layer formation on <span class="hlt">olivine</span> surfaces during reaction with water and supercritical carbon dioxide under conditions relevant for geologic carbon storage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnson, N. C.; Jackson, A.; Maher, K.; Bird, D. K.; Brown, G. E.</p> <p>2013-12-01</p> <p>The reaction of Mg-silicate minerals (i.e. <span class="hlt">olivine</span>) with carbon dioxide (CO2) is a promising method for secure, long-term, geologic carbon storage. Several technical challenges must be overcome before implementing mineral carbonation technology on a large scale, one of which is slow reaction kinetics. This study probes surface reaction limitations of <span class="hlt">olivine</span> carbonation, specifically the formation of a passivating, Si-rich layer on <span class="hlt">olivine</span> surfaces upon exposure to water and CO2 under sequestration conditions (elevated temperature and pressure). A series of batch reactions were performed at 60°C and 100 <span class="hlt">bar</span> CO2 pressure in Dickson-style rocker bombs, varying the length of reaction and the amount of mixing (rocking). The initial aqueous phase was spiked with 29Si. Fluid samples were taken periodically and analyzed for cation content, alkalinity, and dissolved inorganic carbon. At the end of each experiment, the solid products were analyzed with a Sensitive High Resolution Ion Microprobe Reverse Geometry (SHRIMP-RG) in order to measure the amount of 29Si incorporated into the Si-rich layer on reacted <span class="hlt">olivine</span> grains. We also cut cross sections of reacted grains from each experiment using a Focused Ion Beam (FIB) which were thinned to <100nm and imaged using Transmission Electron Microscopy (TEM). SHRIMP-RG results show incorporation of 29Si on <span class="hlt">olivine</span> grain surfaces reacted for 19 days with no mixing, and TEM images of <span class="hlt">olivine</span> grains from the same experiment show an amorphous, Si-rich layer that is 30nm thick. Similarly, SHRIMP-RG results for <span class="hlt">olivine</span> grains reacted for 19 days with mixing indicate 29SiO2 precipitation and TEM images reveal a Si-rich layer 60nm thick. In both experiments, EDS (energy dispersive spectroscopy) data show a step change in composition from the bulk rock to the surface layer in addition to the sharp crystalline/amorphous interface visible in the TEM images. <span class="hlt">Olivine</span> from the unmixed experiment also has a slow decrease in Mg relative to Si before the step change, suggesting that, at least in this experiment, a Si-rich layer precipitated on top of a Mg-depleted layer that formed via a leaching process. SHRIMP-RG data also imply the presence of a precipitated Si-rich layer on top of a leached Si-rich layer, as the 29Si penetration depth is only 25-65% of the total Si-rich layer thickness. The combination of SHRIMP-RG and FIB/TEM analysis leads us to hypothesize that a Si-rich layer forms quickly on <span class="hlt">olivine</span> surfaces due to preferential Mg removal from the surface (the traditional 'leached' layer), and as the reaction proceeds, amorphous silica reaches saturation in the fluid and precipitates on surfaces inside the reactor (including <span class="hlt">olivine</span> grains).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011Litho.127..505M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011Litho.127..505M"><span id="translatedtitle">Petrogenesis and Nd-, Pb-, Sr-isotope geochemistry of the Cenozoic <span class="hlt">olivine</span> melilitites and <span class="hlt">olivine</span> nephelinites (ankaratrites) in Madagascar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Melluso, Leone; le Roex, Anton P.; Morra, Vincenzo</p> <p>2011-12-01</p> <p>The Cenozoic ankaratrites of the Alaotra, Takarindoha-Vatomandry and Votovorona (NE Ankaratra) volcanic fields, Madagascar, range from <span class="hlt">olivine</span> ( monticellite) melilitites, through <span class="hlt">olivine</span>-melilite nephelinites to <span class="hlt">olivine</span> ( leucite) nephelinites. The rocks show significant compositional ranges in their coexisting magmatic minerals (<span class="hlt">olivine</span>-group minerals, melilite, clinopyroxene, nepheline, leucite, Ba-phlogopite, perovskite, ilmenite, spinels, apatite), and evidence of distinct parental magmas, often in different facies of the same vent. Primitive compositions (high Mg#, Cr and Ni concentrations) are found in each volcanic district, and a few lavas contain mantle xenoliths or xenocrysts. The rocks show enrichment in the most strongly incompatible elements (e.g., Ba and Nb up to 200 times primitive mantle, La/Ybn = 24 to 40), with troughs at K and smooth, decreasing patterns towards the least incompatible elements in mantle-normalized diagrams. The Nd-Pb-Sr isotope geochemistry indicates a marked heterogeneity of the mantle sources of the various districts (e.g., 206Pb/204Pb = 18.68-18.77, 87Sr/86Sr = 0.704011-0.704207 for the Alaotra-Votovorona districts; 206Pb/204Pb = 19.04-19.14, 87Sr/86Sr = 0.703544-0.704017 for the Takarindoha-Vatomandry districts), with significant differences to other Cenozoic mafic volcanic rocks of northern Madagascar. The genesis of the Madagascan ankaratrites is related to rifting events which triggered low-degree partial melting of a garnet peridotite enriched in dolomite and incompatible-element-rich phases, in the lowermost lithosphere. Despite marked geochemical similarities, the source of the Madagascan melilitites bears no isotopic similarity to the HIMU-related sources of melilitites of eastern and southern Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeCoA.119....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeCoA.119....1M"><span id="translatedtitle">LA-ICP-MS mapping of <span class="hlt">olivine</span> from the Brahin and Brenham meteorites: Complex elemental distributions in the pallasite <span class="hlt">olivine</span> precursor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKibbin, Seann J.; O'Neill, Hugh St. C.; Mallmann, Guilherme; Halfpenny, Angela</p> <p>2013-10-01</p> <p>To investigate the early history of <span class="hlt">olivine</span> from the Main-Group pallasites Brahin and Brenham, we have spatially mapped their trace-element distributions using laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS). Brahin <span class="hlt">olivine</span> interiors contain ˜100-200 μm patches enriched in Cr, Al, Ti, V, Sc and Ga, separated by linear enrichments of P; these structures bear no relation to current crystal morphologies. Rather, cross-cutting relationships suggest they predate <span class="hlt">olivine</span>-metal mixing. Brenham <span class="hlt">olivine</span> also has internal variations for these elements. By contrast, Ni and Co concentrations in <span class="hlt">olivine</span> from both meteorites decrease near crystal margins, as expected for freezing-in of profiles formed during diffusive re-equilibration with metal during cooling. Brenham <span class="hlt">olivine</span> also has decreasing Al, Cr and Ti near the margin. Correlations between concentrations of Cr and Al exist for individual Brahin <span class="hlt">olivine</span> grains, but do not hold over multiple grains, indicating a heterogeneous precursor. Al and Ti are correlated over multiple grains in Brahin, interpreted as Ti cations decorating pre-existing Al-defects. In Brenham <span class="hlt">olivine</span>, similar geochemical trends exist, but the Cr-Al relationship probably represents both grain margin effects and pre-existing internal heterogeneity. The preservation of structure for elements which are normally fast diffusers in <span class="hlt">olivine</span> hinges on coupled substitutions involving Al, which along with P diffuses much more slowly than most other elements under some conditions. Al concentrations in <span class="hlt">olivine</span> are low and variable (3-33 ppm) which is inconsistent with crystallisation from a normal silicate melt; Al-in-<span class="hlt">olivine</span> thermometers indicate that pallasite <span class="hlt">olivine</span> was formed in a low-temperature environment. Following its delivery to the magma ocean/core-mantle boundary, Al-P systematics were not substantially modified. Assuming diffusivities for Al and P that are similar to Si (since they reside in the same crystallographic site) and temperatures of 1600-1650 K (from the melting point of the metal and the absence of orthopyroxene in pallasites) an upper limit on the residence time of pallasite <span class="hlt">olivine</span> of ˜1 Ma can be inferred by the persistence of trace element detail over scales of 100 μm. Following the <span class="hlt">olivine</span>-metal mixing event, homogeneous Ni and Co distributions were modified by diffusion; Cr and V were partially modified; Al and P were essentially unchanged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9010B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9010B"><span id="translatedtitle">Annealing of deformed <span class="hlt">olivine</span> single-crystals under 'dry' conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blaha, Stephan; Katsura, Tomoo</p> <p>2013-04-01</p> <p>Knowledge of rheological properties of Earth's materials is essential to understand geological processes. Open questions are the water content and crystallographic orientation dependences of dislocation creep rate, because the dominant slip system changes with increasing water content, which suggest different dislocations have different water content dependence. This project focuses on <span class="hlt">olivine</span>, which is the most abundant mineral of the upper mantle. It is also considered to be the weakest phase and hence should control the rheology of the upper mantle. Several slip systems were reported for <span class="hlt">olivine</span>, which are [100](010), [001](010), [001](100) and [100](001), each of which appear under different water content and stress conditions [1]. For this purpose we started to obtain data for 'dry' conditions, providing basic knowledge to understand the effect of water. Variation in dislocation creep rate according to change in physical conditions can be estimated by dislocation recovery experiments [2]. In this technique, deformed crystals are annealed, in which the dislocation density is expected to decrease due to coalescence of two dislocations. Dislocation densities are measured before and after the annealing. Dislocation mobility, which should be directly proportional to the dislocation creep rate, is estimated based on the change in dislocation density and duration of annealing. This technique has significant advantages partly because informations of strain rate and deviatoric stress, which are difficult to measure, are unnecessary, and partly because dislocation annealing is conducted under quasi-hydrostatic conditions, which allows wide ranges of P and T conditions. The first step of the experiments is to deform a single crystal of <span class="hlt">olivine</span>. For this purpose, we developed an assembly, which deforms a single crystal in simple-shear geometry and prevent breakage, sub-grain formation and recrystallization of the crystal. <span class="hlt">Olivine</span> single-crystals were placed in the high-pressure assembly so that a particular slip system is activated. The assemblies were compressed to 3 GPa. The shear deformation was conducted at 1600 K. EBSD measurements indicate that the recovered crystals are single crystals and sub-grain formation did not occur in most cases. The second step is to anneal the samples under the same P-T conditions as those of the deformation experiments. Annealing experiments are also performed at ambient pressures at 1600 K. Dislocation density was measured by means of the oxidation decoration technique [3]. The samples were firstly polished and then oxidized at 1200 K for 50 min. The dislocations are preferably oxidized, so that presence of dislocation can be observed using SEM. First Results indicate that the dislocation density decreased by annealing by 1/4 with an annealing period of 10 h for dislocations with b = [001]. References [1] H. Jung and S. I. Karato. Water-induced fabric transitions in <span class="hlt">olivine</span>. Science, 293(5534):1460-1463, 2001. [2] S. I. Karato, D. C. Rubie, and H. Yan. Dislocation recovery in <span class="hlt">olivine</span> under deep upper mantle conditions: Implications for creep and diffusion. Journal of Geophysical Research, 98(B6):9761-9768, 1993. [3] D. L. Kohlstedt, C. Goetze, W. B. Durham, and J. V. Sande. New technique for decorating dislocations in <span class="hlt">olivine</span>. Science, 191(4231):1045-1046, March 1976.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19800065203&hterms=solar+chemical+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsolar%2Bchemical%2Benergy','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19800065203&hterms=solar+chemical+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsolar%2Bchemical%2Benergy"><span id="translatedtitle">Chemical energy in cold-cloud aggregates - The origin of meteoritic <span class="hlt">chondrules</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clayton, D. D.</p> <p>1980-01-01</p> <p>If interstellar particles and molecules accumulate into larger particles during the collapse of a cold cloud, the resulting aggregates contain a large store of internal chemical energy. It is here proposed that subsequent warming of these accumulates leads to a thermal runaway when exothermic chemical reactions begin within the aggregate. These, after cooling, are the crystalline <span class="hlt">chondrules</span> found so abundantly within chondritic meteorites. Chemical energy can also heat meteoritic parent bodies of any size, and both thermal metamorphism and certain molten meteorites are proposed to have occurred in this way. If this new theory is correct, (1) the model of chemical condensation in a hot gaseous solar system is eliminated, and (2) a new way of studying the chemical evolution of the interstellar medium has been found. A simple dust experiment on a comet flyby is proposed to test some features of this controversy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SolED...5.2283J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SolED...5.2283J"><span id="translatedtitle">The morphology and surface features of <span class="hlt">olivine</span> in kimberlite lava: implications for ascent and emplacement mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, T. J.; Russell, J. K.; Porritt, L. A.; Brown, R. J.</p> <p>2013-12-01</p> <p>Many kimberlite rocks contain large proportions of ellipsoidal-shaped xenocrystic <span class="hlt">olivine</span> grains that are derived mainly from the disaggregation of peridotite. Xenocrystic <span class="hlt">olivine</span> grains from a lava erupted from the Quaternary Igwisi Hills kimberlites, Tanzania, are compared to phenocrystic <span class="hlt">olivine</span>, liberated from picritic lavas, and mantle <span class="hlt">olivine</span>, liberated from a fresh peridotite xenolith, in order to examine the potential modification of <span class="hlt">olivine</span> surface textures due to transport from the mantle to the surface within kimberlite magmas. Image analysis, SEM imagery and laser microscopy reveals significant differences in the surface features and morphologies of the three crystal populations. Xenocrystic <span class="hlt">olivine</span> grains are characterised by rough surfaces, ellipsoidal shapes and impact pits. Mantle <span class="hlt">olivines</span> are characterised by flaked surfaces and indented shapes consistent with growth as a crystal aggregates. Phenocrystic <span class="hlt">olivines</span> are smooth-surfaced and exhibit flat crystal faces. We infer that the distinctive shapes and surfaces of xenocrystic <span class="hlt">olivine</span> grains resulted from three distinct mechanical processes attending their rapid transport from their source in the mantle lithosphere: (1) penetrative flaking from micro-tensile failure induced by rapid decompression; (2) sustained abrasion and attrition arising from particle-particle collisions between grains in a turbulent, volatile-rich flow regime, and; (3) higher energy particle-particle collisions that produced impact cavities superimposed on decompression structures. The combination of these processes during the rapid ascent of kimberlite magmas is responsible for the distinctive ellipsoidal shape of <span class="hlt">olivine</span> xenocrysts found in kimberlites worldwide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC43E..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC43E..06S"><span id="translatedtitle">Effects of organic ligands and temperature variations on the kinetics of <span class="hlt">olivine</span> carbonation and the formation of associated secondary phases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sissmann, O.; Daval, D.; Martinez, I.; Brunet, F.; Verlaguet, A.; Pinquier, Y.; Guyot, F. J.</p> <p>2011-12-01</p> <p>The slow dissolution kinetics of Mg-rich silicates has become a critical issue for the geologic CO2 sequestration in basic rocks. Previous batch carbonation studies on San Carlos <span class="hlt">olivine</span> [1] performed in CO2 saturated water (at 90°C and P CO2 = 280 <span class="hlt">bar</span>) have focused on the role that secondary phases, such as amorphous silica layers (SiO2 (am)), have on the transport of reactants from and to the reactive surfaces. The fluid composition remained roughly constant over the duration of the experiment, close to saturation with respect to amorphous silica and with a [Mg2+]/[SiO2 (aq)] ratio close to stoechiometric release, suggesting a passivation of the <span class="hlt">olivine</span> surface by the silica layer. In order to accelerate the dissolution process, organic ligands such as citrate and acetate were added to the solutions and tested at 1M and 0.1M concentrations in similar batch experiments. An intrinsic increase of the dissolution rate of <span class="hlt">olivine</span> was expected [2], [3] prior to the formation of a passivating silica layer. Preliminary results confirm this idea since Mg was released in non-stoechimoetric proportions with respect to SiO2 (aq) (found to be in equilibrium with SiO2 (am)). Similarly, a slight increase of temperature (from 90°C to 120°C) accelerated the reaction kinetics as well, possibly impacting the textural properties of SiO2 (am). Current TEM investigations are directed to confirming a possible link between the observed increase of the rate and textural properties of secondary phases. In addition, because carbonate minerals have a retrograde solubility, thermodynamical modelling suggests that this temperature increase should allow the fluid to reach saturation with respect to carbonates before reaching saturation with respect to SiO2 (am). Enough Mg can therefore be released to initiate the formation of carbonates before the silica precipitates and passivates the <span class="hlt">olivine</span> surface. [1] Daval et al (2011), Chemical Geology, v.284, p.193-209 [2] Grandstaff, D.E. (1986) In: Colman, S.M., Dethier, D.P. Eds., Rates of Chemical Weathering of Rocks and Minerals. 41-57. [3] Krevor and Lackner (2009) Energy Procedia v 1, 4867-4871.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22050979','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22050979"><span id="translatedtitle">Calcio-<span class="hlt">olivine</span> {gamma}-Ca{sub 2}SiO{sub 4}: I. Rietveld refinement of the crystal structure</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gobechiya, E. R. Yamnova, N. A.; Zadov, A. E.; Gazeev, V. M.</p> <p>2008-05-15</p> <p>The structure of the natural mineral calcio-<span class="hlt">olivine</span> ({gamma}-Ca{sub 2}SiO{sub 4}) found in skarn xenoliths in the region of the Lakargi Mountain (North Caucasus, Kabardino-Balkaria, Russia) is refined by the Rietveld method [a = 5.07389(7) A, b = 11.21128(14) A, c = 6.75340(9) A, V = 384.170(5) A{sup 3}, Z = 4, {rho}{sub calcd} = 2.98 g/cm{sup 3}, space group Pbnm]. The X-ray diffraction pattern of a powdered sample is recorded on a STOE STADI MP diffractometer [{lambda}CuK{sub {alpha}1}; Ge(111) primary monochromator; 6.00{sup o} < 2{theta} < 100.88{sup o}; step width, 2.5{sup o} in 2{theta}; number of reflections, 224]. All calculations are performed with the WYRIET (version 3.3) software package. The structural model is refined in the anisotropic approximation to R{sub p} = 6.44, R{sub wp} = 8.52, R{sub exp} = 5.85, R{sub B} = 4.98, R{sub F} = 6.90, and s = 1.46. It is shown that the sample under investigation is a mixture of several mineral phases, among which calcio-<span class="hlt">olivine</span> (the natural analogue of the {gamma}-Ca{sub 2}SiO{sub 4} compound) (83%), hillebrandite (13%), and wadalite (4%) are dominant. Only the scale factors and the unit cell parameters are refined for hillebrandite Ca{sub 2}SiO{sub 3}(OH){sub 2} [a = 3.63472(16) A, b = 16.4140(10) A, c = 11.7914(8) A, space group Cmc2{sub 1}, Z = 6] and wadalite Ca{sub 6}Al{sub 5}Si{sub 2}O{sub 16}Cl{sub 3} (a = 12.0088 A, space group, I 4 <span class="hlt">bar</span> 3d, Z = 4). The results of the structure refinement of the main component of the sample confirm that the mineral calcio-<span class="hlt">olivine</span> is isostructural to the synthetic compound {gamma}-Ca{sub 2}SiO{sub 4}. The structure of this compound is formed by the heteropolyhedral framework composed of Ca octahedra joined together into <span class="hlt">olivine</span>-like ribbons and isolated Si tetrahedra.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50..944P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50..944P"><span id="translatedtitle">From <span class="hlt">olivine</span> to ringwoodite: a TEM study of a complex process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pittarello, Lidia; Ji, Gang; Yamaguchi, Akira; Schryvers, Dominique; Debaille, Vinciane; Claeys, Philippe</p> <p>2015-05-01</p> <p>The study of shock metamorphism of <span class="hlt">olivine</span> might help to constrain impact events in the history of meteorites. Although shock features in <span class="hlt">olivine</span> are well known, so far, there are processes that are not yet completely understood. In shock veins, <span class="hlt">olivine</span> clasts with a complex structure, with a ringwoodite rim and a dense network of lamellae of unidentified nature in the core, have been reported in the literature. A highly shocked (S5-6), L6 meteorite, Asuka 09584, which was recently collected in Antarctica by a Belgian-Japanese joint expedition, contains this type of shocked <span class="hlt">olivine</span> clasts and has been, therefore, selected for detailed investigations of these features by transmission electron microscopy (TEM). Petrographic, geochemical, and crystallographic studies showed that the rim of these shocked clasts consists of an aggregate of nanocrystals of ringwoodite, with lower Mg/Fe ratio than the unshocked <span class="hlt">olivine</span>. The clast's core consists of an aggregate of iso-oriented grains of <span class="hlt">olivine</span> and wadsleyite, with higher Mg/Fe ratio than the unshocked <span class="hlt">olivine</span>. This aggregate is crosscut by veinlets of nanocrystals of <span class="hlt">olivine</span>, with extremely low Mg/Fe ratio. The formation of the ringwoodite rim is likely due to solid-state, diffusion-controlled, transformation from <span class="hlt">olivine</span> under high-temperature conditions. The aggregate of iso-oriented <span class="hlt">olivine</span> and wadsleyite crystals is interpreted to have formed also by a solid-state process, likely by coherent intracrystalline nucleation. Following the compression, shock release is believed to have caused opening of cracks and fractures in <span class="hlt">olivine</span> and formation of <span class="hlt">olivine</span> melt, which has lately crystallized under postshock equilibrium pressure conditions as <span class="hlt">olivine</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130010925','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130010925"><span id="translatedtitle">A New Spinel-<span class="hlt">Olivine</span> Oxybarometer: Near-Liquidus Partitioning of V between <span class="hlt">Olivine</span>-Melt, Spinel-Melt, and Spinel-<span class="hlt">Olivine</span> in Martian Basalt Composition Y980459 as a Function of Oxygen Fugacity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Papike, J. J.; Le, L.; Burger, P. V.; Shearer, C. K.; Bell, A. S.; Jones, J.</p> <p>2013-01-01</p> <p>Our research on valence state partitioning began in 2005 with a review of Cr, Fe, Ti, and V partitioning among crystallographic sites in <span class="hlt">olivine</span>, pyroxene, and spinel [1]. That paper was followed by several on QUE94201 melt composition and specifically on Cr, V, and Eu partitioning between pyroxene and melt [2-5]. This paper represents the continuation of our examination of the partitioning of multivalent V between <span class="hlt">olivine</span>, spinel, and melt in martian <span class="hlt">olivine</span>-phyric basalts of Y980459 composition [6, 7]. Here we introduce a new, potentially powerful oxybarometer, V partitioning between spinel and <span class="hlt">olivine</span>, which can be used when no melt is preserved in the meteorite. The bulk composition of QUE94201 was ideal for our study of martian pyroxene-phyric basalts and specifically the partitioning between pyroxene-melt for Cr, V, and Eu. Likewise, bulk composition Y980459 is ideal for the study of martian <span class="hlt">olivine</span>-phyric basalts and specifically for <span class="hlt">olivine</span>-melt, spinel-melt, and spinel-<span class="hlt">olivine</span> partitioning of V as a function of oxygen fugacity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.1418F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.1418F"><span id="translatedtitle">Phosphorus zoning in <span class="hlt">olivine</span> of Kilauea Iki lava lake, Hawaii</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fabbrizio, Alessandro; Beckett, John R.; Baker, Michael B.; Stolper, Edward M.</p> <p>2010-05-01</p> <p>Kilauea Iki lava lake was formed when the lavas of the 1959 summit eruption of Kilauea volcano ponded in Kilauea Iki pit crater, as described by [1]. The main chamber of this lake has been drilled repeatedly from 1960 to 1981 as the lake has cooled and crystallized and partial descriptions of core can be found in [2-7]. The bulk of the core consists of a gray, <span class="hlt">olivine</span>-phyric basalt matrix [3]. Rapid diffusion of divalent cations through <span class="hlt">olivine</span> at magmatic temperatures can delete information on early-formed zoning and thus information on early magmatic history, recorded in <span class="hlt">olivine</span> during its growth, is often largely lost [8-11]. In the last years many studies [8-11] have shown that natural <span class="hlt">olivine</span>, terrestrial and extraterrestrial, from several localities and rock types can preserve a complex zoning in P (sometimes associated with Cr and Al). Simple crystallization experiments conducted by [10] and [11] were able to replicate these features (i.e., sector and oscillatory zoning). Here, we describe P, Cr and Al zoning in <span class="hlt">olivine</span> from the 1981 drilling of Kilauea Iki lava lake hole #1 (KI81-1) [6]. K? X-ray intensity maps and major and minor element quantitative analyses were obtained using the Caltech JEOL JXA-8200 electron microprobe. We acquired P, Cr, Al, Fe and Ti X-ray maps simultaneously at 15 kV and 400 nA, a beam diameter of 1 ?m, pixel spacing of 1-2 ?m, and count times of 420-1500 msec/step were used depending on the dimension of the crystal. 15 kV and 40 nA with a beam diameter of 1 ?m were used to collect quantitative analyses. P2O5 contents of the Iki <span class="hlt">olivines</span> range from below detection limit to 0.30 wt%. Zoning in phosphorus, based on X-ray intensity maps, was observed in all <span class="hlt">olivines</span> we examined. The P zoning patterns of the <span class="hlt">olivines</span> display several styles. P shows oscillatory zoning comparable to that seen in terrestrial and extraterrestrial igneous <span class="hlt">olivines</span> and in experimentally grown <span class="hlt">olivine</span> [8-11]; high P regions, inside the crystals, outline low P chambers and P enriched zones were also observed; near the margins of the crystals is possible to find the presence of discontinuous sets of P-enriched bands that generally outline euhedral crystal forms; some crystals are characterized by P-enriched ghosts of relict crystals in their interior that are associated with probable undercooling and/or with an initial pulse of rapid crystal growth [8, 10]. Phenocrysts and microphenocrysts are frequently unzoned in major and minor divalent cations (Fe, Mg, Mn, Ca, Ni), but all are zoned in P. Variations in Cr and Al correlate spatially with P but are much fainter or absents, in some crystal the P-enriched bands are superimposed with small crystals of chromite (?1 ?m) aligned along the P zoning. Probably these chromites were formed by precipitation from the original Cr and Al bands. In no case was observed Ti zoning. [1] Richter D.H. et al. (1970) US Geol Surv Prof Pap 537-E, 73 p. [2] Richter D.H., Moore J.G. (1966) US Geol Surv Prof Pap 537-B, 26 p. [3] Helz R.T. (1980) Bull Volcanol 43-4, 675-701. [4] Helz R.T. et al. (1984) US Geol Surv Open File Rep 84-484, 72 p. [5] Hardee H.C. et al. (1981) Geophys Res Lett 8, 1211-1214. [6] Helz R.T., Wright T.L. (1983) US Geol Surv Open File Rep 83-326, 66 p. [7] Helz R.T. (1987) Geochem Soc Spec Pub 1, 241-258. [8] Beckett J.R. et al. (2008) LPSC abs. 1726. [9] Mccanta M.C. et al. (2008) LPSC abs. 1807. [10] Milmann-Barris M.S. et al. (2008) CMP 155, 739-765. [11] Mccanta M.C. et al. (2008) GCA 72-12, S1, A610.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25004515','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25004515"><span id="translatedtitle"><span class="hlt">Bar</span> piezoelectric ceramic transformers.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Erhart, Ji?; Pulpan, P?lpn; Rusin, Lubo</p> <p>2013-07-01</p> <p><span class="hlt">Bar</span>-shaped piezoelectric ceramic transformers (PTs) working in the longitudinal vibration mode (k31 mode) were studied. Two types of the transformer were designed--one with the electrode divided into two segments of different length, and one with the electrodes divided into three symmetrical segments. Parameters of studied transformers such as efficiency, transformation ratio, and input and output impedances were measured. An analytical model was developed for PT parameter calculation for both two- and three-segment PTs. Neither type of <span class="hlt">bar</span> PT exhibited very high efficiency (maximum 72% for three-segment PT design) at a relatively high transformation ratio (it is 4 for two-segment PT and 2 for three-segment PT at the fundamental resonance mode). The optimum resistive loads were 20 and 10 k? for two- and three-segment PT designs for the fundamental resonance, respectively, and about one order of magnitude smaller for the higher overtone (i.e., 2 k? and 500 ?, respectively). The no-load transformation ratio was less than 27 (maximum for two-segment electrode PT design). The optimum input electrode aspect ratios (0.48 for three-segment PT and 0.63 for two-segment PT) were calculated numerically under no-load conditions. PMID:25004515</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25071232','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25071232"><span id="translatedtitle">Beyond Hopkinson's <span class="hlt">bar</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pierron, F; Zhu, H; Siviour, C</p> <p>2014-08-28</p> <p>In order to perform experimental identification of high strain rate material models, engineers have only a very limited toolbox based on test procedures developed decades ago. The best example is the so-called split Hopkinson pressure <span class="hlt">bar</span> based on the <span class="hlt">bar</span> concept introduced 100 years ago by Bertram Hopkinson to measure blast pulses. The recent advent of full-field deformation measurements using imaging techniques has allowed novel approaches to be developed and exciting new testing procedures to be imagined for the first time. One can use this full-field information in conjunction with efficient numerical inverse identification tools such as the virtual fields method (VFM) to identify material parameters at high rates. The underpinning novelty is to exploit the inertial effects developed in high strain rate loading. This paper presents results from a new inertial impact test to obtain stress-strain curves at high strain rates (here, up to 3000 s(-1)). A quasi-isotropic composite specimen is equipped with a grid and images are recorded with the new HPV-X camera from Shimadzu at 5 Mfps and the SIMX16 camera from Specialised Imaging at 1 Mfps. Deformation, strain and acceleration fields are then input into the VFM to identify the stiffness parameters with unprecedented quality. PMID:25071232</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014P%26SS..104..163W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014P%26SS..104..163W"><span id="translatedtitle">Mineralogical and Raman spectroscopy studies of natural <span class="hlt">olivines</span> exposed to different planetary environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weber, I.; Böttger, U.; Pavlov, S. G.; Jessberger, E. K.; Hübers, H.-W.</p> <p>2014-12-01</p> <p>New lander missions to bodies of our solar system are coming up and thus new techniques are desirable for the in-situ investigation of planetary surface and near surface materials. During the last decade Raman spectroscopy has been developed to become an excellent laboratory tool for fast petrological and mineralogical investigation of terrestrial and extraterrestrial rocks. Consequently, Raman spectroscopy has successfully been proposed for operation on planetary surfaces. In the joint ESA and Roscosmos mission ExoMars a Raman Laser Spectrometer (RLS) will for the first time be applied in space to identify minerals and organic compounds in Martian surface rocks and soils. The present study aims to investigate the possible response of various environmental conditions to Raman spectra in preparation for the ExoMars mission, as well as other space missions in future. For our study we selected five natural <span class="hlt">olivines</span> with different forsterite (Mg2SiO4) and fayalite (Fe2SiO4) compositions. <span class="hlt">Olivine</span> as an important rock forming mineral of the Earth upper mantle and an abundant mineral in Martian meteorites is one of the key planetary mineral. The spectra were taken in various environmental conditions that include vacuum down to 10-6 mbar, 8 mbar CO2 atmosphere, and temperatures ranging between room temperature and~8 K resembling those on Mars as well as on the Moon and on asteroids. We have found that forsterite shows only small temperature-related shifts in Raman spectra at very low temperatures indicating relatively weak changes in the lattice modes. Fayalite demonstrates, in addition to temperature dependent changes in the lattice modes found for forsterite, modification of Raman spectra at low Stokes frequencies. This is an effect in the SiO4 internal modes that most probably is caused by the high amount of iron in the mineral structure, which triggers antiferromagnetic transition at low temperatures. No influence of a CO2 atmosphere on Raman spectra for the investigated rock-forming minerals has been observed at any pressure from ambient 1 <span class="hlt">bar</span> down to a few mbar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMMR22A..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMMR22A..07S"><span id="translatedtitle"><span class="hlt">Olivine</span>-Wadsleyite-Pyroxene Epitaxy: Element and Volatile Distributions at the 410km Discontinuity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smyth, J. R.; Miyajima, N.; Huss, G. R.; Hellebrand, E.; Rubie, D. C.; Frost, D. J.</p> <p>2010-12-01</p> <p>We have synthesized hydrous peridotite-composition samples at 13GPa and 1400C with co-existing coarse grains (~100 micrometer) of <span class="hlt">olivine</span>, wadsleyite, clinoenstatite, and melt in a multi-anvil press. The <span class="hlt">olivine</span> grains contain fine-scale lamellae of wadsleyite and clinoenstatite that likely resulted from small temperature fluctuations during the four-hour experiment. Major-element compositions were determined by electron microprobe and H contents by secondary ion mass spectroscopy (SIMS). The <span class="hlt">olivine</span> is about Fo93 in composition and contains about 650 ppm by weight H2O. The wadsleyite is about Fo87 in composition and contains about 1650 weight percent H2O. The clinoenstatite is about En96 in composition and about 440 ppm H2O. High resolution transmission electron microscopy of the lamellae and host show that the <span class="hlt">olivine</span> and wadsleyite share their close-packed oxygen planes so that the wadsleyite lamellae are nearly planar and perpendicular to the [1 0 0] of <span class="hlt">olivine</span>. The wadsleyite lamellae thus have their [1 0 1] and [1 0 -1] directions parallel to the [1 0 0] of <span class="hlt">olivine</span>. Additionally, a second orientation relation with the [001] of <span class="hlt">olivine</span> parallel to [100] of wadsleyite is also found as are incoherent blebs of wadsleyite in <span class="hlt">olivine</span>. The coexisting melt phase quenched to a feathery mass of mostly wadsleyite crystals. Neither a quenched glass phase nor a nominally hydrous phase was observed. The lamellae indicate that the <span class="hlt">olivine</span>-wadsleyite transformation can proceed effectively by coherent mechanisms that could potentially preserve lattice preferred orientation. The observed rapid coherent inversion from <span class="hlt">olivine</span> to wadsleyite means that a metastable preservation of <span class="hlt">olivine</span> below 410 km is unlikely under slightly hydrous conditions. The distribution of H among the nominally anhydrous phases implies that dehydration of peridotites by partial melting is inefficient so that complete dehydration of subducting slabs is unlikely. SEM-BSE image of wadsleyite (W) blebs and lamellae in <span class="hlt">olivine</span> (O).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008M%26PS...43.1241S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008M%26PS...43.1241S"><span id="translatedtitle">Petrogenetic linkages among Martian basalts: Implications based on trace element chemistry of <span class="hlt">olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shearer, C. K.; Burger, P. V.; Papike, J. J.; Borg, L. E.; Irving, A. J.; Herd, C.</p> <p>2008-10-01</p> <p>The shergottites exhibit a range of major and trace element compositions, crystallization ages, and initial Sr, Nd, Hf, and Pb isotopic compositions. To constrain the physical mechanisms by which shergottites obtain their compositional characteristics, we examined the major and trace element record preserved in <span class="hlt">olivine</span> in the more primitive shergottites. Based on such characteristics as the Mg#, V zoning, calculated DNi,Co, the <span class="hlt">olivine</span> in Y-980459 are most likely phenocrysts. Many of these same characteristics indicate that the <span class="hlt">olivines</span> in other shergottites are not in equilibrium with the adjacent melt. However, in most cases they are not xenocrystic, but additions of <span class="hlt">olivine</span> from the same basaltic system. Elephant Moraine (EET) A79001 may be an exception with the <span class="hlt">olivine</span> data suggesting that it is xenocrystic. In this case, the <span class="hlt">olivine</span> crystallized from a reduced and LREEdepleted melt and was incorporated into an oxidized and enriched basalt. Vanadium and CaO in <span class="hlt">olivine</span> appear to record the appearance of spinel and pyroxene on the liquidus of most of the shergottites. Most of the <span class="hlt">olivine</span> shergottites represent basalts produced by melting of reduced (IW to IW + 1), depleted mantle sources. <span class="hlt">Olivine</span> data indicate that many of the primary melts derived from this source had similar Ni, Co, and Mn. Shergottites such as Northwest Africa (NWA) 1110/1068 and perhaps Roberts Massif (RBT) 04261 that appear to be derived from more enriched sources have distinctly different <span class="hlt">olivine</span>. In the case of NWA 1110/1068, the <span class="hlt">olivine</span> data suggests that the enriched component was added to system prior to <span class="hlt">olivine</span> crystallization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24369634','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24369634"><span id="translatedtitle">[Study on the FTIR spectra of OH in <span class="hlt">olivines</span> from mengyin kimberlite].</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ai, Qun; Yang, Zhi-jun; Zeng, Xiang-qing; Zheng, Yun-long; Hu, Piao-ye</p> <p>2013-09-01</p> <p>The results of FTIR spectra study of OH in <span class="hlt">olivines</span> from Mengyin kimberlite show that there are more than 60 OH absorption peaks in the range of 3800-3000 cm(-1). We identified four major spectral features in the OH absorption bands of kimberlitic <span class="hlt">olivines</span>. One is with nuOH in the range of 3800-3700 cm(-1), which is caused by the vapour of the room circumstance, and can not be regarded as intrinsic or non-intrinsic nuOH of the <span class="hlt">olivines</span>. Another one is with nuOH in the range of 3710-3620 cm(-1), which belongs to three "water"-bearing minerals including serpentine, talc and Mg-bearing amphiboles, which is the non-intrinsic nuOH of the <span class="hlt">olivines</span>. There is the possibility that H in hydrous minerals mainly entered into <span class="hlt">olivines</span> during post-emplacement processes of the kimberlite magma. The third one is with nuOH in the range of 3620-3425 cm(-1), which originated from H occupying the Si-defect in the <span class="hlt">olivine</span> structure, forming humite-like defects, and/or the defects that H occupies (Mg,Fe)-depletion, which is certainly attributed to the intrinsic nuOH of the <span class="hlt">olivines</span>. In this case, H possibly entered into <span class="hlt">olivines</span> following its immersion in the high temperature and rich fluid kimberlite magma in the mantle circumstance. The last one is with nuOH in the range of 3425-3000 cm(-1). In this area, nuOH is assigned to fluid inclusions of the <span class="hlt">olivines</span>, and is the non-intrinsic nuOH of <span class="hlt">olivines</span>. Fluid inclusions can enter into the <span class="hlt">olivines</span> either during post-emplacement processes of the kimberlite magma or during the periods that <span class="hlt">olivines</span> were formed in the mantle. PMID:24369634</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70001175','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70001175"><span id="translatedtitle">Serpentinization and alteration in an <span class="hlt">olivine</span> cumulate from the Stillwater Complex, Southwestern Montana</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Page, N.J.</p> <p>1976-01-01</p> <p>Some of the <span class="hlt">olivine</span> cumulates of the Ultramafic zone of the Stillwater Complex, Montana, are progressively altered to serpentine minerals and thompsonite. Lizardite and chrysotile developed in the cumulus <span class="hlt">olivine</span> and postcumulus pyroxenes; thompsonite developed in postcumulus plagioclase. The detailed mineralogy, petrology, and chemistry indicate that <span class="hlt">olivine</span> and plagioclase react to form the alteration products, except for H2O, without changes in the bulk composition of the rocks. ?? 1976 Springer-Verlag.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015M%26PS...50.1271K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015M%26PS...50.1271K"><span id="translatedtitle">LIME silicates in amoeboid <span class="hlt">olivine</span> aggregates in carbonaceous chondrites: Indicator of nebular and asteroidal processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Komatsu, Mutsumi; Fagan, Timothy J.; Mikouchi, Takashi; Petaev, Michail I.; Zolensky, Michael E.</p> <p>2015-07-01</p> <p>MnO/FeO ratios in <span class="hlt">olivine</span> from amoeboid <span class="hlt">olivine</span> aggregates (AOAs) reflect conditions of nebular condensation and can be used in concert with matrix textures to compare metamorphic conditions in carbonaceous chondrites. LIME (low-iron, Mn-enriched) <span class="hlt">olivine</span> was identified in AOAs from Y-81020 (CO3.05), Kaba (CV~3.1), and in Y-86009 (CV3), Y-86751 (CV3), NWA 1152 (CR/CV3), but was not identified in AOAs from Efremovka (CV3.1-3.4) or Allende (CV>3.6). According to thermodynamic models of nebular condensation, LIME <span class="hlt">olivine</span> is stable at lower temperatures than Mn-poor <span class="hlt">olivine</span> and at low oxygen fugacities (dust enrichment <10× solar). Although this set of samples does not represent a single metamorphic sequence, the higher subtypes tend to have AOA <span class="hlt">olivine</span> with lower Mn/Fe, suggesting that Mn/Fe decreases during parent body metamorphism. Y-81020 has the lowest subtype and most forsteritic AOA <span class="hlt">olivine</span> (Fo>95) in our study, whereas Efremovka AOAs are slightly Fe-rich (Fo>92). AOA <span class="hlt">olivines</span> from Kaba are mostly forsteritic, but rare Fe-rich <span class="hlt">olivine</span> precipitated from an aqueous fluid. A combination of precipitation of Fe-rich <span class="hlt">olivine</span> and diffusion of Fe into primary <span class="hlt">olivine</span> grains resulted in iron-rich compositions (Fo97-59) in Allende AOAs. Variations from fine-grained, nonporous matrix toward higher porosity and coarser lath-like matrix <span class="hlt">olivine</span> can be divided into six stages represented by (1) Y-81020, Efremovka, NWA 1152; (2) Y-86751 lithology B; (3) Y-86009; (4) Kaba; (5) Y-86751 lithology A; (6) Allende. These stages are inferred to represent general degree of metamorphism, although the specific roles of thermally driven grain growth and diffusion versus aqueous dissolution and precipitation remain uncertain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMMR11A2464D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMMR11A2464D"><span id="translatedtitle">Deformation of <span class="hlt">olivine</span> single crystals under lithospheric conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Demouchy, S.; Tommasi, A.; Cordier, P.</p> <p>2012-12-01</p> <p>The rheology of mantle rocks at lithospheric temperatures (<1000°C) remains poorly constrained, in contrast to the extensive experimental data on creep of <span class="hlt">olivine</span> single crystals and polycrystalline aggregates at high temperature (T > 1200°C). Consequently, we have performed tri-axial compression experiments on oriented single crystals and polycrystalline aggregates of San Carlos <span class="hlt">olivine</span> at temperatures ranging from 800° to 1090°C. The experiments were carried out at a confining pressure of 300 MPa in a high-resolution gas-medium mechanical testing apparatus at constant strain rates ranging from 7 × 10-6 s-1 to 1 × 10-4 s-1 . Compression was applied along three different crystallographic directions: [101]c, [110]c and [011]c, to activate the several slip systems. Yield differential stresses range from 88 to 1076 MPa. To constrain hardening, stick-and-slip, or strain localization behaviors, all samples were deformed at constant displacement rate for finite strains between 4 to 23 %. Hardening was observed in all experiments and the maximum differential stress often overcame the confining pressure. EBSD mapping highlights macroscale bending of the crystalline network in three crystals. TEM observations on several samples show dislocations with [100] and [001] Burgers vectors in all samples, but dislocation arrangements vary. The results from the present study permit to refining the power-law expressing the strain rate dependence on stress and temperature for <span class="hlt">olivine</span>, allowing its application to the lithospheric mantle. Our experiments confirm that previous published high-temperature power flow laws overestimate the strength of lithospheric mantle and that the transition to low-temperature creep occurs at higher temperatures than it has previously been established.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/959669','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/959669"><span id="translatedtitle">Deformation of <span class="hlt">Olivine</span> at Mantle Pressure using D-DIA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li,L.</p> <p>2006-01-01</p> <p>Knowledge of the rheological properties of mantle materials is critical in modeling the dynamics of the Earth. The high-temperature flow law of <span class="hlt">olivine</span> defined at mantle conditions is especially important since the pressure dependence of rheology may affect our estimation of the strength of <span class="hlt">olivine</span> in the Earth's interior. In this study, steady-state high-temperature (up to 1473 K) deformation experiments of polycrystalline <span class="hlt">olivine</span> (average grain size ? 10 ?m) at pressure up to 9.6 GPa, were conducted using a Deformation-DIA (D-DIA) high-pressure apparatus and synchrotron X-ray radiation. The oxygen fugacity (fo2) during the runs was in-between the iron-wustite and the Ni/NiO buffers' fo2. The water content of the polycrystalline samples was generally about 150 to 200 wt. ppm but was as low as 35 wt ppm. Typically, 30 % strain was generated during the uniaxial compression. Sample lengths during the deformation process as well as the differential stresses were monitored in situ by X-ray radiography and diffraction, respectively. The strain rate was derived with an accuracy of 10?6 s?1. Differential stress was measured at constant strain rate (?10?5 s?1) using a multi-element solid-state detector combined with a conical slit. Recovered specimens were investigated by optical and transmission electron microscopy (TEM). TEM shows that dislocation glide was the dominant deformation mechanism throughout the experiment. Evidence of dislocation climb and cross-slip as active mechanisms are also reported. Deformation data show little or no dependence of the dislocation creep flow with pressure, yielding to an activation volume V* of 0 {+-} 5 cm3/mol. These new data are consistent with the high-temperature rheological laws at lower pressures, as reported previously.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.V51A2169W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.V51A2169W"><span id="translatedtitle">Argon Diffusion in Shocked Pyroxene, Feldspar, and <span class="hlt">Olivine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weirich, J.; Isachsen, C. E.; Johnson, J. R.; Swindle, T.</p> <p>2010-12-01</p> <p>Background: The diffusion rate of argon (Ar) in unshocked feldspar has been well studied, but studies on pyroxene and <span class="hlt">olivine</span> are limited or non-existent. Likewise, the effects of shock on these mineral groups is also limited or non-existent. Understanding how shock affects these mineral groups is important for determining the thermal history of shocked meteorites and collisional impact craters. We have analyzed the Ar diffusion rate of an albitite and a pyroxenite at various experimental shock pressures up to ~60GPa, unshocked high-Ca pyroxene, and an <span class="hlt">olivine</span> mineral separate from the Springwater meteorite. A previous study of shocked feldspar has shown that Ar diffusion in plagioclase (An67) is unaffected by experimental shock [1]. Re-reduction of data from another study [2] suggests naturally shocked K-rich feldspar is affected, though experimentally shocked oligoclase feldspar (An10-30) is not affected. However, previous shock experiments on feldspar were performed with low temperature resolution and only a single extraction at each temperature. This makes determining the diffusion parameters difficult because the presence of multiple grain sizes can compromise the data. By performing our experiments with a higher temperature resolution and with two extractions at each temperature, we can attain higher quality and more reliable data. The effects of shock on pyroxene and <span class="hlt">olivine</span> have never been studied. Results: We have found that experimental shock undoubtedly raises the diffusivity of albite (Ab97), and lowers the activation energy required for diffusion. Comparison with previous data indicates that the Ca content may be controlling the response to shock. Pyroxene seems to be somewhat variable regardless of shock pressure, even within the same sample. Shock may have an effect on the diffusion rate of pyroxene, but given the variability it is difficult to delineate. The range of pyroxene diffusion rates is similar to previous studies. <span class="hlt">Olivine</span> is found to have a low activation energy, somewhat similar to that of unshocked alkali feldspar, despite remaining a high temperature mineral due to a much lower frequency factor. References: [1]Jessberger E. K. and Ostertag R. (1982). GCA 46:1465-1471. [2]Stephan T. and Jessberger E. K. (1992). GCA 56:1591-1605.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeCoA.122..280G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeCoA.122..280G"><span id="translatedtitle">Chromium valences in ureilite <span class="hlt">olivine</span> and implications for ureilite petrogenesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goodrich, C. A.; Sutton, S. R.; Wirick, S.; Jercinovic, M. J.</p> <p>2013-12-01</p> <p>Ureilites are a group of ultramafic achondrites commonly thought to be residues of partial melting on a carbon-rich asteroid. They show a large variation in FeO content (<span class="hlt">olivine</span> Fo values ranging from ∼74 to 95) that cannot be due to igneous fractionation and suggests instead variation in oxidation state. The presence of chromite in only a few of the most ferroan (Fo 75-76) samples appears to support such a model. MicroXANES analyses were used in this study to determine the valence states of Cr (previously unknown) in <span class="hlt">olivine</span> cores of 11 main group ureilites. The goal of this work was to use a method that is independent of Fo to determine the oxidation conditions under which ureilites formed, in order to evaluate whether the ureilite FeO-variation is correlated with oxidation state, and whether it is nebular or planetary in origin. Two of the analyzed samples, LEW 88774 (Fo 74.2) and NWA 766 (Fo 76.7) contain primary chromite; two others, LAP 03587 (Fo 74.4) and CMS 04048 (Fo 76.2) contain sub-micrometer-sized exsolutions of chromite + Ca-rich pyroxene in <span class="hlt">olivine</span>; and one, EET 96328 (Fo 85.2) contains an unusual chromite grain of uncertain origin. No chromite has been observed in the remaining six samples (Fo 77.4-92.3). Chromium in <span class="hlt">olivine</span> in all eleven samples was found to be dominated by the divalent species, with valences ranging from 2.10 ± 0.02 (1σ) to 2.46 ± 0.04. The non-chromite-bearing ureilites have the most reduced Cr, with a weighted mean valence of 2.12 ± 0.01, i.e., Cr2+/Cr3+ = 7.33. All low-Fo chromite-bearing ureilites have more oxidized Cr, with valences ranging from 2.22 ± 0.03 to 2.46 ± 0.04. EET 96328, whose chromite grain we interpret as a late-crystallizing phase, yielded a reduced Cr valence of 2.15 ± 0.07, similar to the non-chromite-bearing samples. Based on the measured Cr valences, magmatic (1200-1300 °C) oxygen fugacities (fO2) of the non-chromite-bearing samples were estimated to be in the range IW-1.9 to IW-2.8 (assuming basaltic melt composition), consistent with fO2 values obtained by assuming <span class="hlt">olivine</span>-silica-iron metal (OSI) equilibrium. For the primary chromite-bearing-ureilites, the corresponding fO2 were estimated (again, assuming basaltic melt composition) to be ∼IW to IW+1.0, i.e., several orders of magnitude more oxidizing than the conditions estimated for the chromite-free ureilites. In terms of Fo and Cr valence properties, ureilites appear to form two groups rather than a single “Cr-valence (or fO2) vs. Fo” trend. The chromite-bearing ureilites show little variation in Fo (∼74-76) but significant variation in Cr valence, while the non-chromite-bearing ureilites show significant variation in Fo (∼77-95) and little variation in Cr valence. These groups are unrelated to petrologic type (i.e., <span class="hlt">olivine</span>-pigeonite, <span class="hlt">olivine</span>-orthopyroxene, or augite-bearing). The chromite-bearing ureilites also have lower contents of Cr in <span class="hlt">olivine</span> than most non-chromite-bearing ureilites, consistent with predictions based on Cr <span class="hlt">olivine</span>/melt partitioning in spinel saturated vs. non-spinel-saturated systems. Under the assumption that at magmatic temperatures graphite-gas equilibria controlled fO2 at all depths on the ureilite parent body, we conclude: (1) that ureilite precursor materials having the Fo and Cr valence properties now observed in ureilites are unlikely to have been preserved during planetary processing; and (2) that the Fo and Cr valence properties now observed in ureilites are consistent with having been established by high-temperature carbon redox control over a range of depths on a plausible-sized ureilite parent body. The apparent limit on ureilite Fo values around 74-76 suggests that the precursor material(s) had bulk mg# ⩾ that of LL chondrites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.V21A1966F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.V21A1966F"><span id="translatedtitle">Experimental constraints of the <span class="hlt">olivine</span> crystals compaction in cumulus layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Forien, M.; Bagdassarov, N.; Schmidt, M. W.</p> <p>2009-12-01</p> <p>The layered intrusions are the result of magma crystallization and differentiation in a form of lateral structures, which are often observed in magmatic chambers. They are markers of processes occurring during a prolonged cooling stage (several tens of thousands years for bodies 1 km in size). There is no unique explication for the mechanism of layering during the intrusion formation. The most plausible mechanism proposed to explain the observed layering includes the coupled crystal settling and residual liquid advection. In the layers containing a large crystal fraction (> 66 vol%) and a small percentage of the residual liquid, the compaction mechanism and the decrease of cumulate layer porosity due to the diffusion adjustment of grain boundaries could effectively occur. In this study, the compaction mechanisms of crystals settling in magma chambers have been modelled with the use of a high temperature centrifuge. The suspensions of <span class="hlt">olivine</span> crystals and a basaltic melt (33 vol% and 67 vol%, respectively) were centrifuged at the melting temperature of basalt (temperature range of 1270-1280°C). The experiments were conducted at 200-1500 g under a pressure between 0.8-1.1 GPa. During centrifugation run <span class="hlt">olivine</span> grains are compacted because of the x-time enhanced centrifugation force which is equivalent to x-time larger volume of crystals compacting from above. After crystals have reached a maximum compaction concentration due to this accelerated piling from above, their locations and porosity in cumulates change under the influence of the solution - recrystallisation process. The concentration of crystals in a cumulate layer increases much slower than during their sedimentation. The solution-precipitation and recrystallisation process is a diffusion type mechanism of compaction and has not been addressed experimentally before. Evidences of the precipitation - recrystallisation process of <span class="hlt">olivine</span> grains in centrifuged samples with TEM analyses are revealed. In fact, knowing that Ca is characteristic only for MORB-melt, the first feature is the presence of Ca at the interface of two adjacent Ol-grains even when the melt phase is escaped. Another evidence of the diffusion compaction is the presence of some small melt inclusions at the growing Ol-boundaries of compacting Ol-grains. Finally, the precipitation - recrystallisation process of <span class="hlt">olivine</span> grains during the cumulus compaction stems from the observation that the new boundary between two Ol-grains is distinct and not fully crystallized as the interior of grains. This indicates some MORB melt elements (for example, enrichment in Ca) prevent to recrystallize Ol in a fully crystalline structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007Icar..188..246M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007Icar..188..246M"><span id="translatedtitle">Shock-wave heating model for <span class="hlt">chondrule</span> formation: Hydrodynamic simulation of molten droplets exposed to gas flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miura, Hitoshi; Nakamoto, Taishi</p> <p>2007-05-01</p> <p>Millimeter-sized, spherical silicate grains abundant in chondritic meteorites, which are called as <span class="hlt">chondrules</span>, are considered to be a strong evidence of the melting event of the dust particles in the protoplanetary disk. One of the most plausible scenarios is that the <span class="hlt">chondrule</span> precursor dust particles are heated and melt in the high-velocity gas flow (shock-wave heating model). We developed the non-linear, time-dependent, and three-dimensional hydrodynamic simulation code for analyzing the dynamics of molten droplets exposed to the gas flow. We confirmed that our simulation results showed a good agreement in a linear regime with the linear solution analytically derived by Sekyia et al. [Sekyia, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728]. We found that the non-linear terms in the hydrodynamical equations neglected by Sekiya et al. [Sekiya, M., Uesugi, M., Nakamoto, T., 2003. Prog. Theor. Phys. 109, 717-728] can cause the cavitation by producing negative pressure in the droplets. We discussed that the fragmentation through the cavitation is a new mechanism to determine the upper limit of <span class="hlt">chondrule</span> sizes. We also succeeded to reproduce the fragmentation of droplets when the gas ram pressure is stronger than the effect of the surface tension. Finally, we compared the deformation of droplets in the shock-wave heating with the measured data of <span class="hlt">chondrules</span> and suggested the importance of other effects to deform droplets, for example, the rotation of droplets. We believe that our new code is a very powerful tool to investigate the hydrodynamics of molten droplets in the framework of the shock-wave heating model and has many potentials to be applied to various problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050162228','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050162228"><span id="translatedtitle">The Iodine-Xenon System in Outer and Inner Portions of <span class="hlt">Chondrules</span> from the Unnamed Antarctic LL3 Chondrite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Meshik, A. P.; Pravdivtseva, O. V.; Hohenberg, C. M.; Amelin, Y.</p> <p>2004-01-01</p> <p>Alteration processes may affect I-Xe system in unequilibrated ordinary chondrites. It was shown that at the edges, where a contribution is made by matrix material around the rim, *Xe-129/Xe-128 values are generally lower (later apparent ages) than in the main <span class="hlt">chondrule</span> mass. In this work we attempted to investigate whether thermal metamorphism can affect the I-Xe system in LL3 chondrites which did not experienced aqueous alteration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.V53C4885F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.V53C4885F"><span id="translatedtitle">Mantle Origin of <span class="hlt">Olivine</span>-rich Troctolites in a Rift Environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faul, U.; Garapic, G.; Michibayashi, K.</p> <p>2014-12-01</p> <p><span class="hlt">Olivine</span>-rich troctolites from Krivaja-Konjuh massif in the Dinarides (Bosnia and Herzegovina) represent a unique natural laboratory to study melt segregation and retention in originally fertile rift-related mantle rocks. Petrographic and chemical analyses of coexisting minerals (<span class="hlt">olivine</span> and interstitial clinopyroxene, spinel and plagioclase) show that <span class="hlt">olivine</span> and spinel are of mantle origin, and interstitial clinopyroxene and plagioclase are products of crystallization of trapped melt. Geochemical and microstructural observations (dissolution of pyroxene) indicate that this trapped melt started off at larger depth and that it was silica undersaturated when it reached the plagioclase stability field. The original mantle <span class="hlt">olivine</span> remained and texturally equilibrated with the melt, which is evident from the high Ni content and euhedral crystal habit in thin sections. This suggests that the melt that crystallized the interstitial phases, clinopyroxene and plagioclase, was saturated in <span class="hlt">olivine</span> and probably similar to MORB-type melt. The interstitial phases show no sign of deformation. A mantle origin of <span class="hlt">olivine</span> is corroborated by EBSD data that show a progressive misorientation across individual <span class="hlt">olivine</span> grains due to previous episodes of deformation within the mantle. By contrast, grains originating from cumulate crystallization should show little internal deformation. Therefore we suggest that <span class="hlt">olivine</span>-rich troctolites are not crystallization products, but rather products of reaction of melt with the lherzolitic mantle. The evidence of trapped melt in those rocks provides a new insight into the crust-mantle transition at slow spreading ridges and continental rifts where <span class="hlt">olivine</span>-rich troctolites have been observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70014210','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70014210"><span id="translatedtitle">Relation of the spectroscopic reflectance of <span class="hlt">olivine</span> to mineral chemistry and some remote sensing implications.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>King, T.V.V.; Ridley, W.I.</p> <p>1987-01-01</p> <p>Using high-resolution visible and near-infrared diffuse spectral reflectance, systematically investigates apparent wavelength shifts as a function of mineral chemistry in the Fe/Mg <span class="hlt">olivine</span> series from Fo11 to Fo91. The study also shows that trace amounts of nickel can be spectrally detected in the <span class="hlt">olivine</span> structure. Significant spectral variation as a function of grain size is also demonstrated, adding a further complication to the interpretation of remotely sensed data from <span class="hlt">olivine</span>-rich surfaces. Some permutations of Fe-Mg-Ni relations in <span class="hlt">olivines</span> are discussed as they apply to the interpretation of asteroid surfaces and other extraterrestrial bodies. -from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EPJAP..23...55B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EPJAP..23...55B"><span id="translatedtitle">Bus <span class="hlt">bar</span> copper losses computation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Besacier, M.; Guichon, J. M.; Schanen, J. L.; Roudet, J.</p> <p>2003-07-01</p> <p>This paper describes how to forecast copper losses in a bus <span class="hlt">bar</span>, composed of thin copper layers and several access points. The main difficulties are, first to determine current path and associated electrical characteristics, and second to propose electrical equivalent circuits of the bus <span class="hlt">bar</span>, allowing copper losses representation. For bus <span class="hlt">bar</span> electrical modeling, the choice of an integral method, PEEC method, is justified. Then, several equivalent circuits are proposed and their validity for copper losses computation discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013M%26PS...48.1359B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013M%26PS...48.1359B"><span id="translatedtitle">Magmatic history and parental melt composition of <span class="hlt">olivine</span>-phyric shergottite LAR 06319: Importance of magmatic degassing and <span class="hlt">olivine</span> antecrysts in Martian magmatism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balta, J. Brian; Sanborn, Matthew; McSween, Harry Y.; Wadhwa, Meenakshi</p> <p>2013-08-01</p> <p>Several <span class="hlt">olivine</span>-phyric shergottites contain enough <span class="hlt">olivine</span> that they could conceivably represent the products of closed-system crystallization of primary melts derived from partial melting of the Martian mantle. Larkman Nunatak (LAR) 06319 has been suggested to represent a close approach to a Martian primary liquid composition based on approximate equilibrium between its <span class="hlt">olivine</span> and groundmass. To better understand the <span class="hlt">olivine</span>-melt relationship and the evolution of this meteorite, we report the results of new petrographic and chemical analyses. We find that <span class="hlt">olivine</span> megacryst cores are generally not in equilibrium with the groundmass, but rather have been homogenized by diffusion to Mg# 72. We have identified two unique grain types: an <span class="hlt">olivine</span> glomerocryst and an <span class="hlt">olivine</span> grain preserving a primary magmatic boundary that constrains the time scale of eruption to be on the order of hours. We also report the presence of trace oxide phases and phosphate compositions that suggest that the melt contained approximately 1.1% H2O and lost volatiles during cooling, also associated with an increase in oxygen fugacity upon degassing. We additionally report in situ rare earth element measurements of the various mineral phases in LAR 06319. Based on these reported trace element abundances, we estimate the oxygen fugacity in the LAR 06319 parent melt early in its crystallization sequence (i.e., at the time of crystallization of the low-Ca and high-Ca pyroxenes), the rare earth element composition of the parent melt, and those of melts in equilibrium with later formed phases. We suggest that LAR 06319 represents the product of closed-system crystallization within a shallow magma chamber, with additional <span class="hlt">olivine</span> accumulated from a cumulate pile. We infer that the <span class="hlt">olivine</span> megacrysts are antecrysts, derived from a single magma chamber, but not directly related to the host magma, and suggest that mixing of antecrysts within magma chambers may be a common process in Martian magmatic systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015HiA....16..373M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015HiA....16..373M"><span id="translatedtitle"><span class="hlt">Bars</span> in a cosmological context</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martig, Marie; Kraljic, Katarina; Bournaud, Frédéric</p> <p>2015-03-01</p> <p>We study the properties of <span class="hlt">bars</span> in a series of zoom cosmological simulations (Martig et al. 2012, Kraljic et al. 2012). We find that <span class="hlt">bars</span> are almost absent from galaxies at z>1, and if they form they tend to be quickly destroyed by mergers and instabilities. On the contrary, at z<1 <span class="hlt">bars</span> are long-lived, and the fraction of <span class="hlt">barred</span> galaxies rises steadily. <span class="hlt">Bars</span> are eventually found in ~ 80% of z=0 spiral galaxies. This redshift evolution is quantitatively consistent with existing data from the COSMOS survey (Sheth et al. 2008), although the detectability of <span class="hlt">bars</span> is presently limited to z<0.8 because of band-shifting and resolution effects. We predict later <span class="hlt">bar</span> formation in lower-mass galaxies, also in agreement with existing data (e.g., Sheth et al. 2012). We actually find that the characteristic epoch of <span class="hlt">bar</span> formation is the epoch of massive thin disk formation, corresponding to the transition between an early violent phase at z > 1 and a later secular phase. <span class="hlt">Bar</span> formation thus traces the emergence of the disk-dominated morphology of today's spirals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840008384','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840008384"><span id="translatedtitle">Ladder supported ring <span class="hlt">bar</span> circuit</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kosmahl, H. G. (Inventor)</p> <p>1983-01-01</p> <p>An improved slow wave circuit especially useful in backward wave oscillators includes a slow wave circuit in a waveguide. The slow wave circuit is comprised of rings disposed between and attached to respective stubs. The stubs are attached to opposing sidewalls of the waveguide. To the end that opposed, interacting magnetic fields will be established to provide a very high coupling impedance for the slow wave structure, axially orientated <span class="hlt">bars</span> are connected between rings in alternate spaces and adjacent to the attachment points of stubs. Similarly, axial <span class="hlt">bars</span> are connected between rings in the spaces which do not include <span class="hlt">bars</span> and at points adjacent to the attachment of <span class="hlt">bars</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050169967','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050169967"><span id="translatedtitle">The Planetesimal Bow Shock Model for <span class="hlt">Chondrule</span> Formation: More Detailed Simulations in the Near Vicinity of the Planetesimal</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hood, Lon L.; Ciesla, Fred J.</p> <p>2005-01-01</p> <p>Gas dynamic shock waves in a low temperature nebula have been considered to be a leading candidate mechanism for providing the repetitive, short-duration heating events that are believed to have been responsible for the formation of <span class="hlt">chondrules</span> in chondrites. It has been found, for example, that shocks with Mach numbers greater than 4 or 5 would be capable of rapidly melting 0.1-1 mm sized silicate particles as required by meteoritic data. Near the nebula midplane where chondrite parent bodies are believed to have formed, possible energy sources for generating multiple shocks include mass concentrations in a gravitationally unstable nebula, tidal interactions of proto-Jupiter with the nebula, and bow waves upstream of planetesimals scattered gravitationally into eccentric orbits by proto- Jupiter. In a recent study, we have found that <span class="hlt">chondrule</span> precursors that are melted following passage through a planetesimal bow shock would likely cool at rates that are too rapid to be consistent with meteoritic evidence. However, that study was limited to the bowshock exterior to about 1.5 planetesimal radii (measured perpendicular to the symmetry axis) to avoid complications interior to this distance where large pressure gradients and lateral flow occur as the gas flows around the planetesimal. In this paper, we reconsider the planetesimal bow shock model and report more detailed numerical simulations of <span class="hlt">chondrule</span> precursor heating, cooling, and dynamical histories in the near vicinity of a representative planetesimal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19940007634&hterms=sasa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsasa','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19940007634&hterms=sasa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsasa"><span id="translatedtitle">SXRF determination of trace elements in <span class="hlt">c