Science.gov

Sample records for unequilibrated ordinary chondrites

  1. Thermoluminescence Sensitivity and Thermal History of Unequilibrated Ordinary Chondrites: Review and Update

    NASA Technical Reports Server (NTRS)

    Benoit, P. H.; Ninagawa, K.; Sears, D. W. G.

    2000-01-01

    We report on the induced thermoluminescence (TL) data for 102 unequilibrated ordinary chondrites. We discuss these data in terms of pairing, weathering, and parent body thermal history. We identify ten possible meteorites of petrologic types 3.0-3.1.

  2. Na, K-Rich Rim Around a Chondrule in Unequilibrated Ordinary Chondrite Lew 86018 (L3.1)

    NASA Technical Reports Server (NTRS)

    Mishra, R. K.; Simon, J. I.; Ross, D. K.; Needham, A. W.; Messenger, S.; Keller, L. P.; Han, J.; Marhas, K. K.

    2015-01-01

    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 olivine, and magnetites in their matrices and occasionally in chondrules. 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.

  3. Aqueous Alteration and Hydrogen Generation on Parent Bodies of Unequilibrated Ordinary Chondrites: Thermodynamic Modeling for the Semarkona Composition

    NASA Technical Reports Server (NTRS)

    Zolotov, M. Y.; Mironenko, M. V.; Shock, E. L.

    2005-01-01

    Ordinary chondrites are the most abundant class of meteorites that could represent rocky parts of solar system bodies. However, even the most primitive unequilibrated ordinary chondrites (UOC) reveal signs of mild alteration that affected the matrix and peripheral zones of chondrules. Major chemical changes include oxidation of kamacite, alteration of glass, removal of alkalis, Al, and Si from chondrules, and formation of phases enriched in halogens, alkalis, and hydrogen. Secondary mineralogical changes include formation of magnetite, ferrous olivine, fayalite, pentlandite, awaruite, smectites, phosphates, carbonates, and carbides. Aqueous alteration is consistent with the oxygen isotope data for magnetite. The presence of secondary magnetite, Ni-rich metal alloys, and ferrous silicates in UOC implies that H2O was the oxidizing agent. However, oxidation by H2O means that H2 is produced in each oxidative pathway. In turn, production of H2, and its redistribution and possible escape should have affected total pressure, as well as the oxidation state of gas, aqueous and mineral phases in the parent body. Here we use equilibrium thermodynamic modeling to explore water-rock reactions in UOC. The chemical composition of gas, aqueous, and mineral phases is considered.

  4. Fayalite-silica association in unequilibrated ordinary chondrites: Evidence for aqueous alteration on a parent body

    NASA Technical Reports Server (NTRS)

    Wasson, John T.; Krot, Alexander N

    1994-01-01

    We report ten occurrences of high-fayalite (Fa56-99 mol%; four with Fa greater than 82 mol%) olivine in association with silica in type-3 ordinary chondrites. Pyroxene with high Fs contents is much less common; Fs contents do not exceed 66 mol%, and most maxima are less than 50 mol%. In those cases where the amount of fayalite is minor relative to that of silica, the fayalite forms a layer on the silica, and shows textural evidence of formation by reaction of silica with oxidized Fe; the latter seems to have resulted from reaction of metallic Fe-Ni with an oxidant, most likely H2O vapor. The fayalite is generally in contact with pyroxene (and, in one case, olivine) having a much lower Fe/(Fe + Mg) ratios, indicating that lattice diffusion has been minimal. Formation of fayalite from SiO2 explains the low Mg content of this olivine; the Mg was sequestered inside the lattices of mafic minerals and was thus inaccessible. In contrast, the moderately high Mn contents of the fayalite indicate that an appreciable fraction of the Mn in the precursor assemblage was accessible; it was probably sited in the matrix in the form of tiny, poorly crystallized oxide grains produced by nebular condensation at temperatures too low to permit diffusion into forsterite or enstatite. The reaction of SiO2 with FeO produced by oxidation (during metamorphism) of Fe-Ni can also account for fayalitic olivine associated with SiO2 microspherules in the fine-grained matrices of type-3 ordinary chondrites and, because matrix is SiO2 normative, for other occurrences of fayalite in matrix. The presence of Mn in the fayalitic rims on the olivine of carbonaceous chondrites does not require a nebular sign.

  5. Compositions and textures of relic forsterite in carbonaceous and unequilibrated ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Steele, I. M.

    1986-01-01

    The compositions and textures of olivines in equilibrated ordinary chondrites, C1, C2, and C3 meteorites are described. The olivines are classified by color into blue, red, or dark olivines. The characteristic features of blue olivines are examined. It is observed that the texture of the olivine: (1) forms cores in single olivine grains; (2) shows subhedral to euhedral boundaries against rim olivines; (3) rarely contains inclusions; (4) has embayments containing olivines similar to that of the rim; and (5) occurs within chondrules. The mode of formation for blue olivines, the relation between blue olivine and high temperature compounds, and modifications in the features of blue olivines are analyzed. It is noted that the olivine is a product of condensation, has been modified by additions of olivine formed from a liquid, and that these olivines represent relic grains that are similar to olivines found in cosmic particles and in cores of some deep sea particles.

  6. Rock magnetic properties of dusty olivine: a potential carrier of pre-accretionary remanence in unequilibrated ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Lappe, S. C. L. L.; Harrison, R. J.; Feinberg, J. M.

    2012-04-01

    The mechanism of chondrule formation is an important outstanding question in cosmochemistry. Magnetic signals recorded by Fe-Ni nanoparticles in chondrules could carry clues to their origin. Recently, research in this area has focused on 'dusty olivine' grains within ordinary chondrites as potential carriers of pre-accretionary remanence. Dusty olivine is characterised by the presence of sub-micron Fe-Ni inclusions within the olivine host. These metal particles form via subsolidus reduction of the olivine during chondrule formation and are thought to be protected from subsequent chemical and thermal alteration by the host olivine. Three sets of synthetic dusty olivines have been produced, using natural olivine (average Ni-content of 0.3 wt%), synthetic Ni-containing olivine (0.1wt% Ni) and synthetic Ni-free olivine 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.

  7. Accretionary dark rims in unequilibrated chondrites

    NASA Astrophysics Data System (ADS)

    King, T. V. V.; King, E. A.

    1981-12-01

    Textural and qualitative EDX investigations of dark-rimmed particles in six low petrologic type chondrites indicate that the rims accreted on host particles over a wide range of temperatures prior to initial accumulation and lithification of the meteorites in which the rimmed particles are now contained. Many dark rims are enriched in moderately volatile trace elements such as Na, Cl, P, and K, relative to the host particles and matrix. The range of physical/chemical environments associated with hypervelocity impacts may have offered the setting for the formation of dark-rimmed particles early in solar system history.

  8. Accretionary dark rims in unequilibrated chondrites

    NASA Technical Reports Server (NTRS)

    King, T. V. V.; King, E. A.

    1981-01-01

    Textural and qualitative EDX investigations of dark-rimmed particles in six low petrologic type chondrites indicate that the rims accreted on host particles over a wide range of temperatures prior to initial accumulation and lithification of the meteorites in which the rimmed particles are now contained. Many dark rims are enriched in moderately volatile trace elements such as Na, Cl, P, and K, relative to the host particles and matrix. The range of physical/chemical environments associated with hypervelocity impacts may have offered the setting for the formation of dark-rimmed particles early in solar system history.

  9. Roosevelt County 075: A petrologic chemical and isotopic study of the most unequilibrated known H chondrite

    NASA Technical Reports Server (NTRS)

    Mccoy, T. J.; Keil, K.; Ash, R. D.; Morse, A. D.; Pillinger, C. T.; Wieler, R.; Mayeda, T. K.; Clayton, R. N.; Benoit, P. H.; Sears, D. W. G.

    1993-01-01

    Roosevelt County (RC) 075 was recovered in 1990 as a single 258-gram stone. Classification of this meteorite is complicated by its highly unequilibrated nature and its severe terrestrial weathering, but we favor H classification. This is supported by O isotopes and estimates of the original Fe, Ni metal content. The O isotopic composition is similar to that of a number of reduced ordinary chondrites (e.g., Cerro los Calvos, Willaroy), although RC 075 exhibits no evidence of reduced mineral compositions. Chondrule diameters are consistent with classification as an L chondrite, but large uncertainties in chondrule diameters of RC 075 and poorly constrained means of H, L and LL chondrites prevent use of this parameter for reliable classification. Other parameters are compromised by severe weathering (e.g., siderophile element abundances) or unsuitable for discrimination between unequilibrated H, L and LL chondrites (e.g., Co in kamacite delta C-13). Petrologic subtype 3.2 +/- 0.1 is suggested by the degree of olivine heterogeneity, the compositions of chondrule olivines, the thermoluminescence sensitivity, the abundances and types of chondrules mapped on cathodoluminescence mosaics, and the amount of presolar SiC. The meteorite is very weakly shocked (S2), with some chondrules essentially unshocked and, thus, is classified as an H3.2(S2) chondrite. Weathering is evident by a LREE enrichment due to clay contamination, reduced levels of many siderophile elements, the almost total loss of Fe, Ni metal and troilite, and the reduced concentrations of noble gases. Some components of the meteorite (e.g., type IA chondrules, SiC) appear to preserve their nebular states, with little modification from thermal metamorphism. We conclude that RC 075 is the most equilibrated H chondrite yet recovered and may provide additional insights into the origin of primitive materials in the solar nebula.

  10. Ordinary chondritic micrometeorites from the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Prasad, M. Shyam; Rudraswami, N. G.; de Araujo, Agnelo; Babu, E. V. S. S. K.; Vijaya Kumar, T.

    2015-06-01

    Extraterrestrial particulate materials on the Earth can originate in the form of collisional debris from the asteroid belt, cometary material, or as meteoroid ablation spherules. Signatures that link them to their parent bodies become obliterated if the frictional heating is severe during atmospheric entry. We investigated 481 micrometeorites isolated from ~300 kg of deep sea sediment, out of which 15 spherules appear to have retained signatures of their provenance, based on their textures, bulk chemical compositions, and relict grain compositions. Seven of these 15 spherules contain chromite grains whose compositions help in distinguishing subgroups within the ordinary chondrite sources. There are seven other spherules which comprise either entirely of dusty olivines or contain dusty olivines as relict grains. Two of these spherules appear to be chondrules from an unequilibrated ordinary chondrite. In addition, a porphyritic olivine pyroxene (POP) chondrule-like spherule is also recovered. The bulk chemical composition of all the spherules, in combination with trace elements, the chromite composition, and presence of dusty olivines suggest an ordinary chondritic source. These micrometeorites have undergone minimal frictional heating during their passage through the atmosphere and have retained these features. These micrometeorites therefore also imply there is a significant contribution from ordinary chondritic sources to the micrometeorite flux on the Earth.

  11. Composition of the metal phases in ordinary chondrites - Implications regarding classification and metamorphism

    NASA Technical Reports Server (NTRS)

    Afiattalab, F.; Wasson, J. T.

    1980-01-01

    The paper examines the composition of metal phases and metamorphism in ordinary chondrites. It is shown that below 550 C increasing Co decreases the equilibrium kamacite Ni concentration of an alpha to gamma system, and that the equilibrated L chondrites have kamacite and taenite Co concentrations in the L-group range. Metal-phase studies of petrologic type-3 ordinary chondrites with highly unequilibrated silicates showed a wide range in the degree of matrix kamacite equilibration; in the three most unequilibrated chondrites most taenite is clear, and the high Ni content shows that metamorphic temperatures were lower than 400 C in these meteorites.

  12. Si-rich Fe-Ni grains in highly unequilibrated chondrites

    NASA Technical Reports Server (NTRS)

    Rambaldi, E. R.; Sears, D. W.; Wasson, J. T.

    1980-01-01

    Consideration is given to the Si contents of Fe-Ni grains in highly unequilibrated chondrites, which have undergone little metamorphosis and thus best preserve the record of processes in the solar nebula. Electron microprobe determinations of silicon content in grains of the Bishunpur chondrite are presented for the six Si-bearing Fe-Ni grains for which data could be obtained, five of which were found to be embedded in olivine chondrules. In addition, all grains are found to be Cr-rich, with Cr increased in concentration towards the grain edge, and to be encased in FeS shells which evidently preserved the Si that entered the FeNi at higher temperatures. A mechanism for the production of Si-bearing metal during the condensation of the cooling solar nebula is proposed which considers the metal to have condensed heterogeneously while the mafic silicates condensed homogeneously with amounts of required undercooling in the low-pressure regions where ordinary and carbonaceous chondrites formed, resulting in Si mole fractions of 0.003 at nebular pressures less than 0.000001 atm.

  13. 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.

  14. Actinide abundances in ordinary chondrites

    USGS Publications Warehouse

    Hagee, B.; Bernatowicz, T.J.; Podosek, F.A.; Johnson, M.L.; Burnett, D.S.; Tatsumoto, M.

    1990-01-01

    Measurements of 244Pu fission Xe, U, Th, and light REE (LREE) abundances, along with modal petrographic determinations of phosphate abundances, were carried out on equilibrated ordinary chondrites in order to define better the solar system Pu abundance and to determine the degree of variation of actinide and LREE abundances. Our data permit comparison of the directly measured Pu/ U ratio with that determined indirectly as (Pu/Nd) ?? (Nd/U) assuming that Pu behaves chemically as a LREE. Except for Guaren??a, and perhaps H chondrites in general, Pu concentrations are similar to that determined previously for St. Se??verin, although less precise because of higher trapped Xe contents. Trapped 130Xe 136Xe ratios appear to vary from meteorite to meteorite, but, relative to AVCC, all are similar in the sense of having less of the interstellar heavy Xe found in carbonaceous chondrite acid residues. The Pu/U and Pu/Nd ratios are consistent with previous data for St. Se??verin, but both tend to be slightly higher than those inferred from previous data on Angra dos Reis. Although significant variations exist, the distribution of our Th/U ratios, along with other precise isotope dilution data for ordinary chondrites, is rather symmetric about the CI chondrite value; however, actinide/(LREE) ratios are systematically lower than the CI value. Variations in actinide or LREE absolute and relative abundances are interpreted as reflecting differences in the proportions and/or compositions of more primitive components (chondrules and CAI materials?) incorporated into different regions of the ordinary chondrite parent bodies. The observed variations of Th/U, Nd/U, or Ce/U suggest that measurements of Pu/U on any single equilibrated ordinary chondrite specimen, such as St. Se??verin, should statistically be within ??20-30% of the average solar system value, although it is also clear that anomalous samples exist. ?? 1990.

  15. Incompletely compacted equilibrated ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Sasso, M. R.; Macke, R. J.; Boesenberg, J. S.; Britt, D. T.; Rivers, M. L.; Ebel, D. S.; Friedrich, J. M.

    2009-12-01

    We document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high-resolution synchrotron X-ray microtomography (µCT) and helium pycnometry. We found total porosities ranging from ~10 to 20% within these chondrites, and with µCT we show that up to 64% of the void space is located within intergranular voids within the rock. Given the low (S1-S2) shock stages of the samples and the large voids between mineral grains, we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history. With Fe metal and FeS metal abundances and grain size distributions, we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism. These materials were not “fluffed” on their parent body by impact-related regolith gardening or events caused by seismic vibrations. Samples of all three chemical types of ordinary chondrites (LL, L, H) are represented in this study and we conclude that incomplete compaction is common within the asteroid belt.

  16. Incompletely compacted equilibrated ordinary chondrites

    SciTech Connect

    Sasso, M.R.; Macke, R.J.; Boesenberg, J.S.; Britt, D.T.; Rovers, M.L.; Ebel, D.S.; Friedrich, J.M.

    2010-01-22

    We document the size distributions and locations of voids present within five highly porous equilibrated ordinary chondrites using high-resolution synchrotron X-ray microtomography ({mu}CT) and helium pycnometry. We found total porosities ranging from {approx}10 to 20% within these chondrites, and with {mu}CT we show that up to 64% of the void space is located within intergranular voids within the rock. Given the low (S1-S2) shock stages of the samples and the large voids between mineral grains, we conclude that these samples experienced unusually low amounts of compaction and shock loading throughout their entire post accretionary history. With Fe metal and FeS metal abundances and grain size distributions, we show that these chondrites formed naturally with greater than average porosities prior to parent body metamorphism. These materials were not 'fluffed' on their parent body by impact-related regolith gardening or events caused by seismic vibrations. Samples of all three chemical types of ordinary chondrites (LL, L, H) are represented in this study and we conclude that incomplete compaction is common within the asteroid belt.

  17. Shock metamorphism of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Stoeffler, Dieter; Keil, Klaus; Scott, Edward R. D.

    1991-01-01

    This study proposes a revised petrographic classification of progressive stages of shock metamorphism of 26 ordinary chondrites. Six stages of shock (S1 to S6) are defined on the basis of shock effects in olivine and plagioclase as recognized by thin section microscopy, and the characteristic shock effects of each shock stage are described. It is concluded that shock effects and the sequence of progressively increasing degrees of shock metamorphosis are very similar in H, L, and LL groups. Differences in the frequency distribution of shock stages are relatively minor. It is suggested that the collisional histories of the H, L, and LL parent bodies were similar. Petrologic type-3 chondrites are deficient in stages S4 and S6 and, with increasing petrologic type, the frequency of stages S4 to S6 increases. It is suggested that the more porous and volatile-rich Type-3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type. Stage S3 is the most abundant in nearly all petrologic types.

  18. Oxygen isotopic abundances in calcium- aluminum-rich inclusions from ordinary chondrites: implications for nebular heterogeneity.

    PubMed

    McKeegan, K D; Leshin, L A; Russell, S S; MacPherson, G J

    1998-04-17

    The oxygen isotopic compositions of two calcium-aluminum-rich inclusions (CAIs) from the unequilibrated ordinary chondrite meteorites Quinyambie and Semarkona are enriched in 16O by an amount similar to that in CAIs from carbonaceous chondrites. This may indicate that most CAIs formed in a restricted region of the solar nebula and were then unevenly distributed throughout the various chondrite accretion regions. The Semarkona CAI is isotopically homogeneous and contains highly 16O-enriched melilite, supporting the hypothesis that all CAI minerals were originally 16O-rich, but that in most carbonaceous chondrite inclusions some minerals exchanged oxygen isotopes with an external reservoir following crystallization. PMID:9545215

  19. Metallic Fractions of Ordinary Chondrites: Implications to the Structure of Chondritic Parent Bodies

    NASA Astrophysics Data System (ADS)

    Ebihara, M.; Kong, P.

    1995-09-01

    Bulk metal and taenite fractions separated by a chemical method [1] from 23 ordinary chondrites were studied by INAA and Mossbauer spectroscopy. The elemental distributions demonstrate that siderophile elements, except Co and possibly As and Mo, are more enriched in taenite than kamacite but with different abundance ratios between them. Apparently, kamacite and taenite are not produced by redox reactions, condensation fractionation and melt-solid fractionation. Instead, kamacite and taenite can only be the equilibrated products by low temperature diffusion following the Fe-Ni phase diagram. Positive correlation of Co and Ni in carbonaceous chondritic metals and the existence of a high Co and low Ni metal phase in some LL chondrites suggest that chondritic kamacite and taenite can not be developed in the nebula. Rather, kamacite and taenite are produced through solid diffusion in the chondritic parent bodies. There is a large difference in the development of kamacite and taenite between the equilibrated and the unequilibrated L chondrites: the taenite phase of the unequilibrated L chondrites is mostly or totally developed into tetrataenite while low-Ni paramagnetic taenite is still present abundantly in the equilibrated L chondrites. The low-Ni paramagnetic taenite is believed to be an unequilibrated phase of either an incompletely transformed phase during fast cooling [2] or a metastable taenite located out of the miscibility gap on the Fe-Ni phase diagram [3]. In either case, the arrangement of the EOCs and the UOCs in the parent body was the same; the EOCs located near the surface of the parent body, with the UOCs being near the center, if they derived from the common parent body. An intrinsic thermal activity in the parent body would produce a temperature gradient decreasing from the center to the surface, whereas an external heating would exhibit the inverse trend. If a "reverse" onion shell structure is invoked, the generally accepted metamorphic temperatures of the equilibrated chondrites must be related with an external heating event rather than the intrinsic activity. The taenite fractions of the unequilibrated L chondrites have been developed into tetrataenite, suggesting that a cooling rate responsible to the development of kamacite and taenite was quite slow. The energy yielding such a slow cooling must have derived from intrinsic source, which heated the parent body to a temperature high enough for the development of kamacite and taenite, but too low to recrystallize silicates. During or after this "metamorphism", an external heating took place on the chondritic parent body, which recrystallized the silicates and modified the structure of kamacite and taenite. This external heating was more violent than the intrinsic one and may have derived from the early activities of the Sun. The highest temperature caused by the external heating was imprinted in the type 6 chondrites which located near the surface of the parent body, being in range of 800 C-950 C [4], and the temperature decreased gradually from the surface to the center of the body. Being different from L chondrites, H chondrites have no apparent difference in taenite components between EOCs and UOCs. If we assume similar thermal histories for both H and L chondrites, H chondritic parent body should be smaller than L's, with even its inner part being influenced to a certain degree during the external heating. References: [1] Kong P. et al. (1995) Proc. NIPR Symp. Antarct. Meteorites, 8, 237-249. [2] Gutlich P. et al. (1978) in Mossbauer Spectroscopy and Transition of Metal Chemistry, Springer-Verlag, Berlin-Heidelberg-New York. [3] Reuter K. B. et al. (1989) Metall. Trans., 20A, 719-725. [4] Dodd R. T. (1981) in Meteorites: A Petrologic-Chemical Synthesis, Cambridge Univ., London.

  20. Oxidation during metamorphism of the ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Labotka, Theodore C.

    1993-01-01

    It is suggested that some current concepts about the conditions of metamorphism in ordinary chondrites may be flawed. These meteorites display small systematic variations in the oxidation state of Fe. Evidence is presented that oxidation of Fe is linked to metamorphic grade in types 4-6 ordinary chondrites. This conclusion is at variance with a commonly accepted model for chondrite metamorphism that assumes Fe reduction by graphite.

  1. Oxidation during metamorphism of the ordinary chondrites

    NASA Astrophysics Data System (ADS)

    McSween, H. Y.; Labotka, T. C.

    1993-03-01

    It is suggested that some current concepts about the conditions of metamorphism in ordinary chondrites may be flawed. These meteorites display small systematic variations in the oxidation state of Fe. Evidence is presented that oxidation of Fe is linked to metamorphic grade in types 4-6 ordinary chondrites. This conclusion is at variance with a commonly accepted model for chondrite metamorphism that assumes Fe reduction by graphite.

  2. Multiple and fast: The accretion of ordinary chondrite parent bodies

    SciTech Connect

    Vernazza, P.; Barge, P.; Zanda, B.; Hewins, R.; Binzel, R. P.; DeMeo, F. E.; Lockhart, M.; Hiroi, T.; Birlan, M.; Ricci, L.

    2014-08-20

    Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot be resolved via laboratory measurements and/or experiments alone. Here, we propose the rationale for several new constraints on the formation and evolution of ordinary chondrite parent bodies (and, by extension, most planetesimals) from newly available spectral measurements and mineralogical analysis of main-belt S-type asteroids (83 objects) and unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter, we suggest that spectral data may be used to distinguish whether an ordinary chondrite was formed near the surface or in the interior of its parent body. If these constraints are correct, the suggested implications include that: (1) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteorites within a given class can originate from multiple parent bodies; (2) the surfaces of large (up to ?200 km) S-type main-belt asteroids mostly expose the interiors of the primordial bodies, a likely consequence of impacts by small asteroids (D < 10 km) in the early solar system; (3) the duration of accretion of the H chondrite parent bodies was likely short (instantaneous or in less than ?10{sup 5} yr, but certainly not as long as 1 Myr); (4) LL-like bodies formed closer to the Sun than H-like bodies, a possible consequence of the radial mixing and size sorting of chondrules in the protoplanetary disk prior to accretion.

  3. Semarkona meteorite: first recorded occurrence of smectite in an ordinary chondrite, and its implications

    SciTech Connect

    Hutchison, R.; Alexander, C.M.O.; Barber, D.J.

    1987-07-01

    Semarkona is an unshocked unequilibrated ordinary chondrite. Much of the interchondrule matrix and the mesostases of some chondrules and clasts have been hydrothermally altered. Analyses of altered materials and opaque matrix are presented. Ca and Fe have been redistributed from primary, anhydrous phases into calcite and Na, Fe smectite, respectively. In Semarkona the process possibly requires open system behavior inconsistent with the conventional view of metamorphism of the ordinary chondrites. The low petrologic type previously assigned to Semarkona is the result of retrograde metamorphism, under aqueous conditions, of a higher temperature mineral assemblage. Semarkona, and possibly Bishunpur, should be assigned to petrologic type 2.

  4. Fossil records of high level of 60Fe in chondrules from unequilibrated chondrites

    NASA Astrophysics Data System (ADS)

    Mishra, Ritesh Kumar; Chaussidon, Marc

    2014-07-01

    The short-lived now-extinct nuclide (SLN) 60Fe, which decays to 60Ni with a half-life of 2.62 Ma, is uniquely of stellar origin. Hence, its Solar System initial abundance yields information about the source of SLNs and the astrophysical environment in which the Solar System was born. Only a few chondrules (?19) from unequilibrated ordinary chondrites have reported resolved 60Ni excesses using in situ secondary ion mass spectrometry implying Fe60/Fe56>?0.6×10-7 in the early Solar System, and among these very few (3) have higher excesses implying Fe60/Fe56?7×10-7 (Mishra et al., 2010; Mishra and Goswami, 2014; Telus et al., 2012). At variance, multi-collector inductively coupled plasma mass spectrometer studies of bulk samples and mineral separates from differentiated meteorites, angrites, achondrites, and chondrules suggest a low abundance of 60Fe/56Fe of ?1.4×10-8 which would rule out the need for an external seeding of the early Solar with stellar 60Fe (Quitté et al., 2011; Tang and Dauphas, 2012). Two Semarkona chondrules and one Efremovka chondrule analyzed in the present study have mass fractionation corrected excess of up to ?75 permil (‰) and give 60Fe isochrons with initial 60Fe/56Fe ratios of (7.8±3.7)×10-7, (3.8±1.6)×10-7, and (2.2±1.1)×10-7 (2?), for Efremovka Ch 1, Semarkona Ch 12, and Semarkona Ch J5 respectively. The higher values of 60Fe/56Fe ratios seen in the chondrules of these least altered meteorites samples concur with and lend greater credence to the suggestion of a massive star as the source of 60Fe, and possibly of other short-lived nuclides, to the early Solar System. However, no definitive explanation (e.g. sample bias, effects of metamorphism, 60Fe heterogeneity) to the apparent disagreement with studies of bulk chondrules and chondrule fragments has been found.

  5. {sup 60}Fe AND {sup 26}Al IN CHONDRULES FROM UNEQUILIBRATED CHONDRITES: IMPLICATIONS FOR EARLY SOLAR SYSTEM PROCESSES

    SciTech Connect

    Mishra, R. K.; Goswami, J. N.; Rudraswami, N. G.; Tachibana, S.; Huss, G. R.

    2010-05-10

    The presence of about a dozen short-lived nuclides in the early solar system, including {sup 60}Fe and {sup 26}Al, has been established from isotopic studies of meteorite samples. An accurate estimation of solar system initial abundance of {sup 60}Fe, a distinct product of stellar nucleosynthesis, is important to infer the stellar source of this nuclide. Previous studies in this regard suffered from the lack of exact knowledge of the time of formation of the analyzed meteorite samples. We present here results obtained from the first combined study of {sup 60}Fe and {sup 26}Al records in early solar system objects to remove this ambiguity. Chondrules from unequilibrated ordinary chondrites belonging to low petrologic grades were analyzed for their Fe-Ni and Al-Mg isotope systematics. The Al-Mg isotope data provide the time of formation of the analyzed chondrules relative to the first solar system solids, the Ca-Al-rich inclusions. The inferred initial {sup 60}Fe/{sup 56}Fe values of four chondrules, combined with their time of formation based on Al-Mg isotope data, yielded a weighted mean value of (6.3 {+-} 2) x 10{sup -7} for solar system initial {sup 60}Fe/{sup 56}Fe. This argues for a high-mass supernova as the source of {sup 60}Fe along with {sup 26}Al and several other short-lived nuclides present in the early solar system.

  6. Classification of six ordinary chondrites from Texas

    NASA Astrophysics Data System (ADS)

    Ehlmann, Arthur J.; Keil, Klaus

    1988-12-01

    Based on optical microscopy, modal and electron microprobe analyses, six ordinary chondrites from Texas were classified in compositional groups, petrologic types, and shock facies. These meteorites are Comanche (stone), L5c; Haskell, L5c; Deport (a), H4b; Naruna (a), H4b; Naruna (b), H4b; and Clarendon (b), H5d.

  7. A comparison of FeO-rich, porphyritic olivine chondrules in unequilibrated chondrites and experimental analogues

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.; Lofgren, Gary E.

    1993-01-01

    Experimentally produced analogues of porphyritic olivine (PO) chondrules in ordinary chondrites provide an important insight into chondrule formation processes. We have studied experimental samples with PO textures grown at three different cooling rates (2, 5 and 100 C/h), and samples that have been annealed at high temperatures (1000-1200 C) subsequent to cooling. These are compared with natural chondrules of similar composition and texture from the ordinary chondrites Semarkona (LL3.0) and ALH 81251 (LL3.3). Zoning properties of olivine grains indicate that the Semarkona chondrules cooled at comparable rates to the experiments. Zoning in olivine from chondrules in ALH 81251 is not consistent with cooling alone but indicates that the chondrules underwent an annealing process. Chromium loss from olivine is very rapid during annealing and calculated diffusion coefficients for Cr in olivine are very similar to those of Fe-Mg interdiffusion coefficients under the same conditions. Annealed experimental samples contain an aluminous, low-Ca pyroxene which forms by reaction of olivine and liquid. No similar reaction texture is observed in ALH 81251 chondrules, and this may be evidence that annealing of the natural samples took place at considerably lower temperatures than the experimental analogues. The study supports the model of chondrule formation in a cool nebula and metamorphism of partly equilibrated chondrites during reheating episodes on the chondrite parent bodies.

  8. The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene

    NASA Technical Reports Server (NTRS)

    Weisberg, Michael K.; Prinz, Martin; Fogel, Robert A.

    1994-01-01

    FeO-rich (Fs(sub 6)-34) pyroxene lacking cathodoluminescence (CL), hereafter black pyroxene, is a major constituent of some of the chondrules 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 chondrules 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 chondrules that formed in a nebular region that was more oxidizing than that of the enstatite chondrites. Following solidification, these chondrules 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 chondrules in enstatite chondrites can be expressed in a four-stage model that includes: Stage 1. Formation of chondrules in an oxidizing nebular environment. Stage 2. Solid-state reduction of the more oxidized chondrules 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.

  9. Chemical and physical studies of type 3 chondrites - VI: siderophile elements in ordinary chondrites

    SciTech Connect

    Sears, D.W.G.; Weeks, K.S.

    1986-12-01

    The abundances of Fe, Ni, Co, Au, Ir, Ga, As and Mg have been determined by instrumental neutron activation analysis in 38 type 3 ordinary chondrites (10 of which may be paired) and 15 equilibrated chondrites. Classification of type 3 ordinary chondrites into the H, L and LL classes using oxygen isotopes and parameters which reflect oxidation state (Fa and Fs in the olivine and pyroxene, and Co in kamacite) is difficult or impossible. Bulk compositional parameters, based on the equilibrated chondrites, have therefore been used to classify the type 3 chondrites. The distribution of the type 3 ordinary chondrites over the classes is very different from that of the equilibrated chondrites, the LL chondrites being more heavily represented. The type 3 ordinary chondrites contain 5 to 15% lower abundances of siderophile elements, and a compilation of the present data and literature data indicates a small, systematic decrease in siderophile element concentration with decreasing petrologic type. The type 3 ordinary chondrites have, like the equilibrated ordinary chondrites, suffered a fractionation of their siderophile elements, but the loss of Ni in comparison with Au and Ir is greater for the type 3 chondrites. These siderophile element trends were established at the nebula phase of chondritic history and the co-variation with petrologic type implies onion-shell structures for the ordinary chondrite parent bodies. It is also clear that the relationship between the type 3 and the equilibrated ordinary chondrites involves more than simple, closed-system metamorphism.

  10. The duration of ordinary chondrite metamorphism inferred from tungsten microdistribution in metal

    NASA Astrophysics Data System (ADS)

    Humayun, Munir; Campbell, Andrew J.

    2002-04-01

    Precise ratios of W and Re relative to Ir determined by laser ablation ICP-MS reveal that matrix metal in equilibrated ordinary chondrites (EOC) exhibits a correlated variation of these ratios. In unequilibrated ordinary chondrites (UOC), the W/Ir ratio varies by over two orders of magnitude (W/Ir=0.003-0.6), and shows no correlation with any other siderophile element. Most matrix metal in UOC is depleted in W relative to metal in EOC. Thus, W must enter metal during metamorphism. The correlation between W/Ir and Re/Ir is evident in type 4 chondrites. This implies that the abundance (and isotopic composition) of W is set in ordinary chondrite metal by petrologic type 4, and that the reductant must be exhausted to limit further isotopic exchange, as indicated by the 182Hf- 182W ages of ordinary chondrite metal [Lee and Halliday, Science 274 (1996) 1876-1879]. This offers a means of dating the onset of metamorphic heating of OC parent bodies. A discrepancy in ages between 182Hf- 182W [Lee and Halliday, Science 274 (1996) 1876-1879] and 207Pb- 206Pb [Göpel et al., Earth Planet. Sci. Lett. 121 (1994) 153-171] (or 129I- 129Xe [Brazzle et al., Geochim. Cosmochim. Acta 63 (1999) 739-760]) dating is real, and measures the interval of metamorphism: the time difference between reduction of W during the onset of heating and isotopic closure of Pb (or Xe) by cooling, e.g., ? Tm=2-12 Myr for H chondrites. The 187Re- 187Os and 182Hf- 182W ages are set by the same process, metamorphic equilibration, establishing an important link between an absolute chronometer ( t1/2[ 187Re]=41.6 billion years) and a short-lived radioisotope system ( t1/2[ 182Hf]=9 Myr).

  11. Ubiquitous brecciation after metamorphism in equilibrated ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Lusby, D.; Keil, K.

    1985-01-01

    Ten objects with aberrant Fe/(Fe + Mg) ratios have been found in apparently unbrecciated types 4-6 H and L chondrites. Since the Fe/(Fe + Mg) ratios of these objects are incompatible with the metamorphic history of the host chondrites, it is concluded that a high proportion of ordinary chondrites are breccias that were lithified after peak metamorphism. This is consistent with the results of Scott (1984), who concluded that most type three ordinary chondrites are breccias of materials with diverse thermal histories, even though they do not show prominent brecciation. It is found that the classification scheme of Van Schmus and Wood (1967) does not identify chondrites with similar thermal histories; the petrologic type of a chondrite is only a measure of the average thermal history of its ingredients. Chondrite and achondrite breccias are also compared in order to understand how brecciation of chondrites after metamorphism is so well camouflaged.

  12. Penecontemporaneous metamorphism, fragmentation, and reassembly of ordinary chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Grimm, R. E.

    1985-01-01

    The thermal histories of ordinary chondrites and the canonical internal heating or onion shell models, which predict an inverse relation between the petrologic type of chondrites and the metallographic cooling rate, are reviewed. The thermal and accretional requirements of the 'metamorphosed planetesimal' model proposed by Scott and Rajan (1981) are analyzed, and an alternative model consistent with the metallographic cooling rate constraints is suggested in which ordinary chondrite parent bodies are collisionally fragmented and then rapidly reassembled before metamorphic heat has been dissipated.

  13. 187Re-187Os systematics, highly siderophile element, S-Se-Te abundances in the components of unequilibrated L chondrites

    NASA Astrophysics Data System (ADS)

    Kadlag, Yogita; Becker, Harry

    2016-01-01

    The 187Re-187Os systematics, abundances of highly siderophile elements (HSE: Re, platinum group elements and Au), Te, Se and S as well as major and minor elements were determined in separated components of two unequilibrated L chondrites QUE 97008 (L3.05) and Ceniceros (L3.7). The 187Re-187Os systematics are disturbed in the components of both meteorites, most likely due to open system behavior of Re during terrestrial weathering of QUE 97008 and alteration on the L chondrite parent body as indicated by an internal errorchron generated for components of Ceniceros. The HSE abundance patterns suggest that the bulk rock abundances were mainly controlled by two different end members. Non-magnetic fractions display lower Re/Os and HSE/Ir than CI chondrites. Chondrules, metal-troilite spherules and fine magnetic fractions, are depleted in refractory HSE and show higher Rh/Ir, Pd/Ir and Au/Ir than in CI chondrites. The different HSE compositions indicate the presence of unequilibrated alloys and loss of refractory HSE-rich carrier phases from the precursors of some L chondrite components. Gold is decoupled from other HSE in magnetic fractions and shows chalcophile affinities with a grain size dependent variation similar to S and Se, presumably inherited from preaccretionary processes. Tellurium is depleted in all components compared to other analysed siderophile elements, and its abundance was most likely controlled by fractional condensation and different geochemical affinities. The volatility dependent depletion of Te requires different physical and chemical conditions than typical for the canonical condensation sequence as represented by carbonaceous chondrites. Tellurium also shows variable geochemical behavior, siderophile in Ceniceros, predominantly chalcophile in QUE 97008. These differences may have been inherited from element partitioning during chondrule formation. Selenium and S on the other hand are almost unfractionated from each other and only show complementary S/Se in a few components, presumably due to the effects of volatility or metal-silicate partitioning during chondrule formation. Terrestrial weathering had negligible effects on the S, Se and Te systematics.

  14. Chromium on Eros: Further Evidence of Ordinary Chondrite Composition

    NASA Technical Reports Server (NTRS)

    Foley, C. N.; Nittler, L. R.; Brown, M. R. M.; McCoy, T. J.; Lim, L. F.

    2005-01-01

    The surface major element composition of the near-earth asteroid 433-Eros has been determined by x-ray fluorescence spectroscopy (XRS) on the NEAR-Shoemaker spacecraft [1]. The abundances of Mg, Al, Si, Ca and Fe match those of ordinary chondrites [1]. However, the observation that Eros appears to have a sulfur abundance at least a factor of two lower than ordinary chondrites, suggests either sulfur loss from the surface of Eros by impact and/or radiation processes (space weathering) or that its surface is comprised of a somewhat more differentiated type of material than an ordinary chondrite [1]. A definitive match for an ordinary chondrite parent body has very rarely been made, despite the conundrum that ordinary chondrites are the most prevalent type of meteorite found on Earth. Furthermore, Eros is classified as an S(IV) type asteroid [2] and being an S, it is the second most prevalent type of asteroid in the asteroid belt [3].

  15. Barred olivine chondrules in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Weisberg, Michael K.

    1987-01-01

    The characteristics of 125 barred olivine chondrules identified in polished thin sections of 26 H-L-LL3-6 chondrites were studied, using an electron microprobe for determining mineral abundances and a broad-beam electron microprobe for determining bulk compositions. Compared with all chondrule types in the H-L-LL3 ordinary chondrites, the barred olivine chondrules were found to be enriched in FeO, Al2O3, Na2O, and K2O and depleted in SiO2 and MgO; they were also found to be enriched in the feldspathic component. It is concluded that the precursor components of barred olivine chondrules consisted of a mixture of an olivine-rich component, a refractory-rich component containing Al2O3, TiO2, and CaO, and a volatile-rich alkalic component. This unusual combination implies high temperatures of melting for the refractory component and low temperatures for the volatile component, supporting the hypothesis of Grossman and Wasson (1983) that the alkalies condensed on the alumina already available.

  16. Multiple and fast: the accretion of ordinary chondrite parent bodies

    E-print Network

    Vernazza, P.

    Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there ...

  17. Classification of eight ordinary chondrites from Texas

    NASA Astrophysics Data System (ADS)

    Ehlmann, A. J.; Keil, K.

    1985-06-01

    Based on optical microscopy and electron microprobe analyses, eight previously undescribed or poorly known chondrites were classified into compositional groups, petrologic types, and degree of shock alteration. These chondrites are: Leander, L4b; Nazareth(a), L6d; La Villa, H4b; Mereta, H4c; Gail, H4d; Shafter Lake, H5a; Uvalde, H5d; and Howe, H5d.

  18. A hydrogen isotope study of CO3 type carbonaceous chondrites; comparison with type 3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Morse, A. D.; Newton, J.; Pillinger, C. T.

    1993-01-01

    Meteorites of the Ornans type 3 carbonaceous chondrites exhibit a range in degree of equilibration, attributed to differing amounts of thermal metamorphism. These differences have been used to split the CO3 chondrites into petrologic sub-types from 3.0, least equilibrated, to 3.7, being most equilibrated. This is similar to the system of assigning the type 3 ordinary chondrites into petrologic sub-types 3.0 to 3.9 based upon thermoluminescence (TL) and other properties; however, the actual range of thermal metamorphism experienced by CO3 chondrites is much less than that of the type 3 ordinary chondrites. The least equilibrated ordinary chondrites show evidence of aqueous alteration and have high D/H ratios possibly due to a deuterium-rich organic carrier. The aim of this study was to determine whether the CO3 chondrites, which have experienced similar secondary conditions to the type 3 ordinary chondrites, also contain a similar deuterium-rich carrier. To date a total of 5 CO3 meteorites, out of a set of 11 for which carbon and nitrogen isotopic data are available, have been analyzed. Ornans has not been analyzed yet, because it does not appear to fit in with the metamorphic sequence exhibited by the other CO3 chondrites; it also has an extremely high delta-D value of +2150 percent, unusual for such a comparatively equilibrated meteorite (type 3.4). Initial results indicate that the more equilibrated CO3's tend to have lower delta-D values, analogous to the higher petrologic type ordinary chondrites. However this is complicated by the effects of terrestrial weathering and the small data-set.

  19. Darkening in gas-rich ordinary chondrites: Spectral modelling and implications for the regoliths of ordinary chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Britt, Daniel T.; Pieters, Carle M.

    1991-01-01

    The dark fine grained matrix of gas-rich ordinary chondrites replicates many of the physical, morphological, and spectral characteristics of the highly shocked and optically altered black chondrites. Spectral mixture modeling shows that the darkening and spectral attenuation seen in the dark matrix can be simulated with realistic mass fractions of light host material and black chondritic material. All these factors point to the conclusion that the dark matrix of gas-rich ordinary chondrites is dark due to the same processes that darkens black chondrites, shock distributed small particle size FeNi metal and troilite. Because the darkening is not seen in any of the non-gas-rich light portions and is only seen in the gas rich grains of the meteorite, the shock darkening would have to occur as part of the matrix's exposure to regolith processes. Since all gas-rich grains are darkened, it follows that darkening is not only common, but pervasive in asteroidal regoliths. These results imply that the upper, optically active layer of an ordinary chondrite parent body should have the spectral characteristics of a black chondrite, which are a dark, relatively featureless spectrum with modest red slope in the infrared. These are the characteristics of special type C asteroids.

  20. Multiple parent bodies of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Yomogida, K.; Matsui, T.

    1984-01-01

    Thermal histories of chondrite parent bodies are calculated from an initial state with material in a powder-like form, taking into account the effect of consolidation state on thermal conductivity. The very low thermal conductivity of the starting materials makes it possible for a small body with a radius of less than 100 km to be heated by several hundred degrees even if long-lived radioactive elements in chondritic abundances are the only source of heat. The maximum temperature is determined primarily by the temperature at which sintering of the constituent materials occurs. The thermal state of the interior of a chondrite parent body after sintering has begun is nearly isothermal. Near the surface, however, where the material is unconsolidated and the thermal conductivity is much lower, the thermal gradient is quite large. This result contradicts the conventional 'onion-shell' model of chondrite parent bodies. But because the internal temperature is almost constant through the whole body, it supports a 'multiple-parent bodies' model, according to which each petrologic type of chondrite comes from a different parent body.

  1. The mineralogy of ordinary chondrites and implications for asteroid spectrophotometry

    NASA Astrophysics Data System (ADS)

    McSween, H. Y.; Bennett, M. E.; Jarosewich, E.

    1991-03-01

    Published data from bulk chemical analyses of 94 ordinary chondrites are compiled in a table of normative mineralogy and discussed in detail. Significant variations in olivine, pyroxene, and metal abundance ratios are found within each chondrite class and attributed to redox processes superimposed on initial differences in metal/silicate ratios. The use of the diagrams constructed here to predict the mineralogic characteristics of asteroids on the basis of spectrophotometric observations is suggested.

  2. Screening and classification of ordinary chondrites by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Pittarello, Lidia; Baert, Kitty; Debaille, Vinciane; Claeys, Philippe

    2015-10-01

    Classification of ordinary chondrite meteorites generally implies (1) determining the chemical group by the composition in endmembers of olivine and pyroxene, and (2) identifying the petrologic group by microstructural features. The composition of olivine and pyroxene is commonly obtained by microprobe analyses or oil immersion of mineral separates. We propose Raman spectroscopy as an alternative technique to determine the endmember content of olivine and pyroxene in ordinary chondrites, by using the link between the wavelength shift of selected characteristic peaks in the spectra of olivine and pyroxene and the Mg/Fe ratio in these phases. The existing correlation curve has been recalculated from the Raman spectrum of reference minerals of known composition and further refined for the range of chondritic compositions. Although the technique is not as accurate as the microprobe for determining the composition of olivine and pyroxene, for most of the samples the chemical group can be easily determined by Raman spectroscopy. Blind tests with ordinary chondrites of different provenance, weathering, and shock stages have confirmed the potential of the method. Therefore, we suggest that a preliminary screening and the classification of most of the equilibrated ordinary chondrites can be carried out using an optical microscope equipped with a Raman spectrometer.

  3. 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.

  4. Noble-gas-rich separates from ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Moniot, R. K.

    1980-02-01

    Acid-resistant residues were prepared by HCl-HF demineralization of three H-type ordinary chondrites: Brownfield 1937 (H3), Dimmitt (H3, 4), and Estacado (H6). These residues were found to contain a large proportion of the planetary-type trapped Ar, Kr, and Xe in the meteorites. The similarity of these acid residues to those from carbonaceous chondrites and LL-type ordinary chondrites suggests that the same phase carries the trapped noble gases in all these diverse meteorite types. Because the H group represents a large fraction of all meteorites, this result indicates that the gas-rich carrier phase is as universal as the trapped noble-gas component itself. When treated with an oxidizing etchant, the acid residues lost almost all their complement of noble gases.

  5. Chemical and physical studies of type 3 chondrites. XI - Metamorphism, pairing, and brecciation of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Sears, D. W. G.; Hasan, F. A.; Batchelor, J. D.; Lu, J.

    1991-01-01

    The present study reports recent measurements of the induced thermoluminescence (TL) properties of 69 type-3 ordinary chondrites, bringing to 125 the number of type-3 ordinary chondrites for which TL data are available. The samples include several of the particularly low petrographic type and many breccias, some of them gas-rich. The significance of the data with respect to the physical conditions affecting metamorphism is discussed. The TL data, olivine heterogeneity, carbon content, and inert-gas content were used to assign the samples to petrologic types. Twelve meteorites were identified as being type 3.0-3.2, and 10 of the breccias were found to contain material that may also be of this type. The temperature and width of the induced TL peak are also related to thermal history, with type 3.2-3.4 chondrites tending to have narrower peaks at lower glow curve temperatures than the type 3.6-3.9 chondrites. Type 3 H chondrites were found to be a higher petrographic type than the type 3 L and LL chondrites.

  6. Rapid Classification of Ordinary Chondrites Using Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Fries, M.; Welzenbach, L.

    2014-01-01

    Classification of ordinary chondrites is typically done through measurements of the composition of olivine and pyroxenes. Historically, this measurement has usually been performed via electron microprobe, oil immersion or other methods which can be costly through lost sample material during thin section preparation. Raman microscopy can perform the same measurements but considerably faster and with much less sample preparation allowing for faster classification. Raman spectroscopy can facilitate more rapid classification of large amounts of chondrites such as those retrieved from North Africa and potentially Antarctica, are present in large collections, or are submitted to a curation facility by the public. With development, this approach may provide a completely automated classification method of all chondrite types.

  7. Post-metamorphic brecciation in type 3 ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Scott, E. R. D.; McCoy, T. J.; Keil, K.

    1993-03-01

    Type 3.1-3.9 ordinary chondrites can be divided into two kinds: those in which the compositions of chondrule silicates are entirely consistent with metamorphism of type 3.0 material, and those in which the computational heterogeneity appears to be too extreme for in situ metamorphism. We present petrologic data for three LL3 chondrites of the second kind--Ngawi, ALH A77278 (both type 3.6), and Hamlet (type 3.9)--and compare these data with results for the first kind of LL3-4 chondrites. Given that chondrules form in the nebula and that metamorphic equilibration occurs in asteroids, our new data imply that Ngawi, A77278, Hamlet, and many other type 3 ordinary chondrites are post-metamorphic breccias containing materials with diverse metamorphic histories; they are not metamorphic rocks or special kinds of 'primitive breccias.' We infer also that metamorphism to type 3.1-3.9 levels produces very friable material that is easily remixed into breccias and lithified by mild shock. Thus, petrologic types and subtypes of chondrites indicate the mean metamorphic history of the ingredients, not the thermal history of the rock. The metamorphic history of individual type 1 or 2 porphyritic chondrules in type 3 breccias is best derived from olivine and pyroxene analyses and the data of McCoy et al. for unbrecciated chondrites. The new chondrule classification schemes of Sears, DeHart et al., appears to provide less information about the original state and metamorphic history of individual porphyritic chondrules and should not replace existing classification schemes.

  8. Post-metamorphic brecciation in type 3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Mccoy, T. J.; Keil, K.

    1993-01-01

    Type 3.1-3.9 ordinary chondrites can be divided into two kinds: those in which the compositions of chondrule silicates are entirely consistent with metamorphism of type 3.0 material, and those in which the computational heterogeneity appears to be too extreme for in situ metamorphism. We present petrologic data for three LL3 chondrites of the second kind--Ngawi, ALH A77278 (both type 3.6), and Hamlet (type 3.9)--and compare these data with results for the first kind of LL3-4 chondrites. Given that chondrules form in the nebula and that metamorphic equilibration occurs in asteroids, our new data imply that Ngawi, A77278, Hamlet, and many other type 3 ordinary chondrites are post-metamorphic breccias containing materials with diverse metamorphic histories; they are not metamorphic rocks or special kinds of 'primitive breccias.' We infer also that metamorphism to type 3.1-3.9 levels produces very friable material that is easily remixed into breccias and lithified by mild shock. Thus, petrologic types and subtypes of chondrites indicate the mean metamorphic history of the ingredients, not the thermal history of the rock. The metamorphic history of individual type 1 or 2 porphyritic chondrules in type 3 breccias is best derived from olivine and pyroxene analyses and the data of McCoy et al. for unbrecciated chondrites. The new chondrule classification schemes of Sears, DeHart et al., appears to provide less information about the original state and metamorphic history of individual porphyritic chondrules and should not replace existing classification schemes.

  9. Carbon in weathered ordinary chondrites from Roosevelt County

    NASA Technical Reports Server (NTRS)

    Ash, R. D.; Pillinger, C. T.

    1993-01-01

    A suite of Roosevelt County ordinary chondrites of known terrestrial age have been analyzed for carbon content and isotopic composition. Initial results indicate that significant carbon contamination is evident only in samples with a terrestrial age greater than 40 ka. These samples are of weathering grade D and E and contain three times more carbon than the less weathered samples. The soil in which they were preserved has a carbon content of ca. 1.5 percent. Over 200 meteorites have been recovered from a series of soil depleted areas of New Mexico and West Texas. Most have been recovered from blowouts near Clovis in Roosevelt County (RC) on the high plains of New Mexico. The mineralogical and petrologic Al effects of weathering upon these samples have been studied previously and show that the degree of weathering is largely depend ant upon the terrestrial residence time. The study was undertaken to determine the effects of prolonged exposure to the soil and climate of Roosevelt County upon ordinary chondrites in the hope that this will enable a better understanding of the problems associated with the collection of meteoritic falls. A suite of ten grade 4 to 6 H, L, and LL ordinary chondrites were analyzed for carbon content and isotopic composition.

  10. Hot Accretion of the Ordinary Chondrites: The Rocks Don't Lie

    NASA Astrophysics Data System (ADS)

    Hutchison, R.

    1996-03-01

    The ordinary chondrites (OCs) comprise three petrographic series, each ranging from type 3 (the UOCs), with distinct chondrules, little crystalline intergrowth and unequilibrated minerals, to type 6 or 7, in which chondrules have largely disappeared into a granular textured fabric with little mineralogical disequilibrium. There are conflicting interpretations of the textural progression. Many believe that the OCs formed by accretion of 'cold' silicate chondrules, chondrule fragments, metal, sulphide and fine-grained material, followed by thermal metamorphism. A minority argues that the constituents accreted 'hot' and that the textural progression resulted from different cooling rates; type 3 cooled rapidly, types 6 and 7 cooled slowly. Hot accretion has been attacked by Haack et al., from the premise that chondrules are nebular, and by Rubin, who suggests that OCs are 'brecciated on millimeter-sized scales' to explain the presence of grains that do not fit the metamorphic model. Some OCs are not post-crystallisation breccias and contain mineralogical evidence that is incompatible with cold accretion and prograde metamorphism.

  11. Metal Phases of Ordinary Chondrites: Melting Remnants or Nebular Condensates?

    NASA Astrophysics Data System (ADS)

    Kong, P.; Ebihara, M.

    1995-09-01

    Bulk metals of 10 H, 6 L and 7 LL chondrites were analyzed by INAA. A significant difference in the metallic compositions between EOCs and UOCs is noted for the abundances of three lithophile elements, Cr, Mn and V, and three weakly siderophile elements, W, Mo and Ga. The abundances of W, Mo and Ga are increased and those of Cr, Mn and V are decreased with increase of petrographic type. According to condensation sequence [1], Fe condensed into a metal phase at high temperature. With temperature falling, metallic Fe was partly oxidized into silicates and partly transferred into troilite during equilibrium with the solar nebula. If Fe could equilibrate with the solar nebula, it is not expected that V, Cr and Mn still remain partly in the metal phases since they would be oxidized at higher temperatures than that for oxidizing Fe. Rapid formation of silicates around metal grains might preserve these elements but should keep W and Mo quantitatively present in the metals. Our results show that relative to Ir and Os, W and Mo are both depleted in the UOC metals to some extents, implying that portions of W and Mo are present in the non-metal phases. It is difficult to envision that the "being reduced" V, Cr and Mn can coexist with the "being oxidized" W, Mo and Ga in the metallic fractions if the metallic fractions were nebula condensates. W, Mo and Ga are enriched in the metallic fractions of the EOCs in order of W>Mo>Ga, while in those of the UOCs the order changes to Mo>W>Ga. We believe that the truly equilibrated distributions of W and Mo among different phases are preserved in the equilibrated chondrites, because the redox states of the elements must have been readjusted to reach equilibrium or near to equilibrium during the thermal metamorphism. So, if the UOC metals were equilibrated condensates, the relative distributions of W and Mo in the UOC metals should be similar to those in the EOC metals. However, this is not the case. If the metals were interstellar grains and have not changed their characteristics before the accretion of chondrites, the compositions of the metals should be uniform for all ordinary chondrites of different chemical groups. In fact, they have changed. If the compositions of the metals were adjusted according to the redox condition in places where chondrites formed, the contradictory states of "being reduced" V, Mn and Cr and "being oxidized" W, Mo and Ga preserved in the UOC metals must be erased. Thus, it seems implausible that the metals of ordinary chondrites were the interstellar grains before their accreting into chondrites. Formation of chondritic metals seems to be attributable only to the remaining melting mechanism. Experimental results showed that the metal/silicate partition coefficients of W were always lower than those of Mo at temperature 1300 degrees C and oxygen fugacities between 10^-13 to 10^-11 bars [2]. Moreover, partition behaviors of Cr, V and Mn [3] are similar to those found in the UOCs. The consistence of experimental partition coefficients of W, Mo, Ga, V, Cr and Mn with their abundance ratios between metal and silicate phases of UOCs suggests that the UOC metals were formed by a melting mechanism. It is thus concluded that the metals of ordinary chondrites were the melting remnants before they were accreted into chondritic parent bodies. References: [1] Wasson J. T. (1985) in Meteorites: Their Record of Early Solar-System History, Freeman, New York. [2] Schmitt W. et al. (1989) GCA, 53, 173-185. [3] Drake M. J. et al. (1989) GCA, 53, 2101-2111.

  12. Defining the Petrology of Pseudotachylytes in Ordinary Chondrites: An Experimental and Deductive Approach

    NASA Technical Reports Server (NTRS)

    vanderBogert, C. H.; Schultz, P. H.; Spray, J. G.

    2000-01-01

    Evidence for deformation in ordinary chondrites suggests that meteorite evolution involves high strain-rate processes. Unexpected experimental results and an analysis of physical properties of chondrite minerals supports and defines this contention.

  13. Kamacite and olivine in ordinary chondrites - Intergroup and intragroup relationships

    NASA Astrophysics Data System (ADS)

    Rubin, A. E.

    1990-05-01

    Results are presented from high-precision electron microprobe analyses of olivine and kamacite in a suite of 134 ordinary chondrites (OCs). The compositional ranges of these phases are defined for each OC group (high total Fe, low total Fe, and low total Fe/low metallic Fe). Anomalous OCs that have olivine and/or kamacite compositions that lie outside the established ranges are identified. The phases in the chondritic clasts of the Netschaevo iron meteorite are characterized to determine the relationship between Netschaevo and OCs. Intragroup variations of olivine and kamacite compositions with petrologic type are examined and OCs that contain olivine and/or kamacite grains with aberrant compositions are identified as fragmental breccias. Also, a search for new metallic Fe-Ni phases with extreme compositions is conducted. As a result of these analyses, several meteorites are reclassified.

  14. Unusual olivine and pyroxene composition in interplanetary dust and unequilibrated ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Klock, W.; Mckay, D. S.; Thomas, K. L.; Palme, H.

    1989-01-01

    The presence, in both a number of interplanetary dust particles (IDPs) and in meteorite matrices, of olivine and orthopyroxene grains, low in FeO but containing up to 5 wt pct MnO, is reported. The majority of olivines and pyroxenes in meteorites contain less than 0.5 wt pct MnO. The presence of these low-iron, manganese-enriched (LIME) olivines and pyroxenes in IDPs and meteorites may indicate a link between the origin and history of IDPs and the matrix material of primitive meteorites. The origin of the LIME silicates could be explained by condensation from a gas of solar composition. Forsterite is the first major silicate phase to condense from a solar nebula gas, and Mn, which is not stable as a metal under solar nebula conditions, would condense at about 1100 K as Mn2SiO4 in solid solution with forsterite.

  15. The onset of metamorphism in ordinary and carbonaceous chondrites

    USGS Publications Warehouse

    Grossman, J.N.; Brearley, A.J.

    2005-01-01

    Ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by X-ray mapping techniques. A variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cathodoluminescence (CL) methods. The distribution of Cr in FeO-rich olivine systematically changes as metamorphism increases between type 3.0 and type 3.2. Igneous zoning patterns are replaced by complex ones and Cr-rich coatings develop on all grains. Cr distributions in olivine are controlled by the exsolution of a Cr-rich phase, probably chromite. Cr in olivine may have been partly present as tetrahedrally coordinated Cr3+. Separation of chromite is nearly complete by petrologic type 3.2. The abundance of chondrules showing an inhomogeneous distribution of alkalis in mesostasis also increases with petrologic type. TEM shows this to be the result of crystallization of albite. Residual glass compositions systematically change during metamorphism, becoming increasingly rich in K. Glass in type I chondrules also gains alkalis during metamorphism. Both types of chondrules were open to an exchange of alkalis with opaque matrix and other chondrules. The matrix in the least metamorphosed chondrites is rich in S and Na. The S is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains. Progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules. Alkalis initially leave the matrix and enter chondrules during early metamorphism. Feldspar subsequently nucleates in the matrix and Na re-enters from chondrules. These metamorphic trends can be used to refine classification schemes for chondrites. Cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to subdivide types 3.0 and 3.1 into types 3.00 through 3.15. On this basis, the most primitive ordinary chondrite known is Semarkona, although even this meteorite has experienced a small amount of metamorphism. Allan Hills (ALH) A77307 is the least metamorphosed CO chondrite and shares many properties with the ungrouped carbonaceous chondrite Acfer 094. Analytical problems are significant for glasses in type II chondrules, as Na is easily lost during microprobe analysis. As a result, existing schemes for chondrule classification that are based on the alkali content of glasses need to be revised. ?? The Meteorological Society, 2005.

  16. Textural variability of ordinary chondrite chondrules: Implications of their formation

    NASA Technical Reports Server (NTRS)

    Zinovieva, N. G.; Mitreikina, O. B.; Granovsky, L. B.

    1994-01-01

    Scanning electron microscopy (SEM) and microprobe examination of the Raguli H3-4, Saratov L3, and Fucbin L5-6 ordinary chondrites and the analysis of preexisted data on other meteorites have shown that the variety of textural types of chondrules depends on the chemical composition of the chondrules. The comparison of bulk-rock chemistries of the chondrules by major components demonstrates that they apparently fall, like basic-ultrabasic rock, into groups of dunitic and pyroxenitic composition. This separation is further validated by the character of zoning in chondrules of the intermediate, peridotitic type. The effect is vividly demonstrated by the 'chondrule-in-chondrule' structure.

  17. Metallographic cooling rates of L-group ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Bennett, Marvin E.; Mcsween, Harry Y., Jr.

    1993-01-01

    Shock metamorphism appears to be a ubiquitous feature in L-group ordinary chondrites. Brecciation and heterogeneous melting obscure much of the early history of this meteorite group and have caused confusion as to whether L chondrites have undergone thermal metamorphism within onion-shell or rubble-pile parent bodies. Employing the most recent shock criteria, we have examined 55 Antarctic and 24 non-Antarctic L chondrites in order to identify those which have been least affected by post-accretional shock. Six low-shock samples (those with shock grade less than S4) of petrographic types L3-L5 were selected from both populations and metallographic cooling rates were obtained following the technique of Willis and Goldstein. All non-Antarctic L6 chondrites inspected were too heavily shocked to be included in this group. However, 4 shocked L6 chondrites were analyzed in order to determine what effects shock may impose on metallographic cooling rates. Metallographic cooling rates were derived by analyzing the cores of taenite grains and then measuring the distance to the nearest grain edge. Taenites were identified using backscatter imaging on a Cameca SX-50 electron microprobe. Using backscatter we were able to locate homogeneous, rust-free, nearly spherical grains. M-shaped profiles taken from grain traverses were also used to help locate the central portions of selected grains. All points which contained phosphorus above detection limits were discarded. Plots of cooling-rate data are summarized and data from the high-shock samples are presented. The lack of coherency of cooling rates for individual samples is indicative of heterogeneous cooling following shock. The data confirms the statement expressed by numerous workers that extreme care must be taken when selecting samples of L chondrites for cooling-rate studies. Data for the 6 non-Antarctic low-shock samples are also presented. The samples display a general trend in cooling rates. The lowest metamorphic grade yielded the slowest cooling rates and an increase in grade follows an increase in cooling rate. This is the opposite relationship to that predicted by the onion-shell model.

  18. Fe-Ni metal in primitive chondrites: Indicators of classification and metamorphic conditions for ordinary and CO chondrites

    USGS Publications Warehouse

    Kimura, M.; Grossman, J.N.; Weisberg, M.K.

    2008-01-01

    We report the results of our petrological and mineralogical study of Fe-Ni metal in type 3 ordinary and CO chondrites, and the ungrouped carbonaceous chondrite Acfer 094. Fe-Ni metal in ordinary and CO chondrites occurs in chondrule interiors, on chondrule surfaces, and as isolated grains in the matrix. Isolated Ni-rich metal in chondrites of petrologic type lower than type 3.10 is enriched in Co relative to the kamacite in chondrules. However, Ni-rich metal in type 3.15-3.9 chondrites always contains less Co than does kamacite. Fe-Ni metal grains in chondrules in Semarkona typically show plessitic intergrowths consisting of submicrometer kamacite and Ni-rich regions. Metal in other type 3 chondrites is composed of fine- to coarse-grained aggregates of kamacite and Ni-rich metal, resulting from metamorphism in the parent body. We found that the number density of Ni-rich grains in metal (number of Ni-rich grains per unit area of metal) in chondrules systematically decreases with increasing petrologic type. Thus, Fe-Ni metal is a highly sensitive recorder of metamorphism in ordinary and carbonaceous chondrites, and can be used to distinguish petrologic type and identify the least thermally metamorphosed chondrites. Among the known ordinary and CO chondrites, Semarkona is the most primitive. The range of metamorphic temperatures were similar for type 3 ordinary and CO chondrites, despite them having different parent bodies. Most Fe-Ni metal in Acfer 094 is martensite, and it preserves primary features. The degree of metamorphism is lower in Acfer 094, a true type 3.00 chondrite, than in Semarkona, which should be reclassified as type 3.01. ?? The Meteoritical Society, 2008.

  19. Source of potassium in shocked ordinary chondrites J.R. Weirich a,

    E-print Network

    Downs, Robert T.

    Source of potassium in shocked ordinary chondrites J.R. Weirich a, , T.D. Swindle a,b , C (a variation of potassium­argon dating) of ordinary chondrites is being used to reconstruct the col shocked nature of chon- drites, the sources of potassium (K) in these meteorites have not been fully

  20. SType Asteroids, Ordinary Chondrites, and Space Weathering: The Evidence from Galileo's Flybys of Gaspra and Ida

    E-print Network

    Chapman, Clark R.

    S­Type Asteroids, Ordinary Chondrites, and Space Weathering: The Evidence from Galileo's Fly 1996 Abstract. New observations of the S­type asteroids Gaspra and, especially, Ida by the Galileo tend to convert spectra of ordinary chondrites to have the spectral traits of S­type asteroids

  1. Anomalous Oxygen Isotopic Compositions of Unequilibrated but Supposedly Ordinary Chondrites, Including Ungrouped Silica-Bearing Chondrite Jiddat Al Harasis 846

    NASA Astrophysics Data System (ADS)

    Ziegler, K.; Irving, A. J.; Kuehner, S. M.; Sipiera, P. P.

    2015-07-01

    JaH 846 has many features suggestive of an UOC. It is unusual in having silica and opx in chondrules, and in oxygen isotopic compositions that plot beyond (?18O) and below (?17O) the ranges for OCs. We conclude it derived from a unique parent body.

  2. Aluminum-, Calcium- And Titanium-Rich Oxide Stardust In Ordinary Chondrite Meteorites

    E-print Network

    Larry R. Nittler; Conel M. O'D. Alexander; Roberto Gallino; Peter Hoppe; Ann N. Nguyen; Frank J. Stadermann; Ernst K. Zinner

    2008-04-17

    We report isotopic data for a total of 96 presolar oxide grains found in residues of several unequilibrated ordinary chondrite meteorites. Identified grain types include Al2O3, MgAl2O4, hibonite (CaAl12O19) and Ti oxide. This work greatly increases the presolar hibonite database, and is the first report of presolar Ti oxide. O-isotopic compositions of the grains span previously observed ranges and indicate an origin in red giant and asymptotic giant branch (AGB) stars of low mass (<2.5 MSun) for most grains. Cool bottom processing in the parent AGB stars is required to explain isotopic compositions of many grains. Potassium-41 enrichments in hibonite grains are attributable to in situ decay of now-extinct 41Ca. Inferred initial 41Ca/40Ca ratios are in good agreement with model predictions for low-mass AGB star envelopes, provided that ionization suppresses 41Ca decay. Stable Mg and Ca isotopic ratios of most of the hibonite grains reflect primarily the initial compositions of the parent stars and are generally consistent with expectations for Galactic chemical evolution, but require some local interstellar chemical inhomogeneity. Very high 17O/16O or 25Mg/24Mg ratios suggest an origin for some grains in binary star systems where mass transfer from an evolved companion has altered the parent star compositions. A supernova origin for the hitherto enigmatic 18O-rich Group 4 grains is strongly supported by multi-element isotopic data for two grains. The Group 4 data are consistent with an origin in a single supernova in which variable amounts of material from the deep 16O-rich interior mixed with a unique end-member mixture of the outer layers. The Ti oxide grains primarily formed in low-mass AGB stars. They are smaller and rarer than presolar Al2O3, reflecting the lower abundance of Ti than Al in AGB envelopes.

  3. The compositions of chondrules in unequilibrated chondrites An evaluation of models for the formation of chondrules and their precursor materials

    NASA Technical Reports Server (NTRS)

    Grossman, J. N.; Wasson, J. T.

    1983-01-01

    Recent progress toward the resolution of the problem of chondrule composition is reviewed. Special attention is given to studies of both the chemical and textural properties of chondrules. The characteristic variations of the composition of carbonaceous chondrite chrondules are discussed within the framework of current theories of chondrule evolution. Consideration is also given to the possible mechanisms for chondrule melts, and the relationship between chondrules and other chondrite components.

  4. Thermoluminescence sensitivity and thermal history of type 3 ordinary chondrites: Eleven new type 3.0-3.1 chondrites and possible explanations for differences among H, L, and LL chondrites

    NASA Astrophysics Data System (ADS)

    Benoit, P. H.; Akridge, G. A.; Ninagawa, K.; Sears, D. W. G.

    2002-06-01

    We review induced thermoluminescence (TL) data for 102 unequilibrated ordinary chondrites (UOCs), many data just published in abstracts, in order to identify particularly primitive UOCs and further explore TL systematics that may have implications for the history of the chondrites and their parent body. We have identified 11 UOCs of petrologic types 3.0-3.1: Adrar 003, Elephant Moraine (EET) 90066, EET 90161, Grosvenor Mountains (GRO) 95502, Lewis Cliff (LEW) 88477, Meteorite Hills (MET) 96503, Yamato (Y)-790787, Y-791324, Y-791558, Y-793565, and Y-793596. These samples represent an important new resource for researchers interested in the nature of primitive solar system materials. Previously reported trends in which TL sensitivity increases with TL peak temperature and TL peak width, which we interpret in terms of crystallization of feldspar in the ordered or disordered forms during metamorphism, are confirmed by the new data. Importantly, the present data strengthen the trend described earlier in which the mean level of metamorphism experienced by UOCs increases along the series LL, L and H. This suggests either different burial depths for the UOCs from each class, or formation at similar depths in regoliths of different thickness.

  5. Volatile element chemistry during metamorphism of ordinary chondritic material and some of its implications for the composition of asteroids

    E-print Network

    Volatile element chemistry during metamorphism of ordinary chondritic material and some of its to model thermal metamorphism of ordinary chondritic material as a function of temperature, pressure metamorphism of ordinary chondrite parent bodies. We com- piled trace element abundances in H-, L-, and LL

  6. Igneous rock from Severnyi Kolchim (H3) chondrite: Nebular origin

    NASA Technical Reports Server (NTRS)

    Nazarov, M. A.; Brandstaetter, F.; Kurat, G.

    1993-01-01

    The discovery of lithic fragments with compositions and textures similar to igneous differentiates in unequilibrated ordinary chondrites (UOC's) and carbonaceous chondrites (CC's) has been interpreted as to suggest that planetary bodies existed before chondrites were formed. As a consequence, chondrites (except, perhaps CI chondrites) cannot be considered primitive assemblages of unprocessed nebular matter. We report about our study of an igneous clast from the Severnyi Kolchim (H3) chondrite. The results of the study are incompatible with an igneous origin of the clast but are in favor of a nebular origin similar to that of chondrules.

  7. Metamorphism and partial melting of ordinary chondrites: Calculated phase equilibria

    NASA Astrophysics Data System (ADS)

    Johnson, T. E.; Benedix, G. K.; Bland, P. A.

    2016-01-01

    Constraining the metamorphic pressures (P) and temperatures (T) recorded by meteorites is key to understanding the size and thermal history of their asteroid parent bodies. New thermodynamic models calibrated to very low P for minerals and melt in terrestrial mantle peridotite permit quantitative investigation of high-T metamorphism in ordinary chondrites using phase equilibria modelling. Isochemical P-T phase diagrams based on the average composition of H, L and LL chondrite falls and contoured for the composition and abundance of olivine, ortho- and clinopyroxene, plagioclase and chromite provide a good match with values measured in so-called equilibrated (petrologic type 4-6) samples. Some compositional variables, in particular Al in orthopyroxene and Na in clinopyroxene, exhibit a strong pressure dependence when considered over a range of several kilobars, providing a means of recognising meteorites derived from the cores of asteroids with radii of several hundred kilometres, if such bodies existed at that time. At the low pressures (<1 kbar) that typify thermal metamorphism, several compositional variables are good thermometers. Although those based on Fe-Mg exchange are likely to have been reset during slow cooling, those based on coupled substitution, in particular Ca and Al in orthopyroxene and Na in clinopyroxene, are less susceptible to retrograde diffusion and are potentially more faithful recorders of peak conditions. The intersection of isopleths of these variables may allow pressures to be quantified, even at low P, permitting constraints on the minimum size of parent asteroid bodies. The phase diagrams predict the onset of partial melting at 1050-1100 °C by incongruent reactions consuming plagioclase, clinopyroxene and orthopyroxene, whose compositions change abruptly as melting proceeds. These predictions match natural observations well and support the view that type 7 chondrites represent a suprasolidus continuation of the established petrologic types at the extremes of thermal metamorphism. The results suggest phase equilibria modelling has potential as a powerful quantitative tool in investigating, for example, progressive oxidation during metamorphism, the degree of melting and melt loss or accumulation required to produce the spectrum of differentiated meteorites, and whether the onion shell or rubble pile model best explains the metamorphic evolution of asteroid parent bodies in the early solar system.

  8. Weathering Effects on Ordinary Chondrites from the Lut Desert (Iran) Studied by 57Fe Mössbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Scorzelli, R. B.; De Avillez, R. R.; Pourkhorsandi, H.; Rochette, P.; Gattacceca, J.

    2015-07-01

    The Lut Desert (Iran) is a high-potential region for preserving large concentrations of meteorites. In this work, we will apply 57Fe Mössbauer spectroscopy to investigate weathering in ordinary chondrites collected in different areas from Lut Desert.

  9. Rhenium-osmium isotope systematics of ordinary chondrites and iron meteorites

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Morgan, J. W.; Horan, M. F.; Grossman, J. N.

    1993-01-01

    Using negative thermal ionization mass spectrometry, Re and Os abundances were determined by isotope dilution and Os-187/Os-186 measured in 11 ordinary chondrites, and also in 1 IIB and 3 IIIB irons. In addition, Os-186/Os-188 and Os-189/Os-188 ratios were precisely determined for 3 unspiked ordinary chondrites as a means of constraining the intensity of any neutron irradiation these meteorites may have experienced.

  10. Metamorphism and aqueous alteration in low petrographic type ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Xie, T.; Lipschutz, M. E.; Sears, D. W. G.; Guimon, R. K.; Jie, Lu; Benoit, P. H.; O'D. Alexander, C. M.; Wright, Ian; Pillinger, C.; Morse, A. D.; Hutchison, Robert

    1995-01-01

    In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondruies, chondruies were hand-picked from the Semarkona (petrographic type 3.0), Bishunpur (3. 1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron-microprobe and radiochemical neutron activation and the water and H-isotopic composition determined. The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to approx. 8000% SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work. With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondruies, indicating metamorphism-related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence for aqueous alteration, but the matrix contains H with approximately terrestrial D/H values, even though it contains much water. Secondary processes (probably aqueous alteration) presumably lowered the D/H of the matrix and certain chondrules. While chondrule properties appear to be governed primarily by formation processes and subsequent metamorphism, the matrix of Semarkona has a more complex history involving aqueous alteration as a meteorite-wide process.

  11. Ion microprobe magnesium isotope analysis of plagioclase and hibonite from ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Hinton, R. W.; Bischoff, A.

    1984-01-01

    Ion and electron microprobes were used to examine Mg-26 excesses from Al-26 decay in four Al-rich objects from the type 3 ordinary hibonite clast in the Dhajala chondrite. The initial Al-26/Al-27 ratio was actually significantly lower than Al-rich inclusions in carbonaceous chondrites. Also, no Mg-26 excesses were found in three plagioclase-bearing chondrules that were also examined. The Mg-26 excesses in the hibonite chondrites indicated a common origin for chondrites with the excesses. The implied Al-26 content in a proposed parent body could not, however, be confirmed as a widespread heat source in the early solar system.

  12. Physical propoerties of incompletely compacted equilibrated ordinary chondrites: Implications for asteroidal structure and impact processing

    SciTech Connect

    Sasso, M.R.; Macke, R.J.; Britt, D.T.; Rivers, M.L.; Ebel, D.S.; Friedrich, J.M.

    2009-03-19

    Aside from robotic exploration, meteorites are our primary source of information about the asteroids that they sample. Although there are some discrepancies, there are dynamical, spectral, and compositional evidence for an S-type asteroid connection to the ordinary chondrite meteorites. Reconciling the measured bulk density of chondrites with that of asteroids can yield important inferences about the internal structure of asteroids. For example, the bulk density of S-type asteroids is typically much less than the bulk density of chondrites, leading to the inference that asteroids contain a significant quantity of macroporosity. We have identified several unusual ordinary chondrites that have been incompletely compacted relative to petrologically similar but much less porous chondrites. Although these are equilibrated chondrites, they have extreme amounts of pore spaces between mineral grains. Here, we detail our efforts quantifying the nature of the pore spaces in these chondrites and we examine the implications for the structure and mechanical processing of the asteroids from which these chondrites originate. Our pore size distribution data may also provide constraints for the modeling of heat flow and shock waves within primordial chondritic parent bodies.

  13. Ordinary chondrites - Multivariate statistical analysis of trace element contents

    NASA Technical Reports Server (NTRS)

    Lipschutz, Michael E.; Samuels, Stephen M.

    1991-01-01

    The contents of mobile trace elements (Co, Au, Sb, Ga, Se, Rb, Cs, Te, Bi, Ag, In, Tl, Zn, and Cd) in Antarctic and non-Antarctic populations of H4-6 and L4-6 chondrites, were compared using standard multivariate discriminant functions borrowed from linear discriminant analysis and logistic regression. A nonstandard randomization-simulation method was developed, making it possible to carry out probability assignments on a distribution-free basis. Compositional differences were found both between the Antarctic and non-Antarctic H4-6 chondrite populations and between two L4-6 chondrite populations. It is shown that, for various types of meteorites (in particular, for the H4-6 chondrites), the Antarctic/non-Antarctic compositional difference is due to preterrestrial differences in the genesis of their parent materials.

  14. Non-Destructive Classification Approaches for Equilibrated Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Righter, K.; Harrington, R.; Schroeder, C.; Morris, R. V.

    2013-09-01

    In order to compare a few non-destructive classification techniques with the standard approaches, we have characterized a group of chondrites from the Larkman Nunatak region using magnetic susceptibility and Mössbauer spectroscopy.

  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. Bleached chondrules: Evidence for widespread aqueous processes on the parent asteroids of ordinary chondrites

    USGS Publications Warehouse

    Grossman, J.N.; Alexander, C.M. O'D.; Wang, Jingyuan; Brearley, A.J.

    2000-01-01

    We present the first detailed study of a population of texturally distinct chondrules 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' chondrules, which are exclusively radial pyroxene and cryptocrystalline in texture, have porous outer zones where mesostasis has been lost. Bleached chondrules 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 chondrules in a cross section of ordinary chondrites. We studied bleached chondrules from Semarkona by ion microprobe for trace elements and H isotopes, and by transmission electron microscopy. Chondrule 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-chondrule reaction. The mineralogy of bleached chondrules 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 chondrules 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 chondrules were certainly open systems in all chondrites that experienced aqueous alteration leading to bleaching.

  17. The Cooling History and Structure of the Ordinary Chondrite Parent Bodies

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    Most major meteorite classes exhibit significant ranges of metamorphism. The effects of metamorphism have been extensively characterized, but the heat source(s) and the metamorphic environment are unknown. Proposed beat sources include Al-26, Fe-60, electromagnetic induction, and impact. It is typically assumed that metamorphism occurred in parent bodies of some sort, but it uncertain whether these bodies were highly structured ("onion skins") or were chaotic mixes of material ("rubble piles"). The lack of simple trends of metallographic cooling rates with petrologic type has been considered supportive of both concepts. In this study, we use induced thermoluminescence (TL) as an indicator of thermal history. The TL of ordinary chondrites is produced by sodic feldspar, and the induced TL peak temperature is related to its crystallographic order/disorder. Ordered feldspar has TL peak temperatures of approx. 120 C, and disordered feldspar has TL peak temperatures of approx. 220 C. While ordered feldspar can be easily disordered in the laboratory by heating above 650 C and is easily quenched in the disordered form, producing ordered feldspar requires cooling at geologic cooling rates. We have measured the induced TL properties of 101 equilibrated ordinary chondrites, including 49 H, 29 L, and 23 LL chondrites. For the H chondrites there is an apparent trend of decreasing induced TL peak temperature with increasing petrologic type. H4 chondrites exhibit a tight range of TL peak temperatures, 190 C - 200 C, while H6 chondrites exhibit TL peak temperatures between 180 C and 190 C. H5 chondrites cover the range between H4 and H6, and also extend up to 210 C. Similar results are obtained for LL chondfiles and most L6 chondrites have lower induced TL peak temperatures than L5 chondrites.

  18. Hysteresis properties of ordinary chondrites and implications for their thermal history

    NASA Astrophysics Data System (ADS)

    Gattacceca, J.; Suavet, C. R.; Rochette, P.; Weiss, B. P.; Winklhofer, M.; Uehara, M.; Friedrich, J. M.

    2013-12-01

    We present a large dataset of magnetic hysteresis properties of ordinary chondrite falls. We show that hysteresis properties are distinctive of individual meteorites while homogeneous among meteorite subsamples. Except for the most primitive chondrites, these properties can be explained by a mixture of multidomain kamacite and tetrataenite (both in the cloudy zone and as larger grains in plessite and in the rim of zoned taenite). Kamacite dominates the induced magnetism whereas tetrataenite dominates the remanent magnetism, in agreement with previous microscopic magnetic observations. Type 5 and 6 chondrites have higher tetrataenite content than type 4 chondrites, suggesting they have lower cooling rates at least in the 650-450 °C interval, consistent with an onion-shell model. In equilibrated chondrites, shock-related transient heating events above ~500 °C result in the disordering of tetrataenite and associated drastic change in magnetic properties. As a good indicator of the amount of tetrataenite, hysteresis properties are a very sensitive proxy of the thermal history of ordinary chondrites, revealing low cooling rates during thermal metamorphism, and high cooling rates following shock reheating or excavation after thermal metamorphism.

  19. Partial melting of ordinary chondrites: Lost City (H) and St. Severin (LL)

    NASA Technical Reports Server (NTRS)

    Jurewicz, Amy J. G.; Jones, John H.; Weber, Egon T.; Mittlefehldt, David W.

    1993-01-01

    Eucrites and diogenites are examples of asteroidal basalts and orthopyroxenites, respectively. As they are found intermingled in howardites, which are inferred to be regolith breccias, eucrites and diogenites are thought to be genetically related. But the details of this relationship and of their individual origins remain controversial. Work by Jurewicz et al. showed that 1170-1180 C partial melts of the (anhydrous) Murchison (CM) chondrite have major element compositions extremely similar to primitive eucrites, such as Sioux County. However, the MnO contents of these melts were about half that of Sioux County, a problem for the simple partial melting model. In addition, partial melting of Murchison could not produce diogenites, because residual pyroxenes in the Murchison experiments were too Fe- and Ca-rich and were minor phases at all but the lowest temperatures. A parent magma for diogenites needs an expanded low-calcium pyroxene field. In their partial melting study of an L6 chondrite, Kushiro and Mysen found that ordinary chondrites did have an expanded low-Ca pyroxene field over that of CV chondrites (i.e., Allende), probably because ordinary chondrites have lower Mg/Si ratios. This study expands that of both Kushiro and Mysen and Jurewicz et al. to the Lost City (H) and St. Severin (LL) chondrites at temperatures ranging from 1170 to 1325 C, at an fO2 of one log unit below the iron-wuestite buffer (IW-1).

  20. Minor Element Evidence that Asteroid 433 Eros is a Space-weathered Ordinary Chondrite Parent Body

    E-print Network

    Nittler, Larry R.

    . Trombka3 1 Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road Magnetism Carnegie Institution of Washington 5241 Broad Branch Road, NW Washington DC, 20015-1305 USA lrn abundant in the inner asteroid belt, are the source of ordinary chondrites, the most abundant meteorites

  1. ALUMINUM-, CALCIUM-AND TITANIUM-RICH OXIDE STARDUST IN ORDINARY CHONDRITE METEORITES

    E-print Network

    ALUMINUM-, CALCIUM- AND TITANIUM-RICH OXIDE STARDUST IN ORDINARY CHONDRITE METEORITES Larry R stars and supernovae. The isotopic and elemental compositions of the grains, as well as their microstructures, provide a great deal of information on astrophysical processes, including Galactic chem- ical

  2. Effects of Metamorphism on the Valence and Coordination of Titanium in Ordinary Chondrites

    SciTech Connect

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

    2012-04-02

    Despite years of study, the conditions under which ordinary chondrites were metamorphosed from grade 3 to grade 6 are not well defined. Wide ranges of peak temperature are inferred for each grade. The long-popular 'onion shell' model, in which higher metamorphic grade is attributed to greater depths of origin, implies a corresponding decrease in cooling rate with increasing grade, and there is disagreement as to whether or not this is observed. Redox conditions during chondrite metamorphism are also not well understood. Some workers have reported evidence for reduction, presumably by carbon, with increase in grade from 3-4, followed by oxidation during metamorphism to higher grades, but other work indicates little variation in fO{sub 2} as a function of metamorphic grade. During our investigation of the valence of Ti in planetary materials, we found high proportions of Ti{sup 3+} in olivine and pyroxene in chondrules in Semarkona (LL3.0) and low proportions in New Concord (L6) olivine, suggesting that Ti was oxidized during ordinary chondrite metamorphism. We have undertaken a study of L and LL chondrites of grades 3-6 to see how Ti valence and coordination vary with grade and to see if the variations can be used to constrain conditions of chondrite metamorphism.

  3. Non-Destructive Classification Approaches for Equilbrated Ordinary Chondrites

    NASA Technical Reports Server (NTRS)

    Righter, K.; Harrington, R.; Schroeder, C.; Morris, R. V.

    2013-01-01

    Classification of meteorites is most effectively carried out by petrographic and mineralogic studies of thin sections, but a rapid and accurate classification technique for the many samples collected in dense collection areas (hot and cold deserts) is of great interest. Oil immersion techniques have been used to classify a large proportion of the US Antarctic meteorite collections since the mid-1980s [1]. This approach has allowed rapid characterization of thousands of samples over time, but nonetheless utilizes a piece of the sample that has been ground to grains or a powder. In order to compare a few non-destructive techniques with the standard approaches, we have characterized a group of chondrites from the Larkman Nunatak region using magnetic susceptibility and Moessbauer spectroscopy.

  4. Carbon-rich aggregates in type 3 ordinary chondrites - Characterization, origins, and thermal history

    NASA Astrophysics Data System (ADS)

    Brearley, A. J.

    1990-03-01

    Carbon-rich aggregates from three type 3.4-3.6 ordinary chondrites and two chondritic clasts have been characterized in detail, using TEM techniques. The aggregates in all the meteorites studied range in size from 5-1000 microns and consist of a fine scale intergrowth of poorly graphitized carbon, amorphous carbon, Fe,Ni metal, and minor chromite. Contrary to previous reports, well-crystallized graphite and magnetite are absent. The association of Fe,Ni metal and carbonaceous material suggests that the original carbonaceous material may have formed by Fischer-Tropsch (FT) type reactions at low temperatures (less than 400 K), possibly in the solar nebula. This carbonaceous material probably consisted of a complex mixture of hydrocarbons, kerogen-like material, and other complex organic molecules. The aggregates were subsequently accreted onto the ordinary chondrite parent bodies and underwent planetary thermal processing which resulted in the catalytic graphitization of hydrocarbons, in the presence of Fe,Ni metal, to produce poorly graphitized carbon. None of the meteorites studied experienced temperatures sufficiently high to produce crystalline, ordered graphite. Using the empirical geothermometer of Rietmeijer and Mackinnon (1985), the measured d(002) spacings of poorly graphitized carbon show that graphitization occurred at temperatures between 300 and 450 C. This range of temperatures is significantly lower than the generally quoted metamorphic temperatures for type 3.4-3.6 ordinary chondrites (about 450-500 C).

  5. Early aqueous activity on the ordinary and carbonaceous chondrite parent bodies recorded by fayalite

    NASA Astrophysics Data System (ADS)

    Doyle, Patricia M.; Jogo, Kaori; Nagashima, Kazuhide; Krot, Alexander N.; Wakita, Shigeru; Ciesla, Fred J.; Hutcheon, Ian D.

    2015-06-01

    Chronology of aqueous activity on chondrite parent bodies constrains their accretion times and thermal histories. Radiometric 53Mn-53Cr dating has been successfully applied to aqueously formed carbonates in CM carbonaceous chondrites. Owing to the absence of carbonates in ordinary (H, L and LL), and CV and CO carbonaceous chondrites, and the lack of proper standards, there are no reliable ages of aqueous activity on their parent bodies. Here we report the first 53Mn-53Cr ages of aqueously formed fayalite in the L3 chondrite Elephant Moraine 90161 as Myr after calcium-aluminium-rich inclusions (CAIs), the oldest Solar System solids. In addition, measurements using our synthesized fayalite standard show that fayalite in the CV3 chondrite Asuka 881317 and CO3-like chondrite MacAlpine Hills 88107 formed and Myr after CAIs, respectively. Thermal modelling, combined with the inferred conditions (temperature and water/rock ratio) and 53Mn-53Cr ages of aqueous alteration, suggests accretion of the L, CV and CO parent bodies ~1.8-2.5 Myr after CAIs.

  6. Early aqueous activity on the ordinary and carbonaceous chondrite parent bodies recorded by fayalite.

    PubMed

    Doyle, Patricia M; Jogo, Kaori; Nagashima, Kazuhide; Krot, Alexander N; Wakita, Shigeru; Ciesla, Fred J; Hutcheon, Ian D

    2015-01-01

    Chronology of aqueous activity on chondrite parent bodies constrains their accretion times and thermal histories. Radiometric (53)Mn-(53)Cr dating has been successfully applied to aqueously formed carbonates in CM carbonaceous chondrites. Owing to the absence of carbonates in ordinary (H, L and LL), and CV and CO carbonaceous chondrites, and the lack of proper standards, there are no reliable ages of aqueous activity on their parent bodies. Here we report the first (53)Mn-(53)Cr ages of aqueously formed fayalite in the L3 chondrite Elephant Moraine 90161 as Myr after calcium-aluminium-rich inclusions (CAIs), the oldest Solar System solids. In addition, measurements using our synthesized fayalite standard show that fayalite in the CV3 chondrite Asuka 881317 and CO3-like chondrite MacAlpine Hills 88107 formed and Myr after CAIs, respectively. Thermal modelling, combined with the inferred conditions (temperature and water/rock ratio) and (53)Mn-(53)Cr ages of aqueous alteration, suggests accretion of the L, CV and CO parent bodies ?1.8-2.5?Myr after CAIs. PMID:26100451

  7. The Oxygen Isotope Composition of Dark Inclusions in HEDs, Ordinary and Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Greenwood, R. C.; Zolensky, M. E.; Buchanan, P. C.; Franchi, I. A.

    2015-01-01

    Dark inclusions (DIs) are lithic fragments that form a volumetrically small, but important, component in carbonaceous chondrites. Carbonaceous clasts similar to DIs are also found in some ordinary chondrites and HEDs. DIs are of particular interest because they provide a record of nebular and planetary processes distinct from that of their host meteorite. DIs may be representative of the material that delivered water and other volatiles to early Earth as a late veneer. Here we focus on the oxygen isotopic composition of DIs in a variety of settings with the aim of understanding their formational history and relationship to the enclosing host meteorite.

  8. Composition and formation of metal nodules and veins in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Widom, E.; Rubin, A. E.; Wasson, J. T.

    1986-01-01

    Five large metal nodules, a composite sample of five small metal nodules, one troilite nodule, and two metal veins from five ordinary chondrites were analyzed by electron microprobe and neutron activation analysis. Metal nodules and veins in H chondrites generally consist of large single crystals of kamacite, whereas L nodules contain significant taenite. Most nodules and veins are depleted by large factors ranging up to 240 in refractory siderophiles (Re, Os, Ir, Pt). Tungsten (normally a refractory siderophile) and Au, As, and Ga (volatile siderophiles) have abundance ratios similar to those of the common siderophiles Fe, Co and Ni. It is proposed that the metal with extremely low refractory-element contents was produced by shock-induced vaporization of chondritic material. The refractory elements condensed near the point of vaporization and were not transported with the vapor. Because the shock-generated gas was mildly oxidizing, W formed volatile oxides.

  9. Chemical zoning and homogenization of olivines in ordinary chondrites and implications for thermal histories of chondrules

    NASA Technical Reports Server (NTRS)

    Miyamoto, Masamichi; Mckay, David S.; Mckay, Gordon A.; Duke, Michael B.

    1986-01-01

    The extent and degree of homogenization of chemical zoning of olivines in type 3 ordinary chondrites is studied in order to obtain some constraints on cooling histories of chondrites. Based on Mg-Fe and CaO zoning, olivines in type 3 chondrites are classified into four types. A single chondrule usually contains olivines with the same type of zoning. Microporphyritic olivines show all four zoning types. Barred olivines usually show almost homogenized chemical zoning. The cooling rates or burial depths needed to homogenize the chemical zoning are calculated by solving the diffusion equation, using the zoning profiles as an initial condition. Mg-Fe zoning of olivine may be altered during initial cooling, whereas CaO zoning is hardly changed. Barred olivines may be homogenized during initial cooling because their size is relatively small. To simulated microporphyritic olivine chondrules, cooling from just below the liquidus at moderately high rates is preferable to cooling from above the liquidus at low rates. For postaccumulation metamorphism of type 3 chondrites to keep Mg-Fe zoning unaltered, the maximum metamorphic temperature must be less than about 400 C if cooling rates based on Fe-Ni data are assumed. Calculated cooling rates for both Fa and CaO homogenization are consistent with those by Fe-Ni data for type 4 chondrites. A hot ejecta blanket several tens of meters thick on the surface of a parent body is sufficient to homogenize Mg-Fe zoning if the temperature of the blanket is 600-700 C. Burial depths for petrologic types of ordinary chondrites in a parent body heated by Al-26 are broadly consistent with those previously proposed.

  10. Ordinary chondrite metallography: Part 1 Fe-Ni taenite cooling experiments

    NASA Astrophysics Data System (ADS)

    Reisener, R. J.; Goldstein, J. I.

    2003-11-01

    Cooling rate experiments were performed on P-free Fe-Ni alloys that are compositionally similar to ordinary chondrite metal to study the taenite taenite + kamacite reaction. The role of taenite grain boundaries and the effect of adding Co and S to Fe-Ni alloys were investigated. In P-free alloys, kamacite nucleates at taenite/taenite grain boundaries, taenite triple junctions, and taenite grain corners. Grain boundary diffusion enables growth of kamacite grain boundary precipitates into one of the parent taenite grains. Likely, grain boundary nucleation and grain boundary diffusion are the applicable mechanisms for the development of the microstructure of much of the metal in ordinary chondrites. No intragranular (matrix) kamacite precipitates are observed in P-free Fe-Ni alloys. The absence of intragranular kamacite indicates that P-free, monocrystalline taenite particles will transform to martensite upon cooling. This transformation process could explain the metallography of zoneless plessite particles observed in H and L chondrites. In P-bearing Fe-Ni alloys and iron meteorites, kamacite precipitates can nucleate both on taenite grain boundaries and intragranularly as Widmanstatten kamacite plates. Therefore, P-free chondritic metal and P-bearing iron meteorite/ pallasite metal are controlled by different chemical systems and different types of taenite transformation processes.

  11. Experimental Space Weathering of Ordinary Chondrites by Nanopulse Laser: TEM Results

    NASA Technical Reports Server (NTRS)

    Noble, S. K.; Hiroi, T.; Keller, L. P.; Pieters, C. M.

    2011-01-01

    A set of ordinary chondrite meteorites has been subjected to artificial space weathering by nanopulse laser to simulate the effects of micrometeorite bombardment. Three meteorites, an H (Ehole), L (Chateau Renard - CR), and LL (Appley Bridge - AB) were lasered following the method of Sasaki et al [1]. Near IR spectra were taken before and after exposure to examine the optical changes induced and the samples were examined by scanning and transmission electron microscopy (SEM and TEM) to understand the physical changes.

  12. doi:10.1016/j.gca.2004.11.024 An ordinary chondrite impactor for the Popigai crater, Siberia

    E-print Network

    Claeys, Philippe

    doi:10.1016/j.gca.2004.11.024 An ordinary chondrite impactor for the Popigai crater, Siberia ROALD in Northern Siberia is the largest crater known in the Cenozoic. The concentrations in platinum group elements

  13. A new LL3 chondrite, Allan Hills A79003, and observations on matrices in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Taylor, G. J.; Maggiore, P.

    1982-01-01

    Allan Hills A79003 is an LL3 chondrite with a petrologic subtype of 3.4 + or - 0.2. Contrary to previous suggestions, it is not paired with other Allan Hills specimens. It contains haxonite, (Fe,Ni)23C6; shock-melted, 'fizzed' metal-troilite intergrowths; and translucent, glassy-looking Huss matrix (fine-grained, Fe-rich silicate matrix), in addition to the normal opaque and recrystallized varieties of Huss matrix. Some chondrules are partly coated with opaque matrix, others with translucent matrix. Translucent matrix is more uniform in composition and contains less S, CaO and FeO and more MgO than the opaque variety. Both kinds of matrix rimmed chondrules before consolidation of the meteorite.

  14. Postshock Annealing and Postannealing Shock in Equilibrated Ordinary Chondrites: Implications for the Thermal and Shock Histories of Chondritic Asteroids

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    In addition to shock effects in olivine, plagioclase, orthopyroxene and Ca-pyroxene, petrographic shock indicators in equilibrated ordinary chondrites (OC) include chromite veinlets, chromite-plagioclase assemblages, polycrystalline troilite, metallic Cu, irregularly shaped troilite grains within metallic Fe-Ni, rapidly solidified metal-sulfide intergrowths, martensite and various types of plessite, metal-sulfide veins, large metal and/or sulfide nodules, silicate melt veins, silicate darkening, low-Ca clinopyroxene, silicate melt pockets, and large regions of silicate melt. The presence of some of these indicators in every petrologic type-4 to -6 ordinary chondrite (OC) demonstrates that collisional events caused all equilibrated OC to reach shock stages S3-S6. Those type-4 to -6 OC that are classified as shock-stage S1 (on the basis of sharp optical extinction in olivine) underwent postshock annealing due to burial beneath materials heated by the impact event. Those type-4 to -6 OC that are classified S2 (on the basis of undulose extinction and lack of planar fractures in olivine) were shocked to stage S3-S6, annealed to stage S1 and then shocked again to stage S2. Some OC were probably shocked to stage 253 after annealing. It seems likely that many OC experienced multiple episodes of shock and annealing. Because 40Ar-39Ar chronological data indicate that MIL 99301 (LL6, Sl) was annealed approximately 4.26 Ga ago, presumably as a consequence of a major impact, it seems reasonable to suggest that other equilibrated S1 and S2 OC (which contain relict shock features) were also annealed by impacts. Because some type-6 S1 OC (e.g., Guarena, Kernouve, Portales Valley, all of which contain relict shock features) were annealed 4.44-4.45 Ga ago (during a period when impacts were prevalent and most OC were thermally metamorphosed), it follows that impact-induced annealing could have contributed significantly to OC thermal metamorphism.

  15. Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites.

    PubMed

    Nakamura, Tomoki; Noguchi, Takaaki; Tanaka, Masahiko; Zolensky, Michael E; Kimura, Makoto; Tsuchiyama, Akira; Nakato, Aiko; Ogami, Toshihiro; Ishida, Hatsumi; Uesugi, Masayuki; Yada, Toru; Shirai, Kei; Fujimura, Akio; Okazaki, Ryuji; Sandford, Scott A; Ishibashi, Yukihiro; Abe, Masanao; Okada, Tatsuaki; Ueno, Munetaka; Mukai, Toshifumi; Yoshikawa, Makoto; Kawaguchi, Junichiro

    2011-08-26

    The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid. PMID:21868667

  16. Raman spectroscopic study of four Spanish shocked ordinary chondrites: Cañellas, Olmedilla de Alarcón, Reliegos and Olivenza.

    PubMed

    Rull, F; Muñoz-Espadas, M J; Lunar, R; Martínez-Frías, J

    2010-07-13

    Shock metamorphism in chondritic parent bodies produces typical textures, visible under the microscope, which are a consequence of structural deformation of the crystals. Such deformations can be studied with Raman spectroscopy. The vibrational characteristics of olivines and pyroxenes, structurally deformed by weak-to-moderate shock metamorphism, have been determined on four Spanish ordinary chondrites (Cañellas, Olmedilla de Alarcón, Reliegos and Olivenza). Such deformations would affect, in principle, the band positions and widths of the Raman spectra peaks. The measured band positions and relative intensities are consistent with chemical composition for olivines and pyroxenes, but show little influence on the degree of shock. However, the full spectral band width of the silicate internal modes shows some dependence on the impact grade, which could be attributed to inhomogeneous effects produced by the impacts. PMID:20529952

  17. The Ardón L6 ordinary chondrite: A long-hidden Spanish meteorite fall

    NASA Astrophysics Data System (ADS)

    Trigo-RodríGuez, Josep M.; Llorca, Jordi; Weyrauch, Mona; Bischoff, Addi; Moyano-Cambero, Carles E.; Keil, Klaus; Laubenstein, Matthias; Pack, Andreas; Madiedo, José MaríA.; Alonso-AzcáRate, Jacinto; Riebe, My; Wieler, Rainer; Ott, Uli; Tapia, Mar; Mestres, NarcíS.

    2014-08-01

    We report and describe an L6 ordinary chondrite fall that occurred in Ardón, León province, Spain (longitude 5.5605°W, latitude 42.4364°N) on July 9th, 1931. The 5.5 g single stone was kept hidden for 83 yr by Rosa González Pérez, at the time an 11 yr old who had observed the fall and had recovered the meteorite. According to various newspaper reports, the event was widely observed in Northern Spain. Ardón is a very well-preserved, fresh, strongly metamorphosed (petrologic type 6), and weakly shocked (S3) ordinary chondrite with well-equilibrated and recrystallized minerals. The mineral compositions (olivine Fa23.7±0.3, low-Ca pyroxene Fs20.4±0.2Wo1.5±0.2, plagioclase An10.3±0.5Ab84.3±1.2), magnetic susceptibility (log ? = 4.95 ± 0.05 × 10-9 m3 kg-1), bulk density (3.49 ± 0.05 g cm-3), grain density (3.58 ± 0.05 g cm-3), and porosity (2.5 vol%) are typical for L6 chondrites. Short-lived radionuclides confirm that the meteorite constitutes a recent fall. The 21Ne and 38Ar cosmic ray exposure ages are both about 20-30 Ma, similar to values for many other L chondrites. The cosmogenic 22Ne/21Ne ratio indicates that preatmospheric Ardón was a relatively large body. The fact that the meteorite was hidden in private hands for 83 yr makes one wonder if other meteorite falls may have experienced the same fate, thus possibly explaining the anomalously low number of falls reported in continental Spain in the 20th century.

  18. Evidence for a late thermal event of unequilibrated enstatite chondrites: a Rb-Sr study of Qingzhen and Yamato 6901 (EH3) and Khairpur (EL6)

    USGS Publications Warehouse

    Torigoye, N.; Shima, M.

    1993-01-01

    The Rb-Sr whole rock and internal systematics of two EH3 chondrites, Qingzhen and Yamato 6901, and of one EL6 chondrite, Khairpur, were determined. The internal Rb-Sr systematics of the EH3 chondrites are highly disturbed. Fractions corresponding to sulfide phases show excess 87Sr, while other fractions corresponding to silicate phases produce a linear trend on a Rb-Sr evolution diagram. If these linear relations are interpreted as isochrons, the ages of the silicate phases are 2.12?? 0.23 Ga and 2.05 ??0.33 Ga with the initial Sr isotopic ratios of 0.7112 ?? 0.0018 and 0.7089 ?? 0.0032, for Qingzhen and Yamato 6901, respectively. The Rb-Sr results are interpeted as indicative of a late thermal event about 2Ga ago on the parent bodies of these EH3 chondrites. These ages agree well with previously published K-Ar ages. An older isochron age of 4.481 ?? 0.036 Ga with a low initial Sr isotopic ratio of 0.69866 ?? 0.00038 was obtained for the data from silicate fractions of Khairpur, indicating early petrological equilibrium on the parent body of EL6 chondrites. -from Authors

  19. Volatile Element Chemistry during Metamorphism of Ordinary Chondritic Material and Some of its Implications for the Composition of Asteroids

    E-print Network

    Laura Schaefer; Bruce Fegley Jr

    2008-01-07

    We used chemical equilibrium calculations to model thermal metamorphism of ordinary chondritic material as a function of temperature, pressure, and trace element abundance and use our results to discuss volatile mobilization during thermal metamorphism of ordinary chondrite parent bodies. The calculations include ~1,700 solids and gases of 40 elements. We compiled trace element abundances in H-, L-, and LL-chondrites for the elements Ag, As, Au, Bi, Cd, Cs, Cu, Ga, Ge, In, Pb, Rb, Sb, Se, Sn, Te, Tl, and Zn, and identified abundance trends as a function of petrographic type within each class. We found that abundance patterns within the H- and L- chondrites are consistent with mobilization of volatile elements in an onionshell-type parent body. LL-chondrites have more complex abundance patterns that may support a rubble-pile model for the LL-chondrite parent body. We calculated volatility sequences for the trace elements in the ordinary chondritic material, which differs significantly from the solar nebula volatility sequence.

  20. Volatile Element Chemistry during Metamorphism of Ordinary Chondritic Material and Some of its Implications for the Composition of Asteroids

    E-print Network

    Schaefer, Laura

    2008-01-01

    We used chemical equilibrium calculations to model thermal metamorphism of ordinary chondritic material as a function of temperature, pressure, and trace element abundance and use our results to discuss volatile mobilization during thermal metamorphism of ordinary chondrite parent bodies. The calculations include ~1,700 solids and gases of 40 elements. We compiled trace element abundances in H-, L-, and LL-chondrites for the elements Ag, As, Au, Bi, Cd, Cs, Cu, Ga, Ge, In, Pb, Rb, Sb, Se, Sn, Te, Tl, and Zn, and identified abundance trends as a function of petrographic type within each class. We found that abundance patterns within the H- and L- chondrites are consistent with mobilization of volatile elements in an onionshell-type parent body. LL-chondrites have more complex abundance patterns that may support a rubble-pile model for the LL-chondrite parent body. We calculated volatility sequences for the trace elements in the ordinary chondritic material, which differs significantly from the solar nebula vol...

  1. The Iodine-Xenon System in Outer and Inner Portions of Chondrules from the Unnamed Antarctic LL3 Chondrite

    NASA Technical Reports Server (NTRS)

    Meshik, A. P.; Pravdivtseva, O. V.; Hohenberg, C. M.; Amelin, Y.

    2004-01-01

    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 chondrule 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.

  2. The Cali Meteorite: Luminescence of a recently fallen H/L ordinary chondrite

    SciTech Connect

    Trigo-Rodriguez, J. M.; Llorca, J.; Sears, D. W. G.

    2009-08-17

    The Cali meteorite fall occurred on 6 July 2007 at 21h33m+-1m UTC. Some specimens were recovered just after their fall so they are extremely fresh materials. Mineral analysis and bulk chemistry revealed that the measured abundances for most elements closely match the values recorded for other ordinary chondrites classified as H/L. We present here thermoluminescence studies of this recently fallen meteorite in order to get additional information on the radiation environment, and the thermal history of this meteorite. Such information is revealed to be complementary with the range of orbital elements deduced from eyewitness reports of the fireball.

  3. The natural thermoluminescence of meteorites. V - Ordinary chondrites at the Allan Hills ice fields

    NASA Technical Reports Server (NTRS)

    Benoit, Paul H.; Sears, Hazel; Sears, Derek W. G.

    1993-01-01

    Natural thermoluminescence (TL) data have been obtained for 167 ordinary chondrites from the ice fields in the vicinity of the Allan Hills in Victoria Land, Antarctica, in order to investigate their thermal and radiation history, pairing, terrestrial age, and concentration mechanisms. Natural TL values for meteorites from the Main ice field are fairly low, while the Farwestern field shows a spread with many values 30-80 krad, suggestive of less than 150-ka terrestrial ages. There appear to be trends in TL levels within individual ice fields which are suggestive of directions of ice movement at these sites during the period of meteorite concentration. These directions seem to be confirmed by the orientations of elongation preserved in meteorite pairing groups. The proportion of meteorites with very low natural TL levels at each field is comparable to that observed at the Lewis Cliff site and for modern non-Antarctic falls and is also similar to the fraction of small perihelia orbits calculated from fireball and fall observations. Induced TL data for meteorites from the Allan Hills confirm trends which show that a select group of H chondrites from the Antarctic experienced a different extraterrestrial thermal history to that of non-Antarctic H chondrites.

  4. Petrography and Mineralogy of 18 Newly Recovered Ordinary Chondrites in China

    NASA Astrophysics Data System (ADS)

    Li, S. L.

    2015-05-01

    Petrology and mineralogy of 18 newly recovered ordinary chondrites in China are reported in this paper. Fifteen meteorites were found in Xinjiang, among which 13 meteorites were found in the Lop Nur desert, and the other 2 meteorites were found in Kumtag and Aksai Chin, respectively. Three other meteorites are observed falls in Xining, Fuhe, and Dongyang, respectively. All meteorites are equilibrated ordinary chondrites with 8 H group and 10 L group meteorites. Their petrographic types vary from 4 to 6 in the L group meteorites, with most being type 5, while all H group meteorites are classified as type 5. The features of shock metamorphism of most meteorites are moderate though a few have features of â?¥S4 stage. Most Lop Nur meteorites underwent intense weathering with only two of which have weathering degree of W1 and W2. Both Kumtag and Aksai Chin meteorite have a weathering degree of W2. The newly discovered tens of meteorites in the gobi deserts east to the Taklimakan Desert indicate that this region may become an important dense meteorite collection area in Eurasia.

  5. THE VALENCE AND COORDINATION OF Ti IN OLIVINE AND PYROXENE IN ORDINARY AND ENSTATITE CHONDRITES AS A FUNCTION OF METAMORPHIC GRADE. S. B. Simon1

    E-print Network

    AS A FUNCTION OF METAMORPHIC GRADE. S. B. Simon1 , S. R. Sutton1,2 and L. Grossman1,3 , 1 Dept. Geophysical Sci processes re- lated to chondrite metamorphism is to evaluate changes in chondrite features, such as oxidation state, as a function of metamorphic grade. It has been sug- gested that ordinary chondrites

  6. First occurrence of pyrophanite (MnTiO3) and baddeleyite (ZrO2) in an ordinary chondrite

    NASA Technical Reports Server (NTRS)

    Krot, Aleksandr N.; Rubin, Alan E.; Kononkova, Natal'ya N.

    1993-01-01

    An examination is conducted of the distinct optical and compositional zoning exhibited by a Mg-Al-chromite fragment in the Raguli H3.8 ordinary chondrite. Two end-member pyrophanite grains occur in the fragment's outer portion; this is noted to be the first occurrence of pyrophanite in conjunction with baddeleyite in an ordinary chondrite. Two alternative models are presented for the formation of the fragment: a multistage nebular melting process, and the fragment's formation on a metamorphosed parent body. The latter alternative is favored.

  7. First occurrence of pyrophanite (MnTiO3) and baddeleyite (ZrO2) in an ordinary chondrite

    NASA Astrophysics Data System (ADS)

    Krot, A. N.; Rubin, A. E.; Kononkova, N. N.

    1993-06-01

    An examination is conducted of the distinct optical and compositional zoning exhibited by a Mg-Al-chromite fragment in the Raguli H3.8 ordinary chondrite. Two end-member pyrophanite grains occur in the fragment's outer portion; this is noted to be the first occurrence of pyrophanite in conjunction with baddeleyite in an ordinary chondrite. Two alternative models are presented for the formation of the fragment: a multistage nebular melting process, and the fragment's formation on a metamorphosed parent body. The latter alternative is favored.

  8. Striking Graphite Bearing Clasts Found in Two Ordinary Chondrite Samples; NWA6169 and NWA8330

    NASA Technical Reports Server (NTRS)

    Johnson, Jessica M.; Zolensky, Michael E.; Chan, Queenie; Kring, David A.

    2015-01-01

    Meteorites play an integral role in understanding the history of the solar system. Not only can they contain some of the oldest material found in the solar system they also can contain material that is unique. Many lithologies are only found as foreign clasts within distinctly different host meteorites. In this investigation two foreign clasts within the meteorites, NWA6169 and NWA8330 were studied. The purpose of this investigation was to examine the mineralogy and petrography of the clasts within the samples. From there an identification and possible origin were to be inferred. NWA6169 is an unclassified ordinary chondrite that has a presumed petrologic type of L3. NWA8330 is a classified ordinary chondrite that has a petrologic type of LL3. Both meteorites were found to contain clasts that were similar; both modally were comprised of about 5% acicular graphite. Through SEM and Raman Spectroscopy it was found that they contained olivine, pyroxene, plagioclase, Fe-Ni sulfides, graphite, and metals. They were found to portray an igneous texture with relationships that suggest concurrent growth. Analytical microprobe results for NWA6169 revealed mineral compositions of Fa31-34, Fs23-83, and Ab7-85. For NWA8330 these were Fa28-32, Fs10-24, and Ab4-83. Only one similar material has been reported, in the L3 chondrite Krymka (Semenenko & Girich, 1995). The clast they described exhibited similar mineralogies including the unusual graphite. Krymka data displayed compositional values of Fa28.5-35.0 and Fs9-25.9. These ranges are fairly similar to that of NWA6169 and NWA8330. These samples may all be melt clasts, probably of impact origin. Two possibilities are (1) impact of a C-type asteroid onto the L chondrite parent asteroid, and (2) a piece of proto-earth ejected from the moon-forming collision event. These possibilities present abundant questions, and can be tested. The measurement of oxygen isotope compositions from the clasts should reveal the original source of the melt clasts. It may also be possible to perform Ar dating of the plagioclase present. Former analyses are now being performed.

  9. How much of the S-type asteroids are made of ordinary chondrite materials, and why are they so highly space-weathered? T. Hiroi1

    E-print Network

    Hiroi, Takahiro

    How much of the S-type asteroids are made of ordinary chondrite materials, and why are they so whether the high abundance of ordinary chondrites really reflects their abundance in the main asteroid belt. The abundant S-type asteroids and less abundant Q-type asteroids could contain significant amount

  10. The S-type asteroid ordinary chondrite controversy and discoveries by the Hayabusa mission to asteroid 25143 Itokawa. T. Hiroi1

    E-print Network

    Hiroi, Takahiro

    The S-type asteroid ­ ordinary chondrite controversy and discoveries by the Hayabusa mission to asteroid 25143 Itokawa. T. Hiroi1 , M. Abe2 , K. Kitazato2,3 , S. Abe4 , B. E. Clark5 , S. Sasaki6 , and M-standing controversy concerning the parent bodies of ordinary chondrites and the identity of the S-type asteroids

  11. DERIVING THE DISTRIBUTION OF ORDINARY CHONDRITE (H, L, LL)-LIKE MATERIALS IN ASTEROIDS FROM THEIR VISIBLE AND NEAR-INFRARED REFLECTANCE SPECTROSCOPY. T.

    E-print Network

    Hiroi, Takahiro

    DERIVING THE DISTRIBUTION OF ORDINARY CHONDRITE (H, L, LL)-LIKE MATERIALS IN ASTEROIDS FROM reflects their abundance in the main asteroid belt. The abundant S-type asteroids and less abundant Q-type asteroids could contain significant amount of ordinary chondrite materials of different degrees of thermal

  12. The Natural Thermoluminescence of Meteorites. Part 5; Ordinary Chondrites at the Allan Hills Ice Fields

    NASA Technical Reports Server (NTRS)

    Benoit, Paul H.; Sears, Hazel; Sears, Derek W. G.

    1993-01-01

    Natural thermoluminescence (TL) data have been obtained for 167 ordinary chondrites from the ice fields in the vicinity of the Allan Hills in Victoria Land, Antarctica, in order to investigate their thermal and radiation history, pairing, terrestrial age, and concentration mechanisms. Using fairly conservative criteria (including natural and induced TL, find location, and petrographic data), the 167 meteorite fragments are thought to represent a maximum of 129 separate meteorites. Natural TL values for meteorites from the Main ice field are fairly low (typically 5-30 krad, indicative of terrestrial ages of approx. 400 ka), while the Far western field shows a spread with many values 30-80 krad, suggestive of less then 150-ka terrestrial ages. There appear to be trends in TL levels within individual ice fields which are suggestive of directions of ice movement at these sites during the period of meteorite concentration. These directions seem to be confirmed by the orientations of elongation preserved in meteorite pairing groups. The proportion of meteorites with very low natural TL levels (less then 5 krad) at each field is comparable to that observed at the Lewis Cliff site and for modern non-Antarctic falls and is also similar to the fraction of small perihelia (less then 0.85 AU) orbits calculated from fireball and fall observations. Induced TL data for meteorites from the Allan Hills confirm trends observed for meteorites collected during the 1977/1978 and 1978/1979 field seasons which show that a select group of H chondrites from the Antarctic experienced a different extraterrestrial thermal history to that of non-Antarctic H chondrites.

  13. Chemical and physical studies of chondrites. X - Cathodoluminescence and phase composition studies of metamorphism and nebular processes in chondrules of type 3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Dehart, John M.; Lofgren, Gary E.; Jie, LU; Benoit, Paul H.; Sears, Derek W. G.

    1992-01-01

    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 chondrules into eight groups according to the CL of mesostasis and to certain compositional criteria and by determining the number of chondrules in these groups as a function of petrological type, it was possible to deduce genetic/evolutionary sequences of the chondrules. It is shown that there are major compositional differences in chondrules, which account for their CL properties and the chondrule groups.

  14. Cosmogenic Records in 18 Ordinary Chondrites from the Dar Al Gani Region, Libya. 2; Radionclides

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Nishiizumi, K.; Finkel, R. C.; Hillegonds, D. J.; Jull, A. J. T.; Schultz, L.

    2003-01-01

    In the past decade more than 1000 meteorites have been recovered from the Dar al Gani (DaG) plateau in the Libyan part of the Sahara. The geological setting, meteorite pairings and density are described. So far, only a few terrestrial ages are known for DaG meteorites, e.g. 60+/- 20 kyr for the DaG 476 shergottite shower and 80+/- 20 kyr for the lunar meteorite DaG 262. However, from other desert areas, such as Oman, it is known that achondrites may survive much longer than chondritic meteorites, so the ages of these two achondrites may not be representative of the majority of the DaG meteorite collection, of which more than 90% are ordinary chondrites. In this work we report concentrations of the cosmogenic radionuclides, 14C (half-life = 5,730 yr), 41Ca (1.04x10 superscript 5 yr), Cl-36 (3.01x10 superscript 5 yr), Al-26 (7.05x10 superscript 5 yr) and 10Be (1.5x10 superscript 6 yr) to determine the terrestrial ages of DaG meteorites and constrain their pre-atmospheric size and exposure history.

  15. The Danebury Iron Age meteorite—An H5 ordinary chondrite "find" from Hampshire, England

    NASA Astrophysics Data System (ADS)

    Pillinger, C. T.; Pillinger, J. M.; Johnson, D.; Greenwood, R. C.; Tindle, A. G.; Jull, A. J. T.; Allen, D. H.; Cunliffe, B.

    2014-06-01

    What remains of a 30 g sample, first recognized as a meteorite in 1989 during characterization of metalworking debris from Danebury, an Iron Age hillfort, in Hampshire, England, has been classified as an H5 ordinary chondrite. Its arrival on Earth has been dated as 2350 ± 120 yr BP, making it contemporary with the period of maximum human activity at the recovery site. Despite its considerable terrestrial residence age, the interior of the specimen is remarkably fresh with a weathering index of W1/2. There is, however, no evidence of human intervention in its preservation. Its near-pristine state is explained in terms of its serendipitous burial during the back-fill of a pit dug into chalk by prehistoric people for the storage of grain. This chance discovery has interesting ramifications for the survival of meteorites in areas having a high pH because of a natural lime content arising as a result of the local geology.

  16. The cali meteorite fell: A new H/L ordinary chondrite

    USGS Publications Warehouse

    Rodriguez, J.M.T.; Llorca, J.; Rubin, A.E.; Grossman, J.N.; Sears, D.W.G.; Naranjo, M.; Bretzius, S.; Tapia, M.; Sepulveda, M.H.G.

    2009-01-01

    The fall of the Cali meteorite took place on 6 July 2007 at 16 h 32 ?? 1 min local time (21 h 32 ?? 1 min UTC). A daylight fireball was witnessed by hundreds of people in the Cauca Valley in Colombia from which 10 meteorite samples with a total mass of 478 g were recovered near 3??24.3'N, 76??30.6'W. The fireball trajectory and radiant have been reconstructed with moderate accuracy. From the computed radiant and from considering various plausible velocities, we obtained a range of orbital solutions that suggest that the Cali progenitor meteoroid probably originated in the main asteroid belt. Based on petrography, mineral chemistry, magnetic susceptibility, fhermoluminescence, and bulk chemistry, the Cali meteorite is classified as an H/L4 ordinary chondrite breccia.

  17. EFFECTS OF METAMORPHISM ON THE VALENCE AND COORDINATION OF TITANIUM IN ORDINARY CHONDRITES. S. B. Simon1

    E-print Network

    EFFECTS OF METAMORPHISM ON THE VALENCE AND COORDINATION OF TITANIUM IN ORDINARY CHONDRITES. S. B, in which higher metamorphic grade is attributed to greater depths of origin, implies a cor- responding by oxidation during metamorphism to higher grades [3, 4], but other work [5] indicates little variation in fO2

  18. Dynamic behavior of an ordinary chondrite: The effects of microstructure on strength, failure and fragmentation

    NASA Astrophysics Data System (ADS)

    Hogan, James David; Kimberley, Jamie; Hazeli, Kavan; Plescia, Jeffrey; Ramesh, K. T.

    2015-11-01

    Knowledge of the relationships between microstructure, stress-state and failure mechanisms is important in the development and validation of numerical models simulating large-scale impact events. In this study, we investigate the effects of microstructural constituent phases and defects on the compressive and tensile strength, failure, and fragmentation of a stony meteorite (GRO 85209). In the first part of the paper we consider the effect of defects on the strength and failure. Strengths are measured and linked with detailed quantification of the important defects in this material. We use the defect statistic measurements in conjunction with our current understanding of rate-dependent strengths to discuss the uniaxial compressive strength measurements of this ordinary chondrite with those of another ordinary chondrite, with a different defect population. In the second part of the paper, we consider the effects of the microstructure and defects on the fragmentation of GRO 85209. Fragment size distributions are measured using image processing techniques and fragments were found to result from two distinct fragmentation mechanisms. The first is a mechanism that is associated with relatively smaller fragments arising from individual defect grains and the coalescence of fractures initiating from microstructure defects. This mechanism becomes more dominant as the strain-rate is increased. The second mechanism is associated with larger fragments that are polyphase and polygrain in character and is dependent on the structural failure mechanisms that are activated during load. In turn, these are dependent on (for example) the strain-rate, stress state, and specimen geometry. The implications of these results are briefly discussed in terms of regolith generation and catastrophic disruption.

  19. Chemical and physical studies of chondrites: 10. Cathodoluminescence and phase composition studies of metamorphism and nebular processes in chondrules of type 3 ordinary chondrites

    SciTech Connect

    DeHart, J.M.; Lu Jie; Benoit, P.H.; Sears, D.W.G. ); Lofgren, G.E. )

    1992-10-01

    The cathodoluminescence (CL) properties of eight type 3 ordinary chondrites and one L5 chondrite have been determined, and phenocryst and mesostasis compositions have been analyzed in the chondrules of four of them (Semarkona, type 3.0; Krymka, 3.1; Allan Hills A77214, 3.5; and Dhajala, 3.8) in order to investigate their origins and metamorphic history. In the present study, the authors discuss the CL properties of nine ordinary chondrites of a variety of petrologic types with particular emphasis on detailed studies of the compositions of the relevant phases in four of these: Semarkona (3.0), Krymka (3.1), Allan Hills A77214 (3.5), and Dhajala (3.8). They describe a means of classifying chondrules that is based on the composition of their two major components, the mesostasis and phenocrysts. The system is applicable to > 90-95% off the chondrules in a given meteorite and it describes the range of material produced by nebular material and of the effect of metamorphism on the chondrules. They also discuss the relevance of the results for the origin of the nine chondrite classes.

  20. Thermoluminescence and the shock and reheating history of meteorites. IV - The induced TL properties of type 4-6 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Haq, Munir; Hasan, Fouad A.; Sears, Derek W. G.

    1988-01-01

    The thermoluminescence (TL) properties were measured in 121 equilibrated H and L ordinary chondrites of which 33 H and 32 L were from Antarctica. It was found that the distribution of TL sensitivities for non-Antarctic L chondrites differs from that of non-Antarctic H chondrites, reflecting the well-known differences in shock history between L and H classes, the greater proportion of the former having suffered postmetamorphic shock. The data also show differences in TL sensitivity between Antarctic and non-Antarctic H chondrites, suggesting nontrivial differences in thermal history of these chondrites.

  1. Space Weathering of Ordinary Chondrite Parent Bodies, Its Impact on the Method of Distinguishing H, L, and LL Types and Implications for Itokawa Samples Returned by the Hayabusa Mission

    NASA Technical Reports Server (NTRS)

    Hiroi, T.; Sasaki, S.; Noble, S. K.; Pieters, C. M.

    2011-01-01

    As the most abundance meteorites in our collections, ordinary chondrites potentially have very important implications on the origin and formation of our Solar System. In order to map the distribution of ordinary chondrite-like asteroids through remote sensing, the space weathering effects of ordinary chondrite parent bodies must be addressed through experiments and modeling. Of particular importance is the impact on distinguishing different types (H/L/LL) of ordinary chondrites. In addition, samples of asteroid Itokawa returned by the Hayabusa spacecraft may re veal the mechanism of space weathering on an LLchondrite parent body. Results of space weathering simulations on ordinary chondrites and implications for Itokawa samples are presented here.

  2. Thursday, March 16, 2006 POSTER SESSION II: ORDINARY AND ENSTATITE CHONDRITES

    E-print Network

    Rathbun, Julie A.

    ­6 Fragmental Breccia with Huge L Chondritic Clasts [#1625] Glanerbrug is a very complex fragmental breccia and has been previously classified as an LL breccia or L/LL5 chondrite. We classify Glanerbrug as an LL4­6 fragmental breccia with huge L-chondritic clasts. Dunaway J. K. Moersch J. Taylor L. A. Petrogenesis

  3. Accretion, metamorphism, and brecciation of ordinary chondrites - Evidence from petrologic studies of meteorites from Roosevelt County, New Mexico

    NASA Technical Reports Server (NTRS)

    Scott, Edward R. D.; Taylor, G. Jeffrey; Keil, Klaus

    1986-01-01

    The olivines and pyroxenes from twenty-nine ordinary chondrites from Roosevelt County, New Mexico are examined. The mineralogical properties of the chondrites studied are described. Correlations between mineral compositions and petrologic type and between petrologic type and bulk chemistry are analyzed. It is observed that mean CaO concentrations in olivine show significant variations among equilibrated chondrites, but these are not correlated with petrologic type; the degree of heterogeneity of FeO concentrations in olivines of types 4-6 is not correlated with the degree of metamorphism; and mean FeO concentrations of silicates show average increases of 3-5 percent from type 4 to type 6 in each group.

  4. Partial melting of the St. Severin (LL) and Lost City (H) ordinary chondrites: One step backwards and two steps forward

    NASA Technical Reports Server (NTRS)

    Jurewicz, A. J. G.; Jones, J. H.; Mittlefehldt, D. W.

    1994-01-01

    This study looks at partial melting in H and LL chondrites at nearly one atmosphere of total pressure as part of a continuing study of the origins of basaltic achondrites. Previously, melting experiments on anhydrous CM and CV chondrites showed that, near its solidus, the CM chondrite produced melts having major element chemistries similar to the Sioux County eucrite; but, the pyroxenes in the residuum were too iron-rich to form diogenites. Our preliminary results from melting experiments on ordinary (H, LL) chondrites suggested that, although the melts did not look like any known eucrites, pyroxenes from these charges bracketed the compositional range of pyroxenes found in diogenites. We had used the Fe/Mg exchange coefficients calculated for olivine, pyroxene, and melt in these charges to evaluate the approach to equilibrium, which appeared to be excellent. Unfortunately, mass balance calculations later indicated to us that, unlike our CM and CV charges, the LL and H experimental charges had lost significant amounts of iron to their (Pt or PtRh) supports. Apparently, pyroxene stability in chondritic systems is quite sensitive to the amount of FeO, and it was this unrecognized change in the bulk iron content which had stabilized the high temperature, highly magnesian pyroxenes. Accordingly, this work reinvestigates the phase equilibria of ordinary chondrites, eliminating iron and nickel loss, and reports significant differences. It also looks closely at how the iron and sodium in the bulk charge affect the stability of pyroxene, and it comments on how these new results apply to the problems of diogenite and eucrite petrogenesis.

  5. A shock-metamorphic model for silicate darkening and compositionally variable plagioclase in CK and ordinary chondrites

    SciTech Connect

    Rubin, A.E. )

    1992-04-01

    Silicate darkening in ordinary chondrites (OC) is caused by tiny grains of metallic Fe-Ni and troilite occurring mainly within curvilinear trails that traverse silicate interiors and decorate or, in some cases, cut across silicate grain boundaries. Highly shocked OC tend to have greater degrees of silicate darkening than lightly shocked OC; this indicates that silicate darkening is probably a result of shock metamorphism. The low Fe-FeS eutectic temperature (988C) renders metal and troilite susceptible to melting and mobilization during shock heating. Unshocked OC tend to have plagioclase with uniform compositions; shocked OC tend to have plagioclase with more variable (albeit still stoichiometric) compositions. The low impedance of plagioclase to shock compression makes it particularly susceptible to melting and mobilization; this is consistent with the molten appearance of plagioclase in highly shocked OC (e.g., Rose City and Paragould). CK chondrites also have compositionally variable plagioclase. The common association of silicate darkening with compositionally variable plagioclase is consistent with the hypothesis that both are products of shock metamorphism. Some CK and OC chondrites exhibit light shock effects in olivine that are consistent with equilibrium peak shock pressures that are too low to account for the silicate darkening or opaque shock veins in these meteorites. Therefore, the olivine in these chondrites may have been annealed after intense shock produced these effects. A few CK chondrites that contain olivine with undulose or mosaic extinction (e.g., LEW87009 and EET83311) may have been shocked again, after annealing.

  6. Metamorphic effects in experimentally heated Krymka /L3/ chondrite

    NASA Technical Reports Server (NTRS)

    Mcsween, H. Y., Jr.; Taylor, L. A.; Lipschutz, M. E.

    1978-01-01

    Experimental charges of the Krymka unequilibrated ordinary chondrite heated from 500-1000 C have been examined petrographically for evidence of metamorphism. Of the petrologic criteria commonly used to distinguish types 4-6 chondrites, only changes in opaque mineral compositions are observed. Chemical and textural observations indicate development of a fine-grained intergrowth of taenite + troilite beginning at 700 C due to melting within the metal-rich portion of the Fe-Ni-S system, and minor reduction of troilite to metal, possibly through sulfur loss at higher temperatures. Overall textural integration, glass devitrification, and significant Fe-enrichment of ferromagnesian minerals are not observed because the short duration of these experiments was not sufficient for the development of other changes normally attributed to metamorphism in ordinary chondritic meteorites.

  7. Extraterrestrial chromite in latest Maastrichtian and Paleocene pelagic limestone at Gubbio, Italy: The flux of unmelted ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Cronholm, Anders; Schmitz, Birger

    The distribution of sediment-dispersed extraterrestrial (ordinary chondritic) chromite (EC) grains (>63 ?m) has been studied across the latest Maastrichtian and Paleocene in the Bottaccione Gorge section at Gubbio, Italy. This section is ideal for determining the accumulation rate of EC because of its condensed nature and well-constrained sedimentation rates. In a total of 210 kg of limestone representing eight samples of 14-28 kg distributed across 24 m of the Bottaccione section, only 6 EC grains were found (an average of 0.03 EC grains kg-1). In addition, one probable pallasitic chromite grain was found. No EC grains could be found in two samples at the Cretaceous-Tertiary (K-T) boundary, which is consistent with the K-T boundary impactor being a carbonaceous chondrite or comet low in chromite. The average influx of EC to Earth is calculated to ˜0.26 grain m-2 kyr-1. This corresponds to a total flux of ˜200 tons of extraterrestrial matter per year, compared to ˜30,000 tons per year, as estimated from Os isotopes in deep-sea sediments. The difference is explained by the EC grains representing only unmelted ordinary chondritic matter, predominantly in the size range from ˜0.1 mm to a few centimeters in diameter. Sedimentary EC grains can thus give important information on the extent to which micrometeorites and small meteorites survive the passage through the atmosphere. The average of 0.03 EC grain kg-1 in the Gubbio limestone contrasts with the up to ˜3 EC grains kg-1 in mid-Ordovician limestone that formed after the disruption of the L chondrite parent body in the asteroid belt at ˜470 Ma. The two types of limestone were deposited at about the same rate, and the difference in EC abundance gives support for an increase by two orders of magnitude in the flux of chondritic matter directly after the asteroid breakup.

  8. Using the U-Pb system's dual decay scheme towards reconstructing the thermal histories and origins of ordinary chondrites (Invited)

    NASA Astrophysics Data System (ADS)

    Blackburn, T. J.; Elkins-Tanton, L. T.; Carlson, R. W.; Alexander, C. M.; Hourigan, J. K.

    2013-12-01

    Ordinary chondrites provide a record of planetary formation through the accretion of the Solar System's earliest forming solids. Despite the critical importance these samples have for understanding Solar System history, the origin of chondrites as well as the size and histories of their parent bodies remains unclear. The antiquity of chondrules permit chondrite accretion prior to the extinction of the 26Al short-lived radionuclide and the possibility of parent body melting and differentiation due to radioactive heating. Yet this antiquity and the overall abundance of chondrites has raised questions concerning the origin of chondrules and the conditions leading to the preservation of their primordial geochemical signatures, accretion textures and ancient inclusions. In short, if these bodies accreted early in the history of the solar system, how has this material avoided melting by radioactive heating? Different models for the size and structure of the chondrite parent bodies as well as for chondrule formation exist to explain how chondrites survive or avoid early radiogenic heating. Here we propose to evaluate these scenarios through comparison between modeled thermal histories and thermal histories reconstructed using U-Pb thermochronology of chondritic phosphates. Detailed thermal histories are reconstructed by exploiting the U-Pb system's dual decay scheme, where two parent isotopes, 238U and 235U, decay to two daughter isotopes 206Pb and 207Pb respectively. The difference in decay rates between parent isotopes imposes a time-variant parent and instantaneous daughter isotopic composition for any point in Solar System history. This new thermochronologic methodology works to capture this isotopic evolution using the variation in the time of Pb retention between both: 1) chondrites from different parent body depths or metamorphic grades, where variations in the timescale of cooling result from the thermal gradient within a conductively cooling body, and; 2) crystals of different size, where volume diffusion behavior, in particular for slowly cooled systems, result in larger crystals retaining Pb at higher temperatures and over longer and older timescales in comparison to smaller crystals. The differences in 207Pb/206Pb among samples from different depths and within each sample--between grains of different size -- can be used to reconstruct the long-term chondrite thermal histories. Here we will present 207Pb-206Pb data for phosphates from over 10 ordinary chondrites with samples from: 1) H, L and LL chondrites, 2) metamorphic grades Type 4-6, and 3) a range of shock grades. Preliminary phosphate (U-Th)/He data from the same samples provide a means to understand whether the U-Pb system has been influenced by subsequent heating events. The combined data are used to constrain parent body thermal histories--and in doing so constrain the size and structure of the chondrite parent bodies.

  9. Deformation and thermal histories of ordinary chondrites: Evidence for post-deformation annealing and syn-metamorphic shock

    NASA Astrophysics Data System (ADS)

    Ruzicka, Alex; Hugo, Richard; Hutson, Melinda

    2015-08-01

    We show that olivine microstructures in seven metamorphosed ordinary chondrites of different groups studied with optical and transmission electron microscopy can be used to evaluate the post-deformation cooling setting of the meteorites, and to discriminate between collisions affecting cold and warm parent bodies. The L6 chondrites Park (shock stage S1), Bruderheim (S4), Leedey (S4), and Morrow County (S5) were affected by variable shock deformation followed by relatively rapid cooling, and probably cooled as fragments liberated by impact in near-surface settings. In contrast, Kernouvé (H6 S1), Portales Valley (H6/7 S1), and MIL 99301 (LL6 S1) appear to have cooled slowly after shock, probably by deep burial in warm materials. In these chondrites, post-deformation annealing lowered apparent optical strain levels in olivine. Additionally, Kernouvé, Morrow County, Park, MIL 99301, and possibly Portales Valley, show evidence for having been deformed at an elevated temperature (?800-1000 °C). The high temperatures for Morrow County can be explained by dynamic heating during intense shock, but Kernouvé, Park, and MIL 99301 were probably shocked while the H, L and LL parent bodies were warm, during early, endogenically-driven thermal metamorphism. Thus, whereas the S4 and S5 chondrites experienced purely shock-induced heating and cooling, all the S1 chondrites examined show evidence for static heating consistent with either syn-metamorphic shock (Kernouvé, MIL 99301, Park), post-deformation burial in warm materials (Kernouvé, MIL 99301, Portales Valley), or both. The results show the pitfalls in relying on optical shock classification alone to infer an absence of shock and to construct cooling stratigraphy models for parent bodies. Moreover, they provide support for the idea that "secondary" metamorphic and "tertiary" shock processes overlapped in time shortly after the accretion of chondritic planetesimals, and that impacts into warm asteroidal bodies were common.

  10. A search for subkilometer-sized ordinary chondrite like asteroids in the main-belt

    NASA Astrophysics Data System (ADS)

    Lin, H. W.; Yoshida, Fumi; Chen, Y. T.; Ip, W. H.; Chang, C. K.

    2015-07-01

    The size-dependent effects of asteroids on surface regolith and collisional lifetimes suggest that small asteroids are younger than large asteroids. In this study, we performed multicolor main-belt asteroid (MBA) survey by Subaru telescope/Suprime-Cam to search for subkilometer-sized ordinary chondrite (Q-type) like MBAs. The total survey area was 1.5 deg2 near ecliptic plane and close to the opposition. We detected 150 MBAs with 4 bands (B, V, R, I) in this survey. The range of absolute magnitude of detected asteroids was between 13 and 22 magnitude, which is equivalent to the size range of kilometer to sub-kilometer diameter in MBAs. From this observation, 75 of 150 MBAs with color uncertainty less than 0.1 were used in the spectral type analysis, and two possible Q-type asteroids were detected. This mean that the Q-type to S-type ratio in MBAs is <0.05. Meanwhile, the Q/S ratio in near Earth asteroids (NEAs) has been estimated to be 0.5-2 (Binzel, R.P. et al. [2004]. Icarus 107, 259-224; Dandy, C.L., Fitzsimmins, A., Collander-Brown, S.J. [2003]. Icarus 163, 363-373). Therefore, Q-type NEAs might be delivered from the main belt region with weathered, S-type surface into near Earth region and then obtain their Q-type, non-weathered surface after undergoing re-surfacing process there. The resurfacing mechanisms could be: 1. dispersal of surface material by tidal effect during planetary encounters (Binzel, R.P. et al. [2010]. Nature 463, 331-334; Nesvorný, D. et al. [2010]. Icarus 209, 510-519), 2. the YORP spin-up induced rotational-fission (Polishook, D. et al. [2014]. Icarus 233, 9-26) or surface re-arrangement, or 3. thermal degradation (Delbo, M. et al. [2014]. Nature 508, 233-236).

  11. Thursday, March 26, 2009 POSTER SESSION II: CHONDRITES, THEIR CLASTS, AND ALTERATION

    E-print Network

    Rathbun, Julie A.

    . The Highly Unequilibrated EH Chondrite, Sahara 97072, May Be a Primitive Breccia [#2154] We have investigated a breccia lump in the unequilibrated enstatite chondrite Sahara 97072, which we interpret to be a primitive breccia. Macke R. J. Britt D. T. Consolmagno G. J. Enstatite Chondrite Physical Properties: Density

  12. Northwest Africa 8709: A Rare but Revealing Type 3 Ordinary Chondrite Melt Breccia

    NASA Astrophysics Data System (ADS)

    Ruzicka, A. M.; Hutson, M.; Friedrich, J. M.; Bland, P. A.; Pugh, R.

    2015-07-01

    We discuss the discovery of a rare L3 melt breccia, which has implications for compaction processes that must have contributed to the lithification of what are expected to have been initially porous primordial chondritic agglomerates.

  13. Chemical and physical studies of type 3 chondrites. II Thermoluminescence of sixteen type 3 ordinary chondrites and relationships with oxygen isotopes

    NASA Technical Reports Server (NTRS)

    Sears, D. W. G.; Weeks, K. S.

    1983-01-01

    Thermoluminescence (TL) sensitivity values for sixteen type 3 ordinary chondrites, fourteen of them from Antarctica, have been measured. The values obtained (normalized to the TL sensitivity of the Dhajala meteorite) range from 1.6 (Allan Hills A77216) to 0.010 (Allan Hills A77176), and include two (Reckling Peak A80207 and Allan Hills A77176) that are particularly low. They fill a hiatus in the TL distribution that previously existed between St. Mary's County and Bishunpur, the latter being a meteorite with one of the lowest TL sensitivities known. The histogram of TL sensitivity values now shows a single distribution with higher values preferred; it resembles the histogram for L chondrites occupying the petrologic types 3, 4, 5, and 6. There is a tendency for the TL sensitivity of meteorites to decrease as delta O-18 increases. Theoretically, it is possible that the range of delta O-18 values observed may reflect progressive loss of O in the form of CO at very low temperatures, but very restrictive physical conditions and a complex history seem to be required.

  14. Magnetic properties of the LL5 ordinary chondrite Chelyabinsk (fall of February 15, 2013)

    NASA Astrophysics Data System (ADS)

    Bezaeva, Natalia S.; Badyukov, Dmitry D.; Nazarov, Mikhail A.; Rochette, Pierre; Feinberg, Joshua M.; Markov, Gennadiy P.; Borschneck, Daniel; Demory, FrançOis; Gattacceca, JéRôMe; Borisovskiy, Sergey E.; Skripnik, Anna Ya

    2014-06-01

    Here we characterize the magnetic properties of the Chelyabinsk chondrite (LL5, S4, W0) and constrain the composition, concentration, grain size distribution, and mineral fabric of the meteorite's magnetic mineral assemblage. Data were collected from 10 to 1073 K and include measurements of low-field magnetic susceptibility (?0), the anisotropy of ?0, hysteresis loops, first-order reversal curves, Mössbauer spectroscopy, and X-ray microtomography. The REM and REM' paleointensity protocols suggest that the only magnetizations recorded by the chondrite are components of the Earth's magnetic field acquired during entry into our planet's atmosphere. The Chelyabinsk chondrite consists of light and dark lithologies. Fragments of the light lithology show log?0 = 4.57 ± 0.09 (s.d.) (n = 135), while the dark lithology shows 4.65 ± 0.09 (n = 39) (where ?0 is in 10-9 m3 kg-1). Thus, Chelyabinsk is three times more magnetic than the average LL5 fall, but is similar to a subgroup of metal-rich LL5 chondrites (Paragould, Aldsworth, Bawku, Richmond) and L/LL5 chondrites (Glanerbrug, Knyahinya). The meteorite's room-temperature magnetization is dominated by multidomain FeNi alloys taenite and kamacite (no tetrataenite is present). However, below approximately 75 K remanence is dominated by chromite. The metal contents of the light and dark lithologies are 3.7 and 4.1 wt%, respectively, and are based on values of saturation magnetization.

  15. Collision of cometlike and slightly differentiated bodies as an origin for ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Kitamura, M.; Tsuchiyama, A.

    1994-01-01

    One of the keys to understanding the origins of chondrites is given by the characteristics of relict minerals in chondrules that survived chondrule formation. Some of the relic materials show shock deformation textures, such as high dislocation densities in relict olivine and stacking faults in relict pyroxene. The textures suggest that shock deformation was the cause of melting of the chondrules. Some of the olivine and pyroxene fragments in the matrix of the chondrites have been shown to have a composition closer to the relict minerals than minerals crystallized during the chondrule formation. This suggests that some of the fragments originated from the precursor materials of the chondrules. A proposed origin for chondrites is discussed here along with supporting observations and conclusions.

  16. The thermoluminescence sensitivity-metamorphism relationship in ordinary chondrites - Experimental data on the mechanism and implications for terrestrial systems

    NASA Technical Reports Server (NTRS)

    Guimon, R. K.; Sears, D. W. G.; Lofgren, G. E.

    1986-01-01

    Hydrothermal annealing experiments have been performed on samples of the Sharps meteorite in order to investigate the mechanism responsible for the metamorphism-related, 10-to-the-5th-fold range in the thermoluminescence (TL) sensitivity in ordinary chondrites. Duplicate 50 mg samples of meteorite were annealed under the following conditions: (1) 168 h at 785 C and 1 kbar; (2) the same time, temperature and pressure, but with 2 wt pct water; (3) 174 h at 855 C and 0.77 kbar with 2 wt pct water and 2 molal sodium disilicate (NadiSi); (4) the same time, temperature and pressure as the preceding samples, but with 10 wt pct H2O and 2 molal NadiSi. Samples annealed under the first three sets of conditions showed little or no change in their TL sensitivities, however the samples annealed with 10 wt pct water and 2 molal NadiSi showed a three-fold to 10-fold increase in TL sensitivity, and the temperature of the TL peak was suggestive of feldspar in the high-temperature form. It is suggested that these data are consistent with the TL sensitivity-metamorphism relationship in ordinary chondrites being due to the formation of the TL phosphor, feldspar, by the crystallization of chondrule glass.

  17. Complex zoning behavior in pyroxene in FeO-rich chondrules in the Semarkona ordinary chondrite

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.; Papike, J. J.

    1993-01-01

    A detailed understanding of the properties of silicate minerals in chondrules is essential to the interpretation of chondrule formation conditions. This study is further work in a series of petrologic studies of chondrules in the least equilibrated LL chondrite, Semarkona (LL3.0). The objectives of this work are as follows: (1) to understand chondrule formation conditions and nebular processes; and (2) to use the data as a basis for understanding the effects of metamorphism in more equilibrated chondrites. FeO-rich pyroxene in the chondrules described shows complex zoning behavior. Low-Ca clinopyroxene, orthopyroxene, pigeonite, and augite are all observed, in various associations with one another. Coexisting olivine phenocrysts are also FeO-rich and strongly zoned. Compositional and zoning properties are similar to those observed in boninites and are interpreted as resulting from rapid cooling of individual chondrules.

  18. Radial Heterogeneity of 53-Mn in the Early Solar System and the Place of Origin of Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Lugmair, G. W.; Shukolyukov, A.; MacIsaac, Ch.

    1996-03-01

    The earlier results of our studies of 53Mn-53Cr isotope systematics (T(sub)1/2 of 53Mn = 3.7 My) in angrites (LEW 86010, Angra dos Reis) and in some eucrites (Chervony Kut [CK], Juvinas [JI3V1) have suggested that the resolution of small age differences between these differentiated objects is possible if the assumption is true that 53Mn was homogeneously distributed at least in that region of the solar nebula where the meteorite parent bodies formed. The fact that the present day and the initial 53Cr/52Cr ratios in both meteorite classes are significantly higher than the terrestrial and lunar values led us to test the 53Mn-53Cr systematics in several ordinary chondrites, the putative building blocks of planetesimals. We found that these chondrites possess uniform and higher than terrestrial bulk 53Cr/52Cr ratios (0.5 epsilon; 1 epsilon = l x 10^-4) but more than a factor of two lower than the bulk eucrites. Thus, it became clear that the original assumption of 53Mn homogeneity on a large scale may not be valid and that the low abundance on earth of the 53Mn decay product may be the consequence of a solar system wide phenomenon rather than, say, simply depletion at 1 AU due to volatility. The idea of a radially heterogeneous 53Mn distribution in the nebula was suggested and tests of this hypothesis were undertaken.

  19. Partitioning of Nd, Tb, Lu, and Hf Between Garnet and Ordinary Chondrite Melt at 5 to 9 GPa: Applications to Martian Differentiation

    NASA Technical Reports Server (NTRS)

    Draper, D. S.; Chabot, N. L.; Xirouchakis, D.; Wasserman, A. A.; Agee, C. B.

    2001-01-01

    One explanation for Al and REE depletions in SNC meteorites is early majorite fractionation in a deep martian magma ocean. We report initial results from an experimental investigation of partitioning between majoritic garnet and ordinary chondrite liquid. Additional information is contained in the original extended abstract.

  20. An Ordinary Chondrite Impactor Composition for the Bosumtwi Impact Structure, Ghana, West Africa: Discussion of Siderophile Element Contents and Os and Cr Isotope Data

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian; Shukolyukov, Alex; Lugmair, Guenter

    2004-01-01

    Osmium isotope data had shown that Ivory Coast tektites contain an extraterrestrial component, but do not allow distinction between chondritic and iron meteorite contamination. PGE abundances of Ivory Coast tektites and impactites and target rocks from the Bosumtwi crater, the source crater of the Ivory Coast tektites, were all relatively high and did not allow to resolve the presence, or identify the nature, of the meteoritic component. However, Cr isotope analyses of an Ivory Coast tektite yielded a distinct 53Cr excess of 0.30+/-0.06, which indicates that the Bosumtwi impactor was an ordinary chondrite.

  1. The natural thermoluminescence of meteorites. 7: Ordinary chondrites from the Elephant Moraine region, Antarctica

    NASA Technical Reports Server (NTRS)

    Benoit, P. H.; Roth, J.; Sears, H.; Sears, D. W. G.

    1994-01-01

    We report natural and induced thermoluminescence (TL) measurements for meteorites from the Elephant Moraine region (76 deg 17 min S, 157 deg 20 min E) of Antarctica. We use our data to identify fragmented meteorites (i.e., 'pairings'); our dataset of 107 samples represents at most 73 separate meteorite falls. Pairing groups are generally confined to single icefields, or to adjacent icefields, but a small proportion cross widely separated icefields in the region, suggesting that the fields can be considered as a single unit. Meteorites from this region have high natural TL levels, which indicates that they have small terrestrial surface exposure ages (less than 12,500 years). There do not appear to be significant differences in natural TL levels (and hence surface exposure ages) between individual blue icefields in the region. The proportion of reheated meteorites from the Elephant Moraine region is similar to that of other Antarctic sites and modern falls, consistent with the uniformity of the meteoritic flux in this regard. An unusual subset of H-chondrites, with high induced TL peak temperatures, is absent among the data for meteorites collected in the Elephant Moraine region, which stresses their similarity to modern falls. We suggest that the Elephant Moraine region, which stresses their similarity to modern falls. We suggest that the Elephant Moraine icefields formed through shallow ablation of the ice. Unlike the Allan Hills sites to the south, lateral transport is probably less important relative to the infall of meteorites in concentrating meteorites on these icefields.

  2. Preliminary results of sulfide melt/silicate wetting experiments in a partially melted ordinary chondrite

    NASA Technical Reports Server (NTRS)

    Jurewicz, Stephen R.; Jones, John H.

    1994-01-01

    Recently, mechanisms for core formation in planetary bodies have received considerable attention. Most current theories emphasize the need for large degrees of silicate partial melting to facilitate the coalescence and sinking of sulfide-metal liquid blebs through a low strength semi-crystalline silicate mush. This scenario is based upon observations that sulfide-metal liquid tends to form circular blebs in partially molten meteorites during laboratory experiments. However, recent experimental work by Herpfer and Larimer indicates that some sulfide-Fe liquids have wetting angles at and slightly below 60 deg in an olivine aggregate, implying an interconnected melt structure at any melt fraction. Such melt interconnectivity provides a means for gravitational compaction and extraction of the majority of a sulfide liquid phase in small planetary bodies without invoking large degrees of silicate partial melting. Because of the important ramifications of these results, we conducted a series of experiments using H-chondrite starting material in order to evaluate sulfide-liquid/silicate wetting behavior in a more complex natural system.

  3. A Quantitative NMR Analysis of Phosphorus in Carbonaceous and Ordinary Chondrites

    NASA Technical Reports Server (NTRS)

    Pasek, M. A.; Smith, V. D.; Lauretta, D. S.

    2004-01-01

    Phosphorus is important in a number of biochemical molecules, from DNA to ATP. Early life may have depended on meteorites as a primary source of phosphorus as simple dissolution of crustal apatite may not produce the necessary concentration of phosphate. Phosphorus is found in several mineral phases in meteorites. Apatite and other Ca- and Mg phosphate minerals tend to be the dominant phosphorus reservoir in stony meteorites, whereas in more iron-rich or reduced meteorites, the phosphide minerals schreibersite, (Fe, Ni)3P, and perryite, (Ni, Fe)5(Si, P)2 are dominant. However, in CM chondrites that have experienced significant aqueous alteration, phosphorus has been detected in more exotic molecules. A series of phosphonic acids including methyl-, ethyl-, propyl- and butyl- phosphonic acids were observed by GC-MS in Murchison. Phosphorian sulfides are in Murchison and Murray. NMR spectrometry is capable of detecting multiple substances with one experiment, is non-destructive, and potentially quantitative, as discussed below. Despite these advantages, NMR spectrometry is infrequently applied to meteoritic studies due in large part to a lack of applicability to many compounds and the relatively high limit of detection requirements. Carbon-13 solid-state NMR has been applied to macromolecular carbon in Murchison. P-31 NMR has many advantages over aqueous carbon-13 NMR spectrometry. P-31 is the only isotope of phosphorus, and P-31 gives a signal approximately twice as strong as C-13. These two factors together with the relative abundances of carbon and phosphorus imply that phosphorus should give a signal approximately 20 as strong as carbon in a given sample. A discussion on the preparation of the quantitative standard and NMR studies are presented

  4. The thermoluminescence carrier in the Dhajala chondrite

    NASA Technical Reports Server (NTRS)

    Sparks, M. H.; Mckimmey, P. M.; Sears, D. W. G.

    1983-01-01

    It is pointed out that the type 3 (unequilibrated) ordinary chondrites provide a major source of information on the early solar system. However, the interpretation of the data is difficult because all but a few display signs of metamorphic alteration. The present investigation is concerned with the thermoluminescence (TL) sensitivity measurements on 58 chondrules separated from the Dhajala meteorites. The data were discussed briefly by Sparks and Sears (1982). In the current investigation particular attention is given to the constraints placed by these data on the mechanism by which metamorphism is related to TL sensitivity. Dhajala-normalized TL sensitivity of the separated chondrules is plotted against chondrule mass, and a histogram of the CaO contents of 15 chondrules is presented. Histograms showing the TL sensitivity of chondrules separated from the Dhajala meteorite are also provided.

  5. Fe-Ni metal and sulfide minerals in CM chondrites: An indicator for thermal history

    USGS Publications Warehouse

    Kimura, M.; Grossman, J.N.; Weisberg, M.K.

    2011-01-01

    CM chondrites were subjected to aqueous alteration and, in some cases, to secondary metamorphic heating. The effects of these processes vary widely, and have mainly been documented in silicate phases. Herein, we report the characteristic features of Fe-Ni metal and sulfide phases in 13 CM and 2 CM-related chondrites to explore the thermal history of these chondrites. The texture and compositional distribution of the metal in CM are different from those in unequilibrated ordinary and CO chondrites, but most have similarities to those in highly primitive chondrites, such as CH, CR, and Acfer 094. We classified the CM samples into three categories based on metal composition and sulfide texture. Fe-Ni metal in category A is kamacite to martensite. Category B is characterized by pyrrhotite grains always containing blebs or lamellae of pentlandite. Opaque mineral assemblages of category C are typically kamacite, Ni-Co-rich metal, and pyrrhotite. These categories are closely related to the degree of secondary heating and are not related to degree of the aqueous alteration. The characteristic features of the opaque minerals can be explained by secondary heating processes after aqueous alteration. Category A CM chondrites are unheated, whereas those in category B experienced small degrees of secondary heating. CMs in category C were subjected to the most severe secondary heating process. Thus, opaque minerals can provide constraints on the thermal history for CM chondrites. ?? The Meteoritical Society, 2011.

  6. Carbon-rich Chondritic Clast PV1 from the Plainview H-chondrite Regolith Formation from H3 Chondrite Material by Possible Cometary Impact

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Trigo-Rodriguez, Josep M.; Kunihiro, Takuya; Kallemeyn, Gregory W.; Wasson, John T.

    2006-01-01

    Chondritic clast PV1 from the Plainview H-chondrite regolith breccia is a subrounded, 5-mm diameter unequilibrated chondritic fragment that contains 13 wt% C occurring mainly within irregularly shaped 30-400-micron-size opaque patches. The clast formed from H3 chondrite material as indicated by the mean apparent chondrule diameter (310 micron vs. approximately 300 micron in H3 chondrites), the mean Mg-normalized refractory lithophile abundance ratio (1.00 +/- 0.09 XH), the previously determined 0-isotopic composition (Delta O-17 = 0.66% vs. 0.68 +/- 0.04%0 in H3 chondrites and 0.73 +/- 0.09% in H4-6 chondrites), the heterogeneous olivine compositions in grain cores (with a minimum range of Fal-19), and the presence of glass in some chondrules. Although the clast lacks the fine-grained, ferroan silicate matrix material present in type 3 ordinary chondrites, PV1 contains objects that appear to be recrystallized clumps of matrix material. Similarly, the apparent dearth of radial pyroxene and cryptocrystalline chondrules in PV1 is accounted for by the presence of some recrystallized fragments of these chondrule textural types. All of the chondrules in PV1 are interfused indicating that temperatures must have briefly reached approximately 1100C (the approximate solidus temperature of H-chondrite silicate). The most likely source of this heating was by an impact. Some metal was lost during impact heating as indicated by the moderately low abundance of metallic Fe-Ni in PV1 (approximately 14 wt%) compared to that in mean H chondrites (approximately 18 wt%). The carbon enrichment of the clast may have resulted from a second impact event, one involving a cometary projectile, possibly a Jupiter-family comet. As the clast cooled, it experienced hydrothermal alteration at low water/rock ratios as evidenced by the thick rims of ferroan olivine around low-FeO olivine cores. The C-rich chondritic clast was later incorporated into the H-chondrite parent-body regolith and extensively fractured and faulted.

  7. Chromite-Plagioclase Assemblages as a New Shock Indicator; Implications for the Shock and Thermal Histories of Ordinary Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    Chromite in ordinary chondrites (OC) can be used as a shock indicator. A survey of 76 equilibrated H, L and LL chondrites shows that unshocked chromite grains occur in equant, subhedral and rounded morphologies surrounded by silicate or intergrown with metallic Fe-Ni and/or troilite. Some unmelted chromite grains are fractured or crushed during whole-rock brecciation. Others are transected by opaque veins; the veins form when impacts cause localized heating of metal-troilite intergrowths above the Fe-FeS eutectic (988 C), mobilization of metal-troilite melts, and penetration of the melt into fractures in chromite grains. Chromite-plagioclase assemblages occur in nearly every shock-stage S3-S6 OC; the assemblages range in size from 20-300 microns and consist of 0.2-20-micron-size euhedral, subhedral, anhedral and rounded chromite grains surrounded by plagioclase or glass of plagioclase composition. Plagioclase has a low impedance to shock compression. Heat from shock-melted plagioclase caused adjacent chromite grains to melt; chromite grains crystallized from this melt. Those chromite grains in the assemblages that are completely surrounded by plagioclase are generally richer in Al2O3, than unmelted, matrix chromite grains in the same meteorite. Chromite veinlets (typically 0.5-2 microns thick and 10-300 microns long) occur typically in the vicinity of chromite-plagioclase assemblages. The veinlets formed from chromite-plagioclase melts that were injected into fractures in neighboring silicate grains; chromite crystallized in the fractures and the residual plagioclase-rich melt continued to flow, eventually pooling to form plagioclase-rich melt pockets. Chromite-rich chondrules (consisting mainly of olivine, plagioclase-normative mesostasis, and 5-15 vol.% chromite) occur in many shocked OC and OC regolith breccias but they are absent from primitive type-3 OC. They may have formed by impact melting chromite, plagioclase and adjacent mafic silicates during higher-energy shock events. The melt was jetted from the impact site and formed droplets due to surface tension. Crystallization of these droplets may have commenced in flight, prior to landing on the parent-body surface. Chromite-plagioclase assemblages and chromite veinlets occur in 25 out of 25 shock-stage S1 OC of petrologic type 5 and 6 that I examined. Although these rocks contain unstrained olivine with sharp optical extinction, most possess other shock indicators such as extensive silicate darkening, numerous occurrences of metallic Cu, polycrystalline troilite, and opaque veins. It seems likely that these rocks were shocked to levels at least as high as shock-stage S3 and then annealed by heat generated during the shock event. During annealing, the olivine crystal lattices healed but other shock indicators survived. Published Ar-Ar age data for some SI OC indicate that many shock and annealing events occurred very early in the history of the parent asteroids. The common occurrence of shocked and annealed OC is consistent with collisions being a major mechanism responsible for metamorphosing OC.

  8. A 3D nanoscale approach to nebular paleomagnetism in the Semarkona LL3.0 ordinary chondrite

    NASA Astrophysics Data System (ADS)

    Einsle, J. F.; Fu, R. R.; Weiss, B. P.; Kasama, T.; Midgley, P. A.; Harrison, R. J.

    2014-12-01

    Solar nebular models suggest that magnetic fields are central to the redistribution of mass and angular momentum in the protoplanetary disk. Using individual chondrules with patches of dusty olivine the strength of these magnetic fields can be measured due to presence of nanoscale Fe inclusions. Since chondrules formed by rapid heating and cooling in the early solar nebula, individual chondrules have the potential to record the magnetic field that was present during their formation, and retain this signal for several billion years. Recently the first robust paleointensity measurement of nebular fields was compleated by measureing dusty olivine grains from the Semarkona LL3.0 ordinary chondrite meteorite in a SQUID microscope. (Fu et al. this meeting) Extracting quantitative information from the paleomagnetic meaurements requires a full understanding of the underlying physical mechanisms producing the measured magnetic signal. Here we characterise the magnetic behaviour of the same dusty olivine chondrules, using a variety of electron microscopy techniques. Electron holography and Lorentz imaging confirm the dominance of single vortex (SV) states in the majority of the remanence carriers. In-field measurements demonstrate the high stability of this SV state, making them suitable carriers of paleomagnetic information. We present a 3D volume reconstruction of the dusty olivine using Focussed-Ion-Beam (FIB) slice-and-view tomography. Combining the selective milling properties of FIB with the high spatial resolution of the Scanning Electron Microscope we are able to capture images as we make successive slices through a selected region of the sample. For this initial study we present a collection of 400 images taken every 10 nm as we slice through an 10 ?m x 10 ?m x 4 ?m volume of the dusty olivine patch within a single chondrule. Each image possesses resolution around 10 nm allowing us to resolve particles in both the single domain and single vortex size ranges. Once assembled the full data provies quantitative statistics on particle-size distribution, shapes and interparticle spacing. The information is then used to model the macroscopic paleomagnetic properties. This work further extends the central role of electron microscopy in determining the underlying physics of the remanence acquisition process.

  9. The Portales Valley meteorite breccia: evidence for impact-induced melting and metamorphism of an ordinary chondrite

    NASA Astrophysics Data System (ADS)

    Rubin, Alan E.; Ulff-Møller, Finn; Wasson, John T.; Carlson, William D.

    2001-01-01

    The Portales Valley H-chondrite fall is an annealed impact-melt breccia with coarse metal interstitial to angular and subrounded silicate clasts. The large metal-rich regions exhibit a Widmanstätten structure and contain very little troilite. We were able to examine a 16.5 kg metal-rich specimen of Portales Valley. Silicates contain numerous flecks of metallic Cu and curvilinear trails of tiny metallic Fe-Ni blebs, characteristic of shocked and annealed chondrites. One silicate clast appears to have experienced little (<10%) or no melting; it is essentially identical to normal H6 chondrites. Other clasts are finer grained and have a low abundance of recognizable relict chondrules; they are significantly enriched in troilite and depleted in metallic Fe-Ni relative to typical H chondrites. Their low metal abundance indicates that they are not simply ultra-recrystallized H6 chondrites. If the silicates in these clasts started off as normal H-chondrite material and were recrystallized to the same extent as the progenitor of the H6-like clast, then their low modal abundance of chondrules indicates that they experienced significant crushing and/or impact melting. We infer that most of the metal and troilite was lost from these silicate clasts during impact melting; it appears that troilite was reintroduced into the silicates, perhaps by an S 2-rich vapor (that formed FeS by reacting with Fe vapor or residual metal). Portales Valley probably formed on a low-density, porous H-chondrite asteroid by a high-energy impact event that caused crushing and melting; the target material was buried deeply enough to undergo slow cooling. Meteorites that appear to have formed, at least in part, by analogous processes include IIE-an Netschaëvo and EL6 Blithfield.

  10. 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.

  11. Comparison of Nickel XANES Spectra and Elemental Maps from a Ureilite, a LL3.8 Ordinary Chondrite, Two Carbonaceous Chondrites and Two Large Cluster IDPs

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Sutton, S.; Zolensky, M. E.

    2014-01-01

    Nickel in the extraterrestrial world is commonly found in both Fe-Ni sulfide and Fe-Ni met-al forms [1] and in the pure metal state in the interior of iron meteorites where it is not easily oxidized. Ni is also found in olivine, pyroxene and glasses and in some melts the partitioning of Ni between the olivines and glass is controlled by the amount of S in the melt [2]. Its most common valence state is Ni(2+) but Ni also occurs as Ni(0), Ni(+), and Ni(3+) and rarely as Ni(2-), Ni(1-) and Ni(4+) [3]. It's valence state in olivines is Ni(2+) in octa-hedral coordination on the M1 site and rarely on the M2 site.[4]. The chemical sensitivity of X-ray absorp-tion near-edge structure (XANES) spectroscopy is well established and can be used to determine not only va-lence states but also coordination sites [5]. We report here Ni XANES spectroscopy and elemental maps collected from 2 carbonaceous chondrites, 2 large clus-ter IDPs, 1 ureilite and 1 LL3 orginary chondrite.Using XANES it may be possible to find a common trait in the large cluster IDPs that will also be found in mete-orite samples.

  12. Chemical and physical studies of type 3 chondrites. IX. Thermoluminescence and hydrothermal annealing experiments and their relationship to metamorphism and aqueous alteration in type < 3. 3 ordinary chondrites

    SciTech Connect

    Guimon, R.K.; Lofgren, G.E.; Sears, D.W.G.

    1988-01-01

    Samples of four type 3 chondrites have been annealed at 400-850/sup 0/C and 0.77-1 kbar for 10-500 h in the presence of various amounts of water (0-10 wt.%) and sodium disilicate (0-2 molal) and their thermoluminescence properties measured. After annealing for > 20 h at temperatures > 600/sup 0/C, the TL sensitivity of the samples increased by factors of up to 40. After annealing at < 600/sup 0/C for 10-500 h, or relatively short periods at high temperatures (e.g., less than or equal to 20 h at 850/sup 0/C), the TL sensitivity of the samples decreased by up to 2 orders of magnitude (depending on the original value). The TL peak temperatures observed in the present experiments are consistent with a low form of feldspar (the TL phosphor) being produced at < 800/sup 0/C and a high form being produced at > 800/sup 0/C. When both high and low forms were present originally, the low-form was destroyed preferentially. The authors suggest that these data are consistent with the TL-metamorphism trends observed in type > 3.2 chondrites, being due to the formation of feldspar by the devitrification of chondrule glass during metamorphism. For types < 3.2, the TL data are equally consistent with these types experiencing lower levels of metamorphism than the higher types, or with type 3.0 being produced from higher types by aqueous alteration. The presence of water with non-terrestrial D/H ratios, and petrographic evidence for aqueous alteration in Semarkona, lead to favoring the aqueous alteration hypothesis.

  13. The Effects of Shock Metamorphism on Metal Textures and Metallographic Cooling Rates in L-Group Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Bennett, M. E.; McSween, H. Y., Jr.

    1993-07-01

    Postshock reheating and rapid cooling have severely disturbed geothermometers and coolingrate indicators in L chondrites. This has generated an ongoing debate on the interpretation of the early thermal history of an 'onion-shell' [1] or a 'rubble-pile' [2] L-chondrite parent body. In order to access the degree that reheating has perturbed metallographic cooling rates (disrupting this early thermal history), we have undertaken a study of textures derived from shock metamorphism and subsequent fast cooling of sulfides and Fe-Ni metals. Classification of shock stage by petrographic analysis [3] was performed on 70 L- chondrite thin sections, 55 Antarctic and 15 non-Antarctic, in order to place each into their appropriate shock stage. Fe-Ni metals from representative samples of each shock stage were studied optically and analyzed chemically with a Cameca SX-50 electron microprobe to obtain textural and chemical data. Meteorites of shock stage S3. Meteorites of S4 shock stage contain features similar to lower-shocked S3s, except that they exhibit more abundant melt pockets with melt droplets larger by an order of magnitude (~10 micrometers in diameter). Samples of shock grade S5 have numerous melt droplets of troilite adjacent to troilite grains. They also contain small metal-silicate melt veins and patchy fizzed troilite [4]. These textures indicate reheating to an average temperature of 600-800 degrees C at 45-55 GPa [3]. At S6 stage large melt pockets and veins are readily visible and all original metal textures are totally disrupted. Metallographic cooling rate data were obtained four moderately- to highly-shocked samples. The lack of coherency for these samples is indicative of heterogeneous cooling following shock and confirms the statement by numerous workers that extreme care must be taken when selecting samples of L chondrites for cooling-rate studies. Six low-shock samples were also analyzed for metallographic cooling rates. Incoherency in most of the samples may be due to the slight degree of shock reheating present in even the 'least-shocked' L chondrites, however great care was taken during the analyses to avoid those regions where shock-related features were noted. These samples do, however, display a general trend in cooling rates. The lowest metamorphic grade yielded the slowest cooling rates and an increase in grade followed an increase in cooling rate. This is opposite the relationship predicted by the onion-shell model and suggests that the L parent body may have broken up while still hot and then gravitationally reaccreted as a rubble-pile [6]. Further study of metal and sulfide textures in L chondrites will provide additional information that can be used to better quantify the effect of shock metamorphism on L chondrites. This additional information will, in turn, furnish the necessary low-shock samples for use in determining the thermal history and, hence, the internal structure of the L-chondrite parent body. References: [1] Pellas P. and Storzer D. (1981) Proc. R. Soc. Lond., A374, 253-270. [2] Taylor G. J. et al. (1987) Icarus, 69, 1-13. [3] Stoffler D. et al. (l991) GCActa, 55, 3845-3867. [4] Scott E. R. D. et al. (1991) Meteoritics, 26, 393. [5] Raikes S. and Ahrens T. J. (1979) Geophys. J. R. Astron. Soc., 58, 717

  14. KINETICS AND VOLATILIZATION OF SiC AND SiO2: IMPLICATIONS FOR METAMORPHISM OF UNEQUILIBRATED ORDINARY CHONDRITES; R.A. Mendybaev1,3, J.R. Beckett3, L. Grossman1,2, and E.

    E-print Network

    .66 0.68 IW+1 1400° 1350° 1300° 1250° IW-3 E =579±19 kJ/mole IW-1 E ~220 kJ/mole IW-2 E IW-1 E =96±20 kJ indistinguishable. Although R for SiO2 is usu- ally a little higher than that of SiC (e.g., 3.2x10-7 vs. 1.7x10-7 mg/mole Fig. 1 IW -16.0 -15.0 -14.0 -13.0 -12.0 -11.0 0.6 0.62 0.64 0.66 0.68 1000/T,K IW+1 1400° 1350° 1300

  15. Origin of iron-rich olivine in the matrices of type 3 ordinary chondrites - an experimental study

    NASA Astrophysics Data System (ADS)

    Nagahara, H.; Kushiro, I.

    1987-10-01

    The reaction of metallic iron and enstatite, with and without forsterite and SiO2, is experimentally studied at temperatures between 1150 and 800 C in order to investigate the origin of iron-rich olivine in the matrices of type 3 chondrites. The composition of olivine is shown to become more iron-rich with increasing silica/enstatite ratio. Possible scenarios for the origin of this olivine include: (1) free silica having been present if the iron-rich olivine was formed by solid-state reactions under oxidizing conditions in the solar nebula; and (2) the reaction of silicon-rich gas with metallic iron having taken place under oxidizing conditions in the solar nebula.

  16. Organic Analysis of Catalytic Fischer-Tropsch Synthesis Products and Ordinary Chondrite Meteorites by Stepwise Pyrolysis-GCMS: Organics in the Early Solar Nebula

    NASA Technical Reports Server (NTRS)

    Locke, Darren R.; Yazzie, Cyriah A.; Burton, Aaron S.; Niles, Paul B.; Johnson, Natasha M.

    2014-01-01

    Abiotic generation of complex organic compounds, in the early solar nebula that formed our solar system, is hypothesized by some to occur via Fischer-Tropsch (FT) synthesis. In its simplest form, FT synthesis involves the low temperature (<300degC) catalytic reaction of hydrogen and carbon monoxide gases to form more complex hydrocarbon compounds, primarily n-alkanes, via reactive nano-particulate iron, nickel, or cobalt, for example. Industrially, this type of synthesis has been utilized in the gas-to-liquid process to convert syngas, produced from coal, natural gas, or biomass, into paraffin waxes that can be cracked to produce liquid diesel fuels. In general, the effect of increasing reaction temperature (>300degC) produces FT products that include lesser amounts of n-alkanes and greater alkene, alcohol, and polycyclic aromatic hydrocarbon (PAH) compounds. We have begun to experimentally investigate FT synthesis in the context of abiotic generation of organic compounds in the early solar nebula. It is generally thought that the early solar nebula included abundant hydrogen and carbon monoxide gases and nano-particulate matter such as iron and metal silicates that could have catalyzed the FT reaction. The effect of FT reaction temperature, catalyst type, and experiment duration on the resulting products is being investigated. These solid organic products are analyzed by thermal-stepwise pyrolysis-GCMS and yield the types and distribution of hydrocarbon compounds released as a function of temperature. We show how the FT products vary by reaction temperature, catalyst type, and experimental duration and compare these products to organic compounds found to be indigenous to ordinary chondrite meteorites. We hypothesize that the origin of organics in some chondritic meteorites, that represent an aggregation of materials from the early solar system, may at least in part be from FT synthesis that occurred in the early solar nebula.

  17. C:\\Laura\\Ivtan\\Early Earth\\trace elements\\drafts\\SF08trace-revision2.doc 4:04:50 PM 7/23/2009 Volatile Element Chemistry during Metamorphism of Ordinary Chondritic Material

    E-print Network

    C:\\Laura\\Ivtan\\Early Earth\\trace elements\\drafts\\SF08trace-revision2.doc 4:04:50 PM 7/23/2009 1 Volatile Element Chemistry during Metamorphism of Ordinary Chondritic Material and Some of its Implications: 5 #12;C:\\Laura\\Ivtan\\Early Earth\\trace elements\\drafts\\SF08trace-revision2.doc 4:04:50 PM 7

  18. Micron-scale D/H heterogeneity in chondrite matrices: a signature of the pristine solar system water?

    E-print Network

    Piani, Laurette; Remusat, Laurent

    2015-01-01

    Organic matter and hydrous silicates are intimately mixed in the matrix of chondrites and in-situ determination of their individual D/H ratios is therefore challenging. Nevertheless, the D/H ratio of each pure component in this mixture should yield a comprehensible signature of the origin and evolution of water and organic matter in our solar system. We measured hydrogen isotope ratios of organic and hydrous silicates in the matrices of two carbonaceous chondrites (Orgueil CI1 and Renazzo CR2) and one unequilibrated ordinary chondrite (Semarkona, LL3.0). A novel protocol was adopted, involving NanoSIMS imaging of H isotopes of monoatomatic ($H^-$) and molecular ($OH^-$) secondary ions collected at the same location. This allowed the most enriched component with respect to D to be identified in the mixture. Using this protocol, we found that in carbonaceous chondrites the isotopically homogeneous hydrous silicates are mixed with D-rich organic matter. The opposite was observed in Semarkona. Hydrous silicates i...

  19. Intrinsic oxygen fugacity measurements on seven chondrites, a pallasite, and a tektite and the redox state of meteorite parent bodies

    USGS Publications Warehouse

    Brett, R.; Sato, M.

    1984-01-01

    Intrinsic oxygen-fugacity (fO2) measurements were made on five ordinary chondrites, a carbonaceous chondrite, an enstatite chondrite, a pallasite, and a tektite. Results are of the form of linear log fO2 - 1 T plots. Except for the enstatite chondrite, measured results agree well with calculated estimates by others. The tektite produced fO2 values well below the range measured for terrestrial and lunar rocks. The lowpressure atmospheric regime that is reported to follow large terrestrial explosions, coupled with a very high temperature, could produce glass with fO2 in the range measured. The meteorite Salta (pallasite) has low fO2 and lies close to Hvittis (E6). Unlike the other samples, results for Salta do not parallel the iron-wu??stite buffer, but are close to the fayalite-quartz-iron buffer in slope. Minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites. fO2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fO2 conditions. The samples equilibrated with respect to fO2 in relatively short time on heating. Equilibration with respect to fO2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism. Application of P - T - fO2 relations in the system C-CO-CO2 indicates that the ordinary chondrites were metamorphosed at pressures of 3-20 bars, as it appears that they lay on the graphite surface. A steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior, an oxidized near-surface layer, and an interior that is increasingly reduced with depth; a shallow thermal gradient will produce the reverse. A body heated by accretion on the outside will have a reduced exterior and oxidized interior. Meteorites from the same parent body clearly are not required to have similar redox states. ?? 1984.

  20. Highly siderophile elements in chondrites

    USGS Publications Warehouse

    Horan, M.F.; Walker, R.J.; Morgan, J.W.; Grossman, J.N.; Rubin, A.E.

    2003-01-01

    The abundances of the highly siderophile elements (HSE), Re, Os, Ir, Ru, Pt and Pd, were determined by isotope dilution mass spectrometry for bulk samples of 13 carbonaceous chondrites, 13 ordinary chondrites and 9 enstatite chondrites. These data are coupled with corresponding 187Re-187Os isotopic data reported by Walker et al. [Geochim. Cosmochim. Acta, 2002] in order to constrain the nature and timing of chemical fractionation relating to these elements in the early solar system. The suite of chondrites examined displays considerable variations in absolute abundances of the HSE, and in the ratios of certain HSE. Absolute abundances of the HSE vary by nearly a factor of 80 among the chondrite groups, although most vary within a factor of only 2. Variations in concentration largely reflect heterogeneities in the sample aliquants. Different aliquants of the same chondrite may contain variable proportions of metal and/or refractory inclusions that are HSE-rich, and sulfides that are HSE-poor. The relatively low concentrations of the HSE in CI1 chondrites likely reflect dilution by the presence of volatile components. Carbonaceous chondrites have Re/Os ratios that are, on average, approximately 8% lower than ratios for ordinary and enstatite chondrites. This is also reflected in 187Os/188Os ratios that are approximately 3% lower for carbonaceous chondrites than for ordinary and enstatite chondrites. Given the similarly refractory natures of Re and Os, this fractionation may have occurred within a narrow range of high temperatures, during condensation of these elements from the solar nebula. Superimposed on this major fractionation are more modest movements of Re or Os that occurred within the last 0-2 Ga, as indicated by minor open-system behavior of the Re-Os isotope systematics of some chondrites. The relative abundances of other HSE can also be used to discriminate among the major classes of chondrites. For example, in comparison to the enstatite chondrites, carbonaceous and ordinary chondrites have distinctly lower ratios of Pd to the more refractory HSE (Re, Os, Ir, Ru and Pt). Differences are particularly well resolved for the EH chondrites that have Pd/Ir ratios that average more than 40% higher than for carbonaceous and ordinary chondrite classes. This fractionation probably occurred at lower temperatures, and may be associated with fractionation processes that also affected the major refractory lithophile elements. Combined, 187Os/188Os ratios and HSE ratios reflect unique early solar system processing of HSE for each major chondrite class. ?? 2002 Elsevier Science B.V. All rights reserved.

  1. Carbon and Oxygen Isotope Measurements of Ordinary Chondrite (OC) Meteorites from Antarctica Indicate Distinct Carbonate Species Using a Stepped Acid Extraction Procedure

    NASA Technical Reports Server (NTRS)

    Evans, Michael E.

    2015-01-01

    The purpose of this study is to characterize the stable isotope values of terrestrial, secondary carbonate minerals from five Ordinary Chondrite (OC) meteorites collected in Antarctica. These samples were identified and requested from NASA based upon their size, alteration history, and collection proximity to known Martian meteorites. They are also assumed to be carbonate-free before falling to Earth. This research addresses two questions involving Mars carbonates: 1) characterize terrestrial, secondary carbonate isotope values to apply to Martian meteorites for isolating in-situ carbonates, and 2) increase understanding of carbonates formed in cold and arid environments with Antarctica as an analog for Mars. Two samples from each meteorite, each approximately 0.5 grams, were crushed and dissolved in pure phosphoric acid for 3 sequential reactions: a) R times 0 for 1 hour at 30 degrees Centigrade (fine calcite extraction), b) R times 1 for 18 hours at 30 degrees Centigrade (course calcite extraction), and c) R times 2 for 3 hours at 150 degrees Centigrade (siderite and/or magnesite extraction). CO (sub 2) was distilled by freezing with liquid nitrogen from each sample tube, then separated from organics and sulfides with a TRACE GC using a Restek HayeSep Q 80/100 6 foot 2 millimeter stainless column, and then analyzed on a Thermo MAT 253 Isotope Ratio Mass Spectrometer (IRMS) in Dual Inlet mode. This system was built at NASA/JSC over the past 3 years and proof-tested with known carbonate standards to develop procedures, assess yield, and quantify expected error bands. Two distinct species of carbonates are found: 1) calcite, and 2) non-calcite carbonate (future testing will attempt to differentiate siderite from magnesite). Preliminary results indicate the terrestrial carbonates are formed at approximately sigma (sup 13) C equal to plus 5 per mille, which is consistent with atmospheric CO (sub 2) sigma (sup 13) C equal to minus 7 per mille and fractionation of plus12 per mille based upon polar temperature of -20 degrees Centigrade. The oxygen values fractionate sigma (sup 18) O equal to minus 10-20 per mille lighter between the R times 0 and R times 1 reactions at 30 degrees Centigrade. The carbonate oxygen isotope measurements are consistently heavier than expected with meteoric water and temperatures from Antarctica, perhaps due to secondary carbonate formation during curation in Houston, TX.

  2. The Natural Thermoluminescence Survey of Antarctic Meteorites: Ordinary Chondrites at the Grosvenor Mountains, Macalpine Hills, Pecora Escarpment and Queen Alexandra Range, and New Data for the Elephant Moraine, Ice Fields

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The natural TL (Thermoluminescence) survey of Antarctic meteorites was started in 1987 at the request of the Antarctic Meteorite Working Group in order to provide an initial description of radiation and thermal histories. It was intended to be a complement to the mineralogical and petrographic surveys performed at the Johnson Space Center and the Smithsonian Institution. All ANSMET (Antarctic Search for Meteorites) samples recovered since then, besides those that were heated throughout by atmospheric passage, have been measured. To date this amounts to about 1200 samples. As the data for each ice field reaches a significant level, we have been conducting a thorough examination of the data for that field with a view to identifying pairing, providing an estimate of terrestrial age and residence time on the ice surface, looking for differences in natural TL between ice fields, looking for variations in natural TL level with location on the ice, looking for meteorites with natural TL levels outside the normal range. Pairing is a necessary first step in ensuring the most productive use of the collection, while geographical variations could perhaps provide clues to concentration mechanisms. Samples with natural TL values outside the normal range are usually inferred to have had either small perihelia or recent changes in orbital elements. In addition, induced TL data have enabled us to look for evidence for secular variation in the nature of the flux of meteorites to Earth, and look for petrologically unusual meteorites, such as particularly primitive ordinary chondrites, heavily shocked meteorites, or otherwise anomalous meteorites. To date we have published studies of the TL properties of 167 ordinary chondrites from Allan Hills, 107 from Elephant Moraine and 302 from Lewis Cliff and we have discussed the TL properties of fifteen H chondrites collected at the Allan Hills by Euromet after a storm during the 1988 season. We now have additional databases for a reasonable number of ordinary chondrites from Grosvenor Mountains (39 meteorites), MacAlpine Hills (70 meteorites), Pecora Escarpment (60 meteorites), and Queen Alexandra Range (173 meteorites) and we have data for a further 101 samples from Elephant Moraine. The results are summarized. We also have fairly minimal databases (10-15 meteorites) for Dominion Range, Graves Nunataks, Reckling Peak and Wisconsin Range that will not be discussed here.

  3. The Natural Thermoluminescence Survey of Antarctic Meteorites: Ordinary Chondrites at the Grosvenor Mountains, MacAlpine Hills, Pecora Escarpment and Queen Alexandra Range, and New Data New Data for the Elephant Moraine, Ice Fields

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    The natural TL survey of Antarctic meteorites was started in 1987 at the request of the Antarctic Meteorite Working Group in order to provide an initial description of radiation and thermal histories. It was intended to be a complement to the mineralogical and petrographic surveys performed at the Johnson Space Center and the Smithsonian Institution. All ANSMET samples recovered since then, besides those that were heated throughout by atmospheric passage, have been measured. To date this amounts to about 1200 samples. As the data for each ice field reaches a significant level, we have been conducting a thorough examination of the data for that field with a view to (1) identifying pairing, (2) providing an estimate of terrestrial age and residence time on the ice surface, (3) looking for differences in natural TL between ice fields, (4) looking for variations in natural TL level with location on the ice, (5) looking for meteorites with natural TL levels outside the normal range. Pairing is a necessary first step in ensuring the @ost productive use of the collection, while geographical variations could perhaps provide clues to concentration mechanisms. Samples with natural TL values outside the normal range are usually inferred to have had either small perihelia or recent changes in orbital elements. In addition, induced TL data have enabled us to (5) look for evidence for secular variation in the nature of the flux of meteorites to Earth, and (6) look for petrologically unusual meteorites, such as particularly primitive ordinary chondrites, heavily shocked meteorites, or otherwise anomalous meteorites. To date we have published studies of the TL properties of 167 ordinary chondrites from Allan Hills, 107 from Elephant Moraine and 302 from Lewis Cliff and we have discussed the TL properties of fifteen H chondrites collected at the Allan Hills by Euromet after a storm during the 1988 season. We now have additional databases for a reasonable number of ordinary chondrites from Grosvenor Mountains (39 meteorites), MacAlpine Hills (70 meteorites), Pecora Escarpment (60 meteorites), and Queen Alexandra Range (173 meteorites) and we have data for a further 101 samples from Elephant Moraine. The results are summarized in Table 1. We also have fairly minimal databases (10-15 meteorites) for Dominion Range, Graves Nunataks, Reckling Peak and Wisconsin Range that will not be discussed here.

  4. Shock metamorphism of carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Scott, Edward R. D.; Keil, Klaus; Stoeffler, Dieter

    1992-01-01

    Shock effects were studied in 69 carbonaceous chondrites, including CM2, CO3, CV3, ungrouped C2-C4, and CK4-6 chondrites, using optical microscopy of thin sections. It is shown that the classification scheme of Stoeffler et al. (1991) for the progressive stages of shock metamorphism in ordinary chondrites is also applicable to carbonaceous chondrites. On the basis of shock effects in olivine, the 69 carbonaceous chondrites could be assigned to four shock stage, S1 to S4. The CM2 and CO3 groups were found to be the least shocked chondrite groups, whereas the CK4-6 and CV3 were the most strongly shocked groups.

  5. Mean Atomic Weight of Chelyabinsk and Olivenza LL5 Chondrites

    NASA Astrophysics Data System (ADS)

    Szurgot, M.

    2015-07-01

    Mean atomic weights (Amean) of Chelyabinsk and Olivenza LL5 chondrites have been determined and analysed. Relationship between Fe/Si atomic ratio and mean atomic weight of ordinary chondrites has been established which enables one to predict Amean values.

  6. Chemical and physical studies of type 3 chondrites. IX - Thermoluminescence and hydrothermal annealing experiments and their relationship to metamorphism and aqueous alteration in type below 3.3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Guimon, R. Kyle; Sears, Derek W. G.; Lofgren, Gary E.

    1988-01-01

    Thermoluminescence (TL) properties were measured in samples of four type-3.0 chondrites annealed at 400-850 C and 0.77-1 kbar in the presence of various amounts of water and sodium disilicate. Several changes recorded in TL characteristics, such as the lowering of TL sensitivity in certain samples, its increase in other samples, and changes in the peak position and peak width of TL suggested the occurrence of metamorphic processes in these samples. It is suggested that, for the chondrite types above 3.2, the observed changes in TL are consistent with the TL-metamorphism trends, being due to the formation of feldspar by the devitrification of chondrule glass during metamorphism. For types below 3.2, the TL data are consistent with the hypothesis that these chondrules experienced lower levels of metamorphism than the higher types or, alternatively, with the hypothesis that the type 3.0 chondrules are being produced from higher types by aqueous alteration.

  7. Lunar and Planetary Science XXXV: Concerning Chondrites

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The Lunar and Planetary Science XXXV session entitled "Concerning Chondrites" includes the following topics: 1) Petrology and Raman Spectroscopy of Shocked Phases in the Gujba CB Chondrite and the Shock History of the CB Parent Body; 2) The Relationship Between CK and CV Chondrites: A Single Parent Body Source? 3) Samples of Asteroid Surface Ponded Deposits in Chondritic Meteorites; 4) Composition and Origin of SiO2-rich Objects in Carbonaceous and Ordinary Chondrites; 5) Re-Os Systematics and HSE distribution in Tieschitz (H3.6); Two Isochrons for One Meteorite; 6) Loss of Chromium from Olivine During the Metamorphism of Chondrites; 7) Very Short Delivery Times of Meteorites After the L-Chondrite Parent Body Break-Up 480 Myr Ago; and 8) The Complex Exposure History of a Very Large L/LL5 Chondrite Shower: Queen Alexandra Range 90201.

  8. A partial melting study of an ordinary (H) chondrite composition with application to the unique achondrite Graves Nunataks 06128 and 06129

    NASA Astrophysics Data System (ADS)

    Usui, Tomohiro; Jones, John H.; Mittlefehldt, David W.

    2015-04-01

    Melting experiments of a synthesized, alkali-bearing, H-chondrite composition were conducted at ambient pressure with three distinct oxygen fugacity conditions (IW-1, IW, and IW+2). Oxygen fugacity conditions significantly influence the compositions of partial melts. Partial melts at IW-1 are distinctly enriched in SiO2 relative to those of IW and IW+2 melts. The silica-enriched, reduced (IW-1) melts are characterized by high alkali contents and have silica-oversaturated compositions. In contrast, the silica-depleted, oxidized (?IW) melts, which are also enriched in alkali contents, have distinctly silica-undersaturated compositions. These experimental results suggest that alkali-rich, felsic, asteroidal crusts as represented by paired achondrites Graves Nunataks 06128 and 06129 should originate from a low-degree, relatively reduced partial melt from a parent body having near-chondritic compositions. Based on recent chronological constraints and numerical considerations as well as our experimental results, we propose that such felsic magmatism should have occurred in a parent body that is smaller in size and commenced accreting later than those highly differentiated asteroids having basaltic crusts and metallic cores.

  9. The effect of aqueous alteration and metamorphism in the survival of presolar silicate grains in chondrites

    E-print Network

    Trigo-Rodriguez, Josep M

    2009-01-01

    Relatively small amounts (typically between 2-200 parts per million) of presolar grains have been preserved in the matrices of chondritic meteorites. The measured abundances of the different types of grains are highly variable from one chondrite to another, but are higher in unequilibrated chondrites that have experienced little or no aqueous alteration and/or metamorphic heating than in processed meteorites. A general overview of the abundances measured in presolar grains (particularly the recently identified presolar silicates) contained in primitive chondrites is presented. Here we will focus on the most primitive chondrite groups, as typically the highest measured abundances of presolar grains occur in primitive chondrites that have experienced little thermal metamorphism. Looking at the most aqueously altered chondrite groups, we find a clear pattern of decreasing abundance of presolar silicate grains with increasing level of aqueous alteration. We conclude that the measured abundances of presolar grains...

  10. Lunar and Planetary Science XXXV: Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The titles in this section include: 1) A Quantitative NMR Analysis of Phosphorus in Carbonaceous and Ordinary Chondrites; 2) An Infrared Study of the Matrices of CI1 and CM2 Chondrites; 3) A Study of the Morphology, Composition and Mineral Associations of Fe-Ni Sulphides in CM Carbonaceous Chondrites; 4) Aqueous Alteration Mineralogy in CM Carbonaceous Chondrites; 5) In Situ Location and Characterization of Carbon-bearing Phases in Carbonaceous; 6) Chondrites: Insights from Yamato 791198, a Weakly-altered CM2 Chondrite; 7) Unique Texture in EET 83389: Clues to Formation of Fine Grained Rims in CM Chondrites; 8) Amoeboid Olivine Aggregates in the NWA 760 CV3 Chondrite; 9) Petrologic Type of CV3 Chondrites as Revealed by Raman Spectroscopy of Organic Matter; 10) A First Look at Acfer 324: Evidence for Another CR 3 Chondrite? 11) Hydrogen Isotopic Composition of the Bencubbin Meteorite; 12) The Fountain Hills Meteorite: A New CBa Chondrite from Arizona; 13) Shock Effects in the Metal-rich Chondrites QUE 94411, Hammadah al Hamra 237 and Bencubbin; 14) Mineralogy and Petrology of Al-rich Objects in the CH Carbonaceous Chondrite North West Africa 739.

  11. Chondrites and Their Components

    NASA Astrophysics Data System (ADS)

    Scott, E. R. D.; Krot, A. N.

    Chondrites are extraordinary mixtures of materials with diverse origins that formed around other stars, in the solar nebula, and in their parent asteroids. Most chondrites were so severely altered by aqueous fluids, thermal metamorphism, and impacts that the original characteristics of their components have been largely erased. But a few pristine chondrites have preserved an exquisite mineralogical, chemical, isotopic, and chronological record of the first few million years of solar system history. The properties of diverse types of carbonaceous, ordinary, and enstatite chondrites focusing on the most pristine samples are reviewed to establish the chemical, isotopic, and mineralogical properties and origins of their components and to elucidate the asteroidal processes that modified them. Refractory inclusions - amoeboid olivine aggregates and Ca-Al-rich inclusions - were the first solids to form in the solar nebula near to the protosun. Chondrules and associated metallic Fe-Ni grains were still forming several million years later when the earliest planetesimals, which melted due to heat from 26Al decay, were colliding. In the least-altered chondrites, matrix material, which coats chondrules and other components, is largely composed of micrometer-sized silicates and amorphous materials, which formed at high temperatures, plus small amounts (up to 200 ppm) of presolar oxides and silicates.

  12. A preliminary investigation of Jilantai chondrite

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Yang, X.

    In the afternoon on March 15, 1979, a chondrite, 20.5 kg in total weight, fell in the Jilantai People's Commune at Alxa Zuoqi, Inner Mongolia, China. In terms of mineralogic identification and chemical analysis, this meteorite should be assigned to L-group ordinary chondrites.

  13. The Vicência meteorite fall: A new unshocked (S1) weakly metamorphosed (3.2) LL chondrite

    NASA Astrophysics Data System (ADS)

    Keil, Klaus; Zucolotto, Maria E.; Krot, Alexander N.; Doyle, Patricia M.; Telus, Myriam; Krot, Tatiana V.; Greenwood, Richard C.; Franchi, Ian A.; Wasson, John T.; Welten, Kees C.; Caffee, Marc W.; Sears, Derek W. G.; Riebe, My; Wieler, Rainer; Santos, Edivaldo; Scorzelli, Rosa B.; Gattacceca, Jerome; Lagroix, France; Laubenstein, Matthias; Mendes, Julio C.; Schmitt-Kopplin, Philippe; Harir, Mourad; Moutinho, Andre L. R.

    2015-06-01

    The Vicência meteorite, a stone of 1.547 kg, fell on September 21, 2013, at the village Borracha, near the city of Vicência, Pernambuco, Brazil. It was recovered immediately after the fall, and our consortium study showed it to be an unshocked (S1) LL3.2 ordinary chondrite. The LL group classification is based on the bulk density (3.13 g cm-3); the chondrule mean apparent diameter (0.9 mm); the bulk oxygen isotopic composition (?17O = 3.768 ± 0.042‰, ?18O = 5.359 ± 0.042‰, ?17O = 0.981 ± 0.020‰); the content of metallic Fe,Ni (1.8 vol%); the Co content of kamacite (1.73 wt%); the bulk contents of the siderophile elements Ir and Co versus Au; and the ratios of metallic Fe0/total iron (0.105) versus total Fe/Mg (1.164), and of Ni/Mg (0.057) versus total Fe/Mg. The petrologic type 3.2 classification is indicated by the beautifully developed chondritic texture, the standard deviation (~0.09) versus mean Cr2O3 content (~0.14 wt%) of ferroan olivine, the TL sensitivity and the peak temperature and peak width at half maximum, the cathodoluminescence properties of chondrules, the content of trapped 132Xetr (0.317 × 10-8cm3STP g-1), and the Raman spectra for organic material in the matrix. The cosmic ray exposure age is ~72 Ma, which is at the upper end of the age distribution of LL group chondrites. The meteorite is unusual in that it contains relatively large, up to nearly 100 ?m in size, secondary fayalite grains, defined as olivine with Fa>75, large enough to allow in situ measurement of oxygen and Mn-Cr isotope systematics with SIMS. Its oxygen isotopes plot along a mass-dependent fractionation line with a slope of ~0.5 and ?17O of 4.0 ± 0.3‰, and are similar to those of secondary fayalite and magnetite in the unequilibrated chondrites EET 90161, MET 96503, and Ngawi. These data suggest that secondary fayalite in Vicência was in equilibrium with a fluid with a ?17O of ~4‰, consistent with the composition of the fluid in equilibrium with secondary magnetite and fayalite in other unequilibrated ordinary chondrites. Secondary fayalite and the chondrule olivine phenocrysts in Vicência are not in isotopic equilibrium, consistent with low-temperature formation of fayalite during aqueous alteration on the LL parent body. That alteration, as dated by the 53Mn-53Cr chronology age of secondary fayalite, took place 4.0-1.1+1.4 Ma after formation of CV CAIs when anchored to the quenched angrite D'Orbigny.

  14. Osmium isotope evidence for an s-process carrier in primitive chondrites.

    PubMed

    Brandon, A D; Humayun, M; Puchtel, I S; Leya, I; Zolensky, M

    2005-08-19

    Osmium extracted from unequilibrated bulk chondrites has isotope anomalies consistent with an insoluble s-process carrier, termed Os(i) here. Osmium from metamorphosed bulk chondrites does not have isotope anomalies, implying that the Os(i) carrier was destroyed by metamorphism. The isotopic homogeneity of metamorphosed bulk chondrites is consistent with extremely effective mixing of presolar grains from varied sources in the nebula. Osmium in the Os(i) carrier is likely from nucleosynthetic sites with a neutron density about two to four times as high as that of the average solar s-process Os. PMID:16109878

  15. Osmium Isotopic Compositions of Chondrites and Earth's Primitive Upper Mantle: Constraints on the Late Veneer

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Horan, M. F.; Morgan, J. W.; Meisel, T.

    2001-01-01

    The 187 Os/188 Os of carbonaceous chondrites averages approximately 2% lower than for enstatite and ordinary chondrites. The primitive upper mantle ratio for the Earth best matches that of ordinary and enstatite chondrites. Additional information is contained in the original extended abstract.

  16. Mean Atomic Weight of Pu?tusk Meteorite and H Chondrites

    NASA Astrophysics Data System (ADS)

    Szurgot, M.

    2015-07-01

    Mean atomic weight Amean of Pu?tusk and fifteen other H chondrites has been determined and analyzed. It was concluded that relationship between Fe/Si atomic ratio and Amean of ordinary chondrites predicts precisely Amean values.

  17. Opaque Assemblages in CK and CV Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Neff, K. E.; Righter, K.

    2006-01-01

    CK carbonaceous chondrites are the only group of carbonaceous chondrites that exhibit thermal metamorphism. As a result, CKs display features of metamorphism such as silicate darkening, recrystallization and shock veins. Calcium Aluminum Inclusions and Fe-Ni metal are rare. CV carbonaceous chondrites are unequilibrated and have two subgroups; oxidized and reduced. The CV and CK carbonaceous chondrite groups have been compared to each other often because of petrographic similarities, such as overlapping oxygen isotopic ratios. Scientists have suggested the two groups of carbonaceous chondrites formed from the same parent body and CKs are equilibrated CV chondrites [1, 2]. The oxidized CV group has been most closely related to CKs. This study examines the petrology and mineralogy of CKs and CVs focusing on opaque minerals found in the meteorites. Using the oxide, metal and sulfide assemblages, constraints can be placed on the temperature and oxygen fugacity at which the meteorites equilibrated. The temperature and oxygen fugacity of the CK and CV chondrites can be compared in order to help define their formation history.

  18. Lea County 001, an H5 chondrite, and Lea County 002, an ungrouped type 3 chondrite

    SciTech Connect

    Zolensky, M.E.; Score, R.; Clayton, R.N.; Mayeda, T.K.; Schutt, J.W. Lockheed Engineering and Sciences Co., Houston, TX Chicago Univ., IL )

    1989-12-01

    A search of active deflation basins near Jal, Lea County, New Mexico resulted in the discovery of two meteorites, Lea County 001 and 002. Lea County 001 has mean olivine and low-Ca pyroxene compositions of Fa(19) and Fs(17), respectively. These and all other mineralogical and petrological data collected indicate a classification of H5 for this stone. Lea County 002 has mean olivine and low-Ca pyroxene compositions of Fa(2) and Fs(4), and is unequilibrated. Although it is mineralogically most similar to Kakangari and chondritic clasts within Cumberland Falls, the high modal amount of forsterite makes Lea County a unique type 3 chondrite. Oxygen isotope data for Lea County 002 fall on an 0-16-mixing line through those of the enstatite meteorites and IAB irons, a feature shared by Kakangari. 28 refs.

  19. Devgaon (H3) chondrite: Classification and complex cosmic ray exposure history

    NASA Astrophysics Data System (ADS)

    Murty, S. V. S.; Rai, V. K.; Shukla, A. D.; Srinivasan, G.; Shukla, P. N.; Suthar, K. M.; Bhandari, N.; Bischoff, A.

    2004-03-01

    The Devgaon meteorite fell in India on February 12, 2001 and was immediately collected. It is an ordinary chondrite having a number of SiO2-rich objects and some Ca, Al-rich inclusions. Olivines (Fa17-19) are fairly equilibrated, while pyroxenes (Fs4-20) are unequilibrated. Occasionally, shock veins are visible, but the bulk rock sample is very weakly shocked (S2). Chondrules and chondrule fragments are abundant. Based on chemical and petrological features, Devgaon is classified as an H3.8 group chondrite. Several cosmogenic radionuclides ranging in half-lives from 5.6 d (52Mn) to 7.3 × 105 yr (26Al), noble gases (He, Ne, Ar, Kr, and Xe), and particle track density have been measured. The track density in olivines from five spot samples varies between (4.6 to 9) × 106 cm-2 showing a small gradient within the meteorite. The light noble gases are dominated by cosmogenic and radiogenic components. Large amounts of trapped gases (Ar, Kr, and Xe) are present. In addition, (n, g) products from Br and I are found in Kr and Xe, respectively. The average cosmic ray exposure age of 101 ± 8 Ma is derived based on cosmogenic 38Ar, 83Kr, and 126Xe. The track production rates correspond to shielding depths of about 4.9 to 7.8 cm, indicating that the stone suffered type IV ablation. Low 60Co, high (22Ne/21Ne)c, and large neutron produced excesses at 80Kr, 82Kr, and 128Xe indicate a complex exposure history of the meteoroid. In the first stage, a meter-sized body was exposed for nearly 108 yr in the interplanetary space that broke up in ~50 cm-sized fragments about a million years ago (stage 2), before it was captured by the Earth.

  20. Glass Veins in the Unequilibrated Eucrite Yamato 82202

    NASA Technical Reports Server (NTRS)

    Bogard, Donald; Buchanan, Paul; Noguchi, T.; Katavama, Ikuo

    2004-01-01

    The unequilibrated eucrite Yamato 82202 (Y82202) contains a network of glass veins, which are relatively thick (up to 1 mm in width) and are not devitrified. The host of the meteorite represents volcanic rock that crystallized >4.3 Gyr ago, probably as a lava flow on the surface of 4 Vesta. The impact event that formed the glass veins occurred at approx. 3.9 Gyr under conditions of low effective fo2 and very rapid cooling. A S-rich vapor probably was generated by impact vaporization of sulfides. The impact melt was not superheated and it retains some disordered structural characteristics of the original pyroxene and feldspar of the eucritic target lithology. The unequilibrated pyroxenes of this eucrite and the pristine character of the glass indicate that the meteorite experienced no significant metamorphism after initial crystallization. Hence, it was not buried to a significant depth or covered by a lava flow or hot layer of impact ejecta. The meteorite resided at a shallow level (though not at the surface) on 4 Vesta or on one of the vestoids until it was ejected and traveled to Earth, probably with other HED materials that have Ar-36 exposure ages of approx. 13 Myr.

  1. I-Xe systematics in LL chondrites

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Podosek, F. A.; Swindle, T. D.; Honda, M.

    1988-01-01

    A stepwise heating analysis of Ar and Xe data from five neutron-irradiated whole rock LL chondrites (Soko Banja, Alta Ameen, Tuxtuac, Guidder, and Olivenza) is presented, emphasizing the complicated thermal history of ordinary chondrites. None of the present meteorites show a well-defined (Ar-40)-(Ar-39) apparent age plateau comprised of more than two release fractions. Most of the samples are found to yield well-defined high-temperature correlations between Xe-129/Xe-130 and Xe-128/Xe-130, and thus determinations of I-129/I-127 and Xe-129/Xe-130 at the time of isotopic closure for Xe. As in the case of other ordinary chondrites, the I-Xe systematics for LL chondrites correlate neither with a metamorphic grade nor with chronologies based opon other methods.

  2. The formation of Ca-, Fe-rich silicates in reduced and oxidized CV chondrites: The roles of impact-modified porosity and permeability, and heterogeneous distribution of water ices

    NASA Astrophysics Data System (ADS)

    MacPherson, Glenn J.; Krot, Alexander N.

    2014-07-01

    CV (Vigarano type) carbonaceous chondrites, comprising Allende-like (CVoxA) and Bali-like (CVoxB) oxidized and reduced (CVred) subgroups, experienced differing degrees of fluid-assisted thermal and shock metamorphism. The abundance and speciation of secondary minerals produced during asteroidal alteration differ among the subgroups: (1) ferroan olivine and diopside-hedenbergite solid solution pyroxenes are common in all CVs; (2) nepheline and sodalite are abundant in CVoxA, rare in CVred, and absent in CVoxB; (3) phyllosilicates and nearly pure fayalite are common in CVoxB, rare in CVred, and virtually absent in CVoxA; (4) andradite, magnetite, and Fe-Ni-sulfides are common in oxidized CVs, but rare in reduced CVs; the latter contain kirschsteinite instead. Thus, a previously unrecognized correlation exists between meteorite bulk permeabilities and porosities with the speciation of the Ca-, Fe-rich silicates (pyroxenes, andradite, kirschsteinite) among the CVox and CVred meteorites. The extent of secondary mineralization was controlled by the distribution of water ices, permeability, and porosity, which in turn were controlled by impacts on the asteroidal parent body. More intense shock metamorphism in the region where the reduced CVs originated decreased their porosity and permeability while simultaneously expelling intergranular ices and fluids. The mineralogy, petrography, and bulk chemical compositions of both the reduced and oxidized CV chondrites indicate that mobile elements were redistributed between Ca,Al-rich inclusions, dark inclusions, chondrules, and matrices only locally; there is no evidence for large-scale (>several cm) fluid transport. Published 53Mn-53Cr ages of secondary fayalite in CV, CO, and unequilibrated ordinary chondrites, and carbonates in CI, CM, and CR chondrites are consistent with aqueous alteration initiated by heating of water ice-bearing asteroids by decay of 26Al, not shock metamorphism.

  3. The Effect of Aqueous Alteration and Metamorphism in the Survival of Presolar Silicate Grains in Chondrites

    NASA Astrophysics Data System (ADS)

    Trigo-Rodriguez, Josep M.; Blum, Jürgen

    2009-09-01

    Relatively small amounts (typically between 2 and 200 ppm) of presolar grains have been preserved in the matrices of chondritic meteorites. The measured abundances of the different types of grains are highly variable from one chondrite to another, but are higher in unequilibrated chondrites that have experienced little or no aqueous alteration and/or metamorphic heating than in processed meteorites. A general overview of the abundances measured in presolar grains (particularly the recently identified presolar silicates) contained in primitive chondrites is presented. Here we will focus on the most primitive chondrite groups, as typically the highest measured abundances of presolar grains occur in primitive chondrites that have experienced little thermal metamorphism. Looking at the most aqueously altered chondrite groups, we find a clear pattern of decreasing abundance of presolar silicate grains with increasing levels of aqueous alteration. We conclude that measured abundances of presolar grains in altered chondrites are strongly biased by their peculiar histories. Scales quantifying the intensity of aqueous alteration and shock metamorphism in chondrites could correlate with the content of presolar silicates. To do this it would be required to infer the degree of destruction or homogenization of presolar grains in the matrices of primitive meteorites. To get an unbiased picture of the relative abundance of presolar grains in the different regions of the protoplanetary disk where first meteorites consolidated, future dedicated studies of primitive meteorites, IDPs, and collected materials from sample-return missions (like e.g. the planned Marco Polo) are urgently required.

  4. Roedderite in the Qingzhen (EH3) chondrite

    NASA Astrophysics Data System (ADS)

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

    1986-03-01

    The rare mineral roedderite, (Na1.09 K0.89 Ca0.02)2.00 (Mg4.71 Fe0.27)4.98 (Si11.80 Al0.09)11.89 O30 has been found in accessory amounts in the highly unequilibrated enstatite chondrite, Qingzhen. It occurs in association with minor amounts of albite and SiO2 as inclusions within the metal or sulfide phases of metal-sulfide assemblages. The roedderite crystals are connected through oxide and silicate veins to the surrounding matrix. The presence of glass coated vesicles on the surface of the assemblages strongly suggests that roedderite originated in the presence of a fluid phase, presumably during post-accretional planetary processes.

  5. Friday, March 27, 2009 EARLY SOLAR SYSTEM CHRONOLOGY

    E-print Network

    Rathbun, Julie A.

    -MC-ICPMS and SIMS techniques for the 26 Al-26 Mg system is demonstrated. 40th Lunar and Planetary Science Conference. Rudraswami N. G. Fe-Ni and Al-Mg Isotope Systematics in Chondrules from Unequilibrated Ordinary Chondrites [#1689] Fe-Ni and Al-Mg isotope systematics study was carried out on Unequilibrated ordinary chondrites

  6. Paired Renazzo-type (CR) carbonaceous chondrites from the Sahara

    NASA Astrophysics Data System (ADS)

    Bischoff, A.; Palme, H.; Ash, R. D.; Clayton, R. N.; Schultz, L.; Herpers, U.; Stoffler, D.; Grady, M. M.; Pillinger, C. T.; Spettel, B.; Weber, H.; Grund, T.; Endress, M.; Weber, D.

    1993-04-01

    Data on the chemical composition, mineralogy, abundance, and isotopic composition of recently found Sahara meteorites are presented. The nine Acfer samples and the El Djouf 001 meteorite are considered to belong to the same parent meteoroid and are classified as a CR chondrite. The Acfer-El Djouf meteorite has a CI-chondritic composition of nonvolatile elements, in particular CI ratios of refractory elements to Mg. The presence of metal with chondritic Fe/Ni ratios, olivine with relatively low FeO contents and with high Cr is attributed to the primitive, unequilibrated nature of Acfer-El Djouf and other CR chondrites. The carbon and nitrogen stable isotropic composition of the Acfer-El Djouf chondrite lies within the range of other members of the CR group. Rare gases of the Acfer-El Djouf meteorite contain a comparatively large solar wind component, in excess of that in Renazzo. The cosmic-ray exposure age of the Acfer-El Djouf meteorite is about 6 million years.

  7. Aqueous Alteration of Enstatite Chondrites

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E.; Ziegler, K.; Weisberg, M. K.; Gounelle, M.; Berger, E. L.; Le, L.; Ivanov, A.

    2014-01-01

    The Kaidun meteorite is different from all other meteorites [1], consisting largely of a mixture of “incompatible” types of meteoritic material – carbonaceous and enstatite chondrites, i.e. corre-sponding to the most oxidized and the most reduced samples of meteorite materials, including CI1, CM1-2, CV3, EH3-5, and EL3. In addition to these, minor amounts of ordinary and R chondrites are present. In addition, approximately half of the Kaidun lithologies are new materials not known as separate meteorites. Among these are aqueously altered enstatite chondrites [1], which are of considerable interest because they testify that not all reduced asteroids escaped late-stage oxidation, and hydrolysis, and also because hydrated poorly crystalline Si-Fe phase, which in turn is re-placed by serpentine (Figs 3-5). In the end the only indication of the original presence of metal is the re-sidual carbides. In other enstatite chondrite lithogies (of uncertain type) original silicates and metal have been thoroughly replaced by an assemblage of authi-genic plagioclase laths, calcite boxwork, and occasion-al residual grains of silica, Cr-rich troilite, ilmenite, and rare sulfides including heideite (Fig. 6). Fe and S have been largely leached from the rock (Fig. 4). Again the accessory phases are the first clue to the original character of the rock, which can be verified by O isotopes. It is fortunate that Kaidun displays every step of the alteration process.

  8. Structure, composition, and location of organic matter in the enstatite chondrite Sahara 97096 (EH3)

    E-print Network

    Piani, Laurette; Beyssac, Olivier; Binet, Laurent; Bourot-Denise, Michèle; Derenne, Sylvie; Guillou, Corentin Le; Marrocchi, Yves; Mostefaoui, Smail; Rouzaud, Jean-Noel; Thomen, Aurelien

    2015-01-01

    The insoluble organic matter (IOM) of an unequilibrated enstatite chondrite Sahara (SAH) 97096 has been investigated using a battery of analytical techniques. As the enstatite chondrites are thought to have formed in a reduced environment at higher temperatures than carbonaceous chondrites, they constitute an interesting comparative material to test the heterogeneities of the IOM in the solar system and to constrain the processes that could affect IOM during solar system evolution. The SAH 97096 IOM is found in situ: as submicrometer grains in the network of fine-grained matrix occurring mostly around chondrules and as inclusions in metallic nodules, where the carbonaceous matter appears to be more graphitized. IOM in these two settings has very similar $\\delta^{15}N$ and $\\delta^{13}C$; this supports the idea that graphitized inclusions in metal could be formed by metal catalytic graphitization of matrix IOM. A detailed comparison between the IOM extracted from a fresh part and a terrestrially weathered part...

  9. 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.

  10. Petrology and Cosmochemistry of a Suite of R Chondrites

    NASA Technical Reports Server (NTRS)

    Torrano, Z. A.; Mittlefehldt, D. W.; Peng, Z. X.

    2015-01-01

    Chondrites are among the most primitive surviving materials from the early solar system. They are divided into groups based on chemical types defined by mineralogy, bulk composition, and oxygen isotope compositions. Chondrites range in petrographic grade from type 1 to type 7. Type 3 chondrites are the most primitive and are little changed from the nebular solids accreted to form asteroids. They are composed of chondrules, fine-grained matrix, metal and sulfide, plus or minus Ca-Al-rich inclusions. With increasing aqueous alteration at low temperatures, members of some chondrite classes transformed from type 3 towards type 1. With increasing thermal metamorphism and low fluid content, members of other classes changed from type 3 towards type 7. Rumuruti (R) chondrites are a rare group (0.1% of falls) similar to ordinary chondrites in some properties but different in others. They are characterized by low chondrule/matrix modal abundance ratios, high oxidation state, small mean chondrule size, abundant sulfides and low metal contents. R chondrites vary in petrologic type from 3 to 6. They are important objects to study because some of them have undergone metamorphism at high temperatures in the presence of aqueous fluids. In contrast, CM and CI chondrites were heated to low temperatures in the presence of aqueous fluids leading to alteration; they contain low-T hydrous phases (phyllosilicates) and little or no remaining metal. Ordinary chondrites were heated to high temperatures in a low-fluid environment resulting in anhydrous metamorphic rocks. R6 chondrites are highly metamorphosed and some contain the high-T hydrous phases mica and amphibole. R chondrites are thus unique and give us an opportunity to examine whether there are compositional effects caused by high-T, highfluid metamorphism of nebular materials.

  11. The Pasamonte unequilibrated eucrite: Pyroxene REE systematic and major-, minor-, and trace-element zoning. [Abstract only

    NASA Technical Reports Server (NTRS)

    Pun, A.; Papike, J. J.

    1994-01-01

    We are evaluating the trace-element concentrations in the pyroxenes of Pasamonte. Pasamonte is a characteristic member of the main group eucrites, and has recently been redescribed as a polymict eucrite. Our Pasamonte sample contained eucritic clasts with textures ranging from subophitic to moderately coarse-grained. This study concentrates on pyroxenes from an unequilibrated, coarse-grained eucrite clast. Major-, minor-, and trace-element analyses were measured for zoned pyroxenes in the eucritic clast of Pasamonte. The major- and minor-element zoning traverses were measured using the JEOL 733 electron probe with an Oxford-Link imaging/analysis system. Complemenatry trace elements were then measured for the core and rim of each of the grains by SIMS. The trace elements analyzed consisted of eight REE, Sr, Y, and Zr. These analyses were performed on a Cameca 4f ion probe. The results of the CI chondrite normalized (average CI trace-element analyses for several grains and the major- and minor-element zoning patterns from a single pyroxene grain are given. The Eu abundance in the cores of the pyroxenes represents the detection limit and therefore the (-Eu) anomaly is a minimum. Major- and minor-element patterns are typical for igneous zoning. Pyroxene cores are Mg enriched, whereas the rims are enriched in Fe and Ca. Also, Ti and Mn are found to increase, while Cr and Al generally decrease in core-to-rim traverses. The cores of the pyroxenes are more depleted in the Rare Earth Elements (REE) than the rims. Using the minor- and trace-element concentrations of bulk Pasamonte and the minor- and trace-element concentrations from the cores of the pyroxenes in Pasamonte measured in this study, we calculated partition coefficients between pyroxene and melt. This calculation assumes that bulk Pasamonte is representative of a melt composition.

  12. Thermal evolution and sintering of chondritic planetesimals

    E-print Network

    Henke, Stephan; Trieloff, Mario; Schwarz, Winfried H; Kleine, Thorsten

    2011-01-01

    The major aim of this study is to assess the effects of sintering of initially porous material on the thermal evolution of planetesimals, and to constrain the values of basic parameters that determined the structure and evolution of the H chondrite parent body. A new code is presented for modeling the thermal evolution of ordinary chondrite parent bodies that initially are highly porous and undergo sintering by hot pressing as they are heated by decay of radioactive nuclei. The pressure and temperature stratification in the interior of the bodies is calculated by solving the equations of hydrostatic equilibrium and energy transport. The decrease of porosity of the granular material by hot pressing due to self-gravity is followed by solving a set of equations for the sintering of powder materials. For the heat conductivity of granular material we combine recently measured data for highly porous powder materials, relevant for the surface layers of planetesimals, with data for heat conductivity of chondrite mate...

  13. Thermal metamorphism of CI and CM carbonaceous chondrites - An internal heating model

    SciTech Connect

    Miyamoto, M. )

    1991-06-01

    Infrared diffuse reflectance spectra were measured for several thermally metamorphosed carbonaceous chondrites with CI-CM affinities which were recently found from Antarctica. Compared with other CI or CM carbonaceous chondrites, these Antarctic carbonaceous chondrites show weaker absorption bands near 3 microns due to hydrous minerals, and weaker absorption bands near 6.9 microns due to carbonates, interpreted as thermal metamorphic features. These absorption bands also disappear in the spectra of samples of the Murchison (CM) carbonaceous chondrite heated above 500 C, implying that the metamorphic temperatures of the Antarctic carbonaceous chondrites considered here were higher than about 500 C. Model calculations were performed to study thermal metamorphism of carbonaceous chondrites in a parent body internally heated by the decay of the extinct nuclide Al-26. The maximum temperature of the interior of a body more than 20 km in radius is 500-700 C for the bulk Al contents of CI and CM cabonaceous chondrites, assuming a ratio of Al-26/Al-27 = 5 {times} 10 to the -6th which has been previously proposed for an ordinary-chondrite parent body. The metamorphic temperatures experienced by the Antarctic carbonaceous chondrites considered here may be attainable by an internally heated body with an Al-26/Al-27 ratio similar to that inferred for an ordinary-chondrite parent body. 30 refs.

  14. Rhodium, gold and other highly siderophile element abundances in chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Fischer-Gödde, M.; Becker, H.; Wombacher, F.

    2010-01-01

    The abundances of the highly siderophile elements (HSE) Re, Os, Ir, Ru, Pt, Rh, Pd and Au, and 187Os/ 188Os isotope ratios have been determined for a set of carbonaceous, ordinary, enstatite and Rumuruti chondrites, using an analytical technique that permits the precise and accurate measurement of all HSE from the same digestion aliquot. Concentrations of Re, Os, Ir, Ru, Pt and Pd were determined by isotope dilution ICP-MS and N-TIMS analysis. The monoisotopic elements Rh and Au were quantified relative to the abundance of Ir. Differences in HSE abundances and ratios such as Re/Os, 187Os/ 188Os, Pd/Ir and Au/Ir between different chondrite classes are further substantiated with new data, and additional Rh and Au data, including new data for CI chondrites. Systematically different relative abundances of Rh between different chondrite classes are reminiscent of the behaviour of Re. Carbonaceous chondrites are characterized by low average Rh/Ir of 0.27 ± 0.03 (1s) which is about 20% lower than the ratio for ordinary (0.34 ± 0.02) and enstatite chondrites (EH: 0.33 ± 0.01; EL: 0.32 ± 0.01). R chondrites show higher and somewhat variable Rh/Ir of 0.37 ± 0.07. Well-defined linear correlations of HSE, in particular for bulk samples of ordinary and EL chondrites, are explained by binary mixing and/or dilution by silicates. The HSE carriers responsible for these correlations have a uniform chemical composition, indicating efficient homogenization of local nebular heterogeneities during or prior to the formation of the host minerals in chondrite components. Excepting Rumuruti chondrites and Au in carbonaceous chondrites, these correlations also suggest that metamorphism, alteration and igneous processes had negligible influence on the HSE distribution on the bulk sample scale. Depletion patterns for Rh, Pd and Au in carbonaceous chondrites other than CI are smoothly related to condensation temperatures and therefore consistent with the general depletion of moderately volatile elements in carbonaceous chondrites. Fractionated HSE abundance patterns of ordinary, enstatite and Rumuruti chondrites, however, are more difficult to explain. Fractional condensation combined with the removal of metal phases at various times, and later mixing of early and late formed metal phases may provide a viable explanation. Planetary fractionation processes that may have affected precursor material of chondrite components cannot explain the HSE abundance patterns of chondrite groups. HSE abundances of some, but not all Rumuruti chondrites may be consistent with solid sulphide-liquid sulphide fractionation processes during impact induced melting.

  15. Dynamic Crystallization Experiments Using Conventional and Solar Furnace Techniques--implications For The Formation of Refractory Forsterite In Chondrites

    NASA Astrophysics Data System (ADS)

    Pack, A.; Sauerborn, M.; Klerner, S.; Palme, H.; Neumann, A.; Seboldt, W.

    A distinct generation of forsteritic olivine (Mg2SiO4) grains (RF) with unusually high concentrations of refractory components including CaO (0.7 wt.%), Al2O3 (0.4 wt.%), V, Sc, and REEs occurs in unequilibrated chondrites, including ordinary, carbonaceous, and the highly oxidized Rumurutiites. Contents of siderophile elements like FeO (1 wt.%), Ni, or Mn are extremly low in RF. It is inferred that formation of RF pre-dates the formation of chondrules and matrix as well as formation of the different types of parent bodies (CCs, OCs, oxidized R-chondrites). Hence, RF can help us to better understand the processes in the early stage of the solar system in the time between formation of CAIs and Si,Mg-chondrules. However, formation of RF is not well understood. Crystallization of RF in chon- drules requires chondrule melts with ca. 20 wt.% CaO. Most chondrules have typically <4 wt.% CaO (max. ca. 10 wt.% CaO). We have conducted dynamic crystallization experiments using a conventional furnace (1.5...1000 K·min-1) and the DLR solar furnace (approx. 100000 K·min-1) in order to test if rapid cooling of a chondrule- like melt would produce high CaO in RF. We demostrate that Ca-partitioning between olivine and silicate melt is only weakly influenced by rapid cooling even at extremly high cooling rates in the range of 105 K·min-1 as obtained in the solar furnace ex- periments. At a bulk composition of the starting melt of 7.5 wt.% CaO, no deviation from equilibrium fractionation was observed (T/t = 1.5 . . . 105 K·min-1). At a ol/melt bulk content of 17.5 wt.% CaO, in increase in DCa of approximately 10...20% was observed. Chondrules with CaO contents in the range of 10 wt.% (upper limit of CaO in chondrules) thus cannot be regarded to be the host of RF. Hence, there must have been an early generation of extremly CaO-rich chondrules (20 wt.% CaO). Alternatively, RF may have formed by other processes, e. g. direct condensation from the solar nebula.

  16. Chemical and physical studies of type 3 chondrites - VIII: Thermoluminescence and metamorphism in the CO chondrites

    SciTech Connect

    Keck, B.D.; Sears, D.W.G. )

    1987-11-01

    The thermoluminescence properties of nine CO chondrites have been measured. With the exception of Colony and Allan Hills A77307 (ALHA 77307), whose maximum induced TL emission is at approximately 350{degree}C, CO chondrites exhibit two TL peaks, one at 124 {plus minus} 7{degree}C (130{degree}C peak) and one at 252 {plus minus} 7{degree}C (250{degree}C peak). The 130{degree}C peak shows a 100-fold range in TL sensitivity and correlates with various metamorphism-related phenomena, such as silicate heterogeneity, metal composition and McSween's metamorphic subtypes. The peak at 250{degree}C does not show these correlations and, Colony excepted, varies little throughout the class. Mineral separation experiments, and a series of annealing experiments on Isna, suggest that the TL properties for CO chondrites reflect the presence of feldspar in two forms, (1) a form produced during metamorphism, and analogous to the dominant form of feldspar in type 3 ordinary chondrites, and (2) a primary, metamorphism-independent form, perhaps associated with the amoeboid inclusions. If this interpretation is correct, then the CO chondrites have not experienced temperatures above the order/disorder temperature for feldspar (500-600{degree}C) and they cooled more slowly than comparable type 3 ordinary chondrites. Colony and ALHA 77307 have atypical TL properties, including very low TL sensitivity, suggesting that phosphors other than feldspar are important. They have apparently experienced less metamorphism than the others, and may have also been aqueously altered.

  17. Petrology and bulk chemistry of Yamato-82094, a new type of carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Barrat, J. A.; Weisberg, M. K.; Imae, N.; Yamaguchi, A.; Kojima, H.

    2014-03-01

    Carbonaceous chondrites are classified into several groups. However, some are ungrouped. We studied one such ungrouped chondrite, Y-82094, previously classified as a CO. In this chondrite, chondrules occupy 78 vol%, and the matrix is distinctly poor in abundance (11 vol%), compared with CO and other C chondrites. The average chondrule size is 0.33 mm, different from that in C chondrites. Although these features are similar to those in ordinary chondrites, Y-82094 contains 3 vol% Ca-Al-rich inclusions and 5% amoeboid olivine aggregates (AOAs). Also, the bulk composition resembles that of CO chondrites, except for the volatile elements, which are highly depleted. The oxygen isotopic composition of Y-82094 is within the range of CO and CV chondrites. Therefore, Y-82094 is an ungrouped C chondrite, not similar to any other C chondrite previously reported. Thin FeO-rich rims on AOA olivine and the mode of occurrence of Ni-rich metal in the chondrules indicate that Y-82094 is petrologic type 3.2. The extremely low abundance of type II chondrules and high abundance of Fe-Ni metal in the chondrules suggest reducing condition during chondrule formation. The depletion of volatile elements indicates that the components formed under high-temperature conditions, and accreted to the parent body of Y-82094. Our study suggests a wider range of formation conditions than currently recorded by the major C chondrite groups. Additionally, Y-82094 may represent a new, previously unsampled, asteroidal body.

  18. Transmission electron microscopy of an interplanetary dust particle with links to CI chondrites

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Thomas, Kathie L.; Mckay, David S.

    1991-01-01

    The majority of hydrated interplanetary dust particles (IDPs) have compositions that resemble CI and CM chondrites, however, their mineralogies are most similar to the fine grained material in certain altered type-3 carbonaceous and ordinary chondrites. During the transmission electron microscope studies of hydrated IDPs, a unique particle was discovered whose mineralogy is very similar to that reported from CI chondrites. W7013F5 is the first IDP whose mineralogy and chemistry approximates that of CI chondrites. The similarity in mineralogy and mineral chemistry suggests that W7013F5 was altered under conditions similar to those that existed on the CI parent bodies.

  19. The stable carbon isotopes in enstatite chondrites and Cumberland Falls

    NASA Astrophysics Data System (ADS)

    Deines, P.; Wickman, F. E.

    1985-01-01

    The carbon-isotopic composition (CIC) of the total carbon in the enstatite chondrites Indarch, Abee, St. Marks, Pillistfer, Hvittis and Daniel's Kuil and the enstatite achondrite Cumberland Falls has been measured. The empirical relationship between CIC and total carbon content is distinct from that of carbonaceous and ordinary chondrites. Within the enstatite chondrite group the average C-13 content increases with petrographic type: E4 less than E5 less than E6. Daniel's Kuil shows the largest C-13 enrichment in the bulk carbon of any meteorite. The CIC is most clearly correlated with the abundance of the elements Zn, Cd, and In. Insofar as these elements may hold the key to the understanding of enstatite chondrites, more detailed combined CIC and trace-element studies of these meteorites will play an important role in the deciphering of their history.

  20. Chondrite chronology by initial Sr-87/Sr-86 in phosphates?

    NASA Technical Reports Server (NTRS)

    Podosek, Frank A.; Brannon, Joyce C.

    1991-01-01

    New data are presented on Rb-Sr isotope analyses of phosphates from nine ordinary chondrites, including accurate identification of initial Sr-87/Sr-86. The initial Sr-87/Sr-86 ratios found in this study were generally significantly higher than the more primitive initial Sr-87/Sr-86 ratios inferred for carbonaceous chondrite refractory inclusions, basaltic achondrites, or bulk ordinary chondrites. Such elevation of initial Sr-87/Sr-86 is generally considered to reflect isotopic redistribution during metamorphism. However, in this study, no evident correlation was found between the phosphate initial Sr-87/Sr-86 compositions and the metamorphic grade. Two possible alternative hypotheses for high initial Sr-87/Sr-86 ratios are considered.

  1. The Olton, Texas, H chondrite regolith breccia - Paired with Dimmitt

    NASA Technical Reports Server (NTRS)

    Keil, Klaus; Ehlmann, A. J.; Wieler, Rainer

    1990-01-01

    The Olton ordinary chondrites (two stones found in 1948) are H group, solar wind-bearing regolith breccias. The proximity of the recovery site to the Dimmitt strewnfield, and the similarity in texture, composition, noble gas contents and isotopic ratios to Dimmitt indicate that Olton is paired with Dimmitt.

  2. Experimental Impacts into Chondritic Targets. Part 1; Disruption of an L6 Chondrite by Multiple Impacts

    NASA Technical Reports Server (NTRS)

    Cintala, Mark J.; Horz, Friedrich

    2007-01-01

    A fragment of an L6 chondrite (ALH 85017,13) with an initial mass (M(sub 0)) of 464.1 g was the target in a series of experimental impacts in which the largest remaining fragment (M(sub R)) after each shot was impacted by a 3.18-mm ceramic sphere at a nominal speed of 2 km/s. This continued until the mass of the largest remaining piece was less than half the mass of the target presented to that shot (M(sub S)). Two chunks of Bushveldt gabbro with similar initial masses were also impacted under the same conditions until M(sub R) was less than half M(sub 0). The two gabbro targets required a total of 1.51x10(exp 7) and 1.75x10(exp 7) erg/g to attain 0.27 and 0.33 M(sub R)/M(sub 0), respectively; the chondrite, however, was considerably tougher, reaching 0.40 and 0.21 M(sub R)/M(sub 0) only after receiving 2.37x10(exp 7) and 3.10x10(exp 7) erg g-1, respectively. The combined ejecta and spallation products from the gabbro impacts were coarser than those from the chondrite and in sufficient quantities that the new surface areas exceeded those from the meteorite until the fifth shot in the chondrite series, which was the number of impacts required to disrupt each gabbro target (i.e., MR/M0 = 0.5). Unlike the behavior shown in previous regolith-evolution series, neither gabbro target produced an enhancement in the size fraction reflecting the mean size of the crystals composing the rock (about 3 mm), an effect possibly related to the width of the shock pulse. The original chondrite was so fine-grained and fractured, and the variance in its grain-size distribution so large, that effects related to grain-size were relegated to the <63- m fraction. Impacts into ALH 85017 produced abundant, fine-grained debris, but otherwise the slopes of its size distributions were comparable to those from other experiments involving natural and fabricated terrestrial targets. The characteristic slopes of the chondrite's size distributions, however, were notably more constant over the entire nine-impact series than those from any of the terrestrial targets, a testament to the control over comminution apparently exerted by pre-existing fractures and other, microscopic damage in the meteorite. The enhancement in the finer fraction of debris from ALH 85017 indicates that ordinary chondrites in solar orbit would be very efficient contributors to the cosmic-dust complex. At the same time, the greater resistance to disruption displayed by ordinary chondrites relative to that exhibited by igneous rocks indicates that a selection effect could be operative between the annealed, ordinary-chondritic breccias and relatively weaker, differentiated meteorites. Preferential survival from their time in the regoliths of their parent bodies through their transit to Earth and passage through the atmosphere suggests that meteorite collections could be biased in favor of the ordinary chondrites.

  3. 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).

  4. Chemical and physical studies of type 3 chondrites 12: The metamorphic history of CV chondrites and their components

    NASA Technical Reports Server (NTRS)

    Guimon, R. Kyle; Symes, Steven J. K.; Sears, Derek W. G.

    1995-01-01

    The induced thermoluminescence (TL) properties of 16 CV and CV-related chondrites, four CK chondrites and Renazzo (CR2) have been measured in order to investigate their metamorphic history. The petrographic, mineralogical and bulk compositional differences among the CV chondrites indicate that the TL sensitivity of the approximately 130 C TL peak is reflecting the abundance of ordered feldspar, especially in chondrule mesostasis, which in turn reflects parent-body metamorphism. The TL properties of 18 samples of homogenized Allende powder heated at a variety of times and temperatures, and cathodoluminescence mosaics of Axtell and Coolidge, showed results consistent with this conclusion. Five refractory inclusions from Allende, and separates from those inclusions, were also examined and yielded trends reflecting variations in mineralogy indicative of high peak temperatures (either metamorphic or igneous) and fairly rapid cooling. The CK chondrites are unique among metamorphosed chondrites in showing no detectable induced TL, which is consistent with literature data that suggests very unusual feldspar in these meteorites. Using TL sensitivity and several mineral systems and allowing for the differences in the oxidized and reduced subgroups, the CV and CV-related meteorites can be divided into petrologic types analogous to those of the ordinary and CO type 3 chondrites. Axtell, Kaba, Leoville, Bali, Arch and ALHA81003 are type 3.0-3.1, while ALH84018, Efremovka, Grosnaja, Allende and Vigarano are type 3.2-3.3 and Coolidge and Loongana 001 are type 3.8. Mokoia is probably a breccia with regions ranging in petrologic type from 3.0 to 3.2. Renazzo often plots at the end of the reduced and oxidized CV chondrite trends, even when those trends diverge, suggesting that in many respects it resembles the unmetamorphosed precursors of the CV chondrites. The low-petrographic types and low-TL peak temperatures of all samples, including the CV3.8 chondrites, indicates metamorphism in the stability field of low feldspar (i.e., less than 800 C) and a metamorphic history similar to that of the CO chondrites but unlike that of the ordinary chondrites.

  5. Comparative 187Re-187Os systematics of chondrites: Implications regarding early solar system processes

    USGS Publications Warehouse

    Walker, R.J.; Horan, M.F.; Morgan, J.W.; Becker, H.; Grossman, J.N.; Rubin, A.E.

    2002-01-01

    A suite of 47 carbonaceous, enstatite, and ordinary chondrites are examined for Re-Os isotopic systematics. There are significant differences in the 187Re/188Os and 187Os/188Os ratios of carbonaceous chondrites compared with ordinary and enstatite chondrites. The average 187Re/188Os for carbonaceous chondrites is 0.392 ?? 0.015 (excluding the CK chondrite, Karoonda), compared with 0.422 ?? 0.025 and 0.421 ?? 0.013 for ordinary and enstatite chondrites (1?? standard deviations). These ratios, recast into elemental Re/Os ratios, are as follows: 0.0814 ?? 0.0031, 0.0876 ?? 0.0052 and 0.0874 ?? 0.0027 respectively. Correspondingly, the 187Os/188Os ratios of carbonaceous chondrites average 0.1262 ?? 0.0006 (excluding Karoonda), and ordinary and enstatite chondrites average 0.1283 ?? 0.0017 and 0.1281 ?? 0.0004, respectively (1?? standard deviations). The new results indicate that the Re/Os ratios of meteorites within each group are, in general, quite uniform. The minimal overlap between the isotopic compositions of ordinary and enstatite chondrites vs. carbonaceous chondrites indicates long-term differences in Re/Os for these materials, most likely reflecting chemical fractionation early in solar system history. A majority of the chondrites do not plot within analytical uncertainties of a 4.56-Ga reference isochron. Most of the deviations from the isochron are consistent with minor, relatively recent redistribution of Re and/or Os on a scale of millimeters to centimeters. Some instances of the redistribution may be attributed to terrestrial weathering; others are most likely the result of aqueous alteration or shock events on the parent body within the past 2 Ga. The 187Os/188Os ratio of Earth's primitive upper mantle has been estimated to be 0.1296 ?? 8. If this composition was set via addition of a late veneer of planetesimals after core formation, the composition suggests the veneer was dominated by materials that had Re/Os ratios most similar to ordinary and enstatite chondrites. ?? 2002 Elsevier Science Ltd.

  6. Rhenium-osmium isotope systematics of carbonaceous chondrites

    USGS Publications Warehouse

    Walker, R.J.; Morgan, J.W.

    1989-01-01

    Rhenium and osmium concentrations and Os isotopic compositions of eight carbonaceous chondrites, one LL3 ordinary chondrite, and two iron meteorites were determined by resonance ionization mass spectrometry. Iron meteorite 187Re/186Os and 187OS/186Os ratios plot on the previously determined iron meteorite isochron, but most chondrite data plot 1 to 2 percent above this meteorite isochron. This suggests either that irons have significantly younger Re-Os closure ages than chondrites or that chondrites were formed from precursor materials with different chemical histories from the precursors of irons. Some samples of Semarkona (LL3) and Murray (C2M) meteorites plot 4 to 6 percent above the iron meteorite isochron, well above the field delineated by other chondrites. Murray may have lost Re by aqueous leaching during its preterrestrial history. Semarkona could have experienced a similar loss of Re, but only slight aqueous alteration is evident in the meteorite. Therefore, the isotopic composition of Semarkona could reflect assembly of isotopically heterogeneous components subsequent to 4.55 billion years ago or Os isotopic heterogeneities in the primordial solar nebula.

  7. Crustal structure and igneous processes in a chondritic Io

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.

    1993-01-01

    Liquid sulfur can form when metal-free C1 or C2 chondrites are heated. It may be obtained either by direct melting of native sulfur in disequilibrated C1 or C2 chondrites or by incongruent melting of pyrite and other sulfides in thermodynamically equilibrated rocks of the same composition. Hence, Lewis considered C2 chondrites to be the best meteoritic analog for Io's bulk composition. Metal-bearing C3 and ordinary chondrites are too chemically reduced to yield liquid sulfur and are not thought to represent plausible analogs of Io's bulk composition. An important aspect of Lewis' work is that CaSO4 and MgSO4 are predicted to be important in Io. Real C1 and C2 chondrites contain averages of, respectively, 11 percent and 3 percent by mass of salts (plus water of hydration). The most abundant chondritic salts are magnesium and calcium sulfates, but other important components include sulfates of sodium, potassium, and nickel and carbonates of magnesium, calcium, and iron. It is widely accepted that chondritic salts are formed by low-temperature aqueous alteration. Even if Io originally did not contain salts, it is likely that aqueous alteration would have yielded several percent sulfates and carbonates. In any event, Io probably contains sulfates and carbonates. This report presents the results of a model of differentiation of a simplified C2 chondrite-like composition that includes 1.92 percent MgSO4, 0.56 percent CaSO4, 0.53 percent CaCO3, and 0.094 percent elemental sulfur. The temperature of the model is gradually increased; ensuing fractional melting results in these components extruding or intruding at gravitationally stable levels in Io's crust. Relevant phase equilibria were reviewed. A deficiency of high-pressure phase equilibria renders the present model qualitative.

  8. Thermal evolution and sintering of chondritic planetesimals

    NASA Astrophysics Data System (ADS)

    Henke, S.; Gail, H.-P.; Trieloff, M.; Schwarz, W. H.; Kleine, T.

    2012-01-01

    Aims: Radiometric ages for chondritic meteorites and their components provide information on the accretion timescale of chondrite parent bodies, and on cooling paths within certain areas of these bodies. However, to use this age information for constraining the internal structure, and the accretion and cooling history of the chondrite parent bodies, the empirical cooling paths obtained by dating chondrites must be combined with theoretical models of the thermal evolution of planetesimals. Important parameters in such thermal models include the initial abundances of heat-producing short-lived radionuclides (26Al and 60Fe), which are determined by the accretion timescale and the terminal size, chemical composition and physical properties of the chondritic planetesimals. The major aim of this study is to assess the effects of sintering of initially porous material on the thermal evolution of planetesimals, and to constrain the values of basic parameters that determined the structure and evolution of the H chondrite parent body. Methods: We present a new code for modelling the thermal evolution of ordinary chondrite parent bodies that initially are highly porous and undergo sintering by hot pressing as they are heated by decay of radioactive nuclei. The pressure and temperature stratification in the interior of the bodies was calculated by solving the equations of hydrostatic equilibrium and energy transport. The decrease of porosity of the granular material by hot pressing due to self-gravity was followed by solving a set of equations for the sintering of powder materials. For the heat-conductivity of granular material we combined recently measured data for highly porous powder materials, relevant for the surface layers of planetesimals, with data for heat-conductivity of chondrite material, relevant for the strongly sintered material in deeper layers. Results: Our new model demonstrates that in initially porous planetesimals heating to central temperatures sufficient for melting can occur for bodies a few km in size, that is, a factor of ?10 smaller than for compact bodies. Furthermore, for high initial 60Fe abundances small bodies may differentiate even when they had formed as late as 3-4 Ma after CAI formation. To demonstrate the capability of our new model, the thermal evolution of the H chondrite parent body was reconstructed. The model starts with a porous body that is later compacted first by "cold pressing" at low temperatures and then by "hot pressing" for temperatures above ?700 K, i.e., the threshold temperature for sintering of silicates. The thermal model was fitted to the well-constrained cooling histories of the two H chondrites Kernouvé (H6) and Richardton (H5). The best fit was obtained for a parent body with a radius of 100 km that accreted at t = 2.3 Ma after CAI formation, and had an initial 60Fe/56Fe = 4.1 × 10-7. Burial depths of 8.3 km and 36 km for Richardton and Kernouvé were able to reproduce their empirically determined cooling history. These burial depths are shallower than those derived in previous models. This reflects the strong insulating effect of the residual powder surface layer, which is characterised by a low thermal conductivity.

  9. The Wold Cottage meteorite: Not just any ordinary chondrite

    NASA Astrophysics Data System (ADS)

    Pillinger, C. T.; Pillinger, J. M.

    1996-09-01

    The Wold Cottage meteorite (fell, 1795), as is well known, played an important part in meteorites being accepted as stones from the sky. In most cases, the very select group of people who have been privileged to witness any meteorite fall, let alone one as important as Wold Cottage, enjoy a moment's fame but then disappear into obscurity. In this respect, Wold Cottage is very different; Edward Topham, the man who reported the fall and who became the meteorite's publicist, was already very well known for many other reasons. This fact contributed substantially to the evidence provided by his workmen being accepted, following two public exhibitions of the meteorite, the second after sworn testimonies were obtained. Here we explore Topham's background in order to reveal his character, particularly the value he placed on truth. When he passed the meteorite over to a public museum, he did so in the belief that he was acting for the benefit of posterity. At a time when the idea of meteorites being extraterrestrial was still controversial, the Wold Cottage stone vitally prompted the observation that specimens from different parts of the globe closely resembled each other, thus stimulating the crucial chemical analyses which verified that they were indeed related. During its first twenty years on Earth, the Wold Cottage meteorite was a prized specimen, a public attraction and sought after for scientific teaching purposes. In researching Wold Cottage, we have been able to discover information about many of the personalities who were involved in providing and studying the first few meteorites to become available for scientific research. The Wold Cottage story gives an interesting perspective on the cultural scene at the end of the eighteenth and beginning of the nineteenth centuries when there was no clear distinction between the arts and sciences, and meteoritics was the prerogative of often rather flamboyant gentlemen.

  10. In-Situ Oxygen Isotopic Composition of Tagish Lake: An Ungrouped Type 2 Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Engrand, Cecile; Gounelle, Matthieu; Zolensky, Mike E.

    2001-01-01

    We have measured the oxygen isotopic composition of several components of Tagish Lake by ion microprobe. This meteorite constitutes the best preserved sample of C2 matter presently available for study. It presents two different lithologies (carbonate-poor and -rich) which have fairly comparable oxygen isotopic composition, with regard to both the primary or secondary minerals. For the olivine and pyroxene grains, their delta O-18 values range from - 10.5% to + 7.4% in the carbonate-poor lithology, with a mean Delta O-17 value of - 3.7 2.4%. In the carbonate-rich lithology, delta O-18 varies from - 7.9% to + 3.3%, and the mean Delta O-17 value is - 4.7 +/- 1.4%. Olivine inclusions (Fo(sub >99)) with extreme O-16-enrichment were found in both lithologies: delta O-18 = - 46.1 %, delta O-187= - 48.3% and delta O-18 = - 40.6%, delta O-17 = - 41.2% in the carbonate-rich lithology; delta O-18 = - 41.5%, delta O-17 = -43.4%0 in the carbonate-poor lithology. Anhydrous minerals in the carbonate-poor lithology are slightly more O-16-rich than in the carbonate-rich one. Four low-iron manganese-rich (LIME) olivine grains do not have an oxygen isotopic composition distinct from the other "normal" olivines. The phyllosilicate matrix presents the same range of oxygen isotopic compositions in both lithologies: delta O-18 from approximately 11 % to approximately 6%, with an average Delta. O-17 approximately 0%. Because the bulk Tagish Lake oxygen isotopic composition given by Brown et al. is on the high end of our matrix analyses, we assume that this "bulk Tagish Lake" composition probably only represents that of the carbonate-rich lithology. Calcium carbonates have delta O-18 values up to 35%, with Delta O-17 approximately 0.5%0. Magnetite grains present very high Delta O-17 values approximately + 3.4%0 +/- 1.2%. Given our analytical uncertainties and our limited carbonate data, the matrix and the carbonate seem to have formed in isotopic equilibrium. In that case, their large isotopic fractionation would argue for a low temperature (CM-like, T approximately 0 deg) formation. Magnetite probably formed during a separate event. Tagish Lake magnetite data is surprisingly compatible with that of R-chondrites and unequilibrated ordinary (LL3) chondrites. Our oxygen isotope data strongly supports the hypothesis of a single precursor for both lithologies. Drastic mineralogical changes between the two lithologies not being accompanied with isotopic fractionation seem compatible with the alteration model presented by Young et aI. Tagish Lake probably represents the first well preserved large sample of the C2 matter that dominates interplanetary matter since the formation of the solar system.

  11. Paleomagnetism of enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Feng, H.; Weiss, B. P.; Tikoo, S. M.; Gattacceca, J.; Suavet, C. R.; Andrade Lima, E.

    2013-12-01

    Chondritic meteorites are widely thought to have originated on unmelted parent bodies. However, recent studies of CV carbonaceous chondrites have observed stable remanent magnetization acquired after accretion that may have been imparted by a core dynamo on the parent body. This suggests that CV chondrites may have originated from an internally melted, partially differentiated parent body with a relic chondritic crust. Although diverging from the predominant view that chondrites are samples of unmelted bodies, this idea has deep roots in the history of meteoritics. In particular, a common parent body has often been invoked for enstatite chondrites and enstatite achondrites (aubrites), which share many compositional, mineralogical, and isotopic similarities. Therefore, enstatite chondrites are a natural target for further testing the partial differentiation hypothesis. However, there are very few previous paleomagnetic studies of these meteorites. To address this, we studied the magnetic properties and paleomagnetism of three enstatite chondrites (Pillistfer EL6, Eagle EL6, and Sahara 97158 EH3) to examine the feasibility of dynamo generation on the enstatite chondrite parent body. In Pillistfer, our alternating field (AF) demagnetization of mutually oriented interior and fusion-crusted subsamples revealed three low coercivity components blocked from ~1.5-2.5 mT (component A1), ~2.5-7 mT (component A2), and ~7-9 mT (component A3). The A2 and A3 components are poorly defined, likely due to spurious anhysteretic remanent magnetization (ARM) acquired during AF demagnetization. Thermal demagnetization revealed low temperature (T1) and medium temperature (T2) components, ranging from 50-600°C and 600-700°C, respectively. The A1 and T1 components coincided, while the A2 and T2 components were more scattered (although nonrandomly distributed). Components A1 and A2 of fusion-crusted samples were similarly oriented to those of interior samples. The ratio of natural remanent magnetization (NRM) to isothermal remanent magnetization (IRM) over the A1 coercivity range is 10%. Combined with the failed fusion crust test, this high value of NRM/IRM suggests the sample has been partially, but not completely, remagnetized since arriving on Earth (perhaps by a hand magnet). Furthermore, we found that using AF paleointensity methods, we are only capable of recovering paleointensities from thermoremanence in Pillistfer down to 200 ?T, indicating it has poor magnetic recording properties and preventing us from obtaining paleointensities for the A2 and A3 components. Electron microscopy analyses of Pillistfer show the prevalence of FeNi metal with varying amounts of nickel (ranging in composition from kamacite into the taenite equilibrium fields and schriebersite as the most abundant ferromagnetic phases). Preliminary results on Eagle and Sahara 97158 enstatite chondrites indicate that, like in Pillistfer, the remanence is dominated by soft multidomain kamacite, making them poor paleomagnetic recorders. It is currently unclear whether enstatite chondrites may be suitable for retaining paleomagnetic fields imparted from a parent body-generated dynamo.

  12. Re-Os Systematics and HSE Distribution in Metal from Ochansk (H4) Chondrite

    NASA Technical Reports Server (NTRS)

    Smoliar, M. I.; Horan, M. F.; Alexander, C. M. OD.; Walker, R. J.

    2003-01-01

    Previous studies of the Re-Os systematics of chondrites have documented considerable variation in the Re/Os ratios of whole rock samples. For some whole rock chondrites, Re-Os systematics display large deviations from the primitive isochron that are considerably larger than deviations in other isotope systems. Possible interpretation of these facts is that the Re-Os system in chondrites is particularly sensitive to post-formation alteration processes, thus providing a useful tool to examine such processes. Significant variations that have been detected in highly siderophile element (HSE) patterns for ordinary chondrites support this conclusion. We report Re-Os isotope data for metal separates from the Ochansk H4 chondrite coupled with abundance data for Ru, Pd, Ir, and Pt, determined in the same samples by isotope dilution. We chose this meteorite mainly because it is an observed fall with minimal signs of weathering, and its low metamorphic grade (H4) and shock stage (S3).

  13. Chemical characteristic of R chondrites in the light of P, REEs, Th and U abundances

    NASA Astrophysics Data System (ADS)

    Khan, Rahat; Shirai, Naoki; Ebihara, Mitsuru

    2015-07-01

    Rare earth elements (REEs), Th, U and P were determined in 15 Rumuruti (R)-type chondrites and the Allende CV chondrite. Repeated analyses of Allende for REEs, Th and U by ICP-MS and P by ICP-AES, and comparisons of these data with literature values ensure high reproducibility (precision) and reliability (accuracy) of acquired data. CI-normalized REE abundances in R chondrites are slightly enriched in heavy REEs with a small, positive Ce anomaly, in contrast to Allende. CI-normalized Pr/Tm and Nd/Yb ratios show a positive correlation, suggesting the heterogeneous mixing of two components (CI-like and refractory-rich materials) during the accretion of the R chondrite parent body. A Ce anomaly, however, was likely homogeneously present in the nebula. A mean Th/U ratio of R chondrites is 3.81 ± 0.13 (1 ?), which is 5.1% higher than the CI ratio. Probably, the Th-U fractionation was inherited from the nebula from which the R chondrite parent body formed. Besides the Th-U fractionation, REEs and Th-U are heterogeneously fractionated in R chondrites, for which parent body processing is assumed to be the cause. A mean P content of R chondrites (1254 ?g/g) is higher than for any ordinary chondrite and is close to the EL mean. There appears to be a negative correlation between P and REEs contents in R chondrites. It is probable that REEs were diluted by extraneously supplied, REEs-depleted and P-containing materials (schreibersite or metal). This process must have occurred heterogeneously during accretion so that the heterogeneity of P-containing materials was preserved in the R chondrite parent body and individual R chondrites.

  14. Chondrites - Initial strontium-87/strontium-86 ratios and the early history of the solar system.

    NASA Technical Reports Server (NTRS)

    Wetherill, G. W.; Mark, R.; Lee-Hu, C.

    1973-01-01

    A sodium-poor, calcium-rich inclusion in the carbonaceous chondrite Allende had a Sr-87/Sr-86 ratio at the time of its formation of 0.69880, as low a value as that found in any other meteorite. The higher Sr-87/Sr-86 ratios found in ordinary chondrites indicate that their formation or isotopic equilibration occurred tens of millions of years later.

  15. The Concentrations of Some Refractory and Volatile Elements in CaS of Enstatite Chondrites

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Pernicka, E.; Sears, D. W. G.

    1993-07-01

    Oldhamite, being the carrier of REE in enstatite chondrites, may provide unique clues to the origin and history of the enstatite chondrites. We have previously reported that oldhamite grains from Qingzhen (EH3) contain 80% of the REE in the bulk rock [1], and this phase is highly enriched in several other refractory elements such as Sc, Th, and Hf. Perhaps surprisely, oldhamite are also enriched in the volatile chalcophile elements Se, Br, and Zn. This suggests interactions at low temperature [2]. Here we report INAA data for the REE, Sc, Se, Br, and Zn in CaS extracted from five enstatite chondrites (Qingzhen EH3, St. Marks EH5, Atlanta EL6, Hvittis EL6, and Pillistfer EL6) using a diamond drill attached to a standard microscope. Nine CaS grains from Qingzhen were analyzed, two from St. Marks and one from each of remaining meteorites. We found that the REE abundances in CaS from higher petrologic types are much lower than from unequilibrated enstatite chondrite, Qingzhen (Table 1). Similarly, the abundances of Sc, Se, Br, and Zn in the CaS from Qingzhen are higher than that in CaS grains from equilibrated chondrites. Since both refractory and volatile element abundances decrease with petrologic type, the high abundances of these elements must reflect primary (i.e. pre-metamorphic) process. We conclude first, the CaS grains from enstatite chondrites are not simply residues of an evaporative process, as suggested by thermodynamic models for the REE patterns observed in the CaS [1,3-7], since such material would be depleted in volatiles. Secondly, metamorphism has caused considerable redistribution of the trace elements among the minerals in most enstatite chondrites. References: [1] Chen et al. (1992) Chinese J. Space Sci., 12, 129-138. [2] Chen et al. (1989) Meteoritics, 24, 258. [3] Larimer J. W. and Ganapathy R. (1987) EPSL, 84, 123-134. [4] Lundberg L. L. and Crozaz G. (1988) Meteoritics, 23, 285-286. [5] Lundberg L. L. et al. (1989) Meteoritics, 24, 296. [6] Lundberg L. L. et al., (1991) LPSC, XXII, 835-836. [7] Lodders K. and Fegley B. (1993) EPSL (in press). Table 1, which appears here in the hard copy, shows CI-normalized element abundances in CaS extracted from enstatite chondrites.

  16. A search for spectral alteration effects in chondritic gas-rich breccias

    NASA Technical Reports Server (NTRS)

    Bell, J. F.; Keil, Klaus

    1987-01-01

    Several samples of gas-rich breccias were selected, including slabs of the Kapoeta howardite, the ordinary chondrites Dubrovnik, Cangas de Onis, and Dimmit. Numerous 0.8 to 2.5 micron reflection spectra of selected areas on sawed or broken surfaces were measured with the Planetary Geosciences Division spectrogoniometer. While these spectra are not directly comparable to those of powered samples, comparisons within the data set should reveal any spectral differences due to weathering. These results indicate that unknown regolith processes do not confer the ordinary-chondrite parent bodies with an altered layer exhibiting S-class spectral properties. This is consistent with recent interpretations of the new Q-class of asteroids as the ordinary-chondrite parent bodies. However, significant spectral effects do occur in asteroid regoliths: darkening and suppression of absorption bands in highly shocked material, as seen previously in the so-called black chondrites; and segregation of metal in large impact melt pools on chondritic asteroids, which may have achondritic spectra. Neither of these effects is likely to be significant in interpreting current integral-disk spectra, but should be searched for in spectral maps returned by future spacecraft.

  17. Temperature and Oxygen Fugacity Constraints on CK and R Chondrites and Implications for Water and Oxidation in the Early Solar System

    NASA Technical Reports Server (NTRS)

    Righter, K.; Neff, K. E.

    2007-01-01

    Recent chondritic meteorite finds in Antarctica have included CB, CH, CK and R chondrites, the latter two of which are among the most oxidized materials found in meteorite collections. In this study we present petrographic and mineralogic data for a suite of CK and R chondrites, and compare to previous studies of CK and R, as well as some CV chondrites. In particular we focus on the opaque minerals magnetite, chromite, sulfides, and metal as well as unusual silicates hornblende, biotite, and plagioclase. Several mineral thermometers and oxy-barometers are utilized to calculate temperatures and oxygen fugacities for these unusual meteorites compared to other more common chondrite groups. R and CK chondrites show lower equilibrium temperatures than ordinary chondrites, even though they are at similar petrologic grades (e.g., thermal type 6). Oxygen fugacity calculated for CV and R chondrites ranges from values near the iron-wustite (IW) oxygen buffer to near the fayalite-magnetite-quartz (FMQ) buffer. In comparison, the fO2 recorded by ilmenite-magnetite pairs from CK chondrites are much higher, from FMQ+3.1 to FMQ+5.2. The latter values are the highest recorded for materials in meteorites, and place some constraints on the formation conditions of these magnetite-bearing chondrites. Differences between mineralogic and O isotopic compositions of CK and R chondrites suggest two different oxidation mechanisms, which may be due to high and low water: rock ratios during metamorphism, or to different fluid compositions, or both.

  18. Ar-40/Ar-39 dating of collisional events in chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Bogard, D. D.; Wright, R. J.; Husain, L.

    1976-01-01

    Ar-40/Ar-39 age dating of a number of shocked ordinary chondrites is interpreted in terms of collisional degassing events of meteorite parent bodies, probably in the asteroid belt. Examples of L, H, and at least one LL chondrite show episodic degassing. Degassing ages suggest several distinct events ranging from about 0.03 aeon to 0.7 aeon and probably higher. All specimens of either the H or L chondrites are not consistent with a single age event. A direct correlation exists between the degree of shock heating and the fraction of argon lost during degassing. However, no chondrite yet analyzed shows complete degassing of its high-temperature phase. Consequently, whole rock K-Ar ages are not accurate monitors of the time of the shock event.

  19. Cat Mountain: A meteoritic sample of an impact-melted chondritic asteroid

    NASA Technical Reports Server (NTRS)

    Kring, David A.

    1993-01-01

    Although impact cratering and collisional disruption are the dominant geologic processes affecting asteroids, samples of impact melt breccias comprise less than 1 percent of ordinary chondritic material and none exist among enstatite and carbonaceous chondrite groups. Because the average collisional velocity among asteroids is sufficiently large to produce impact melts, this paucity of impact-melted material is generally believed to be a sampling bias, making it difficult to determine the evolutionary history of chondritic bodies and how impact processes may have affected the physical properties of asteroids (e.g., their structural integrity and reflectance spectra). To help address these and related issues, the first petrographic description of a new chondritic impact melt breccia sample, tentatively named Cat Mountain, is presented.

  20. Chondrite thermal histories from Low-CA pyroxene microstructures: Autometamorphism versus prograde metamorphism revisited

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.; Jones, Rhian H.; Papike, J. J.

    1993-01-01

    In order to constrain the thermal histories of chondritic meteorites, a detailed study of the microstructures of low-Ca pyroxenes produced experimentally and in types 4 and 5 ordinary chondrites was carried out. Cooling experiments on synthetic MgSiO3 at cooling rates between 2 and 10000 C/hr from the protopyroxene stability field into that of orthopyroxene (OPX) were performed and the products of these experiments were annealed for a variety of annealing times. There are clear microstructural differences between samples which were cooled and those which were subsequently annealed. A comparison of the microstructures observed in the experimental samples with those in H4-5 ordinary chondrites shows that they cannot have experienced a single stage cooling history, as proposed for the autometamorphism model.

  1. On the Relationship between Cosmic Ray Exposure Ages and Petrography of CM Chondrites

    NASA Technical Reports Server (NTRS)

    Takenouchi, A.; Zolensky, M. E.; Nishiizumi, K.; Caffee, M.; Velbel, M. A.; Ross, K.; Zolensky, A.; Lee, L.; Imae, N.; Yamaguchi, A.; Mikouchi, T.

    2014-01-01

    Carbonaceous (C) chondrites are potentially the most primitive among chondrites because they mostly escaped thermal metamorphism that affected the other chondrite groups. C chondrites are chemically distinguished from other chondrites by their high Mg/Si ratios and refractory elements, and have experienced various degrees of aqueous alteration. They are subdivided into eight subgroups (CI, CM, CO, CV, CK, CR, CB and CH) based on major element and oxygen isotopic ratios. Their elemental ratios vary over a wide range, in contrast to those of ordinary and enstatite chondrites which are relatively uniform. It is critical to know how many separate bodies are represented by the C chondrites. In this study we defined 4 distinct cosmic-ray exposure (CRE) age groups of CMs and systematically characterized the petrography in each of the 4 CRE age groups to determine whether the groups have significant petrographic differences with such differences probably reflecting different parent body (asteroid) geological processing, or multiple original bodies. We have reported the results of a preliminary grouping at the NIPR Symp. in 2013 [3], however, we revised the grouping and here report our new results.

  2. Chondritic Asteroids--When Did Aqueous Alteration Happen?

    NASA Astrophysics Data System (ADS)

    Doyle, P. M.

    2015-06-01

    Using a synthesized fayalite (Fe2SiO4) standard for improved 53Mn-53Cr radiometric age dating, Patricia Doyle (previously at the University of Hawaii and now at the University of Cape Town, South Africa) and coauthors from Hawaii, the National Astronomical Observatory of Japan, University of Chicago, and Lawrence Livermore National Laboratory in California, analyzed aqueously formed fayalite in the ordinary chondrite Elephant Moraine 90161 (L3.05) and in the carbonaceous chondrites Asuka 881317 (CV3) and MacAlpine Hills 88107 (CO3-like) from Antarctica. The data obtained indicate that liquid water existed - and aqueous alteration started - on the chondritic parent bodies about three million years earlier than previously determined. This discovery has implications for understanding when and where the asteroids accreted. The 53Mn-53Cr chronology of chondrite aqueous alteration, combined with thermodynamic calculations and physical modeling, signifies that hydrated asteroids, at least those sampled by meteorites, accreted in the inner Solar System (2-4 AU) near the main asteroid belt 2-4 million years after the beginning of the Solar System, rather than migrating inward after forming in the Solar System's colder, outer regions beyond Jupiter's present orbit (5-15 AU).

  3. The Tsarev meteorite - Petrology and bidirectional reflectance spectra of a shock-blackened L chondrite

    NASA Technical Reports Server (NTRS)

    Britt, D. T.; Pieters, C. M.; Petaev, M. I.; Zaslavskaia, N. I.

    1989-01-01

    The Tsarev meteorite is a highly shocked black L5 ordinary chondrite. Meteorites of this class may have been subjected to regolith processes on or near the surface of ordinary chondrite bodies. The study of their optical alteration can provide valuable support in the spectral search for ordinary chondrite parent bodies. Although Tsarev is very dark in a cut-surface hand sample, it is characterized by subtle variations in apparent darkness, called in this work grey and black areas. Both areas are substantially optically altered from normal ordinary chondrites and are characterized by a much lower albedo and strongly suppressed absorption features. Although both areas are altered, they show differences in albedo and the strength of absorption features. Particulate samples from the black area have a slightly higher albedo and stronger absorption features, while the particulate samples from the grey area show a systematic suppression of spectral features and albedo. Chemical, mineralogical, and spectral analyses suggest that the spectral differences can be the result of one or a combination of several factors, including shock effects on the crystallographic structure of the minerals and differences in the size, distribution, and amount of metal and troilite grains.

  4. Magnesium isotopic composition of the Earth and chondrites

    NASA Astrophysics Data System (ADS)

    Teng, Fang-Zhen; Li, Wang-Ye; Ke, Shan; Marty, Bernard; Dauphas, Nicolas; Huang, Shichun; Wu, Fu-Yuan; Pourmand, Ali

    2010-07-01

    To constrain further the Mg isotopic composition of the Earth and chondrites, and investigate the behavior of Mg isotopes during planetary formation and magmatic processes, we report high-precision (±0.06‰ on ? 25Mg and ±0.07‰ on ? 26Mg, 2SD) analyses of Mg isotopes for (1) 47 mid-ocean ridge basalts covering global major ridge segments and spanning a broad range in latitudes, geochemical and radiogenic isotopic compositions; (2) 63 ocean island basalts from Hawaii (Kilauea, Koolau and Loihi) and French Polynesia (Society Island and Cook-Austral chain); (3) 29 peridotite xenoliths from Australia, China, France, Tanzania and USA; and (4) 38 carbonaceous, ordinary and enstatite chondrites including 9 chondrite groups (CI, CM, CO, CV, L, LL, H, EH and EL). Oceanic basalts and peridotite xenoliths have similar Mg isotopic compositions, with average values of ? 25Mg = -0.13 ± 0.05 (2SD) and ? 26Mg = -0.26 ± 0.07 (2SD) for global oceanic basalts ( n = 110) and ? 25Mg = -0.13 ± 0.03 (2SD) and ? 26Mg = -0.25 ± 0.04 (2SD) for global peridotite xenoliths ( n = 29). The identical Mg isotopic compositions in oceanic basalts and peridotites suggest that equilibrium Mg isotope fractionation during partial melting of peridotite mantle and magmatic differentiation of basaltic magma is negligible. Thirty-eight chondrites have indistinguishable Mg isotopic compositions, with ? 25Mg = -0.15 ± 0.04 (2SD) and ? 26Mg = -0.28 ± 0.06 (2SD). The constancy of Mg isotopic compositions in all major types of chondrites suggest that primary and secondary processes that affected the chemical and oxygen isotopic compositions of chondrites did not significantly fractionate Mg isotopes. Collectively, the Mg isotopic composition of the Earth's mantle, based on oceanic basalts and peridotites, is estimated to be -0.13 ± 0.04 for ? 25Mg and -0.25 ± 0.07 for ? 26Mg (2SD, n = 139). The Mg isotopic composition of the Earth, as represented by the mantle, is similar to chondrites. The chondritic composition of the Earth implies that Mg isotopes were well mixed during accretion of the inner solar system.

  5. Opaque Mineral Assemblages at Chondrule Boundaries in the Vigarano CV Chondrite: Evidence for Gas-Solid Reactions Following Chondrule Formation

    NASA Technical Reports Server (NTRS)

    Lauretta, Dante S.

    2004-01-01

    Recent studies of opaque minerals in primitive ordinary chondrites suggest that metal grains exposed at chondrule boundaries were corroded when volatile elements recondensed after the transient heating event responsible for chondrule formation. Metal grains at chondrule boundaries in the Bishunpur (LL3.1) chondrite are rimmed by troilite and fayalite. If these layers formed by gas solid reaction, then the composition of the corrosion products can provide information on the chondrule formation environment. Given the broad similarities among chondrules from different chondrite groups, similar scale layers should occur on chondrules in other primitive meteorite groups. Here I report on metal grains at chondrule boundaries in Vigarano (CV3).

  6. On Ordinary forms and Ordinary Galois representations

    E-print Network

    ]). In such a situation, we say that ae is a modular mod p Galois representation. To make this more precise, let us fix in the space Sk( 0(N), O) of newforms of weight k (throughout 1 #12 as far as we are aware, has not been addressed before. We are interested in studying ordinary Galois

  7. Effect of metamorphism on isolated olivine grains in CO3 chondrites

    NASA Technical Reports Server (NTRS)

    Jones, Rhian H.

    1993-01-01

    The presence of a metamorphic sequence in the CO3 chondrite group has been shown previously to result in changes in properties of chondrule silicates. However, the role of isolated olivine grains during metamorphism of these chondrites has not been addressed. Isolated olivine grains in two metamorphosed CO3 chondrites, Lance and Isna, have been investigated in this study in order to assess the compositional properties of isolated olivine grains that may be attributable to metamorphism. Compositional changes in isolated olivines with increasing petrologic subtype are very similar to changes in chondrule olivines in the same chondrites. Olivine compositions from all occurrences (chondrules, 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 olivine, 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 olivine 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.

  8. Formation and Processing of Amorphous Silicates in Primitive Carbonaceous Chondrites and Cometary Dust

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Messenger, S.

    2012-01-01

    Chondritic-porous interplanetary dust particles (CP IDPs) exhibit strongly heterogeneous and unequilibrated mineralogy at sub-micron scales, are enriched in carbon, nitrogen and volatile trace elements, and contain abundant presolar materials [1-4]. These observations suggest that CP IDPs have largely escaped the thermal processing and water-rock interactions that have severely modified or destroyed the original mineralogy of primitive meteorites. CP IDPs are believed to represent direct samples of the building blocks of the Solar System - a complex mixture of nebular and presolar materials largely unperturbed by secondary processing. The chemical and isotopic properties of CP IDPs and their atmospheric entry velocities are also consistent with cometary origins. GEMS (glass with embedded metal and sulfides) grains are a major silicate component of CP IDPs. GEMS grains are < 0.5 microns in diameter objects that consist of numerous 10 to 50 nm-sized Fe-Ni metal and Fe-Ni sulfide grains dispersed in a Mg-Si-Al-Fe amorphous silicate matrix [2, 5]. Based on their chemistry and isotopic compositions, most GEMS appear to be non-equilibrium condensates from the early solar nebula [2]. If GEMS grains are a common nebular product, then they should also be abundant in the matrices of the most physically primitive chondritic meteorites. Although amorphous silicates are common in the most primitive meteorites [6-9], their relationship to GEMS grains and the extent to which their compositions and microstructure have been affected by parent body processing (oxidation and aqueous alteration) is poorly constrained. Here we compare and contrast the chemical, microstructural and isotopic properties of amorphous silicates in primitive carbonaceous chondrites to GEMS grains in IDPs.

  9. Studies of kamacite, perryite and schreibersite in E-chondrites and aubrites

    NASA Astrophysics Data System (ADS)

    Easton, A. J.

    1986-03-01

    The bulk composition of metal (kamacite plus perryite) was determined in eleven E-chondrites and eight aubrites. The data are compatible with the subdivision of the E-chondrites into two groups (Yavnel, 1963; Anders, 1964), St Mark's and St Sauveur belonging to type I (Easton, 1985). The Ni content of kamacite plus perryite in Kota Kota (5.49 percent) is within the range covered by the remaining E-chondrites. Normative perryite constitutes 2.1 percent of Kota Kota and 2.7 percent of South Oman. The Ni content in the bulk metal of Aubres, Bishopville, Norton County and Pena Blanca Spring is about half the average Ni content in the metal of E-chondrites or the remaining aubrites (Bustee, Khor Temiki, Mayo Belwa and Shallowater). High Ga/Ni ratios distinguish the metal in E-chondrites and aubrites from that in ordinary chondrites. The composition of both bulk metal and individual grains in aubrites makes it unlikely that they represent residual metal trapped during magmatic differentation and/or fractional crystallization of E6 material. Compositional differences between metal grains strongly indicate that the aubrites are polymict breccias.

  10. Chondrites, S asteroids, and space weathering: Thumping noises from the coffin?

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Clark, B. E.

    1993-01-01

    Most of the spectral characteristics of ordinary chondrites and S-asteroids in the visible and infrared can be reduced to three numerical values. These values represent the depth of the absorption band resulting from octahedrally coordinated Fe(sup 2+), the reflectance at 0.56 microns and the slope of the continuum (as measured according to convention). By plotting these three characteristics, it is possible to immediately compare the spectral characteristics of large numbers of ordinary chondrites and S-asteroids. Commonality of spectral characteristics between these populations can thus be evaluated on the basis of overlap in position on three two-coordinate systems: albedo vs. band depth, band depth vs. slope, and slope vs. albedo. In order to establish identity, members of the two populations must overlap on all three of these independent parameter spaces. In this coordinate system, spectra of 23 ordinary chondrites (representing all metamorphic grades), and 39 S-asteroids were compared. It was found that there was no overlap between the two populations in terms of the slope vs. band depth parameters, nor were most chondrites identical to the S-asteroids with respect to the other criteria. However, the controversial question remains: Where are the parent bodies of the chondrites? Perhaps an even more critical question is: Where are our samples of the S-asteroids? Considering the geography of the asteroid belt and the theory that early solar-system electromagnetic induction heating differentiated protoasteroids in the inner portion of the main belt, it was suggested that although S-asteroids and ordinary chondrites have very similar mineralogy, the S-asteroids are mixtures of metallic nickel iron and silicates which resulted from magmatism induced by electromagnetic heating whereas chondrites were only slightly metamorphosed nebular condensates. In this scenario chondrites would have been derived from a population of bodies with thermal lag times so short that they were not subjected to melting during the phase of the electromagnetic induction heating event but only to various degrees of pervasive metamorphism. Furthermore, these objects would then have been too small to be observed and systematically included in the library of asteroidal spectra. It was also suggested that the parametric distribution of S-asteroid spectra could be reproduced by mixing various proportions of NiFe meteorite and achondritic materials. This has also been demonstrated in the laboratory.

  11. Solving Ordinary Differential Equations

    NASA Technical Reports Server (NTRS)

    Krogh, F. T.

    1987-01-01

    Initial-value ordinary differential equation solution via variable order Adams method (SIVA/DIVA) package is collection of subroutines for solution of nonstiff ordinary differential equations. There are versions for single-precision and double-precision arithmetic. Requires fewer evaluations of derivatives than other variable-order Adams predictor/ corrector methods. Option for direct integration of second-order equations makes integration of trajectory problems significantly more efficient. Written in FORTRAN 77.

  12. ALH85085: a unique volatile-poor carbonaceous chondrite with possible implications for nebular fractionation processes

    USGS Publications Warehouse

    Grossman, J.N.; Rubin, A.E.; MacPherson, G.J.

    1988-01-01

    Allan Hills 85085 is a unique chondrite with affinities to the Al Rais-Renazzo clan of carbonaceous chondrites. Its constituents are less than 50 ??m in mean size. Chondrules and microchondrules of all textures are present; nonporphyritic chondrules are unusually abundant. The mean compositions of porphyritic, nonporphyritic and barred olivine chondrules resemble those in ordinary chondrites except that they are depleted in volatile elements. Ca-, Al-rich inclusions are abundant and largely free of nebular alteration; they comprise types similar to those in CM and CO chondrites, as well as unique types. Calcium dialuminate occurs in several inclusions. Metal, silicate and sulfide compositions are close to those in CM-CO chondrites and Al Rais and Renazzo. C1-chondrite clasts and metal-rich "reduced" clasts are present, but opaque matrix is absent. Siderophile abundances in ALH85085 are extremely high (e.g., Fe Si = 1.7 ?? solar), and volatiles are depleted (e.g., Na Si = 0.25 ?? solar, S Si = 0.03 ?? solar). Nonvolatile lithophile abundances are similar to those in Al Rais, Renazzo, and CM and CO chondrites. ALH85085 agglomerated when temperatures in the nebula were near 1000 K, in the same region where Renazzo, Al Rais and the CI chondrites formed. Agglomeration of high-temperature material may thus be a mechanism by which the fractionation of refractory lithophiles occurred in the nebula. Chondrule formation must have occurred at high temperatures when clumps of precursors were small. After agglomeration, ALH85085 was annealed and lightly shocked. C1 and other clasts were subsequently incorporated during late-stage brecciation. ?? 1988.

  13. Reflectance spectra of primitive chondrites

    NASA Astrophysics Data System (ADS)

    Trigo-Rodríguez, J. M.; Moyano-Cambero, C. E.; Llorca, J.

    2013-05-01

    We are studying a wide sample of pristine carbonaceous chondrites from the NASA Antarctic collection in order to get clues on the physico-chemical processes occurred in the parent bodies of these meteorites. We are obtaining laboratory reflectance spectra of different groups of carbonaceous chondrites, but here we focus in CM and CI chondrites. We discuss the main spectral features that can be used to identify primitive carbonaceous asteroids by remote sensing techniques. Two different spectrometers were used covering the entire 0.3 to 30 ?m electromagnetic window. Only a handful of Near Earth Objects (NEOs) exhibit bands or features clearly associated with aqueous alteration. Among them are the target asteroids of Osiris Rex and Marco Polo-R missions.

  14. Serpentine Nanotubes in CM Chondrites

    NASA Technical Reports Server (NTRS)

    Zega, Thomas J.; Garvie, Laurence A. J.; Dodony, Istvan; Buseck, Peter R.

    2004-01-01

    The CM chondrites are primitive meteorites that formed during the early solar system. Although they retain much of their original physical character, their matrices and fine-grained rims (FGRs) sustained aqueous alteration early in their histories [1- 3]. Serpentine-group minerals are abundant products of such alteration, and information regarding their structures, compositions, and spatial relationships is important for determining the reactions that produced them and the conditions under which they formed. Our recent work on FGRs and matrices of the CM chondrites has revealed new information on the structures and compositions of serpentine-group minerals [4,5] and has provided insights into the evolution of these primitive meteorites. Here we report on serpentine nanotubes from the Mighei and Murchison CM chondrites [6].

  15. Magnetite-sulfide chondrules and nodules in CK carbonaceous chondrites - Implications for the timing of CK oxidation

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1993-01-01

    CK carbonaceous chondrites contain rare (about 0.1 vol pct) magnetite-sulfide chondrules 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 chondrules in CK chondrites. It seems likely that the magnetite-sulfide chondrules constitute the subset of magnetite-sulfide nodules that escaped as immiscible droplets from their molten silicate chondrule hosts during chondrule formation. The intactness of the magnetite-sulfide chondrules 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.

  16. Spectral alteration effects in chondritic gas-rich breccias - Implications for S-Class and Q-Class asteroids

    NASA Technical Reports Server (NTRS)

    Bell, Jeffrey F.; Keil, Klaus

    1988-01-01

    Reflection spectra were obtained from sawed or freshly broken surfaces of gas-rich matrix regions in a number of ordinary chondrites (Dubrovnik, Cangas de Onis, Olivenza, and Dimmitt) which are believed to represent lithified portions of asteroid regoliths that were once directly exposed to space, with the purpose of relating these chondrites to Class S asteroids. However, the observations did not detect curved red continuum characteristic for Class S asteroid spectra, suggesting that it is unlikely for any well-observed Class S asteroid to be a source of ordinary chondrites. It is suggested that the newly discovered spectral class 'Q', of which asteroid 1982 Apollo is the prototype, provides a viable alternative of a parent body.

  17. Petrology and geochemistry of chondrules and metal in NWA 5492 and GRO 95551: A new type of metal-rich chondrite

    NASA Astrophysics Data System (ADS)

    Weisberg, Michael K.; Ebel, Denton S.; Nakashima, Daisuke; Kita, Noriko T.; Humayun, Munir

    2015-10-01

    Northwest Africa (NWA) 5492 and Grosvenor Mountains (GRO) 95551 are metal-rich chondrites having silicate (olivine and pyroxene) compositions that are more reduced than those in other metal-rich chondrites, such as the CH and CB chondrites. Additionally, sulfides in NWA 5492 and GRO 95551 are more abundant and not related to the metal, as in the CB chondrites. Average metal compositions in NWA 5492 and GRO 95551 are close to H chondrite metal. Oxygen isotope ratios of NWA 5492 and GRO 95551 components (chondrules and fragments) show a range of compositions with most having ?17O values >0‰. Since there is no matrix component, their average chondrule + fragment oxygen isotopic compositions are considered to be representative of whole rock and (?17O values) are sandwiched between the values for enstatite (E) and ordinary (O) chondrites. These data argue for a close relationship between NWA 5492 and GRO 95551 and suggest that they are the first examples of a new type of metal-rich chondrite. Oxygen isotope ratios of chondrules in NWA 5492 and GRO 95551 show considerable overlap with chondrules in O, E and R chondrites, with average compositions indistinguishable from LL3 chondrules, suggesting considerable mixing between these Solar System materials during chondrule formation and/or that their precursors experienced similar formation environments and/or processes. Another characteristic shared between NWA 5492 and GRO 95551 and O, E and R chondrites is that they are all relatively dry (low abundances of hydrated minerals), compared to many C chondrites and have fewer, smaller CAIs than many C chondrites. (No CAIs were found in NWA 5492 or GRO 95551 but they contain rare Al-rich chondrules.) We suggest that O, E, R and the NWA 5492 and GRO 95551 chondrites are closely related Solar System materials.

  18. Aqueous activity and sources of water on the chondrite parent asteroids

    NASA Astrophysics Data System (ADS)

    Krot, A.; Alexander, C.; Nagashima, K.; Ciesla, F.; Fujiya, W.

    2014-07-01

    Ages of aqueous alteration of asteroids: Most chondrite parent asteroids experienced aqueous alteration resulting in the formation of secondary minerals, including phyllosilicates, magnetite, Fe,Ni-sulfides, carbonates [(Ca,Mg,Fe,Mn)CO_3)], and fayalite [(Fe,Mn)_2SiO_4] [1]. Mineralogical observations and thermodynamic analysis suggest that the alteration of the various chondrite groups occurred under different physico-chemical conditions (temperature, redox conditions, pH, water/rock ratio). The chronology of aqueous activity on the chondrite parent asteroids can be inferred from ^{53}Mn-^{53}Cr dating (^{53}Mn decays to ^{53}Cr with half-life of 3.7 Myr) of aqueously-formed carbonates and fayalite measured with secondary ion mass-spectrometry. Recently reported ^{53}Mn-^{53}Cr ages of carbonates in CM [2,3], CI [4], CR [5] chondrites, and fayalite in CV [6], CO [6], and LL [7] chondrites indicate that aqueous alteration on the ordinary and carbonaceous chondrite (CC) parent asteroids occurred nearly contemporaneously, ˜3-5 Myr after formation of Ca,Al-rich inclusions (CAIs), the earliest Solar System solids dated [8]. Accretion ages of chondrite parent asteroids: Assuming uniform distribution of a short-lived radionuclide ^{26}Al (decays to ^{26}Mg with half-life of ˜0.7 Myr) in the disk at the canonical level (^{26}Al/^{27}Al ˜5×10^{-5}), the timing of aqueous alteration combined with estimates of peak metamorphic temperatures and thermal modelling of the ordinary and CC parent asteroids suggest that these bodies accreted ˜2-3 Myr after CAI formation [2,3,7]. The inferred accretion ages of ordinary and CC parent asteroids are generally consistent with average ^{26}Al-^{26}Mg ages (^{26}Al decays to ^{26}Mg with half-life of ˜0.7 Myr) of their chondrules [9,10], suggesting that chondrule formation was rapidly followed by accretion and that ^{26}Al was the major heating source of aqueous alteration and thermal metamorphism on these bodies. The observed variations in the degree of aqueous alteration within a chondrite group may indicate that water ices accreted heterogeneously or that there was a fluid flow in their parent bodies. Sources of water on the chondrite parent asteroids: According to the Grand Tack and Nice models, the extensively hydrated (C-, D-, and P-type) asteroids formed between and beyond the giant planets and were scattered into the main asteroid belt during a period of giant planet migration [11,12]. Bulk D/H ratio of chondrite water ices can potentially be used for testing this model, but cannot be measured directly. Alexander et al. [13] used the bulk hydrogen and carbon isotopic compositions of chondrites to estimate the water D/H ratio for a number of chondrite groups. The estimated D/H ratio of water in the extensively hydrated CI, CM, CR and ungrouped carbonaceous chondrite Tagish Lake (spectrally similar to D-type asteroids) are significantly lower than in the measured comets from Oort Cloud comets; the D/H ratio of water in CRs, however, is similar to that in the Jupiter Family Comet Hartley 2 [14]. Alexander et al. [13] concluded that CC parent asteroids accreted ˜3-7 au from the Sun. These data provide important constraints on the Grand Tack and Nice models.

  19. The Carlisle Lakes-type chondrites: A new grouplet with high. Delta. sup 17 O and evidence for nebular oxidation

    SciTech Connect

    Weisberg, M.K. Brooklyn Coll., NY ); Prinz, M. ); Kojima, Hideyasu; Yanai, Keizo ); Clayton, R.N.; Mayeda, T.K. )

    1991-09-01

    Carlisle Lakes, ALH85151, and Y75302 are similar ungrouped chondrites which have petrologic and bulk compositional similarities to the ordinary chondrites, but are more oxidized; and their oxygen isotopic compositions differ. They represent a new grouplet which the authors call the Carlisle Lakes-type chondrites. They have the highest {Delta}{sup 17}O values (up to 2.91) measured to date. The whole chondrites and most of their chondrules plot on the same mass fractionation line on an oxygen 3-isotope diagram. They are olivine rich (>70 vol%), essentially metal free, and most olivine is FeO rich, equilibrated at Fa{sub 38}. Rare olivine and pyroxene grains in chondrules and fragments are zoned, and these are important in discerning the history of these chondrites. The zoning does not appear to have formed during crystallization from a melt droplet chondrule, but post-dated chondrule formation. Two hypotheses are postulated to explain the zoning: (1) parent-body thermal metamorphism and (2) nebular gas-solid exchange reactions accompanied by condensation of new FeO-rich olivine, utilizing existing olivine surfaces as nucleation sites. The occurrence of steep Fe-Mg compositional gradients of core-to-rim profiles, oscillatory zoning in olivine, fayalitic rims of Fa{sub 45} that exceed instead of approach the equilibrium composition of the matrix (Fa{sub 38}), and olivine-filled veins in zoned pyroxenes are more compatible with the nebular hypothesis. The Carlisle Lakes-type chondrites may have originally been derived from an ordinary chondrite-like precursor which was later oxidized, prior to its final lithification. However, the oxygen isotopic compositions of the whole chondrites and most of their chondrules suggest that the precursor probably formed in an oxygen isotopically distinct environment.

  20. Igneous Graphite in Enstatite Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Igneous graphite. a rare constituent in terrestrial mafic and ultramafic rocks. occurs in three EH and one EL enstatite chondrite impact-melt breccias as 2-150 Ilm long euhedrallaths. some with pyramidal terminations. In contrast. graphite in most enstatite chondrites exsolved from metallic Fe-Ni as polygonal. rounded or irregular aggregates. Literature data for five EH chondrites on C combusting at high temperatures show that Abee contains the most homogeneous C isotopes (i.e. delta(sup 13)C = -8.1+/-2.1%); in addition. Abee's mean delta(sup l3)C value is the same as the average high-temperature C value for the set of five EH chondrites. This suggests that Abee scavenged C from a plurality of sources on its parent body and homogenized the C during a large-scale melting event. Whereas igneous graphite in terrestrial rocks typically forms at relatively high pressure and only moderately low oxygen fugacity (e.g., approx. 5 kbar. logfO2, approx. -10 at 1200 C ). igneous graphite in asteroidal meteorites formed at much lower pressures and oxygen fugacities.

  1. Petrography, stable isotope compositions, microRaman spectroscopy, and presolar components of Roberts Massif 04133: A reduced CV3 carbonaceous chondrite

    PubMed Central

    Davidson, Jemma; Schrader, Devin L; Alexander, Conel M O'D; Lauretta, Dante S; Busemann, Henner; Franchi, Ian A; Greenwood, Richard C; Connolly, Harold C; Domanik, Kenneth J; Verchovsky, Alexander

    2014-01-01

    Here, we report the mineralogy, petrography, C-N-O-stable isotope compositions, degree of disorder of organic matter, and abundances of presolar components of the chondrite Roberts Massif (RBT) 04133 using a coordinated, multitechnique approach. The results of this study are inconsistent with its initial classification as a Renazzo-like carbonaceous chondrite, and strongly support RBT 04133 being a brecciated, reduced petrologic type >3.3 Vigarano-like carbonaceous (CV) chondrite. RBT 04133 shows no evidence for aqueous alteration. However, it is mildly thermally altered (up to approximately 440 °C); which is apparent in its whole-rock C and N isotopic compositions, the degree of disorder of C in insoluble organic matter, low presolar grain abundances, minor element compositions of Fe,Ni metal, chromite compositions and morphologies, and the presence of unequilibrated silicates. Sulfides within type I chondrules from RBT 04133 appear to be pre-accretionary (i.e., did not form via aqueous alteration), providing further evidence that some sulfide minerals formed prior to accretion of the CV chondrite parent body. The thin section studied contains two reduced CV3 lithologies, one of which appears to be more thermally metamorphosed, indicating that RBT 04133, like several other CV chondrites, is a breccia and thus experienced impact processing. Linear foliation of chondrules was not observed implying that RBT 04133 did not experience high velocity impacts that could lead to extensive thermal metamorphism. Presolar silicates are still present in RBT 04133, although presolar SiC grain abundances are very low, indicating that the progressive destruction or modification of presolar SiC grains begins before presolar silicate grains are completely unidentifiable. PMID:26640360

  2. Celebrating the Ordinary

    ERIC Educational Resources Information Center

    Horst, Carol

    2010-01-01

    Memento. Memoir. Memorable. Memory. Memorial. Commemorate. In Memoriam. These words may remind a person of stone monuments, or larger-than-life heroes and loved ones far distanced by space and time. The act of remembering, though, also belongs in the world of the everyday and the ordinary, and has a valuable place in an art classroom. In this…

  3. Sculptures of Ordinary People.

    ERIC Educational Resources Information Center

    Hubbard, Guy

    2000-01-01

    Discusses the presence of ordinary people in art. Features four sculptors and examples of their work: (1) "Janitor" by Duane Hanson; (2) "The Red Light" by George Segal; (3) "The Sodbuster" by Luis A. Jimenez; and (4) "The Driller" by Mahonri Young. (CMK)

  4. Carbonates in the Kaidun chondrite. [Abstract only

    NASA Technical Reports Server (NTRS)

    Weisberg, M. K.; Prinz, M.; Zolensky, M. E.; Ivanov, A. V.

    1994-01-01

    Kaidun is a remarkable chondrite breccia fall containing lithic clasts that span a wide range of chondrite groups including C and E chondrites, as well as having clasts with characteristics not yet found in existing chondrite samples. The dominant lithology in Kaidun appears to be CR chondritic, consonant with recent O isotope data. The carbonates in Kaidun are presented as one mineralogical basis for comparing it to the other hydrated chondrites and to better understand its relative alteration history. The four polished thin sections of Kaidun studied contained a variety of lithologies that we classified into four groups -- CR, E, CM-like, and dark inclusions (DIs). DIs contain sulfide and magnetite morphologies that superficially resemble CI chondrites, and some of the previously reported CI lithologies in Kaidun may be what we term DIs. Carbonates were found in all lithologies studied. Carbonates in Kaidun are similar in composition to those in CR chondrites. Some of the DIs in Kaidun, previously characterized as CI, have carbonates similar to those in CR chondrites and are unlike those in CI or CM chondrites. Most carbonates in Kaidun and CR chondrites are calcites, some of which formed at temperatures above 250 C. Dolomite is less common and some may be metastable. Alteration temperatures in the Renazzo CR chondrite were estimated to be approximately 300 C, based on O isotope fractionation between phyllosilicates and magnetite. Temperatures of up to 450 C were proposed for the alteration of a CR-like dark inclusion in Kaidun, based on the presence of hydrothermal pentlandite veins. The alteration temperatures for Kaidun and the other CR chondrites are considerably higher than those suggested for CI or CM parent bodies.

  5. Formation timescales of CV chondrites from component specific Hf-W systematics

    NASA Astrophysics Data System (ADS)

    Becker, Maike; Hezel, Dominik C.; Schulz, Toni; Elfers, Bo-Magnus; Münker, Carsten

    2015-12-01

    Carbonaceous chondrites are an important meteorite group that closely resembles the bulk composition of the solar system. We report the first elemental and isotope dataset for Hf-W in carbonaceous chondrites that includes chondrules, matrix, magnetic fractions as well as bulk compositions. Our study focuses on the three CV3 chondrites, Allende, Vigarano and Bali. Compared to bulk chondrites, matrix splits have low Hf/W ratios and ?182W compositions, whereas chondrule splits are characterized by high, but more variable, Hf/W ratios and ?182W compositions. Thus, Hf/W ratios behave complementary between chondrules and matrix in the analysed CV chondrites, supporting the view that both components formed from the same parental reservoir. Strong nucleosynthetic effects were observed in most of the analysed CV3 components, especially in matrices and chondrule splits that were found to have large ?183W anomalies of several ?-units. All separates define a rough correlation between initial 182W/184W and 183W/184W ratios, in agreement with theoretical model trends based on calculations for stellar nucleosynthesis. Our results, therefore, indicate a heterogeneous distribution of s- and r-process W isotopes among the different CV3 chondrite components, arguing for selective thermal processing of early solar system matter during chondrule formation. After correcting for nucleosynthetic anomalies, chondrules and matrix splits of reduced (Vigarano) as well as oxidised (Allende) CV3 chondrites define a linear correlation in ?182W vs. 180Hf/184W space, which is interpreted as an isochron, covering an age interval within the first ?2.6 Ma after solar system formation. As peak metamorphic temperatures for CV3 chondrites were well below the 182Hf-182W closure temperature, the resulting isochron within its error most likely defines a common formation interval for all components. The calculated age interval is for the first time based on a combined chondrule-matrix isochron, a marked difference compared to previous studies where only chondrules were analysed. Notably, our formation age interval covers previously reported chondrule formation ages determined using 26Al and Pb-Pb chronometry, illustrating that chondrule and matrix formation started contemporaneously with CAI formation and lasted over a time interval of about 2-3 Ma. Our results also corroborate previous models from ordinary chondrites, in that chondrite parent bodies were not the first planetesimals to have formed in the early solar system.

  6. The Steingarden Nunataks L6 Chondrites STG 07002, 07003, 07004: Relationship to Type 7 Chondrites

    NASA Astrophysics Data System (ADS)

    Brandstätter, F.; Koeberl, C.; Topa, D.

    2014-09-01

    Steingarden Nunataks L6 chondrites STG 07002, 07003 and 07004 have several features in common with some recently described L7 chondrites. The similarities comprise microscopic textures as well as the mineral chemistry of major silicates and opaques.

  7. Rare-earth abundances in chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Evensen, N. M.; Hamilton, P. J.; Onions, R. K.

    1978-01-01

    Fifteen chondrites, including eight carbonaceous chondrites, were analyzed for rare earth element abundances by isotope dilution. Examination of REE for a large number of individual chondrites shows that only a small proportion of the analyses have flat unfractionated REE patterns within experimental error. While some of the remaining analyses are consistent with magmatic fractionation, many patterns, in particular those with positive Ce anomalies, can not be explained by known magmatic processes. Elemental abundance anomalies are found in all major chondrite classes. The persistence of anomalies in chondritic materials relatively removed from direct condensational processes implies that anomalous components are resistant to equilibrium or were introduced at a late stage of chondrite formation. Large-scale segregation of gas and condensate is implied, and bulk variations in REE abundances between planetary bodies is possible.

  8. To Be an Ordinary Department

    ERIC Educational Resources Information Center

    Colburn, Forrest D.

    2003-01-01

    In this article, the author shares his experience being the "chair" of the Department of Latin American and Puerto Rican Studies at Lehman College of the City University of New York. He also shares how this department proved to be an "ordinary" department at an "ordinary" liberal arts college. However, to conclude that they are an ordinary

  9. New component of the Mezo-Madaras breccia - a microchondrule- and carbon-bearing L-related chondrite

    SciTech Connect

    Michel-Levy, M.C.

    1988-03-01

    Microchondrules with apparent diameters 2-150 microns are found in a black carbon-bearing inclusion in Mazo-Madaras. Some are homogeneous (glassy or microcrystalline); others show two phases (mainly silica and pyroxene-rich glass). The bulk chemical composition of the inclusion is related to the host chondrite, in which silica-pyroxene chondrules are ubiquitous. Small black lumps of the same kind are dispersed in bulk Mezo-madaras. This L-related carbon-bearing material may represent a new specimen of C-rich ordinary chondrite. 13 references.

  10. A new component of the Mezo-Madaras breccia - A microchondrule- and carbon-bearing L-related chondrite

    NASA Astrophysics Data System (ADS)

    Michel-Levy, M. C.

    1988-03-01

    Microchondrules with apparent diameters 2-150 microns are found in a black carbon-bearing inclusion in Mazo-Madaras. Some are homogeneous (glassy or microcrystalline); others show two phases (mainly silica and pyroxene-rich glass). The bulk chemical composition of the inclusion is related to the host chondrite, in which silica-pyroxene chondrules are ubiquitous. Small black lumps of the same kind are dispersed in bulk Mezo-madaras. This L-related carbon-bearing material may represent a new specimen of C-rich ordinary chondrite.

  11. The extent of aqueous alteration in C-class asteroids, and the survival of presolar isotopic signatures in chondrites

    NASA Astrophysics Data System (ADS)

    Trigo-Rodriguez, J. M.

    2011-05-01

    Several sample return missions are being planned by different space agencies for in situ sampling of undifferentiated bodies. Such missions wish to bring back to Earth pristine samples from C-class asteroids and comets to obtain clues on solar system formation conditions. A careful selection of targeted areas is required as many C-class asteroids and periodic comets have been subjected to collisional and space weathering processing since their formation. Their surfaces have been reworked by impacts as pointed out by the brecciated nature of many chondrites arrived to Earth, exhibiting different levels of thermal and aqueous alteration. It is not surprising that pristine chondrites can be considered quite rare in meteorite collections because they were naturally sampled in collisions, but several groups of carbonaceous chondrites contain a few members with promising unaltered properties. The CI and CM groups suffered extensive aqueous alteration [1], but for the most part escaped thermal metamorphism (only a few CMs evidence heating temperature over several hundred K). Both chondrite groups are water-rich, containing secondary minerals as consequence of the pervasive alteration of their primary mineral phases [2]. CO, CV, and CR chondrite groups suffered much less severe aqueous alteration, but some CRs are moderately aqueously altered. All five groups are good candidates to find unequilibrated materials between samples unaffected by aqueous alteration or metamorphism. The water was incorporated during accretion, and was released as consequence of shock after impact compaction, and/or by mild radiogenic heating. Primary minerals were transformed by water into secondary ones. Water soaking the bodies participated in chemical homogenization of the different components [1]. Hydrothermal alteration and collisional metamorphism changed the abundances of isotopically distinguishable presolar silicates [3]. Additional instruments in the landers to identify aqueous alteration signatures could help to get samples unbiased by parent body processes. Future work in this regard could be essential to successfully getting back to Earth samples to unveil the conditions in which the solar system formed. REF: [1] Trigo-Rodriguez J.M. & Blum J. 2009. Plan. Space Sci.57,243; [2] Rubin et al. (2007) GCA 71,2361; [3] Trigo-Rodriguez J.M. & Blum J. (2009). Pub.Ast.Soc.Aust.26,289

  12. Formation and transformations of Fe-rich serpentines by asteroidal aqueous alteration processes: A nanoscale study of the Murray chondrite

    NASA Astrophysics Data System (ADS)

    Elmaleh, Agnès; Bourdelle, Franck; Caste, Florent; Benzerara, Karim; Leroux, Hugues; Devouard, Bertrand

    2015-06-01

    Fe-rich serpentines are an abundant product of the early aqueous alteration events that affected the parent bodies of CM carbonaceous chondrites. Alteration assemblages in these meteorites show a large chemical variability and although water-rock interactions occurred under anoxic conditions, serpentines contain high amounts of ferric iron. To date very few studies have documented Fe valence variations in alteration assemblages of carbonaceous chondrites, limiting the understanding of the oxidation mechanisms. Here, we report results from a nanoscale study of a calcium-aluminum-rich inclusion (CAI) from the Murray chondrite, in which alteration resulted in Fe import and Ca export by the fluid phase and in massive Fe-rich serpentines formation. We combined scanning and transmission electron microscopies and scanning transmission X-ray microscopy for characterizing the crystal chemistry of Fe-serpentines. We used reference minerals with known crystallographic orientations to quantify the Fe valence state in Fe-rich serpentines using X-ray absorption spectroscopy at the Fe L2,3-edges, yielding a robust methodology that would prove valuable for studying oxidation processes in other terrestrial or extra-terrestrial cases of serpentinization. We suggest that aqueous Fe2+ was transported to the initially Fe-depleted CAI, where local changes in pH conditions, and possibly mineral catalysis by spinel promoted the partial oxidation of Fe2+ into Fe3+ by water and the formation of Fe-rich serpentines close to the cronstedtite endmember. Such mechanisms produce H2, which opens interesting perspectives as hydrogen may have reacted with carbon species, or escaped and yield increasingly oxidizing conditions in the parent asteroid. From the results of this nanoscale study, we also propose transformations of the initial cronstedtite, destabilized by later input of Al- and Mg-rich solutions, leading to Fe2+ leaching from serpentines, as well as to random serpentine-chlorite interstratifications. Such transformations towards polysomatic assemblages that are un-equilibrated from the structural, chemical and redox point of views are probably controlled by the various rates of alteration of primary minerals, but also by porosity gradients, as in terrestrial hydrothermal systems. We suggest that the proposed mechanisms may have played a role in the early formation of (Fe2+,Fe3+)-rich serpentines documented in CM chondrites, as well as in their transformation with on-going alteration towards Fe-poorer compositions inferred from previous petrologic, mineralogical and magnetic studies of CM chondrites.

  13. 2D Size Distribution of Chondrules and Chondritic Fragments of an Ordinary Chondrite from Lut Desert (Iran)

    NASA Astrophysics Data System (ADS)

    Pourkhorsandi, H.; Mirnejad, H.

    2014-09-01

    2D size measurement of chondrules and chondiritic fragments of a meteorite from Lut desert of Iran is conducted. Chondrules exhibit a size range of 55-1800 µm (average 437 µm). Chondiritic fragments show a size range of 46-1220 µm (average 261 µm).

  14. Chemical and physical studies of type 3 chondrites. I - Metamorphism related studies of Antarctic and other type 3 ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Sears, D. W.; Grossman, J. N.; Melcher, C. L.

    1982-01-01

    New thermoluminescence (TL) sensitivity measurements on 17 finds and one fall are presented, and petrologic assignments are made on the basis of TL sensitivity and silicate heterogeneity. The correlation that exists between TL sensitivity and glow curve shape is discussed, with the difference in the glow curve shapes of meteorite types 3.4 and less and type 3.5 and greater being tentatively attributed to an order-disorder transition in plagioclase, the TL phosphor. A correlation between TL sensitivity and heteogeneity of the silicate composition is found, but it tends to break down in the most heterogeneous meteorites. For Antarctic meteorites, the TL data show a much more restricted range in TL sensitivity than in silicate heterogeneity. The Quinyambie meteorite is the only one not consistent with the observed trend. Several explanations are offered, none of them totally satisfactory.

  15. A refractory inclusion in the Kaba CV3 chondrite - Some implications for the origin of spinel-rich objects in chondrites

    NASA Technical Reports Server (NTRS)

    Fegley, B., Jr.; Post, J. E.

    1985-01-01

    The first detailed petrographic and mineralogical study of a Ca, Al-rich inclusion (CAI) from the Kaba CV3 chondrite is reported. This 'fine-grained' CAI contains abundant small, rounded, rimmed, spinel-rich objects which have important features in common with the spinel-rich objects in other carbonaceous and ordinary chondrites. These nodules are interpreted as fractionated distillation residues of primitive dust. However, the available data do not unambiguously rule out a condensation origin for at least some of these objects. Finally, the preservation of distinct diopside-hedenbergite rims on the spinel-rich bodies and the small grain size of many minerals in the CAI matrix material both suggest that the CAI accreted cool and had a relatively cool thermal history in the Kaba parent body.

  16. Micro-Scale Distributions of Major and Trace Elements in Chondrites

    NASA Technical Reports Server (NTRS)

    Ireland, T. R.; Zolensky, M.

    2011-01-01

    The Hayabusa spacecraft has successfully returned to Earth after two touchdowns on the surface of Asteroid 25143 Itokawa. This asteroid is classified as an S-type and inferred to consist of materials similar to ordinary chondrites or primitive achondrites [1]. More than 1500 particles have been identified consisting of olivine, pyroxene, plagioclase, Fe sulfide and Fe metal, with compositions consistent with being of LL origin. While the chondritic components are familiar to us, the level of detail to which the Itokawa samples will be exposed to will be unprecedented given that the samples are reasonably large and accessible to a wide variety of techniques. In many ways, we expect that our knowledge base of the comparator chondrites will be found to be wanting. Chondrites are the building blocks of the solar system. However, these rocks are essentially breccias and they are quite variable in bulk element compositions as well as compositions of the individual components. We have initiated a program of analysis for chondrites focusing on major and trace element distributions between the mineral components and the matrix. The issues to be addressed include the homogeneity of matrix and chondrule components and the representivity of any given sample to the bulk meteorite. This may be particularly important given the limited numbers of Itokawa grains that may be available for a specific analysis. As an initial study, we have taken thin sections of carbonaceous chondrites to study the representivity of the matrix compositions. Spot locations were constrained to limited regions of the sections so as to assess the variability of a local scale. Further work will be required to assess variability over a centimeter scale.

  17. 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].

  18. Volatile elements in chondrites - Metamorphism or nebular fractionation

    NASA Technical Reports Server (NTRS)

    Takahashi, H.; Gros, J.; Higuchi, H.; Morgan, J. W.; Anders, E.

    1978-01-01

    Three of the most highly metamorphosed meteorites of their respective classes, Shaw (LL7), Karoonda (C5), and Coolidge (C4), were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Comparison with data by Lipschutz and coworkers (1977) on artificially heated primitive meteorites shows that the natural metamorphism of meteorites cannot have taken place in a system open to volatiles. Shaw, metamorphosed at 1300 C for more than 1 million yr, is less depleted in In, Bi, Ag, Te, Zn, and Tl than Krymka heated at 1000 C for 1 week. Karoonda, metamorphosed at 600 C for many millennia, is less depleted in Bi and Tl than Allende heated at 600 C for 1 week. Data on primordial noble gases also show that the volatile-element patterns of ordinary and carbonaceous chondrites were established by nebular condensation and changed little, if at all, during metamorphism. For enstatite chondrites, the evidence is still incomplete but seems to favor a nebular origin of the volatile pattern.

  19. A large shock vein in L chondrite Roosevelt County 106: Evidence for a long-duration shock pulse on the L chondrite parent body

    NASA Astrophysics Data System (ADS)

    Sharp, Thomas G.; Xie, Zhidong; de Carli, Paul S.; Hu, Jinping

    2015-11-01

    A large shock-induced melt vein in L6 ordinary chondrite Roosevelt County 106 contains abundant high-pressure minerals, including olivine, enstatite, and plagioclase fragments that have been transformed to polycrystalline ringwoodite, majorite, lingunite, and jadeite. The host chondrite at the melt-vein margins contains olivines that are partially transformed to ringwoodite. The quenched silicate melt in the shock veins consists of majoritic garnets, up to 25 ?m in size, magnetite, maghemite, and phyllosilicates. The magnetite, maghemite, and phyllosilicates are the terrestrial alteration products of magnesiowüstite and quenched glass. This assemblage indicates crystallization of the silicate melt at approximately 20-25 GPa and 2000 °C. Coarse majorite garnets in the centers of shock veins grade into increasingly finer grained dendritic garnets toward the vein margins, indicating increasing quench rates toward the margins as a result of thermal conduction to the surrounding chondrite host. Nanocrystalline boundary zones, that contain wadsleyite, ringwoodite, majorite, and magnesiowüstite, occur along shock-vein margins. These zones represent rapid quench of a boundary melt that contains less metal-sulfide than the bulk shock vein. One-dimensional finite element heat-flow calculations were performed to estimate a quench time of 750-1900 ms for a 1.6-mm thick shock vein. Because the vein crystallized as a single high-pressure assemblage, the shock pulse duration was at least as long as the quench time and therefore the sample remained at 20-25 GPa for at least 750 ms. This relatively long shock pulse, combined with a modest shock pressure, implies that this sample came from deep in the L chondrite parent body during a collision with a large impacting body, such as the impact event that disrupted the L chondrite parent body 470 Myr ago.

  20. What Are Space Exposure Histories Telling Us about CM Carbonaceous Chondrites?

    NASA Technical Reports Server (NTRS)

    Takenouchi, A.; Zolensky, Michael E.; Nishiizumi, K.; Caffee, M.; Velbel, M. A.; Ross, K.; Zolensky, P.; Le, L.; Imae, N.; Yamaguchi, A.; Mikouchi, T.

    2013-01-01

    Chondrites are chemically primitive and carbonaceous (C) chondrites are potentially the most primitive among them because they mostly escaped thermal metamor-phism that affected the other chondrite groups and ratios of their major, non-volatile and most of the volatile elements are similar to those of the Sun. Therefore, C chondrites are ex-pected to retain a good record of the origin and early history of the solar system. Carbonaceous chondrites are chemically differentiated from other chondrites by their high Mg/Si ratios and refractory elements, and have experienced various degrees of aqueous alteration. They are subdivided into eight subgroups (CI, CM, CO, CV, CK, CR, CB and CH) based on major element and oxygen isotopic ratios. Their elemental ratios spread over a wide range though those of ordinary and enstatite chondrites are relatively uniform. It is critical to know how many sepa-rate bodies are represented by the C chondrites. In this study, CM chondrites, the most abundant carbona-ceous chondrites, are examined. They are water-rich, chon-drule- and CAI-bearing meteorites and most of them are brec-cias. High-temperature components such as chondrules, iso-lated olivine and CAIs in CMs are frequently altered and some of them are replaced by clay minerals and surrounded by sul-fides whose Fe was derived from mafic silicates. On the basis of degrees of aqueous alteration, CMs have been classified into subtypes from 1 to 2, although Rubin et al. [1] assigned subtype 1 to subtype 2 and subtype 2 to subtype 2.6 using various petrologic properties. The classification is based on petrographic and mineralogic properties. For example, though tochilinite (2[(Fe, Mg, Cu, Ni[])S] 1.57-1.85 [(Mg, Fe, Ni, Al, Ca)(HH)2]) clumps are produced during aqueous alteration, they disappear and sulfide appears with increasing degrees of aqueous alteration. Cosmic-ray exposure (CRE) age measurements of CM chondrites reveal an unusual feature. Though CRE ages of other chondrite groups range from several Myr to tens of Myr, CMs exposure ages are not longer than 7 Myr with one-third of the CM having less than 1 Myr CRE age. For those CM chondrites that have CRE ages <1 Myr, there are two discern-able CRE peaks. Because a CRE age reflects how long a me-teorite is present as a separate body in space, the peaks pre-sumably represent collisional events on the parent body (ies) [2]. In this study we defined 4 distinct CRE age groups of CMs and systematically characterized the petrography in each of the 4 CRE age groups to determine whether the groups have significant petrographic differences, with such differences probably reflecting different parent body (asteroid) geological processing, or multiple original bodies.

  1. Origin and history of chondrite regolith, fragmental and impact-melt breccias from Spain

    NASA Technical Reports Server (NTRS)

    Casanova, I.; Keil, K.; Wieler, R.; San Miguel, A.; King, E. A.

    1990-01-01

    Six ordinary chondrite breccias from the Museo Nacional de Ciencias Naturales, Madrid (Spain), are described and classified as follows: the solar gas-rich regolith breccia Oviedo (H5); the premetamorphic fragmental breccias Cabezo de Mayo (type 6, L-LL), and Sevilla (LL4); the fragmental breccias Canellas (H4) and Gerona (H5); and the impact melt breccia, Madrid (L6). It is confirmed that chondrites with typical light-dark structures and petrographic properties typical of regolith breccias may (Oviedo) or may not (Canellas) be solar gas-rich. Cabezo de Mayo and Sevilla show convincing evidence that they were assembled prior to peak metamorphism and were equilibrated during subsequent reheating. Compositions of olivine and low-Ca pyroxene in host chondrite and breccia clasts in Cabezo de Mayo are transitional between groups L and LL. It is suggested, based on mineralogic and oxygen isotopic compositions of host and clasts, that the rock formed on the L parent body by mixing, prior to peak metamorphism. This was followed by partial equilibrium of two different materials: the indigenous L chondrite host and exotic LL melt rock clasts.

  2. Evidence for a source of H chondrites in the outer main asteroid belt

    NASA Astrophysics Data System (ADS)

    Nedelcu, D. A.; Birlan, M.; Popescu, M.; B?descu, O.; Pricopi, D.

    2014-07-01

    Aims: In this paper we report near-infrared spectroscopic observations of one of the largest potentially hazardous asteroids, (214869) 2007 PA8. Mineralogical analysis of this object was followed by the investigation of the dynamical delivery mechanism from its probable source region, based on long-term numerical integrations. Methods: The spectrum of (214869) 2007 PA8 was analysed using the positions of 1 ?m and 2 ?m bands and by curve-matching with RELAB meteorites spectra. Its dynamical evolution was investigated by means of a 200 000-year numerical integration in the past of 1275 clones followed to the source region. Results: (214869) 2007 PA8 has a very young surface with a composition more akin to H chondrites than to any other type of ordinary chondrite. It arrived from the outer Main Belt in the near-Earth space via the 5:2 mean motion resonance with Jupiter by eccentricity pumping. Identification of its source region far from (6) Hebe raises the possibility of the existence of a second parent body of the H chondrites that has a radically different post-accretion history. Future spectroscopic surveys in the 5:2 resonance region will most likely discover other asteroids with an H chondrite composition. Figure 2 is available in electronic form at http://www.aanda.org

  3. H/L chondrite LaPaz Icefield 031047 ? A feather of Icarus?

    SciTech Connect

    Wittmann, Axel; Friedrich, Jon M.; Troiano, Julianne; Macke, Robert J.; Britt, Daniel T.; Swidle, Timothy D.; Weirich, John R.; Rumble III, Douglas; Lasue, Jeremie; King, David A.

    2011-10-28

    Antarctic meteorite LAP 031047 is an ordinary chondrite composed of loosely consolidated chondritic fragments. Its petrography, oxygen isotopic composition and geochemical inventory are ambiguous and indicate an intermediate character between H and L chondrites. Petrographic indicators suggest LAP 031047 suffered a shock metamorphic overprint below {approx}10 GPa, which did not destroy its unusually high porosity of {approx}27 vol%. Metallographic textures in LAP 031047 indicate heating above {approx}700 C and subsequent cooling, which caused massive transformation of taenite to kamacite. The depletion of thermally labile trace elements, the crystallization of chondritic glass to microcrystalline plagioclase of unusual composition, and the occurrence of coarsely crystallized chondrule fragments is further evidence for post-metamorphic heating to {approx}700-750 C. However, this heating event had a transient character because olivine and low-Ca pyroxene did not equilibrate. Nearly complete degassing up to very high temperatures is indicated by the thorough resetting of LAP 031047's Ar-Ar reservoir {approx}100 {+-} 55 Ma ago. A noble gas cosmic-ray exposure age indicates it was reduced to a meter-size fragment at < 0.5 Ma. In light of the fact that shock heating cannot account for the thermal history of LAP 031047 in its entirety, we test the hypothesis that this meteorite belonged to the near-surface of an Aten or Apollo asteroid that underwent heating during orbital passages close to the Sun.

  4. Porosity and Permeability of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Corrigan, Catherine M.; Dahl, Jason; Long, Michael

    1996-01-01

    We have investigated the porosity of a large number of chondritic interplanetary dust particles and meteorites by three techniques: standard liquid/gas flow techniques, a new, non-invasive ultrasonic technique, and image processing of backscattered images . The latter technique is obviously best suited to sub-kg sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, non-destructive pressure release technique. We find that chondritic IDP's have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. These values suggest IDP bulk densities of 1.1 to 3.3 g/cc. Type 1-3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1-3 chondrites have the same approximate range as exhibited by matrix, indicating that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as matrix. These results reveal that the porosity of primitive materials at scales ranging from nanogram to kilogram are similar, implying similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, or chondrite type.

  5. Carbonaceous chondrite clasts in the Kapoeta howardite

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.; Papike, J. J.

    1993-01-01

    A petrographic and mineralogical study of a number of carbonaceous chondrite clasts in the Kapoeta howardite has been carried out. Most of the clasts have mineralogical and chemical properties which link them to the CM carbonaceous chondrites. Some clasts contain chondrules which often have well-developed fine-grained rims, but many have been extensively brecciated. PCP-rich objects are common and pentlandite and pyrrhotite also occur. Calcite has also been found. The remainder of the clasts are extremely fine-grained and appear to be closely related to CI carbonaceous chondrites. In these clasts magnetite framboids are common and finegrained sulfides and magnetite occur disseminated throughout the matrix.

  6. Thermal metamorphism. [of chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Sears, Derek W. G.; Dodd, Robert T.

    1988-01-01

    Most chondrites have experienced thermal metamorphism, resulting in changes in texture, mineralogy and possibly chemical composition. The physical conditions for metamorphism range from approximately 400 to 1000 C at low lithostatic pressure. Metamorphism may have resulted from decay of short-lived radionuclides, electromagnetic induction or accretion of hot materials. Several thermal models for chondrite parent bodies have been proposed. The least metamorphosed type-3 chondrites probably carry the most information about the early solar system, but even these have been affected to some degree by thermal processing.

  7. Ion Irradiation Experiments on the Murchison CM2 Carbonaceous Chondrite: Simulating Space Weathering of Primitive Asteroids

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Christoffersen, R.; Dukes, C. A.; Baragiola, R. A.; Rahman, Z.

    2015-01-01

    Remote sensing observations show that space weathering processes affect all airless bodies in the Solar System to some degree. Sample analyses and lab experiments provide insights into the chemical, spectroscopic and mineralogic effects of space weathering and aid in the interpretation of remote- sensing data. For example, analyses of particles returned from the S-type asteroid Itokawa by the Hayabusa mission revealed that space-weathering on that body was dominated by interactions with the solar wind acting on LL ordinary chondrite-like materials [1, 2]. Understanding and predicting how the surface regoliths of primitive carbonaceous asteroids respond to space weathering processes is important for future sample return missions (Hayabusa 2 and OSIRIS-REx) that are targeting objects of this type. Here, we report the results of our preliminary ion irradiation experiments on a hydrated carbonaceous chondrite with emphasis on microstructural and infrared spectral changes.

  8. The origin and evolution of chondrites recorded in the elemental and isotopic compositions of their macromolecular organic matter

    NASA Astrophysics Data System (ADS)

    Alexander, C. M. O.'D.; Fogel, M.; Yabuta, H.; Cody, G. D.

    2007-09-01

    Extraterrestrial organic matter in meteorites potentially retains a unique record of synthesis and chemical/thermal modification by parent body, nebular and even presolar processes. In a survey of the elemental and isotopic compositions of insoluble organic matter (IOM) from 75 carbonaceous, ordinary and enstatite chondrites, we find dramatic variations within and between chondrite classes. There is no evidence that these variations correlate with the time and/or location of chondrite formation, or with any primary petrologic or bulk compositional features that are associated with nebular processes (e.g., chondrule and volatile trace element abundances). Nor is there evidence for the formation of the IOM by Fischer-Tropsch-Type synthesis in the nebula or in the parent bodies. The elemental variations are consistent with thermal maturation and/or oxidation of a common precursor. For reasons that are unclear, there are large variations in isotopic composition within and between chondrite classes that do not correlate in a simple way with elemental composition or petrologic type. Nevertheless, because of the pattern of elemental variations with petrologic type and the lack of any correlation with the primary features of the chondrite classes, at present the most likely explanation is that all IOM compositional variations are the result of parent body processing of a common precursor. If correct, the range of isotopic compositions within and between chondrite classes implies that the IOM is composed of several isotopically distinct components whose relative stability varied with parent body conditions. The most primitive IOM is found in the CR chondrites and Bells (CM2). Isotopically, the IOM from these meteorites resembles the IOM in interplanetary dust particles. Chemically, their IOM resembles the CHON particles of comet Halley. Despite the large isotopic anomalies in the IOM from these meteorites, it is uncertain whether the IOM formed in the interstellar medium or the outer Solar System, although the former is preferred here.

  9. Carbonaceous Chondrite Clasts in HED Achondrites

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E.; Weisberg, M. K.; Buchanan, P. C.; Mittlefehldt, David W.

    1996-01-01

    Since carbonaceous chondrite planetesimals are attractive candidates for the progenitors of HED asteroid(s), we have performed a survey of HED meteorites in order to locate and characterize the mineralogy, chemistry, and petrography of the oft-reported carbonaceous chondrite clasts by microprobe, SEM-EDX. and TEM techniques. We examined samples of all HEDs we could lay our gloved hands on, and found carbonaceous chondrite clasts in the howardites Kapoeta, Jodzie, EET 87513, Y 793497, LEW 85441, LEW 87015, and G'Day, the polymict eucrites LEW 97295 and LEW 95300, and the diogenite Ellemeet. We verified previous suggestions that the majority (about 80%) of these clasts are CM2 material, but we discovered that a significant proportion are CR2 (about 20%) and other rare types are present. We conclude that chondritic compounds of mixed CM2 and CR2 materials should be investigated in future geochemical modeling of the origin of the HED asteroid(s).

  10. Luminescence Characterization of Tsarev L5 Chondrite

    NASA Astrophysics Data System (ADS)

    Vokhmintsev, A. S.; Weinstein, I. A.; Grokhovsky, V. I.

    2015-07-01

    This work presents the investigation results of spectral and kinetic properties of Tsarev L5 chondrite using photo- and thermoluminescence techniques. Dose fading estimates for laboratory TL response were fulfilled also.

  11. Saturation magnetization measurements of carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Hyman, M.; Rowe, M. W.

    1986-03-01

    The saturation magnetization of some carbonaceous chondrites was studied using a Faraday balance. The authors present measurements on the magnetite contents of some CM2, CV3 and a CV5 chondrites. The method was also used to measure the content of metallic nickel-iron in Ornans, 3.4±0.3%. Of the CM2 chondrites examined, only Bells, Essebi and Haripura had magnetite contents over about 1% by weight. A number of CV chondrites have magnetite between 2.3 and 13%, with little or no metallic iron. Leoville and Vigarano contain both magnetite and metallic iron, complicating the saturation magnetization results. Arch and Allende have very little metallic iron or magnetite, probably <1% of either.

  12. 84Sr Anomalies in Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Moynier, F.; Day, J. M. D.; Bouvier, A.; Walker, R. J.; Podosek, F. A.

    2011-03-01

    Carbonaceous chondrites are enriched by 50 ppm in 84Sr/86Sr ratio compared to terrestrial samples. These results reflect heterogeneous distribution of the p-process nuclide 84Sr in the early solar system.

  13. Chondritic Earth: comparisons, guidelines and status

    NASA Astrophysics Data System (ADS)

    McDonough, W. F.

    2014-12-01

    The chemical and isotopic composition of the Earth is rationally understood within the context of the chondritic reference frame, without recourse to hidden reservoirs, collision erosion, or strict interpretation of an enstatite chondrite model. Challenges to interpreting the array of recent and disparate chemical and isotopic observations from meteorites need to be understood as rich data harvests that inform us of the compositional heterogeneity in the early solar system. Our ability to resolve small, significant compositional differences between chondrite families provide critical insights into integrated compositional signatures at differing annuli distances from the Sun (i.e., 1-6 AU). Rigorous evaluation of chondritic models for planets requires treatment of both statistical and systematic uncertainties - to date these efforts are uncommonly practiced. Planetary olivine to pyroxene ratio reflects fO2 and temperature potentials in the nebular, given possible ISM compositional conditions; thus this ratio is a non-unique parameter of terrestrial bodies. Consequently the Mg/Si value of a planet (ie., olivine to pyroxene ratio) is a free variable; there is no singular chondritic Mg/Si value. For the Earth, there is an absence of physical and chemical evidence requiring a major element, chemical distinction between the upper and lower mantle, within uncertainties. Early Earth differentiation likely occurred, but there is an absence of chemical and isotopic evidence of its imprint. Chondrites, peridotites, komatiites, and basalts (ancient and modern) reveal a coherent picture of a chondritic compositional Earth, with compositionally affinities to enstatite chondrites. At present results from geoneutrino studies non-uniquely support these conclusions. Future experiments can provide true transformative insights into the Earth's thermal budget, define compositional BSE models, and will restrict discussions on Earth dynamics and its thermal evolution.

  14. Birth in an Ordinary Instant

    PubMed Central

    De Vries, Charlotte

    2010-01-01

    Our daily lives are a series of ordinary moments and unnoticed thresholds—times that define us in ways we often do not give much attention. While we consider childbirth to be one of life's extra-ordinary events, the hours of labor and birth need not be dramatic (or traumatic) ones. I describe a quiet, well-supported birth in the Netherlands that is cause for celebration of the beauty of an ordinary instant that can define and enrich the human experience. PMID:21629383

  15. Chemical and physical studies of type 3 chondrites. VIII - Thermoluminescence and metamorphism in the CO chondrites

    NASA Technical Reports Server (NTRS)

    Keck, Bradly D.; Sears, Derek W. G.

    1987-01-01

    A possible relationship between the thermoluminescence (TL) properties of CO chondrites and their metamorphic history was investigated by measuring the TL properties of seven normal CO chondrites and of the Colony and the Allan Hills A77307 (ALHA 77307) CO-related chondrites. With the exception of Colony and ALHA 77307, whose maximum induced TL emission is at approximately 350 C, the CO chondrites were found to exhibit two TL peaks: a 130 C and a 250 C peaks. Among the CO chondrites, the 130 C peak showed a 100-fold range in TL sensitivity and was found to correlate with various metamorphism-related phenomena, such as silicate heterogeneity, metal composition, and McSween's metamorphic subtypes. The peak at 250 did not show these correlations and, with exception of Colony, showed little variation.

  16. Effects of Microsecond Pulse Laser Irradiation on Vis-NIR Reflectance Spectrum of Carbonaceous Chondrite Simulant: Implications for Martian Moons and Primitive Asteroids

    NASA Technical Reports Server (NTRS)

    Hiroi, T.; Moroz, L. V.; Shingareva, T. V.; Basilevsky, A. T.; Pieters, M.

    2003-01-01

    Goal of this study is to make a progress in understanding the optical effects of space weathering on small bodies believed to be similar in composition to carbonaceous chondrites: C, G, B, F, T, D, and P asteroids and possibly Martian satellites Phobos and Deimos. The companion work focuses on petrological and mineralogical aspects of this process. One of the main factors of space weathering is meteorite and micrometeorite bombardment leading, in particular, to impact melting of components of the regolith. Studies of lunar regolith and laboratory experiments simulating impact melting show that the melting products differ from the unmelted material in mineralogy and distribution of chemical components among different phases that results in spectral changes. We simulate impact melting of CM chondrite by pulse laser irradiation of an artificial analog of such a meteorite. The analog is a mixture of 46 wt.% non-magnetic fraction of L5 ordinary chondrite Tsarev, 47 wt.% serpentine, 5 wt.% kerite, and 2 wt.% calcite. It simulates rather well bulk chemistry, including volatiles such as H2O and CO2, and only approximately the CM chondrite mineralogy. Thus, we do not expect the mixture to be spectrally similar to CM chondrites, but expect the laser melting products to be similar to those formed by impact melting of natural CM chondrites.

  17. Petrologic evidence for collisional heating of chondritic asteroids

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1995-01-01

    The identification of the mechanism(s) responsible for heating asteroids is among the major problems in planetary science. Because of difficulties with models of electromagnetic induction and the decay of short-lived radionuclides, it is worthwhile to evaluate the evidence for collisional heating. New evidence for localized impact heating comes from the high proportion of relict type-6 material among impact-melt-bearing ordinary chondrites (OC). This relict material was probably metamorphosed by residual heat within large craters. Olivine aggregates composed of faceted crystals with 120 deg triple junctions occur within the melted regions of the Chico and Rose City OC melt rocks; the olivine aggregates formed from shocked, mosaicized olivine grains that underwent contact metamorphism. Large-scale collisional heating is supoorted by the correlation in OC between petrologic type and shock stage; no other heating mechanism can readily account for this correlation. The occurrence of impact-melt-rock clasts in OC that have been metamorphosed along with their whole rocks indicates that some impact events preceded or accompanied thermal metamorphism. Such impacts events, occurring during or shortly after accretion, are probably responsible for substantially melting approximately 0.5% of OC. These events must have heated a larger percentage of OC to subsolidus temperatures sufficient to have caused significant metamorphism. If collisional heating is viable, then OC parent asteroids must have been large; large OC asteroids in the main belt may include those of the S(IV) spectral subtype. Collisional heating is inconsistent with layered ('onion-shell') structures in OC asteroids (wherein the degree of metamorphism increases with depth), but the evidence for such structures is weak. It seems likely that collisional heating played an important role in metamorphosing chondritic asteroids.

  18. Origin of spinel-rich chondrules and inclusions in carbonaceous and ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Kornacki, A. S.; Fegley, B., Jr.

    1984-01-01

    The evaluation of three models of the origin of spinel-rich chondrules 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 chondrules 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 chondrules and inclusions (1) are usually smaller than melilite-rich chondrules 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.

  19. Cosmogenic Records in 18 Ordinary Chondrites from the Dar Al Gani Region, Libya. 1; Noble Gases

    NASA Technical Reports Server (NTRS)

    Schultz, L.; Franke, L.; Welten, K. C.; Nishiizumi, K.; Jull, A. J. T.

    2003-01-01

    In the last decade thousands of meteorites have been recovered from hot deserts in the Sahara and Oman. One of the main meteorite concentration surfaces in the Sahara is the Dar al Gani plateau in Libya, which covers a total area of 8000 km2. More than 1000 meteorites have been reported from this area. The geological setting, meteorite pairings and the meteorite density of the Dar al Gani (DaG) field are described in more detail in [1]. In this work we report concentrations of the noble gas isotopes of He, Ne, Ar as well as 84Kr and 132Xe in 18 DaG meteorites. In a separate paper we will report the cosmogenic radionuclides [2]. We discuss the thermal history and cosmic-ray exposure (CRE) history of these meteorites, and evaluate the effects of the hot desert environment on the noble gas record.

  20. Fusion Crust and the Measurement of Surface Ages of Antarctic Ordinary Chondrites

    NASA Technical Reports Server (NTRS)

    Akridge, Jannette M. C.; Benoit, Paul H.; Sears, Derek W. G.

    1997-01-01

    Natural thermoluminescence (TL) reflects radiation exposure and storage temperature. Meteorites generally exhibit thermoluminescence acquired during their long exposure to galactic cosmic rays in space. During atmospheric passage, temperatures are high enough to completely drain the TL, in the first mm of material under the fusion crust. We therefore refer to this surface layer as "fusion crust" although it does include some unmelted material just below the crust. When the meteorite lands on earth this drained layer will begin to build up natural TL once again due to radiation from cosmic rays and internal radionuclides. Cosmic ray annual dose is estimated to be between 0.04 and 0.06 rad/yr on the earth's surface in Antarctica while the internal radionuclides contribute only about 0.01 rad/yr. Therefore the total annual dose received by the meteorite while it is on the surface is between 0.05 and 0.07 rad/yr. If the meteorite is buried deeply in the ice it is effectively shielded from most cosmic rays and thus only internal radioactivity contributes to the annual dose.

  1. The natural thermoluminescence of meteorites. IV - Ordinary chondrites at the Lewis Cliff ice field

    NASA Technical Reports Server (NTRS)

    Benoit, Paul H.; Sears, Hazel; Sears, Derek W. G.

    1992-01-01

    Results of natural thermoluminescence (TL) measurements of 302 meteorites from the vicinity of the Lewis Cliff in the Beardmore region of Antarctica are presented in order to identify fragments of a single fall and to elucidate ice sheet movements and the mechanisms by which meteorite concentration occurs at this site. From the distribution of meteorites on the ice, the shape of the fields of 'paired' meteorites, and trends in the natural TL data, it is inferred that there is a western component to the movement of the ice at this location, as well as the previously supposed movement to the north. The western vector explains the concentration of meteorites along the western edge of the ice tongue. These new natural TL data identify several recent falls and several meteorites which probably had unusually small perihelia immediately prior to capture by the earth.

  2. Magnetic Evidence for a Partially Differentiated Carbonaceous Chondrite Parent Body

    E-print Network

    Shuster, David L.

    The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. ...

  3. Silicate sulfidation and chemical differences between enstatite chondrites and Earth

    NASA Astrophysics Data System (ADS)

    Lehner, S. W.; Petaev, M. I.; Buseck, P. R.

    2013-12-01

    Isotopic similarity between the Earth-Moon system and enstatite chondrites (ECs) led to the idea that ECs were Earth's building blocks [1-3]. However, compared to Earth's mantle, ECs have low Fe0/Fe ratios, are enriched in volatile elements, and depleted in refractory lithophile elements and Mg [4]. Therefore, deriving Earth composition from ECs requires a loss of volatiles during or prior to accretion and sequestering a large fraction of Si in the deep Earth. Alternatively, the isotopic similarity between the Earth and ECs is explained by their formation from a common precursor that experienced different evolutionary paths resulting in the chemical difference [4]. The vestiges of such a precursor are still present in the unequilibrated ECs as FeO-rich silicates with O isotopic compositions identical to bulk ECs and Earth [5]. Conversion of such a precursor into the characteristic EC mineral assemblage requires high-temperature processing in an H-poor environment with high fS2 and fO2 close to that of the classic solar nebula [6], consistent with redox conditions inferred from Ti4+/Ti3+ ratios in EC pyroxene [7]. Under such conditions reaction of FeO-rich silicates with S-rich gas results in their replacement by the assemblage of FeO-poor silicates; Fe, Mg, Ca sulfides; free silica; and Si-bearing Fe,Ni metal alloy. The progressive sulfidation of ferromagnesian silicates in chondrules results in loss of Mg and addition of Fe, Mn, S, Na, K and, perhaps, other volatiles [6]. At the advanced stages of silicate sulfidation recorded in the metal-sulfide nodules [8], a portion of Si is reduced and dissolved in the Fe,Ni metal. This process is known to fractionate Si isotopes [9,10] and would explain the differences between the ECs and Earth's mantle [11]. The sulfidation of silicates also produces porous S-rich silica, a peculiar phase observed so far only in the ECs. It consists of a sinewy SiO2-rich framework enclosing numerous vesicles filled with beam-sensitive material and contains minor elements such as Na, Ca, Mg, or Fe, which also occur in the adjacent minerals. Its high S content and vesicular nature point to formation by quenching of a high-temperature melt saturated with a gaseous phase. The porous silica occurs in ~50% of chondrules [12], metal-sulfide nodules, and as inter-chondrule clasts, suggesting it is a good tracer of silicate sulfidation. Refs: [1] Javoy M. (1995) GRL 22: 2219-2222. [2] Javoy M. et al. (2010) EPSL 293: 259-268. [3] Kaminski E. & Javoy M. (2013) EPSL 365: 97-107. [4] Jacobsen S.B. et al. (2013) LPSC 44: #2344. [5] Weisberg M.K. et al. (2011) GCA 75: 6556-6569. [6] Lehner S.W. et al. (2013) GCA 101: 34-56. [7] Simon S.B. et al. (2013) LPSC 44: #2270. [8] Lehner S.W. et al. (2012) LPSC 43: #2252. [9] Shahar A. et al. (2011) GCA 75: 7688-7697. [10] Kempl J. et al. (2013) EPSL 368: 61-68. [11] Fitoussi C. & Bourdon B. (2012) Science 335: 1477-1480. [12] Piani L. et al. (2013) MetSoc 76: # 5178.

  4. Exposure ages of carbonaceous chondrites, 1

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.; Arnold, J. R.; Caffee, M. W.; Finkel, R. C.; Southon, J. R.; Nagai, H.; Honda, M.; Sharma, P.; Imamura, M.; Kobayashi, K.

    1993-01-01

    The recent exposure histories of carbonaceous chondrites have been investigated using cosmogenic radionuclides. Our results may indicate a clustering of exposure ages of C1 and C2 chondrites into two peaks, 0.2 My and 0.6 My, perhaps implying two collisional events of Earth-crossing parent bodies. Among carbonaceous chondrites are some having short exposure ages which Mazor et al. hypothesized cluster into a small number of families. This hypothesis is based on spallogenic Ne-21 exposure ages, which in some instances are difficult to determine owing to the large amounts of trapped noble gases in carbonaceous chondrites. Also, since Ne-21 is stable, it integrates a sample's entire exposure history, so meteorites with complex exposure histories are difficult to understand using exclusively Ne-21. Cosmogenic radionuclides provide an alternative means of determining the recent cosmic ray exposure duration. To test the hypothesis of Mazor et al. we have begun a systematic investigation of exposure histories of Antarctic and non-Antarctic carbonaceous chondrites especially C2s.

  5. 146Sm-142Nd systematics measured in enstatite chondrites reveals a heterogeneous distribution of 142Nd in the solar nebula.

    PubMed

    Gannoun, Abdelmouhcine; Boyet, Maud; Rizo, Hanika; El Goresy, Ahmed

    2011-05-10

    The short-lived (146)Sm-(142)Nd chronometer (T(1/2) = 103 Ma) is used to constrain the early silicate evolution of planetary bodies. The composition of bulk terrestrial planets is then considered to be similar to that of primitive chondrites that represent the building blocks of rocky planets. However for many elements chondrites preserve small isotope differences. In this case it is not always clear to what extent these variations reflect the isotope heterogeneity of the protosolar nebula rather than being produced by the decay of parent isotopes. Here we present Sm-Nd isotopes data measured in a comprehensive suite of enstatite chondrites (EC). The EC preserve (142)Nd/(144)Nd ratios that range from those of ordinary chondrites to values similar to terrestrial samples. The EC having terrestrial (142)Nd/(144)Nd ratios are also characterized by small (144)Sm excesses, which is a pure p-process nuclide. The correlation between (144)Sm and (142)Nd for chondrites may indicate a heterogeneous distribution in the solar nebula of p-process matter synthesized in supernovae. However to explain the difference in (142)Nd/(144)Nd ratios, 20% of the p-process contribution to (142)Nd is required, at odds with the value of 4% currently proposed in stellar models. This study highlights the necessity of obtaining high-precision (144)Sm measurements to interpret properly measured (142)Nd signatures. Another explanation could be that the chondrites sample material formed in different pulses of the lifetime of asymptotic giant branch stars. Then the isotope signature measured in SiC presolar would not represent the unique s-process signature of the material present in the solar nebula during accretion. PMID:21515828

  6. 146Sm–142Nd systematics measured in enstatite chondrites reveals a heterogeneous distribution of 142Nd in the solar nebula

    PubMed Central

    Gannoun, Abdelmouhcine; Boyet, Maud; Rizo, Hanika; El Goresy, Ahmed

    2011-01-01

    The short-lived 146Sm–142Nd chronometer (T1/2 = 103 Ma) is used to constrain the early silicate evolution of planetary bodies. The composition of bulk terrestrial planets is then considered to be similar to that of primitive chondrites that represent the building blocks of rocky planets. However for many elements chondrites preserve small isotope differences. In this case it is not always clear to what extent these variations reflect the isotope heterogeneity of the protosolar nebula rather than being produced by the decay of parent isotopes. Here we present Sm–Nd isotopes data measured in a comprehensive suite of enstatite chondrites (EC). The EC preserve 142Nd/144Nd ratios that range from those of ordinary chondrites to values similar to terrestrial samples. The EC having terrestrial 142Nd/144Nd ratios are also characterized by small 144Sm excesses, which is a pure p-process nuclide. The correlation between 144Sm and 142Nd for chondrites may indicate a heterogeneous distribution in the solar nebula of p-process matter synthesized in supernovae. However to explain the difference in 142Nd/144Nd ratios, 20% of the p-process contribution to 142Nd is required, at odds with the value of 4% currently proposed in stellar models. This study highlights the necessity of obtaining high-precision 144Sm measurements to interpret properly measured 142Nd signatures. Another explanation could be that the chondrites sample material formed in different pulses of the lifetime of asymptotic giant branch stars. Then the isotope signature measured in SiC presolar would not represent the unique s-process signature of the material present in the solar nebula during accretion. PMID:21515828

  7. Early Solar System hydrothermal activity in chondritic asteroids on 1–10-year timescales

    PubMed Central

    Dyl, Kathryn A.; Bischoff, Addi; Ziegler, Karen; Young, Edward D.; Wimmer, Karl; Bland, Phil A.

    2012-01-01

    Chondritic meteorites are considered the most primitive remnants of planetesimals from the early Solar System. As undifferentiated objects, they also display widespread evidence of water–rock interaction on the parent body. Understanding this history has implications for the formation of planetary bodies, the delivery of water to the inner Solar System, and the formation of prebiotic molecules. The timescales of water–rock reactions in these early objects, however, are largely unknown. Here, we report evidence for short-lived water–rock reactions in the highly metamorphosed ordinary chondrite breccia Villalbeto de la Peña (L6). An exotic clast (d = 2cm) has coexisting variations in feldspar composition and oxygen isotope ratios that can only result from hydrothermal conditions. The profiles were modeled at T = 800 °C and P(H2O) = 1 bar using modified grain-boundary diffusion parameters for oxygen self-diffusion and reaction rates of NaSiCa-1Al-1 exchange in a fumarole. The geochemical data are consistent with hydrothermal activity on the parent body lasting only 1–10 y. This result has wide-ranging implications for the geological history of chondritic asteroids. PMID:23093668

  8. Workshop on Parent-Body and Nebular Modification of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Krot, A. N. (Editor); Zolensky, M. E. (Editor); Scott, E. R. D. (Editor)

    1997-01-01

    The purpose of the workshop was to advance our understanding of solar nebula and asteroidal processes from studies of modification features in chondrites and interplanetary dust particles. As reflected in the program contained in this volume, the workshop included five regular sessions, a summary session, and a poster session. Twenty-three posters and 42 invited and contributed talks were presented. Part 1 of this report contains the abstracts of these presentations. The focus of the workshop included: (1) mineralogical, petrologic, chemical, and isotopic observations of the alteration mineralogy in interplanetary dust particles, ordinary and carbonaceous chondrites, and their components (Ca-Al-rich inclusions, chondrules, and matrix) to constrain the conditions and place of alteration; (2) sources of water in chondrites; (3) the relationship between aqueous alteration and thermal metamorphism; (4) short-lived radionuclides, AI-26, Mn-53, and I-129, as isotopic constraints on timing of alteration; (5) experimental and theoretical modeling of alteration reactions; and (6) the oxidation state of the solar nebula. There were approximately 140 participants at the workshop, probably due in part to the timeliness of the workshop goals and the workshop location. In the end few new agreements were achieved between warring factions, but new research efforts were forged and areas of fruitful future exploration were highlighted. Judged by these results, the workshop was successful.

  9. Olivine in terminal particles of Stardust aerogel tracks and analogous grains in chondrite matrix

    NASA Astrophysics Data System (ADS)

    Frank, David R.; Zolensky, Michael E.; Le, Loan

    2014-10-01

    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 olivine (Fa0-97) in the coarse-grained terminal particles of Stardust aerogel tracks and a comprehensive dataset (>103 analyses) of analogous olivine grains (5-30 ?m) 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 olivine includes amoeboid olivine aggregates (AOAs), refractory forsterite, type I and type II chondrule 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 olivine in the Stardust samples indicates that they underwent mild thermal metamorphism, akin to a petrologic grade of 3.05-3.15.

  10. Degree of Weathering of H-Chondrites from Frontier Mountain, Antarctica

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Nishiizumi, Kunihiko

    1999-01-01

    One of the factors that determines the survival time of meteorites on the Earth's surface is the rate of weathering. For meteorites from hot deserts, a clear correlation is found between the degree of weathering and the terrestrial age, but for Antarctic meteorites this correlation is weak or even lacking. The lack of a clear correlation can partly be attributed to the two-stage history of many Antarctic meteorites, which spend part of their terrestrial residence time in the ice before they are exposed on the ice. Recently, it was found that for Lewis Cliff (LEW) meteorites local conditions on the ice play an important role in the weathering process. This work focuses on weathering effects in ordinary chondrites from Frontier Mountain (FRO), North Victoria Land. Although most FRO meteorites were classified as weathering category A or B, many are contaminated with terrestrial uranium, deposited from meltwater. This suggests that weathering plays a more significant role than the qualitative A-B-C weathering index indicates. We therefore determined the degree of weathering more quantitatively, by deriving the amount of oxidized metal from the concentrations of Fe and Ni in the nonmagnetic fraction of 23 H-chondrites and 1 L-chondrite. The results will be compared with those of LEW meteorites and will be discussed in terms of terrestrial age and location of find on the ice.

  11. Degree of Weathering of H-Chondrites From Frontier Mountain, Antarctica

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Nishiizumi, K.

    2000-01-01

    One of the factors that determines the survival time of meteorites on the Earth's surface is the rate of weathering. For meteorites from hot deserts, a clear correlation is found between the degree of weathering, and the terrestrial age, but for Antarctic meteorites this correlation is weak or even lacking. The lack of a clear correlation can partly be attributed to the two-stage history of many Antarctic meteorites, which spend part of their terrestrial residence time in the ice before they are exposed on the ice. Recently, it was found that for Lewis Cliff (LEW) meteorites local conditions on the ice play an important role in the weathering process. This work focuses on weathering effects in ordinary chondrites from Frontier Mountain (FRO), North Victoria Land. Although most FRO meteorites were classified as weathering category A or B, many are contaminated with terrestrial uranium, deposited from meltwater. This suggests that weathering plays a more significant role than the qualitative A-B-C weathering index indicates. We therefore determined the degree of weathering more quantitatively, by deriving the amount of oxidized metal from the concentrations of Fe and Ni in the nonmagnetic fraction of 23 H-chondrites and 1 L-chondrite The results will be compared with those of LEW meteorites and will be discussed in terms of terrestrial age and location of find on the ice.

  12. Experimental vaporization of the Holbrook chondrite

    NASA Technical Reports Server (NTRS)

    Gooding, J. L.; Muenow, D. W.

    1977-01-01

    The vapor phase composition obtained by heating samples of the Holbrook L6 chondrite to 1300 C was determined quantitatively by Knudsen cell-quadrupole mass spectrometry. Maximum observed vapor pressures, produced at 1200 C, are reported for Na, K, Fe, and Ni, and the implications of the Na/K ratio are considered. The Fe and Ni data are discussed with attention to their migration in individual equilibrated chondrites. S2 (with minor SO2), H2O, and CO2 were also present in the high-temperature gas phase. Vesicles formed by the release of intrinsically derived volatiles are compared with vesicles in the Ibitira eucrite. Chondrite evolution is briefly discussed.

  13. Extraterrestrial Nucleobases in Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Martins, Z.; Botta, O.; Fogel, M.; Sephton, M.; Glavin, D.; Watson, J.; Dworkin, J.; Schwartz, A.; Ehrenfreund, P.

    Nucleobases in Carbonaceous Chondrites Z. Martins (1), O. Botta (2), M. L. Fogel (3), M. A. Sephton (4), D. P. Glavin (2), J. S. Watson (5), J. P. Dworkin (2), A. W. Schwartz (6) and P. Ehrenfreund (1,6). (1) Astrobiology Laboratory, Leiden Institute of Chemistry, Leiden, The Netherlands, (2) NASA Goddard Space Flight Center, Goddard Center for Astrobiology, Greenbelt, MD, USA, (3) GL, Carnegie Institution of Washington, Washington DC, USA, (4) Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, South Kensington Campus, Imperial College, London, UK, (5) Planetary and Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes, UK, (6) Radboud University Nijmegen, Nijmegen, The Netherlands. E-mail: z.martins@chem.leidenuniv.nl/Phone:+31715274440 Nucleobases are crucial compounds in terrestrial biochemistry, because they are key components of DNA and RNA. Carbonaceous meteorites have been analyzed for nucleobases by different research groups [1-5]. However, significant quantitative and qualitative differences were observed, leading to the controversial about the origin of these nucleobases. In order to establish the origin of these compounds in carbonaceous chondrites and to assess the plausibility of their exogenous delivery to the early Earth, we have performed formic acid extraction of samples of the Murchison meteorite [6], followed by an extensive purification procedure, analysis and quantification by high-performance liquid chromatography with UV absorption detection and gas chromatography-mass spectrometry. Our results were qualitatively consistent with previous results [3, 4], but showed significant quantitative differences. Compound specific carbon isotope values were obtained, using gas chromatography-combustion- isotope ratio mass spectrometry. A soil sample collected in the proximity of the Murchison meteorite fall site was subjected to the same extraction, purification and analysis procedure. Our stable carbon isotope measurements clearly demonstrate that the nucleobases in the Murchison meteorite are indigenous to the meteorite, and clearly differ from the values determined for the terrestrial nucleobases measured in the soil collected at the impact site. These results support the hypothesis that nucleobases were exogenously delivered to the early Earth, and may have been important for the prebiotic chemistry on our young planet. With regard to the detection of traces of life on other planets such as Mars it is essential to characterize organic materials that have been exogenously delivered to the early planets. The analysis of the composition and isotopic fractionation of extraterrestrial material using complementary techniques can provide crucial insights into the formation of our Solar System, extraterrestrial delivery processes and subsequent addition and incorporation into the carbonaceous material available on the young planets. Ultimately, these parameters form an essential reference point for interpreting biosignatures that may be left in the ancient rock record on a planetary body. References: [1] Hayatsu R. et al. 1975. Geochimica et Cosmochimica Acta 39: 471- 488. [2] Folsome C. E. et al. 1971. Nature 232: 108-109. [3] Stoks P. G. & Schwartz A. W. 1979. Nature 282: 709-710. [4] Stoks P.G. & Schwartz A. W. 1981. Geochimica et Cosmochimica Acta 45: 563-569. [5] Shimoyama A. et al. 1990. Geochemical Journal 24: 343-348. [6] Martins Z. et al. 2004. Meteoritics & Planetary Science 39: A5145. 2

  14. EL3 Chondrite (not Aubrite) Northwest Africa 2828: An Unusual Paleo-meteorite Occurring as Cobbles in a Terrestrial Conglomerate

    NASA Astrophysics Data System (ADS)

    Kuehner, S. M.; Irving, A. J.; Bunch, T. E.; Wittke, J. H.

    2006-12-01

    Although we recently classified NWA 2828 as an aubrite [1], our examination of new material (now comprising over 120 stones totaling >27 kg) requires revision of that classification. New information on the find site in Algeria indicates that these stones were excavated from a subsurface deposit, and we have found terrestrial rhyolite pebbles and sandy matrix attached to several NWA 2828 stones (see images at http://www.ess.washington.edu/meteoritics). Thus this is a rare example of a paleo-meteorite or 'fossil' meteorite. Some stones contain sparse (<5 vol.%) but very distinct round, radial pyroxene chondrules (up to 3 mm across), as well as rounded, fine-grained aggregates (up to 6 mm across) rich in either enstatite or sodic plagioclase. Remnant Na-Al-Si-rich glass is present within cavities in chondrules, both between enstatite blades and in annular zones. The matrix contains pervasive 0.2-0.5 mm cavities with coatings of calcite and minor halite and gypsum. Iron sulfate (after troilite), jarosite, an inhomogeneous (possibly amorphous) phase rich in Fe, Cr, Si, Ca, Ti, P, S and Cl, minor native sulfur and silica also are present, and brown Fe-rich rinds on one stone contain up to 6.5 wt.% Ni. These secondary minerals signify terrestrial alteration of primary metal, sulfides, phosphides, nitrides and glass in an ancient fluvial and/or acidic lacustrine environment. The dominant primary phase in NWA 2828 is enstatite (En98.4Wo1.4), which forms stubby prismatic grains (lacking polysynthetic twinning indicative of inverted clinoenstatite [cf., 1]). Our original classification was based on a very small specimen of an apparently igneous-textured rock, but the discovery of chondrules and the absence of twinned enstatite now suggests that it is instead an unequilibrated enstatite chondrite. Additional primary phases noted previously [1] are sodic plagioclase (An14- 15Or3-4), troilite, graphite, daubreelite, alabandite, oldhamite, schreibersite, glass and very rare kamacite. The well-formed, round chondrules containing glass coupled with the unrecrystallized matrix lead us to re-classify NWA 2828 as an EL3 chondrite. We also must revise our opinion [1] about the relationship between NWA 2828 and material classified as EL chondrites NWA 2965 and NWA 2736, which evidently come from the more extensively weathered top of the same ancient conglomerate layer as NWA 2828. [1] Irving A.J. et al. (2006) 69th Met. Soc. Mtg., #5264 (MAPS 41 Suppl., A84)

  15. Ordinary People, Ordinary Places: The Civil Rights Movement. [Lesson Plan].

    ERIC Educational Resources Information Center

    2002

    Martin Luther King, Jr. framed the goals and strategies of the Civil Rights Movement for a national audience, and with his message of nonviolent protest, he inspired ordinary African Americans to demand equal rights as American citizens. This lesson focuses on the individual men and women who embraced King's message and advanced the Civil Rights…

  16. Petrology and Stable Isotopes of LEW 87232, A New Kakangari-type Chondrite

    NASA Astrophysics Data System (ADS)

    Weisberg, M. K.; Prinz, M.; Clayton, R. N.; Mayeda, T. K.; Grady, M. M.; Franchi, I. A.

    1993-07-01

    The discovery of new chondrite groups is an important step in widening our understanding of the primitive asteroidal materials on which models of early solar system processes are based. LEW87232 was tentatively classified as a CR chondrite [1] and our interest in the CR group and its diversity [2] led us to study this meteorite. This petrologic and stable isotope study shows that LEW87232 is, in fact, a new member of the rare Kakangari-type chondrite grouplet. Kakangari was recognized as the first member of a new chondrite group with petrologic, bulk chemical, and oxygen isotopic characteristics that sharply distinguish it from other chondrites [3-7]. Lea Co. 002 was found to be a second member [8]. Texturally, LEW87232 consists of chondrules, fragments, and metal spheres (chondrules) set in a fine-grained matrix. The chondrule mean diameter is 0.4 nm (some up to 1.6 mm). Most chondrules are porphyritic pyroxene, and olivine is poikilitically enclosed in the pyroxene. Rarely, chondrules are olivine rich. Metal chondrules consist of kamacite with exsolved taenite and are rimmed by, and enclose, lath-shaped pyroxene that is similar in size and morphology to the matrix pyroxene; accessory apatite and schreibersite are associated with the metal. The matrix consists mainly of low-Ca-pyroxene laths 1-3 micrometers wide, up to 15 micrometers long, and it is intermixed with an Fe oxide, possibly ferrihydrite. Ferrihydrite was identified in Kakangari [9]. Mineral compositions in chondrules, fragments, and matrix are fairly homogeneous, and similar, with pyroxene Wo0.2-0.5Fs2.6-3.6, olivine Fa0.5-2.9, Ca-pyroxene Wo45Fs0.8, and plagioclase An~60. Kamacite (Ni ~ 5.6%) and taenite (Ni ~ 27%) are homogeneous. Kakangari has similar mineral compositions [7]. Bulk compositions of the chondrules and matrix are strikingly similar, reflecting similarities in their modes and mineral compositions. Stable Isotopes: LEW87232 nitrogen, total delta-15N = +10.6 permil, [N] = 80.6 ppm, is closest to that of ordinary chondrites and differs from that of Kakangari, which has lighter N (total delta-15N = -20 permil). Total [C] = 1989 ppm and is also closest to ordinary chondrites. Kakangari total [C] = 864 [10]. Combustion temperatures indicate the presence of some organic component with delta-15N ~ +4 to +8 permil released at low T. N released above 1000 degrees C may be a combination of spallogenic N, with N possibly from SiC. The oxygen isotope compositions of Kakangari-type chondrites are shown in the figure. Whole rock LEW87232 plots close to the other Kakangari-type chondrites. Chondrule compositions are similar to those in Kakangari, but are displaced toward lower delta-18O values perhaps, in part, due to weathering. Chondrules from Kakangari-type chondrites generally have oxygen compositions similar to enstatite chondrite chondrules (shown by the loop) and some extend toward more 16O-rich compositions. Conclusions: LEW87232 is shown to be a Kakangari-type meteorite and it further defines this distinct chondrite grouplet. Characteristics that distinguish the Kakangari-type grouplet from other chondrite groups include (1) the oxygen isotope composition of the chondrules and matrix, (2) the high metal and pyroxene abundances and low FeO content of the silicates that indicate an oxidation state between H and E chondrites, (3) the Mg- and pyroxene-rich nature and similarity of the chondrules and matrix, (4) the unique intergrowths of matrix pyroxene within and rimming metal chondrules, suggesting that abundant Mg-rich pyroxene crystals formed in the nebula and were present during chondrule formation. References: [1] Mason B. (1992) Ant. Met. News., 15, 24. [2] Weisberg M. K. et al. (1993) GCA, 57, 1567-1586. [3] Graham A. L. and Hutchison R. (1974) Nature, 251, 128-129. [4] Clayton R. N. et al. (1976) LPSC, VII, 160-162. [5] Clayton R. N. et al. (1976) EPSL, 30, 10-18. [6] Davis A. M. et al. (1977) Nature, 265, 230-232. [7] Prinz M. et al. (1989) LPSC, XX, 870-871. [8] Prinz M. et al. (1991) LPSC, XXII, 1097-1098. [9] Brearley A. J. (1989) GCA, 53,

  17. Potentially hazardous Asteroid 2007 LE: Compositional link to the black chondrite Rose City and Asteroid (6) Hebe

    NASA Astrophysics Data System (ADS)

    Fieber-Beyer, Sherry K.; Gaffey, Michael J.; Bottke, William F.; Hardersen, Paul S.

    2015-04-01

    The research is an integrated effort beginning with telescopic observations and extending through detailed mineralogical characterizations to provide constraints on the albedo, diameter, composition, and meteorite affinity of near-Earth object-potentially hazardous asteroid (NEO-PHA 2007 LE). Results of the analysis indicate a diameter of 0.56 kilometers (km) and an albedo of 0.08. 2007 LE exhibits a 1-?m absorption feature without a discernible Band II feature. Compositional analysis of 2007 LE reveal Fs17 and Fa19 values, which are consistent with the Fa and Fs values for the H-type ordinary chondrites (Fs14.5-18 and Fa16-20) and of Asteroid (6) Hebe (Fs17 and Fa15). Spectroscopically, 2007 LE does not appear like the average H-chondrite spectra, exhibiting a reddened spectrum and subdued absorption feature. Further investigation of the meteorite classes yielded a black chondrite, Rose City, which is both similar in mineralogy and spectrally to PHA 2007 LE. Dynamical analysis could not directly link the fall of the Rose City meteorite to 2007 LE. As it stands, 2007 LE and Rose City have a compositional link, and both could come from the same parent body/possible family, one known source of the H chondrites is (6) Hebe.

  18. Non-nebular Origin of Dark Mantles Around Chondrules and Inclusions in CM Chondrites

    NASA Technical Reports Server (NTRS)

    Trigo-Rodriquez, Josep M.; Rubin, Alan E.; Wasson, John T.

    2006-01-01

    Our examination of nine CM chondrites that span the aqueous alteration sequence leads us to conclude that compact dark fine mantles surrounding chondrules 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 chondrules 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 chondrules 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).

  19. Zaoyang chondrite cooling history from pyroxene Fe(2+)-Mg intracrystalline ordering and exolutions

    NASA Technical Reports Server (NTRS)

    Molin, G. M.; Tribaudino, M.; Brizi, E.

    1993-01-01

    The Zaoyang ordinary chondrite fell as a single 14.15-kg mass in Hubey province (China) in October 1984 and was classified as a non-brecciated H5 chondrite, shock facies b. Cooling rate in pyroxenes can be calculated down to about 1000 C by using fine textures and at still lower temperatures (700 to 200 C) by intracrystalline ordering processes. The crystal chemistry of clinopyroxene and orthopyroxene from the matrix of the H5 Zaoyang chondrite has been investigated by X-ray structure refinement and detailed microprobe analysis. By comparison with terrestrial pyroxenes cell and polyhedral volumes in clino- and orthopyroxenes show a low crystallization pressure. Fe(2+) and Mg are rather disordered in M1 and M2 sites of clino- and orthopyroxenes; the closure temperatures of the exchange reaction are 600 and 512 C respectively, which is consistent with a quite fast cooling rate, estimated of the order of one degree per day. The closure temperature for the intercrystalline Ca-Mg exchange reaction for clino- and orthopyroxene showing clinopyroxene lamellae about 10 microns thick. Kinetic evaluations based on the thickness of exolved lamellae give a cooling rate of not more than a few degrees per 10(exp 4) years. The different cooling rates obtained from Fe(2+)-Mg intracrystalline partitioning and exolution lamellae suggest an initial episode of slow cooling at 900 C, followed by faster cooling at temperatures of 600-500 C at low pressure conditions. The most probable scenario of the meteorite history seems that the exolved orthopyroxene entered the parental chondrite body after exolution had taken place at high temperature. Subsequent fast cooling occurred at low temperature after the formation of the body.

  20. Petrographic, chemical and spectroscopic evidence for thermal metamorphism in carbonaceous chondrites I: CI and CM chondrites

    NASA Astrophysics Data System (ADS)

    Tonui, Eric; Zolensky, Mike; Hiroi, Takahiro; Nakamura, Tomoki; Lipschutz, Michael E.; Wang, Ming-Sheng; Okudaira, Kyoko

    2014-02-01

    We present a comprehensive description of petrologic, chemical and spectroscopic features of thermally metamorphosed CI-like and CM (and CM-like) chondrites. Only two such CI chondrites have so far been discovered i.e. Y-86029 and Y-82162. Thermal metamorphism in these chondrites is apparent in their low contents of H2O, C and the most thermally labile trace elements, partial dehydration of matrix phyllosilicates and abundance of thermally decomposed Ca-Mg-Fe-Mn carbonates, which apparently resulted from heating of Mg-Fe carbonate precursors. The CM chondrites exhibit a wide range of aqueous and thermal alteration characteristics. This alteration was almost complete in Y-86720 and Y-86789, which also escaped alternating episodes of oxidation and sulfidization experienced by the others. Thermal metamorphism in the CM chondrites is apparent in loss of thermally labile trace elements and also in partial to almost complete dehydration of matrix phyllosilicates: heating was less uniform in them than in CI chondrites. This dehydration is also evident in strength and shapes of integrated intensities of the 3 ?m bands except in PCA 91008, which experienced extensive terrestrial weathering. Tochilinite is absent in all but Y-793321 probably due to heating. Textural evidence for thermal metamorphism is conspicuous in blurring or integration/fusion of chondrules with matrix in the more extensively heated (?600 °C) CM chondrites like PCA 91008 and B-7904. TEM and XRD analyses reveal that phyllosilicate transformation to anhydrous phases proceeds via poorly crystalline, highly desiccated and disordered 'intermediate' phases in the least and moderately heated (400-600 °C) carbonaceous chondrites like WIS 91600, PCA 91008 and Y-86029. These findings are significant in that they confirm that these phases occur in meteorites as well as terrestrial samples. Thermal alteration in these meteorites can be used to identify other carbonaceous chondrites that were thermally metamorphosed in their parent bodies. Combining RNAA trace element data for experimentally heated Murchison CM2 samples with petrographic and spectroscopic data, these thermally metamorphosed carbonaceous chondrites can be ordered by severity of open system heating as 400 °C ? Y-793321 < WIS91600 = EET90043 = A881655 < PCA91008 < B-7904 = Y-86029 < Y-82162 < Y-86720 = Y-86789 ? 700 °C. Nearly all heated carbonaceous chondrites discovered so far have been found in Antarctica, which is known to have sampled the flux of near-Earth material for much longer than exemplified by current falls.

  1. Ordinary Differential Equation System Solver

    Energy Science and Technology Software Center (ESTSC)

    1992-03-05

    LSODE is a package of subroutines for the numerical solution of the initial value problem for systems of first order ordinary differential equations. The package is suitable for either stiff or nonstiff systems. For stiff systems the Jacobian matrix may be treated in either full or banded form. LSODE can also be used when the Jacobian can be approximated by a band matrix.

  2. Alkaline Element Fractionations in LL-chondritic Breccias

    NASA Astrophysics Data System (ADS)

    Misawa, K.; Yokoyama, T.; Okano, O.

    2010-12-01

    Introduction: Fractionation of moderately volatile lithophile elements including alkaline elements was an important process in the early solar system. Alkali-rich igneous fragments (K-rich fragments) were found in brecciated LL-chondrites. These fragments in Kraehenberg (LL5), Bhola (LL3-6), and Yamato (Y)-74442 (LL4) show fractionated alkaline element patterns; for example, abundances of alkaline elements in the Kraehenberg fragment are ~0.5 x CI for Na, ~12 x CI for K,~45 x CI for Rb, and ~70 x CI for Cs [1]. In order to understand moderately volatile element fractionations, we have undertaken mineralogical and petrological studies on K-rich fragments in Kraehenberg [1], Bhola [2], and Y-74442 [3, 4]. Results and Discussion: Kraehenberg, Bhola, and Y-74442 consist of mineral fragments, K-rich fragments, impact-melt clasts, chondrules, and matrix. K-rich fragments in these meteorites are composed of 10-100 µm-sized euhedral olivine (~60 vol.%) and groundmass of brown glasses (~40 vol.%, including microcrystalline pyroxene) which are highly enriched in alkaline elements. Dendritic pyroxene and chromite (~1 µm in size) along with troilite (~10 µm in size) are commonly observed in the groundmass. The textures are different from those of impact melt clasts in ordinary chondrites. Chemical compositions of olivine in the K-rich fragments fall within the compositional range of equilibrated LL-chondrites (Fa26-32 [5]). Groundmass glasses in the Kraehenberg, Bhola, and Y-74442 fragments are almost identical in composition when plotted on a Na+K+Al-oxides-Ca+Mg+Fe-oxides-SiO2 ternary diagram [1]. The fractionation trend is also observed in an angular igneous fragment in Siena (LL5) [6]. The lack of K isotopic fractionation effects in the K-rich clast in Kraehenberg [7] implies that the enrichment of (heavier) alkaline elements occurred near-equilibrium conditions. The K-rich fragments in Kraehenberg and Y-74442 could be early solar system materials (~4.56 Ga [8, 9]). Similarities in textures, compositions, and fractionation patterns of the K-rich fragments suggest that they might be formed from related precursor materials with related processes. Complementarity of K-rich fragments and differentiated body alkali abundance patterns suggests that the fractionation could have occurred in the early solar nebula. Refs: [1] Wlotzka F. et al. (1983) Geochim. Cosmochim. Acta 47, 743. [2] Noonan A.F. et al. (1978) Geol. Survey Open File Report 78-701, 311. [3] Yanai K. et al. (1978) Mem. Natl. Inst. Polar Res. Spec. Issue 8, 110. [4] Ikeda Y. and Takeda H. (1979) Mem. Natl. Inst. Polar Res. Spec. Issue 15, 123. [5] Dodd R.T. (1981) Meteorites pp. 368, Cambridge Univ. Press. [6] Fodor R.V. and Keil K. (1978) Catalog of lithic fragments in LL-chondrites, Inst. Meteoritics Spec. Publ. No. 19, pp. 38, Univ. New Mexico, Albuquerque. [7] Humayun M. and Clayton R.N. (1995) Geochim. Cosmochim. Acta 59, 2131. [8] Kempe W. and Mueller O. (1969) Meteorite Res., pp. 418. [9] Nishiya N. et al. (1995) Okayama Univ. Earth Sci. Rep. 2, 91.

  3. Evidence of Microfossils in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Rozanov, Alexei Y.; Zhmur, S. I.; Gorlenko, V. M.

    1998-01-01

    Investigations have been carried out on freshly broken, internal surfaces of the Murchison, Efremovka and Orgueil carbonaceous chondrites using Scanning Electron Microscopes (SEM) in Russia and the Environmental Scanning Electron Microscope (ESEM) in the United States. These independent studies on different samples of the meteorites have resulted in the detection of numerous spherical and ellipsoidal bodies (some with spikes) similar to the forms of uncertain biogenicity that were designated "organized elements" by prior researchers. We have also encountered numerous complex biomorphic microstructures in these carbonaceous chondrites. Many of these complex bodies exhibit diverse characteristics reminiscent of microfossils of cyanobacteria such as we have investigated in ancient phosphorites and high carbon rocks (e.g. oil shales). Energy Dispersive Spectroscopy (EDS) analysis and 2D elemental maps shows enhanced carbon content in the bodies superimposed upon the elemental distributions characteristic of the chondritic matrix. The size, distribution, composition, and indications of cell walls, reproductive and life cycle developmental stages of these bodies are strongly suggestive of biology' These bodies appear to be mineralized and embedded within the meteorite matrix, and can not be attributed to recent surface contamination effects. Consequently, we have interpreted these in-situ microstructures to represent the lithified remains of prokaryotes and filamentous cyanobacteria. We also detected in Orgueil microstructures morphologically similar to fibrous kerite crystals. We present images of many biomorphic microstructures and possible microfossils found in the Murchison, Efremovka, and Orgueil chondrites and compare these forms with known microfossils from the Cambrian phosphate-rich rocks (phosphorites) of Khubsugul, Northern Mongolia.

  4. Intensive parameters of enstatite chondrite metamorphism

    NASA Technical Reports Server (NTRS)

    Fogel, Robert A.; Hess, Paul C.; Rutherford, Malcolm J.

    1989-01-01

    A geothermometer based on the assemblage kamacite-quartz-enstatite-oldhamite-troilite found in enstatite chondrites is described. Data obtained with the geothermometer reveal that the EL6 meteorites experienced temperatures exceeding 1000 C. These temperatures imply a metal-sulfide melting event that may have fractionated the melt from the source region.

  5. Csátalja, the largest H4-5 chondrite from Hungary

    NASA Astrophysics Data System (ADS)

    Kovács, János; Sajó, István; Márton, Zsuzsanna; Jáger, Viktor; Hegedüs, Tibor; Berecz, Tibor; Tóth, Tamás; Gyenizse, Péter; Podobni, András

    2015-01-01

    We report here for the first time the composition and mineralogical studies on a new meteorite, which was found in August 2012 near the village of Csátalja, Hungary (46°0'21''N; 18°59'27'E). The Csátalja meteorite is classified as a H4-5 ordinary chondrite with shock stage S2 and a degree of weathering W1 and the total mass is 15 kg. The Csátalja meteorite is characterized by well-defined chondrules composed either of olivine or pyroxene. X-ray diffractogram shows the primary phases olivine, pyroxene, kamacite, and albite. Metal particles were extracted from the bulk powdered samples exhibit only kamacite and small amounts of the intergrowth taenite/kamacite. Raman spectra of forsterite indicate that Csátalja meteorite suffered from relatively low shock pressure regime. The texture of chondrules varies from nonporphyritic (e.g., barred olivine, radial pyroxene) to porphyritic ones (e.g., granular olivine as well as olivine pyroxene). The meteorite name has not yet approved by the Nomenclature Committee of the Meteoritical Society.

  6. Chondrites and the Protoplanetary Disk, Part 3

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Contents include the following: Ca-, Al-Rich Inclusions and Ameoboid Olivine Aggregates: What We Know and Don t Know About Their Origin. Aluminium-26 and Oxygen Isotopic Distributions of Ca-Al-rich Inclusions from Acfer 214 CH Chondrite. The Trapping Efficiency of Helium in Fullerene and Its Implicatiion to the Planetary Science. Constraints on the Origin of Chondritic Components from Oxygen Isotopic Compositions. Role of Planetary Impacts in Thermal Processing of Chondrite Materials. Formation of the Melilite Mantle of the Type B1 CAIs: Flash Heating or Transport? The Iodine-Xenon System in Outer and Inner Portions of Chondrules from the Unnamed Antarctic LL3 Chondrite. Nucleosynthesis of Short-lived Radioactivities in Massive Stars. The Two-Fluid Analysis of the Kelvin-Helmholtz Instability in the Dust Layer of a Protoplanetary Disk: A Possible Path to the Planetesimal Formation Through the Gravitational Instability. Shock-Wave Heating Model for Chonodrule Formation: Heating Rate and Cooling Rate Constraints. Glycine Amide Hydrolysis with Water and OH Radical: A Comparative DFT Study. Micron-sized Sample Preparation for AFM and SEM. AFM, FE-SEM and Optical Imaging of a Shocked L/LL Chondrite: Implications for Martensite Formation and Wave Propagation. Infrared Spectroscopy of Chondrites and Their Components: A Link Between Meteoritics and Astronomy? Mid-Infrared Spectroscopy of CAI and Their Mineral Components. The Origin of Iron Isotope Fractionation in Chondrules, CAIs and Matrix from Allende (CV3) and Chainpur (LL3) Chondrites. Protoplanetary Disk Evolution: Early Results from Spitzer. Kinetics of Evaporation-Condensation in a Melt-Solid System and Its Role on the Chemical Composition and Evolution of Chondrules. Oxygen Isotope Exchange Recorded Within Anorthite Single Crystal in Vigarano CAI: Evidence for Remelting by High Temperature Process in the Solar Nebula. Chondrule Forming Shock Waves in Solar Nebula by X-Ray Flares. Organic Globules with Anormalous Nitrogen Isotopic Compositions in the Tagish Lake Meteorite: Products of Primitive Organic Reactions. Yet Another Chondrule Formation Scenario. CAIs are Not Supernova Condensates. Microcrystals and Amorphous Material in Comets and Primitive Meteorites: Keys to Understanding Processes in the Early Solar System. A Nearby Supernova Injected Short-lived Radionuclides into Our Protoplanetary Disk. REE+Y Systematics in CC and UOC Chondrules. Meteoritic Constraints on Temperatures, Pressures, Cooling Rates, Chemical Compositions, and Modes of Condensation in the Solar Nebula. The I-Xe Record of Long Equilibration in Chondrules from the Unnamed Antarctic Meteorite L3/LL3. Early Stellar Evolution.

  7. Reclassification of Villalbeto de la Peña—Occurrence of a winonaite-related fragment in a hydrothermally metamorphosed polymict L-chondritic breccia

    NASA Astrophysics Data System (ADS)

    Bischoff, Addi; Dyl, Kathryn A.; Horstmann, Marian; Ziegler, Karen; Wimmer, Karl; Young, Edward D.

    2013-04-01

    The Villalbeto de la Peña meteorite that fell in 2004 in Spain was originally classified as a moderately shocked L6 ordinary chondrite. The recognition of fragments within the Villalbeto de la Peña meteorite clearly bears consequences for the previous classification of the rock. The oxygen isotope data clearly show that an exotic eye-catching, black, and plagioclase-(maskelynite)-rich clast is not of L chondrite heritage. Villalbeto de la Peña is, consequently, reclassified as a polymict chondritic breccia. The oxygen isotope data of the clast are more closely related to data for the winonaite Tierra Blanca and the anomalous silicate-bearing iron meteorite LEW 86211 than to the ordinary chondrite groups. The REE-pattern of the bulk inclusion indicates genetic similarities to those of differentiated rocks and their minerals (e.g., lunar anorthosites, eucritic, and winonaitic plagioclases) and points to an igneous origin. The An-content of the plagioclase within the inclusion is increasing from the fragment/host meteorite boundary (approximately An10) toward the interior of the clast (approximately An52). This is accompanied by a successive compositionally controlled transformation of plagioclase into maskelynite by shock. As found for plagioclase, compositions of individual spinels enclosed in plagioclase (maskelynite) also vary from the border toward the interior of the inclusion. In addition, huge variations in oxygen isotope composition were found correlating with distance into the object. The chemical and isotopical profiles observed in the fragment indicate postaccretionary metamorphism under the presence of a volatile phase.

  8. Evidence for a Carbonaceous Chondrite Parent Body With Near-TFL Oxygen Isotopes From Unique Metachondrite Northwest Africa 2788

    NASA Astrophysics Data System (ADS)

    Bunch, T. E.; Irving, A. J.; Rumble, D.; Korotev, R. L.

    2006-12-01

    Metachondrites: Metachondrites are newly recognized groups of stony meteorites that lack chondrules, but which have elemental and oxygen isotopic compositions and textures suggesting that they have been transformed by metamorphism or partial melting from precursor ordinary and carbonaceous chondrites on relatively large parent bodies [1]. The best known examples have affinities to CR (e.g., LEW 88763), CV (e.g., NWA 3133), H, L and LL chondrites; conversely there is evidence that winonaites and acapulcoites also are metachondrites derived from chondritic precursors (represented by rare chondrites such as NWA 1463 and Monument Draw). With increased sampling of new meteorites from both hot and cold desert regions, there is an emerging realization that the early solar system was populated with many relatively large differentiated planetary bodies complete with metallic cores, silicate mantles and chondritic regoliths of various types. The affinity of a particular metachondrite to a specific chondrite class relies mainly on oxygen isotopic analysis combined with distinctive elemental ratios in bulk rocks and constituent minerals (notably Fe/Mn and Ca/Na ratios, which are quite different for ordinary vs. various carbonaceous chondrite classes). Northwest Africa 2788: This specimen exhibits a metamorphic texture with triple grain junctions (grain size is mostly <0.5 mm, a few grains reach nearly 1 mm), and is composed of orthopyroxene (63 vol.%, Fs18.0Wo1.3, FeO/MnO = 30), olivine (27 vol.%, Fa21.4, FeO/MnO = 57-61), clinopyroxene (5 vol.%, Fs7.4Wo49.8, TiO2 = 0.74 wt.%, Cr2O3 = 0.63 wt.%, FeO/MnO = 19), plagioclase (5 vol.%, An53.9Or3), and accessory merrillite, troilite and metal. Replicate oxygen isotopic analyses of acid-washed bulk samples by laser fluorination gave ?18O = 6.004, 6.082; ?17O = 3.082, 3.102; ?17O = -0.076, -0.097 per mil (for TFL slope of 0.526); these values plot close to but below the TFL. The elevated Fe/Mn ratios in the mafic silicates coupled with the relatively calcic plagioclase are hallmarks of carbonaceous chondrite bulk compositions [2], but the oxygen isotopic compositions are quite unlike those of any known chondrite class. Bulk rock abundances by INAA relative to Allende analyzed simultaneously are 0.89 times for Fe and ~1.2 times for Cr, REE and Hf. We conclude that NWA 2788 is a unique metachondrite sampled from a new, perhaps now-disaggregated parent body accreted from a distinctive oxygen isotopic reservoir. It is possible that this body also may harbor or have harbored chondrule-bearing carbonaceous regolith materials ('CT chondrites') that are yet to be found or recognized. [1] Irving A. J. et al. (2005) 68th Met. Soc. Mtg., #5218; Bunch T. E. et al. (2005) LPS XXXVI, #2308 [2] Wasson J. T. and Kallemyn G. W. (1988) Phil. Trans. Roy. Soc. Lond. A325, 535-544.

  9. Mineralogy of Frontier Mountains L7 Chondrites with Reference to the Chondrite-Achondrite Transition

    NASA Astrophysics Data System (ADS)

    Baba, T.; Takeda, H.

    1992-07-01

    Achondrites have been generally assumed to be derived from magma formed from some chondritic melts or mixtures and the genetic model often proposes specific crystallization sequences to account for particular achondrite properties. However, some achondrites such as primitive achondrites (Acapulco-type chondrites and/or Lodranites) and ureilites still preserve primitive signatures of chondritic source materials (Palme et al., 1981). To account for formation of such meteorites, a model involving formation of ultramafic meteorites without invoking large-scale melting such as magmatic process has been proposed (Takeda, 1989). The process to form extensively recrystallized chondrites (H7,L7,LL7) should be investigated as a first step to make such meteorites. We investigated the textures and chemical compositions of two L7 chondrites from Frontier Mountains by electron probe microanalysis (EPMA) and scanning electron microscope (JEOL 840A SEM) with chemical mapping analysis (CMA) utility, and compared them with other type 7 chondrites, primitive achondrites, and ureilites. Two polished thin sections, FRO90058,001 and FRO90066,001 have been supplied from the EUROMET. The textures of FRO90058 and FRO90066 are very similar. Textural characteristics of some parts of the samples are rather similar to primitive achondrites than chondrites. However, a few chondrules still remain in FRO90058. Two samples are composed of subangular recrystallized clasts and much comminuted grains of clasts and minerals filling interstices between the clasts. The facts indicate that they are partly brecciated. The recrystallized parts show coarse-grained textures of orthopyroxene(opx), olivine(oliv) and opaque minerals. In fine- grained portions, silicate minerals exhibit granoblastic texture. Plagioclase is present as elongated, irregular grains in the fine-grained portion, while in coarser regions, plagioclase fills interstices or channels and is intruded by opx. Olivine grains are compositionally uniform with mean Fa=25. Opx of FRO90058 and FRO90066 are similar and their chemical compositions are nearly uniform from grain to grain and within the range of Mg# (=Mg x 100/(Mg+Fe) mol%) from 79 to 80. In the present L7 chondrites, the Ca content of opx is lower and the Ca-content of augite is higher than that of Y74160(LL7) and that of augite is higher, indicating that temperature of equilibration is lower than that of Y74160(LL7) (Takeda et al., 1984). The plagioclase compositions in the LL7(Y74160) chondrite show chemical zoning and their ranges differ from one place to another. The plagioclase compositions of FRO L7 chondrites also show minor chemical variation (Ab80-87), though it is not as large as Y74160. We interpret these zonings as resulted from plagioclase growth in localized areas where compositions of Ca-Na-Al-rich materials in their regions are slightly variable. For an internal heat source, such as radioactive decay, temperature increase and decrease would require longer time and plagioclase compositions would be homogenized. Impact process seems more likely heat source although shock features seem to have been erased by subsequent recrystallization. From mineralogical and chemical observations, these chondrites appear to show L6 chondrite-like features, although their textures are rather similar to those of some primitive achondrites. This type of chondrite may be on the road to becoming achondrites, but loss of low-temperature melts are not clearly shown in these samples. We thank EUROMET for the meteorite samples. References: Takeda H. (1989) Earth Planet. Sci. Lett. 93, 181- 194; Takeda H., Huston T.J., and Lipschutz M.E. (1984) Earth Planet. Sci. Lett. 71, 329-339; Palme H., Schultz L., Spettel B., Weber H.W., Wanke H., Michel-Levy M.C., and Lorin J.C. (1981) Geochim. Cosmochim. Acta 45, 727-752.

  10. Mn-Cr ages of dolomites in CI chondrites and the Tagish Lake ungrouped carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Fujiya, Wataru; Sugiura, Naoji; Sano, Yuji; Hiyagon, Hajime

    2013-01-01

    53Mn-53Cr ages have been measured for dolomites in three CI chondrites and an ungrouped C2 chondrite Tagish Lake. For an accurate age determination, we utilized, in contrast to previous works, a matrix-matched carbonate standard to appropriately correct the observed Mn/Cr ratios. The Mn-Cr data of the dolomites most likely represent isochrons with chronological significances and the obtained ages are concentrated in 4563.8-4562.5 million years ago (4.4-5.7 million years after the birth of the solar system). The ages of the CI and Tagish Lake dolomites are very similar to those of carbonates in CM chondrites, although CI and CM chondrites are likely to have different alteration histories. The similar carbonate ages in various carbonaceous chondrites suggest that the aqueous activities in hydrous asteroids initiated almost concurrently. If this is the case, the most plausible heat source for the aqueous alteration is the decay energy of short-lived radionuclides, especially 26Al. We carried out a model calculation for the thermal history of the CI chondrite parent body assuming that 26Al is the dominant heat source. By two different approaches to estimate the accretion time of the CI chondrite parent body, we conclude that it accreted 3.0-3.9 million years after the birth of the solar system. This is also likely to be the case for the CM chondrite and Tagish Lake parent bodies, because the result of the calculation is not sensitive to the ice abundance. Therefore, we stress that near the condensation front of water ice, meteorite parent bodies with abundant ice accreted almost simultaneously at 3-4 million years after CAI formation. Combining our Mn-Cr ages of the dolomites with those of breunnerites reported previously (the youngest one is 4554.6 million years ago), we found that the aqueous alteration in the CI chondrite parent body lasted for at least 9 million years. Therefore, the parent body should be large enough (>50 km in radius) so that the internal heat had been kept for 9 million years.

  11. Silicon isotope evidence against an enstatite chondrite Earth.

    PubMed

    Fitoussi, Caroline; Bourdon, Bernard

    2012-03-23

    The compositions of Earth materials are strikingly similar to those of enstatite chondrite meteorites in many isotope systems. Although this suggests that Earth largely accreted from enstatite chondrites, definitive proof of this model has been lacking. By comparing the silicon (Si) isotope signatures of several extraterrestrial materials with terrestrial samples, we show that they cannot be explained by core-formation scenarios involving a bulk Earth of enstatite chondrite composition. Si isotope similarities between the bulk silicate Earth and the Moon preclude the existence of a hidden reservoir in the lower mantle, a necessary condition of the enstatite chondrite model, and require an equilibrium process after the Moon-forming impact. A three-end-member chondritic mixing model for Earth reconciles the Si isotope similarities between enstatite chondrites and Earth. PMID:22383806

  12. The Structure and Composition of Large Metal Nodule from the Ghubara L5 Chondrite

    NASA Astrophysics Data System (ADS)

    Lorenz, C. A.; Teplyakova, S. N.; Korochantsev, A. V.; Kononkova, N. N.; Roshina, I. A.; Sadilenko, D. A.

    2009-03-01

    The large metal nodule was found in the Ghubara L5 chondrite. The metal demonstrates widmannstätten texture that is unique in chondritic metal. The nodule could be formed by the partial or complete impact melting of chondritic precursor.

  13. Deducing Wild 2 Components with a Statistical Dataset of Olivine in Chondrite Matrix

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    Introduction: A preliminary exam of the Wild 2 olivine yielded a major element distribution that is strikingly similar to those for aqueously altered carbonaceous chondrites (CI, CM, and CR) [1], in which FeO-rich olivine is preferentially altered. With evidence lacking for large-scale alteration in Wild 2, the mechanism for this apparent selectivity is poorly understood. We use a statistical approach to explain this distribution in terms of relative contributions from different chondrite forming regions. Samples and Analyses: We have made a particular effort to obtain the best possible analyses of both major and minor elements in Wild 2 olivine and the 5-30 micrometer population in chondrite matrix. Previous studies of chondrite matrix either include larger isolated grains (not found in the Wild 2 collection) or lack minor element abundances. To overcome this gap in the existing data, we have now compiled greater than 10(exp 3) EPMA analyses of matrix olivine in CI, CM, CR, CH, Kakangari, C2-ungrouped, and the least equilibrated CO, CV, LL, and EH chondrites. Also, we are acquiring TEM/EDXS analyses of the Wild 2 olivine with 500s count times, to reduce relative errors of minor elements with respect to those otherwise available. Results: Using our Wild 2 analyses and those from [2], the revised major element distribution is more similar to anhydrous IDPs than previous results, which were based on more limited statistics (see figure below). However, a large frequency peak at Fa(sub 0-1) still persists. All but one of these grains has no detectable Cr, which is dissimilar to the Fa(sub 0-1) found in the CI and CM matrices. In fact, Fa(sub 0-1) with strongly depleted Cr content is a composition that appears to be unique to Kakangari and enstatite (highly reduced) chondrites. We also note the paucity of Fa(sub greater than 58), which would typically indicate crystallization in a more oxidizing environment [3]. We conclude that, relative to the bulk of anhydrous IDPs, Wild 2 may have received a larger contribution from the Kakangari and/or enstatite chondrite forming regions. Alternatively, Wild 2 may have undergone accretion in an anomalously reducing region, marked by nebular condensation of this atypical forsterite. In [4], a similar conclusion was reached with an Fe-XANES study. We will also use similar lines of reasoning, and our previous conclusions in [5], to constrain the relative contributions of silicates that appear to have been radially transported from different ordinary and carbonaceous chondrite forming regions to the Kuiper Belt. In addition, the widespread depletion of Cr in these FeO-rich (Fa(sub greater than 20)) fragments is consistent with mild thermal metamorphism in Wild 2.

  14. The formation conditions of chondrules and chondrites

    USGS Publications Warehouse

    Alexander, C.M. O'D.; Grossman, J.N.; Ebel, D.S.; Ciesla, F.J.

    2008-01-01

    Chondrules, which are roughly millimeter-sized silicate-rich spherules, dominate the most primitive meteorites, the chondrites. They formed as molten droplets and, judging from their abundances in chondrites, are the products of one of the most energetic processes that operated in the early inner solar system. The conditions and mechanism of chondrule formation remain poorly understood. Here we show that the abundance of the volatile element sodium remained relatively constant during chondrule formation. Prevention of the evaporation of sodium requires that chondrules formed in regions with much higher solid densities than predicted by known nebular concentration mechanisms. These regions would probably have been self-gravitating. Our model explains many other chemical characteristics of chondrules and also implies that chondrule and planetesimal formation were linked.

  15. Carbonaceous chondritic material in the solar system

    NASA Technical Reports Server (NTRS)

    Wilkening, L. L.

    1978-01-01

    Carbonaceous chondritic matrix material (CCMM) appears to be an important planet-forming unit in the mid-solar system, from the orbits of Mars to that of Uranus. The type specimen for CCMM is the low-temperature (400-500 K) assemblage of clay minerals, organic polymer, magnetite, and Ni-rich iron sulfides which constitutes the black, fine-grained matrix of primitive carbonaceous chondrites. Solar-system objects which appear to be partly or wholly made of CCMM are the satellites of Mars, most asteroids, interplanetary dust, and, perhaps, comets, satellites of the outer planets and the rings of Uranus. CCMM constituents probably formed by low-temperature reactions of higher-temperature condensates with the ambient solar composition gas, or in the case of the organic polymer, by reactions of gaseous species catalyzed by solids.

  16. Amino acids of the Nogoya and Mokoia carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Moore, C. B.

    1976-01-01

    Amino acids were found in acid hydrolyzed, hot water extracts of the Nogoya (C2) and Mokoia (C3V) chondrites. About 40 n moles/g of amino acids were found in the Nogoya extract while Mokoia contained less than 1 n mole/g. The amino acid composition of Nogoya differs from that of other C2 chondrites studied earlier. The results from Mokoia are similar to previous data obtained from the C3V chondrite Allende.

  17. Are carbonaceous chondrites primitive or processed - A review

    NASA Technical Reports Server (NTRS)

    Mcsween, H. Y., Jr.

    1979-01-01

    According to the results of the present analysis, carbonaceous chondrites are obviously not pristine samples of proto-solar-system condensates. In terms of chemistry, however, these chondrites may represent the most primitive solar system materials known. It appears that the alterations experienced by carbonaceous chondrites were isochemical, or nearly so, so that their bulk compositions have remained practically unchanged, provided that the analyses are representative of large portions of the meteorites.

  18. MATH 411 SPRING 2001 Ordinary Differential Equations

    E-print Network

    Alekseenko, Alexander

    MATH 411 SPRING 2001 Ordinary Differential Equations Schedule # 749025 TR 01:00-02:15 316 Boucke will be an introduction to ordinary differential equations. During the classes basic concepts of theory theory and implementations of ordinary differential equations. Text. Ray Redhefer Differential equations

  19. Size distributions in two porous chondritic micrometeorites

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.

    1993-01-01

    Quantitative size measurements of granular units (GUs), and nm-sized minerals in these units, in two porous chondritic micrometeorites are investigated. The matrix of these micrometeorites consist of loosely packed, 0.1 micron-sized, GUs. These objects were a major component of the solar nebula dust that accreted into protoplanets. The matrix in micrometeorite W7010*A2 has a fractal dimension with a small coefficient that supports efficient sticking of carbon-rich GUs during accretion. The fractal nature of the matrix provides a way to calculate the density using the aggregate size. The resulting very low density for porous chondritic micrometeorites is 0.08-0.14 g/cu cm, which supports the view that they are the solid debris from unconsolidated solar system bodies. Chondritic GUs contain ultrafine olivines, pyroxenes, and sulfides, embedded in hydrocarbons and amorphous carbons. Nanocrystals in the micrometeorites W7010*A2 and U2015*B show log normal size distributions. The high incidence of disk-shaped grains, a changeover from disk-shaped to euhedral grains, the unevolved nature of the size distributions, and multiple populations for grains less than 127 nm in size, are consistent with continuous postaccretion nucleation and growth in amorphous GUs, including coarsening via Ostwald ripening.

  20. Polyhedral Serpentine Grains in CM Chondrites

    NASA Technical Reports Server (NTRS)

    Zega, Thomas J.; Garvie, Laurence A. J.; Dodony, Istvan; Stroud, Rhonda M.; Buseck, Peter R.

    2005-01-01

    CM chondrites are primitive rocks that experienced aqueous alteration in the early solar system. Their matrices and fine-grained rims (FGRs) sustained the effects of alteration, and the minerals within them hold clues to the aqueous reactions. Sheet silicates are an important product of alteration, and those of the serpentine group are abundant in the CM2 chondrites. Here we expand on our previous efforts to characterize the structure and chemistry of serpentines in CM chondrites and report results on a polyhedral form that is structurally similar to polygonal serpentine. Polygonal serpentine consists of tetrahedral (T) sheets joined to M(2+)-centered octahedral (O) sheets (where (M2+) is primarily Mg(2+) and Fe(2+)), which give rise to a 1:1 (TO) layered structure with a 0.7-nm layer periodicity. The structure is similar to chrysotile in that it consists of concentric lizardite layers wrapped around the fiber axis. However, unlike the rolled-up chrysotile, the tetrahedral sheets of the lizardite layers are periodically inverted and kinked, producing sectors. The relative angles between sectors result in 15- and 30-sided polygons in terrestrial samples.

  1. The meteorite Moss - a rare carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Bilet, M.; Roaldset, E.

    2014-07-01

    On July 14, 2006, at about 10:20 a.m. local daylight time (UTC+2), a bright fireball travelling SSE-NNV was witnessed from the Baltic Sea to SE Norway. On the east side of the Oslo fiord, around Moss, an explosion and a rumbling sound was heard, and pieces were observed falling. Rapid recovery of meteorite stones gave an opportunity for detailed petrological and geochemical investigations, including analyses of indigenous organic species, and short lived isotopes. The meteorite is a chondritic stone meteorite, with some carbon (0.21-0.25 wt% C). The cosmic-ray exposure (CRE) age is 14 Ma, i.e. when Moss was ejected from its parent body. Gas retention ages are approximately 3.95x10^9 yr (U/Th/He) and 4.43x10^9 yr (K/Ar), respectively. The meteorite has the official name Moss, and is classified as carbonaceous chondrite type CO3.6. It was the first witnessed fall of a CO3 chondrite since Kainsaz in Russia in 1937.

  2. New Ideas: Ordinary is Extraordinary

    PubMed Central

    Dodson, Michael; Fernyhough, Melinda; Antonio, Jose; Bucci, Luke

    2004-01-01

    With the initial issue of this journal, a new challenge has been offered tothe world of sports nutrition: initiate "team oriented" research and clinical trials in order to make dynamic progress in terms of understandingand applying nutrition principals to the field of competitive sports. It is our further challenge that these teams think "outside the box" in terms of their approach to elucidating new concepts through which nutritional interventions might play a role in the regulation of muscle growth and repair, athletic performance and endurance, and mental acuity. What was once thought of as extraordinary might now be approached as ordinary, if the correct composition of "teams" were formed.

  3. Carbonate abundances and isotopic compositions in chondrites

    NASA Astrophysics Data System (ADS)

    Alexander, C. M. O'd.; Bowden, R.; Fogel, M. L.; Howard, K. T.

    2015-04-01

    We report the bulk C abundances, and C and O isotopic compositions of carbonates in 64 CM chondrites, 14 CR chondrites, 2 CI chondrites, LEW 85332 (C2), Kaba (CV3), and Semarkona (LL3.0). For the unheated CMs, the total ranges of carbonate isotopic compositions are ?13C ? 25-75‰ and ?18O ? 15-35‰, and bulk carbonate C contents range from 0.03 to 0.60 wt%. There is no simple correlation between carbonate abundance and isotopic composition, or between either of these parameters and the extent of alteration. Unless accretion was very heterogeneous, the uncorrelated variations in extent of alteration and carbonate abundance suggests that there was a period of open system behavior in the CM parent body, probably prior to or at the start of aqueous alteration. Most of the ranges in CM carbonate isotopic compositions can be explained by their formation at different temperatures (0-130 °C) from a single fluid in which the carbonate O isotopes were controlled by equilibrium with water (?18O ? 5‰) and the C isotopes were controlled by equilibrium with CO and/or CH4 (?13C ? -33‰ or -20‰ for CO- or CH4-dominated systems, respectively). However, carbonate formation would have to have been inefficient, otherwise carbonate compositions would have resembled those of the starting fluid. A quite similar fluid composition (?18O ? -5.5‰, and ?13C ? -31‰ or -17‰ for CO- or CH4-dominated systems, respectively) can explain the carbonate compositions of the CIs, although the formation temperatures would have been lower (~10-40 °C) and the relative abundances of calcite and dolomite may play a more important role in determining bulk carbonate compositions than in the CMs. The CR carbonates exhibit a similar range of O isotopes, but an almost bimodal distribution of C isotopes between more (?13C ? 65-80‰) and less altered samples (?13C ? 30-40‰). This bimodality can still be explained by precipitation from fluids with the same isotopic composition (?18O ? -9.25‰, and ?13C ? -21‰ or -8‰ for CO- or CH4-dominated systems, respectively) if the less altered CRs had higher mole fractions of CO2 in their fluids. Semarkona and Kaba carbonates have some of the lightest C isotopic compositions of the meteorites studied here, probably because they formed at higher temperatures and/or from more CO2-rich fluids. The fluids responsible for the alteration of chondrites and from which the carbonates formed were almost certainly accreted as ices. By analogy with cometary ices, CO2 and/or CO would have dominated the trapped volatile species in the ices. The chondrites studied are too oxidized for CO-dominated fluids to have formed in their parent bodies. If CH4 was the dominant C species in the fluids during carbonate formation, it would have to have been generated in the parent bodies from CO and/or CO2 when oxidation of metal by water created high partial pressures of H2. The fact that the chondrite carbonate C/H2O mole ratios are of the order predicted for CO/CO2-H2O ices that experienced temperatures of >50-100 K suggests that the chondrites formed at radial distances of <4-15 AU.

  4. 5 CFR 831.1405 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Ordinary and necessary living expenses. 831.1405...CONTINUED) RETIREMENT Standards for Waiver of Overpayments... Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include...

  5. 5 CFR 831.1405 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Ordinary and necessary living expenses. 831.1405...CONTINUED) RETIREMENT Standards for Waiver of Overpayments... Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include...

  6. Cumberland Falls chondritic inclusions - Mineralogy/petrology of a forsterite chondrite suite

    NASA Technical Reports Server (NTRS)

    Neal, C. W.; Lipschutz, M. E.

    1981-01-01

    The mineralogy and petrology of a suite of chondritic inclusions from the Cumberland Falls aubrite are investigated in order to clarify the relation of the inclusions to each other, forsterite chondrites, and the aubrites. Thin sections of nine chondritic inclusions and the achondritic matrix of Cumberland Falls were examined in reflected light, then analyzed for up to 12 elements by electron microprobe techniques. Minerals detected in abundant quantities include low-Ca pyroxene, olivine, plagioclase, kamacite, taenite, schreibersite, troilite, ferroan alabandite and daubreelite; diospide, oldhamite and a Ti-rich sulfide are found in one or two inclusions. The mineralogic compositions indicate similar degrees of reduction for the inclusions in the Cumberland Falls meteorites and in four meteorites identified as forsterite chondrites (Kakangari, Mt. Morris, Pontlyfni and Winona). The inclusions are found to be of a primitive composition, corresponding to petrological types 2 or 3, while the identification of jadeitic pyroxene in nearly all inclusions indicates a substantial degree of shock. The results suggest that the inclusions formed from nebular material that condensed and accreted over a broad redox range, and experienced tertiary shock in a collision with an enstatite meteorite in which the Cumberland Falls meteorite formed.

  7. R Raman Spectroscopy and Petrology of Antarctic CR Chondrites: Comparison with Other Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Komatsu, M.; Fagan, T. J.; Yamaguchi, A.; Mikouchi, T.; Zolensky, M. E.; Yasutake, M.

    2015-01-01

    In Renazzo-like carbonaceous (CR) chondrites, abundant original Fe,Ni-metal is preserved in chrondules, but the matrix is characterized by fine-grained magnetite with phyllosilicate. This combination of reduced Fe in chrodrules with oxidized Fe and phyllosilicate in the matrix has been attributed to aqueous alteration of matrix at relatively low temperatures.

  8. Thursday, March 26, 2009 CHONDRITE ACCRETION AND EARLY HISTORY

    E-print Network

    Rathbun, Julie A.

    , and the thermal history of MIL05029, an igneous rock with L-chondritic affinity, suggest formation as an impact chondrites Vigarano, Efremovka, Allende, Mokoia, Grosnaja and Kaba are amongst the most studied rocks of metamorphism of these clasts to similar clasts in eucrites and to understand the igneous processes

  9. The Insoluble Organic Matter of the Paris CM Chondrite

    NASA Astrophysics Data System (ADS)

    Vinogradoff, V.; Remusat, L.; Bernard, S.; Le Guillou, C.

    2015-07-01

    We study the IOM of the Paris carbonaceous chondrite, considered as one of the least altered chondrites, and compared it to Murchison IOM. Paris CM is likely the best CM sample available to infer the nature of the OM accreted on the CM parent body.

  10. Rumuruti: A New Carlisle Lakes-type Chondrite

    NASA Astrophysics Data System (ADS)

    Schulze, H.; Otto, J.

    1993-07-01

    We report here preliminary results of the investigation of a meteorite that fell on January 28, 1934, at 10:45 p.m. at Rumuruti, Kenya. The stone, weighing originally about 75 g, was part of a shower of a few pounds. It was picked up immediately after the fall and has been in the collection of the Museum fur Naturkunde in Berlin since 1938, but it has never been investigated. The stone has a black crust. A cut exhibits a nice light-dark structure typical of regolithic breccias. The numerous clasts are light-grey and reach up to 7 mm. The groundmass is dark grey. The portion of chondrules in the meteorite is rather small. They are often broken or irregularly shaped. The mineralogical investigation revealed a quite equilibrated olivine with a high fayalite content ranging in composition from Fa37 to Fa42 and averaging Fa39 (PMD 2.4; n = 66). The grains are up to 400 micrometers and often appear to be fragments of larger lithologies. Low-Ca pyroxene is much less abundant. It is unequilibrated with a mean of approximately Fs26 (n = 2). It is smaller than olivine (up to ~100 micrometers) and often shows polysynthetical twinning. A Ca-rich pyroxene was measured having En43Fs17Wo40. The common plagioclase reaches several micrometers and is mostly of oligoclasic composition with a mean of Ab85An11Or5 (n = 15), similar to OCs [1]. Also whitlockite of a composition similar to OCs [2] has been observed. Common sulfides comprise pentlandite (~35 wt% Ni) and low-Ni iron sulfide, which is pyrrhotite according to powder diffraction patterns. They occur individually or intergrown as grains of up to 1 mm. Pentlandite partly forms flame-like exsolutions in pyrrhotite. Also chalcopyrite, which is otherwise a rare mineral in meteorites [3], can be observed in grains of up to 50 micrometers. It is generally intergrown with the other sulfides. The common chromian spinel is Ti-rich (TiO2 ~6 wt%), Cr2O3 ranges from 32 to 48 wt%, and FeO from 37 to 53 wt%. For charge balance a high Fe3+-content is required (12-51 mol% of the iron). The mean composition of this spinel phase can be expressed as a mixture of the end members chromite (55 mol%), ulvospinel (17 mol%), magnetite (15 mol%), and spinel (9 mol%). Only the magnetite (4-25 mol%) and the chromite component (46-68 mol%) are strongly variable, obviously substituting each other. Chromian spinel occurs intergrown with the sulfides, as xenomorphic or chondrulelike individual grains (up to 200 micrometers) or as inclusions in the olivine. Nickel-iron is a rare phase. Only four grains of up to 30 micrometers have been observed. It seems to be associated with pentlandite and is very rich in Ni (67 wt% Ni). The homogeneity of the olivine and the grain size of plagioclase indicates a classification as a type-4 chondrite, whereas some glass in a chondrule points also to type 3. A refined investigation of clasts and groundmass will provide more clarity. Rumuruti is only mildly shocked (S2 according to [4]), but a vein restricted to one of the light clasts indicates that components of the meteorite experienced higher shock pressures. The unusual assemblage of fayalite-rich olivine (Fa39), Ti- and Fe3+-rich chromite, pentlandite, pyrrhotite, and chalcopyrite is comparable to the highly oxidized Carlisle Lakes-type meteorites [3,5]. Rumuruti now brings this group, together with Carlisle Lakes, ALH85151, Y75302 [3], and Acfer 217 [6], to five meteorites where Rumuruti is the first observed fall. References: [1] Van Schmus W. R. and Ribbe P. H. (1968) GCA, 32, 1327-1342. [2] Van Schmus W. R. and Ribbe P. H. (1969) GCA, 33, 637-640. [3] Rubin A. E. and Kallemeyn G. W. (1989) GCA, 53, 3035-3044. [4] Stoffler D. et al. (1991) GCA, 55, 3845-3867. [5] Weisberg M. K. et al. (1991) GCA, 55, 2657-2669. [6] Bischoff A. et al. (1993) Meteoritics, submitted.

  11. Multivariate Statistical Analysis of Labile Trace Elements in H Chondrites: Evidence for Meteoroid Streams

    NASA Astrophysics Data System (ADS)

    Wolf, S. F.; Lipschutz, M. E.

    1992-07-01

    Differences have been observed between meteorite populations with vastly different terrestrial ages, i.e. Antarctic and non-Antarctic meteorite populations (Koeberl and Cassidy, 1991 and references therein). Comparisons of labile trace element contents (Wolf and Lipschutz, 1992) and induced TL parameters (Benoit and Sears, 1992) in samples from Victoria Land and Queen Maud Land, populations which also differ in mean terrestrial age (Nishiizumi et al, 1989), show significant differences consistent with different average thermal histories. These differences are consistent with the proposition that the flux of meteoritic material to Earth varied temporally. Variations in the flux of meteoritic material over time scales of 10^5 10^6 y require the existence of undispersed streams of meteoroids of asteroidal origin which were initially disputed by Wetherill ( 1986) but have since been observed (Olsson-Steele, 1988; Oberst, 1989; Halliday et al. 1990). Orbital evidence for meteoroid and asteroid streams has been independently obtained by others, particularly Halliday et al.(1990) and Drummond (1991). A group of H chondrites of various petrographic types and diverse CRE ages that yielded 16 falls from 1855 until 1895 in the month of May has been proposed to be two co-orbital meteoroid streams with a common source (R. T. Dodd, personal communication). Compositional evidence of a preterrestrial association of the proposed stream members, if it exists, might be observed in the most sensitive indicators of genetic thermal history, the labile trace elements. We report RNAA data for the concentrations of 14 trace elements, mostly labile ones, (Ag, Au, Bi, Cd, Cs, Co, Ga, In, Rb, Sb, Se, Te, Tl, and Zn) in H4-6 ordinary chondrites. Variance of elemental concentrations within a subpopulation, the members of a proposed co-orbital meteorite stream for example, could be expected to be smaller than the variance for the entire population. We utilize multivariate linear regression and logistic regression statistical techniques as tools for discriminant analysis. A randomization-simulation technique can also be used to make distribution-independent comparisons and to verify that any observed differences are not due to insufficient samples or too many independent variables (Lipschutz and Samuels, 1991). These methods allow us to test for the existence of distinct compositional subpopulations in what is supposedly a single meteorite population. At the time of writing this abstract our database consists of 55 H4-6 chondrites (Lingner et al, 1987 and this work). Nine of these meteorites are members of the proposed "cluster 1" co-orbital meteoroid stream. For these 9 samples, linear discriminant analysis based on the concentrations of 10 labile trace elements reveals a difference between the "cluster 1" subpopulation of H chondrite falls and all other H chondrite falls at the <0.03 significance level. Logistic regression reveals a difference at the <0.0001 significance level. Normalization of data to Allende standard meteorite reference standard to eliminate bias conceivably due to different analysts yields results comparable to results from the non-normalized data. Additional evidence for the absence of interanalyst bias is provided by data of samples from Victoria Land, Antarctica: random populations analyzed by the present authors (Wolf and Lipschutz, 1992) are statistically indistinguishable from populations analyzed previously (Dennison and Lipschutz, 1987). A logistic regression validation run also supports the lack of interanalyst bias. Results from linear discriminant analysis, and logistic regression randomization-simulations will be presented in Copenhagen. These results on a limited population, which may be expanded by meeting time demonstrate that the "cluster 1" subpopulation of H chondrite falls are distinguishable from all other H chondrite falls on the basis of their labile trace elements, a result that is consistent with the idea that these meteorites had a common thermal history and were assoc

  12. Oxygen Isotope Compositions of the Kaidun Meteorite - Indications for Aqeuous Alteration of E-Chondrites

    NASA Technical Reports Server (NTRS)

    Ziegler, K.; Zolensky, M.; Young, E. D.; Ivanov, A.

    2012-01-01

    The Kaidun microbreccia is a unique meteorite due to the diversity of its constituent clasts. Fragments of various types of carbonaceous (CI, CM, CV, CR), enstatite (EH, EL), and ordinary chondrites, basaltic achondrites, and impact melt products have been described, and also several unknown clasts [1, and references therein]. The small mm-sized clasts represent material from different places and times in the early solar system, involving a large variety of parent bodies [2]; meteorites are of key importance to the study of the origin and evolution of the solar system, and Kaidun is a collection of a range of bodies evidently representing samples from across the asteroid belt. The parent-body on which Kaidun was assembled is believed to be a C-type asteroid, and 1-Ceres and the martian moon Phobos have been proposed [1-4]. Both carbonaceous (most oxidized) and enstatite (most reduced) chondrite clasts in Kaidun show signs of aqueous alterations that vary in type and degree and are most likely of pre-Kaidun origin [1, 4].

  13. Santa Lucia (2008) (L6) Chondrite, a Recent Fall: Composition, Noble Gases, Nitrogen and Cosmic Ray Exposure Age

    NASA Astrophysics Data System (ADS)

    Mahajan, Ramakant R.; Varela, Maria Eugenia; Joron, Jean Louis

    2015-11-01

    The Santa Lucia (2008)—one the most recent Argentine meteorite fall, fell in San Juan province, Argentina, on 23 January 2008. Several masses (total ~6 kg) were recovered. Most are totally covered by fusion crust. The exposed interior is of light-grey colour. Chemical data [olivine (Fa24.4) and low-Ca pyroxene (En77.8 Fs20.7 Wo1.6)] indicate that Santa Luica (2008) is a member of the low iron L chondrite group, corresponding to the equilibrated petrologic type 6. The meteorite name was approved by the Nomenclature Committee (NomCom) of the Meteoritical Society (Meteoritic Bulletin, no. 97). We report about the chemical composition of the major mineral phases, its bulk trace element abundance, its noble gas and nitrogen data. The cosmic ray exposure age based on cosmogenic 3He, 21Ne, and 38Ar around 20 Ma is comparable to one peak of L chondrites. The radiogenic K-Ar age of 2.96 Ga, while the young U, Th-He are of 1.2 Ga indicates that Santa Lucia (2008) lost radiogenic 4He more recently. Low cosmogenic (22Ne/21Ne)c and absence of solar wind noble gases are consistent with irradiation in a large body. Heavy noble gases (Ar/Kr/Xe) indicated trapped gases similar to ordinary chondrites. Krypton and neon indicates irradiation in large body, implying large pre-atmospheric meteoroid.

  14. 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.

  15. Olivine and Pyroxene Compositions in Fine-Grained Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Frank, D.

    2011-01-01

    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 olivine 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 olivine with the available chondrite matrix olivine 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 olivine 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.

  16. Reanalysis of porous chondritic cosmic dust particles

    NASA Astrophysics Data System (ADS)

    Kapisinsky, I.; Figusch, V.; Ivan, J.; Izdinsky, K.; Zemankova, M.

    2001-10-01

    The particles reanalysed in this study were obtained from the NASA Johnson Space Center (JSC) Cosmic Dust Collection. The reanalysis of the particle L2008 P9 indicates typical assemblage of olivine - pyroxene. This sample can be classified as a chondritic porous IDP with the metallic phase grain containing essential amount of nickel and copper (the latter element is most probably due to instrumental artefact). The chemical composition of the particle L2011 S5 corresponds mostly to an assemblage of pyroxene phase - (Mg,Fe,Ni)SiO_3 roughly 75 wt.% and a sulphide phase - probably pyrrhotite (Fe,Ni)S about 25 wt.%.

  17. ACFER 182 and paired samples, an iron-rich carbonaceous chondrite - Similarities with ALH85085 and relationship to CR chondrites

    NASA Astrophysics Data System (ADS)

    Bischoff, A.; Palme, H.; Schultz, L.; Weber, D.; Weber, H. W.; Spettel, B.

    1993-06-01

    Data are presented on the minerology, chemical composition, and rare gas composition of three paired meteorite samples of a new Fe-rich chondrite found in the Sahara in 1990 and 1991 (Acfer 182, Acfer 207, and Acfer 214), designated as meteorite Acfer 182. The major components of Acfer 182 are (in decreasing order of abundance): (1) highly altered matrix, (2) mineral and polymineralic silicate fragments and aggregates, (3) chondrule fragments, (4) chondrules, (5) metal, and (6) fine-grained dark inclusions. The chemical composition of Acfer 182 was found to be almost indistinguishable from that of ALH85085. Considering their affinity to carbonaceous chondrites and their high bulk iron content, Acfer 182 and ALH85085 are designated as CH chondrites. Their relation to other groups of chondritic meteorites, such as CR chondrites, is discussed.

  18. Evidence for differences in the thermal histories of Antarctic and non-Antarctic H chondrites with cosmic-ray exposure ages less than 20 Ma

    NASA Technical Reports Server (NTRS)

    Sears, Derek W. G.; Benoit, Paul; Batchelor, J. David

    1991-01-01

    Antarctic H chondrites show a different range of induced thermoluminescence properties compared with those of H chondrites that have fallen elsewhere in the world. Recent noble gas data of Schultz et al. (1991) show that this difference is displayed most dramatically by meteorites with cosmic-ray exposure ages less than 20 Ma, and they confirm that the differences cannot be attributed to weathering or to the presence of a great many fragments of an unusual Antarctic meteorite. Annealing experiments on an H5 chondrite, and other measurements on a variety of ordinary chondrites, have shown that induced TL properties are sensitive to the thermal histories of the meteorities. It is concluded that the events(s) that released the less than 20 Ma samples, which are predominantly those with exposure ages of 8 + or - 2 Ma, produced two groups with different thermal histories, one that came to earth several 100,000 years ago and that are currently only found in Antarctica, and one that is currently falling on the earth.

  19. Thermal metamorphism of primitive meteorites. VII - Mineralogy-petrology of heated Murchison /C2/ and alteration of C30 and other chondrites

    NASA Technical Reports Server (NTRS)

    Matza, S. D.; Lipschutz, M. E.

    1978-01-01

    Alterations caused by week-long heating of Murchison in a low-pressure environment at 400-1400 C are of two types: thermodynamically favored kinetically controlled or thermodynamically controlled rapid processes. Kinetically controlled changes pertinent to chondritic evolution and which vary progressively with temperature in heated Murchison include: chondrule blurring; matrix coarsening; increasing mean Fa and Fs contents of ferromagnesian silicates; equilibration of olivine; increasing Mg/Si, Ca/Si, Al/Si, and Cr/Si and decreasing Fe/Si, Ni/Si, and S/Si in matrix; Cr loss from kamacite; and homogenization and Ni-zoning in taenite at high temperatures. Low-temperature thermodynamically controlled changes include: transformation of high-Ni troilite to low-Ni and formation of Ni- and Co-rich metal from pentlandite. High-temperature changes include formation of Cr-rich magnetite and formation of a Ni-rich sulfide similar to that found in highly altered chondrites. Trends resulting from processes of both kinds in Murchison are consistent with characteristics of a postulated C30 metamorphic suite, while those changes caused by reactions of the second kind are similar to those in heavily shock-heated ordinary chondrites and the heavily metamorphosed C5-6 chondrite, Mulga West. Either the simulations support the metamorphic origin of the C30 suite and other thermally induced changes or the natural alterations support the utility of laboratory simulations in studying meteoritic evolution.

  20. The UThPb age of equilibrated L chondrites and a solution to the excess radiogenic Pb problem in chondrites

    USGS Publications Warehouse

    Unruh, D.M.

    1982-01-01

    U, Th, and Pb analyses of whole-rock and troilite separates from seven L chondrites suggest that the excess radiogenic Pb relative to U and the large variations in PbPb model ages commonly observed in chondritic meteorites are largely due to terrestrial Pb contamination induced prior to analyses. Using the Pb isotopic composition of troilite separates to calculate the isotopic composition of the Pb contaminants, the whole-rock data have been corrected for pre-analysis terrestrial Pb contamination. Two approaches have been used: (1) the chondrite-troilite apparent initial Pb isotopic compositions were used to approximate the mixture of indigenous intial Pb and terrestrial Pb in the whole-rock sample, and (2) a single-stage (concordant) model was applied using the assumption that the excess radiogenic Pb in these samples was terrestrial. Data for L5 and L6 chondrites yield a 4551 ?? 7 My age using the former correction and a 4550 ?? 5 My age using the latter one. Corrected data for one L4 chondrite, Tennasilm, yield a 4552 ?? 13 My age which is indistinguishable from that of the L5-L6 chondrites. However, the other L4 chondrite, Bjurbo??le, yields a 4590 ?? 6 My. ThUPb data suggest that this older age may be an artifact of the correction procedure, and that some of the discordancy of the Bjurbo??le data is the result of either a recent geologic disturbance to the UThPb system or to terrestrial U loss. Some aliquots of the L5L6 chondrites also show small amounts of discordancy (??? 10%) which are not easily attributable to terrestrial Pb contamination. The data from the L5-L6 chondrites and Tennasilm suggest that there are no more than ??? 15 MY differences in the ages of L24-L6 chondrites. ?? 1982.

  1. A Second H Chondrite Stream of Falls

    NASA Astrophysics Data System (ADS)

    Wolf, S. F.; Wang, M.-S.; Dodd, R. T.; Lipschutz, M. E.

    1995-09-01

    Earlier, Dodd et al. [1] described a statistically significant concentration of 17 H4-6 chondrite falls in May between 1855 and 1895, that clustered on a year-day plot, indicating a coorbital meteoroid stream or two closely-related ones. Contents of 10 thermally labile trace elements (Rb, Ag, Se, Cs, Te,Zn, Cd, Bi, Tl, In) determined by RNAA demonstrated that 13 of these H Cluster 1 (hereafter HC1) falls are compositionally distinguishable from another 45 non-H Cluster 1 (non-HC1) falls [1] (as are Antarctic samples with nominal terrestrial ages >50 ky [2,3]). This compositional distinguishability is demonstrable using two standard, model-dependent multivariate statistical tests (linear discriminant analysis LDA or logistic regression LR) or the model-independent, randomization-simulation (R-S) methods of Lipschutz and Samuels [4]. Despite petrographic and cosmic ray exposure age variabilities, like Antarctic suites [2] HC1 meteorites seemingly derive from coorbital meteoroids (from their circumstances of fall) and apparently have a common thermal history (reflected in contents of thermally labile trace elements) distinguishable from those of other H4-6 chondrite falls [1]. Other explanations seem inviable [5]. During days 220-300 when streams of large fireballs [6] and near-Earth asteroids [7] occur several H chondrite concentrations are evident (Fig. 1), particularly if petrographic type becomes a criterion [1]. Here, we focus on H Clusters 2 through 4 (HC2-4) containing, respectively, 10 H4-6, 5 H5 and 12 H6 chondrite members, for which full data sets exist because of the generosity of many colleagues/institutions. H chondrite clusters in the same time-span might include samples derived from related parent regions. Hence, we changed our comparison-base to approximate a random background of falls by including only the 34 non-Cluster H chondrites, HC0; this also simplified our calculations. To establish whether this choice impacts our observations, we compared 13 HC1 with 34 HC0 meteorites (Table 1). As is evident, the LDA, LR and R-S results are nearly identical to those obtained by comparing 13 HC1 with 45 non- HC1 falls [1]. As Table 1 shows, 10 HC2 chondrites are not compositionally distinguishable from 34 HC0 falls by any criterion. However, 12 HC4 falls may be compositionally distinguishable from the HC0 suite using model-dependent LDA and LR techniques. The small HC3 suite seems to lie on an extension of HC4 (Fig. 1) and we compared the 17-member combined suite, HC34, with HC0. Model-dependent or -independent results (Table 1) provide strong evidence for a compositional difference: apparently HC34, like HC1 [1], derive from coorbital meteoroid streams. The oldest and youngest HC34 members are particularly interesting: Borodino fell 5 Sept. 1812 just before the battle there: its fall is unrecorded in military histories of the era [8]. The final orbit of the Peekskill fall in 1992 is particularly well-established [9] linking HC34 to a specific orbit. Acknowledgments: Support from NASA grant NAGW-3396 and DOE grant DE-FG07-80ER1-072SJ. References: [1] Dodd R. T. et al. (1993) JGR, 98, 15105-15118. [2] Michlovich S. et al. (1995) JGR, 100, 3317-3333. [3] Wolf S. F. and Lipschutz M. E. (1995) JGR, 100, 3335-3349. [4] Lipschutz M. E. and Samuels S. M. (1991) GCA, 55, 19-47. [5] Wolf S. F. and Lipschutz M. E. (1995) JGR, 100, 3297-3316. [6] Halliday I. et al. (1990) Meteoritics, 24, 93-99. [7] Drummond J. D. (1991) Icarus, 89, 14-25. [8] Rothenberg G. E., personal communication. [9] Brown P. et al. (1994) Nature, 367, 624-626. Table 1 shows multivariate statistical comparisons of RNAA data for 10 thermally-labile trace elements in various putative suites of H4-6 chondrite falls.

  2. Internal Structure and Mineralogy of Differentiated Asteroids Assuming Chondritic Bulk Composition: The Case of Vesta

    NASA Technical Reports Server (NTRS)

    Toplis, M. J.; Mizzon, H.; Forni, O.; Monnereau, M.; Prettyman, T. H.; McSween, H. Y.; McCoy, T. J.; Mittlefehldt, D. W.; DeSanctis, M. C.; Raymond, C. A.; Russell, C. T.

    2012-01-01

    Bulk composition (including oxygen content) is a primary control on the internal structure and mineralogy of differentiated asteroids. For example, oxidation state will affect core size, as well as Mg# and pyroxene content of the silicate mantle. The Howardite-Eucrite-Diogenite class of meteorites (HED) provide an interesting test-case of this idea, in particular in light of results of the Dawn mission which provide information on the size, density and differentiation state of Vesta, the parent body of the HED's. In this work we explore plausible bulk compositions of Vesta and use mass-balance and geochemical modelling to predict possible internal structures and crust/mantle compositions and mineralogies. Models are constrained to be consistent with known HED samples, but the approach has the potential to extend predictions to thermodynamically plausible rock types that are not necessarily present in the HED collection. Nine chondritic bulk compositions are considered (CI, CV, CO, CM, H, L, LL, EH, EL). For each, relative proportions and densities of the core, mantle, and crust are quantified. Considering that the basaltic crust has the composition of the primitive eucrite Juvinas and assuming that this crust is in thermodynamic equilibrium with the residual mantle, it is possible to calculate how much iron is in metallic form (in the core) and how much in oxidized form (in the mantle and crust) for a given bulk composition. Of the nine bulk compositions tested, solutions corresponding to CI and LL groups predicted a negative metal fraction and were not considered further. Solutions for enstatite chondrites imply significant oxidation relative to the starting materials and these solutions too are considered unlikely. For the remaining bulk compositions, the relative proportion of crust to bulk silicate is typically in the range 15 to 20% corresponding to crustal thicknesses of 15 to 20 km for a porosity-free Vesta-sized body. The mantle is predicted to be largely dominated by olivine (>85%) for carbonaceous chondrites, but to be a roughly equal mixture of olivine and pyroxene for ordinary chondrite precursors. All bulk compositions have a significant core, but the relative proportions of metal and sulphide can be widely different. Using these data, total core size (metal+ sulphide) and average core densities can be calculated, providing a useful reference frame within which to consider geophysical/gravity data of the Dawn mission.

  3. Can Halogen Enrichment in Reduced Enstatite Chondrites Provide Clues to Volatile Accretion in the Early Earth?

    NASA Astrophysics Data System (ADS)

    Clay, P. L.; Burgess, R.; Busemann, H.; Ruzié, L.; Joachim, B.; Ballentine, C.

    2013-12-01

    Understanding how the Earth obtained and ultimately retained its volatiles is important for our overall understanding of large scale planetary evolution. Numerous models exist for the heterogeneous accretion of volatiles to early Earth, but accounting for all elements through accretion of typical planetary building blocks (e.g., CI chondrites) is difficult. Proto-planetary collisions resulting in the accretion of volatile-poor material under reducing conditions followed by accretion of volatile-rich material under oxidizing conditions has been suggested in such models [e.g., 1]. The heavy halogens (Cl, Br and I), a group of moderately volatile elements, are excellent tracers of planetary processing due to their low abundance and incompatible nature. Therefore characterizing halogen abundance and distribution in materials that accreted to form the planets, e.g., primitive meteorites, is crucial. One group of primitive meteorites, the enstatite chondrites (EC's), are amongst the most reduced materials in the solar system as evidenced by their unique mineral assemblage. Yet despite forming under ultra-reducing conditions, they are enriched in the moderately volatile elements, such as the halogens. The ECs are of particular interest owing to their oxygen isotopic composition which plots along the terrestrial fractionation line, linking them isotopically to the Earth-Moon system. These samples can thus potentially provide clues on the accretion of moderately volatile element rich material under reducing conditions, such as it may have existed during the early stages of Earth's accretion. Chlorine, Br and I concentrations in ECs were determined through step-heating small neutron-irradiated samples (0.3 to 3.3 mg) and measured by mass spectrometry using the noble gas proxy isotopes 38ArCl/Cl, 80KrBr/Br and 128XeI/I. The EH chondrites are consistently enriched in the heavy halogens (up to 330 ppm Cl, 2290 ppb Br and 180 ppb I), compared to other ordinary and carbonaceous chondrites measured and have high molar I/Cl (~10-3) and Br/Cl (~10-3) ratios. For comparison, the ordinary chondrites have highly variable halogen concentrations and very low molar I/Cl (~10-6) and Br/Cl (~10-4) ratios. Halogen concentrations in the ECs are up to ~ 8 times higher for Cl, up to ~ 40 times higher for Br and up to ~ 50 times higher for I, when compared to estimates of halogen concentrations in the primitive mantle [2]. Potential halogen carrier phases in the ECs include Cl-rich feldspathic glass in chondrules, enstatite and/or the halogen-bearing sulfide djerfisherite. Accretion of halogen-rich, reduced material such as that observed here with the ECs could support models for heterogeneous accretion. Ongoing analyses of the primitive enstatite achondrites will shed additional light on these issues. [1] Wänke, H. Dreibus, G., Jagoutz E., Archaean Geochemistry, A. Kröner, G. N. Hanson, A. M. Goodwin, Eds. (Springer, Berlin, 1984), pp. 1-24. [2] Newsom, H.E., 1995. Global Earth Physics, A Handbook of Physical Constants, AGU Reference Shelf, vol. 1. American Geophysical Union, Washington.

  4. Resonant Problems for Ordinary Dierential Equations

    E-print Network

    De Nápoli, Pablo Luis

    was obtained by D.E. Leach and A. Lazer in [15] Theorem 1.2 Consider the second order ordinary dierential on the existence of so- lutions for resonant problems. In the literature, they are known as Landesman- Lazer type- tems of second order ordinary dierential equations. In [21] some Landesman- Lazer conditions

  5. MACSYMA's symbolic ordinary differential equation solver

    NASA Technical Reports Server (NTRS)

    Golden, J. P.

    1977-01-01

    The MACSYMA's symbolic ordinary differential equation solver ODE2 is described. The code for this routine is delineated, which is of interest because it is written in top-level MACSYMA language, and may serve as a good example of programming in that language. Other symbolic ordinary differential equation solvers are mentioned.

  6. Origins and Distribution of Chondritic Olivine Inferred from Wild 2 and Chondrite Matrix

    NASA Technical Reports Server (NTRS)

    Frank, D. R.; Zolensky, M. E.

    2014-01-01

    To date, only 180 particle impact tracks from Wild 2 have been extracted from the Stardust aerogel collector and even fewer have been thoroughly characterized. In order to provide a cohesive compositional dataset that can be compared to the meteorite record, we have made both major and minor element analyses (TEM/EDXS) of olivine and low-Ca pyroxene for 39 particles harvested from 26 tracks. However, the dearth of equivalent analyses for these phases in chondrite matrix hinders their comparison to the Wild 2 samples. To properly permit comparison of chondritic olivine and pyroxene to the Wild 2 samples, we have also provided a large, comprehensive EPMA dataset (greater than10(exp 3) analyses) of analogous grains (5-30 micrometers) isolated in L/LL3.0-4, CI, CM, CR, CH, CO, CV, Acfer 094, EH3, EL6, and Kakangari matrix

  7. Carbonaceous chondrites and the origin of life

    NASA Technical Reports Server (NTRS)

    Hartman, Hyman; Sweeney, Michael A.; Kropp, Michael A.; Lewis, John S.

    1993-01-01

    Organic matter in carbonaceous chondrites can be separated into three fractions. The first component, the fraction that is insoluble in chloroform and methanol, has a part which is of interstellar origin. The other two fractions (chloroform-soluble hydrocarbons and methanol-soluble polar organics) are hypothesized to have been synthesized on a planetoid body. We propose that the polar organics, i.e., amino acids, were synthesized close to its surface by the radiolysis of hydrocarbons and ammonium carbonate in a liquid water environment. Some hydrocarbons may have been synthesized by a Fischer-Tropsch mechanism in the interior of the body. Ferrous ion acted as a protection against back reactions. The simultaneous synthesis of iron-rich clays with the polar organics may be indicative of events related to the origin of life on Earth.

  8. Organic analysis of the Antarctic carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Kotra, R. K.; Shimoyama, A.; Ponnamperuma, C.; Hare, P. E.; Yanai, K.

    1981-01-01

    Thus far, organic analysis of carbonaceous chondrites has proven the only fruitful means of examining complex organic matter of extraterrestrial origin. The present paper presents the results of organic analysis of two Antarctic meteorites, Allan Hills (77306) and Yamato (74662), which may be considered free from terrestrial contamination. Ion-exchange chromatography, gas chromatography and mass spectrometery of meteorite samples reveal the presence in Yamato of 15 and in Allan Hills of 20 protein and nonprotein amino acids, the most abundant of which are glycine and alanine. Abundances of the D and L enantiomers of each amino acid are also found to be nearly equal. Data thus indicate an abiotic extraterrestrial origin for the matter, and confirm a lack of terrestrial contamination.

  9. Diamond thermoluminescence properties of different chondrites

    NASA Technical Reports Server (NTRS)

    Fisenko, A. V.; Kashkarov, L. L.; Semjonova, L. F.; Pillinger, C. T.

    1993-01-01

    It was found that thermoluminescence (TL) glows of diamonds depend on the origin of diamonds and the chondrite metamorphism degree. The investigation of TL of diamonds was continued and the results for diamonds from Murchison CM2, Krymka LL3.0, Kainsaz CO3, and Abee E4 were considered. The diamonds synthesized by CVD-process (samples 133, 159) and by detonation from soot (DDS-B14-89) were also analyzed for comparison. Before the TL measuring samples were annealed at approximately 350 C for a few seconds and then irradiated by gamma-rays of Cs-137 up to dose approximately 200 krad. TL-measurements were performed in the air atmosphere on the standard equipment. TL data for samples are shown. TL glow for some diamonds are also presented.

  10. Trace element geochemistry of CR chondrite metal

    NASA Astrophysics Data System (ADS)

    Jacquet, Emmanuel; Paulhiac-Pison, Marine; Alard, Olivier; Kearsley, Anton T.; Gounelle, Matthieu

    2013-10-01

    We report trace element analyses by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of metal grains from nine different CR chondrites, distinguishing grains from chondrule interior ("interior grains"), chondrule surficial shells ("margin grains"), and the matrix ("isolated grains"). Save for a few anomalous grains, Ni-normalized trace element patterns are similar for all three petrographic settings, with largely unfractionated refractory siderophile elements and depleted volatile Au, Cu, Ag, S. All three types of grains are interpreted to derive from a common precursor approximated by the least-melted, fine-grained objects in CR chondrites. This also excludes recondensation of metal vapor as the origin of the bulk of margin grains. The metal precursors were presumably formed by incomplete condensation, with evidence for high-temperature isolation of refractory platinum-group-element (PGE)-rich condensates before mixing with lower temperature PGE-depleted condensates. The rounded shape of the Ni-rich, interior grains shows that they were molten and that they equilibrated with silicates upon slow cooling (1-100 K h-1), largely by oxidation/evaporation of Fe, hence their high Pd content, for example. We propose that Ni-poorer, amoeboid margin grains, often included in the pyroxene-rich periphery common to type I chondrules, result from less intense processing of a rim accreted onto the chondrule subsequent to the melting event recorded by the interior grains. This means either that there were two separate heating events, which formed olivine/interior grains and pyroxene/margin grains, respectively, between which dust was accreted around the chondrule, or that there was a single high-temperature event, of which the chondrule margin records a late "quenching phase," in which case dust accreted onto chondrules while they were molten. In the latter case, high dust concentrations in the chondrule-forming region (at least three orders of magnitude above minimum mass solar nebula models) are indicated.

  11. A Cautionary Tale About Volatile-Rich Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Britt, D. T.; Beltran, E.

    2015-07-01

    The organic component of volatile-rich carbonaceous chondrite meteorites are primarily in the form of polycyclic aromatic hydrocarbons (PAHs). While PAHs are common in the environment, many species of PAHs are either toxic or carcinogenic or both.

  12. Near Infrared Opposition Surge of Carbonaceous Chondrite Meteorites

    NASA Astrophysics Data System (ADS)

    Kawakami, K.; Nakamura, A. M.

    2007-03-01

    We measured the opposition surge of carbonaceous chondrite meteorites with changing particle size and degree of surface compaction, and we compared these data with reflectance phase curve of C-type asteroid, Mathilde.

  13. Application of the sphalerite cosmobarometer to the enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Kissin, S. A.

    1989-07-01

    Thirteen enstatite chondrites and two aubrites were examined for the presence of sphalerite, which was found and analyzed in four of these samples, including ALHA77295, Qingzhen (EH3), Pillistfer (EL6), and Indarch (EH4). The analyses of these sphalerites allow the application of the sphalerite cosmobarometer to the enstatite chondrites. Assuming nebular conditions and zero pressure, the blocking temperatures for the diffusion of iron, T(B), and the cooling rates for these meteorites were calculated. Differences in iron content were found in sphalerites from EH3, EH4, and EL6, considered to be related to differences in their thermal histories. Results indicate that the EH4 chondrite has cooled at an extremely rapid rate and has an unreasonably high T(B). Data for the EL6 chondrites were consistent with relatively slow cooling ca. 773 K, whereupon rapid cooling occurred.

  14. Thermomagnetic analysis of meteorites, 2. C2 chondrites

    USGS Publications Warehouse

    Watson, D.E.; Larson, E.E.; Herndon, J.M.; Rowe, M.W.

    1975-01-01

    Samples of all eighteen of the known C2 chondrites have been analyzed thermomagnetically. For eleven of these, initial Fe3O4 content is low (generally <1%) and theJs-T curves are irreversible. The heating curves show variable greater (up to 10 times) than it is initially. This behavior is attributed to the production of magnetite from a thermally unstable phase - apparently FeS. Four of the remaining seven C2 chondrites contain Fe3O4 as the only significant magnetic phase: initial magnetite contents range from 4 to 13%. The remaining three C2 chondrites contain iron or nickel-iron in addition to Fe3O4. These seven C2 chondrites show little evidence of the breakdown of a thermally unstable phase. ?? 1975.

  15. Evolution of carbonaceous chondrite parent bodies: Insights into cometary nuclei

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1989-01-01

    It is thought that cometary samples will comprise the most primitive materials that are able to be sampled. Although parent body alteration of such samples would not necessarily detract from scientists' interest in them, the possibility exists that modification processes may have affected cometary nuclei. Inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. Observations suggest that, of all the classes of chondrites, these meteorites are most applicable to the study of comets. If the proportion of possible internal heat sources such as Al-26 in cometary materials are similar to those in chondrites, and if the time scale of comet accretion was fast enough to permit incorporation of live radionuclides, comets might have had early thermal histories somewhat like those of carbonaceous chondrite parent bodies.

  16. Space Weathering on Primitive Asteroids: Ion Irradiation of Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Lantz, C.; Brunetto, R.; Barucci, M. A.

    2015-11-01

    We simulate space weathering processes on primitive bodies using ion implantation as a simulation of solar wind irradiation. The laboratory analogs we irradiate and analyze with visible to mid-infrared spectroscopy are carbonaceous chondrites.

  17. Heterogeneous Aqueous Alteration in the CR2 Chondrite Renazzo

    NASA Astrophysics Data System (ADS)

    Jilly, C. E.; Huss, G. R.

    2012-03-01

    We examine the aqueous alteration of CR2 chondrites and report on phosphates, sulfides, and other phases present in Renazzo. Various styles of alteration present in close proximity may suggest localized variations in conditions on the CR parent body.

  18. Ruthenium Isotopic Composition of Terrestrial Materials, Iron Meteorites and Chondrites

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2002-01-01

    Ru isotopic compositions of magmatic iron meteorites and chondrites overlap with terrestrial Ru at the 0.3 to 0.9 (epsilon) level. Additional information is contained in the original extended abstract.

  19. Thulium anomalies and rare earth element patterns in meteorites and Earth: Nebular fractionation and the nugget effect

    E-print Network

    Dauphas, N

    2015-01-01

    This study reports the bulk rare earth element (REEs, La-Lu) compositions of 41 chondrites, including 32 falls and 9 finds from carbonaceous (CI, CM, CO and CV), enstatite (EH and EL) and ordinary (H, L and LL) groups, as well as 2 enstatite achondrites (aubrite). The CI-chondrite-normalized REE patterns and Eu anomalies in ordinary and enstatite chondrites show more scatter in more metamorphosed than in unequilibrated chondrites. This is due to parent-body redistribution of the REEs in various carrier phases during metamorphism. The dispersion in REE patterns of equilibrated ordinary chondrites is explained by the nugget effect associated with concentration of REEs in minor phosphate grains. Terrestrial rocks and samples from ordinary and enstatite chondrites display negative Tm anomalies of ~-4.5 % relative to ca chondrites. In contrast, CM, CO and CV (except Allende) show no significant Tm anomalies. Allende CV chondrite shows large excess Tm (~+10 %). These anomalies are similar to those found in group II...

  20. Volatilization-fractionation of silicates related to chondrite composition

    NASA Technical Reports Server (NTRS)

    Walter, L. S.

    1987-01-01

    The compositions of chondritic meteorites are linked to the solar composition. It is believed that the chemistry of the (generally) drop-shaped chondrules which comprise a large portion of these meteorites may present valuable clues to their formation and, ultimately, to the early conditions and processes of the planets. The purpose of this experiment is to determine the nature of volatilization-fractionation of silicate (and related metallic) compositions related to chondrite composition.

  1. Origin of magnetite and pyrrhotite in carbonaceous chondrites

    USGS Publications Warehouse

    Herndon, J.M.; Rowe, M.W.; Larson, E.E.; Watson, D.E.

    1975-01-01

    CARBONACEOUS chondrites, although comprising only about 2% of known meteorites, are extremely interesting for scientific investigation. Their mineral constitution, and the correspondence between their bulk chemical composition and the solar abundance of condensable elements, indicate that minimum chemical fractionation and thermal alteration have occurred. The mineral phases observed in these primitive chondrites are sufficiently unique, with respect to other meteorite classes, to have elicited considerable speculation about the physical environment in which they formed1-7. ?? 1975 Nature Publishing Group.

  2. Variations among chondrite groups: Constraints on nebular processes

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Love, S. G.; Hutcheon, I. D.

    1994-01-01

    Diverse proportions of the four major ingredients are found in the 13 chondrite groups. Ca-Al-rich inclusions (CAI) include amoeboid-olivine aggregates, which contain refractory nodules. Matrix material forms aggregates and rims on other constituents and contains micrometer-sized grains and a small, uniform concentration of presolar grains. Fe, Ni grains are mostly derived from hot chondrules. Although bulk nonvolatile chondritic elemental ratios are typically within 30% of solar values, individual CAI and some chondrules shown large deviations.

  3. 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.

  4. Refractory solids in chondrites and comets: How similar

    NASA Technical Reports Server (NTRS)

    Wood, John A.

    1989-01-01

    The grains of ice, dust, and organic material that came together to form the solar system have been preserved to differing degrees in the most primitive solar system bodies, asteroids and comets. The study of samples of asteroids (in the form of chondritic meteorites) reveals that the dust component was extensively altered by high-temperature events and processes in the early solar system, before it was aggregated into chondritic planetesimals. The nature of these high-temperature events and processes is not known, but the evidence of their operation is pervasive and unequivocal. Are the refractory particles in comets likely to be similar to these chondrite components. Probably not (except for the presolar carbonaceous grains in chondrites), because the chondritic components are products of severe thermal processing, and all imaginable energy sources that could have provided the heat tend to diminish with distance from the sun. Every indication is that comets formed at much greater radial distances than asteroids, so the particles they incorporated would have experienced less heating. The possibilities cannot be completely ruled out that comets, too, formed inside the present orbit of Jupiter, or that thermally-processed grains were able to diffuse great radial distances before being incorporated in accreting objects, but it is far more likely that most of the refractory grains in comets have been spared the extreme thermal processing that shaped the character of chondritic components.

  5. Salts in two chondritic porous interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.

    1990-01-01

    Grain-by-grain analytical electron microscope analyses of two micrometeorites, or interplanetary dust particles (IDPs) of the chondritic porous subtype show the presence of rare barite (BaSO4) and magnesium carbonate, probably magnesite. Salt minerals in chondritic porous (CP) IDPs give evidence for in situ aqueous alteration in their parent bodies. The uniquely high barium content of CP IDP W7029(asterisk)C1 is consistent with barite precipitation from a mildly acidic (pH above 5) aqueous fluid at temperatures below 417 K and low oxygen fugacity. The presence of magnesite in olivine-rich, anhydrous CP IDP W7010(asterisk)A2 is evidence that carbonate minerals occur in both the chondritic porous and chondritic smooth subtypes of chondritic IDPs. Citing Schramm et al. (1989) for putative asteroidal-type aqueous alteration in IDPs and probable sources of chondritic IDPs, salt minerals in CP IDPs could support low-temperature aqueous activity in nuclei of active short-period comets.

  6. Analysis of chondritic interplanetary dust thin-sections

    SciTech Connect

    Bradley, J.P. )

    1988-04-01

    Chondritic interplanetary dust particles (IDPs) are heterogeneous aggregates of predominantly submicrometer mineral grains and carbonaceous material, whose bulk compositions agree within a factor of two with type CI/CM carbonaceous chondrites. The mineralogy and petrography of 25 such particles were studied by analytical electron microscopic examination of ultramicrotomed thin-sections (500-1,000 {angstrom} thick). Four classes of chondritic IDPs were recognized, referred to as pyroxene, olivine, smectite, and serpentine, and their relative abundances were 9:4:10:2 respectively. Pyroxene and olivine particles are porous assemblages of anhydrous mineral grains, glass, and carbonaceous material. Smectite and serpentine particles are low porosity objects whose matrices contain layer silicates and glassy material. Quantitative thin-film analyses indicate that pyroxene particles most closely resemble material emitted from comet Halley. Smectite particles may have formed from pyroxene particles by aqueous alteration of glass and enstatite crystals. Serpentine particles are the only class that are similar to the matrices of carbonaceous chondrites, but these are the least abundant chondritic IDPs. Collectively, chondritic particles are a mineralogically diverse group of extraterrestrial materials.

  7. Correlated Petrologic and Geochemical Characteristics of CO3 Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1998-01-01

    Many properties of CO3 chondrites have been shown previously to have resulted from thermal metamorphism; petrologic subtypes 3.0-3.7 have been assigned to members of the group. Additional properties that correlate with the metamorphic sequence but seem to have resulted from hydrothermal alteration include the modal abundance of amoeboid olivine inclusions (AOI), chondrule size, the types of refractory inclusions and whole rock O isotopic composition. The percentage of rimmed AOI increases with petrologic subtype. The rims most likely formed during hydrothermal alteration. The previously reported correlation between AOI abundance and chondrite subtype is probably an artifact due to the difficulty in recognizing small unrimmed AOI in the least metamorphosed CO3 chondrites. Because large (>=200 micron size) porphyritic chondrules have nearly the same mean size in all CO3 chondrites, it seems likely that the correlation between chondrule size and subtype is due to alteration of the smallest chondrules to the point of unrecognizability as complete objects in the more metamorphosed CO3 chondrites. The previously reported decrease in the proportion of melilite-rich refractory inclusions with increasing petrologic subtype may have resulted from more extensive hydrothermal alteration in CO3 .4-3.7 chondrites that converted primary melilite into Ca-pyroxene, andradite and nepheline. Alteration probably caused the preferential occurrence of O-16-poor oxygen isotopes in the more metamorphosed whole rock samples.

  8. Ordinary Stoichiometry of Extraordinary Microbes

    NASA Astrophysics Data System (ADS)

    Neveu, M.; Poret-Peterson, A. T.; Anbar, A. D.; Elser, J. J.

    2013-12-01

    Life on Earth seems to be composed of the same chemical elements in relatively conserved stoichiometric proportions. However, this observation is largely based on observations of biota from habitats spanning a moderate range of temperature and chemical composition (e.g., temperate lakes, forests, grasslands, oceanic phytoplankton). Whether this stoichiometry is conserved in settings that differ radically from such "normal" planetary settings may provide insight into the habitability of environments with radically different stoichiometries, and into possible stoichiometries for putative life beyond Earth. Here we report the first measurements of elemental stoichiometries of microbial extremophiles from hot springs of Yellowstone National Park (YNP). These phototrophic and chemotrophic microbes were collected in locations spanning large ranges of temperature (ambient to boiling) and pH (1 to 9). Microbial biomass was carefully extracted from hot spring sediment substrata following a procedure adapted from [1], which conserves cellular elemental abundances [2]. Their C and N contents were determined by Elemental Analysis Isotope Ratio Mass Spectrometry, and their P and trace element (Mg, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and non-biogenic Al and Ti) contents were measured by Inductively Coupled Plasma Mass Spectrometry. Residual mineral contamination was an issue in some samples with low measured C and N; we eliminated these from our results. Even in the remaining samples, contamination sometimes prevented accurate determinations of cellular Mg, Ca, Mn, and Fe abundances; however, the cellular Ni, Cu, Zn, and Mo contents were several-fold above contamination level. Although hot spring water and sediment elemental abundances varied by orders of magnitude, the data showed that the extremophiles have a major and trace element stoichiometry similar to those previously measured in "normal" microbial biomass [3-6]. For example, biomass C:N:P ratios resembled those commonly observed in temperate lakes (e.g., C:P ratios of 260 to 1600 and N:P ratios of 35 to 200) while cellular C:Fe ratios were of a similar magnitude to those of marine phytoplankton. Exceptions were Al and Ti, much higher than previously measured, likely because of contamination from residual sediment. Moreover, the low phosphorus contents (high C:P and N:P ratios) are suggestive of limited P supply. Chemotrophs and phototrophs had similar elemental compositions to one another, although Mg, Mn, Ni, and Zn abundances were higher and nearly constant in phototrophs, due to their importance in phototrophic metabolism. Despite the tremendous physical and chemical diversity of YNP environments, the stoichiometry of life in these settings is surprisingly ordinary. Thus, our study supports the view that the biological stoichiometry of life is heavily constrained by the elemental composition of core biomolecules, and that even life in extreme environments must operate within these constraints. In the frame of life detection in exotic locales, these results suggest a general elemental biosignature for life as we know it. References: [1] Amalfitano and Fazi. 2008. J. Microbiol. Meth. 75:237 [2] Neveu et al. L&O: Meth., in review [3] Ho et al. 2003. J. Phycol. 39:1145 [4] Nuester et al. 2012. Front. Microbiol. 3:150 [5] Sterner and Elser. 2002. Ecological Stoichiometry. Princeton U. Press [6] Twining et al. 2011. Deep-Sea Res. II 58:325

  9. Parameter estimation in ordinary differential equations 

    E-print Network

    Ng, Chee Loong

    2004-09-30

    The parameter estimation problem or the inverse problem of ordinary differential equations is prevalent in many process models in chemistry, molecular biology, control system design and many other engineering applications. It concerns the re...

  10. Fire Classifications Fires involving the ordinary

    E-print Network

    Jia, Songtao

    Fire Classifications Fires involving the ordinary combustible materials such as wood, cloth, paper, plastics, etc. Fires involving combustible or flammable liquids such as gasoline, kerosene, oils, grease, paints and chemicals. Fires involving energized electrical equipment such as appliances, including

  11. Terrestrial microbes in martian and chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Airieau, S.; Picenco, Y.; Andersen, G.

    2007-08-01

    Introduction: The best extraterrestrial analogs for microbiology are meteorites. The chemistry and mineralogy of Asteroid Belt and martian (SNC) meteorites are used as tracers of processes that took place in the early solar system. Meteoritic falls, in particular those of carbonaceous chondrites, are regarded as pristine samples of planetesimal evolution as these rocks are primitive and mostly unprocessed since the formation of the solar system 4.56 billion years ago. Yet, questions about terrestrial contamination and its effects on the meteoritic isotopic, chemical and mineral characteristics often arise. Meteorites are hosts to biological activity as soon as they are in contact with the terrestrial biosphere, like all rocks. A wide biodiversity was found in 21 chondrites and 8 martian stones, and was investigated with cell culture, microscopy techniques, PCR, and LAL photoluminetry. Some preliminary results are presented here. The sample suite included carbonaceous chondrites of types CR, CV, CK, CO, CI, and CM, from ANSMET and Falls. Past studies documented the alteration of meteorites by weathering and biological activity [1]-[4]. Unpublished observations during aqueous extraction for oxygen isotopic analysis [5], noted the formation of biofilms in water in a matter of days. In order to address the potential modification of meteoritic isotopic and chemical signatures, the culture of microbial contaminating species was initiated in 2005, and after a prolonged incubation, some of the species obtained from cell culture were analyzed in 2006. The results are preliminary, and a systematic catalog of microbial contaminants is developing very slowly due to lack of funding. Methods: The primary method was cell culture and PCR. Chondrites. Chondritic meteorite fragments were obtained by breaking stones of approximately one gram in sterile mortars. The core of the rocks, presumably less contaminated than the surface, was used for the present microbial study, and the remaining fragments of the samples were used for amino acid and isotopic analyses [6]. Some samples were fragments of dried and wet meteorites isolated in centrifuge tubes after a 10-day water extraction. Sabouraud Dextrose (dilutions 1:10 and 1:1000), Bacto Agar, LB Broth Miller (dilutions 1:10 and 1:1000), and R2A agar (1:1 and 1:1000), were autoclaved and cooled in culture plates inside a clean hood for cell culture. Some controls retained sterile moist agar still adhering to the perimeter of the plates for up to 18 months, and validated the sterile technique. Cell culture, PCR and microscopy documented a diversity of archea, prokaryotes and eukaryotes in these samples [7]. The plates displaying microbial growth at room temperature after 6 weeks or less were used to produce streak plates and isolate colonies of individual species for long term freezing in Eppendorf tubes. Any plate with biological growth along the perimeter of the plate was discarded. The plates without microbial activity after 6 weeks were stored in a fridge for 18 months. Control plates, exposed to the clean hood, laboratory room, used gloves, and weighing paper used in the analyses, sustained the prolonged storage with no sign of microbial activity that could be related to the analysis method. Dust grains and water extracts from the meteorites were spread on agar surfaces in cell culture Petri dishes in a clean hood. SNC samples.In early 2005, the surface of SNC stones in the USNM curation facility were brushed with sterile swabs. Fallen dust grains were collected on weighing paper and isolated in sterile tubes. The sample suite included Zagami USNM 6545, Lafayette USNM 1505, Los Angeles USNM 7052, Shergotty USNM 321, Nakhla USNM 5892, Nakhla USNM 426 (117.4 g) and Nakhla USNM 426 (18.2 g), and Chassigny USNMMNHN 2524. The controls, worker's gloves, blank swabs, and weighing paper exhibited no microbial activity in subsequent months. The cell culture was conducted with Sabouraud Dextrose and R2A only, by deposition of dry grains onto the surface of agar in culture plates that were incubated a

  12. High-precision Mg isotopic systematics of bulk chondrites

    NASA Astrophysics Data System (ADS)

    Schiller, Martin; Handler, Monica R.; Baker, Joel A.

    2010-08-01

    Variations of the mass-independent abundance of 26Mg ( ?26Mg*) and stable Mg ( ?25Mg) isotope composition of chondrites are important because they constrain the homogeneity of 26Al and Mg isotopes in the proto-planetary disc and the validity of the short-lived 26Al-to- 26Mg chronometer applied to meteorites. We present high-precision Mg isotope data and Al/Mg ratios of chondrites representing nearly all major chondrite classes, including a step-leaching experiment on the CM2 chondrite Murchison. ?26Mg* variations in leachates of Murchison representing acid soluble material are ? 30 times smaller than reported for neutron-rich isotopes of Ti and Cr and do not reveal resolvable deficits in ?26Mg* (-0.002 to + 0.118‰). Very small variations in ?26Mg* anomalies in bulk chondrites (-0.006 to + 0.019‰) correlate with increasing 27Al/ 24Mg ratios and ?50Ti, reflecting the variable presence of calcium-aluminium-rich inclusions (CAIs) in some types of carbonaceous chondrites. Similarly, release of radiogenic 26Mg produced by 26Al decay from CAI material in the step-leaching of Murchison best explains the high ?26Mg* observed in the last, aggressive, leaching steps of this experiment. Overall, the observed variations in ?26Mg* are small and potential differences beyond that which result from the presence of CAI-like material cannot be detected within the analytical uncertainties of this study (± 0.004‰). The results do not allow radical heterogeneity of 26Al (?±30%) or measurable Mg nucleosynthetic heterogeneity (?±0.005‰) to have existed on a planetesimal scale in the proto-planetary disc. Combined with published ?26Mg* data for CAIs, the bulk chondrite data yield a precise initial ( 26Al/ 27Al) 0 = (5.21 ± 0.06) × 10 -5 and ?26Mg* = -0.0340 ± 0.0016‰ for the Solar System. However, it is not possible with the currently available data to determine with certainty whether CAIs and the material from which planetesimals accreted including chondrite parent bodies had precisely the same initial levels of 26Al, although planetesimals and planets appear to have accreted from material with a mean initial ( 26Al/ 27Al) 0 in the range of 2.1 to 6.7 × 10 - 5 . The average stable Mg isotope composition of all analysed chondrites, with the exception of a chondrule from the CBa chondrite Gujba ( ?25Mg DSM-3 = -0.032 ± 0.035‰), is ?25Mg DSM-3 = -0.152 ± 0.079‰ (2 sd) and is indistinguishable from that of the Earth's mantle.

  13. 31 CFR 29.525 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Ordinary and necessary living expenses. 29.525...Waivers of Collection Standards for Waiver of Overpayments... Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include...

  14. 31 CFR 29.525 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Ordinary and necessary living expenses. 29.525...Waivers of Collection Standards for Waiver of Overpayments... Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include...

  15. 5 CFR 845.305 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Ordinary and necessary living expenses. 845.305...SYSTEM-DEBT COLLECTION Standards for Waiver of Overpayments... Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include...

  16. 5 CFR 845.305 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Ordinary and necessary living expenses. 845.305...SYSTEM-DEBT COLLECTION Standards for Waiver of Overpayments... Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include...

  17. 7 CFR 28.426 - Strict Good Ordinary Spotted Color.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 false Strict Good Ordinary Spotted Color. 28.426 Section 28.426 Agriculture...Cotton § 28.426 Strict Good Ordinary Spotted Color. Strict Good Ordinary Spotted Color is color which is within the range...

  18. 7 CFR 28.426 - Strict Good Ordinary Spotted Color.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 false Strict Good Ordinary Spotted Color. 28.426 Section 28.426 Agriculture...Cotton § 28.426 Strict Good Ordinary Spotted Color. Strict Good Ordinary Spotted Color is color which is within the range...

  19. 7 CFR 28.426 - Strict Good Ordinary Spotted Color.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 false Strict Good Ordinary Spotted Color. 28.426 Section 28.426 Agriculture...Cotton § 28.426 Strict Good Ordinary Spotted Color. Strict Good Ordinary Spotted Color is color which is within the range...

  20. 7 CFR 28.426 - Strict Good Ordinary Spotted Color.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 false Strict Good Ordinary Spotted Color. 28.426 Section 28.426 Agriculture...Cotton § 28.426 Strict Good Ordinary Spotted Color. Strict Good Ordinary Spotted Color is color which is within the range...

  1. Amoeboid olivine aggregates from CH carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; Park, Changkun; Nagashima, Kazuhide

    2014-08-01

    Amoeboid olivine 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 ?17O = -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 ?17O values, from -24‰ to -13‰. Melilite, grossite, and hibonite in four CAIs within AOAs show no evidence for radiogenic 26Mg excess (?26Mg). In contrast, anorthite in five out of six AOAs measured has ?26Mg 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 ?26Mg 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 ?26Mg 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 chondrules and Fe,Ni-metal grains in CH and CB carbonaceous chondrites about 5 Myr after formation of CV CAIs.

  2. Distinct Purine Distribution in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Smith, Karen E.; Cleaves, Henderson J.; Ruzicka, Josef; Stern, Jennifer C.; Glavin, Daniel P.; House, Christopher H.; Dworkin, Jason P.

    2011-01-01

    Carbonaceous chondrite meteorites are known to contain a diverse suite of organic compounds, many of which are essential components of biochemistry. Amino acids, which are the monomers of proteins, have been extensively studied in such meteorites (e.g. Botta and Bada 2002; Pizzarello et aI., 2006). The origin of amino acids in meteorites has been firmly established as extraterrestrial based on their detection typically as racemic mixtures of amino acids, the presence of many non-protein amino acids, and non-terrestrial values for compound-specific deuterium, carbon, and nitrogen isotopic measurements. In contrast to amino acids, nucleobases in meteorites have been far less studied. Nucleobases are substituted one-ring (pyrimidine) or two-ring (purine) nitrogen heterocyclic compounds and serve as the information carriers of nucleic acids and in numerous coenzymes. All of the purines (adenine, guanine, hypoxanthine, and xanthine) and pyrimidines (uracil) previously reported in meteorites are biologically common and could be interpreted as the result of terrestrial contamination (e.g. van del' Velden and Schwartz, 1974.) Unlike other meteoritic organics, there have been no observations of stochastic molecular diversity of purines and pyrimidines in meteorites, which has been a criterion for establishing extraterrestrial origin. Maltins et al. (2008) performed compound-specific stable carbon isotope measurements for uracil and xanthine in the Murchison meteorite. They assigned a non-terrestrial origin for these nucleobases; however, the possibility that interfering indigenous molecules (e.g. carboxylic acids) contributed to the 13C-enriched isotope values for these nucleobases cannot be completely ruled out. Thus, the origin of these meteoritic nucleobases has never been established unequivocally. Here we report on our investigation of extracts of II different carbonaceous chondrites covering various petrographic types (Cl, CM, and CR) and degrees of aqueous alteration (l, 2, and 3) and one ureilite. Analysis via liquid chromatography coupled with electrospray triple-stage mass spectrometry or orbitrap mass spectrometry employed a targeted approach for analysis focused on the five canonical RNA/DNA nucleobases as well as 14 non-canonical pyrimidines and purines, which have bcen observed under plausible prebiotic reactions.

  3. Is the Chondritic Earth model still viable? (Invited)

    NASA Astrophysics Data System (ADS)

    Sharma, M.

    2009-12-01

    Following the discovery by Boyet and Carlson in 2005 that the terrestrial 142Nd\\144Nd ratio is about 20 ? units higher than chondrites, papers with four different ideas explaining the observed difference have appeared in the literature. The first idea is that there is an early differentiated hidden reservoir on earth (Boyet & Carlson, 2005, 2006; Andreasen & Sharma, 2006, 2007; Andreasen et al., 2008; Carlson & Boyet, 2008). The second idea is that the solar nebula was isotopically heterogeneous (Ranen and Jacobsen, 2006). The third idea explains the isotope ratio difference as resulting from fractionation between Sm and Nd during condensation of solid materials from a nebula with higher Sm/Nd ratio (Allegre et al., 2008). The fourth idea suggests large-scale rare earth element fractionation following nebular condensation and possibly during the planetary accretionary phase (O’Neill & Palme, 2008; Warren, 2008). This last idea has gained currency as it has been argued that Mars is non-chondritic Sm/Nd ratio (Bourdon et al., 2008; Caro et al, 2008) and therefore the Earth-Moon system is also non-chondritic. All above scenarios, except for the first one imply a non-chondritic earth and therefore change the fundamental benchmark parameters against which we have been assessing the sense and magnitude of terrestrial evolution over thirty years. Is this really needed? How can we test some of the non-chondritic scenarios? If not, should we be seriously considering them even if they appear to be aesthetically appealing? In this paper I will review each of these scenarios and demonstrate why a chondritic earth model still remains attractive and provides testable explanations of the observed excess of 142Nd in terrestrial upper mantle over chondrites.

  4. Spade: An H Chondrite Impact-melt Breccia that Experienced Post-shock Annealing

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Jones, Rhian H.

    2006-01-01

    The low modal abundances of relict chondrules (1.8 Vol%) and of coarse (i.e. >= 2200 micron-size) isolated mafic silicate grains (1.8 Vol%) in Spade relative to mean H6 chondrites (11.4 and 9.8 vol%, respectively) show Spade to be a rock that has experienced a significant degree of melting. Various petrographic features (e.g., chromite-plagioclase assemblages, chromite veinlets, silicate darkening) indicate that melting was caused by shock. Plagioclase was melted during the shock event and flowed so that it partially to completely surrounded nearby mafic silicate grains. During crystallization, plagioclase developed igneous zoning. Low-Ca pyroxene that crystallized from the melt (or equilibrated with the melt at high temperatures) acquired relatively high amounts of CaO. Metallic Fe-Ni cooled rapidly below the Fe-Ni solws and transformed into martensite. Subsequent reheating of the rock caused transformation of martensite into abundant duplex plessite. Ambiguities exist in the shock stage assignment of Spade. The extensive silicate darkening, the occurrence of chromite-plagioclase assemblages, and the impact-melted characteristics of Spade are consistent with shock stage S6. Low shock (stage S2) is indicated by the undulose extinction and lack of planar fractures in olivine. This suggests that Spade reached a maximum prior shock level equivalent to stage S6 and then experienced post-shock annealing (probably to stage Sl). These events were followed by a less intense impact that produced the undulose extinction in the olivine, characteristic of shock stage S2. Annealing could have occurred if Spade were emplaced near impact melts beneath the crater floor or deposited in close proximity to hot debris within an ejecta blanket. Spade firmly establishes the case for post-shock annealing. This may have been a common process on ordinary chondrites (OC) asteroids.

  5. Application of an alkylammonium method for characterization of phyllosilicates in CI chondrites

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Ming, D. W.; Zolensky, M. E.; Yang, S. V.

    1994-01-01

    Many meteorites and interplanetary dust particles (IDP's) with primitive compositions contain significant amounts of phyllosilicates, which are generally interpreted as evidence of protoplanetary aqueous alteration at an early period in the solar system. These meteorites are chondrites of the carbonaceous and ordinary varieties. Characterization of phyllosilicates in these materials is important because of the important physico-chemical information they hold, e.g., from well characterized phyllosilicates, thermodynamic stability relations and hence the conditions of formation of phyllosilicates in the parent body of the meteorite can be predicted. Although we are at a rudimentary level of understanding of the minerals resulting from the aqueous alteration in the early solar nebula, we know that the most common phyllosilicates present in chondritic extraterrestrial materials are serpentines, smectites, chlorites, and micas. The characterization of fine grained minerals in meteorites and IDP's rely heavily on electron beam instruments, especially transmission electron microscopy (TEM). Typically, phyllosilicates are identified by a combination of high resolution imaging of basal spacings, electron diffraction analysis, and chemical analysis. Smectites can be difficult to differentiate from micas because the smectites loose their interlayer water and the interlayers collapse to the same basal spacing as mica in the high vacuum of the TEM. In high-resolution TEM (HRTEM) images, smectite basal spacings vary from 1 nm up to 1.5 nm, while micas show 1 or 2 nm basal spacings. Not only is it difficult to differentiate smectites from micas, but there is no way of identifying different classes of smectites in meteorites and IDP's. To differentiate smectites from micas and also to recognize the charge differences among smectites, an alkylammonium method can be employed because the basal spacings of alkylammonium saturated smectites expand as a function of alkylamine chain length and the layer-charge density of the 2:1 expanding phyllosilicate, and the final product is significantly more stable under electron beam examination. Such a method was tested on standard clays and several meteorite samples using four alkylammonium salts.

  6. The origin of the neon isotopes in chondrites and on Earth

    NASA Astrophysics Data System (ADS)

    Moreira, Manuel; Charnoz, Sébastien

    2016-01-01

    We discuss the origin of the neon isotopic signatures in chondrites and in the terrestrial mantle. There are two primary possible origins for neon in the Earth's mantle. One origin is the dissolution of a dense primordial atmosphere with a solar composition of 20Ne/22Ne >13.4 into the mantle in a possible magma ocean stage during Earth's accretion. The second origin, developed in this study, is that mantle neon was already in Earth's parent bodies because of refractory grain irradiation by solar wind. We propose that solar wind implantation occurred early on dust within the accretion disk to allow such irradiation. Because solar wind implantation fractionates neon isotopes, the heavier isotopes are implanted deeper than the lighter ones because of different kinetic energies, and the process of implantation, if coupled with sputtering, leads to a steady state neon isotopic ratio (20Ne/22Ne ?12.7) that is similar to what is observed in mantle-derived rocks (12.5-12.9), lunar soil grains (?12.9) and certain gas-rich chondrites from all classes (enstatite, ordinary, rumuruti). Using a dust transport model in a turbulent and irradiated solar nebula, we estimated the equivalent irradiation age of a population of dust particles at three different distances from the sun (0.8, 1, 1.2 AU) and converted these ages into neon concentrations and isotopic ratios. The dust subsequently coagulated to form Earth's parent bodies, which have the mean neon isotopic composition of the irradiated dust (non-irradiated dust is assumed to be free of neon). If this scenario of solar wind implantation coupled with sputtering in the precursors of Earth's parent bodies is correct, it offers a simple alternative to the model of solar nebula gas incorporation by dissolution in a magma ocean.

  7. Extinct I-129 in C3 chondrites

    NASA Technical Reports Server (NTRS)

    Crabb, J.; Lewis, R. S.; Anders, E.

    1982-01-01

    Eight C3 chondrites were examined by the I-129 to Xe-129 dating method to determine whether their initial I-129/I-127 ratios, or R(0), correlate with any other properties. The R(0)'s range from 1.60 x 10 to the -4th to 1.09 x 10 to the -4th, corresponding to I to Xe ages from 2.0 Myr before to 6.7 Myr after the Murchison magnetite. Three C30's have essentially indistinguishable R(0)'s, while a fourth is undatable. Four C3V's show a distinct spread, ranging from 1.60 + or 0.07 x 10 to the -4th to 1.09 + or - 0.10 x 10 to the -4th. These R(0)'s correlate inversely with four other properties: I, Br, and Cd content, olivine composition, both percent mean deviation, and proportion of iron-poor olivine grains. The simplest model that accounts for the correlations with R(0) involves mixing of two iodine components in the solar nebula, associated with gas and grains, respectively. The second, of lower I-129/I-127 ratio, predominated at later times and thus became enriched in late-formed meteorites.

  8. Northwest Africa 428: Impact-induced Annealing of an L6 Chondrite Breccia

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    Northwest Africa (NWA) 428 is an L chondrite that was successively thermally metamorphosed to petrologic type-6, shocked to stage S4-S5, brecciated, and annealed to approximately petrologic type-4. Its thermal and shock history resembles that of the previously studied LL6 chondrite, Miller Range (MIL) 99301, which formed on a different asteroid. The petrologic type-6 classification of NWA 428 is based on its highly recrystallized texture, coarse metal (150 +/- 150 micron), troilite (100 +/- 170 micron), and plagioclase (20-60 micron) grains, and relatively homogeneous olivine (Fa(sub 24.4 +/- 0.6)), low-Ca pyroxene (FS(sub 2.5+/- 0,4) , and plagioclase (Ab(sub 84.2 +/- 0.4) compositions. The petrographic criteria that indicate shock stage S4-S5 include the presence of chromite veinlets, chromite-plagioclase assemblages, numerous occurrences of metallic Cu, irregular troilite grains within metallic Fe-Ni, polycrystalline troilite, duplex plessite, metal and troilite veins, large troilite nodules, and low-Ca clinopyroxene with polysynthetic twins. If the rock had been shocked before thermal metamorphism, low-Ca clinopyroxene produced by the shock event would have transformed into orthopyroxene. Post-shock brecciation is indicated by the presence of recrystallized clasts and highly shocked clasts that form sharp boundaries with the host. Post-shock annealing is indicated by the sharp optical extinction of the olivine grains; during annealing, the damaged olivine crystal lattices healed. If temperatures exceeded those approximating petrologic type-4 (approximately 600-700 C) during annealing, the low-Ca clinopyroxene would have transformed into orthopyroxene. The other shock indicators, likewise, survived the mild annealing. An impact event is the most plausible source of post-metamorphic, post-shock annealing because any A1-26 that may have been present when the asteroid accreted would have decayed away by the time NWA 428 was annealed. The similar inferred histories of NWA 428 (L6) and MIL 99301 (LL6) indicate that impact heating affected more than 1 ordinary chondrite parent body.

  9. Petrology and In Situ Trace Element Chemistry of a Suite of R Chondrites

    NASA Astrophysics Data System (ADS)

    Mittlefehldt, D. W.; Peng, Z. X.; Torrano, Z. A.

    2015-07-01

    Your eyes are not deceiving you: Duck has submitted an abstract to a chondrite session. We will present the results of our petrological and compositional studies of R chondrites of diverse petrological type.

  10. Consortium study of the unusual H chondrite regolith breccia, Noblesville

    NASA Technical Reports Server (NTRS)

    Lipschutz, Michael E.; Wolf, Stephen F.; Vogt, Stephan; Michlovich, Edward; Lindstrom, Marilyn M.; Zolensky, Michael E.; Mittlefehldt, David W.; Satterwhite, Cecilia; Schultz, Ludolf; Loeken, Thomas

    1993-01-01

    The Noblesville meteorite is a genomict, regolith breccia (H6 clasts in H4 matrix). Moessbauer analysis confirms that Noblesville is unusually fresh, not surprising in view of its recovery immediately after its fall. It resembles 'normal' H4-6 chondrites in its chemical composition and induced thermoluminescence (TL) levels. Thus, at least in its contents of volatile trace elements, Noblesville differs from other H chondrite, class A regolith breccias. Noblesville's small pre-atmospheric mass and fall near solar maximum and/or its peculiar orbit (with perihelion less than 0.8 AU as shown by natural TL intensity) may partly explain its levels of cosmogenic radionuclides. Its cosmic ray exposure age of about 44 Ma is long, is equalled or exceeded by less than 3 percent of all H chondrites, and also differs from the 33 +/- 3 Ma mean exposure age peak of other H chondrite regolith breccias. While Noblesville is now among the chondritic regolithic breccias richest in solar gases, elemental ratios indicate some loss, especially of He, perhaps by impacts in the regolith that heated individual grains. While general shock-loading levels in Noblesville did not exceed 4 GPa, individual clasts record shock levels of 5-10 GPa, doubtless acquired prior to lithification of the whole-rock meteoroid.

  11. Magnetic evidence for a partially differentiated carbonaceous chondrite parent body

    PubMed Central

    Carporzen, Laurent; Weiss, Benjamin P.; Elkins-Tanton, Linda T.; Shuster, David L.; Ebel, Denton; Gattacceca, Jérôme

    2011-01-01

    The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. As a result, the paleomagnetism of the CV carbonaceous chondrite Allende, most of which was acquired after accretion of the parent body, has been a long-standing mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Resolution of this conundrum requires a determination of the age and timescale over which Allende acquired its magnetization. Here, we report that Allende’s magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a >  ? 20 ?T field up to approximately 9—10 Ma after solar system formation. This field was present too recently and directionally stable for too long to have been generated by the protoplanetary disk or young Sun. The field intensity is in the range expected for planetesimal core dynamos, suggesting that CV chondrites are derived from the outer, unmelted layer of a partially differentiated body with a convecting metallic core.

  12. Evidence for Extended Aqueous Alteration in CR Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Trigo-Rodriquez, J. M.; Moyano-Cambero, C. E.; Mestres, N.; Fraxedas, J.; Zolensky, M.; Nakamura, T.; Martins, Z.

    2013-01-01

    We are currently studying the chemical interrelationships between the main rockforming components of carbonaceous chondrites (hereafter CC), e.g. silicate chondrules, refractory inclusions and metal grains, and the surrounding meteorite matrices. It is thought that the fine-grained materials that form CC matrices are representing samples of relatively unprocessed protoplanetary disk materials [1-3]. In fact, modern non-destructive analytical techniques have shown that CC matrices host a large diversity of stellar grains from many distinguishable stellar sources [4]. Aqueous alteration has played a role in homogeneizing the isotopic content that allows the identification of presolar grains [5]. On the other hand, detailed analytical techniques have found that the aqueously-altered CR, CM and CI chondrite groups contain matrices in which the organic matter has experienced significant processing concomitant to the formation of clays and other minerals. In this sense, clays have been found to be directly associated with complex organics [6, 7]. CR chondrites are particularly relevant in this context as this chondrite group contains abundant metal grains in the interstitial matrix, and inside glassy silicate chondrules. It is important because CR are known for exhibiting a large complexity of organic compounds [8-10], and only metallic Fe is considered essential in Fischer-Tropsch catalysis of organics [11-13]. Therefore, CR chondrites can be considered primitive materials capable to provide clues on the role played by aqueous alteration in the chemical evolution of their parent asteroids.

  13. Primitive Fine-Grained Matrix in the Unequilbrated Enstatite Chondrites

    NASA Technical Reports Server (NTRS)

    Weisberg, M. K.; Zolensky, M. E.; Kimura, M.; Ebel, D. S.

    2014-01-01

    Enstatite chondrites (EC) have important implications for constraining conditions in the early solar system and for understanding the evolution of the Earth and other inner planets. They are among the most reduced solar system materials as reflected in their mineral compositions and assemblage. They are the only chondrites with oxygen as well as Cr, Ti, Ni and Zn stable isotope compositions similar to the earth and moon and most are completely dry, lacking any evidence of hydrous alteration; the only exception are EC clasts in the Kaidun breccia which have hydrous minerals. Thus, ECs likely formed within the snow line and are good candidates to be building blocks of the inner planets. Our goals are to provide a more detailed characterization the fine-grained matrix in E3 chondrites, understand its origin and relationship to chondrules, decipher the relationship between EH and EL chondrites and compare E3 matrix to matrices in C and O chondrites as well as other fine-grained solar system materials. Is E3 matrix the dust remaining from chondrule formation or a product of parent body processing or both?

  14. Chemical fractionations in meteorites. XI - C2 chondrites

    NASA Technical Reports Server (NTRS)

    Wolf, R.; Richter, G. R.; Woodrow, A. B.; Anders, E.

    1980-01-01

    Measurements of the compositions of 20 trace elements in the representative C2 chondrites Boriskino, Cold Bokkeveld, Erakot, Essebi, Haripura, Santa Cruz and Al Rais are reported. The contents of Ag, Au, Bi, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn were determined by radiochemical neutron activation analysis. The siderophile abundances of the C2 chondrites are found to be less uniform than those of other carbonaceous chondrites, while the C2R chondrite Al Rais is systematically lower in 12 volatiles than the C2M chondrites. Enrichment of Bi and Tl found in Erakot and Haripura indicate the possible presence of the late condensate mysterite. Volatile abundances are shown to agree with matrix contents for meteorites that have suffered little aqueous alteration, however to be 20-30% lower for the more altered meteorites. Finally, the decline of element abundance with volatility is shown to be consistent with the sigmoid curve explained by the two-component model.

  15. Collisional erosion and the non-chondritic composition of the terrestrial planets

    E-print Network

    Mcdonough, William F.

    Collisional erosion and the non-chondritic composition of the terrestrial planets BY HUGH ST. C. O¨lpicherstrasse 49b, 50674 Ko¨ln, Germany The compositional variations among the chondrites inform us about in oxidation state. Moon- to Mars-sized planetary bodies, formed by rapid accretion of chondrite

  16. Organic Analysis of Catalytic Fischer-Tropsch Type Synthesis Products: Are they Similar to Organics in Chondritic Meteorites?

    NASA Technical Reports Server (NTRS)

    Yazzie, Cyriah A.; Locke, Darren R.; Johnson, Natasha M.

    2014-01-01

    Fischer-Tropsch Type (FTT) synthesis of organic compounds has been hypothesized to occur in the early solar nebula that formed our Solar System. FTT is a collection of abiotic chemical reactions that convert a mixture of carbon monoxide and hydrogen over nano-catalysts into hydrocarbons and other more complex aromatic compounds. We hypothesized that FTT can generate similar organic compounds as those seen in chondritic meteorites; fragments of asteroids that are characteristic of the early solar system. Specific goals for this project included: 1) determining the effects of different FTT catalyst, reaction temperature, and cycles on organic compounds produced, 2) imaging of organic coatings found on the catalyst, and 3) comparison of organic compounds produced experimentally by FTT synthesis and those found in the ordinary chondrite LL5 Chelyabinsk meteorite. We used Pyrolysis Gas Chromatography Mass Spectrometry (PY-GCMS) to release organic compounds present in experimental FTT and meteorite samples, and Scanning Electron Microscopy (SEM) to take images of organic films on catalyst grains.

  17. Composition of Potentially Hazardous Asteroid (214869) 2007 PA8: An H Chondrite from the Outer Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Sanchez, Juan A.; Reddy, Vishnu; Dykhuis, Melissa; Lindsay, Sean; Le Corre, Lucille

    2015-07-01

    Potentially hazardous asteroids (PHAs) represent a unique opportunity for physical characterization during their close approaches to Earth. The proximity of these asteroids makes them accessible for sample-return and manned missions, but could also represent a risk for life on Earth in the event of collision. Therefore, a detailed mineralogical analysis is a key component in planning future exploration missions and developing appropriate mitigation strategies. In this study we present near-infrared spectra (˜0.7-2.55 ?m) of PHA (214869) 2007 PA8 obtained with the NASA Infrared Telescope Facility during its close approach to Earth on 2012 November. The mineralogical analysis of this asteroid revealed a surface composition consistent with H ordinary chondrites. In particular, we found that the olivine and pyroxene chemistries of 2007 PA8 are Fa18(Fo82) and Fs16, respectively. The olivine-pyroxene abundance ratio was estimated to be 47%. This low olivine abundance and the measured band parameters, close to the H4 and H5 chondrites, suggest that the parent body of 2007 PA8 experienced thermal metamorphism before being catastrophically disrupted. Based on the compositional affinity, proximity to the J5:2 resonance, and estimated flux of resonant objects we determined that the Koronis family is the most likely source region for 2007 PA8.

  18. Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

    NASA Technical Reports Server (NTRS)

    Tatsunori, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2015-01-01

    Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

  19. Are C1 chondrites chemically fractionated - A trace element study

    NASA Astrophysics Data System (ADS)

    Ebihara, M.; Wolf, R.; Anders, E.

    1982-10-01

    Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for a large variety of elements, including rare earths. The sample processing is described, including the irradiation, chemical procedure, rare earths separation, counting techniques, radiochemical purity check, and chemical yields. The results of consistency checks on a number of elements are discussed. Abundances for siderophiles, volatiles, and rare earths are presented and discussed. Tests are presented for fractionation of rare earths and other refractories, compositional uniformity of C1's, and interelement correlations. There is no conclusive evidence for nebular fractionation affecting C1's. Three fractionation-prone rare earths have essentially the same relative abundances in C1's and all other chondrite classes, and hence are apparently not fractionated in C1's.

  20. Chondritic Meteorites: Nebular and Parent-Body Formation Process

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    1997-01-01

    Chondritic meteorites are the products of condensation, agglomeration and accretion of material in the solar nebula; these objects are the best sources of information regarding processes occurring during the early history of the solar system. We obtain large amounts of high-quality chemical and petrographic data and use them to infer chemical fractionation processes that occurred in the solar nebula and on meteorite parent bodies during thermal metamorphism, shock metamorphism and aqueous alteration. We compare diverse groups of chondrites and model their different properties in terms of processes that differed at different nebular locations or on different parent-bodies. In order to expand our set of geochemically important elements (particularly Si, C, P and S) and to distinguish the different oxidation states of Fe, Greg Kallemeyn spent three months (1 Sept. - 30 Nov. 1995) at the Smithsonian Institution to learn Eugene Jarosewich's wet chemical techniques. Key specimens from the recently established CK, CR and R chondrite groups were analyzed.

  1. A Weathering Index for CK and R Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Huber, Heinz

    2006-01-01

    We present a new weathering index (wi) for the metallic-Fe-Ni-poor chondrite groups (CK and R) based mainly on transmitted light observations of the modal abundance of crystalline material that is stained brown in thin sections: wi-0, <5 vol%; wi-1, 5-25 vol%; wi-2,25-50 vol%; wi-3,50- 75 vol%; wi-4, 75-95 vol%; wi-5, >95 vol%, wi-6, significant replacement of mafic silicates by phyllosilicates. Brown staining reflects mobilization of oxidized iron derived mainly from terrestrial weathering of Ni-bearing sulfide. With increasing degrees of terrestrial weathering of CK and R chondrites, the sulfide modal abundance decreases, and S, Se, and Ni become increasingly depleted. In addition, bulk Cl increases in Antarctic CK chondrites, probably due to contamination from airborne sea mist.

  2. Gas flow and fluidization in a thick dynamic regolith: A new mechanism for the formation of chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Huang, Shaoxiong; Sears, Derek W. G.

    1995-01-01

    We have previously shown that size and density sorting in a regolith which has been 'fluidized' by the passage or gases from the interior or the body can quantitatively explain metal-silicate fractionation, an important property of ordinary chondrites. Here we discuss whether the flow rates and flux or volatiles expected from a primitive parent body are likely to be sufficient for this mechanism. Many meteorite parent bodies may have contained volatiles. From a consideration of heat diffusion and fluid mechanics, we calculate the gas flow rate of volatiles (e.g., water) in the regolith of an asteroid-sized object heated by Al-26. Our calculations show that the flow velocities and flux of water vapor are sufficient to produce conditions suitable for fluidization. Other heat sources have yet to be considered, but literature work suggests that they may be equally effective.

  3. Petrology of Two Itokawa Particles: Comparison with Equilibrated LL Chondrites

    NASA Technical Reports Server (NTRS)

    Komatsu, M.; Mikouchi, T.; Arai, T.; Fagan, T. J.; Zolensky, M.; Hagiya, K.; Ohsumi, K.; Karouji, Y.

    2015-01-01

    A strong link between Itokawa particles and LL chondrites was confirmed by preliminary examinations of Hayabusa particles [e.g., 1, 2]. Both poorly equilibrated and highly equilibrated particles have been found among the grains returned from Itokawa [1], and it is suggested that they correspond to LL4 and LL5-6, respectively. Here we report the petrography of two Itokawa particles and TEM study of one, and compare them to Antarctic LL chondrites with variable petrologic types (LL4-LL7) in order to understand the metamorphic history of asteroid Itokawa.

  4. Hydrated interplanetary dust particle linked with carbonaceous chondrites?

    NASA Technical Reports Server (NTRS)

    Tomeoka, K.; Buseck, P. R.

    1985-01-01

    The results of transmission electron microscope observations of a hydrated interplanetary dust particle (IDP) containing Fe-, Mg-rich smectite or mica as a major phase are reported. The sheet silicate appears to have formed by alteration of anhydrous silicates. Fassaite, a Ca, Al clinopyroxene, also occurs in this particle, and one of the crystals exhibits solar-flare tracks, clearly indicating that it is extraterrestrial. Fassaite is a major constituent of the Ca-, Al-rich refractory inclusions found in the carbonaceous chondrites, so its presence in this particle suggests that there may be a link between hydrated IDPs and carbonaceous chondrites in the early history of the solar system.

  5. Identification and characterization of extraterrestrial non-chondritic interplanetary dust

    NASA Technical Reports Server (NTRS)

    Blake, D. F.; Fleming, R. H.

    1991-01-01

    Interplanetary dust particles (IDPs) are among the most pristine and primitive extraterrestrial materials available for direct study. Most of the stratospheric particles selected for study from the JSC Curatorial Collection were chondritic in composition (major element abundances within a factor of two of chondritic meteorites) because this composition virtually ensures that the particle is from an extraterrestrial source. It is likely that some of the most interesting classes of IDP's have not been recognized simply because they are not chondritic or do not fit established criteria for extraterrestrial origin. Indeed, mass spectroscopy data from the Giotto Flyby of comet Halley indicate that a substantial fraction of the dust is in the submicron size range and that a majority of these particles contain C, H, O, and/or N as major elements. The preponderance of CHON particles in the coma of Halley implies that similar particles may exist in the JSC stratospheric dust collection. However, the JSC collection also contains a variety of stratospheric contaminants from terrestrial sources which have these same characteristics. Because established criteria for extraterrestrial origin may not apply to such particles in individual cases, and integrated approach is required in which a variety of analysis techniques are applied to the same particle. Non-chondritic IDP's, like their chondritic counterparts, can be used to elucidate pre- and early solar system processes and conditions. The study of non-chondritic IDP's may additionally yield unique information which bears on the nature of cometary bodies and the processing of carbonaceous and other low atomic number materials. A suite of complementary techniques, including Low Voltage Scanning Electron Microscopy (LVSEM), Energy-Dispersive X-ray Microanalysis (EDX), Secondary Ion Mass Spectrometry (SIMS) isotope-ratio imaging and Analytical Electron Microscopy (AEM), were utilized to accomplish the following two objectives: (1) to develop criteria for the unequivocal identification of extraterrestrial non-chondritic IDP's; and (2) to infer IDP parent body, solar nebula, and pre-solar conditions through the study of phases, textures, and components contained within non-chondritic IDP's. The general approach taken is designed to maximize the total information obtained from each particle. Techniques will be applied in order from least destructive to most destructive.

  6. The metallic microstructures and thermal histories of severely reheated chondrites

    NASA Technical Reports Server (NTRS)

    Smith, B. A.; Goldstein, J. I.

    1977-01-01

    The metallographic structures of eight severely reheated chondrites - Farmington, Ramsdorf, Orvinio, Wickenburg, Lubbock, Rose City, Arapahoe, and Tadjera - were studied using optical, SEM and electron microprobe techniques. The following metallographic criteria were used to estimate the post-shock residual temperature of the chondrites: melted metal-troilite appearance, presence of martensite, phosphorus enrichment of metal and averaging of central metal grain compositions. The presence of phosphides and secondary kamacite are due to slow post-shock cooling rates. Ni rim gradients indicate both extensive remelting of metal grains and relatively fast cooling.

  7. Nitrogen and light noble gases in Parsa enstatite chondrite

    NASA Technical Reports Server (NTRS)

    Murty, S. V. S.

    1993-01-01

    Solar gases have been recently reported in Parsa, an EH3 chondrite. In an effort to check whether solar gases are uniformly distributed throughout Parsa or they are located in specific phases, we analyzed two additional samples of bulk Parsa and one aubritic nodule for N and noble gases. Nitrogen studies are intended for the understanding of the nitrogen components distribution in E-chondrites. The N-systematics of the nodule are entirely different from the bulk samples. The higher N contents in this nodule, as well as its complex delta(sup 15)N structure, as compared to the normal aubrites, is suggestive that the nodule is not a genuine aubrite.

  8. Water and the thermal evolution of carbonaceous chondrite parent bodies

    NASA Technical Reports Server (NTRS)

    Grimm, Robert E.; Mcsween, Harry Y., Jr.

    1989-01-01

    Two hypotheses are proposed for the aqueous alteration of carbonaceous chondrites within their parent bodies, in which respectively the alteration occurs (1) throughout the parent body interior, or (2) in a postaccretional surface regolith; both models assume an initially homogeneous mixture of ice and rock that is heated through the decay of Al-26. Water is seen to exert a powerful influence on chondrite evolution through its role of thermal buffer, permitting substitution of a low temperature aqueous alteration for high temperature recrystallization. It is quantitatively demonstrated that liquid water may be introduced by either hydrothermal circulation, vapor diffusion from below, or venting due to fracture.

  9. Pyroxene structures, cathodoluminescence and the thermal history of the enstatite chondrites

    NASA Technical Reports Server (NTRS)

    Zhang, Yanhong; Huang, Shaoxiong; Schneider, Diann; Benoit, Paul H.; Sears, Derek W. G.; DeHart, John M.; Lofgren, Gary E.

    1996-01-01

    In order to explore the thermal history of enstatite chondrites, we examined the cathodoluminescence (CL) and thermoluminescence (TL) properties of 15 EH chondrites and 21 EL chondrites, including all available petrographic types, both textural types 3-6 and mineralogical types alpha-delta. The CL properties of EL3(alpha) and EH3(alpha) chondrites are similar. Enstatite grains high in Mn and other transition metals display red CL, while enstatite with low concentrations of these elements show blue CL. A few enstatite grains with greater than 5 wt% FeO display no CL. In contrast, the luminescent properties of the metamorphosed EH chondrites are very different from those of metamorphosed EL chondrites. While the enstatites in metamorphosed EH chondrites display predominantly blue CL, the enstatites in metamorphosed EL chondrites display a distinctive magenta CL with blue and red peaks of approximately equal intensity in their spectra. The TL sensitivities of the enstatite chondrites correlate with the intensity of the blue CL and, unlike other meteorite classes, are not simply related to metamorphism. The different luminescent properties of metamorphosed EH and EL chondrites cannot readily be attributed to compositional differences. But x-ray diffraction data suggests that the enstatite in EH5(gamma),(delta) chondrites is predominantly disordered orthopyroxene, while enstatite in EL6(beta) chondrites is predominantly ordered orthopyroxene. The difference in thermal history of metamorphosed EL and EH chondrites is so marked that the use of single 'petrographic' types is misleading, and separate textural and mineralogical types are preferable. Our data confirm earlier suggestions that metamorphosed EH chondrites underwent relatively rapid cooling, and the metamorphosed EL chondrites cooled more slowly and experienced prolonged heating in the orthopyroxene field.

  10. Breakup and structure of an H-chondrite parent body - The H-chondrite flux over the last million years

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Two distinct groups of H chondrites are identified which have respectively induced thermoluminescence peak temperatures above 190 C (AC) and below 190 C (BC). Metallographic cooling rate determinations confirm that the AC group cools at very high rates relative to the latter group. The AC group members have cosmic ray exposure ages of about 8 Myr. Antarctic meteorite of the BC group have cosmic ray exposure ages greater than 20 Myr. Modern H-chondrite falls, which are all of the BC group, have cosmic ray exposure ages of 8 and above 20 Myr. The data show that the abundance of the AC group is directly related to terrestrial age. It is suggested that both the AC group and part of BC group were produced by an impact event at approximately 8 Myr and that the small sizes of the AC group made them prone to destruction, allowing the BC group to dominate the modern H-chondrite flux.

  11. Homeless Young People and Technology: Ordinary

    E-print Network

    Anderson, Richard

    Homeless Young People and Technology: Ordinary Interactions, Extraordinary Circumstances JillWashington|dhendry@uw.edu Homelessness among young people aged 13 to 30 is a pressing problem with lasting social and economic consequences for the U.S. By one estimate, 3 million young people experience homelessness annu- ally; that is

  12. Numerical solution of ordinary differential equations

    E-print Network

    Hairer, Ernst

    numerical meth- ods in use today was formed by Leonhard Euler in 1768. On writing down the first terms´e de Gen`eve and Universit¨at T¨ubingen 1 Introduction: Euler methods Ordinary differential equations, Leibniz, Euler, Lagrange), in chemical re- action kinetics, molecular dynamics, electronic circuits

  13. Yesterday's Extraordinary Research Yields Today's Ordinary Principles

    ERIC Educational Resources Information Center

    Thomas, Mary Norris

    2005-01-01

    Ordinary performance improvement tips, techniques, and principles that are taken for granted today have their roots in extraordinary research. Today, the learning principle that states that things that occur together tend to be recalled together is widely accepted, and this principle of association as an instructional technique is often used. How…

  14. A Unified Introduction to Ordinary Differential Equations

    ERIC Educational Resources Information Center

    Lutzer, Carl V.

    2006-01-01

    This article describes how a presentation from the point of view of differential operators can be used to (partially) unify the myriad techniques in an introductory course in ordinary differential equations by providing students with a powerful, flexible paradigm that extends into (or from) linear algebra. (Contains 1 footnote.)

  15. Numerical Solution of Ordinary Di erential Equations

    E-print Network

    Numerical Solution of Ordinary. Di erential Equations. E. S uli. October 16, 2001 ...... is an example of an explicit linear four-step method; the four-step Adams - Moul- ...... of this result see, for example, Walter Rudin: Real and Complex Analysis.

  16. Major, trace element and oxygen isotope study of glass cosmic spherules of chondritic composition: The record of their source material and atmospheric entry heating

    NASA Astrophysics Data System (ADS)

    Cordier, Carole; Folco, Luigi; Suavet, Clément; Sonzogni, Corinne; Rochette, Pierre

    2011-09-01

    New geochemical data on cosmic spherules (187 major element, 76 trace element, and 10 oxygen isotope compositions) and 273 analyses from the literature were used to assess the chemical diversity observed among glass cosmic spherules with chondritic composition. Three chemical groups of glass spherules are identified: normal chondritic spherules, CAT-like spherules (where CAT refers to Ca-Al-Ti-rich spherules), and high Ca-Al spherules. The transition from normal to high Ca-Al spherules occurs through a progressive enrichment in refractory major elements (on average from 2.3 wt.% to 7.0 wt.% for CaO, 2.8 wt.% to 7.2 wt.% for Al 2O 3, and 0.14 wt.% to 0.31 wt.% for TiO 2) and refractory trace elements (from 6.2 ?g/g to 19.3 ?g/g for Zr and 1.6CI-4.3CI for Rare Earth Elements-REEs) relative to moderately refractory elements (Mg, Si) and volatile elements (Rb, Na, Zn, Pb). Based on a comparison with experimental works from the literature, these chemical groups are thought to record progressive heating and evaporation during atmospheric entry. The evaporative mass losses evaluated for the high Ca-Al group (80-90%) supersede those of the CAT spherules which up to now have been considered as the most heated class of stony cosmic spherules. However, glass cosmic spherules still retain isotopic and elemental evidence of their source and precursor mineralogy. Four out of the 10 normal and high Ca-Al spherules analysed for oxygen isotopes are related to ordinary chondrites ( ?18O = 13.2-17.3‰ and ?17O = 7.6-9.2‰). They are systematically enriched in Ni and Co (Ni = 24-500 ?g/g) with respect to spherules related to carbonaceous chondrites (Ni < 1.2 ?g/g, ?18O = 13.1-28.0‰ and ?17O = 5.1-14.0‰). REE abundances in cosmic spherules, which are not fractionated according to parent body or atmospheric entry heating, can then be used to unravel the precursor mineralogy. Spherules with flat REE pattern close to unity when normalized to CI are the most abundant in our dataset (54%) and likely derive from homogeneous, fine-grained chondritic precursors. Other REE patterns fall into no more than five categories, a surprising reproducibility in view of the mineralogical heterogeneity of chondritic lithologies at the micrometeorite scale.

  17. Large silica-rich igneous-textured inclusions in the Buzzard Coulee chondrite: Condensates, differentiates, or impact melts?

    NASA Astrophysics Data System (ADS)

    Ruzicka, Alex; Hutson, Melinda; Floss, Christine; Hildebrand, Alan

    2012-11-01

    We studied three large (2-4 mm diameter) igneous-textured inclusions in the Buzzard Coulee (H4) chondrite using microanalytical techniques (OLM, SEM, EMPA, SIMS) to better elucidate the origins of igneous inclusions in ordinary chondrites. The inclusions are clasts that come in two varieties (1) white inclusions Bz-1 and Bz-2 represent a nearly holocrystalline assemblage of low-Ca and high-Ca pyroxene (63-66 area%) and cristobalite (33-36%) and (2) tan inclusion Bz-3 is glass-rich (approximately 60%) with low-Ca and high-Ca pyroxene phenocrysts. The bulk compositions of the inclusions determined by modal reconstruction are all SiO2-rich (approximately 67 wt% for Bz-1 and Bz-2, approximately 62% for Bz-3), but Bz-3 is enriched in incompatible elements (e.g., REE approximately 4-5 × CI abundances), whereas Bz-2 and Bz-1 are depleted in those elements that are most incompatible in pyroxene (e.g., La-Ho approximately 0.15-0.4 × CI abundances). These bulk compositions do not resemble what one would expect for partial or complete shock melting of a chondritic precursor, and show no evidence for overall volatility control. We infer that the inclusions originated through igneous differentiation and FeO reduction, with Bz-3 forming as an "andesitic" partial melt (approximately 30-40% partial melting of an H chondrite precursor), and Bz-1 and Bz-2 forming as pyroxene-cristobalite cumulates from an Si-rich melt. We suggest that both types of melts experienced a period of transit through a cold, low-pressure space environment in which cooling, FeO reduction, and interaction with a vapor occurred. Melts may have been lofted into space by excavation or splashing during collisions, or by pyroclastic volcanism. Our results indicate intriguing similarities between the inclusions in Buzzard Coulee and the silicates in some iron (IIE-type) and stony iron (IVA-type) meteorites, suggesting a genetic relationship.

  18. E-chondrites - Significance of the partition of elements between 'silicate' and 'sulphide'

    NASA Astrophysics Data System (ADS)

    Easton, A. J.

    1985-03-01

    Bulk chemical analyses of six E-type chondrites are given. The chondrites include Daniel's kuil, Khairpur, Kota Kota, and Sain Sauveur, together with South Oman, and St. Mark's chondrites. The distribution of lithophile elements between silicate and sulfide mineral groups was measured using selective attack by dry chlorine on magnetically separated fractions. Subdivision of the E-chondrites into types I and II is shown using chemical data for the St. Mark's and Saint Sauveur chondrites. It is found that the Sulphides contributed the largest proportion of elements to the bulk composition; the proportion of Ti contributed to the bulk composition by the sulfides in both chondrite types increased in relation to the intensity of the thermal metamorphic effect. A complete list of the chemical abundances in the chondrites is provided.

  19. Regolith breccia consisting of H and LL chondrite mixture

    NASA Technical Reports Server (NTRS)

    Yanai, Keizo; Kojima, Hideyasu

    1993-01-01

    Antarctic meteorite Yamato-8424 (Y-8424) is a regolith breccia that is homogenized mixture of H and LL chondrite components. The breccia consists mainly of a fine-grained material with mineral fragments of olivine, pyroxene, and Fe-Ni metal with traces of plagioclase.

  20. Organic Carbon Inclusions in CR2 Chondrite Graves Nunataks 95229

    NASA Astrophysics Data System (ADS)

    Peeters, Z.; Changela, H.; Stroud, R. H.; Alexander, C. M. O'D.; Nittler, L. R.

    2012-09-01

    We report coordinated XANES, TEM, and nanoSIMS analysis of two large, carbon-rich veins in CR2 chondrite GRA 95229. The variability in morphological, isotopic, and chemical properties is compared to previous results on C-rich veins in CR3 QUE 99177.

  1. Metastable carbon in two chondritic porous interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.; Mackinnon, Ian D. R.

    1987-01-01

    An understanding of carbonaceous matter in primitive extraterrestrial materials is an essential component of studies on dust evolution in the interstellar medium and the early history of the Solar System. Analytical Electron Microscopy (AEM) on carbonaceous material in two Chondritic Porous (CP) aggregates is presented. The study suggests that a record of hydrocarbon carbonization may also be preserved in these materials.

  2. Metastable carbon in two chondritic porous interplanetary dust particles

    NASA Technical Reports Server (NTRS)

    Rietmeijer, F. J. M.; Mackinnon, I. D. R.

    1986-01-01

    An understanding of carbonaceous matter in primitive extraterrestrial materials is an essential component of studies on dust evolution in the interstellar medium and the early history of the Solar System. Analytical Electron Microscopy (AEM) on carbonaceous material in two Chondritic Porous (CP) aggregrates is presented. The study suggests that a record of hydrocarbon carbonization may also be preserved in these materials.

  3. Chondrites and the Protoplanetary Disk ASP Conference Series, Vol. ###, 2005

    E-print Network

    Connolly Jr, Harold C.

    is still not totally resolved, though heating by shock waves in the protoplanetary disk (e.g., Desch% of the rock (e.g., Zanda 2004; Jones et al. this vol- ume). Chondritic bodies are in turn abundant throughout of microdroplets and dust (Wood 1996), or by melting of rock or of dustballs (e.g., Jones et al. this volume

  4. Establishing a molecular relationship between chondritic and cometary organic solids

    PubMed Central

    Cody, George D.; Heying, Emily; Alexander, Conel M. O.; Nittler, Larry R.; Kilcoyne, A. L. David; Sandford, Scott A.

    2011-01-01

    Multidimensional solid-state NMR spectroscopy is used to refine the identification and abundance determination of functional groups in insoluble organic matter (IOM) isolated from a carbonaceous chondrite (Murchison, CM2). It is shown that IOM is composed primarily of highly substituted single ring aromatics, substituted furan/pyran moieties, highly branched oxygenated aliphatics, and carbonyl groups. A pathway for producing an IOM-like molecular structure through formaldehyde polymerization is proposed and tested experimentally. Solid-state 13C NMR analysis of aqueously altered formaldehyde polymer reveals considerable similarity with chondritic IOM. Carbon X-ray absorption near edge structure spectroscopy of formaldehyde polymer reveals the presence of similar functional groups across certain Comet 81P/Wild 2 organic solids, interplanetary dust particles, and primitive IOM. Variation in functional group concentration amongst these extraterrestrial materials is understood to be a result of various degrees of processing in the parent bodies, in space, during atmospheric entry, etc. These results support the hypothesis that chondritic IOM and cometary refractory organic solids are related chemically and likely were derived from formaldehyde polymer. The fine-scale morphology of formaldehyde polymer produced in the experiment reveals abundant nanospherules that are similar in size and shape to organic nanoglobules that are ubiquitous in primitive chondrites. PMID:21464292

  5. Amino acid analyses of R and CK chondrites

    NASA Astrophysics Data System (ADS)

    Burton, Aaron S.; McLain, Hannah; Glavin, Daniel P.; Elsila, Jamie E.; Davidson, Jemma; Miller, Kelly E.; Andronikov, Alexander V.; Lauretta, Dante; Dworkin, Jason P.

    2015-03-01

    Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon-rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3-6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh-performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino-terminal (n-?-amino) acids ?-alanine, and ?-amino-n-butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n-?-amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer-Tropsch-type reactions, although this hypothesis needs further testing.

  6. Evolution of Carbonaceous Chondrite Parent Bodies: Insights into Cometary Nuclei?

    NASA Astrophysics Data System (ADS)

    McSween, Harry Y., Jr.

    1997-12-01

    Much of the excitement about obtaining cometary samples accrues from the conventional view that they comprise the most primitive materials that we are likely to get our hands on. But is this true? Although "parent body" alteration of such samples would not necessarily detract from this interest, we should keep in mind the possibility that certain kinds of secondary processes may have affected cometary nuclei. Weissman (1986) has proposed some mechanisms by which comet nuclei might be altered, but observational evidence supporting the physical processing of comets is not yet generally available. This paper will take another approach: inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. It seems increasingly unlikely that carbonaceous chondrites are comet nucleus samples. However, these meteorites were probably derived from planetesimals that originally contained ices, though possibly in lesser proportions than comets, so the compositional distinction between carbonaceous chondrite parent bodies and comets may be one of degree. The possibility of an orbital evolution of cometary bodies into asteroidal orbits lias also been suggested. For these reasons, it seems prudent to examine the processes which have affected carbonaceous chondrite parent bodies as possible analogs for the evolutionary history of comets.

  7. Ubiquitous high-FeO silicates in enstatite chondrites

    NASA Technical Reports Server (NTRS)

    Lusby, David; Scott, Edward R. D.; Keil, Klaus

    1987-01-01

    SEM and EMPA were used to determine the mineral contents of four EH3 chondrites. All four showed the dominant enstatite peak, Fs 0-5, with 4-8 percent of FeO-rich pyroxene with Fs 5-20. Among the 542 objects found to contain high-FeO silicates, 18 were chondrules, 381 were rimmed or unrimmed grains, and 143 were aggregates. The high-FeO silicates in these objects are very largely pyroxene with Fs 5-23. Large grains of both FeO-rich and FeO-poor silicates were found to be present in the FeO-rich chondrules. This fact, together with the absence of clasts of FeO-rich chondritic material in the EH3 chondrites, suggests that FeO-rich grains were introduced before or during chondrule formation. It is concluded that FeO-rich and FeO-poor silicates were both present in the nebular region where E chondrites originated.

  8. Amino acids in a carbonaceous chondrite from Antarctica

    NASA Technical Reports Server (NTRS)

    Kotra, R. K.; Shimoyama, A.; Ponnamperuma, C.; Hare, P. E.

    1979-01-01

    A carbonaceous chondrite from the Antarctic, referred to as the Allan Hills meteorite 77306, appears to be free from terrestrial organic contamination. The presence of both protein and non-protein amino acids and an equal abundance of D- and L-enantiomers of amino acids, is testimony to the extraterrestrial nature of these compounds.

  9. CM Carbonaceous Chondrite Lithologies and Their Space Exposure Ages

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Gregory, Timothy; Takenouchi, Atsushi; Nishiizumi, Kunihiko; Trieman, Alan; Berger, Eve; Le, Loan; Fagan, Amy; Velbel, Michael; Imae, Naoya; Yamaguchi, Akira

    2015-01-01

    The CMs are the most commonly falling C chondrites, and therefore may be a major component of C-class asteroids, the targets of several current and future space missions. Previous work [1] has concluded that CM chondrites fall into at least four distinct cosmic ray space exposure (CRE) age groups (0.1 million years, 0.2 million years, 0.6 million years and greater than 2.0 million years), an unusually large number, but the meaning of these groupings is unclear. It is possible that these meteorites came from different parent bodies which broke up at different times, or instead came from the same parent body which underwent multiple break-up events, or a combination of these scenarios, or something else entirely. The objective of this study is to investigate the diversity of lithologies which make up CM chondrites, in order to determine whether the different exposure ages correspond to specific, different CM lithologies, which permit us to constrain the history of the CM parent body(ies). We have already reported significant petrographic differences among CM chondrites [2-4]. We report here our new results.

  10. Kinetics of volatile extraction from carbonaceous chondrites: Dehydration of talc

    NASA Technical Reports Server (NTRS)

    Bose, Kunal; Ganguly, Jibamitra

    1991-01-01

    Carbonaceous chondrites are believed to be the primary constituents of near-Earth asteroids and Phobos and Deimos, and are potential resources of fuels that may be exploited for future planetary missions. Calculations of equilibrium phase relations suggest that talc (Ta) and antigorite (Ant) are likely to be the major hydrous phases in the C1 and C2 meteorites (Ganguly and Saxena, 1989), which constitute the most volatile rich classes of carbonaceous chondrites. The dehydration kinetics of talc are studied as a function of temperature, grain size, composition and fluid fugacity, as part of a systematic study of the reaction kinetics of the volatile bearing phases that are either known or likely to be present in carbonaceous chondrites. The dehydration kinetics were investigated at 1 bar, 775 to 875 C by monitoring the in-situ weight loss as a function of time of a natural talc. The talc platelets had a dimension of 0.8 to 1 micron. The run durations varied from 233.3 hours at 775 C (48 percent dehydration) to 20.8 hours at 875 C (80 pct. dehydration). The results can be adequately represented by a given rate equation. Theoretical analysis suggests that the reduction in the concentration of H2O in the environment of dehydrating talc, as would be encountered in processing chondritic materials, will have negligible effect on the rate of dehydration, unless there is a change of reaction mechanism owing to the presence of other volatile species.

  11. Shock and thermal history of iron and chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Goldstein, Joseph I.

    1994-01-01

    This research grant included a study of the shock and thermal history of iron and chondritic meteorites. The important research findings are to be found in the 20 publications that were published as a result of the research support. A complete bibliographic reference to all these papers is given.

  12. Neodymium Isotope Evidence for a Chondritic Composition of the Moon

    E-print Network

    Neodymium Isotope Evidence for a Chondritic Composition of the Moon K. Rankenburg,1 * A. D. Brandon,1 C. R. Neal2 Samarium-neodymium isotope data for six lunar basalts show that the bulk Moon has this hypothesis, we measured Nd-isotope ratios of six lunar basalts that span the compositional range of basaltic

  13. I-Xe Dating: The Time Line of Chondrule Formation and Metamorphism in LL Chondrites

    NASA Technical Reports Server (NTRS)

    Pravdivtseva, O. V.; Hohenberg, C. M.; Meshik, A. P.

    2005-01-01

    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 chondrules (from different meteorites) suggested that chondrule 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 chondrules in Allende [2]. The I-Xe ages of CAI s in Allende are about 2 Ma younger than the I-Xe ages of Allende chondrules [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 chondrules the iodine host phases vary and can reflect formation and/or alteration but, to put chondrule ages on a quantative basis, some problems should first be addressed.

  14. Petrology of enstatite chondrites and anomalous enstatite achondrites

    NASA Astrophysics Data System (ADS)

    van Niekerk, Deon

    2012-01-01

    Chondrites are meteorites that represent unmelted portions of asteroids. The enstatite chondrites are one class of chondrites. They consist of reduced mineral assemblages that formed under low oxygen fugacity in the solar nebula, prior to accretion into asteroids. There are two groups of enstatite chondrites---EH and EL. I studied EL3 meteorites, which are understood to be unmetamorphosed and thus to only preserve primitive nebular products. I show in a petrographic study that the EL3s are in fact melt--breccias in which impact-melting produced new mineral assemblages and textures in portions of the host chondrites, after accretion. I document meta- land sulfide assemblages that are intergrown with silicate minerals (which are often euhedral), and occur outside chondrules; these assemblages probably represent impact-melting products, and are different from those in EH3 chondrites that probably represent nebular products. In situ siderophile trace element compositions of the metal in EL3s, obtained by laser ablation inductively coupled plasma mass spectrometry, are consistent with an impact-melting hypothesis. The trace element concentrations show no clear volatility trend, and are thus probably not the result of volatile-driven petrogenetic processes that operated in the solar nebula. Trace element modeling suggests that the character of the trace element patterns together with deviations from the mean bulk EL metal pattern is consistent with metal that crystallized in a coexisting liquid-solid metal system in which dissolved carbon influenced element partitioning. I also conducted a petrographic and mineral-chemistry study of several anomalous enstatite meteorites. These have igneous textures, but unfractionated mineralogy similar to unmelted chondrites. I show that with the exception of one, the meteorites are related to each other, and probably formed by crystallization from an impact melt instead of metamorphism through the decay of short lived radionuclides. The broad importance of these studies lies in documenting the petrology of extraterrestrial materials that reveal the geological history of the young solar system prior to the existence of planets. Furthermore, they serve to identify which mineral assemblages record nebular processes and which record processes on asteroids, so that future studies may select the correct material to address particular questions.

  15. Surviving High-temperature Components in CI Chondrites

    NASA Technical Reports Server (NTRS)

    Zolensky, M.; Frank, D.

    2014-01-01

    The CI1 chondrites, while having the most solar-like compo-sition of any astromaterial available for laboratory analysis, have also been considerably altered by asteroidal processes including aqueous alteration. It is of fundamental importance to determine their pre-alteration mineralogy, so that the state of matter in the early Solar System can be better determined. In the course of a re-examination of the compositional range of olivine and low-Ca pyroxene in CI chondrites Orgueil, Ivuna and Alais [1] we found the first reported complete CAI, as already reported [2], with at-tached rock consisting mainly of olivine and low-Ca pyroxene. The range of residual olivine major element compositions we have determined in the CIs (Fig. 1) may now be directly com-pared with those of other astromaterials, including Wild 2 grains. The abundance of olivine and low-Ca pyroxene in CIs is higher than is generally appreciated, and in fact much higher than for some CMs [1]. We also noted numerous rounded objects varying in shape from spheres to oblate spheroids, and ranging up to 100µm in size (Fig. 2), which have been previously noted [3] but have not been well documented or appreciated. We characterized the mineralogy by transmission electron microscopy and found that they consist mainly of rather fine-grained, flaky single phase to intergrown serpentine and saponite. These two materials in fact dominate the bulk of the host CI1 chondrites. With the exception of sparse spinels, the rounded phyllosilicate objects are remarka-bly free of other minerals, suggesting that the precursor from which the phyllosilicates were derived was a homogeneous mate-rial. We suggest that these round phyllosilicates aggregates in CI1 chondrites were cryptocrystalline to glassy microchondrules. If so then CI chondrites cannot be considered chondrule-free. Small though they are, the abundance of these putative microchondrules is the same as that of chondrules in the Tagish Lake meteorite.

  16. Developing concepts of ordinary and extraordinary communication.

    PubMed

    Lane, Jonathan D; Evans, E Margaret; Brink, Kimberly A; Wellman, Henry M

    2016-01-01

    We examine how understandings of ordinary and extraordinary communication develop. Three- to 10-year-old children and adults (N = 183) were given scenarios in which a protagonist wanted help from a human (their parent) or from God. Scenarios varied in whether protagonists expressed their desires aloud (by asking) or silently (by hoping), whether (for human scenarios) parents were nearby or far away, and whether (for God scenarios) protagonists expressed desires through ordinary means (asking or hoping) or more extraordinary means (praying). Following each scenario, participants were asked whether the recipient (either the parent or God) was aware of the protagonist's desire. Children as young as 3 to 4 years old understood that both loudness and distance limit the effectiveness of human communication, reporting that humans would most likely be aware of desires when they were expressed both aloud and nearby. As well, by this age children reported that God would more often be aware of desires than would humans, but children of all ages often reported that God (like humans) would be more aware of desires expressed aloud (rather than silently). These concepts of ordinary and extraordinary communication continued to be refined through middle childhood. Children's performance on standard theory-of-mind tasks and participants' religious background predicted whether they attributed awareness to God. (PsycINFO Database Record PMID:26501723

  17. Thermomagnetic analysis of meteorites, 3. C3 and C4 chondrites

    USGS Publications Warehouse

    Herndon, J.M.; Rowe, M.W.; Larson, E.E.; Watson, D.E.

    1976-01-01

    Thermomagnetic analysis was made on samples of all known C3 and C4 chondrites in a controlled oxygen atmosphere. Considerable variation was noted in the occurrence of magnetic minerals, comparable to the variation observed earlier in the C2 chondrites. Magnetite was found as the only major magnetic phase in samples of only three C3 chondrites (2-4 wt.%) and the Karoonda C4 chondrite (7.7 wt.%). The magnetite content of these three C3 chondrites is only about one-third that observed in the C1 and C2 chondrites which were found to contain magnetite as the only magnetic phase. Five C3 chondrites were observed to undergo chemical change during heating, producing magnetite: this behavior is characteristic of troilite oxidation. Upper limits on initial magnetite content of about 1-9% were established for these meteorites. Samples of the remaining five C3 chondrites and the Coolidge C4 chondrite were found to contain both magnetite and metallic iron. In two samples, iron containing ???2% Ni was observed, while in the other four, the iron contained 6-8 wt.% Ni. In addition to containing both magnetite and iron metal, three of these samples reacted during heating to form additional magnetite. Variations in the magnetic mineralogy and, hence by inference bulk mineralogy, of C3 and C4 chondrites indicate a more complex genesis than is evident from whole-rock elemental abundance patterns. ?? 1976.

  18. Records of the Moon-forming impact and the 470 Ma disruption of the L chondrite parent body in the asteroid belt from U-Pb apatite ages of Novato (L6)

    NASA Astrophysics Data System (ADS)

    Yin, Qing-Zhu; Zhou, Qin; Li, Qiu-Li; Li, Xian-Hua; Liu, Yu; Tang, Guo-Qiang; Krot, Alexander N.; Jenniskens, Peter

    2014-08-01

    Novato, a newly observed fall in the San Francisco Bay area, is a shocked and brecciated L6 ordinary chondrite containing dark and light lithologies. We have investigated the U-Pb isotope systematics of coarse Cl-apatite grains of metamorphic origin in Novato with a large geometry ion microprobe. The U-Pb systematics of Novato apatite reveals an upper intercept age of 4472 ± 31 Ma and lower intercept age of 473 ± 38 Ma. The upper intercept age is within error identical to the U-Pb apatite age of 4452 ± 21 Ma measured in the Chelyabinsk LL5 chondrite. This age is interpreted to reflect a massive collisional resetting event due to a large impact associated with the peak arrival time at the primordial asteroid belt of ejecta debris from the Moon-forming giant impact on Earth. The lower intercept age is consistent with the most precisely dated Ar-Ar ages of 470 ± 6 Ma of shocked L chondrites, and the fossil meteorites and extraterrestrial chromite relicts found in Ordovician limestones with an age of 467.3 ± 1.6 Ma in Sweden and China. The lower intercept age reflects a major disturbance related to the catastrophic disruption of the L chondrite parent body most likely associated with the Gefion asteroid family, which produced an initially intense meteorite bombardment of the Earth in Ordovician period and reset and degassed at least approximately 35% of the L chondrite falls today. We predict that the 470 Ma impact event is likely to be found on the Moon and Mars, if not Mercury.

  19. 29 CFR 785.35 - Home to work; ordinary situation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Home to work; ordinary situation. 785.35 Section 785.35... Principles Traveltime § 785.35 Home to work; ordinary situation. An employee who travels from home before his regular workday and returns to his home at the end of the workday is engaged in ordinary home to...

  20. 7 CFR 28.426 - Strict Good Ordinary Spotted Color.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Good Ordinary Spotted Color. 28.426 Section 28... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Spotted Cotton § 28.426 Strict Good Ordinary Spotted Color. Strict Good Ordinary Spotted Color is color which is within the range represented by a...

  1. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406... for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good... United States, American Upland, Strict Good Ordinary, effective July 1, 1987.”...

  2. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture... American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color which is within the range... marked “Original Official Cotton Standards of the United States, American Upland, Good...

  3. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406 Agriculture...Standards of the United States for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is...

  4. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture...Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color...

  5. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture...Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color...

  6. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 2011-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture...Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color...

  7. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406 Agriculture...Standards of the United States for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is...

  8. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 2010-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture...Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color...

  9. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture...Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color...

  10. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406 Agriculture...Standards of the United States for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is...

  11. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406 Agriculture...Standards of the United States for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is...

  12. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406 Agriculture...Standards of the United States for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is...

  13. 31 CFR 29.525 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Ordinary and necessary living... Collection Standards for Waiver of Overpayments § 29.525 Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include rent, mortgage payments, utilities,...

  14. 31 CFR 29.525 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance: Treasury 1 2011-07-01 2011-07-01 false Ordinary and necessary living... Collection Standards for Waiver of Overpayments § 29.525 Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include rent, mortgage payments, utilities,...

  15. 5 CFR 845.305 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Ordinary and necessary living expenses... of Overpayments § 845.305 Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include rent, mortgage payments, utilities, maintenance, transportation,...

  16. 5 CFR 845.305 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 2 2011-01-01 2011-01-01 false Ordinary and necessary living expenses... of Overpayments § 845.305 Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include rent, mortgage payments, utilities, maintenance, transportation,...

  17. 22 CFR 17.6 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Ordinary and necessary living expenses. 17.6... FOREIGN SERVICE PENSION SYSTEM (FSPS) § 17.6 Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include rent, mortgage payments, utilities, maintenance,...

  18. 22 CFR 17.6 - Ordinary and necessary living expenses.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Ordinary and necessary living expenses. 17.6... FOREIGN SERVICE PENSION SYSTEM (FSPS) § 17.6 Ordinary and necessary living expenses. An individual's ordinary and necessary living expenses include rent, mortgage payments, utilities, maintenance,...

  19. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color which is within the...

  20. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color which is within the...

  1. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406... for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is color which is within the range represented by a set of samples in the custody of...

  2. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406... for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is color which is within the range represented by a set of samples in the custody of...

  3. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406... for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is color which is within the range represented by a set of samples in the custody of...

  4. 7 CFR 28.406 - Strict Good Ordinary Color.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406... for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is color which is within the range represented by a set of samples in the custody of...

  5. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color which is within the...

  6. 7 CFR 28.407 - Good Ordinary Color.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Good Ordinary Color. 28.407 Section 28.407 Agriculture..., TESTING, AND STANDARDS Standards Official Cotton Standards of the United States for the Color Grade of American Upland Cotton § 28.407 Good Ordinary Color. Good Ordinary Color is color which is within the...

  7. Quantitative methods for three-dimensional comparison and petrographic description of chondrites

    SciTech Connect

    Friedrich, J.M.

    2008-10-20

    X-ray computed tomography can be used to generate three-dimensional (3D) volumetric representations of chondritic meteorites. One of the challenges of using collected X-ray tomographic data is the extraction of useful data for 3D petrographic analysis or description. Here, I examine computer-aided quantitative 3D texture metrics that can be used for the classification of chondritic meteorites. These quantitative techniques are extremely useful for discriminating between chondritic materials, but yield little information on the 3D morphology of chondrite components. To investigate the morphology of chondrite minerals such as Fe(Ni) metal and related sulfides, the homology descriptors known as Betti numbers, are examined. Both methodologies are illustrated with theoretical discussion and examples. Betti numbers may be valuable for examining the nature of metal-silicate structural changes within chondrites with increasing degrees of metamorphism.

  8. Odeint - Solving ordinary differential equations in C++

    E-print Network

    Karsten Ahnert; Mario Mulansky

    2011-10-15

    Many physical, biological or chemical systems are modeled by ordinary differential equations (ODEs) and finding their solution is an every-day-task for many scientists. Here, we introduce a new C++ library dedicated to find numerical solutions of initial value problems of ODEs: odeint (www.odeint.com). odeint is implemented in a highly generic way and provides extensive interoperability at top performance. For example, due to it's modular design it can be easily parallized with OpenMP and even runs on CUDA GPUs. Despite that, it provides a convenient interface that allows for a simple and easy usage.

  9. Generalized Ordinary Differential Equation Models 1

    PubMed Central

    Miao, Hongyu; Wu, Hulin; Xue, Hongqi

    2014-01-01

    Existing estimation methods for ordinary differential equation (ODE) models are not applicable to discrete data. The generalized ODE (GODE) model is therefore proposed and investigated for the first time. We develop the likelihood-based parameter estimation and inference methods for GODE models. We propose robust computing algorithms and rigorously investigate the asymptotic properties of the proposed estimator by considering both measurement errors and numerical errors in solving ODEs. The simulation study and application of our methods to an influenza viral dynamics study suggest that the proposed methods have a superior performance in terms of accuracy over the existing ODE model estimation approach and the extended smoothing-based (ESB) method. PMID:25544787

  10. Quantization of minisuperspaces as ordinary gauge systems

    E-print Network

    Simeone, C

    1998-01-01

    Simple cosmological models are used to show that gravitation can be quantized as an ordinary gauge system if the Hamilton-Jacobi equation for the model under consideration is separable. In this situation, a canonical transformation can be performed such that in terms of the new variables the model has a linear and homogeneous constraint, and therefore canonical gauges are admissible in the path integral. This has the additional practical advantage that gauge conditions that do not generate Gribov copies are then easy to choose.

  11. Petrography, mineral chemistry and origin of Type I enstatite chondrites

    NASA Technical Reports Server (NTRS)

    Leitch, C. A.; Smith, J. V.

    1982-01-01

    The petrography and mineralogy of four Type I enstatite chondrites were examined by optical and cathololuminescent and electron microprobe means to discern particular chemical and mechanical processes present during solar system condensation. The specimens examined included sections of the Indarch, Abee, Kota-Kota, and Adhi-Kot chondrites. Textural interpretations were performed, as well as chemical analyses of the degree of similarity of the clinoenstatite, olivine, accessory silicates, metal, schreibersite, troilite, oldhamite, and niningerite grains in each sample. Simple models of progressive condensation either at equilibrium or with mechanical removal of early condensates were ruled out due to the occurrence of both blue and red enstatite crystals in metal clasts. A need for sequential processes of mixing, melting, crystallization, condensation, fracturing, and mechanical aggregation are suggested as necessary to model the formation mechanisms of the mineral aggregates.

  12. New Titanium Monosulfide Mineral Phase in Yamato 691 Enstatite Chondrite

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K; Clemett, S. J.; Rubin, A. E.; Choi, B.-G.; Zhang, S.; Rahman, Z.; Oikawa, K.; Keller, L. P.

    2011-01-01

    Yamato 691, an EH3 enstatite chondrite, was among the first meteorites discovered by chance in Antarctica by the Japanese Antarctic Research Expedition (JARE) team in 1969. This discovery led to follow-up searches for meteorites in Antarctica [1]. These international searches have been very successful recovering over 40,000 total specimens (and still counting), including martian and lunar meteorites. Titanium is partly chalcophile in enstatite-rich meteorites. Previous occurrences of Ti-bearing sulfides include troilite, daubrelite and ferroan alabandite in enstatite chondrites and aubrites [2], and heideite with 28.5 wt% Ti in the Bustee aubrite [3]. Here we report a new mineral from Yamato 691, ideally stoichiometric TiS, titanium monosulfide, a simple two-element mineral phase, yet with a very unique crystal structure that, to our knowledge, has not been observed previously in nature.

  13. 21 Lutetia as the likely parent body of CH chondrites

    NASA Astrophysics Data System (ADS)

    Trigo-Rodríguez, J. M.; Moyano-Cambero, C. E.; Llorca, J.; Barucci, A.; Fornasier, S.; Belskaya, I.; Binzel, R.; Rivkin, AS.

    2012-09-01

    The reflectance spectra of the different groups of carbonaceous chondrites (hereafter CCs) reflects a large compositional diversity. CC groups exhibit different components and distinctive abundance ratios that are the main reasons for a large spectral diversity [1, 2]. A precise visible reflectance spectra of asteroid 21 Lutetia was recently obtained by VIRTIS spectrometer on board the Rosetta (ESA) spacecraft [3]. All collected evidence suggests that 21 Lutetia is a primitive asteroid, but exhibiting far higher reflectance than the measured for the most common groups of CCs [3, 4]. In any case, Rosetta data can be compared with our recently taken laboratory spectra of rare CC groups from the NASA Antarctic collection. As a result we have found an excellent candidate to fit that reflectance pattern in the CH group of carbonaceous chondrites. We exemplify that presenting the UV to nIR spectrum of one of the most pristine CHs available in our collections: PCA 91467.

  14. A CAI in the Ivuna CI1 Chondrite

    NASA Technical Reports Server (NTRS)

    Frank, David R.; Zolensky, M.; Martinez, J.; Mikouchi, T.; Ohsumi, K.; Hagiya, K.; Satake, W.; Le, L.; Ross, D.; Peslier, A.

    2011-01-01

    We have recently discovered the first well-preserved calcium aluminum-rich inclusion (CAI) in a CI1 chondrite (Ivuna). Previously, all CI1 chondrites were thought to be devoid of preserved CAI and chondrules due to the near total aqueous alteration to which their parent body (bodies) have been subjected. The CAI is roughly spherical, but with a slight teardrop geometry and a maximum diameter of 170 microns (fig. 1). It lacks any Wark-Lovering Rim. Incipient aqueous alteration, and probably shock, have rendered large portions of the CAI poorly crystalline. It is extremely fine-grained, with only a few grains exceeding 10 microns. We have performed electron microprobe analyses (EPMA), FEG-SEM imaging and element mapping, as well as electron back-scattered diffraction (EBSD) and synchrotron X-ray diffraction (SXRD) in order to determine the fundamental characteristics of this apparently unique object.

  15. Comparing Amino Acid Abundances and Distributions Across Carbonaceous Chondrite Groups

    NASA Technical Reports Server (NTRS)

    Burton, Aaron S.; Callahan, Michael P.; Glavin, Daniel P.; Elsila, Jamie E.; Dworkin, Jason P.

    2012-01-01

    Meteorites are grouped according to bulk properties such as chemical composition and mineralogy. These parameters can vary significantly among the different carbonaceous chondrite groups (CI, CM, CO, CR, CH, CB, CV and CK). We have determined the amino acid abundances of more than 30 primary amino acids in meteorites from each of the eight groups, revealing several interesting trends. There are noticeable differences in the structural diversity and overall abundances of amino acids between meteorites from the different chondrite groups. Because meteorites may have been an important source of amino acids to the prebiotic Earth and these organic compounds are essential for life as we know it, the observed variations of these molecules may have been important for the origins of life.

  16. Axtrell, a new CV3 chondrite find from Texas

    NASA Technical Reports Server (NTRS)

    Simon, S. B.; Grossman, L.; Casanova, I.; Symes, S.; Benoit, P.; Sears, D. W. G.; Wacker, J. F.

    1995-01-01

    We describe a previously unreported meteorite found in Axtell, Texas, in 1943. Based on the mineralogical composition and texture of its matrix and the sizes and abundance of chondrules, we classify it as a CV3 carbonaceous chondrite. The dominant opaque phase in the chondrules is magnetite, and that in refractory inclusions is Ni-rich metal (awaruite). Axtell, therefore, belongs to the oxidized subgroup of CV3 chondrites, although unlike Allende it escaped strong sulfidation. The meteorite bears a strong textural resemblance to Allende, and its chondrule population and matrix appear to be quite similar to those of Allende, but its refractory inclusions, thermoluminescence properties, and cosmogenic Co-60 abundances are not. Our data are consistent with a terrestrial age for Axtell of approximately 100 years and a metamorphic grade slightly lower than that of Allende.

  17. Petrology of ALH85085 - A chondrite with unique characteristics

    NASA Technical Reports Server (NTRS)

    Weisberg, Michael K.; Nehru, Cherukupalli E.; Prinz, Martin

    1988-01-01

    The characteristics of the chondrite ALH85085 are examined. It is found that the chondrules of ALH85085 are 25-75 microns in size. The majority of the chondrules are cryptocrystalline and all of them are volatile depleted. It is shown that the FeNi metal abundance is 40.9 wt pct and the sulfide abundance is 1.1 wt pct. The matrix lumps and bulk composition of ALH85085 are analyzed. The characteristics of ALH85085 are compared with other chondrite groups, showing that it cannot be classified. The possible origin of ALH85085 is analyzed, showing trends similar to those of calculated nebular condensation paths indicating a nebular origin.

  18. Vein formation in the C1 carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Richardson, S. M.

    1978-01-01

    Veins in the C1 chondrites Orgueil, Alais, and Ivuna have been deposited during an extended period of impact brecciation and leaching. At least three generations of mineralization, dominated successively by carbonates, calcium sulfate, and magnesium sulfate, can be recognized. Vein minerals are derived locally by closed-system reactions between matrix phyllosilicates and an aqueous fluid, with the result that few, if any, primitive mineral phases still exist in the C1s.

  19. Compositions and taxonomy of 15 unusual carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Choe, Won Hie; Huber, Heinz; Rubin, Alan E.; Kallemeyn, Gregory W.; Wasson, John T.

    2010-04-01

    We used instrumental neutron activation analysis and petrography to determine bulk and phase compositions and textural characteristics of 15 carbonaceous chondrites of uncertain classification: Acfer 094 (type 3.0, ungrouped CM-related); Belgica-7904 (mildly metamorphosed, anomalous, CM-like chondrite, possibly a member of a new grouplet that includes Wisconsin Range (WIS) 91600, Dhofar 225, and Yamato-86720); Dar al Gani (DaG) 055 and its paired specimen DaG 056 (anomalous, reduced CV3-like); DaG 978 (type 3 ungrouped); Dominion Range 03238 (anomalous, magnetite-rich CO3.1); Elephant Moraine 90043 (anomalous, magnetite-bearing CO3); Graves Nunataks 98025 (type 2 or type 3 ungrouped); Grosvenor Mountains (GRO) 95566 (anomalous CM2 with a low degree of aqueous alteration); Hammadah al Hamra (HaH) 073 (type 4 ungrouped, possibly related to the Coolidge-Loongana [C-L] 001 grouplet); Lewis Cliff (LEW) 85311 (anomalous CM2 with a low degree of aqueous alteration); Northwest Africa 1152 (anomalous CV3); Pecora Escarpment (PCA) 91008 (anomalous, metamorphosed CM); Queen Alexandra Range 99038 (type 2 ungrouped); Sahara 00182 (type 3 ungrouped, possibly related to HaH 073 and/or to C-L 001); and WIS 91600 (mildly metamorphosed, anomalous, CM-like chondrite, possibly a member of a new grouplet that includes Belgica-7904, Dhofar 225, and Y-86720). Many of these meteorites show fractionated abundance patterns, especially among the volatile elements. Impact volatilization and dehydration as well as elemental transport caused by terrestrial weathering are probably responsible for most of these compositional anomalies. The metamorphosed CM chondrites comprise two distinct clusters on the basis of their ?17O values: approximately -4‰ for PCA 91008, GRO 95566, DaG 978, and LEW 85311, and approximately 0‰ for Belgica-7904 and WIS 91600. These six meteorites must have been derived from different asteroidal regions.

  20. Non-spherical Lobate Chondrules in CO3.0 Y-81020: General Implications for the Formation of Low-FeO Porphyritic Chondrules in CO Chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Wasson, John T.

    2006-01-01

    Non-spherical chondrules (arbitrarily defined as having aspect ratios greater than or equal to 1.20) in CO3.0 chondrites comprise multi-lobate, distended, and highly irregular objects with rounded margins; they constitute approx. 70% of the type-I (low-FeO) porphyritic chondrules in Y-81020, approx. 75% of such chondrules in ALHA77307, and approx. 60% of those in Colony. Although the proportion of non-spherical type-I chondrules in LL3.0 Semarkona is comparable (approx. 60%), multi-lobate OC porphyritic chondrules (with lobe heights equivalent to a significant fraction of the mean chondrule diameter) are rare. If the non-spherical type-I chondrules in CO chondrites had formed from totally molten droplets, calculations indicate that they would have collapsed into spheres within approx. 10(exp -3) s, too little time for their 20-micrometer-size olivine phenocrysts to have grown from the melt. These olivine grains must therefore be relicts from an earlier chondrule generation; the final heating episode experienced by the non-spherical chondrules involved only minor amounts of melting and crystallization. The immediate precursors of the individual non-spherical chondrules may have been irregularly shaped chondrule fragments whose fracture surfaces were rounded during melting. Because non-spherical chondrules and circular chondrules form a continuum in shape and have similar grain sizes, mineral and mesostasis compositions, and modal abundances of non-opaque phases, they must have formed by related processes. We conclude that a large majority of low-FeO chondrules in CO3 chondrites experienced a late, low-degree melting event. Previous studies have shown that essentially all type-II (high-FeO) porphyritic chondrules in Y-81020 formed by repeated episodes of low-degree melting. It thus appears that the type-I and type-II porphyritic chondrules in Y-81020 (and, presumably, all CO3 chondrites) experienced analogous formation histories. Because these two types constitute approx. 95% of all CO chondrules, it is clear that chondrule recycling was the rule in the CO chondrule-formation region and that most melting events produced only low degrees of melting. The rarity of significantly non-spherical, multi-lobate chondrules in Semarkona may reflect more-intense heating of chondrule precursors in the ordinary-chondrite region of the solar nebula.

  1. Chondritic models of 4 Vesta: Comparison of data from the Dawn mission with predicted internal structure and surface composition/mineralogy.

    NASA Astrophysics Data System (ADS)

    Toplis, M. J.; Mizzon, H.; Forni, O.; Monnereau, M.; Barrat, J. A.; Prettyman, T. H.; McSween, H. Y.; McCoy, T. J.; Mittlefehldt, D. W.; De Sanctis, M. C.; Raymond, C. A.; Russell, C. T.

    2012-04-01

    While the HEDs provide an extremely useful basis for interpreting data from the Dawn mission, there is no guarantee that they provide a complete vision of all possible crustal (and possibly mantle) lithologies that are exposed at the surface of Vesta. With this in mind, an alternative approach is to identify plausible bulk compositions and use mass-balance and geochemical modelling to predict possible internal structures and crust/mantle compositions and mineralogies. While such models must be consistent with known HED samples, this approach has the potential to extend predictions to thermodynamically plausible rock types that are not necessarily present in the HED collection. Nine chondritic bulk compositions are considered (CI, CV, CO, CM, H, L, LL, EH, EL). For each, relative proportions and densities of the core, mantle, and crust are quantified. This calculation is complicated by the fact that iron may occur in metallic form (in the core) and/or in oxidized form (in the mantle and crust). However, considering that the basaltic crust has the composition of Juvinas and assuming that this crust is in thermodynamic equilibrium with the residual mantle, it is possible to calculate a single solution to this problem for a given bulk composition. Of the nine bulk compositions tested, solutions corresponding to CI and LL groups predicted a negative metal fraction and were not considered further. Solutions for enstatite chondrites imply significant oxidation relative to the starting materials and these solutions too are considered unlikely. For the remaining bulk compositions, the relative proportion of crust to bulk silicate is typically in the range 15 to 20% corresponding to crustal thicknesses of 15 to 20 km for a porosity-free Vesta-sized body. The mantle is predicted to be largely dominated by olivine (>85%) for carbonaceous chondrites, but to be a roughly equal mixture of olivine and pyroxene for ordinary chondrite precursors. All bulk compositions have a significant core, but the relative proportions of metal and sulphide can be widely different. Using these data, total core size (metal+ sulphide) and average core densities can be calculated, providing a useful reference frame within which to consider geophysical/gravity data of the Dawn mission. Further to these mass-balance calculations, the MELTS thermodynamic calculator has been used to assess to what extent chondritic bulk compositions can produce Juvinas-like liquids at relevant degrees of partial melting/crystallization. This work will refine acceptable bulk compositions and predict the mineralogy and composition of the associated solid and liquid products over wide ranges of partial melting and crystallization, providing a useful and self-consistent reference frame for interpretation of the data from the VIR and GRaND instruments onboard the Dawn spacecraft.

  2. Timescales and settings for alteration of chondritic meteorites

    SciTech Connect

    Krot, A N; Hutcheon, I D; Brearley, A J; Pravdivtseva, O V; Petaev, M I; Hohenberg, C M

    2005-11-16

    Most groups of chondritic meteorites experienced diverse styles of secondary alteration to various degrees that resulted in formation of hydrous and anhydrous minerals (e.g., phyllosilicates, magnetite, carbonates, ferrous olivine, hedenbergite, wollastonite, grossular, andradite, nepheline, sodalite, Fe,Ni-carbides, pentlandite, pyrrhotite, Ni-rich metal). Mineralogical, petrographic, and isotopic observations suggest that the alteration occurred in the presence of aqueous solutions under variable conditions (temperature, water/rock ratio, redox conditions, and fluid compositions) in an asteroidal setting, and, in many cases, was multistage. Although some alteration predated agglomeration of the final chondrite asteroidal bodies (i.e. was pre-accretionary), it seems highly unlikely that the alteration occurred in the solar nebula, nor in planetesimals of earlier generations. Short-lived isotope chronologies ({sup 26}Al-{sup 26}Mg, {sup 53}Mn-{sup 53}Cr, {sup 129}I-{sup 129}Xe) of the secondary minerals indicate that the alteration started within 1-2 Ma after formation of the Ca,Al-rich inclusions and lasted up to 15 Ma. These observations suggest that chondrite parent bodies must have accreted within the first 1-2 Ma after collapse of the protosolar molecular cloud and provide strong evidence for an early onset of aqueous activity on these bodies.

  3. Comparing Wild 2 Particles to Chondrites and IDPS

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Nakamura-Messenger, Keiko; Rietmeijer, Frans; Leroux, Hugues; Mikouchi, Takashi; Ohsumi, Kazumasa; Simon, Steven; Grossman, Lawrence; Stephan, Thomas; Weisberg, Michael; Velbel, Michael; Zega, Thomas; Stroud, Rhonda; Tomeoka, Kazushige; Ohnishi, Ichiro; Tomioka, Naotaka; Nakamura, Tomoki; Matrajt, Graciela; Joswiak, David; Brownlee, Don; Langenhorst, Falko; Krot, Alexander; Kearsley, Anton; Ishii, Hope; Graham, Giles

    2008-01-01

    We compare the observed composition ranges of olivine, pyroxene and Fe-Ni sulfides in Wild 2 grains, comparing these with chondritic IDPs and chondrite classes to explore whether these data suggest affinities to known hydrous materials in particular. Wild 2 olivine has an extremely wide composition range, from Fo4-100 with a pronounced frequency peak at Fo99. The composition range displayed by the low-calcium pyroxene is also very extensive, from En52 to En100, with a significant frequency peak centered at En95. These ranges are as broad or broader than those reported for any other extraterrestrial material. Wild 2 Fe-Ni sulfides mainly have compositions close to that of FeS, with less than 2 atom % Ni - to date, only two pentlandite grains have been found among the Wild-grains suggesting that this mineral is not abundant. The complete lack of compositions between FeS and pentlandite (with intermediate solid solution compositions) suggests (but does not require) that FeS and pentlandite condensed as crystalline species, i.e. did not form as amorphous phases, which later became annealed. While we have not yet observed any direct evidence of water-bearing minerals, the presence of Ni-bearing sulfides, and magnesium-dominated olivine and low-Ca pyroxene does not rule out their presence at low abundance. We do conclude that modern major and minor element compositions of chondrite matrix and IDPs are needed.

  4. Timescales and Settings for Alteration of Chondritic Meteorites

    NASA Astrophysics Data System (ADS)

    Krot, A. N.; Hutcheon, I. D.; Brearley, A. J.; Pravdivtseva, O. V.; Petaev, M. I.; Hohenberg, C. M.

    Most groups of chondritic meteorites experienced diverse styles of secondary alteration to various degrees that resulted in formation of hydrous and anhydrous minerals (e.g., phyllosilicates, magnetite, carbonates, ferrous olivine, hedenbergite, wollastonite, grossular, and radite, nepheline, sodalite, Fe, Ni-carbides, pentlandite, pyrrhotite, and Ni-rich metal). Mineralogical, petrographic, and isotopic observations suggest that the alteration occurred in the presence of aqueous solutions under variable conditions (temperature, water/rock ratio, redox conditions, and fluid compositions) in an asteroidal setting, and, in many cases, was multistage. Although some alteration predated agglomeration of the final chondrite asteroidal bodies (i.e., was preaccretionary), it seems highly unlikely that the alteration occurred in the solar nebula, nor in planetesimals of earlier generations. Short-lived isotope chronologies (26Al-26Mg, 53Mn-53Cr, 129I-129Xe) of the secondary minerals indicate that the alteration started within 1-2 m.y. after formation of the Ca,Al-rich inclusions and lasted up to 15 m.y. These observations suggest that chondrite parent bodies must have accreted within the first 1-2 m.y. after collapse of the protosolar molecular cloud and provide strong evidence for an early onset of aqueous activity on these bodies.

  5. Simple computer experiments with ordinary ice.

    PubMed

    Shulgin, Ivan L; Ruckenstein, Eli

    2006-10-26

    Simple computer experiments in which various fractions of hydrogen bonds (H-bonds) in ice are allowed to break are presented in this paper. First, up to six million water molecules were used to build an artificial piece of ordinary hexagonal ice in the form of a cube, a monolayer, a bilayer, a trilayer, and thicker layers. Then, certain percentages of H-bonds were broken, and the obtained structures were examined. It was found that a large percentage of H-bonds must be broken in order to completely fragment the network of ice into clusters. For a cubic piece of ice, which can be considered bulk ordinary ice, this percentage is equal to 61% H-bonds, a figure also predicted as the threshold of the percolation theory for ice. If, as usually assumed, 13-20% of H-bonds are broken during melting (estimates based on the comparison between the heats of melting and sublimation of ice), the H-bond network of ice is not fragmented and the overwhelming majority of water molecules (>99%) belong to a new, distorted but unbroken network. The percentage of broken H-bonds required for full fragmentation of layers increases with the number of layers and reaches the bulk value of ice for 5-8 layers. This value is consistent with the literature observation that films of water thicker than 20-30 A have properties close to those of the bulk structure. PMID:17048969

  6. Workshop on Parent-Body and Nebular Modification of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E. (Editor); Krot, A. N. (Editor); Scott, E. R. D. (Editor)

    1997-01-01

    Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

  7. Lunar and Planetary Science XXXV: Organics and Alteration in Carbonaceous Chondrites: Goop and Crud

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Organics and Alteration in Carbonaceous Chondrites: Goop and Crud" included the following reports:Organics on Fe-Silicate Grains: Potential Mimicry of Meteoritic Processes?; Molecular and Compound-Specific Isotopic Study of Monocarboxylic Acids in Murchison and Antarctic Meteorites; Nanoglobules, Macromolecular Materials, and Carbon Sulfides in Carbonaceous Chondrites; Evidence for Terrestrial Organic Contamination of the Tagish Lake Meteorite; Nitrogen Isotopic Imaging of Tagish Lake Carbon Globules; Microscale Distribution of Hydrogen Isotopes in Two Carbonaceous Chondrites; The Nature and Origin of Aromatic Organic Matter in the Tagish Lake Meteorite; Terrestrial Alteration of CM Chondritic Carbonate; Serpentine Nanotubes in CM Chondrites; Experimental Study of Serpentinization Reactions; Chondrule Glass Alteration in Type IIA Chondrules in the CR2 Chondrites EET 87770 and EET 92105: Insights into Elemental Exchange Between Chondrules and Matrices; Aqueous Alteration of Carbonaceous Chondrites: New Insights from Comparative Studies of Two Unbrecciated CM2 Chondrites, Y 791198 and ALH 81002 ;and A Unique Style of Alteration of Iron-Nickel Metal in WIS91600, an Unusual C2 Carbonaceous Chondrite.

  8. Pyroxene thermobarometry in LL-group chondrites and implications for parent body metamorphism

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Patchen, Allan D.

    1989-01-01

    Geothermometry based on the compositions of clinopyroxenes in type 6 and 7 LL chondrites gives coherent results, but the estimated temperatures from coexisting orthopyroxenes are consistently lower than for clinopyroxenes. Orthopyroxene thermometry is suspect because of compositional effects of polymorphic inversions and/or unknown kinetic factors. Lack of clinopyroxene equilibration precludes accurate estimation of peak metamorphic temperatures for type 4 and 5 chondrites. There is no apparent correlation between Al content (a pressure-dependent variable) and equilibration temperature in chondritic pyroxenes. This finding, which is at variance with a previously published conclusion that temperature and pressure are correlated in metamorphosed chondrites, may have important implications for asteroid thermal models.

  9. Ordinary planetary systems - Architecture and formation

    NASA Technical Reports Server (NTRS)

    Levy, E. H.

    1993-01-01

    Today we believe ordinary planetary systems to be an unremarkable consequence of star formation. The solar system, so far the only confidently known example in the universe of a planetary system, displays a set of striking structural regularities. These structural regularities provide fossil clues about the conditions and mechanisms that gave rise to the planets. The formation of our planetary system, as well as its general characteristics, resulted from the physical environment in the disk-shaped nebula that accompanied the birth of the sun. Observations of contemporary star formation indicate that the very conditions and mechanisms thought to have produced our own planetary system are widely associated with the birth of stars elsewhere. Consequently, it is reasonable to believe that planetary systems occur commonly, at least in association with single, sunlike stars. Moreover, it is reasonable to believe that many planetary systems have gross characteristics resembling those of our own solar system.

  10. Gamma Ray Signatures from Ordinary Cosmic Strings

    E-print Network

    Jane H. MacGibbon; Robert H. Brandenberger

    1992-06-19

    We calculate the flux of ultra high energy photons from individual ordinary (i.e. non-superconducting) cosmic strings and compare the results with the sensitivity of current and proposed TeV and EeV telescopes. Our calculations give only upper limits for the gamma ray flux, since the source of the photons, jets from particle production at cusps, may be weakened by back reaction effects. For the usual cosmic distribution of strings, the predicted bursts from strings with the value of mass per unit length associated with galaxy formation or light strings may just be detectable. A diffuse gamma ray background from light strings may also be seen by the Fly's Eye detector at above $7 \\times 10^{10}$ GeV.

  11. Tuesday, March 24, 2009 POSTER SESSION I: CRASHING CHONDRITES: IMPACT, SHOCK, AND MELTING

    E-print Network

    Rathbun, Julie A.

    Rate of H-Chondrite Impact Melt Breccia LAP 04751 [#2034] An impact event melted a portion of the H-chondrite parent body, mixing with surviving clastic material. The melt-rich breccia was deposited as a thin unit at a depth breccia lens. Schrader D. L

  12. Carbonate compositions in CM and CI chondrites, and implications for aqueous alteration

    NASA Technical Reports Server (NTRS)

    Johnson, Craig A.; Prinz, Martin

    1993-01-01

    Carbonate minerals in fourteen CM chondrites and two CI chondrites have been analyzed by electron microprobe to provide a better understanding of the aqueous processes that affected carbonaceous chondrite parent bodies. Calcites in CM chondrites and dolomites and magnesites in CI chondrites display the compositions expected of stable phases formed at low temperatures. Dolomites in CM chondrites, identified here for the first time in five members of the group, have small amounts of excess Ca which may reflect metastable growth. The distribution of Fe between dolomite and coexisting serpentine differs in the two chondrite groups. If the distributions reflect an approach to chemical equilibrium, then the difference implies higher alteration temperatures for the CI group than the CM group in agreement with the results of previously published oxygen isotope thermometry and mineral solubility modeling of the alteration process. Dolomite Fe contents are relatively uniform in the two chondrite groups. Dolomite Mn contents, by contrast, vary widely. The variations may reflect transport-controlled coprecipitation of Mn resulting from a heterogeneous distribution of the element in the anhydrous precursor material. If this interpretation is correct, then the altering fluids were essentially immobile white hydration reactions proceeded on the meteorite parent bodies. The near closed-system character of the alteration process, long known from bulk chemical analyses of the meteorites, is a direct consequence of the limited mobility of dissolved species.

  13. Trace element content of chondritic cosmic dust: Volatile enrichments, thermal alterations, and the possibility of contamination

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Sutton, S. R.; Bajt, S.

    1993-01-01

    Trace element abundances in 51 chondritic Interplanetary Dust Particles (IDP's) were measured by Synchrotron X-Ray Fluorescence (SXRF). The data allow us to determine an average composition of chondritic IDP's and to examine the questions of volatile loss during the heating pulse experienced on atmospheric entry and possible element addition due to contamination during atmospheric entry, stratospheric residence, and curation.

  14. Chondrites and the Protoplanetary Disk ASP Conference Series, Vol. 341, 2005

    E-print Network

    Garden St., Cambridge, MA 02138, USA Abstract. Recent work on the high temperature origins of chondritic- drule formation, and on the chemical processes most responsible for metal formation, including elements, generating the different chemical reservoirs from which these chondrite groups and planets

  15. Abyssal peridotites reveal the near-chondritic Fe isotopic composition of the Earth

    E-print Network

    Abyssal peridotites reveal the near-chondritic Fe isotopic composition of the Earth Paul R Accepted 11 January 2013 Editor: B. Marty Keywords: iron isotope abyssal peridotite mantle chondritic a b basalts is unknown. Here we report Fe isotopic measurements of abyssal peridotites, which are the residues

  16. PRINT ONLY: CHONDRITES Cole K. J. Schultz L. Sipiera P. P. Welten K. C.

    E-print Network

    Rathbun, Julie A.

    Composition of the Dubrovnik L Chondrite Breccia [#1131] Petrology, mineralogy, and noble gas composition of the Dubrovnik L chondrite breccia showing beautiful dark-light structure are characterized. It consists mainly formation of breccia. Lunar and Planetary Science XXXVIII (2007) sess806.pdf #12;KILABO AND BENSOUR, TWO LL6

  17. Chips Off the Old Block: Enstatite Chondrites as Samples of the Proto-Earth

    NASA Astrophysics Data System (ADS)

    Gaidos, E.; Yin, Q.-Z.

    2015-07-01

    We link enstatite chondrites (EC) formation with the evolution of the early solar system and propose that EC formed when proto-earth material equilibrated with oxygen-poor gas from which solids of carbonaceous chondrite-like composition were removed.

  18. Mineralogy and Petrology of Yamato 86029: A New Type of Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Tonui, E.; Zolensky, M. E.

    2001-01-01

    Y-86029 resembles CI chondrites. Its matrix is very fine-grained. Olivine shows evidence of shock, which has rarely been observed in carbonaceous chondrites. Y-86029 experienced aqueous and thermal alteration during or after accretion in parent body. Additional information is contained in the original extended abstract.

  19. Zoology of condensed matter: Framids, ordinary stuff, extra-ordinary stuff

    E-print Network

    Nicolis, Alberto; Piazza, Federico; Rattazzi, Riccardo

    2015-01-01

    We classify condensed matter systems in terms of the spacetime symmetries they spontaneously break. In particular, we characterize condensed matter itself as any state in a Poincar\\'e-invariant theory that spontaneously breaks Lorentz boosts while preserving at large distances some form of spatial translations, time-translations, and possibly spatial rotations. Surprisingly, the simplest, most minimal system achieving this symmetry breaking pattern---the "framid"---does not seem to be realized in Nature. Instead, Nature usually adopts a more cumbersome strategy: that of introducing internal translational symmetries---and possibly rotational ones---and of spontaneously breaking them along with their space-time counterparts, while preserving unbroken diagonal subgroups. This symmetry breaking pattern describes the infrared dynamics of ordinary solids, fluids, superfluids, and---if they exist---supersolids. A third, "extra-ordinary", possibility involves replacing these internal symmetries with other symmetries ...

  20. The Paris meteorite, the least altered CM chondrite so far

    NASA Astrophysics Data System (ADS)

    Hewins, Roger H.; Bourot-Denise, Michèle; Zanda, Brigitte; Leroux, Hugues; Barrat, Jean-Alix; Humayun, Munir; Göpel, Christa; Greenwood, Richard C.; Franchi, Ian A.; Pont, Sylvain; Lorand, Jean-Pierre; Cournède, Cécile; Gattacceca, Jérôme; Rochette, Pierre; Kuga, Maïa; Marrocchi, Yves; Marty, Bernard

    2014-01-01

    The Paris chondrite provides an excellent opportunity to study CM chondrules and refractory inclusions in a more pristine state than currently possible from other CMs, and to investigate the earliest stages of aqueous alteration captured within a single CM bulk composition. It was found in the effects of a former colonial mining engineer and may have been an observed fall. The texture, mineralogy, petrography, magnetic properties and chemical and isotopic compositions are consistent with classification as a CM2 chondrite. There are ?45 vol.% high-temperature components mainly Type I chondrules (with olivine mostly Fa0-2, mean Fa0.9) with granular textures because of low mesostasis abundances. Type II chondrules contain olivine Fa7 to Fa76. These are dominantly of Type IIA, but there are IIAB and IIB chondrules, II(A)B chondrules with minor highly ferroan olivine, and IIA(C) with augite as the only pyroxene. The refractory inclusions in Paris are amoeboid olivine aggregates (AOAs) and fine-grained spinel-rich Ca-Al-rich inclusions (CAIs). The CAI phases formed in the sequence hibonite, perovskite, grossite, spinel, gehlenite, anorthite, diopside/fassaite and forsterite. The most refractory phases are embedded in spinel, which also occurs as massive nodules. Refractory metal nuggets are found in many CAI and refractory platinum group element abundances (PGE) decrease following the observed condensation sequences of their host phases. Mn-Cr isotope measurements of mineral separates from Paris define a regression line with a slope of 53Mn/55Mn = (5.76 ± 0.76) × 106. If we interpret Cr isotopic systematics as dating Paris components, particularly the chondrules, the age is 4566.44 ± 0.66 Myr, which is close to the age of CAI and puts new constraints on the early evolution of the solar system. Eleven individual Paris samples define an O isotope mixing line that passes through CM2 and CO3 falls and indicates that Paris is a very fresh sample, with variation explained by local differences in the extent of alteration. The anhydrous precursor to the CM2s was CO3-like, but the two groups differed in that the CMs accreted a higher proportion of water. Paris has little matrix (?47%, plus 8% fine grained rims) and is less altered than other CM chondrites. Chondrule silicates (except mesostasis), CAI phases, submicron forsterite and amorphous silicate in the matrix are all well preserved in the freshest domains, and there is abundant metal preserved (metal alteration stage 1 of Palmer and Lauretta (2011)). Metal and sulfide compositions and textures correspond to the least heated or equilibrated CM chondrites, Category A of Kimura et al. (2011). The composition of tochilinite-cronstedtite intergrowths gives a PCP index of ?2.9. Cronstedtite is more abundant in the more altered zones whereas in normal highly altered CM chondrites, with petrologic subtype 2.6-2.0 based on the S/SiO2 and ?FeO/SiO2 ratios in PCP or tochilinite-cronstedtite intergrowths (Rubin et al., 2007), cronstedtite is destroyed by alteration. The matrix in fresh zones has CI chondritic volatile element abundances, but interactions between matrix and chondrules occurred during alteration, modifying the volatile element abundances in the altered zones. Paris has higher trapped Ne contents, more primitive organic compounds, and more primitive organic material than other CMs. There are gradational contacts between domains of different degree of alteration, on the scale of ?1 cm, but also highly altered clasts, suggesting mainly a water-limited style of alteration, with no significant metamorphic reheating.