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Sample records for indarch eh4 chondrite

  1. Evolution of Indarch (EH4 Chondrite) at 1 GPa and High Temperature

    NASA Technical Reports Server (NTRS)

    Berthet, S.; Malavergne, V.; Righter, K.

    2008-01-01

    The chondritic meteorites are materials that are as old as the solar system itself characterized by variations in bulk chemical and oxidation state, and have long been considered possible building blocks that accreted to form the terrestrial inner planets. Enstatite chondrites contain nearly FeO free enstatite, silicon-rich kamacite and various sulfides indicating formation under highly reducing conditions. These materials could have participated in the formation of the Earth. However, "fingerprinting" of meteoritic materials has shown that no known meteoritic class corresponds to a hypothetical bulk Earth composition in every aspect. To derive constraints on early accretion and differentiation processes and possibly resolve the debate on the formation of the Earth, it is required to study experimentally a variety of chondritic materials and investigate their melting relations and elemental partitioning behavior at variable pressure (P), temperature (T) and oxygen fugacities (fO2). Variations in fO2 can indeed change chemical features and phase equilibria dramatically. The P-T phase diagrams of peridotites and carbonaceous chondrites have been extensively studied experimentally up to pressures and temperatures corresponding to the transition zone and lower mantle. Even though partial melting experiments have been conducted at ambient pressure on the enstatite chondrite Indarch, enstatite meteorites have never been experimentally investigated at high PT. The following investigation focuses on the effect of the fO2 on the phase relations of Indarch, an EH4 chondrite.

  2. The Evolution of the EH4 Chondrite Indarch at High Pressure and Temperature: The First Experimental Results

    NASA Technical Reports Server (NTRS)

    Berthet, S.; Malavergne, V.; Righter, K.; Corgne, A.; Combes, R.

    2006-01-01

    Chondrite groups are characterized by variations in bulk composition and oxidation state, illustrating in part heterogeneity in the early solar nebula. Planetary accretion could be explained by at least two different scenarios: the homogeneous [1] and heterogeneous accretion models [2, 3]. In particular, for the formation of the Earth, some studies (e.g. [2, 3]) assume that one component is highly reduced material comparable to enstatite chondrites, devoid of volatile elements but containing all other elements in C1 abundance ratios. To derive constraints on the understanding of early differentiation processes, studies of the silicate phase relations and their interactions with metal, at relevant P-T-fO2, are required. Melting relations and equilibrium partitioning behaviour have been studied on peridotitic and chondritic starting compositions at pressures and temperatures corresponding to the transition zone and lower mantle [4, 5, 6]. However, enstatite chondrites, which are highly reduced primitive meteorites, have not yet been studied experimentally under such conditions. Thus, multianvil experiments have been performed at 20-25 GPa and 2000-2400 C on the EH4 chondrite Indarch.

  3. Partial Melting of the Indarch (EH4) Meteorite : A Textural, Chemical and Phase Relations View of Melting and Melt Migration

    NASA Technical Reports Server (NTRS)

    McCoy, Timothy J.; Dickinson, Tamara L.; Lofgren, Gary E.

    2000-01-01

    To Test whether Aubrites can be formed by melting of enstatite Chondrites and to understand igneous processes at very low oxygen fugacities, we have conducted partial melting experiments on the Indarch (EH4) chondrite at 1000-1500 C. Silicate melting begins at 1000 C. Substantial melt migration occurs at 1300-1400 C and metal migrates out of the silicate change at 1450 C and approx. 50% silicate partial melting. As a group, our experiments contain three immiscible metallic melts 9Si-, and C-rich), two immiscible sulfide melts(Fe-and FeMgMnCa-rich) and Silicate melt. Our partial melting experiments on the Indarch (EH4) enstatite Chondrite suggest that igneous processes at low fO2 exhibit serveral unique features. The complete melting of sulfides at 1000 C suggest that aubritic sulfides are not relicts. Aubritic oldhamite may have crystallized from Ca and S complexed in the silicate melt. Significant metal-sulfide melt migration might occur at relatively low degrees of silicate partial melting. Substantial elemental exchange occurred between different melts (e.g., between sulfide and silicate, Si between silicate and metal), a feature not observed during experiments at higher fO2. This exchange may help explain the formation of aubrites from known enstatite chondrites.

  4. Nonporphyritic chondrules and chondrule fragments in enstatite chondrites: Insights into their origin and secondary processing

    NASA Astrophysics Data System (ADS)

    Varela, M. E.; Sylvester, P.; BrandstäTter, F.; Engler, A.

    2015-08-01

    Sixteen nonporphyritic chondrules and chondrule fragments were studied in polished thin and thick sections in two enstatite chondrites (ECs): twelve objects from unequilibrated EH3 Sahara 97158 and four objects from equilibrated EH4 Indarch. Bulk major element analyses, obtained with electron microprobe analysis (EMPA) and analytical scanning electron microscopy (ASEM), as well as bulk lithophile trace element analyses, determined by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), show that volatile components (K2O + Na2O versus Al2O3) scatter roughly around the CI line, indicating equilibration with the chondritic reservoir. All lithophile trace element abundances in the chondrules from Sahara 97158 and Indarch are within the range of previous analyses of nonporphyritic chondrules in unequilibrated ordinary chondrites (UOCs). The unfractionated (solar-like) Yb/Ce ratio of the studied objects and the mostly unfractionated refractory lithophile trace element (RLTE) abundance patterns indicate an origin by direct condensation. However, the objects possess subchondritic CaO/Al2O3 ratios; superchondritic (Sahara 97158) and subchondritic (Indarch) Yb/Sc ratios; and chondritic-normalized deficits in Nb, Ti, V, and Mn relative to RLTEs. This suggests a unique nebular process for the origin of these ECs, involving elemental fractionation of the solar gas by the removal of oldhamite, niningerite, and/or another phase prior to chondrule condensation. A layered chondrule in Sahara 97158 is strongly depleted in Nb in the core compared to the rim, suggesting that the solar gas was heterogeneous on the time scales of chondrule formation. Late stage metasomatic events produced the compositional diversity of the studied objects by addition of moderately volatile and volatile elements. In the equilibrated Indarch chondrules, this late process has been further disturbed, possibly by a postaccretional process (diffusion?) that preferentially mobilized Rb with

  5. I-Xe ages of enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Hopp, Jens; Trieloff, Mario; Ott, Ulrich

    2016-02-01

    In order to elucidate the early thermal history of enstatite chondrite parent bodies we determined 129I-129Xe whole rock ages of enstatite chondrites (5 EH, 2 EL, one EH impact melt) relative to the Shallowater reference meteorite (4562.3 ± 0.4 Ma, all errors are 1σ). I-Xe ages of both EL6 chondrites (LON 94100: -4.38 ± 0.60 Ma and Neuschwanstein: -3.87 ± 0.73 Ma - negative sign indicates ages younger than Shallowater) agree well with data of other EL6 chondrites. LON 94100 displayed a second isochron at lower temperatures equivalent to a younger age of -5.25 ± 1.17 Ma, perhaps reflecting different retention temperatures of respective carrier phases during sequential cooling. The enstatite chondrites Abee (EH4), Indarch (EH4), EET 96135 (EH4/5) and St. Marks (EH5) encompass a I-Xe age range of +0.57 ± 1.05 Ma (EET 96135 #1) to -0.45 ± 0.72 Ma (Abee), again in agreement with previously reported ages of EH chondrites. Only the age of St. Marks differs strongly from previously reported younger ages, now being more in accordance with other members of the EH clan. The EH3 chondrite Sahara 97096 showed the youngest I-Xe age of -7.87 ± 0.46 Ma distinctly younger than other I-Xe ages of EH chondrites, including other EH3s. Due to the apparent high retention temperature of the I-Xe system in enstatite (estimated >800 °C) this young age implies a later resetting of the I-Xe system by a severe thermal, likely impact-induced, event. The EH impact melt LAP 02225 records a similarly young thermal event. Though no isochron relationship could be established, the data fall within an apparent I-Xe age range of +5 to +15 Ma, similar to Sahara 97096. Overall, EH chondrite parent body experienced a thermal history determined by a complex interplay between impact disturbances and parent body metamorphism.

  6. Search for isotopic anomalies in oldhamite (CaS) from unequilibrated (E3) enstatite chondrites

    NASA Technical Reports Server (NTRS)

    Lundberg, Laura L.; Zinner, Ernst; Crozaz, Ghislaine

    1994-01-01

    The Ca isotopic compositions of 32 oldhamite (CaS) grains from the Qingzhen (EH3), MAC88136 (EL3), and Indarch (EH4) enstatite chondrites were determined by ion microprobe mass spectrometry. Also measured were the S isotopic compositions of eight oldhamite, two niningerite (MgS), and seven troilite (FeS) grains. The S isotopic compositions of all minerals are normal, but oldhamite grains of the first two meteorites exhibit apparent small Ca-48 excesses and deficits that are correlated with isotopic mass fractionation as determined from the Ca-40-Ca-44 pair. The interpretation of these results is complicated by the fact that none of the established mass fractionation laws can account for the data in the Norton County oldhamite standard. The method of analysis is carefully scrutinized for experimental artifacts. Neither interferences nor any known mass frationation effect can satisfactorily explain the observed small deviations from normal isotopic composition. If these are truly isotopic anomalies, they are much smaller than those observed in hibonite. The nucleosynthetic origin of Ca isotopes is discussed.

  7. Occurence and implications of silicon nitride in enstatic chondrites

    NASA Technical Reports Server (NTRS)

    Alexander, C. M. O'D.; Swan, P.; Prombo, C. A.

    1994-01-01

    Silicon nitride Si3N4, has previously been observed to be a common constituent of acid residues of Qingzhen (EH3) and Indarch (EH4). Ion probe analysis of the Si, N and C isotopic compositions of individual Si3N4 grains from Qingzhen and Indarch acid residues suggest most, if not all, grains are Solar System in origin. A few grains have isotopically anomalous C but this is probably due to small presolar SiC grains adhering to them. In situ observations of the Si3N4 in Qingzhen show that it is only present within, and probably exsolved from, host phases which contain elemental Si in solid solution. Thermodynamic calculations suggest that the Si3N4 probably formed during metamorphism and not in the nebula. Thermodynamic calculations also show that sinoite (Si2N2O) and not Si3N4 should be the stable phase during metamorphism. It appears that kinetic factors must have inhibited the formation if sinoite in Qimgzhen and Indarch.

  8. NanoSIMS Isotopic Analysis of Small Presolar SiC Grains from the Murchisonand Indarch Meteorites

    NASA Astrophysics Data System (ADS)

    Amari, S.; Jennings, C.; Nguyen, A.; Stadermann, F. J.; Zinner, E.; Lewis, R. S.

    2002-03-01

    Carbon and N isotopic measurements were made with the NanoSIMS ion microprobe on small (0.25-0.6 µm) presolar SiC grains from the Murchison and Indarch meteorites. Indarch also contains silicon nitride grains with the isotopic signature of mainstream SiC.

  9. 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.

  10. Grain-size distribution and morphology of metal in E-chondrites

    NASA Astrophysics Data System (ADS)

    Easton, A. J.

    1983-03-01

    The size distribution and morphology of metal grains have been examined in 11 sections of types I and II E-chondrites. The changes in the grain-size distribution and morphology of metal grains correspond with the petrologic types and define a series that reflects increase in thermal metamorphism in the following order: type I, Kota Kota-Indarch-South Oman-St. Mark's; and type II, Jajh deh Kot Lalu-Atlanta-Daniel's Kuil-Hvittis-Pillistfer-Khairpur-Blithfield. Concentrations of metal grains adjacent to the perimeters of chondrules are observable throughout the sequence and delineate relic chondritic structure in six of the seven type II E-chondrites; relic structures are absent from Blithfield.

  11. Differences in isotopic composition of carbonaceous components in enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Grady, M. M.; Wright, I. P.; Carr, R. H.; Poths, J.; Pillinger, C. T.

    1988-02-01

    Carbon stable isotopic composition of the major carbonaceous component in enstatite chondrites varies with petrologic type. Investigation of a suite of HF/HCl-resistant residues has shown that this variation is due to an inherent difference in delta(C-13) of the carbon, and is not a result of the presence of small amounts of isotopically anomalous carbon-bearing components. These latter do occur in type EH3 and EH4 chondrites, in concentrations similar to those found in C1 and C2 carbonaceous chondrites. Combustion of the major carbon component (apparently elemental carbon, not necessarily graphite) occurs at relatively higher temperatures in enstatite chondrites of increasing petrologic type. This is considered to reflect an increase in crystallinity or ordering of the carbonaceous component, and is a measure of the degree of thermal processing to which the meteorites have been subjected during accretion and/or metamorphism.

  12. On the siting of noble gases in E-chondrites

    NASA Technical Reports Server (NTRS)

    Crabb, J.; Anders, E.

    1982-01-01

    Fractions of six E-chondrites were separated by density, grain size, and chemical resistance to determine the siting of noble gases. The samples were taken from the Qingzhen (E3), Indarch (E4), Abee and Saint Saveur (E4-5), and Yilmia and North West Forrest (E6) meteorites. The Ar-rich component of the E6s was concentrated in the enstatite-rich fraction. This subsolar component was resistant to HCl and HNO3 treatment, but could be partially dissolved by HF, implying that the subsolar component is located in the enstatite. The noble gases were transported there by metamorphism. Xe-129 was found in the same regions in the E6s, but was in areas associated with chondrules in the E4s. Additionally, the carbon-rich fraction of the E4 sample displayed Xe and Ne/CCF-Xe isotopic ratios similar to that found in C-chondrites. E3 and E4 primordial gases were analogous, with no subsolar contribution.

  13. The Linum chondrite

    NASA Astrophysics Data System (ADS)

    Matthes, J.; Adam, K.

    1988-12-01

    Based on optical microscopy and electron microprobe analysis, the Linum (East Germany) chondrite is classified as an L6b chondrite that contains olivine (Fa24), orthopyroxene (Fs20), clinopyroxene (Wo45En47Fs8), plagioclase (An10Ab84Or6), nickel-iron, troilite, chromite and accessory amounts of chlorapatite and whitlockite.

  14. The Seoni chondrite.

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Mall, A. P.; Lewis, C. F.

    1972-01-01

    Description of the Seoni (India, 1966) chondrite in terms of its mineralogy, bulk chemistry, and sample shape and mass. It is an H6 group ordinary chondrite that contains olivine, orthopyroxene, clinopyroxene, plagioclase, together with chromite, troilite, kamacite, taenite, chlorapatite, and whitlockite. Recrystallization has been quite extensive, as indicated by the presence of a few remnant chondrules, low abundance of clinopyroxene, and relatively high abundance of well formed plagioclase.

  15. 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.

  16. Halogens in CM Chondrites

    NASA Astrophysics Data System (ADS)

    Menard, J. M.; Caron, B.; Jambon, A.; Michel, A.; Villemant, B.

    2013-09-01

    We set up an extraction line of halogens (fluorine, chlorine) by pyrohydrolysis with 50 mg of rock. We analyzed 7 CM2 chondrites found in Antarctica and found that the Cl content of meteorites with an intact fusion crust is higher than those without.

  17. 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

  18. 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.

  19. Evidence against a chondritic Earth.

    PubMed

    Campbell, Ian H; O'Neill, Hugh St C

    2012-03-28

    The (142)Nd/(144)Nd ratio of the Earth is greater than the solar ratio as inferred from chondritic meteorites, which challenges a fundamental assumption of modern geochemistry--that the composition of the silicate Earth is 'chondritic', meaning that it has refractory element ratios identical to those found in chondrites. The popular explanation for this and other paradoxes of mantle geochemistry, a hidden layer deep in the mantle enriched in incompatible elements, is inconsistent with the heat flux carried by mantle plumes. Either the matter from which the Earth formed was not chondritic, or the Earth has lost matter by collisional erosion in the later stages of planet formation.

  20. Micro-X-ray diffraction assessment of shock stage in enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Izawa, Matthew R. M.; Flemming, Roberta L.; Banerjee, Neil R.; McCausland, Philip J. A.

    2011-05-01

    A new method for assessing the shock stage of enstatite chondrites has been developed, using in situ micro-X-ray diffraction (μXRD) to measure the full width at half maximum (FWHMχ) of peak intensity distributed along the direction of the Debye rings, or chi angle (χ), corresponding to individual lattice reflections in two-dimensional XRD patterns. This μXRD technique differs from previous XRD shock characterization methods: it does not require single crystals or powders. In situ μXRD has been applied to polished thin sections and whole-rock meteorite samples. Three frequently observed orthoenstatite reflections were measured: (020), (610), and (131); these were selected as they did not overlap with diffraction lines from other phases. Enstatite chondrites are commonly fine grained, stained or darkened by weathering, shock-induced oxidation, and metal/sulfide inclusions; furthermore, most E chondrites have little olivine or plagioclase. These characteristics inhibit transmitted-light petrography, nevertheless, shock stages have been assigned MacAlpine Hills (MAC) 02837 (EL3) S3, Pecora Escarpment (PCA) 91020 (EL3) S5, MAC 02747 (EL4) S4, Thiel Mountains (TIL) 91714 (EL5) S2, Allan Hills (ALHA) 81021 (EL6) S2, Elephant Moraine (EET) 87746 (EH3) S3, Meteorite Hills (MET) 00783 (EH4) S4, EET 96135 (EH4-5) S2, Lewis Cliff (LEW) 88180 (EH5) S2, Queen Alexandra Range (QUE) 94204 (EH7) S2, LaPaz Icefield (LAP) 02225 (EH impact melt) S1; for the six with published shock stages, there is agreement with the published classification. FWHMχ plotted against petrographic shock stage demonstrates positive linear correlation. FWHMχ ranges corresponding to shock stages were assigned as follows: S1 < 0.7°, S2 = 0.7-1.2°, S3 = 1.2-2.3°, S4 = 2.3-3.5°, S5 > 3.5°, S6—not measured. Slabs of Abee (EH impact-melt breccia), and Northwest Africa (NWA) 2212 (EL6) were examined using μXRD alone; FWHMχ values place both in the S2 range, consistent with literature values. Micro

  1. 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.

  2. A new metal-rich chondrite grouplet

    NASA Astrophysics Data System (ADS)

    Weisberg, Michael K.; Prinz, Martin; Clayton, Robert N.; Mayeda, Toshiko K.; Sugiura, Naoji; Zashu, Shigeo; Ebihara, Mitsuru

    2001-03-01

    A new grouplet of primitive, metal-rich chondrites, here called the CB (bencubbinite) chondrites, has been recognized. It includes Bencubbin, Weatherford, HH 237 and QUE 94411, paired with QUE 94627. Their mineral compositions, as well as their oxygen and nitrogen isotopic compositions, indicate that they are closely related to the CR and CH chondrites, all of which are members of the more inclusive CR clan. CB chondrites have much greater metal/silicate ratios than any other chondrite group, widely increasing the range of metal/silicate fractionation recorded in solar nebular processes. They also have the greatest moderately volatile lithophile element depletions of any chondritic materials. Metal has compositional trends and zoning patterns that suggest a primitive condensation origin, in contrast with metal from other chondrite groups. CB chondrites, as well as other CR clan chondrites, have much heavier nitrogen (higher 15N/14N) than that in other chondrite groups. The primitive characteristics of the CB chondrites suggests that they contain one of the best records of early nebular processes. Another chondrite, GRO 95551, is petrographically similar to the CB chondrites, but its mineral and oxygen and nitrogen isotope compositions indicate that it formed from a different nebular reservoir.

  3. C Chondrite Clasts in H Chondrite Regolith Breccias: Something Different

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E.; Fries, M.; Utas, J.; Chan, Q. H.-S.; Kebukawa, Y.; Steele, A.; Bodnar, R. J.; Ito, M.; Nakashima, D.; Greenwood, R.; Rahman, Z.; Le, L.; Ross, D. K.

    2016-01-01

    Zag (H3-6) and Monahans (1998) (H5) are regolith breccias that contain 4.5 GY old halite crystals which in turn contain abundant inclusions of aqueous fluids, solids and organics [1-4]. We have previously proposed that these halites originated on a hydro-volcanically-active C-class asteroid, probably Ceres [3-7]. We have begun a detailed analysis of the included solids and organics and are re-examining the related carbonaceous (C)) chondrite clast we previously reported in Zag [5-7]. These new investigations will potentially reveal the mineralogy of asteroid Ceres. We report here on potentially identical C chondrite clasts in the H chondrite regolith breccias Tsukuba (H5-6) and Carancas (H4-5). The clast in Tsukuba was known before [8], but the Carancas clast is newly recognized.

  4. 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.

  5. CV and CM chondrite impact melts

    NASA Astrophysics Data System (ADS)

    Lunning, Nicole G.; Corrigan, Catherine M.; McSween, Harry Y.; Tenner, Travis J.; Kita, Noriko T.; Bodnar, Robert J.

    2016-09-01

    Volatile-rich and typically oxidized carbonaceous chondrites, such as CV and CM chondrites, potentially respond to impacts differently than do other chondritic materials. Understanding impact melting of carbonaceous chondrites has been hampered by the dearth of recognized impact melt samples. In this study we identify five carbonaceous chondrite impact melt clasts in three host meteorites: a CV3red chondrite, a CV3oxA chondrite, and a regolithic howardite. The impact melt clasts in these meteorites respectively formed from CV3red chondrite, CV3oxA chondrite, and CM chondrite protoliths. We identified these impact melt clasts and interpreted their precursors based on their texture, mineral chemistry, silicate bulk elemental composition, and in the case of the CM chondrite impact melt clast, in situ measurement of oxygen three-isotope signatures in olivine. These impact melts typically contain euhedral-subhedral olivine microphenocrysts, sometimes with relict cores, in glassy groundmasses. Based on petrography and Raman spectroscopy, four of the impact melt clasts exhibit evidence for volatile loss: these melt clasts either contain vesicles or are depleted in H2O relative to their precursors. Volatile loss (i.e., H2O) may have reduced the redox state of the CM chondrite impact melt clast. The clasts that formed from the more oxidized precursors (CV3oxA and CM chondrites) exhibit phase and bulk silicate elemental compositions consistent with higher intrinsic oxygen fugacities relative to the clast that formed from a more reduced precursor (CV3red chondrite). The mineral chemistries and assemblages of the CV and CM chondrite impact melt clasts identified here provide a template for recognizing carbonaceous chondrite impact melts on the surfaces of asteroids.

  6. 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 μm 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.

  7. Actinide abundances in ordinary chondrites

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Measurements of actinide and light REE (LREE) abundances and of phosphate abundances in equilibrated ordinary chondrites were obtained and were used to define the Pu abundance in the solar system and to determine the degree of variation of actinide and LREE abundances. The results were also used to compare directly the Pu/U ratio with the earlier obtained ratio determined indirectly, as (Pu/Nd)x(Nd/U), assuming that Pu behaves chemically as a LREE. The data, combined with high-accuracy isotope-dilution data from the literature, show that the degree of gram-scale variability of the Th, U, and LREE abundances for equilibrated ordinary chondrites is a factor of 2-3 for absolute abundances and up to 50 percent for relative abundances. The observed variations are interpreted as reflecting the differences in the compositions and/or proportions of solar nebula components accreted to ordinary chondrite parent bodies.

  8. 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].

  9. Metamorphism of CO3 Chondrites: A Carbon and Nitrogen Isotope Study

    NASA Astrophysics Data System (ADS)

    Newton, J.; Arden, J. W.; Pillinger, C. T.

    1992-07-01

    . There is about 26 times as much of this component in Kainsaz as there is in Lance, and an unresolvable amount in Colony. A precombusted HF/HCl residue of Acfer 094 has demonstrated a SiC content of around 7 ppm, equivalent to values expected for CM2's and further questioning the legitimacy of assigning Acfer 094 to the CO3 group. The data acquired so far shows that these meteorites contain diamond with nitrogen concentrations which range between CV3 and CM2 averages. Only the 3.0 subtypes contain silicon carbide. There seems to be a hiatus between subtypes 3.0 and 3.1, where silicon carbide is completely destroyed, and the diamond content is halved. This is analagous to the discontinuity between ordinary chondrite subtypes 3.4 and 3.5 (4), although at a higher metamorphic grade and suggests that silicon carbide is more susceptible to metamorphic destruction under the oxidizing conditions of the CO3 group than diamond. The effect is still not yet understood, but is likely to be an important parameter in distinguishing nebular and parent body effects. The fact that Indarch, a highly reduced enstatite chondrite, shows the opposite effect, i.e. a high SiC-to-diamond ratio clearly has implications for understanding the destruction of presolar grains by metamorphism under different conditions. References 1. Newton, J. et al. (1992) LPSC XXIII 985-986. 2. Scott, E.R.D. & Jones, R.H. (1990) Geochim. Cosmochim. Acta 54 2485-2502. 3. Russell, S.S. et al. (1990) Science 254 1188-1191. 4. Huss, G.R. (1990) Nature 347 159-162. 5. Russell, S.S. et al. (1992) LPSC XXIII 1187-1188.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Shock metamorphism of ordinary chondrites

    NASA Astrophysics Data System (ADS)

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

    1991-12-01

    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.

  15. 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.

  16. Spectral reflectance properties of carbonaceous chondrites: 1. CI chondrites

    NASA Astrophysics Data System (ADS)

    Cloutis, E. A.; Hiroi, T.; Gaffey, M. J.; Alexander, C. M. O.'D.; Mann, P.

    2011-03-01

    Existing reflectance spectra of CI chondrites (18 spectra of 3 CIs) have been augmented with new (18 spectra of 2 CIs) reflectance spectra to ascertain the spectral variability of this meteorite class and provide insights into their spectral properties as a function of grain size, composition, particle packing, and viewing geometry. Particle packing and viewing geometry effects have not previously been examined for CI chondrites. The current analysis is focused on the 0.3-2.5 μm interval, as this region is available for the largest number of CI spectra. Reflectance spectra of powdered CI1 chondrites are uniformly dark (<10% maximum reflectance) but otherwise exhibit a high degree of spectral variability. Overall spectral slopes range from red (increasing reflectance with increasing wavelength) to blue (decreasing reflectance with increasing wavelength). A number of the CI spectra exhibit weak (<5% deep) absorption bands that can be attributed to both phyllosilicates and magnetite. Very weak absorption bands attributable to other CI phases, such as carbonates, sulfates, and organic matter may be present in one or a few spectra, but their identification is not robust. We found that darker spectra are generally correlated with bluer spectral slopes: a behavior most consistent with an increasing abundance of fine-grained magnetite and/or insoluble organic material (IOM), as no other CI opaque phase appears able to produce concurrent darkening and bluing. Magnetite can also explain the presence of an absorption feature near 1 μm in some CI spectra. The most blue-sloped spectra are generally associated with the larger grain size samples. For incidence and emission angles <60°, increasing phase angle results in darker and redder spectra, particularly below ∼1 μm. At high incidence angles (60°), increasing emission angle results in brighter and redder spectra. More densely packed samples and underdense (fluffed) samples show lower overall reflectance than normally

  17. Magnetic record in chondrite meteorites

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    What we know about the magnetic record in chondrite meteorites based on new data and previously published results is summarized. Strips from thin slabs of chondrite meteorites were cut into near cubical subsamples (several mm on edge) numbering approximately 60 to approximately 120 per meteorite. A common orientation was assigned to each subsample from a given meteorite in order to ensure that we could discover the vector makeup of the bulk meteorite. The new data set includes: Shaw (L7), Roy (L5/6), Claytonville (L5), Plainview (H5), Etter (H5), Leoville (C3V), and Allende (C3V). In addition to these new results, literature data of sufficient detail, e.g. Bjurbole (L4), ALH769 (L6), Abee (E4), Allende (C3V), and Olivenza (L5), is considered.

  18. 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.

  19. Zn Isotopes in Chondrites, Chondrules, and Matrix: Origin of the Volatile Element Depletion in Chondrites

    NASA Astrophysics Data System (ADS)

    Moynier, F.; Pringle, E.; Hezel, D.

    2015-07-01

    The variations of Zn isotope ratios among carbonaceous chondrites show that the volatile element depletion in solar system material occurred in the solar nebula. We will also present the Zn isotopic composition of chondrules and matrix from carbonaceous chondrites.

  20. 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.

  1. High-temperature condensates in carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Grossman, L.

    1977-01-01

    Equilibrium thermodynamic calculations of the sequence of condensation of minerals from a cooling gas of solar composition play an important role in explaining the mineralogy and trace element content of different types of inclusions in carbonaceous chondrites. Group IV B iron meteorites and enstatite chondrites may also be direct condensates from the solar nebula. Condensation theory provides a framework within which chemical fractionations between different classes of chondrites may be understood.

  2. 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.

  3. Fluorescent organic matter in carbonaceous chondrites.

    PubMed

    Murae, T

    1999-01-01

    Fluorescent organic matter in carbonaceous chondrites was investigated using a microscope equipped with a fluorescence spectrophotometer. Fluorescent particles were observed in powdered CM2 carbonaceous chondrites (Y-74662, Y-7791198, and Murchison) without carbon enrichment by acid treatments. Although it was difficult to find fluorescent particles in powdered sample of C3 chondrites (ALH-77307, Y-791717, and Allende) without acid treatments, many fluorescent particles were observed after carbon enrichment by acid treatments. Fluorescence of coronene and shock-altered graphite were observed using the same microscope and the same conditions as those for carbonaceous chondrites.

  4. Cosmic-Ray Exposure Ages of Chondrites Collected in Grove Mountains, Antarctica

    NASA Astrophysics Data System (ADS)

    Li, S. J.; Leya, I.; Wang, S. J.; Smith, T.

    2016-08-01

    We reported the cosmic-ray exposure ages of 11 chondrites which were collected from Grove Mountains, Antarctica. These meteorites are 1 CR chondrite, 3 H ordinary chondrites, 6 L ordinary chondrites, and 1 ungrouped chondrite.

  5. Solar gases in meteorites - The origin of chondrites and C1 carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Heymann, D.

    1978-01-01

    Evidence suggesting that chondritic meteorites broke off from parent bodies in earth-crossing orbits is considered. It is suggested that ordinary chondrites have an asteroidal origin, and the possibility that C1 chondrites have a cometary origin is examined. Indications of heavy shock and reheating among L and H chondrites provides support for an asteroidal origin, while the Apollo and Amor objects are too small to be unfragmented asteroids, as proposed in the Anders theory of the origin of gas-rich meteorites. Events associated with the megaregolith are discussed in the framework of the proposed cometary origin of C1 chondrites.

  6. Electrical conductivity of chondritic meteorites

    NASA Technical Reports Server (NTRS)

    Duba, AL; Didwall, E. M.; Burke, G. J.; Sonett, C. P.

    1987-01-01

    The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 orders of magnitude greater than rock forming minerals such as olivine for temperatures up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at the grain boundaries. Much of this carbon is produced by pyrolyzation of hydrocarbons at temperatures in excess of 150 C. As the temperature increases, light hydrocarbons are driven off and a carbon-rich residue or char migrates to the grain boundaries enhancing electrical conductivity. Assuming that carbon was present at the grain boundaries in the material which comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance during a hypothetical T-Tauri phase of the sun. Input conductivity data for the meteorite parent body were the present carbonaceous chondrite values for temperatures up to 840 C and the electrical conductivity values for olivine above 840 C.

  7. Spectral reflectance properties of carbonaceous chondrites: 2. CM chondrites

    NASA Astrophysics Data System (ADS)

    Cloutis, E. A.; Hudon, P.; Hiroi, T.; Gaffey, M. J.; Mann, P.

    2011-11-01

    We have examined the spectral reflectance properties and available modal mineralogies of 39 CM carbonaceous chondrites to determine their range of spectral variability and to diagnose their spectral features. We have also reviewed the published literature on CM mineralogy and subclassification, surveyed the published spectral literature and added new measurements of CM chondrites and relevant end members and mineral mixtures, and measured 11 parameters and searched pair-wise for correlations between all quantities. CM spectra are characterized by overall slopes that can range from modestly blue-sloped to red-sloped, with brighter spectra being generally more red-sloped. Spectral slopes, as measured by the 2.4:0.56 μm and 2.4 μm:visible region peak reflectance ratios, range from 0.90 to 2.32, and 0.81 to 2.24, respectively, with values <1 indicating blue-sloped spectra. Matrix-enriched CM spectra can be even more blue-sloped than bulk samples, with ratios as low as 0.85. There is no apparent correlation between spectral slope and grain size for CM chondrite spectra - both fine-grained powders and chips can exhibit blue-sloped spectra. Maximum reflectance across the 0.3-2.5 μm interval ranges from 2.9% to 20.0%, and from 2.8% to 14.0% at 0.56 μm. Matrix-enriched CM spectra can be darker than bulk samples, with maximum reflectance as low as 2.1%. CM spectra exhibit nearly ubiquitous absorption bands near 0.7, 0.9, and 1.1 μm, with depths up to 12%, and, less commonly, absorption bands in other wavelength regions (e.g., 0.4-0.5, 0.65, 2.2 μm). The depths of the 0.7, 0.9, and 1.1 μm absorption features vary largely in tandem, suggesting a single cause, specifically serpentine-group phyllosilicates. The generally high Fe content, high phyllosilicate abundance relative to mafic silicates, and dual Fe valence state in CM phyllosilicates, all suggest that the phyllosilicates will exhibit strong absorption bands in the 0.7 μm region (due to Fe 3+-Fe 2+ charge

  8. 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.

  9. 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.

  10. Tin in a chondritic interplanetary dust particle

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.

    1989-01-01

    Submicron platey Sn-rich grains are present in chondritic porous interplanetary dust particle (IDP) W7029 A and it is the second occurrence of a tin mineral in a stratospheric micrometeorite. Selected Area Electron Diffraction data for the Sn-rich grains match with Sn2O3 and Sn3O4. The oxide(s) may have formed in the solar nebula when tin metal catalytically supported reduction of CO or during flash heating on atmospheric entry of the IDP. The presence of tin is consistent with enrichments for other volatile trace elements in chondritic IDPs and may signal an emerging trend toward nonchondritic volatile element abundances in chondritic IDPs. The observation confirms small-scale mineralogical heterogeneity in fine-grained chondritic porous interplanetary dust.

  11. 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.

  12. Nitrogen isotope anomalies in primitive ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Sugiura, Naoji; Hashizume, Ko

    1992-07-01

    Large anomalies in nitrogen isotopic composition were found in two type-L3 ordinary chondrites. One of them is isotopically heavy, and the other is isotopically light. The carriers of anomalous nitrogen are partly soluble in HCl. Thus, the anomalies are probably due to new types of presolar grains, although they have not been identified yet. Trapped Ar-36 in these chondrites seems to be associated with this anomalous nitrogen, and may be presolar in origin. The presence of two different nitrogen isotopic anomalies suggests that the parent body of L chondrites, and also the primitive solar nebula, were not homogeneous. Nitrogen isotope anomalies seem to be useful in detecting subdivisions of chemical groups of chondrites.

  13. The Thermal History of Enstatite Chondrites

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

    In an attempt to decipher the complicated thermal history of the enstatite chondrites, the CaS enstatite (Larimer and Buseck, 1974; Fogel et al., 1989), cubic sulfide (Skinner and Luce, 1971) and sphalerite (Kissin, 1989; El Goresy and Ehlers, 1989) systems have been applied, but the results have not been straightforward. The CaS-En thermometer gives metamorphic temperatures which appear reasonable, but which do not correlate well with petrologic type. The cubic sulfides yield reasonable temperatures for the EH chondrites, but the values for EL chondrites are very low. To some extent, the problem has been the lack of low petrologic type EL chondrites. Here we discuss data for the recently discovered EL3 chondrites (Chang et al., 1992) and we examine the applicability of the Fe-Ni-P system for thermometry. The CaS-En thermometer uses three reactions including equilibria between metal, CaS, SiO2, enstatite and FeS. The method is crucially dependent on the activity coefficients for Si and CaSiO3 which are in solid solutions with metal and enstatite, respectively. The cubic sulfide thermometer uses the solubility of FeS in MgS and MnS, while the ZnS thermometer (which is pressure-dependent) uses the solubility of FeS in ZnS. Current equilibration temperature estimates for enstatite chondrites including the EL3 chondrites are listed in Table 1. Table 1. Estimates of equilibration temperatures (degrees C) for enstatite chondrites.* Petrologic type EH EL System 3 4 5 6 3 4 5 6 En-CaS 1030 950 830 - 830 - - 1025 Cubic sulf 400 680 600 - <<400 - - <400 ZnS 410 (1859)+ - - 500 - - 550 Fe-Ni-P <450 500 550 - <<450 - - <450 *Literature data (see text), present data (bold type). +Heavily shocked. In an attempt to use the Fe-Ni-P system as a thermometer for enstatite chondrites, we used the phase diagram of Doan and Goldstein (1970). Like the other systems, this required extrapolation to lower temperatures (Fig. 1). The temperatures calculated from this system mirror those of

  14. 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).

  15. Variations of Chondrite Properties with Heliocentric Distance

    NASA Astrophysics Data System (ADS)

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

    1995-09-01

    There are 12 well-established chondrite groups distinguishable by significant compositional hiatus among their compositional and petrographic characteristics. Because each group represents a different parent asteroid, formed in a distinct nebular region (and/or at a particular time), it is plausible that chondrite properties varied in a smooth fashion with heliocentric distance (HD). Oxidation state. Thermodynamic calculations indicate that the equilibrium FeO/(FeO+MgO) ratio increases with decreasing nebular temperature. Because the nebular temperature gradient decreased with HD, at all times inner nebular regions had a lower oxidation state than more distant regions. If the time of agglomeration increased with HD, outer-solar-system materials generally would have acquired more ferroan compositions. By these criteria we infer that enstatite chondrites formed closer to the Sun, OC at intermediate HD, and R chondrites and carbonaceous chondrites still farther from the Sun. Oxygen isotopic composition. The nearer the Sun, the higher the nebular temperature and the larger the fraction of infalling interstellar material that evaporated; this resulted in greater equilibration with nebular gas and greater isotopic homogeneity. Because the Earth, Moon and EH-EL chondrites lie on the terrestrial fractionation (TF) line on the standard three O-isotope diagram, and martian meteorites (Delta^(17)O=0.36 per mil) and eucrites (Delta^(17)O=-0.40 per mil) lie close to this line, we infer that the mean nebular (i.e., solar) O-isotopic composition was on or near the TF line. At >1 AU the absolute value of Delta^(17)O increased. We infer that EH and EL chondrites formed at a HD <1 AU; H, L and LL chondrites (mean Delta^(17)O = 0.73, 1.07 and 1.26 per mil) formed appreciably beyond Mars' distance of 1.5 AU (probably near 2.5 AU at the 3:1 Jupiter-period resonance); R chondrites (Delta^(17)O ~2.9 per mil) and CR, CM, CO, CV and CK chondrites (Delta^(17)O ~ -1.6, -2.3, -4.5, -3.4 and

  16. Noble gases in E-chondrites

    NASA Technical Reports Server (NTRS)

    Crabb, J.; Anders, E.

    1981-01-01

    The combination of noble gas data for 12 E-chondrites with literature data shows K-Ar ages greater than 4 AE for 14 out of 18 meteorites, while U, Th-He ages are often shorter. Cosmic ray exposure ages are found to differ systematically between types E4 and E6, with the respective, below-16 Myr and above-30 Myr values implying that the E-chondrite parent body predominantly contains a single petrologic type on the 1 km scale of individual impacts in contrast to the mixed parent bodies of the ordinary chondrites. Amounts of planetary gas in E4-E6 chondrites fall in the range for ordinary chondrites of types 4-6, but fail to correlate with petrologic type or volatile trace element contents, in contrast to the ordinary chondrites. Analyses of mineral separates show that the planetary gases are concentrated in an HFand HCl-insoluble mineral, similar to phase Q. The subsolar gases are located in an HCl- and HNO3-resistant phase.

  17. 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.

  18. 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.

  19. Petrology of Amoeboid Olivine Aggregates in 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.

    2016-01-01

    Amoeboid olivine aggregates (AOAs) are important refractory components of carbonaceous chondrites and have been interpreted to represent solar nebular condensates that experienced high-temperature annealing, but largely escaped melting. In addition, because AOAs in primitive chondrites are composed of fine-grained minerals (forsterite, anorthite, spinel) that are easily modified during post crystallization alteration, the mineralogy of AOAs can be used as a sensitive indicator of metamorphic or alteration processes. AOAs in CR chondrites are particularly important because they show little evidence for secondary alteration. In addition, some CR AOAs contain Mn-enriched forsterite (aka low-iron, Mn-enriched or LIME olivine), which is an indicator of nebular formation conditions. Here we report preliminary results of the mineralogy and petrology of AOAs in Antarctic CR chondrites, and compare them to those in other carbonaceous chondrites.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. New Volatile-Rich Clasts from Brecciated Chondrites and Achondrites

    NASA Astrophysics Data System (ADS)

    Patzek, M.; Ebert, S.; Bischoff, A.

    2016-08-01

    New volatile-rich clasts from brecciated chondrites and achondrites have been analyzed. Some share similarities with CM and some with CI chondrites, but mineralogical and chemical differences still exist.

  5. 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

  6. Oxygen isotopic relationships between the LEW85332 carbonaceous chondrite and CR chondrites

    NASA Technical Reports Server (NTRS)

    Prinz, M.; Weisberg, M. K.; Clayton, R. N.; Mayeda, T. K.

    1993-01-01

    LEW85332, originally described as a unique C3 chondrite, was shown to be a C2 chondrite with important linkages to the CR clan. An important petrologic aspect of LEW85332 is that it contains anhydrous chondrules and hydrated matrix, and new oxygen isotopic data on chondrules, matrix and whole rock are consistent with the petrology. Chondrules fall on the equilibrated chondrite line (ECL), with a slope near 1, which goes through ordinary chondrite chondrules. This contrasts with the CR chondrule line which has a lower slope due to hydrated components. LEW85332 chondrules define a new carbonaceous chondrite chondrule line, parallel to the anhydrous CV chondrule line (CCC), consistent with the well-established concept of two oxygen isotopic reservoirs. Matrix and whole rock fall on the CR line. The whole rock composition indicates that the chondrite is dominated by chondrules, and that most of them contain light oxygen similar to that of anhydrous olivine and pyroxene separates in the Renazzo and Al Rais CR chondrites.

  7. Primitive material surviving in chondrites - Matrix

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Barber, D. J.; Alexander, C. M.; Hutchinson, R.; Peck, J. A.

    1988-01-01

    A logical place to search for surviving pristine nebular material is in the fine-grained matrices of ordinary and carbonaceous chondrites of petrographic type 3. Unfortunately, many of these chondrites have experienced brecciation, thermal metamorphism, and aqueous alteration, so that interpreting individual features in terms of specific nebular conditions and/or processes is difficult. It follows that the origin and evolutionary history of such matrix phases are controversial, and a consensus is difficult to define. In this chapter, therefore, after summarizing the salient mineralogical, petrographic, chemical, and isotopic features of matrix in apparently primitive chondrites, an attempt is made to provide an overview both of areas of agreement and of topics that are currently in dispute.

  8. 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.

  9. El Médano 301: A New Forsterite Chondrite

    NASA Astrophysics Data System (ADS)

    Pourkhorsandi, H.; Gattacceca, J.; Devouard, B.; D'Orazio, M.; Rochette, P.; Beck, P.; Valenzuela, M.; Sonzogni, C.

    2016-08-01

    El Médano 301 is a chondrite containing olivine and pyroxene with Mg-rich compositions of Fa3.9 ± 0.4 and Fs13.1 ± 5.7 that are intermediate between other ordinary and enstatite chondrites and related to the "forsterite chondrites."

  10. The matrices of unequilibrated ordinary chondrites - Implications for the origin and history of chondrites

    NASA Technical Reports Server (NTRS)

    Huss, G. R.; Keil, K.; Taylor, G. J.

    1981-01-01

    The matrices of 16 unequilibrated chondrites were examined by optical microscopy, an electron microprobe, and a scanning electron microscope. The fine-grained, opaque, silicate matrix of type 3 unequilibrated chondrites was compositionally, mineralogically, and texturally different from the chondrules and their fragments; it may be the low temperature condensate proposed by Larimer and Anders (1967, 1970). Each meteorite has been metamorphosed by a combination of processes including thermal metamorphism and the passage of shock waves; the appearance of each chondrite results from the temperature and pressure conditions which formed it, and subsequent metamorphic alterations.

  11. Chondrites and the Protoplanetary Disk, Part 2

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Contents include the following: On the Dynamical Evolution of a Nebula and Its Effect on Dust Coagulation and the Formation of Centimeter-sized Particles. The Mineralogy and Grain Properties of the Disk Surfaces in Three Herbig Ae/Be Stars. Astrophysical Observations of Disk Evolution Around Solar Mass Stars. The Systematic Petrology of Chondrites: A Consistent Approach to Assist Classification and Interpretation. Understanding Our Origins: Formation of Sun-like Stars in H II Region Environments. Chondrule Crystallization Experiments. Formation of SiO2-rich Chondrules by Fractional Condensation. Refractory Forsterites from Murchison (CM2) and Yamato 81020 (CO3.0) Chondrites: Cathodoluminescence, Chemical Compositions and Oxygen Isotopes. Apparent I-Xe Cooling Rates of Chondrules Compared with Silicates from the Colomera Iron Meteorite. Chondrule Formation in Planetesimal Bow Shocks: Physical Processes in the Near Vicinity of the Planetesimal. Genetic Relationships Between Chondrules, Rims and Matrix. Chondrite Fractionation was Cosmochemical; Chondrule Fractionation was Geochemical. Chondrule Formation and Accretion of Chondrite Parent Bodies: Environmental Constraints. Amoeboid Olivine Aggregates from the Semarkona LL3.0 Chondrite. The Evolution of Solids in Proto-Planetary Disks. New Nickel Vapor Pressure Measurements: Possible Implications for Nebular Condensates. Chemical, Mineralogical and Isotopic Properties of Chondrules: Clues to Their Origin. Maximal Size of Chondrules in Shock-Wave Heating Model: Stripping of Liquid Surface in Hypersonic Rarefied Gas Flow. The Nature and Origin of Interplanetary Dust: High Temperature Components. Refractory Relic Components in Chondrules from Ordinary Chondrites. Constraints on the Origin of Chondrules and CAIs from Short-lived and Long-lived Radionuclides. The Genetic Relationship Between Refractory Inclusions and Chondrules. Contemporaneous Chondrule Formation Between Ordinary and Carbonaceous Chondrites. Chondrules and

  12. On Type III plessite in chondrites

    NASA Astrophysics Data System (ADS)

    Knox, R., Jr.

    1980-03-01

    Questions are raised concerning the possible sources of heat necessary for converting martensite to coarse Type III plessite in ordinary chondrites. It is suggested that the unusual Type III plesite in the Kingfisher, Oklahoma black chondrite was formed by partial homogenization of preexisting Type III plessite as a result of shock reheating of the metal into the gamma field of the Fe-Ni phase diagram, rather than by decomposition of shock reheated prior martensite in the alpha + gamma field, as originally proposed by Taylor and Heymann. Because martensite is sporadically distributed within Kingfisher plessite it is suggested that microstructures of this kind be called Type II-III plessite.

  13. Nature and origin of C-rich ordinary chondrites and chondritic clasts

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Brearley, A. J.; Keil, K.; Grady, M. M.; Pillinger, C. T.

    1988-01-01

    The abundance and the isotopic compositions of C, O, and noble gases were investigated together with the petrologic characteristics of four carbon-rich ordinary chondrites (Sharps and Allan Hills A77011, A78119, and A81024) and three C-rich chondritic clasts. The results of the analyses suggest that all of the chondrites and clasts analyzed belong to petrologic type 3 and contain abundant carbon-rich aggregates, which, in at least two of these samples, consist of poorly graphitized carbon commonly associated with metallic Fe,Ni. The data also suggest that the four C-rich chondrites originated on the H, L, and LL parental bodies, but that clasts in Dimmitt and Plainview and other regolith breccias may come from different bodies. The results obtained are consistent with the view that graphite is not a common nebular phase.

  14. 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 μm 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

  15. Chemical Variations Among L-Group Chondrites, III. Major Element Variation in L6 Chondrites

    NASA Astrophysics Data System (ADS)

    Dodd, R. T.; Jarosewich, E.

    1981-03-01

    Bulk chemical and mineral analyses of five M chondrites of shock facies d to f bring the number of L6 falls analyzed by Jarosewich to 20 and enable us: 1) to examine the chemical effects of shock melting in chondrites of the same petrologic type that presumably sample a limited strati graphic range in their parent body; and 2) to seek depth-related chemical variations by comparing the compositions of L3 and melt-free L6 chondrites. The mean Fe/Mg, Si/Mg, S/Mg and Ni/Mg ratios of melt-free L6 chondrites (shock facies a to c) are virtually identical to those of L3 chondrites, suggesting that L-group material had the same bulk composition early (L6) and late (L3) in the accretion of the parent body. Wider variations of S/Mg and Ni/Mg in L6 chondrites may signify that L6 material was less well mixed than L3, or that some mobilization of metal and troilite occurred at shock intensities (facies c) too low to melt silicates. L6 chondrites that experienced shock melting of silicates (facies d to f) show wide variations of Fe/Mg, Si/Mg, S/Mg and Ni/Mg. It appears that most of the major element variation in the L-group is tertiary (shock-related) rather than primary (nebular, accretionary) or secondary (metamorphic). There is some evidence that L-group chondrites comprise two subgroups with different Fe/S ratios, but these subgroups are now poorly defined and their significance is unknown.

  16. Spectral reflectance properties of carbonaceous chondrites: 8. “Other” carbonaceous chondrites: CH, ungrouped, polymict, xenolithic inclusions, and R chondrites

    NASA Astrophysics Data System (ADS)

    Cloutis, E. A.; Hudon, P.; Hiroi, T.; Gaffey, M. J.; Mann, P.

    2012-11-01

    We have analyzed reflectance spectra (0.3-2.5 μm) of a number of ungrouped or tentatively grouped carbonaceous chondrites (CCs), possible CC-type xenoliths in an aubrite (Cumberland Falls) and a howardite (PRA 04401), a CH chondrite (PCA 91467), a CC polymict breccia (Kaidun), and some R chondrites. The best approach to analysis relies largely on characterizing spectrally active phases - i.e., those phases that contribute diagnostic absorption features, involving absorption band wavelength position, band depth, shape of absorption features, combined with albedo and spectral slope. Mafic silicate (hydrous and/or anhydrous) absorption features are ubiquitous in the CCs and R chondrites we have examined. Combining information on these features along with albedo and spectral slopes allows reasonable inferences to be made concerning their uniqueness. Reflectance spectra of Coolidge show contributions from both olivine and Fe oxyhydroxides (from terrestrial weathering), and its high reflectance and mafic silicate band depths are consistent with a petrologic grade >3 and inconsistent with CVs. The CC nature of the Cumberland Falls inclusions from spectral analysis is inconclusive, but they do exhibit spectral features consistent with their overall mineralogy. DaG 430, which has petrologic characteristics of both CV and CK chondrites, has a spectrum that is not fully consistent with either group. The spectrum of EET 96029 is consistent with some, but not all CM2 chondrites. GRO 95566, a meteorite with some affinities to CM2s, most resembles the Renazzo CR2 chondrite, consistent with their similar mineralogies, and its spectral properties can be related to its major mineralogic characteristics. Spectra of Kaidun are most consistent with CR chondrites, which form the bulk of this meteorite. The reflectance spectrum of MCY 92005 is consistent with its recent classification as a CM2 chondrite. The R3 chondrite MET 01149 shares many characteristics with CKs, but differs in

  17. Collisional records in LL-chondrites

    NASA Technical Reports Server (NTRS)

    Graf, Thomas; Marti, Kurt

    1994-01-01

    One third of all the LL-chondrites have exposure ages of approx. 15 Ma and were exposed to cosmic rays following a collisional break-up. The probability that the 15-Ma peak represents a random signal is calculated to be less than 2%. Considerably lower probabilities are obtained if only LL5s or subgroups of high Ar-40 retention are used. Furthermore, we show that the peak shape agrees with statistical constraints obtained from multiple analyses of samples from the St. Severin LL6-chondrites. The frequency in and out of the 15-Ma peak varies significantly for different petrographic LL-types. The radiogenic Ar-40 retention systematics (most LL-chondrites retained Ar-40(sub rad) shows that no substantial heat pulse resulted in the 15-Ma collisional event. Interestingly, smaller exposure age clusters at approx. 28 Ma and approx. 40 Ma match up well with clusters in the histogram of L-chondrites. The distribution of LL-exposure ages is not consistent with that expected for a quasi-continuous injection of LL material into a resonance zone of the asteroid belt. The near absence of exposure ages shorter than 8 Ma either indicates a lack of recent collisional events or considerably longer transfer times than inferred from dynamical considerations.

  18. Spectrum of carbonaceous-chondrite fission xenon

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1976-01-01

    Estimations of the fission spectrum in xenon isotopes from the progenitor of the strange carbonaceous-chondrite xenon must take account of p-process nucleosynthesis if the latter is the source of anomalous Xe-124, 126. Sample calculations of the p-process yields illustrate the magnitude of the effect, which can greatly increase the estimated Xe-132 fission yield.

  19. 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.

  20. 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.

  1. Mn-Cr Dating of Enstatite Chondrites

    NASA Astrophysics Data System (ADS)

    Hopp, J.; Trieloff, M.; Storck, J.-C.; Ludwig, T.; Meyer, H. P.; Altherr, R.; El Goresy, A.

    2016-08-01

    We will present new 53Mn-53Cr age data of enstatite chondrites, analysed with the new Cameca 1280 HR ionprobe facility at Heidelberg University, Germany. Excess 53Cr was detected in several sphalerites, which was the major high Mn/Cr target mineral.

  2. 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.

  3. 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.

  4. 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

  5. Physical Property Comparison of Ordinary Chondrite Classes

    NASA Astrophysics Data System (ADS)

    Ostrowski, Daniel; Bryson, Kathryn L.

    2016-10-01

    Measurements of the physical properties of meteorites are essential in helping to determine the physical characteristics of the parent asteroids. Studying of physical properties can provide fundamental information to understand meteoroid behavior in the atmosphere and determine methods to deflect potentially hazardous asteroids. Initial focus of our study is on ordinary chondrites, since they are over 70% of the meteorites.To date we have measured the density (bulk and grain), porosity, thermal emissivity, and acoustic velocity of 7 ordinary chondrites (Tamdakht, Chelyabinsk, and multiple Antarctic meteorites). Each meteorite is first scanned using a 3D laser scanner to determine bulk density. For the other tests 1.5cm cubes are studied. Grain density is determined using gas pycnometer using nitrogen gas. Acoustic velocity, longitudinal and shear wave, are measured using an Olympus 45-MG in single element mode. Thermal emissivity is measured from 20°C up to atmospheric entry temperatures, and is based on average measurements over the wavelength range of 8 to 14μm.Tamdakht's bulk density is that of an average H Chondrite (3-4 g/cm3), while it has a low longitudinal velocity of 3540 m/s compared to the normal rage for H chondrites at 3529-6660 m/s. The velocity is consistent across all three axes in the sample. One possibility is an internal fracture, where part of has been seen on the surface of one of the test cubes. Chelyabinsk and the studied Antarctic meteorites have lower bulk and higher grain densities yielding above average porosities. Tamdakht is on the high end of the emissivity range for H chondrites and Chelyabinsk is on the high end for LL chondrites. Emissivity ranges from 0.985-0.995 at 20°C for the ordinary chondrites studied. Heated samples emissivity decreases slightly, 0.045, from initial 20°C measurement. Between 40-200°C, the emissivity stays fairly constant after decrease from room temperature. BTN 00304 has the highest average over the

  6. The Chondrite Types and Their Origins

    NASA Astrophysics Data System (ADS)

    Wood, J. A.

    2005-12-01

    Recent advances in the dating of ferromagnesian chondrules are summarized, and the conclusion seems unavoidable (the author's earlier convictions notwithstanding) that chondrules comprising a given chondrite are the product of nebular activity extending over a million years or more. Continuing chondrule-forming activity, probably successive shock events, can explain the non-solar major element chemical compositions of the ordinary chondrites (OC): they are the cumulative effect of repeated small changes in the local system composition that accompanied each chondrule- forming event. In particular Fe,Ni metal was increasingly lost from the system with time, presumably by incorporation in planetesimals (most of them unsampled) at the nebular midplane. Fe/Si in the system progressed smoothly with time through values appropriate to the H, L, and LL OC groups. The parent bodies of each of these groups were accreted in a relatively short time, during which Fe/Si was essentially constant, then accretion effectively ceased, probably because the parent body was perturbed into an inclined orbit and no longer spent much time in the chondrule-rich nebular midplane. The perturbations are probably ascribable to the same density waves (gravitational irregularities) that created chondrule-forming shocks. Implementation of this concept is also explored for carbonaceous and enstatite chondrites. Maintenance of the differences in composition of the various chondrite types, which formed at differing radial distances, requires that turbulent diffusion was not effective in the zone of chondrite formation. Instead periodic disturbances by the nebular density waves were probably responsible for remixing solids from the midplane zone into the body of the nebula.

  7. Compositions of three low-FeO ordinary chondrites: Indications of a common origin with the H chondrites

    SciTech Connect

    Troiano, Julianne; Rumble III, Douglas; Rivers, Mark L.; Friedrich, Jon M.

    2011-11-17

    Burnwell, EET 96031, and LAP 04575 are ordinary chondrites (OC) that possess lower than typical olivine Fa content than has been established for the H chondrites (< 17 mol%). Mean low-Ca pyroxene Fs contents are typically lower than mean Fa content, with generally 16 mol% Fs. We have investigated these three low-FeO chondrites by measuring their trace element abundances, oxygen isotopic compositions, and examining their three-dimensional (3D) petrography with synchrotron X-ray microtomography. We compare our results with those established for more common OC. The low FeO chondrites studied here have bulk trace element abundances that are identical to the H chondrites. From bulk oxygen isotopic analysis, we show that Burnwell, EET 96010, and LAP 04757 sampled oxygen reservoirs identical to the H chondrites. Burnwell, EET 96031, and LAP 04575 possess common 3D opaque mineral structures that could be distinct from the H chondrites, as evidenced by X-ray microtomographic analysis, but our comparison suite of H chondrites is small and unrepresentative. Overall, our data suggest a common origin for the low-FeO chondrites Burnwell, EET 96010, and LAP 04757 and the H chondrites. These three samples are simply extreme members of a redox process where a limiting nebular oxidizing agent, probably ice, reacted with material containing slightly higher amounts of metal than typically seen in the H chondrites.

  8. Nucleosynthetic strontium isotope anomalies in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Yokoyama, Tetsuya; Fukami, Yusuke; Okui, Wataru; Ito, Nobuaki; Yamazaki, Hiroshi

    2015-04-01

    Precise Sr isotopic compositions in samples from sequential acid leaching experiments have been determined for three carbonaceous chondrites, Allende, Murchison, and Tagish Lake, together with those in the bulk aliquots of these meteorites. The chondritic acid leachates and residues were characterized by Sr isotope anomalies with variable μ84Sr values (106 relative deviation from a standard material) ranging from +120 to - 4700 ppm, documenting multiple nucleosynthetic sources within a single meteorite. In addition, the μ84Sr patterns across leaching samples for individual chondrites differed from one another. The highest μ84Sr values were observed for leaching Step 3 (HCl+H2O, 75 °C) for Allende and Murchison likely because of the incorporation of calcium and aluminum-rich inclusions (CAIs). In contrast, extremely low μ84Sr values were observed in the later fractions (Steps 6 and 7) for Murchison and Tagish Lake, suggesting the existence of s-process-enriched presolar SiC grains derived from AGB stars. A μ84Sr-ɛ54Cr diagram was prepared with the CAIs and bulk aliquots of carbonaceous chondrites and other meteorites (noncarbonaceous) that were plotted separately; however, they still formed a global positive correlation. CAIs presented the highest μ84Sr and ɛ54Cr values, whereas carbonaceous chondrites and noncarbonaceous meteorites had intermediate and the lowest μ84Sr and ɛ54Cr values, respectively. The positive trend was interpreted as resulting from global thermal processing in which sublimation of high μ84Sr and ɛ54Cr carriers generated the excess μ84Sr and ɛ54Cr signatures in CAIs, while noncarbonaceous planetesimals accreted from materials that underwent significant thermal processing and thus had relatively low μ84Sr and ɛ54Cr values. Apart from the global trend, the carbonaceous chondrites and noncarbonaceous meteorites both exhibited intrinsic variations that highlight an isotopic dichotomy similar to that observed in other isotope

  9. Thermal evolution and sintering of chondritic planetesimals. III. Modelling the heat conductivity of porous chondrite material

    NASA Astrophysics Data System (ADS)

    Henke, Stephan; Gail, Hans-Peter; Trieloff, Mario

    2016-05-01

    Context. The construction of models for the internal constitution and temporal evolution of large planetesimals, which are the parent bodies of chondrites, requires as accurate as possible information on the heat conductivity of the complex mixture of minerals and iron metal found in chondrites. The few empirical data points on the heat conductivity of chondritic material are severely disturbed by impact-induced microcracks modifying the thermal conductivity. Aims: We attempt to evaluate the heat conductivity of chondritic material with theoretical methods. Methods: We derived the average heat conductivity of a multi-component mineral mixture and granular medium from the heat conductivities of its mixture components. We numerically generated random mixtures of solids with chondritic composition and packings of spheres. We solved the heat conduction equation in high spatial resolution for a test cube filled with such matter. We derived the heat conductivity of the mixture from the calculated heat flux through the cube. Results: For H and L chondrites, our results are in accord with empirical thermal conductivity at zero porosity. However, the porosity dependence of heat conductivity of granular material built from chondrules and matrix is at odds with measurements for chondrites, while our calculations are consistent with data for compacted sandstone. The discrepancy is traced back to subsequent shock modification of the currently available meteoritic material resulting from impacts on the parent body over the last 4.5 Ga. This causes a structure of void space made of fractures/cracks, which lowers the thermal conductivity of the medium and acts as a barrier to heat transfer. This structure is different from the structure that probably exists in the pristine material where voids are represented by pores rather than fractures. The results obtained for the heat conductivity of the pristine material are used for calculating models for the evolution of the H chondrite

  10. 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.

  11. Jadeite formation in shocked ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Miyahara, Masaaki; Ozawa, Shin; Ohtani, Eiji; Kimura, Makoto; Kubo, Tomoaki; Sakai, Takeshi; Nagase, Toshiro; Nishijima, Masahiko; Hirao, Naohisa

    2013-07-01

    Albitic feldspar in shocked ordinary chondrites (Yamato 791384 L6 and Yamato 75100 H6) and albite recovered from static high-pressure and high-temperature synthetic experiments (Kubo et al., 2010) were investigated with a transmission electron microscope (TEM) subsequent to a conventional micro-Raman spectroscopy analysis to clarify albite dissociation reaction under high-pressure and high-temperature condition. When jadeite forms from albite, SiO2 phase as a residual phase of albite dissociation reaction should accompany jadeite from the stoichiometry. However, albitic feldspar in and adjacent to shock-melt veins of the shocked chondrites dissociates into jadeite+residual amorphous (or poorly-crystallized) material having varied chemical compositions between jadeite and SiO2 phase. TEM observations of albitic feldspar in the shocked chondrites and albite recovered from the static high-pressure and high-temperature synthetic experiments show that jadeite crystallization is initiated by grain refinement of albite (or albitic feldspar). Nucleation occurs along grain-boundaries or at triple-junctions of the fine-grained albite crystal assemblage. Jadeite crystal starts to grow from the nucleus through grain-boundary diffusion. Considering pressure condition recorded in the shock-melt veins of the shocked chondrites, stishovite is the most likely as a residual SiO2 phase accompanying jadeite. High-pressure and high-temperature condition induced by a dynamic event is very short. Stishovite would be hardy formed through a dynamic event due to sluggish nucleation rate of stishovite compared with that of jadeite, thus leading to induce heterogeneous and incomplete albite dissociation reaction; albite dissociates into jadeite+residual amorphous material.

  12. On the chemical composition of L-chondrites

    NASA Technical Reports Server (NTRS)

    Neal, C. W.; Dodd, R. T.; Jarosewich, E.; Lipschutz, M. E.

    1980-01-01

    Radiochemical neutron activation analysis of Ag, As, Au, Bi, Co, Cs, Ga, In, Rb, Sb, Te, Tl, and Zn and major element data in 14 L4-6 and 3 LL5 chondrites indicates that the L group is unusually variable and may represent at least 2 subgroups differing in formation history. Chemical trends in the S/Fe rich subgroup support textural evidence indicating late loss of a shock formed Fe-Ni-S melt; the S/Fe poor subgroup seemingly reflects nebular fractionation only. Highly mobile In and Zn apparently reflect shock induced loss from L chondrites. However, contrasting chemical trends in several L chondrite sample sets indicate that these meteorites constitute a more irregular sampling of, or more heterogeneous parent material than do carbonaceous or enstatite chondrites. Data for 15 chondrites suggest higher formation temperatures and/or degrees of shock than for LL5 chondrites.

  13. Chemical characteristics and origin of H chondrite regolith breccias

    NASA Technical Reports Server (NTRS)

    Lipschutz, M. E.; Biswas, S.; Mcsween, H. Y., Jr.

    1983-01-01

    Petrologic data and contents of Ag, Bi, Cd, Co, Cs, Ga, In, Rb, Se, Te, Tl and Zn-trace elements spanning the volatility/mobility range-in light and dark portions of H chondrite regolith breccias and L chondrite fragmental breccias are reported. The chemical/petrologic characteristics of H chondrite regolith breccias differ from those of nonbrecciated chondrites or fragmental breccias. Petrologic characteristics and at least some trace element contents of H chondrite regolith breccias reflect primary processes; contents of the most volatile/mobile elements may reflect either primary or secondary processing, possibly within layered H chondrite parent object(s). Chemical/petrologic differences existed in different regions of the parent(s). Regoligh formation and gardening and meteoroid compaction were not so severe as to alter compositions markedly.

  14. 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.

  15. 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.

  16. Neodymium Isotopes in Ordinary Chondrites and the Role of Metamorphism on the Parent Body

    NASA Astrophysics Data System (ADS)

    Armytage, R. M. G.; Debaille, V.

    2016-08-01

    Ordinary chondrites have been proposed as a chondritic isotopic reference value for Earth. We present Nd isotopic data for a suite of ordinary chondrites to investigate the effect of parent body processes on isotopic variability.

  17. Chemistry and oxygen isotopic composition of cluster chondrite clasts and their components in LL3 chondrites

    NASA Astrophysics Data System (ADS)

    Metzler, Knut; Pack, Andreas

    2016-02-01

    Cluster chondrites are characterized by close-fit textures of deformed and indented chondrules, taken as evidence for hot chondrule accretion (Metzler). We investigated seven cluster chondrite clasts from six brecciated LL3 chondrites and measured their bulk oxygen isotopic and chemical composition, including REE, Zr, and Hf. The same parameters were measured in situ on 93 chondrules and 4 interchondrule matrix areas. The CI-normalized REE patterns of the clasts are flat, showing LL-chondritic concentrations. The mean chemical compositions of chondrules in clasts and other LL chondrites are indistinguishable and we conclude that cluster chondrite chondrules are representative of the normal LL chondrule population. Type II chondrules are depleted in MgO, Al2O3 and refractory lithophiles (REE, Zr, Hf) by factors between 0.65 and 0.79 compared to type I chondrules. The chondrule REE patterns are basically flat with slight LREE < HREE fractionations. Many chondrules exhibit negative Eu anomalies while matrix shows a complementary pattern. Chondrules scatter along a correlation line with a slope of 0.63 in the oxygen 3-isotope diagram, interpreted as the result of O-isotope exchange between chondrule melts and 18O-rich nebular components. In one clast, a distinct anticorrelation between chondrule size and δ18O is found, which may indicate a more intense oxygen isotope exchange by smaller chondrules. In some clasts the δ18O values of type I chondrules are correlated with concentrations of SiO2 and MnO and anticorrelated with MgO, possibly due to the admixture of a SiO2- and MnO-rich component to chondrule melts during oxygen isotope exchange. Two chondrules with negative anomalies in Sm, Eu, and Yb were found and may relate their precursors to refractory material known from group III CAIs. Furthermore, three chondrules with strong LREE > HREE and Zr/Hf fractionations were detected, whose formation history remains to be explained.

  18. 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.

  19. The Loop chondrite - Petrology, mineral chemistry, and opaque mineralogy

    NASA Astrophysics Data System (ADS)

    Boctor, N. Z.; Kullerud, G.

    1981-03-01

    The petrography, mineral chemistry, and opaque mineralogy of the Loop chondrite, a meteorite found in Gaines County (Texas) in 1962, are discussed. The investigation confirms Mason's (1975) classification of the meteorite as olivine hypersthene chondrite (L6) and proves that the Loop and the Ashmore are distinct chondrites. Tables setting forth representative analyses of silicates and chromite and of metal and troilite are included. It is found that in comparison with the chromite composition of L6 chondrites given by Bunch et al. (1967), the Loop is slightly more enriched in A12O3 and MgO and slightly depleted in Cr2O3.

  20. 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 δ13C ≈ 25-75‰ and δ18O ≈ 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 (δ18O ≈ 5‰) and the C isotopes were controlled by equilibrium with CO and/or CH4 (δ13C ≈ -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 (δ18O ≈ -5.5‰, and δ13C ≈ -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 (δ13C ≈ 65-80‰) and less altered samples (δ13C ≈ 30-40‰). This bimodality can still be explained by precipitation from fluids with the same isotopic

  1. Formation conditions of igneous regions in ordinary chondrites: Chico, Rose City, and other heavily shocked H and L chondrites

    NASA Astrophysics Data System (ADS)

    Yolcubal, Irfan; Sack, Richard O.; Wang, Ming-Sheng; Lipschutz, Michael E.

    1997-09-01

    We report microprobe and radiochemical neutron activation analysis (RNAA) data for hosts and igneous inclusions in the heavily shocked ordinary chondrites Rose City (H5), Yanzhuang (H6), Farmington (L5), Malakal (L5), Chantonnay (L6), Chico (L6), and Tuan Tuc (L6). Based on these analytical results, equilibrium crystallization calculations [Ghiorso and Sack, 1995], phase equilibrium analysis [e.g., Sack and Ghiorso, 1994a,b; Sack et al., 1994], and experimental cooling rate studies [e.g., Walker et al., 1976], we have assessed the metamorphic and magmatic histories of these seven heavily shocked chondrites. We infer that (1) unfractionated chondritic liquids were intruded to depths >0.1km in the parent asteroid of Rose City; (2) early chondritic liquids experiencing 5-10% olivine fractionation were erupted onto the surface of the parent asteroid(s) of Yanzhuang and Chantonnay; and (3) near-surface crystallization is also indicated for the liquids in Tuan Tuc and Farmington, with Chico and Malakal crystallizing at slightly greater depths. In all but Chantonnay, liquids appear to have derived from melting of chondrite types corresponding to their hosts. In the L chondrite Chantonnay, the intrusive liquids derive from melting an H chondrite source region in which chondritic melts were stored for a sufficient time to produce pigeonite in zoned pyroxene xenocrysts. Heating effects are also reflected in the trace element contents of the chondrites. Our RNAA data for Rose City seem to reflect only the siderophile-lithophile fractionation evident in the metal distribution. The Yanzhuang RNAA data are generally similar to those of other H chondrites: severe shock not involving phase transport seems to leave H chondrites unaffected compositionally. Contents of the four most mobile elements (Cd, Bi, Tl, In) and Cs in Chico indicate loss, so that this assemblage experienced extended, low-temperature cooling after injection of dike material into the Chico host. RNAA data for

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Terrestrial microbes in martian and chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Airieau, S.; Piceno, Y.; Andersen, G.

    2007-08-01

    Good extraterrestrial analogs for microbiology are SNC meteorites as Mars analogs, and chondrites as early planet analogs. Chondrites and SNCs are used to trace processes in the early solar system and on Mars. Yet, questions about terrestrial contamination and its effects on the isotopic, chemical and mineral characteristics often arise. A wide biodiversity was found in 21 chondrites of groups CR, CV, CK, CO from ANSMET, CI and CM Falls, and 8 SNCs. Studies documented the alteration of meteorites by weathering and biology [1]-[6], and during aqueous extraction for oxygen isotopic analysis [7], visible biofilms grew in the meteorite solutions in days. To assess biological isotopic and chemical impacts, cultures were incubated 11 months and analyzed by PCR. The sequences for 2 isolates from EET 87770 and Leoville were of a good quality with long sequence reads. In EET 87770, the closest matches were in the genus Microbacterium. Soil and plant isolates were close relatives by sequence comparison. Bacillus, a common soil bacterial genus, grew in a Leoville culture. All SNCs exhibited biological activity measured independently by LAL but only 1 colony was successfully cultured from grains of the SNC Los Angeles. Isotopic analyses of samples with various amounts of microbial contamination could help quantified isotopic impact of microbes on protoplanetary chemistry in these rocks. References: [1] Gounelle, M.& Zolensky M. (2001) LPS XXXII, Abstract #999. [2] Fries, M. et al. (2005) Meteoritical Society Meeting 68, Abstract # 5201. [3] Burckle, L. H. & Delaney, J. S (1999) Meteoritics & Planet. Sci., 32, 475. [4] Whitby, C. et al. (2000) LPS XXXI, Abstract #1732. [5] Tyra M. et al., (2007) Geochim. Cosmochim. Acta, 71, 782 [6] Toporski, J. & Steele A., (2007) Astrobiology, 7, 389 [7]Airieau, S. et al (2005) Geochim. Cosmochim. Acta, 69, 4166.

  7. 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.%.

  8. Evolutionary history of CI and CM chondrites

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.; Macdougall, J. D.

    1984-01-01

    It is now clear that several different processes have acted upon various components of carbonaceous chondrites, and that at least some of those processes occurred very early in solar system history. Because these meteorites are breccias, petrographic relationships are seldom informative about the order in which those processes took place. Nonetheless, information about such an evolutionary sequence would be of potential value in defining the nature of the source region for these meteorites. Implantation of solar wind derived noble gases into CI magnetite apparently postdated the period of aqueous activity believed to be responsible for magnetite production. Carbonate crystallization roughly coincided with one or more episodes of impact driven brecciation.

  9. 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.

  10. 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].

  11. 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.

  12. Phosphate Minerals in Type 4-6 LL Chondrites: The Nature of Fluids on the LL Chondrite Parent Body

    NASA Astrophysics Data System (ADS)

    Jones, R. H.; McCubbin, F. M.; Dreeland, L.; Guan, Y.

    2011-03-01

    Apatite in the LL chondrites is Cl-rich and extremely dry, with H2O contents <100 ppm. We suggest that this apatite may have a significant oxyapatite component. We infer that very dry, halogen-rich fluids pervaded the LL chondrite parent body.

  13. 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

  14. Manganese chromium isotope systematics of carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Shukolyukov, A.; Lugmair, G. W.

    2006-10-01

    In this article we present the results of Cr isotope investigations of different types of carbonaceous chondrites and of the pallasite Eagle Station. The 53Cr/ 52Cr ratios in the bulk samples of carbonaceous chondrites are correlated with 55Mn/ 52Cr ratios. The slope of the correlation line yields a 53Mn/ 55Mn ratio of (8.5 ± 1.5) × 10 - 6 at the time of Mn/Cr fractionation. Mapping this ratio onto an absolute time scale yields a time for this event of 4568.1 + 0.8/- 1.1 Ma ago. This time is very similar to the formation age of Efremovka CAIs of 4567.2 ± 0.6 Ma [Y. Amelin, A. N. Krot, I. D. Hutcheon, A. A. Ulyanov, Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions, Science 297 (2002) 1678-1683], to a time of the chondrule formation of 4568 ± 1 Ma ago [L.E. Nyquist, D. Lindstrom, D. Mittlefehldt, C.-Y. Shih, H. Wiesmann, S. Wentworth, R. Martinez, Manganese-chromium formation intervals for chondrules from the Bishunpur and Chainpur meteorites, Meteorit. Planet. Sci. 36 (2001) 911-938], which, most likely, constrains early global high-temperature Mn/Cr fractionation in a nebular setting. The bulk samples of carbonaceous chondrites exhibit clear 54Cr excesses ( 54Cr *) that are correlated with the 53Cr excesses ( 53Cr *) and also with Mn/Cr ratios. One possible explanation of this correlation is that 54Cr * is also radiogenic, like 53Cr *, and was formed by the decay of the short-lived parent radionuclide 54Mn. The very short half-life of 54Mn of 312 days would require that both short-lived radionuclides 53Mn and 54Mn were generated locally in spallation reactions during the early period of an active sun. The alternative and possibly more plausible explanation is the heterogeneous addition of presolar material. The presolar component, enriched in 54Cr, is mostly contained in the matrix of carbonaceous chondrites. The relative amount of matrix decreases in the sequence CI > CM > CO,CV. A large proportion of Mn is associated with the matrix while

  15. 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.

  16. 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.

  17. Anomalous REE patterns in unequilibrated enstatite chondrites: Evidence and implications

    NASA Technical Reports Server (NTRS)

    Crozaz, Ghislaine; Hsu, Weibiao

    1993-01-01

    We present here a study of Rare Earth Element (REE) microdistributions in unequilibrated enstatite chondrites (EOC's). Although the whole rock REE contents are similar in both unequilibrated and equilibrated chondrites, the host minerals of these refractory elements are different. In the least equilibrated ordinary chondrites (UOC's), the REE reside mainly in glass whereas, in their more equilibrated counterparts, the bulk of the REE is in calcium phosphate, a metamorphic mineral that formed by oxidation of phosphorous originally contained in metal. In the smaller group of enstatite (E) chondrites, calcium phosphate is absent and the phase that contains the highest REE concentrations is a minor mineral, CaS (oldhamite), which contains approximately 50 percent of the total Ca present. In E chondrites, elements typically considered to be lithophiles (such as Ca and Mn) occur in sulfides rather than silicates. This indicates formation under extremely reducing conditions, thus in a region of the solar nebula distinct from those that supplied the more abundant ordinary and carbonaceous chondrites. Previously, we observed a variety of REE patterns in the oldhamite of UEC's; they range from almost flat to some with pronounced positive Eu and Yb anomalies. Here, we searched for complementary REE patterns in other minerals from E chondrites and found them in the major mineral, enstatite. Whenever Eu and Yb anomalies are present in this mineral, they are always negative.

  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. 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

  20. Chondritic Meteorites: Nebular and Parent-Body Formation Processes

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.; Lindstrom, David (Technical Monitor)

    2002-01-01

    It is important to identify features in chondrites that formed as a result of parent-body modification in order to disentangle nebular and asteroidal processes. However, this task is difficult because unmetamorphosed chondritic meteorites are mixtures of diverse components including various types of chondrules, chondrule fragments, refractory and mafic inclusions, metal-sulfide grains and fine-grained matrix material. Shocked chondrites can contain melt pockets, silicate-darkened material, metal veins, silicate melt veins, and impact-melt-rock clasts. This grant paid for several studies that went far in helping to distinguish primitive nebular features from those produced during asteroidal modification processes.

  1. 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.

  2. 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.

  3. A CM chondrite cluster and CM streams

    NASA Technical Reports Server (NTRS)

    Dodd, R. T.; Lipschutz, M. E.

    1993-01-01

    An elongate year-day concentration of CM meteoroid falls between 1921 and 1969 is inconsistent with a random flux of CM meteoroids and suggests that most or all such meteorites, and perhaps the Kaidun C-E chondrite breccia, resulted from streams of meteoroids in nearly circular, Earth-like orbits. To establish whether the post-1920 cluster might have arisen from random sampling, we determined the year-day distribution of 14 falls between 1879 and 1969 by treating each as the corner of a cell of specified dimensions (e.g. 30 years x 30 days) and calculated how many falls occurred in that cell. We then compared the CM cell distribution with random distributions over the same range of years. The results show that for 30 x 30 and 45 x 45 cells, fewer than 5 percent of random sets match the CM distribution with respect to maximum cell content and number of one-fall cells.

  4. 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.

  5. 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.

  6. Behavior of Chromium in Chondritic Materials

    NASA Astrophysics Data System (ADS)

    Kano, N.; Matsuzaki, H.; Nogami, K.; Imamura, M.

    1996-03-01

    To survey the existence forms and existence patterns of Cr and Ru in high-temperature condensate, we have continued to carry out elemental analyses of primitive meteorites particularly acid insoluble fractions and metal phases from them. In addition, condensation calculation, which assume ideal solid solution in the multicomponent alloy, by using thermodynamic data have been performed. Noting that acid residues would contain the high-temperature condensate component, we considerd chemical compositions of acid residues by relating to the condensation process from the solar nebula. In this paper, we present the representative elemental compositions of some chondritic meteorites and discuss the implications of these data to consider the behavior of Cr in meteoritical samples.

  7. 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.

  8. Petrographic, Chemical and Spectroscopic Data on Thermally Metamorphosed Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Tonui, E. K.; Zolensky, M. E.; Hiroi, T.; Wang, M.-S.; Lipschutz, M. E.

    2002-03-01

    First comprehensive description of aqueous alteration and thermal metamorphism in carbonaceous chondrites. Petrographic evidence has been checked against labile trace element temperatures. Spectroscopic data reveals the level of dehydration and possible relationship to primitive asteroids.

  9. Origin of plagioclase-olivine inclusions in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

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

    1991-02-01

    The origin of plagioclase-olivine inclusions (POIs) from three CV chondrites and one ungrouped chondrite was investigated by examining the chemical, mineralogical, and isotopic characteristics of a group of POIs from these chondrites. Results of these analyses demonstrate that the mixing and the partial melting processes in these inclusions were superimposed on more ancient isotopically heterogeneous material. A comparison of the essential characteristics of POIs and CAIs suggests that the major processes leading to the formation of POIs (such as condensation, dust/gas fractionation, aggregation of chemically and isotopically disparate materials, and partial melting) are common to most CAIs and chondrules. A scenario for the origin of POIs is proposed, showing that the homogeneity of the final assemblage (whether a POI, a CAI, or a chondrite) is primarily a reflection of the thermal history rather than the nature of precursor materials.

  10. 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.

  11. Real-Time Calibration for Rapid Raman Ordinary Chondrite Classification

    NASA Astrophysics Data System (ADS)

    Welzenbach, L. C.

    2016-08-01

    Raman spectroscopy is a classification tool being used by other researchers to classify chondrites from NWA and Antarctica. Neon reference spectrum of sufficient fidelity is taken concurrently to calibrate the spectrum to sub-cm-1 accuracy.

  12. Search for Nucleosynthetic Cadmium Isotope Variations in Bulk Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Toth, E. R.; Schönbächler, M.; Friebel, M.; Fehr, M. A.

    2016-08-01

    New high-precision Cd isotope data will be presented for bulk carbonaceous chondrites, such as Allende and Murchison. Volatile element isotope anomalies and their potential nucleosynthetic sources will be discussed.

  13. Analogues for Wild2: Carbonaceous Chondrites Shot into Aerogel

    NASA Astrophysics Data System (ADS)

    Hicks, L. J.; Bridges, J. C.; MacArthur, J. L.; Wickham-Eade, J. E.; Price, M. C.; Burchell, M. J.; Butterworth, A. L.; Baker, S. H.

    2016-08-01

    Comet Wild2 particles show similarities to carbonaceous chondrites. We compare Wild2 grains to analogue shots of CV3 and CR2 powders in aerogel tracks, using the same techniques, to make accurate comparisons.

  14. Microstructure and Thermal History of Metal Particles in CH Chondrites

    NASA Astrophysics Data System (ADS)

    Goldstein, J. I.; Jones, R. H.; Kotula, P. G.; Michael, J. R.

    2005-03-01

    This paper provides detailed microstructural and microchemical information at the nm to µm scale (SEM, EPMA, TEM, EBSD) for a select suite of metal particles in four CH chondrites, ALH 85085, PAT 91546, Acfer 214, NWA 739.

  15. Refractory Inclusions in Pristine Chondrites: Population Comparisons and Equilibrium Condensates

    NASA Astrophysics Data System (ADS)

    Simon, S. B.

    2016-08-01

    The refractory inclusion populations of two CO3 chondrites, DOM 08006 and MIL 090019, were investigated. In both samples >10% of the inclusions contain grossite, a predicted solar condensate, rare in most inclusion populations but significant here.

  16. 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.

  17. The Kelly chondrite - A parent body surface metabreccia

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Stoeffler, D.

    1974-01-01

    A study of the Kelly chondrite classes it as a monomict breccia rather than a polymict breccia as it was originally described. Microprobe analyses of differently textured clasts are very similar to each other and to well-known LL-type chondrites. Clast and matrix olivine compositions are well within the range of LL-chondrite olivine. A correlation is found between the degree of recrystallization and plagioclase composition. Petrographic observations of shocked, annealed, and unshocked clasts coupled with particle size distribution measurements indicate strongly that Kelly is similar to lunar metabreccias in mode of formation. It is theorized that Kelly is an LL-chondrite parent body metabreccia representing the final accumulation phase of the parent body.

  18. Evaluating the Evidence for Magnetic Dynamocs in Chondritic Parent Bodies

    NASA Astrophysics Data System (ADS)

    Fu, R. R.; Weiss, B. P.; Krot, A. N.; Kehayias, P.; Glenn, D. R.; Fintor, K.; Pál-Molnár, E.; Bryson, J. F. J.; Walsworth, R. L.

    2016-08-01

    We present paleomagnetic data suggesting that the LL chondrite parent body lacked a magnetic dynamos. We then further test the dynamo hypothesis for the CV parent body by mapping magnetization in Kaba.

  19. 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.

  20. 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.

  1. Crustal structure and igneous processes in a chondritic Io

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    1993-03-01

    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.

  2. 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.

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

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.; Bennett, Marvin E., III; Jarosewich, Eugene

    1991-01-01

    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.

  4. Sulfide-rich metallic impact melts from chondritic parent bodies

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Lauretta, Dante S.; Connolly, Harold C. _jr., Jr.; Goreva, Yulia S.; Hill, Dolores H.; Domanik, Ken J.; Berger, Eve L.; Yang, Hexiong; Downs, Robert T.

    2010-05-01

    Sacramento Wash 005 (SaW) 005, Meteorite Hills 00428 (MET) 00428, and Mount Howe 88403 (HOW) 88403 are S-rich Fe,Ni-rich metal meteorites with fine metal structures and homogeneous troilite. We compare them with the H-metal meteorite, Lewis Cliff 88432. Phase diagram analyses suggest that SaW 005, MET 00428, and HOW 88403 were liquids at temperatures above 1350°C. Tridymite in HOW 88403 constrains formation to a high-temperature and low-pressure environment. The morphology of their metal-troilite structures may suggest that MET 00428 cooled the slowest, SaW 005 cooled faster, and HOW 88403 cooled the quickest. SaW 005 and MET 00428 contain H-chondrite like silicates, and SaW 005 contains a chondrule-bearing inclusion that is texturally and compositionally similar to H4 chondrites. The compositional and morphological similarities of SaW 005 and MET 00428 suggest that they are likely the result of impact processing on the H-chondrite parent body. SaW 005 and MET 00428 are the first recognized iron- and sulfide-rich meteorites, which formed by impact on the H-chondrite parent body, which are distinct from the IIE-iron meteorite group. The morphological and chemical differences of HOW 88403 suggest that it is not from the H-chondrite body, although it likely formed during an impact on a chondritic parent body.

  5. 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.

  6. Petrologic study of the Belgica 7904 carbonaceous chondrite - Hydrous alteration, oxygen isotopes, and relationship to CM and CI chondrites

    NASA Technical Reports Server (NTRS)

    Ikeda, Y.; Prinz, M.

    1993-01-01

    The genetic relationships between the petrology, hydration reactions, and isotopic oxygen composition in the Belgica 7904 (B7904) carbonaceous chondrite, and the relationship between B7904 and the CM and CI chondrites were investigated by characterizing seven components separated from B7904. The seven specimens included two partially altered chondrules, two phylosilicate clasts, two olivine fragments, and one matrix sample. The results of the analyses and thermodynamic calculations suggest that CI chondrites may have been produced in a two-stage alteration process from materials similar to that of the B7904 matrix, by reactions with liquid water in their parent body. The common CM chondrites may have undergone aqueous alteration in the parent body, in addition to hydration in the nebula, resulting in two-stage alterations; the parent body may have been different from that of B7904.

  7. 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

  8. 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 Δ17O = -23.4 ± 2.3‰, 2SD) and on a three-isotope oxygen diagram plot along ∼slope-1 line. The only exception is a low-Ca pyroxene-bearing AOA 1-103 that shows a range of Δ17O values, from -24‰ to -13‰. Melilite, grossite, and hibonite in four CAIs within AOAs show no evidence for radiogenic 26Mg excess (δ26Mg). In contrast, anorthite in five out of six AOAs measured has δ26Mg corresponding to the inferred initial 26Al/27Al ratio of (4.3 ± 0.7) × 10-5, (4.2 ± 0.6) × 10-5, (4.0 ± 0.3) × 10-5, (1.7 ± 0.2) × 10-5, and (3.0 ± 2.6) × 10-6. Anorthite in another AOA shows no resolvable δ26Mg excess; an upper limit on the initial 26Al/27Al ratio is 5 × 10-6. We infer that CH AOAs formed by gas-solid condensation and aggregation of the solar nebula condensates (forsterite and Fe,Ni-metal) mixed with the previously formed CAIs. Subsequently they experienced thermal annealing and possibly melting to a small degree in a 16O-rich gaseous reservoir during a brief epoch of CAI formation. The low-Ca pyroxene-bearing AOA 1-103 may have experienced incomplete melting and isotope exchange in an 16O-poor gaseous reservoir. The lack of resolvable δ26Mg excess in melilite, grossite, and

  9. 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

  10. Mineralogy of Carbonaceous Chondrites and ACFER 217 from the Sahara

    NASA Astrophysics Data System (ADS)

    Geiger, T.; Bischoff, A.

    1992-07-01

    Among the approximately 400 meteorites recovered in the past three years in the Sahara at least 19 carbonaceous chondrites exist. Ten paired samples belong to the CR- chondrite Acfer 059/El Djouf 001 which has been recently described (Bischoff et al., 1992a). Three samples (Acfer 182, 207, 214) represent a unique (carbonaceous) chondrite (Bischoff et al., 1992b) that has similarities to ALH 85085 (e.g. Scott, 1988). Here, we describe six unpaired carbonaceous chondrites and Acfer 217, an unusual chondritic breccia. Three chondrites probably belong to the CV- chondrites (Acfer 082, 086, 272) and two to the CO- chondrites (Acfer 202, 243). Acfer 094 has trace element characteristics of a CM-chondrite, but has oxygen isotope ratios different from CM-chondrites (Bischoff et al., 1991). CV-chondrites: Based on the petrography and mineral chemistry Acfer 082 and 086 are typical CV3 chondrites. Large coarse-grained CAIs (especially in Acfer 082), fine- grained spinel-rich and large olivine-rich aggregates, chondrules and fragments are embedded in a fine-grained groundmass mainly consisting of small Fe-rich olivine laths. In Acfer 082 and Acfer 086 the average compositions of matrix olivine are Fa 55 and Fa 40, respectively. Acfer 082 is quite fresh concerning the degree of weathering, whereas Acfer 086 is severely weathered as indicated by the occurrence of abundant calcite filling fractures and pores between the olivine laths of the matrix. Acfer 272 has a mineral chemistry similar to Acfer 082, but is in texture, trace element chemistry (Spettel et al., 1992), and oxygen isotopes (Mayeda and Clayton, pers. communication) different to Acfer 082. Acfer 272 has a densely compacted matrix without individual euhedral to subhedral olivine laths. CO-chondrites: Acfer 202 and 243 consist of abundant porphyritic chondrules, CAIs, olivine-rich inclusions, and fragments embedded in abundant fine-grained matrix. The main component of the matrix is Fe-rich olivine. Matrix olivines

  11. Aqueous Alteration Mineralogy in CM Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Chokai, J.; Zolensky, M.; Le, L.; Nakamura, K.; Mikouchi, T.; Monkawa, A.; Koizumi, E.; Miyamoto, M.

    2004-01-01

    Iron-nickel sulfides are found in most or all solar system environments, and are probably the only minerals found in all extraterrestrial materials on hand. Despite the ubiquity, they have not received the attention they deserve. The most common Fe-Ni sulfides in chondrites are troilite (FeS), pyrrhotite (Fe1- XS) and pentlandite (Fe,Ni)9S8. Troilite is believed to have resulted from sulfidation of metal (Fe-Ni) grains in an H2Scontaining environment. Pyrrhotite is produced when friable troilite grains, which are exfoliated from the metal nucleus, are submitted to continued sulfidation [1]. Some asteroids are known to have experienced aqueous alteration, forming products including new generations of sulfides (pyrrhotite and pentlandite). Pentlandite in particular is known to form during such alteration [1]. However, experimental work by Lauretta has indicated that pentlandite may also have been formed during the initial sulfidation process [2], due to the faster diffusion rate of nickel into the forming sulfide, as compared to iron. Finally, there is considerable evidence [1,3&4] for a family of phases intermediate between pyrrhotite and pentlandite, following the trend of the high temperature monosulfide solid solution [5], something not encountered in terrestrial rocks.

  12. Shock Heating: Effects on Chondritic Material

    NASA Technical Reports Server (NTRS)

    Desch, S. J.; Ciesla, F. J.; Hood, L. L.; Nakamoto, T.

    2004-01-01

    At the 1994 Conference on Chondrules and the Protoplanetary Disk, shock waves were discussed as mechanisms that may have been responsible for forming chondrules, millimeter-sized igneous spheres which are significant components of chondritic meteorites, and references therein]. At the time, shock waves were appealing because they were thought to be brief, repetitive events that were quantitatively shown to be able to rapidly heat silicates to the appropriate temperatures for chondrule formation. Since that meeting, more detailed models for the thermal processing of material in shock waves have been developed. These models have tracked the thermal evolution of the silicates for longer periods of time and found that their cooling rates are also consistent with what has been inferred for chondrules. In addition to the thermal histories of these particles, shock waves may be able to explain a number of other features observed in primitive meteorites. Here, we review the recent work that has been done in studying the interaction of solids with shock waves in the solar nebula.

  13. Chemical studies of H chondrites 8. On contemporary meteoroid streams

    NASA Astrophysics Data System (ADS)

    Wolf, Stephen F.; Wang, Ming-Sheng; Dodd, Robert T.; Lipschutz, Michael E.

    Using date and time of fall and petrographic classification as criteria, many equilibrated H chondrites that fell during September and October from 1812 to the present form four significant clusters, denoted as Cluster 2 through Cluster 5, on day-year plots. Using radiochemical neutron activation analysis, we determined 15 trace elements, U, Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, and In (ordered by increasing putative volatility during nebular condensation), in 27 members of these four clusters. We used model-dependent and model-independent multivariate statistical techniques to compare contents of the 10 most volatile elements separately in the four clusters with those of a 33-member suite of random H chondrite falls (from 1773 to 1970). The Clusters 2 and 5 suites (that fell in September 1880-1991 and October, 1919-1984, respectively), each of which is represented by 10 H chondrite falls, are not compositionally distinguishable from the suite of random falls. However, the 17-member combined suite of Clusters 3 and 4 chondrites (that fell during September-October, 1812-1992) proves compositionally distinguishable from random falls at moderate to strong significance levels of 0.01-0.001. This 17-member suite is less readily distinguished from random falls than are the previously reported suite of Cluster 1 falls (May 1855-1895), or Antarctic H chondrites with nominal terrestrial ages >50kyr, each of which is highly significant at <0.001 levels. All suites are genomict and exhibit a range of cosmic ray exposure ages with a plurality having 6-8 Ma ages. Inconclusive results are obtained in the cases of Clusters 2 and 5. However, three H chondrite suites (Clusters 1, 3, and 4) distinguishable from the random background by one property (time of fall) are also distinguishable by another (contents of volatile trace elements or thermal history). Temporal change of H chondrite sources sampled by Earth are indicated by these data.

  14. Chemical studies of H chondrites 11. Cosmogenic radionuclides in falls

    NASA Astrophysics Data System (ADS)

    Ferko, T. E.; Wang, M.-S.; Lipschutz, M. E.

    2002-10-01

    We measured the long-lived cosmogenic radionuclides 10Be, 26Al, and 36Cl in 47 H chondrite falls: 13 ``Cluster 1'' members, 9 ``Cluster 5'' members, and 25 random falls. From the date and time of fall, Clusters 1 and 5 were previously identified as possible coorbital meteoroid streams with distinctive thermal histories being confirmed by contents of volatile trace elements. Here, we use model data, including a three-radionuclide plot (10Bebulk/26Albulk versus 36Clmetal/26Albulk) and the multivariate statistical techniques of logistic regression and linear discriminant analysis to compare radionuclide levels and their utility to differentiate specific suites from other H chondrites. From our radionuclide results and from noble gas data from other workers, we identified 35 falls with simple irradiation histories and cosmic ray exposure ages >4 Ma. Eight others exhibit evidence for shorter (<=4 Ma) exposure, three of which had complex exposure histories (two having been reported by others previously); three others may have had such a history. In any event, the small proportion of H chondrite falls with complex exposure histories supports recent suggestions that they are not commonly encountered, as earlier workers suggested. Although cosmogenic radionuclides do not differentiate between Cluster 1 and a random set of H chondrites, H chondrites that lost 3He from solar heating are distinguishable from those with normal 3He levels.

  15. 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.

  16. 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 μT 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.

  17. 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.

  18. Description, chemical composition and noble gases of the chondrite Nogata

    NASA Astrophysics Data System (ADS)

    Shima, M.; Murayama, S.; Okada, A.; Yabuki, H.; Takaoka, N.

    1983-06-01

    Microscopic, electron-microprobe, chemical-composition, and noble-gas-isotopic-abundance studies of a 20-g sample of the ordinary chondrite Nogata are reported. The historical report of the fall of the chondrite at Nogata, Japan in the year 861 is supported by C-14 dating of the wooden box in which it has been stored in a Shinto shrine. The measurement data are presented in tables and discussed. Except for a low Fe content, the chemical composition and petrological structure of the chondrite are consistent with an L6 classification. Nogata is found to be more lightly shocked and to contain relatiely more radiogenic and spallogenic noble gases than other L chondrites. The gas-retention ages calculated for Nogata are 4.5 (He-4) and 4.7 (Ar-40) x 10 to the 9th years; the cosmic-ray-exposure age is about 4 x 10 to the 7th years. It is suggested that the metamorphism of the chondrite was completed within about 10 to the 8th years of the formation of its parent body.

  19. Microstructure and thermal history of metal particles in CH chondrites

    NASA Astrophysics Data System (ADS)

    Goldstein, J. I.; Jones, R. H.; Kotula, P. G.; Michael, J. R.

    2007-06-01

    We have studied metal microstructures in four CH chondrites, Patuxent Range (PAT) 91546, Allan Hills (ALH) 85085, Acfer 214, and Northwest Africa (NWA) 739, to examine details of the thermal histories of individual particles. Four types of metal particles are common in all of these chondrites. Zoned and unzoned particles probably formed as condensates from a gas of chondritic composition in a monotonic cooling regime, as has been shown previously. We have demonstrated that these particles were cooled rapidly to temperatures below 500 K after they formed, and that condensation effectively closed around 700 K. Zoned and unzoned particles with exsolution precipitates, predominantly high-Ni taenite, have considerably more complex thermal histories. Precipitates grew in reheating episodes, but the details of the heating events vary among individual grains. Reheating temperatures are typically in the range 800-1000 K. Reheating could have been the result of impact events on the CH parent body. Some particles with precipitates may have been incorporated into chondrules, with further brief heating episodes taking place during chondrule formation. In addition to the four dominant types of metal particles, rare Ni-rich metal particles and Si-rich metal particles indicate that the metal assemblage in CH chondrites was a mixture of material that formed at different redox conditions. Metal in CH chondrites consists of a mechanical mixture of particles that underwent a variety of thermal histories prior to being assembled into the existing brecciated meteorites.

  20. 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?

  1. 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

  2. Evidence for Chemical Variations with Shock Loading in L Chondrite Falls

    NASA Astrophysics Data System (ADS)

    Friedrich, J. M.; Bridges, J. C.; Lipschutz, M. E.

    2002-03-01

    We have analyzed 62 equilibrated L chondrite falls for 51 elements by ICPMS and RNAA. We use our data to identify statistically significant geochemical fractionations in the L chondrite parent(s) resulting from shock related heating episodes.

  3. 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.

  4. In Situ Carbon and Oxygen Isotope Analyses of Calcite in CM1 Chondrites

    NASA Astrophysics Data System (ADS)

    Telus, M.; Alexander, C. M. O.'D.; Wang, J.; Hauri, E. H.

    2016-08-01

    We present results from in situ C and O isotope analyses of calcite from CM1 chondrites. There are large isotope variations on small spatial scales. This provides some insight into the evolution of fluids in chondrite parent bodies.

  5. Pore Water Convection in Carbonaceous Chondrite Planetesimals

    NASA Astrophysics Data System (ADS)

    Travis, B. J.; Schubert, G.

    2004-12-01

    Chondritic meteorites are so named because they nearly all contain chondrules - small spherules of olivine and pyroxene that condensed and crystallized in the solar nebula and then combined with other material to form a matrix. Their parent bodies did not differentiate, i.e., form a crust and a core. Carbonaceous chondrites (CCs) derived from undifferentiated icy planetesimals. Asteroids of the inner solar system are probably present-day representatives of the early planetesimals. CCs exhibit liquid water-rock interactions. CCs contain small but significant amounts of radiogenic elements (e.g., 26Al), sufficient to warm up an initially cold planetesimal. A warmed-up phase could last millions of years. During the warmed-up phase, liquid water will form, and could evolve into a hydrothermal convective flow. Flowing water will affect the evolution of minerals. We report on results of a numerical study of the thermal evolution of CCs, considering the major factors that control heating history and possible flow, namely: permeability, radiogenic element content, and planetesimal radius. We determine the time sequence of thermal processes, length of time for a convective phase and patterns of flow, amount of fluid flow throughout the planetesimals, and sensitivity of evolution to primary parameters. We use the MAGHNUM code to simulate 3-D dynamic freezing and thawing and flow of water in a self-gravitating, permeable spherical body. Governing equations are Darcy's law, mass conservation, energy conservation, and equation of state for water and ice. We have simulated the evolution of heating, melting of ice, subsequent flow and eventual re-freezing for several examples of CC planetesimals. For a reference simulation, we use typical values from meteorite analyses: 20 % porosity, 1 darcy permeability (~10-12 m2), 3x10-8 wt fraction of 26Al, rock density of 3000 kg/m3, rock specific heat of 1000 J/kg/K, body radius of 50 km, solid rock thermal conductivity of 3 W/m/K. For the

  6. A Weathering Scale for the Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Wlotzka, F.

    1993-07-01

    terrestrial ages was shown for meteorite finds from Roosevelt County, New Mexico [1]. In these climatic conditions the weathering grades W2 to W6 develop in the following times: W2, 5000 to 15,000 yr; W3, 15,000 to 30,000 yr; W4, 20,000 to 35,000 yr; W5 and W6, 30,000 to >45,000 yr. Similar terrestrial ages were found for chondrites of these weathering grades from the Lybian and Algerian Sahara [2,3]. Antarctic meteorite finds weather much more slowly. A check of 53 Antarctic ordinary chondrites (of hand specimen weathering categories A to C) showed only 9 of grade W2, the rest being W1. Among the W1s is ALHA77278 (category A) with a terrestrial age of 320,000 yr [4]. References: [1] Jull A. J. T. et al. (1991) LPSC XXII, 665. [2] Jull A. J. T. et al. (1990) GCA, 54, 2895. [3] Jull A. J. T. et al. (1993), this volume. [4] Nishiizumi K. et al. (1989) EPSL, 93, 299.

  7. Magnetic Record of Ordinary Chondrite Chondrules

    NASA Astrophysics Data System (ADS)

    Kohout, T.; Kletetschka, G.

    2007-12-01

    The magnetic record of individual chondrules has been examined on two low-metamorphic grade ordinary chondrites - Bjurböle (L4) and Avanhandava (H4). The chondrule magnetic conglomerate study was done by removing oriented chondrules from the meteorite. The magnetic directions of the chondrules in both meteorites seems to be randomly oriented within both meteorites. The paleofield method based on the REM ratio (NRM/SIRM; Natural Remanent Magnetization / Saturation Isothermal Remanent Magnetization) calibrated for the TRM (Thermal Remanent Magnetization; Kletetschka et al., 2004) magnetization process reveals approximate paleofields between 5 μT and 20 μT (REM ~ 0.002) for Avanhandava chondrules and between 12 μT and 45 μT (REM ˜ 0.0015-0.0048) for Bjurböle chondrules. However, the timing of the magnetizing process remains unclear. The random pattern of the individual chondrule magnetic directions suggest that the chondrules were not remagnetized by recent terrestrial weathering nor by the exposure to the artificial magnetic fields. However the effect of post aggregation metamorphism (reaching 400 - 600°C) and impact related shock demagnetization on the parent body may be responsible for partial or complete loss of the magnetic information carried by the lower coercivity grains. In the case of Avanhandava meteorite this can be observed in the REM ratio. The values of REM ratio calculated in low AF (alternating Field) demagnetizing fields are progressively lower than in the higher AF fields. The Bjurböle meteorite contains significant fraction of the tetrataenite mineral. The origin of tetrataenite is related to the slow ordering of the FeNi lattice at temperatures below ~ 350°C). Thus the origin of tetrataenite must be post-metamorphic ruling out the high temperature TRM scenario. The origin of the magnetization in the Bjurböle chondrules are most likely associated to the post-metamorphic low temperature processes (i.e. electric discharges or impact

  8. Microchondrules in three unequilibrated ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Bigolski, John N.; Weisberg, Michael K.; Connolly, Harold C.; Ebel, Denton S.

    2016-02-01

    We report on a suite of microchondrules from three unequilibrated ordinary chondrites (UOCs). Microchondrules, a subset of chondrules that are ubiquitous components of UOCs, commonly occur in fine-grained chondrule rims, although may also occur within matrix. Microchondrules have a variety of textures: cryptocrystalline, microporphyritic, radial, glassy. In some cases, their textures, and in many cases, their compositions, are similar to their larger host chondrules. Bulk compositions for both chondrule populations frequently overlap. The primary material that composes many of the microchondrules has compositions that are pyroxene-normative and is similar to low-Ca-pyroxene phenocrysts from host chondrules; primary material rarely resembles olivine or plagioclase. Some microchondrules are composed of FeO-rich material that has compositions similar to the bulk submicron fine-grained rim material. These microchondrules, however, are not a common compositional type and probably represent secondary FeO-enrichment. Microchondrules may also be porous, suggestive of degasing to form vesicles. Our work shows that the occurrence of microchondrules in chondrule rims is an important constraint that needs to be considered when evaluating chondrule-forming mechanisms. We propose that microchondrules represent melted portions of the chondrule surfaces and/or the melt products of coagulated dust in the immediate vicinity of the larger chondrules. We suggest that, through recycling events, the outer surfaces of chondrules were heated enough to allow microchondrules to bud off as protuberances and become entrained in the surrounding dusty environment as chondrules were accreting fine-grained rims. Microchondrules are thus byproducts of cyclic processing of chondrules in localized environments. Their occurrence in fine-grained rims represents a snapshot of the chondrule-forming environment. We evaluate mechanisms for microchondrule formation and hypothesize a potential link between

  9. Chondritic xenon in the Earth's mantle.

    PubMed

    Caracausi, Antonio; Avice, Guillaume; Burnard, Peter G; Füri, Evelyn; Marty, Bernard

    2016-05-01

    Noble gas isotopes are powerful tracers of the origins of planetary volatiles, and the accretion and evolution of the Earth. The compositions of magmatic gases provide insights into the evolution of the Earth's mantle and atmosphere. Despite recent analytical progress in the study of planetary materials and mantle-derived gases, the possible dual origin of the planetary gases in the mantle and the atmosphere remains unconstrained. Evidence relating to the relationship between the volatiles within our planet and the potential cosmochemical end-members is scarce. Here we show, using high-precision analysis of magmatic gas from the Eifel volcanic area (in Germany), that the light xenon isotopes identify a chondritic primordial component that differs from the precursor of atmospheric xenon. This is consistent with an asteroidal origin for the volatiles in the Earth's mantle, and indicates that the volatiles in the atmosphere and mantle originated from distinct cosmochemical sources. Furthermore, our data are consistent with the origin of Eifel magmatism being a deep mantle plume. The corresponding mantle source has been isolated from the convective mantle since about 4.45 billion years ago, in agreement with models that predict the early isolation of mantle domains. Xenon isotope systematics support a clear distinction between mid-ocean-ridge and continental or oceanic plume sources, with chemical heterogeneities dating back to the Earth's accretion. The deep reservoir now sampled by the Eifel gas had a lower volatile/refractory (iodine/plutonium) composition than the shallower mantle sampled by mid-ocean-ridge volcanism, highlighting the increasing contribution of volatile-rich material during the first tens of millions of years of terrestrial accretion. PMID:27111512

  10. Chondritic xenon in the Earth's mantle.

    PubMed

    Caracausi, Antonio; Avice, Guillaume; Burnard, Peter G; Füri, Evelyn; Marty, Bernard

    2016-05-01

    Noble gas isotopes are powerful tracers of the origins of planetary volatiles, and the accretion and evolution of the Earth. The compositions of magmatic gases provide insights into the evolution of the Earth's mantle and atmosphere. Despite recent analytical progress in the study of planetary materials and mantle-derived gases, the possible dual origin of the planetary gases in the mantle and the atmosphere remains unconstrained. Evidence relating to the relationship between the volatiles within our planet and the potential cosmochemical end-members is scarce. Here we show, using high-precision analysis of magmatic gas from the Eifel volcanic area (in Germany), that the light xenon isotopes identify a chondritic primordial component that differs from the precursor of atmospheric xenon. This is consistent with an asteroidal origin for the volatiles in the Earth's mantle, and indicates that the volatiles in the atmosphere and mantle originated from distinct cosmochemical sources. Furthermore, our data are consistent with the origin of Eifel magmatism being a deep mantle plume. The corresponding mantle source has been isolated from the convective mantle since about 4.45 billion years ago, in agreement with models that predict the early isolation of mantle domains. Xenon isotope systematics support a clear distinction between mid-ocean-ridge and continental or oceanic plume sources, with chemical heterogeneities dating back to the Earth's accretion. The deep reservoir now sampled by the Eifel gas had a lower volatile/refractory (iodine/plutonium) composition than the shallower mantle sampled by mid-ocean-ridge volcanism, highlighting the increasing contribution of volatile-rich material during the first tens of millions of years of terrestrial accretion.

  11. Phyllosilicates in the Carbonaceous Chondrite Breccia Kaidun

    NASA Astrophysics Data System (ADS)

    Yang, S. V.; Zolensky, M.; Golden, D. C.; Ming, D. W.; Ivanov, A.

    1993-07-01

    Kaidun appears to predominantly be a CR chondrite, containing other diverse components, including enstatite chondrites. Previous observations indicate that the dominant phyllosilicates in Kaidun are serpentine and saponite, suggesting that the Kaidun parent body has undergone aqueous alteration [1]. Phyllosilicates in the smectite group are important in that they act as ion exchangers, which can retain alkali metal, alkaline earth, or ammonium ions in their interlayers in exchangeable form while their structure may contain hydroxyl groups derived from the aqueous alteration process. The purpose of this investigation was to study the layer charge of these smectites and to make an attempt to understand the interlayer chemistry, which was the result of rock-water interaction in its parent body. An alkylammonium method coupled with high-resolution transmission electron microscope (HRTEM) was used to study layer charge and the electron microprobe was used to study the composition and the interlayer chemistry of phyllosilicates. Ultramicrotomed Kaidun matrix samples (on TEEM grids) were pretreated with C12-alkylammonium solutions [2]. This procedure was performed to expand and stabilize the smectite (e.g., saponite) for HRTEM study and permit characterization of the relative charge density of the interlayer sites. This latter feature is a potentially important indicator of the environment of the Kaidun parent body (probably a hydrous asteroid). Recent work by Ming et al. [2] shows that the basal lattice fringes of C12-alkylammonium treated saponites in Kaidun meteorite are typically 1.3-1.4 nm, which indicates low-charged interlayer sites. However, in this study saponites with much larger layer spacing (1.3-2.6 nm, mostly 2 nm) were observed. suggesting the presence of high-charge interlayer sites. Another distinct feature observed in this study is that saponite is clearly the dominant phyllosilicate phase in some Kaidun matrix lithologies, with serpentine being rarely

  12. Multiple impact events recorded in the NWA 7298 H chondrite breccia and the dynamical evolution of an ordinary chondrite asteroid

    NASA Astrophysics Data System (ADS)

    Friedrich, Jon M.; Weisberg, Michael K.; Rivers, Mark L.

    2014-05-01

    The major geologic process that has shaped the asteroids and led to development of their regoliths is impact. Petrofabrics in ordinary chondrites are undoubtedly the result of impact events on their asteroidal parent bodies and the foliation present in a chondrite serves as an enduring record of the magnitude of the most intense compacting event experienced by the material. An overwhelming majority of chondrites have an internally consistent petrofabric contained within the spatial dimensions of the entire rock, including across clasts or different petrographic domains. This indicates that the magnitude of the most recent impact to have affected the assembled chondrite was significant enough to impart a foliation across all lithologies. Information of any previous impacts is largely lost because of the consistent, realigned foliations. We present X-ray microtomography derived 3D petrofabric intensity and orientation data for three lithologies in the NWA 7298 breccia. The internally inconsistent petrofabrics among differing lithologies indicate that the magnitude of the final impact event was smaller than previous ones. This latter case preserves fabric information recorded during previous impacts and allows a more complete interpretation of the impact history of a local region of the asteroidal parent. We used our data to infer the sequence and intensity of distinct impact events affecting the NWA 7298 parent asteroid. We suggest a near-surface impact debris zone on the H chondrite parent asteroid as an origin for NWA 7298. These observations yield new opportunities for investigating and interpreting the dynamic collisional evolution of asteroids.

  13. 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.

  14. Plagioclase-rich inclusions in carbonaceous chondrite meteorites - Liquid condensates?

    NASA Technical Reports Server (NTRS)

    Wark, D. A.

    1987-01-01

    The characteristics and formation of coarse-grained, plagioclase-rich inclusions are investigated. The textures, mineralogical compositions, and initial Al-26/Al-27 ratios for the plagioclase-rich inclusions are described. It is observed that plagioclase-rich inclusions in carbonaceous chondrites are either Ca-Al-rich inclusions (CAIs) composed of 30-60 vol pct anorthite, and less than 35 vol pct Ti-Al-pyroxene and melilite, or CA chondrites composed of plagioclase, pyroxene, olivine, spinel, and melilite. It is observed that CA chondrules are chemically and mineralogically the most similar components shared by carbonaceous and ordinary chondrites. The textural changes observed in the inclusions are examined. The data reveal that the CAIs have three textural groups: coarse anorthite laths, equigranular anorthite and Ti-Al-pyroxene, and lacy Ti-Al-pyroxene and fine-grained anorthite.

  15. Morro do Rocio - an unequilibrated H5 chondrite

    NASA Astrophysics Data System (ADS)

    Fredriksson, K.; Wlotzka, F.

    1985-09-01

    The results of an intensive study of apparently anomalous features of the Morro do Rocio (MDR) chondrite are reported. The examination was undertaken because of the detection of what appeared to be tridymite spherules. Chemical, petrological and mineralogical analyses were performed. The analyses indicated that the features thought to anomalous were in reality artifacts taken out of context. Some olivines and pyroxenes with Fe/Mg ratios which deviated from an equilibrated structure were observed, along with free SiO2 close to the olivine. K-feldspar was found to have separated from the albitic-diopsidic residual glass (or melt). The scale of the observed anomalies was finer than the scale usually used in examining chondrites, implying that chondrites will normally display some anomalies if examined on a fine enough scale.

  16. Shock Classication of Ordinary Chondrites: New Data and Interpretations

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

    Introduction. The recently proposed classification system for shocked chondrites (1) is based on a microscopic survey of 76 non-Antarctic H, L, and LL chondrites. Obviously, a larger database is highly desirable in order to confirm earlier conclusions and to allow for a statistically relevant interpretation of the data. Here, we report the shock classification of an additional 54 ordinary chondrites and summarize implications based on a total of 130 samples. New observations on shock effects. Continued studies of those shock effects in olivine and plagioclase that are indicative of the shock stages S1 - S6 as defined in (1) revealed the following: Planar deformation features in olivine, considered typical of stage S5, occur occasionally in stage S3 and are common in stage S4. In some S4 chondrites plagioclase is not partially isotropic but still birefringent coexisting with a small fraction of S3 olivines. Opaque shock veins occur not only in shock stage S3 and above (1) but have now been found in a few chondrites of shock stage S2. Thermal annealing of shock effects. Planar fractures and planar deformation features in olivine persist up to the temperatures required for recrystallization of olivine (> ca. 900 degrees C). Shock history of breccias. In a number of petrologic types 3 and 4 chondrites without recognizable (polymict) breccia texture, we found chondrules and olivine fragments with different shock histories ranging from S1 to S3. Regolith and fragmental breccias are polymict with regard to lithology and shock. The intensity of the latest shock typically varies from S1 to S4 in the breccias studied so far. Frequency distribution of shock stages. A significant difference between H and L chondrites is emerging in contrast to our previous statistics (1), whereas the conspicuous lack of shock stages S5 and S6 in type 3 and 4 chondrites is clearly confirmed (Fig. 1). Correlation between shock and noble gas content. The concentration of radiogenic argon and of

  17. 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.

  18. Are C1 chondrites chemically fractionated - A trace element study

    NASA Technical Reports Server (NTRS)

    Ebihara, M.; Wolf, R.; Anders, E.

    1982-01-01

    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.

  19. 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.

  20. 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.

  1. 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.

  2. A new kind of primitive chondrite, Allan Hills 85085

    NASA Technical Reports Server (NTRS)

    Scott, Edward R. D.

    1988-01-01

    Allan Hills (ALH) 85085, a chemically and mineralogically unique chondrite whose components have suffered little metamorphism or alteration, is discussed. It is found that ALH 85085 has 4 wt pct chondrules (mean diameter 16 microns), 36 wt pct Fe, Ni, 56 wt pct lithic and mineral silicate fragments, and 2 wt pct trolite. It is suggested that, with the exception of matrix lumps, the components of ALH 85085 formed and accreted in the solar nebula. It is shown that ALH 85085 does not belong to any of the nine chondrite groups and is very different from Kakangari. Similarities between ALH 85085 and Bencubbin and Weatherford suggest that the latter two primitive meteorites may be chondrites with high metal abundances and very large, partly fragmented chondrules.

  3. Elemental Analysis of Carbonaceous Chondrites by Sector Field ICP-MS

    NASA Astrophysics Data System (ADS)

    Braukmüller, N.; Escoube, R.; Münker, C.; Heuser, A.; Wombacher, F.

    2016-08-01

    CM chondrites are analyzed via SF-ICP MS for a comparison of the chemical compositions of antarctic and non-antarctic CM chondrites. Aliquots of Murchison CM2 chondrite powder have been heated in a tube furnace to study the loss of volatile elements.

  4. 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.

  5. Mn-53-Cr-53 Systematics of R-Chondrite NWA 753

    NASA Technical Reports Server (NTRS)

    Jogo, K.; Shih, C-Y.; Reese, Y. D.; Nyquist, L. E.

    2006-01-01

    Chondrules and chondrites are interpreted as objects formed in the early solar system, and it is important to study them in order to elucidate its evolution. Here, we report the study of the Mn-Cr systematics of the R-Chondrite NWA753 and compare the results to other chondrite data. The goal was to determine Cr isotopic and age variations among chondrite groups with different O-isotope signatures. The Mn-53-Cr-53 method as applied to individual chondrules [1] or bulk chondrites [2] is based on the assumption that 53Mn was initially homogeneously distributed in that portion the solar nebula where the chondrules and/or chondrites formed. However, different groups of chondrites formed from regions of different O-isotope compositions. So, different types of chondrites also may have had different initial Mn-53 abundances and/or Cr isotopic compositions. Thus, it is important to determine the Cr isotopic systematics among chondrites from various chondrite groups. We are studying CO-chondrite ALH83108 and Tagish Lake in addition to R-Chondrite NWA753. These meteorites have very distinct O-isotope compositions (Figure 1).

  6. Petrologic and oxygen isotopic study of ALH 85085-like chondrites

    NASA Astrophysics Data System (ADS)

    Prinz, M.; Weisberg, M. K.; Clayton, R. N.; Mayeda, T. K.; Ebihara, M.

    1994-07-01

    Four meteorites (PAT 91546, PCA 91328, PCA 91452, PCA 91467) petrologically similar to ALH 85085 chondrite have now been found. Previous studies of ALH 85085 showed it be a new kind of CR-related microchondrule-bearing chondrite, although one called it a sub-chondrite. The purpose of this study is to learn more about ALH 85085-like meteorites and their relationship to CR and CR-related (LEW 85332, Acfer 182, Bencubbin) chondrites. The methods used included petrology, INA bulk chemical analysis (PAT 91546, PCA 91467), and O isotopic analyses of the whole rocks and separated chondrules and dark inclusions (DIs) from PAT 91546. Since microchondrules and fragments are approximately 20 microns it was necessary to analyze composite samples for O; one was of approximately 100 chondrules, and another was of 5 DIs. Petrologically, the four meteorites are similar to ALH 85085, and there is no basis for determining if all of them, or any combinations, are paired. Mineralogically, olivine and pyroxene are highly magnesian FeNi metal generally has 3-10% Ni, and has a positive Ni-Co correlation similar to that in CR and CR-related chondrites. Refractory inclusions are similar in size to the chondrules and have the following assemblages: (1) hibonite-perovskite, (2) melilite-fassaite-forsterite, (3) grossite (Ca-dialuminate)-melilite-perovskite, (4) spinel-melilite, and (5) spinel-pyroxene aggregates. Chemically, INA analyses indicate that PAT 91546 and PCA 91467 are generally similar to ALH 85085. Oxygen isotopic analyses of the four whole-rock compositions fall along the CR mixing line as does ALH 85085; they are also close to LEW 85332, Acfer 182, and Bencubbin. This supports the concept that these are all CR-related chondrites. Even stronger support is found in the compositions of the chondrules and DIs in PAT 91546, which also plot on or near the CR line.

  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. 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.

  10. Refractory inclusions in the Ornans C30 chondrite

    NASA Technical Reports Server (NTRS)

    Davis, A. M.

    1985-01-01

    Several types of metedorites contain unusual objects 10 micrometers to 2 centimeters across that are enriched in refractory elements such as calcium, aluminum and titanium. These objects, commonly known as refractory inclusions, are most abundant in the meteorites known as carbonaceous chondrites. The refractory inclusions that have been found in the Ornans metedorite, a member of a little-studied group of carbonaceous chondrites are described. Some refractory inclusions in Ornans resemble those found in other meteorites, while others are unlike any seen before. The unusual inclusions in Ornans contain minerals with extraordinary enrichments in highly refractory elements.

  11. Timescales and conditions for the aqueous alteration of chondrites

    NASA Astrophysics Data System (ADS)

    Jilly, Christine E.

    It has become well-recognized that water played a critical role in the early geological evolution of materials through observation of hydrated phases in chondritic meteorites. However, details about the mechanism, timing, and conditions of aqueous alteration are poorly constrained. This dissertation investigates water-driven processes in Renazzo-like (CR) carbonaceous chondrites, with some comparison to the heavily altered and Mighei-like (CM) chondrites. CR chondrites were chosen as the focus of this study, as they are the only chondrite group to range from practically anhydrous to completely hydrated, providing petrographic context for the aqueous alteration process. The central goal of the thesis is to elucidate the complete mechanism of aqueous alteration, from primary anhydrous components to secondary minerals. This research uses a variety of micro-analytical techniques to address three main objectives: 1) to detail the petrographic context, 2) to quantify the onset and duration of alteration using radiometric dating, and 3) to constrain the fluid chemistry and conditions for aqueous alteration. On a microscopic scale, fine-grained matrices and glassy mesostases were the first phases to become altered, allowing for elemental transport over short distances (< 100 microns). As alteration progressed, the iron-metal was oxidized, and silicate phenocrysts were pseudomorphically replaced. 53Mn-53 Cr radiometric dating of secondary carbonates in CR chondrites show that aqueous alteration began quickly after accretion of the parent body, ~4 Myr after the beginning of the Solar System. This is contemporaneous with dolomite formation in the CM chondrite Sutter's Mill and with carbonate formation in other CM chondrites. However, the calcite age from a heavily hydrated CR lithology indicates that late-stage alteration occurred ~12 Myr after the beginning of the Solar System. The oxygen isotopic compositions of magnetite and carbonate minerals reveal that altering fluid

  12. Matrix mineralogy of the Orgueil CI carbonaceous chondrite

    NASA Technical Reports Server (NTRS)

    Tomeoka, Kazushige; Buseck, Peter R.

    1988-01-01

    This paper presents the results of petrographic, SEM, and TEM studies of the matrix minerals in Orgueil. It was found that the matrix consists mainly of Fe-bearing Mg-rich serpentine and saponite, and a poorly crystallized Fe-rich ferrihydrite containing small and varying amounts of S and Ni. The serpentine and saponite, which occur in roughly equal molar proportions, are coherently intergrown and occur mainly in fine phyllosilicates in intimate association with the ferrihydrite. Coarse phylosilicates occur in clusters relatively free of ferrihydrite. The matrix mineralogy of the Orgueil chondrite suggests that Orgueil experienced considerably different alteration conditions than did the CM chondrites.

  13. Carbonaceous Chondrite Fragments in the Polymict Eucrite Yamato 791834

    NASA Technical Reports Server (NTRS)

    Buchanan, P. C.; Zolensky, M. E.

    2003-01-01

    Buchanan et al. and Zolensky et al. described carbonaceous chondrite fragments in a variety of howardites and concluded that the majority are CM2 and CR2 materials. Gounelle et al. also described similar, but very small, fragments in these meteorites. These clasts are important because they represent materials that were in orbital proximity to the HED parent body (4 Vesta) and they may be similar to the primitive materials that originally accreted to form this body. The present study describes two carbonaceous chondrite clasts in the Yamato 791834 (Y791834) polymict eucrite.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. The Aqueous Alteration of CR Chondrites: Experiments and Geochemical Modeling

    NASA Technical Reports Server (NTRS)

    Perronnet, M.; Berger, G.; Zolensky, M. E.; Toplis, M. J.; Kolb, V. M.; Bajagic, M.

    2007-01-01

    CR carbonaceous chondrites are of major interest since they contain some of the most primitive organic matter known. However, aqueous alteration has more or less overprinted their original features in a way that needs to be assessed. This study was initiated by comparing the mineralogy and modal abundances of the most altered CR1 chondrite, GRO 95577, to a less altered CR2. Calculated element distributions imply that GRO 95577 may result from aqueous alteration of Renazzo by an isochemical process on their parent asteroid, whose mineralogical composition was estimated ( Unaltered CR shown included table).

  19. Petrology and classification of the Garraf, Spain chondrite

    NASA Technical Reports Server (NTRS)

    Keil, K.; Conrad, G. H.; King, E. A.; San Miguel, A.

    1986-01-01

    Microscopic and electron microprobe studies indicate that the Garraf meteorite is a highly-recrystallized chondrite of petrologic type 6. Olivine (Fa24.7; PMD 1.1) and low-Ca pyroxene (Fs20.9; PMD 1.1) compositions indicate that it belongs to the L-group. Based on contents of noble gases, pervasive fracturing of silicates, common undulose extinction of olivine and plagioclase, and the lack of melt pockets and maskelynite, Garraf is placed into shock facies b. It is concluded that Garraf is a highly recrystallized L6b chondrite that, after recrystallization, was cataclased and comminuted by shock.

  20. CI chondrite-like clasts in the Nilpena polymict ureilite - Implications for aqueous alteration processes in CI chondrites

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.; Prinz, Martin

    1992-01-01

    Petrographic studies of Nilpena polymict ureilite have revealed the presence of small quantities of carbonaceous chondrite matrix clasts. Detailed electron microprobe and TEM studies show that the chemistry and fine-scale mineralogy of one of these clasts is consistent with CI carbonaceous chondrite matrix. Compared to Orgeuil, the phyllosilicate, sulfide, and oxide mineralogy suggests that the Nilpena clasts may represent a less altered type of CI matrix. It is suggested that increased oxidation and aqueous alteration of Nilpena-type materials could result in the formation of the type of mineral assemblage observed in Orgueil. Increased alteration produces progressive more Mg-rich phyllosilicates and more Fe(3+)-rich iron oxides, such as ferrihydrite. As a function of increased alteration, Ca is also progressively leached from the matrix material to form carbonate veins. The depletion of Ca in CI chondrite matrices suggests the Ivuna and Alais may be intermediate in their degree of alteration to Nilpena and Orgueil.

  1. 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.

  2. 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.

  3. Correlations and zoning patterns of phosphorus and chromium in olivine from H chondrites and the LL chondrite Semarkona

    NASA Astrophysics Data System (ADS)

    McCanta, M. C.; Beckett, J. R.; Stolper, E. M.

    2016-03-01

    Phosphorus zoning is observed in olivines in high-FeO (type IIA) chondrules in H chondrites over the entire range of petrologic grades: H3.1-H6. Features in P concentrations such as oscillatory and sector zoning, and high P cores are present in olivines that are otherwise unzoned in the divalent cations. Aluminum concentrations are low and not significantly associated with P zoning in chondrule olivines. In highly unequilibrated H chondrites, phosphorus zoning is generally positively correlated with Cr. Atomic Cr:P in olivine is roughly 1:1 (3:1 for one zone in one olivine in RC 075), consistent with Cr3+ charge-balancing P5+ substituting for Si4+. Normal igneous zonation involving the dominant chrome species Cr2+ was observed only in the LL3.0 chondrite Semarkona. In more equilibrated chondrites (H3.5-H3.8), Cr spatially correlated with P is occasionally observed but it is diffuse relative to the P zones. In H4-H6 chondrites, P-correlated Cr is absent. One signature of higher metamorphic grades (≥H3.8) is the presence of near matrix olivines that are devoid of P oscillatory zoning. The restriction to relatively high metamorphic grade and to grains near the chondrule-matrix interface suggests that this is a response to metasomatic processes. We also observed P-enriched halos near the chondrule-matrix interface in H3.3-H3.8 chondrites, likely reflecting the loss of P and Ca from mesostasis and precipitation of Ca phosphate near the chondrule surface. These halos are absent in equilibrated chondrites due to coarsening of the phosphate and in unequilibrated chondrites due to low degrees of metasomatism. Olivines in type IA chondrules show none of the P-zoning ubiquitous in type IIA chondrules or terrestrial igneous olivines, likely reflecting sequestration of P in reduced form within metallic alloys and sulfides during melting of type IA chondrules.

  4. 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.

  5. The Evaporation Peculiarities of Ca–Al–Inclusions of Chondrites

    NASA Astrophysics Data System (ADS)

    Yakovlev, O. I.; Shornikov, S. I.

    2016-08-01

    The volatile inversion of SiO2 and MgO at the high-temperature evaporation of Ca–Al–Inclusions of chondrites are explained in the framework of the Korginsky’s theory of the acid-base interaction of components in silicate melts.

  6. Comets, carbonaceous chondrites, and interstellar clouds: Condensation of carbon

    NASA Technical Reports Server (NTRS)

    Field, G. B.

    1979-01-01

    Comets, carbonaceous chondrites, and interstellar clouds are discussed in relation to information on interstellar dust. The formation and presence of carbon in stars, comets, and meteorites is investigated. The existence of graphite in the interstellar medium, though it is predicted from thermodynamic calculations, is questioned and the form of carbon contained in comets is considered.

  7. 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.

  8. 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.

  9. An interplanetary dust particle with links to CI chondrites

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    W7013F5 is a chondritic, hydrated interplanetary dust particle whose composition and mineralogy is nearly identical to that found in the CI chondrites. Transmission electron microscope observations show that the phyllosilicates in W7013F5 consist largely of a coherent undergrowth of Mg-Fe serpentine and Fe-bearing saponite on the unitcell scale. This distinctive intergrowth of phyllosilicates has only been observed previously in the CI chondrites. Other secondary minerals in W7013F5 include Mg-Fe carbonates, magnetite, and pentlandite. The mineral assemblage in W7013F5 is generally not as oxidized as that in the CI chondrites. The presence of kamacite in W7013F5 indicates that the particle is extraterrestrial, and a thin amorphous rim surrounding the particle provides evidence that it is not a piece of a meteorite that fragmented during transit through the atmosphere. The apparent lack of hydrated IDPs with CI mineralogy and chemistry may indicate that CI-type dust-producing asteroids are uncommon in the asteroid belt.

  10. Shock and thermal history of iron and chondritic meteorites

    NASA Astrophysics Data System (ADS)

    Goldstein, Joseph I.

    1994-10-01

    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.

  11. 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.

  12. 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.

  13. Exposure Histories of Seven Ordinary Chondrites with Helium-3 Losses

    NASA Astrophysics Data System (ADS)

    Ma, P.; Herzog, G. F.; Faestermann, T.; Knie, K.; Korschinek, G.; Rugel, G.; Wallner, A.; Schultz, L.; Johnson, J.; Jull, A. J. T.; Fink, D.

    2003-03-01

    Among 7 chondrites with He losses and 21Ne<1E-8 cm3 STP/g, simple cosmic-ray exposure histories are likely for 3 (Daraj 115, Staelldalen, and Ybbsitz) but ambiguous for 4 (ALH 88004, Indio Rico, Markovka, and HaH 002). Daraj 115 may show SCR effects.

  14. 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).

  15. 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.

  16. 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

  17. 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-ω-amino) acids β-alanine, and γ-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-ω-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.

  18. 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.

  19. Bulk Fluorine and Chlorine Contents of Chondritic Meteorites

    NASA Astrophysics Data System (ADS)

    Jones, R. H.; Brearley, A. J.; Lewis, J. A.

    2016-08-01

    Bulk F contents of individual chondrite groups are poorly defined. We reappraise bulk Cl and F contents of OCs, based on modal abundance and compositions of apatite, and propose much lower bulk F abundances for OCs and ECs than commonly used values.

  20. Microscale Distribution of Hydrogen Isotopes in Two Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Young, A. F.; Nittler, L. R.; Alexander, C. M. O'D

    2004-01-01

    Hydrogen isotopes are highly variable among primitive meteorites and interplanetary dust particles (IDPs) [1, 2]. In particular, many primitive objects exhibit D (and N-15) enrichments, relative to terrestrial values, thought to represent partial preservation of presolar material fractionated in molecular clouds. However, the diversity of D/H ratios among IDPs and chondrites indicates a complex history of processing in the solar nebula and on meteorite parent bodies. Deconvolving this record requires identification and characterization of the carriers of D enrichments in different objects. Isotopic imaging has proven to be a powerful method to quantitatively explore the distribution of D/H ratios on a one to several m scale in IDPs [2-4] and the CR chondrite Renazzo [5, 6]. In this study, we have used ion imaging to explore the microscale D/H distribution of two carbonaceous chondrites, Tagish Lake (unique) and Al Rais (CR2). Previous D/H measurements (on a tens of microns scale) of Tagish Lake matrix fragments by Messenger [7] and Engrand et al. [8] have found different results, most likely related to the analytical techniques used. Previous work has also shown a large range of D/H ratios in CR chondrites, including very large variations on a scale of a few microns [5, 6, 9].

  1. 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.

  2. 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.

  3. Chondrules and Opaque Phases in Unequilibrated R Chondrites: A Comprehensive Assessment of Their Formation

    NASA Technical Reports Server (NTRS)

    Miller, K. E.; Lauretta, D. S.; Connolly, H. C., Jr.; Berger, E. L.; Domanik, K.

    2016-01-01

    Equilibrated Rumuruti (R) chondrites record an oxygen fugacity between 0 and 3.5 log units below the fayalite-magnetite-quartz buffer, and a sulfur fugacity (fS2) 2 log units above the iron-troilite buffer. They are more than an order of magnitude more oxidized than the ordinary chondrites [1], and orders of magnitude more sulfidized than solar values. Although the R chondrites have the highest (delta)O-17 value of any meteorites, analyses of unequilibrated R chondrites indicate chondrule formation in an oxygen isotope reservoir similar to that of the ordinary chondrite chondrules. We present the relationship of the R chondrite parent body to pre-accretionary volatiles O and S based on our analyses of unequilibrated R chondrite material in two thin sections from the meteorite Mount Prestrud (PRE) 95404.

  4. Accretional Impact Melt From the L-Chondrite Parent Body

    NASA Astrophysics Data System (ADS)

    Wittmann, A.; Weirich, J. R.; Swindle, T. D.; Rumble, D.; Kring, D. A.

    2009-05-01

    MIL 05029, a unique achondritic Antarctic meteorite with L-chondritic affinity, has a medium-grained, well equilibrated texture of large poikilitic low-Ca pyroxenes that overgrew smaller, euhedral olivines. Plagioclase filled interstitial spaces and has an abundance that is twice that typical for L-chondrites, while Fe-Ni metal and troilite are strongly depleted in that respect. No relic clasts or shock features were found in the thin section analyzed. However, based on its chemical affinity to L-chondrites, MIL 05029 was classified as an impact melt. This is confirmed by its olivine and low-Ca pyroxene compositions, the Co content in Fe-Ni metal, and its oxygen isotopic composition that lies very close to that of L-chondrites. An igneous origin of MIL 05029 cannot be ruled out but would have to be reconciled with thermochronometric constraints for the formation of the ordinary chondrite parent bodies. These studies infer delayed accretion of the parent asteroids of the ordinary chondrites and, thus, insufficient heating from short-lived radiogenic isotopes to produce endogenic magmatism. Metallographic cooling rates of ˜2-22 °C/Ma in the temperature range between ˜700-400°C were determined on five zoned metal particles of MIL 05029. Thermal modeling showed that such cooling rates relate to metamorphic conditions at depths of 5-12 km on the L-chondrite parent body. For an impact to deposit material at this depth, scaling relationships for an impact event on the 100-200 km diameter parent asteroid require a 15 to 60 km diameter simple crater that produced a basal melt pool, in which MIL 05029 crystallized. Further constraints for the formation conditions of MIL 05029 were derived from three whole-rock samples that gave well-defined Ar-Ar plateau ages of 4.53±0.02 Ga. This age indicates the time at which MIL 05029 cooled below ˜180°C, the Ar-closure temperature of plagioclase. Considering its slow metallographic cooling, the impact event that formed MIL 05029

  5. 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

  6. 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

  7. Impact cratering on the H chondrite parent asteroid

    NASA Astrophysics Data System (ADS)

    Wittmann, Axel; Swindle, Timothy D.; Cheek, Leah C.; Frank, Elizabeth A.; Kring, David A.

    2010-07-01

    This paper reports petrological data for LaPaz Icefield 02240, 03922, 031125, 031173, 031308, 04462, and 04751, which are meteoritic samples of clast-rich impact melt rocks from the H chondrite parent asteroid. The size distribution and metallographic characteristics of Fe-Ni metal in the melts indicate very rapid 1 to 40°C/s cooling in the temperature range between >1500 and ˜950°C when the clast-melt mixtures were thermally equilibrating. Cooling slowed to values between 10-3 and 10-2°C/s in the temperature range between 700 and 400°C when the melt rocks were cooling to their surroundings. These data suggest that the rocks cooled near the surface of the H chondrite asteroid within suevitic impact deposits. Integrating these data with the petrologic characteristics of other H chondrite melt rocks and their radioisotopic ages indicates that the H chondrite asteroid suffered at least one large impact event while still cooling from endogenous metamorphism at ˜4500 Ma; this impact must have degraded the asteroid's integrity but did not cause shattering. Impact events in the era between ˜4100 and ˜3600 Ma produced melt volumes large enough to allow segregation of metal and troilite from silicate melts, possibly within continuous impact melt sheets contained in craters. The impact record after 3600 Ma does not display such assemblages, which suggests a decrease in the rate of large impact events or a catastrophic size reduction of the H chondrite parent asteroid at around this time.

  8. 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.

  9. Did Ordinary Chondrite Impactors Deliver Olivine to Vesta?

    NASA Astrophysics Data System (ADS)

    Le Corre, Lucille; Reddy, Vishnu; Sanchez, Juan A.; Cloutis, Edward A.; Izawa, Matthew R.; Mann, Paul

    2014-11-01

    Ground-based and Hubble Space Telescope observations of asteroid Vesta suggested the presence of olivine. However, subsequent analysis of data from NASA’s Dawn mission proved that this “olivine-bearing unit”, identified as Oppia crater and its ejecta blanket, was composed of HED impact melt rather than olivine. The lack of widespread olivine in the 19 km deep Rheasilvia basin on the South Pole suggests that the crust-mantle boundary was not breached during the formation of the basin, and that Vesta’s crust is thicker than originally anticipated. Recently, local-scale olivine units have been reported in the walls and ejecta of two craters, Arruntia and Bellicia, located in the northern hemisphere of Vesta, 350-430 km from the Rheasilvia basin (Ammannito et al., 2013). These units were interpreted as exposed plutons by Clenet et al. (2014) rather than of mantle origin excavated during the formation of the Rheasilvia basin. We explored alternative sources for these olivine-rich units by reanalyzing the data published by Ammannito et al. (2013). Our mineralogical analysis gives olivine abundance between 70-80 vol.% consistent with those obtained previously (>60%). The pyroxene ferrosilite content and olivine abundance of the olivine-rich units are similar to ordinary chondrites. Meteoritic evidence suggests contamination of HEDs by several ordinary chondrite impactors including H, L and LL chondrites. This includes howardite JaH 556, which contains ~20 vol.% H chondrite material mixed with HED impact melt. Based on the non-diagnostic curve match and detailed mineralogical analysis using diagnostic spectral band parameters, we conclude that the olivine units in the northern hemisphere of Vesta could be explained by the delivery of exogenic H/L chondrite material rather than being a product of planetary differentiation.

  10. 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.

  11. The chondrite Senboku: Is this the same fall as Shiraiwa?

    NASA Astrophysics Data System (ADS)

    Shima, M.; Honda, M.; Okada, A.; Miura, Y. N.; Ebihara, M.

    1994-07-01

    A stone has been kept in a household altar of the Suda family in Takanashi, Senboku-machi, Senboku-gun, Akita-ken, Japan. The stone came from the sky into the chestnut grove in the dry Maruko river bed. The chondrite Shiraiwa was found in 1920 at approximately 60 cm depth under the field behind a Gosha shrine, at Shiraiwa, Kakunodate-machi, Senboku-gun, Akita-ken, Japan. We have checked the two chondrites to see whether they are from the same fall or not because Senboku and Shiraiwa are the only meteorites found in Akita-ken, and were found only 17 km apart; the time of fall of both are unknown; and both chondrites belong to the H group. Because both chondrites fell more than 70 years ago, cosmogenic radioactive nuclides other than Al-26 were not detected. Aluminum-26 data in both chondrites were compared with a gamma ray standard in respective samples. Obtained results are as follows: Shiraiwa 41.5 +/- 5.3 and Senboku 51.4 +/- 2.6. The concentration and isotopic composition of noble gases of Senboku were determined and compared with that of Shiraiwa. Production rates for He-3 and Ne-21 by Eugster and that for Ar-38 by Schultz et al. were used for age calculation. Although Shiraiwa has data by M. Watanabe as well as by Saga and Kano, who classified it as H4, we are now looking at their data for comparison. For Senboku, we have determined 30 grains of olivine and 40 grains of orthopyroxene and obtained mean Fa and Fs ratios by atomic percent as 18.4 +/- 0.5 and 16.3 +/- 0.6 respectively. From the presence of colorless clear plagioclase in matrix, Senboku was classified as H6. From the results, we have concluded that Shiraiwa and Senboku are completely different falls.

  12. Origin and chronology of chondritic components: A review

    NASA Astrophysics Data System (ADS)

    Krot, A. N.; Amelin, Y.; Bland, P.; Ciesla, F. J.; Connelly, J.; Davis, A. M.; Huss, G. R.; Hutcheon, I. D.; Makide, K.; Nagashima, K.; Nyquist, L. E.; Russell, S. S.; Scott, E. R. D.; Thrane, K.; Yurimoto, H.; Yin, Q.-Z.

    2009-09-01

    Mineralogical observations, chemical and oxygen-isotope compositions, absolute 207Pb- 206Pb ages and short-lived isotope systematics ( 7Be- 7Li, 10Be- 10B, 26Al- 26Mg, 36Cl- 36S, 41Ca- 41K, 53Mn- 53Cr, 60Fe- 60Ni, 182Hf- 182W) of refractory inclusions [Ca,Al-rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs)], chondrules and matrices from primitive (unmetamorphosed) chondrites are reviewed in an attempt to test (i) the x-wind model vs. the shock-wave model of the origin of chondritic components and (ii) irradiation vs. stellar origin of short-lived radionuclides. The data reviewed are consistent with an external, stellar origin for most short-lived radionuclides ( 7Be, 10Be, and 36Cl are important exceptions) and a shock-wave model for chondrule formation, and provide a sound basis for early Solar System chronology. They are inconsistent with the x-wind model for the origin of chondritic components and a local, irradiation origin of 26Al, 41Ca, and 53Mn. 10Be is heterogeneously distributed among CAIs, indicating its formation by local irradiation and precluding its use for the early solar system chronology. 41Ca- 41K, and 60Fe- 60Ni systematics are important for understanding the astrophysical setting of Solar System formation and origin of short-lived radionuclides, but so far have limited implications for the chronology of chondritic components. The chronological significance of oxygen-isotope compositions of chondritic components is limited. The following general picture of formation of chondritic components is inferred. CAIs and AOAs were the first solids formed in the solar nebula ˜4567-4568 Myr ago, possibly within a period of <0.1 Myr, when the Sun was an infalling (class 0) and evolved (class I) protostar. They formed during multiple transient heating events in nebular region(s) with high ambient temperature (at or above condensation temperature of forsterite), either throughout the inner protoplanetary disk (1-4 AU) or in a localized region

  13. LEW85332: A C2 Chondrite in the CR Clan

    NASA Astrophysics Data System (ADS)

    Prinz, M.; Weisberg, M. K.; Brearley, A.; Grady, M. M.; Pillinger, C.; Clayton, R. N.; Mayeda, T. K.

    1992-07-01

    Introduction. LEW85332 was described as a unique C3 chondrite [1] and we undertook this study to learn more about its relationship to other carbonaceous chondrites. We find it to be a C2 chondrite with significant similarites to CR2 chondrites. This linkage extends to the ALH85085 [2] and Acfer 182 [3,4] chondrites, although there are some important differences among them. Petrologic and isotopic similarities define the CR clan, which consists of CR chondrites and their three relatives noted above (and Bencubbin). Some differences are due to major component abundances (chondrules, matrix, metal), and some to minor differences between components, but the similarities are greater and define the clan. Results. Petrogically, LEW85332 has over 60% (vol) chondrules, about 30% matrix and matrix clasts, and about 4-7% metal. Extensive weathering makes modal abundances uncertain. Chondrules are anhydrous, about 170 micrometers wide [1] and of all textural types. ALH85085 chondrules average 20 micrometers and are mainly pyroxene-rich, whereas Acfer 182 is more like LEW85332. Matrix is hydrous and occurs as interstitial matrix, matrix clasts, and chondrule rims [5]. The matrix contains phyllosilicates and magnetite framboids. Matrix clasts are not foreign [1], but part of the chondrite, making it C2. This is also the case for Acfer 182 [3], and perhaps ALH85085. Phyllosilicates are mainly saponite and serpentine [5], and their composition is similar to that in CR chondrites. The water/rock ratio was low. Metal abundances in LEW85332 [1] are lower than in Acfer 182 (9.3 vol%) [4] and ALH85085 (22%) [6]. However, FeNi composition is the same, with a positive Ni-Co trend equivalent to the solar abundance ratio. This is the same as that in CR chondrites [7]. LEW85332 contains 0.5% carbon, combusting between 200 and 500 degrees C, indicating fine-grained, poorly crystalline carbon, or organic material. It contains 259 ppm nitrogen with delta^15N = +249o/oo. Most nitrogen is

  14. Noble Gases in the LEW 88663 L7 Chondrite

    NASA Astrophysics Data System (ADS)

    Miura, Y. N.; Sugiura, N.; Nagao, K.

    1995-09-01

    LEW88663 and some meteorites (e.g. Shaw) are the most highly metamorphosed meteorites among L group chondrites. Although the abundances of lithophile elements and oxygen isotopic compositions of the L7 chondrite LEW88663 (total recovered mass: 14.5g) are close to those of the range for L chondrites [1,2], metallic iron is absent and concentrations of siderophile elements are about half of typical values for L chondrites [3,4]. Petrographical and geochemical observation suggested that this meteorite has experienced partial melting [5]. As a part of our study on differentiated meteorites, we also investigated noble gases in this meteorite. We present here noble gas compositions of LEW88663 and discuss history of this meteorite. In addition, we will consider whether there is any evidence for bridging between chondrites and achondrites. Noble gases were extracted from a whole rock sample weighing 66.31 mg by total fusion, and all stable noble gas isotopes as well as cosmogenic radioactive 81Kr were analyzed using a mass spectrometer at ISEI, Okayama University. The results are summarized in the table. The concentrations of cosmogenic ^3He, ^21Ne, and ^38Ar are 7.3, 1.6 and 3.1x10^-8 cm^3STP/g, respectively. The cosmic-ray exposure ages based on them are calculated to be 4.7, 6.9 and 8.8 m.y., respectively, using the production rates proposed by [6, 7] and mean chemical compositions of L chondrites. The shorter cosmic-ray exposure ages T(sub)3 and T(sub)21 than T(sub)38 would be due to diffusive loss of lighter noble gases from the meteorite. The concentrations of trapped Kr and Xe in LEW88663 are lower than those for L6 chondrites [8], supporting thermal metamorphism for the meteorite higher than that for L6 chondrites. The Kr and Xe are isotopically close to those of the terrestrial atmospheric Kr and Xe, and elemental abundance ratios for Ar, Kr and Xe suggest adsorbed noble gas patterns of the terrestrial atmosphere. The terrestrial atmospheric Ar, Kr and Xe (most

  15. 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).

  16. Cumberland Falls chondritic inclusions: III. Consortium study of relationship to inclusions in Allan Hills 78113 aubrite

    SciTech Connect

    Lipschutz, M.E.; Verkouteren, R.M. ); Sears, D.W.G.; Hasan, F.A. ); Prinz, M.; Weisberg, M.K.; Nehru, C.E.; Delaney, J.S. ); Grossman, L.; Boily, M. )

    1988-07-01

    The authors describe the mineralogy and report contents of Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U and Zn determined by RNAA in three primitive chondritic inclusions from the ALH A78113 aubrite. Comparison of these data with those for large, petrologic type 3 chondritic clasts from the Cumberland Falls aubrite and the discovery of small clasts in it like those in ALH A78113 indicate that all constitute a single chondritic suite. They report thermoluminescence data for Cumberland Falls chondritic inclusions and achondritic host. These results, together with mineralogic, major, minor and trace element information, demonstrate that aubrite inclusions represent a different sort of type 3 chondrite, not an LL3 chondrite altered during equilibration with aubrite host. Instead, the aubrite inclusions represent a distinct chondrite class. These inclusions reflect nebular condensation/accretion over a broad redox range and at temperatures relatively high compared with those at which other type 3 chondrites formed. Limited metamorphism and reduction occurred during condensation/accretion, prior to incorporation into aubrite host. During the impact of the chondritic parent body with the aubrite parent body, chondrite fragments were strongly shocked and cooled rapidly. They then mixed with aubrite host, possibly in a regolith, so that these aubrites now represent impact breccias.

  17. Disentangling nebular and asteroidal features of CO3 carbonaceous chondrite meteorites

    NASA Technical Reports Server (NTRS)

    Scott, Edward R. D.; Jones, Rhian H.

    1990-01-01

    Ten carbonaceous CO3 chondrites (including four chondrites from Antarctica and the Colony, Isna, Kainsaz, Lance , Ornans, and Warrenton chondrites) were analyzed with respect to mean compositions of olivines and low-Ca pyroxenes in order to distinguish the primary nebular features of these chondrites from the secondary (asteroidal or nebular) features. In three of the Antarctic chondrites, matrices and metal grains were analyzed in order to investigate the origin of mineralogical trends in the CO3 sequence. Based on these results, the CO3 chondrites were classified into subtypes 3.0-3.7. In the silicates of chondrites ALH A77307 and Colony, classified as type 3.0, metamorphic effects appear to be absent. Chemical and mineralogical studies suggest that the type 3.1 to 3.7 CO chondrites represent a metamorphic sequence that formed from material closely resembling type 3.0 CO chondrites by metamorphism in one or more planetesimals or asteroids, not by interactions between chondritic ingredients in the solar nebula.

  18. 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.

  19. 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

  20. 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

  1. Stable Isotope Fractionation of Cr in Carbonaceous and Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Moynier, F.; Jacobsen, B.; Yin, Q.

    2006-12-01

    Difficulties with chemical separation and mass spectrometry combined with little expectation of isotopic fractionation at high temperature left the stable isotope geochemistry of Cr almost unknown [1]. The search for ^{53}Cr excess resulting from the decay of the radioactive nuclide ^{53}Mn (T1/2 = 3.5 My) was very successful but the small amount of data produced to date attests to the particularly difficult measurement by TIMS. This preliminary report describes evidence of mass-dependent fractionation of the stable Cr isotopes 50, 52, and 53 as measured by MC-ICPMS in meteorites relative to SRM 979 Cr standard. Cr was purified using cation-exchange chemistry. The yield is ~100 %. The samples were run on the Nu- Plasma HR of UC Davis in pseudo high-resolution mode. The absence of isotopic fractionation induced by the chemical purification has been double checked by 1) processing the standard through the column and 2) running the same sample several times through the columns. In both cases, we observe no difference in the measured isotopic ratio. The external reproducibility, estimated from 13 replicates of Bjurbole, is 50 ppm. The range of the fractionation per mass unit among 7 carbonaceous chondrites (CI, CM, CO, CV and CK) and 5 ordinary chondrites (H, L and LL) is 0.3 ‰. Individual chondrules from Chainpur and Bjurbole have a wider range (0.6 ‰). All the chondrites analyzed so far are isotopically lighter than the bulk silicate earth (δ ^{50/52}Cr=0, [1]). As for Zn [2], Cr isotopes seem to be heavier in ordinary chondrites (-0.23 ‰) than in carbonaceous chondrites (-0.35 ‰). Also as for Zn and Cu [2-3], Cr stable isotopes in carbonaceous chondrites are correlated with Δ 17O, suggesting a mixing between an isotopically heavy component and an isotopically light one. The correlation between mass-dependent fractionation of Cr and non-mass-dependent Δ 17O requires attention and adequate interpretation. References: [1] Johnson and Bullen, 2004, Review in

  2. 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.

  3. 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.

  4. Chemical studies of H chondrites. 5: Temporal variations of sources

    NASA Astrophysics Data System (ADS)

    Michlovich, Edward S.; Wolf, Stephen F.; Wang, Ming-Sheng; Vogt, Stephan; Elmore, David; Lipschutz, Michael E.

    1995-02-01

    We report Cl-36 (301-kyr half-life) data obtained by accelerator mass spectrometry allowing nominal terrestrial ages to be determined for 39 Antarctic H4-6 chondrites for which contents of volatile trace elements are known. The compositional difference between these Antarctic meteorites and 58 non-Antarctic falls increases with terrestrial age and, using multivariate statistical techniques, becomes highly significant for Antarctic samples with ages greater than 50 kyr. The compositional difference is inconsistent with trivial causes such as weathering and seems to reflect differences in thermal histories of parent sources. Temporal source variations for the H chondrite flux on Earth thus exist not only on a short-term, 40 years, basis (Dodd et al., 1993) but also on a long-term, greater than 50 kyr, basis.

  5. Neodymium isotope evidence for a chondritic composition of the Moon.

    PubMed

    Rankenburg, K; Brandon, A D; Neal, C R

    2006-06-01

    Samarium-neodymium isotope data for six lunar basalts show that the bulk Moon has a 142Nd/144Nd ratio that is indistinguishable from that of chondritic meteorites but is 20 parts per million less than most samples from Earth. The Sm/Nd formation interval of the lunar mantle from these data is 215(-21)(+23) million years after the onset of solar system condensation. Because both Earth and the Moon likely formed in the same region of the solar nebula, Earth should also have a chondritic bulk composition. In order to mass balance the Nd budget, these constraints require that a complementary reservoir with a lower 142Nd/144Nd value resides in Earth's mantle. PMID:16741118

  6. 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.

  7. 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.

  8. Nuclear track records in the Abee enstatite chondrite

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.

    1983-01-01

    A determination of preatmospheric mass and a delineation of cosmic ray exposure history are made, through the study of nuclear track records in 14 samples taken from different locations of an Abee enstatite chondrite cut slab. Measured track densities in different samples range from 10,000 to 1,000,000/sq cm. Excess tracks of fissiogenic origin were found near the grain edges and across cleavage planes in eight enstatite grains out of the 300 analyzed. The track data rule out preirradiation of any of the analyzed samples with shielding of less than a few tens of cm. The isotrack density contours on the plane of the slab imply an asymmetric ablation of the Abee chondrite during its atmospheric transit. A sphere of about 30 cm radius approximates the preatmospheric shape and size of the Abee meteorite, which underwent a 70% mass loss during ablation.

  9. Chemical studies of H chondrites. 5: Temporal variations of sources

    NASA Technical Reports Server (NTRS)

    Michlovich, Edward S.; Wolf, Stephen F.; Wang, Ming-Sheng; Vogt, Stephan; Elmore, David; Lipschutz, Michael E.

    1995-01-01

    We report Cl-36 (301-kyr half-life) data obtained by accelerator mass spectrometry allowing nominal terrestrial ages to be determined for 39 Antarctic H4-6 chondrites for which contents of volatile trace elements are known. The compositional difference between these Antarctic meteorites and 58 non-Antarctic falls increases with terrestrial age and, using multivariate statistical techniques, becomes highly significant for Antarctic samples with ages greater than 50 kyr. The compositional difference is inconsistent with trivial causes such as weathering and seems to reflect differences in thermal histories of parent sources. Temporal source variations for the H chondrite flux on Earth thus exist not only on a short-term, 40 years, basis (Dodd et al., 1993) but also on a long-term, greater than 50 kyr, basis.

  10. Glanggang and Selakopi - Two new paired Indonesian chondrites

    NASA Technical Reports Server (NTRS)

    Fredriksson, K.; Peretsman, G. S.

    1982-01-01

    The Indonesian meteorites Selakopi, and H-5 chondrite, and Glanggang, a breccia with H-6 fragments in an H-5 chondritic matrix, were recovered on the same day from sites only 50 km apart. The textures and compositions of Selakopi and the H-5 portion of Glanggang are very similar, indicating that they are closely related. The bulk chemistry of the H-6 portion of Glanggang is also very similar to that of the samples mentioned. It has therefore been concluded that Selakopi and the Glanggang breccia fragments were derived from the same source area and were probably ejected at the same time. Minor differences in bulk composition and texture among the three samples may be attributed to local variations on the parent body. However, for reasons stipulated in the conclusion, it is recommended that separate names be maintained for these meteorites until further, more definitive investigations have been made.

  11. 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.

  12. Cosmogenic radionuclides and noble gases in the Wethersfield (1982) chondrite

    NASA Technical Reports Server (NTRS)

    Evans, J. C.; Reeves, J. H.; Bogard, D. D.

    1986-01-01

    The Wethersfield (1982) chondrite was assayed for a suite of cosmogenic radionuclides shortly after fall. Data are reported for Be-7, Na-22, All-26, Sc-46, V-48, Cr-51, Mn-54, Co-56, Co-57, and Co-60. A comparison is made with predicted results based on a scaling to the Deep River Neutron Monitor. Noble gases were also assayed in a subsample. The cosmic-ray-exposure age is estimated to be 45 Myr.

  13. An ordinary chondrite impactor for the Popigai crater, Siberia

    NASA Astrophysics Data System (ADS)

    Tagle, Roald; Claeys, Philippe

    2005-06-01

    With a diameter of ˜100 km, Popigai in Northern Siberia is the largest crater known in the Cenozoic. The concentrations in platinum group elements (PGE) were analyzed in twenty samples of homogeneous impact melt collected in the northwestern flank of the crater to identify the composition of the projectile. The method selected was preconcentration by NiS fire assay followed by inductively coupled plasma-mass spectrometry (ICP-MS). This technique measures all the PGE (except Os) and by using aliquots >10g, the results are highly reproducible. The major and trace element composition of the impact melt resembles that of gneissic lithologies of the Anabar shield, which are representative of the target rock. The PGE are enriched in the melt by factors of 3 to 14 compared to the main target lithology, but the meteoritic contamination is only around 0.2 wt.%. Using plots of elemental ratios such as Ru/Rh vs. Pt/Pd or Ru/Rh vs. Pd/Ir, the Popigai impactor is clearly identified as an ordinary chondrite and most likely L-chondrite. This study indicates that PGE elemental ratios allow discrimination of the type of impactor, even in the case of low meteoritic contamination. This study confirms that a significant fraction of the crater-forming projectiles presently documented could have an ordinary chondrite composition. Their probable source, the S-type asteroids, appears to form the majority of the bodies in the main asteroid belt and among Near Earth Objects (NEOs). The ordinary chondrite origin of the Popigai projectile supports an asteroidal origin for the late Eocene impacts as a plausible alternative to the comet shower scenario proposed by Farley et al. (1998).

  14. Delivery of dark material to Vesta via carbonaceous chondritic impacts

    NASA Astrophysics Data System (ADS)

    Reddy, Vishnu; Le Corre, Lucille; O'Brien, David P.; Nathues, Andreas; Cloutis, Edward A.; Durda, Daniel D.; Bottke, William F.; Bhatt, Megha U.; Nesvorny, David; Buczkowski, Debra; Scully, Jennifer E. C.; Palmer, Elizabeth M.; Sierks, Holger; Mann, Paul J.; Becker, Kris J.; Beck, Andrew W.; Mittlefehldt, David; Li, Jian-Yang; Gaskell, Robert; Russell, Christopher T.; Gaffey, Michael J.; McSween, Harry Y.; McCord, Thomas B.; Combe, Jean-Philippe; Blewett, David

    2012-11-01

    NASA’s Dawn spacecraft observations of Asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75 μm filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater walls and rims); as flow-like deposits or rays commonly associated with topographic highs; and as dark spots (likely secondary impacts) nearby impact craters. This DM could be a relic of ancient volcanic activity or exogenic in origin. We report that the majority of the spectra of DM are similar to carbonaceous chondrite meteorites mixed with materials indigenous to Vesta. Using high-resolution seven color images we compared DM color properties (albedo, band depth) with laboratory measurements of possible analog materials. Band depth and albedo of DM are identical to those of carbonaceous chondrite xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance in DM (1-6 vol.%) is consistent with howardite meteorites. We find no evidence for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of DM. Our modeling efforts using impact crater scaling laws and numerical models of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta during the formation of the ∼400 km Veneneia basin by a low-velocity (<2 km/s) carbonaceous impactor. This discovery is important because it strengthens the long-held idea that primitive bodies are the source of carbon and probably volatiles in the early Solar System.

  15. Chemical studies of H chondrites. I - Mobile trace elements and gas retention ages

    NASA Technical Reports Server (NTRS)

    Lingner, David W.; Huston, Ted J.; Hutson, Melinda; Lipschutz, Michael E.

    1987-01-01

    Trends for 16 trace elements (Ag, As, Au, Bi, Cd, Co, Cs, Ga, In, K, Rb, Sb, Se, Te, Tl, and Zn), chosen to span a broad geochemical and thermal response range, in 44 H4-6 chondrites, differ widely from those in L4-6 chondrites. In particular, H chondrites classified as heavily shocked petrologically do not necessarily exhibit Ar-40 loss and vice versa. The clear-cut causal relationship between siderophile and mobile element loss with increasing late shock seen in L chondrites is not generally evident in the H group. H chondrite parent material experienced an early high temperature genetic episode that mobilized a substantial proportion of these trace elements so that later thermal episodes resulted in more subtle, collateral fractionations. Mildly shocked L chondrites escaped this early high temperature event, indicating that the two most numerous meteorite groups differ fundamentally in genetic history.

  16. 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.

  17. 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.

  18. Forming Chondrites in a Solar Nebula with Magnetically Induced Turbulence

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph R.

    2016-10-01

    Chondritic meteorites provide valuable opportunities to investigate origins of the solar system. We explore impact jetting as a mechanism to form chondrules and subsequent pebble accretion as a mechanism to accrete them onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is < 5 times more massive than the minimum-mass solar nebula at a = 2-3 AU and parent bodies of chondrites are < 1024 g (< 500 km in radius) there, impact jetting and subsequent pebble accretion can reproduce a number of properties of the meteoritic data. The properties include the present asteroid belt mass, formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies' mass leads to the following implications: primordial asteroids that were originally >1024 g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into origins of the solar system.

  19. 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.

  20. 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.

  1. Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    King, Ashley J.; Solomon, Jake R.; Schofield, Paul F.; Russell, Sara S.

    2015-12-01

    The CI and CI-like chondrites provide a record of aqueous alteration in the early solar system. However, the CI-like chondrites differ in having also experienced a late stage period of thermal metamorphism. In order to constrain the nature and extent of the aqueous and thermal alteration, we have investigated the bulk mineralogy and abundance of H2O in the CI and CI-like chondrites using thermogravimetric analysis and infrared spectroscopy.

  2. 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 σ), 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 μg/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.

  3. Phyllosilicates in the Mokoia CV carbonaceous chondrite - Evidence for aqueous alteration in an oxidizing environment

    NASA Technical Reports Server (NTRS)

    Tomeoka, Kazushige; Buseck, Peter R.

    1990-01-01

    Most CV chondrites contain little if any phyllosilicate mineralization. A petrographic and transmission electron microscopy study of the Mokoia CV carbonaceous chondrite shows that the matrix, chondrules, aggregates, and inclusions all contain considerable amounts of phyllosilicates. The mineralogy and occurrence of phyllosilicates in Mokoia differ from those in the CI and CM chondrites. The differences suggests that aqueous alteration of the three meteorite groups probably occurred under a variety of conditions.

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

    NASA Astrophysics Data System (ADS)

    Afiattalab, F.; Wasson, J. T.

    1980-03-01

    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.

  5. 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.

  6. 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.

  7. 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.

  8. Parent bodies of L and H chondrites: Times of catastrophic events.

    NASA Astrophysics Data System (ADS)

    Alexeev, V. A.

    1998-01-01

    An analysis of the distribution of 3He and 4He in L and H chondrites has shown that the parent body of L chondrites underwent a catastrophic collision in space 340 ( 50 Myr. This age differs considerably from the collision age of 520 ( 60 Myr given previously (Heymann, 1967). The parent body of H chondrites may also have undergone local heating and degassing about 200 Myr ago. Data for L chondrites argue in favour of Antarctic and non-Antarctic meteorites having originated from a common parent body.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. A search for H-chondritic chromite grains in sediments that formed immediately after the breakup of the L-chondrite parent body 470 Ma ago

    NASA Astrophysics Data System (ADS)

    Heck, Philipp R.; Schmitz, Birger; Rout, Surya S.; Tenner, Travis; Villalon, Krysten; Cronholm, Anders; Terfelt, Fredrik; Kita, Noriko T.

    2016-03-01

    A large abundance of L-chondritic material, mainly in the form of fossil meteorites and chromite grains from micrometeorites, has been found in mid-Ordovician 470 Ma old sediments globally. The material has been determined to be ejecta from the L chondrite parent body breakup event, a major collision in the asteroid belt 470 Ma ago. In this study we search the same sediments for H-chondritic chromite grains in order to improve our understanding of the extraterrestrial flux to Earth after the asteroid breakup event. We have used SIMS in conjunction with quantitative SEM/EDS to determine the three oxygen isotopic and elemental compositions, respectively, of a total of 120 randomly selected, sediment-dispersed extraterrestrial chromite grains mainly representing micrometeorites from 470 Ma old post-breakup limestone from the Thorsberg quarry in Sweden and the Lynna River site in Russia. We show that 99% or more of the grains are L-chondritic, whereas the H-chondritic fraction is 1% or less. The L-/H-chondrite ratio after the breakup thus was >99 compared to 1.1 in today's meteoritic flux. This represents independent evidence, in agreement with previous estimates based on sediment-dispersed extraterrestrial chromite grain abundances and sedimentation rates, of a two orders of magnitude higher post-breakup flux of L-chondritic material in the micrometeorite fraction. Finally, we confirm the usefulness of three oxygen isotopic SIMS analyses of individual extraterrestrial chromite grains for classification of equilibrated ordinary chondrites. The H- and L-chondritic chromites differ both in their three oxygen isotopic and elemental compositions, but there is some overlap between the groups. In chromite, TiO2 is the oxide most resistant to diagenesis, and the combined application of TiO2 and oxygen three-isotope analysis can resolve uncertainties arising from the compositional overlaps.

  15. Hf-W Chronometry of Ordinary Chondrites and the Timing of Solar Nebula Metal-Silicate Fractionation

    NASA Astrophysics Data System (ADS)

    Hellmann, J. L.; Kruijer, T. S.; Kleine, T.

    2016-08-01

    Precise internal Hf-W isochrons for equilibrated L and LL chondrites constrain the timing of metal-silicate fractionation among different ordinary chondrite parent bodies as well as the accretion and thermal history of these bodies.

  16. Relationships Among Physical Properties as Indicators of High Temperature Deformation or Post-Shock Thermal Annealing in Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Friedrich, J. M.; Ruzicka, A.; Macke, R. J.; Rivers, M. L.; Ebel, D. S.

    2016-08-01

    A simple model of the effects of high velocity impacts in chondrites suggests that shock intensity and metal grain foliation should be inversely related to porosity. In some ordinary chondrites this model relationship does not hold.

  17. CR chondrites: Shock, aqueous alteration and terrestrial weathering

    NASA Astrophysics Data System (ADS)

    Abreu, N. M.

    2012-12-01

    CR chondrite are a group asteroidal meteorites, whose importance lies in the exotic organic and presolar material [1] found in its most pristine members and in the broad range of alteration features represented in the remaining specimens in this group [2]. This FE-SEM, EMPA, FIB/TEM study takes advantage of the CR's mineralogical diversity to define different trends of secondary alteration, by comparing the CR3s to the Antarctic CRs: MIL 07525, MIL 07513, GRA 06100, LAP 04516, GRO 03116, GRO 95577, and EET 96259. Collisions and subsequent annealing have affected MIL 07513, GRA 06100, and GRO 03116. Shock stages are often assigned based on progressive changes in the textures of olivines and feldspars. However, the large olivines in shocked CRs do not appear to record these process. Opaques, on the other hand, preserve hallmark signatures of impacts, such as crystalline metal/sulfide veins. Opaque nodules in MIL 07513, GRA 06100, GRO 03116 consist of intergrowths of μm-sub μm FeNi-rich metal, kamacite, Fe-sulfides, Fe-oxides, nm-sized metallic Cu and CuFe (~85 wt.% Cu, 14 wt.% Fe ± < 1wt.% Co, Ni, S) alloys. MIL 07525, GRO 03116, EET 96259, LAP 04516, and GRO 95577 show increasing signs of aqueous alteration, such as increasing amounts of ordered phyllosilicates. Although most phyllosilicates are intergrowths of Fe-rich serpentine and saponite, LAP 04516 also contains large (μm-sized), interpenetrating, Fe-rich (cronstedtite-like) phyllosilicates packages with 14Å basal spacings, similar to those observed in CI chondrites by [3]. Heterogeneously interspersed within phyllosilicates are amorphous Fe-rich silicates and small grains (<50nm) of Fe-rich sulfides, partly oxidized sulfides, and in LAP 04516, tochilinite. Tochilinite shows consistent enrichments in Si (~5 wt.%), suggesting that this meteorite has undergone similar pathways of aqueous alteration as CM chondrites [e.g., 4-5]. Despite the myriad of mineralogical changes triggered by secondary and tertiary

  18. 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

  19. A Survey of Large Silicate Objects in Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Hutchison, R.; Bridges, J. C.

    1995-09-01

    We present the results of a survey of large silicate objects in ordinary chondrites (OCs) from the collection of the Natural History Museum, London; 390 H-group, 386 L-group and 57 LL-group meteorites were examined. A total of 61 objects were identified (Table 1). Meteorites with light and dark, brecciated fabrics were excluded from our survey. Following Weisberg et al. [1], large silicate objects are taken to be >= 5mm in size. Macrochondrules have rounded outlines and textures - porphyritic, barred olivine, radiating pyroxene - that are indistinguishable from normal chondrules in OCs [1]. In addition, we also recognise igneous clasts and chondritic clasts. The largest macrochondrule in the collection is 4cm diameter, with a microporphyritic texture [2]. Igneous clasts are those objects whose properties indicate that they originated through melting and differentiation on a planetary body. Examples include a 2cm diameter clast, in Ness County (L6), which contains large (2mm) olivine and enstatite grains set in a plagioclase + olivine groundmass, cristobalite- and tridymite-rich clasts [3] and the FELINE feldspar-nepheline clast [4]. Chondritic clasts comprise a diverse group including a 1cm clast from Barwell (L6) which contains apparently remelted chondrules, microporphyritic clasts with K-rich mesostasis e.g. in Quenggouk (H4) and a 1cm single olivine grain with minor inclusions of anorthite and enstatite, in Julesburg (L3). The K-rich objects are similar to others described from a survey of LL-chondrites and may have an impact origin or have undergone exchange with a K-rich vapor [5]. Abundances of the three types of large silicate objects (Table 1) reflect the relative numbers of H, L and LL meteorite samples in the collection, although LL-group hosted clasts are over-represented as our work concentrated on sections of LL-chondrites. In total, 46% of the objects are macrochondrules, 18% are igneous clasts and 36% are in the indeterminate chondritic clast group

  20. The negligible chondritic contribution in the lunar soils water.

    PubMed

    Stephant, Alice; Robert, François

    2014-10-21

    Recent data from Apollo samples demonstrate the presence of water in the lunar interior and at the surface, challenging previous assumption that the Moon was free of water. However, the source(s) of this water remains enigmatic. The external flux of particles and solid materials that reach the surface of the airless Moon constitute a hydrogen (H) surface reservoir that can be converted to water (or OH) during proton implantation in rocks or remobilization during magmatic events. Our original goal was thus to quantify the relative contributions to this H surface reservoir. To this end, we report NanoSIMS measurements of D/H and (7)Li/(6)Li ratios on agglutinates, volcanic glasses, and plagioclase grains from the Apollo sample collection. Clear correlations emerge between cosmogenic D and (6)Li revealing that almost all D is produced by spallation reactions both on the surface and in the interior of the grains. In grain interiors, no evidence of chondritic water has been found. This observation allows us to constrain the H isotopic ratio of hypothetical juvenile lunar water to δD ≤ -550‰. On the grain surface, the hydroxyl concentrations are significant and the D/H ratios indicate that they originate from solar wind implantation. The scattering distribution of the data around the theoretical D vs. (6)Li spallation correlation is compatible with a chondritic contribution <15%. In conclusion, (i) solar wind implantation is the major mechanism responsible for hydroxyls on the lunar surface, and (ii) the postulated chondritic lunar water is not retained in the regolith.

  1. Numerical Simulation of Hydrothermal Convection in Chondritic Parent Bodies

    NASA Astrophysics Data System (ADS)

    Schubert, G.; Travis, B. J.

    2004-11-01

    Chondritic meteorites are so named because they nearly all contain chondrules - small spherules of olivine and pyroxene that condensed and crystallized in the solar nebula and then combined with other material to form a matrix. Their parent bodies did not differentiate, i.e., form a crust and a core. Carbonaceous chondrites (CCs) derived from undifferentiated icy planetesimals. CCs exhibit liquid water-rock interactions. CCs contain small but significant amounts of radiogenic elements (e.g., 26Al), sufficient to warm up an initially cold planetesimal. A warmed-up phase could last millions of years. During the warmed-up phase, liquid water will form, and could evolve into a hydrothermal convective flow. Flowing water will affect the evolution of minerals. We report on results of a numerical study of the thermal evolution of CCs, considering the major factors that control heating history and possible flow, namely: permeability, radiogenic element content, and planetesimal radius. We determine the time sequence of thermal processes, length of time for a convective phase and patterns of flow, amount of fluid flow throughout the planetesimals, and sensitivity of evolution to primary parameters. We use the MAGHNUM code to simulate 3-D dynamic freezing and thawing and flow of water in a self-gravitating, permeable spherical body. Governing equations are Darcy's law, mass conservation, energy conservation, and the equation of state for water, ice and vapor mixtures. We have simulated the evolution of heating, melting of ice, subsequent flow and eventual re-freezing for several examples of carbonaceous chondrite planetesimals. We have demonstrated that hydrothermal convection should occur for a range of parameter values and would last for several millions of years. Roughly half the interior of simulated planetesimals experience water fluxes of 100--200 pore volumes. High pore volume flux facilitates extensive chemical reactions.

  2. The negligible chondritic contribution in the lunar soils water

    PubMed Central

    Stephant, Alice; Robert, François

    2014-01-01

    Recent data from Apollo samples demonstrate the presence of water in the lunar interior and at the surface, challenging previous assumption that the Moon was free of water. However, the source(s) of this water remains enigmatic. The external flux of particles and solid materials that reach the surface of the airless Moon constitute a hydrogen (H) surface reservoir that can be converted to water (or OH) during proton implantation in rocks or remobilization during magmatic events. Our original goal was thus to quantify the relative contributions to this H surface reservoir. To this end, we report NanoSIMS measurements of D/H and 7Li/6Li ratios on agglutinates, volcanic glasses, and plagioclase grains from the Apollo sample collection. Clear correlations emerge between cosmogenic D and 6Li revealing that almost all D is produced by spallation reactions both on the surface and in the interior of the grains. In grain interiors, no evidence of chondritic water has been found. This observation allows us to constrain the H isotopic ratio of hypothetical juvenile lunar water to δD ≤ −550‰. On the grain surface, the hydroxyl concentrations are significant and the D/H ratios indicate that they originate from solar wind implantation. The scattering distribution of the data around the theoretical D vs. 6Li spallation correlation is compatible with a chondritic contribution <15%. In conclusion, (i) solar wind implantation is the major mechanism responsible for hydroxyls on the lunar surface, and (ii) the postulated chondritic lunar water is not retained in the regolith. PMID:25288758

  3. How Do L/LL Chondrites Relate to L and LL Falls?

    NASA Astrophysics Data System (ADS)

    Friedrich, J. M.; Lipschutz, M. E.

    2001-03-01

    Provisionally our ICPMS results, when treated by cluster analysis, suggest L/LL chondrites constitute an individual group. We found it interesting that bulk REE contents in the L/LL chondrite suite seem enriched relative to the L and LL suites.

  4. Structural and Functional Micro-Infrared Survey of Pristine Carbonaceous Chondrites Insoluble Organic Matter

    NASA Astrophysics Data System (ADS)

    Orthous-Daunay, F.-R.; Quirico, E.; Beck, P.; Brissaud, O.; Schmitt, B.

    2010-03-01

    We present a mid-infrared study of C2 and C1 chondrites IOM. All have similar aliphatic structure at 50°C under 10-7 mbar. Oxidized functions are depleted in less altered chondrites. 300°C heating in ambient air turns aliphatic chains to esters.

  5. Trace element content of chondritic cosmic dust: Volatile enrichments, thermal alterations, and the possibility of contamination

    NASA Astrophysics Data System (ADS)

    Flynn, G. J.; Sutton, S. R.; Bajt, S.

    1993-03-01

    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.

  6. 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.

  7. 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.

  8. Theoretical predictions of volatile bearing phases and volatile resources in some carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Ganguly, Jibamitra; Saxena, Surendra K.

    1989-01-01

    Results are presented from theoretical calculations to predict the modal abundances and compositions of the major mineral phases and the vapor phase that could develop in the bulk compositions of carbonaceous chondrites. The abundances and compositions are obtained as functions of temperature and pressure. The calculations are used to evaluate the volatile and mineralogical resource potential of C1 and C2 carbonaceous chondrites.

  9. A neutron activation analysis of iridium concentration in Yamato carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Yabushita, S.; Wada, K.; Moriyama, H.; Takeuchi, K.

    1988-09-01

    Iridium concentration in extra-terrestrial bodies is an important quantity in relation to Ir-rich geological layers. Ir concentration of a Yamato carbonaceous chondrite (Y-793321) has been measured by a neutron activation method. The measurement yields a value (0.57±0.06) μg per gramme for the chondrite.

  10. Implications of poikilitic textures in LL-group chondrites

    NASA Technical Reports Server (NTRS)

    Fodor, R. V.; Keil, K.

    1975-01-01

    Five lithic fragments with poikilitic textures in five LL-group chondrites are examined by microscope and electron microprobe to determine whether the textures have resulted from processes related to impact events, such as thermal metamorphism or partial melting. The bulk and pyroxene compositions of the fragments are determined. The compositional characteristics of minerals in certain fragments are found to indicate an apparent melt origin. It is concluded that impact processes produced the poikilitic textures and that complete melting, partial melting, and solid-state recrystallization all have had some part in producing the textures.

  11. Comments on D/H ratios in chondritic organic matter

    NASA Astrophysics Data System (ADS)

    Smith, J. W.; Rigby, D.

    1981-06-01

    D/H ratios in chondritic organic matter are investigated. Demineralized organic residues obtained from previous experiments were dried in a quartz reaction vessel under vacuum for 60 minutes at 250-300 C and then combusted in oxygen for 20 minutes at 850 C. The apparatus is described and the results of the experiments such as D/H ratios in water and measurements on total carbon dioxide are given. Atomic H/C ratios calculated directly from the quantities of carbon dioxide and water recovered, are reported according to Standard Mean Ocean Water and Pee Dee Belemnite, using the customary notation.

  12. Chemical alterations of the Holbrook chondrite resulting from terrestrial weathering

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Bogard, D. D.

    1978-01-01

    Major, minor and trace element analysis as well as noble gas measurements were performed on three Holbrook chondrite samples collected fresh in 1912, in 1931, and in 1968. Decreases in metallic iron and MgO and an increase in total iron were detected. Elemental concentrations of Ti, Ca, Al, P, Mn, Ni, and Cr did not change significantly during weathering. While sodium might have been lost, and K slightly enriched, the trace elements C, Rb, and Sr increased at least two-fold during weathering. Gas abundances decreased, and the concentration ratios of noble gas nuclides varied unpredictably.

  13. Organic matter in carbonaceous chondrites, planetary satellites, asteroids and comets

    NASA Technical Reports Server (NTRS)

    Cronin, John R.; Pizzarello, Sandra; Cruikshank, Dale P.

    1988-01-01

    A detailed review is given of the organic compounds found in carbonaceous chondrite meteorites, especially the Murchison meteorite, and detected spectroscopically in other solar-system objects. The chemical processes by which the organic compounds could have formed in the early solar system and the conditions required for these processes are discussed, taking into account the possible alteration of the compounds during the lifetime of the meteoroid. Also considered are the implications for prebiotic evolution and the origin of life. Diagrams, graphs, and tables of numerical data are provided.

  14. Organic matter and metamorphic history of CO chondrites

    NASA Astrophysics Data System (ADS)

    Bonal, Lydie; Bourot-Denise, Michèle; Quirico, Eric; Montagnac, Gilles; Lewin, Eric

    2007-03-01

    The metamorphic grades of a series of eight CO3 chondrites (ALHA77307, Colony, Kainsaz, Felix, Lancé, Ornans, Warrenton and Isna) have been quantified. The method used was based on the structural grade of the organic matter trapped in the matrix, which is irreversibly transformed by thermal metamorphism. The maturation of the organic matter is independent with respect to the mineralogical context and aqueous alteration. This metamorphic tracer is thus valid whatever the chemical class of chondrites. Moreover, it is sensitive to the peak metamorphic temperature. The structural grade of the organic matter was used along with other metamorphic tracers such as petrography of opaque minerals, Fa and Fs silicate composition in type I chondrules, presolar grains and noble gas (P3 component) abundance. The deduced metamorphic hierarchy and the attributed petrographic types are the following: ALHA77307 (3.03) < Colony (3.1) < Kainsaz (3.6) < Felix (3.6 (1)) < Ornans (3.6 (2)) < Lancé (3.6 (3)) < Warrenton (3.7 (1)) < Isna (3.7 (2)). For most metamorphosed objects, the peak metamorphic temperature can be estimated using a geothermometer calibrated with terrestrial metasediments [Beyssac O., Goffe B., Chopin C., and Rouzaud J. N. (2002) Raman spectrum of carbonaceous material in metasediments: a new geothermometer. J. Metamorph. Geol., 20, 859-871]. A value of 330 °C was obtained for Allende (CV chondrite), Warrenton and Isna, consistent with temperatures estimated from Fe diffusion [Weinbruch S., Armstrong J., and Palme H. (1994). Constraints on the thermal history of the Allende parent body as derive from olivine-spinel thermometry and Fe/Mg interdiffusion in olivine. Geochim. Cosmochim. Acta58(2), 1019-1030.], from the Ni content in sulfide-metal assemblages [Zanda B., Bourot-Denise M., and Hewins R. (1995) Condensate sulfide and its metamorphic transformations in primitive chondrites. Meteorit. Planet. Sci.30, A605.] and from the d002 interlayer spacing in poorly

  15. Redox effects in ordinary chondrites and implications for asteroid spectrophotometry

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1992-01-01

    The sensitivity of reflectance spectra to mean ferrous iron content and olivine and pyroxene proportion enhancements in the course of metamorphic oxidation is presently used to examine whether metamorphically-induced ranges in mineralogy, and corresponding spectral parameters, may explain the observed variations in S-asteroid rotational spectra. The predicted spectral variations within any one chondrite class are, however, insufficient to account for S-asteroid rotational spectra, and predicted spectral-range slopes have a sign opposite to the rotational measurements. Metamorphic oxidation is found unable to account for S-asteroid rotational spectra.

  16. Ubiquitous interstellar diamond and SiC in primitive chondrites - Abundances reflect metamorphism

    NASA Technical Reports Server (NTRS)

    Huss, Gary R.

    1990-01-01

    It is shown here that interstellar diamond and SiC were incorporated into all groups of chondrite meteorites. Abundances rapidly go to zero with increasing metamorphic grade, suggesting that metamorphic destruction is responsible for the apparent absence of these grains in most chondrites. In unmetamorphosed chondrites, abundances normalized to matrix content are similar for different classes. Diamond samples from chondrites of different classes have remarkably similar noble-gas constants and isotropic compositions, although constituent diamonds may have come from many sources. SiC seems to be more diverse, partly because grains are large enough to measure individually, but average characteristics seem to be similar from meteorite to meteorite. These observations suggest that various classes of chondritic meteorites sample the same solar system-wide reservoir of interstellar grains.

  17. Nuclear track and compositional studies of olivines in CI and CM chondrites

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Macdougall, J. D.

    1983-01-01

    The CI and CM chondrites, with bulk chemical compositions closely resembling solar values, are important for the study of early solar system processes. Noble gas and particle track studies have revealed that a majority of the CI and CM chondrites contain precompaction solar wind and solar flare irradiation records. A quantitative understanding of these records is important because it would allow constraints to be placed on the environment in which the irradiation occurred, and, therefore, on the mode of evolution of the CI and CM chondrites. The present investigation is concerned primarily with fossil track evidence, taking into account selected specimens of several CI and CM chondrites. In addition, the results are presented of extensive studies of the angular distributions of tracks in irradiated grains from four CM chondrites. The results provide information on the exposure geometry of the grains.

  18. 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).

  19. Petrology and In Situ Trace Element Chemistry of a Suite of R Chondrites

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

    Rumuruti (R) chondrites are characterized by low chondrule/matrix modal ratios, high oxidation state, small mean chondrule size, abundant sulfides and low metal contents, and are of petrologic types 3 to 6 [1, 2]. LAP 04840 (R5, [3]) and MIL 11207 (R6), contain the high-T hydrous phases amphibole and mica [3, 4]; not all equilibrated R chondrites contain these [2]. R chondrites thus can provide evidence on whether there are compositional effects caused by high-T, high-fluid metamorphism of nebular materials. We are investigating a suite of R chondrites of diverse petrologic grades to further understand the nature of the metamorphic processes that engendered them [5]. We report on our petrological studies, plus preliminary in situ analyses of trace elements in amphibole-bearing R chondrites.

  20. Extraterrestrial amino acids identified in metal-rich CH and CB carbonaceous chondrites from Antarctica

    NASA Astrophysics Data System (ADS)

    Burton, Aaron S.; Elsila, Jamie E.; Hein, Jason E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-03-01

    Carbonaceous chondrites contain numerous indigenous organic compounds and could have been an important source of prebiotic compounds required for the origin of life on Earth or elsewhere. Extraterrestrial amino acids have been reported in five of the eight groups of carbonaceous chondrites and are most abundant in CI, CM, and CR chondrites but are also present in the more thermally altered CV and CO chondrites. We report the abundance, distribution, and enantiomeric and isotopic compositions of simple primary amino acids in six metal-rich CH and CB carbonaceous chondrites that have not previously been investigated for amino acids: Allan Hills (ALH) 85085 (CH3), Pecora Escarpment (PCA) 91467 (CH3), Patuxent Range (PAT) 91546 (CH3), MacAlpine Hills (MAC) 02675 (CBb), Miller Range (MIL) 05082 (CB), and Miller Range (MIL) 07411 (CB). Amino acid abundances and carbon isotopic values were obtained by using both liquid chromatography time-of-flight mass spectrometry and fluorescence, and gas chromatography isotope ratio mass spectrometry. The δ13C/12C ratios of multiple amino acids fall outside of the terrestrial range and support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids (13-16 parts per million, ppm) while CB chondrite extracts had much lower abundances (0.2-2 ppm). The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites and contained elevated levels of β-, γ-, and δ-amino acids compared to the corresponding α-amino acids, providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites.

  1. 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.

  2. Presolar grains in the CM2 chondrite Sutter's Mill

    NASA Astrophysics Data System (ADS)

    Zhao, Xuchao; Lin, Yangting; Yin, Qing-Zhu; Zhang, Jianchao; Hao, Jialong; Zolensky, Michael; Jenniskens, Peter

    2014-11-01

    The Sutter's Mill (SM) carbonaceous chondrite is a regolith breccia, composed predominantly of CM2 clasts with varying degrees of aqueous alteration and thermal metamorphism. An investigation of presolar grains in four Sutter's Mill sections, SM43, SM51, SM2-4, and SM18, was carried out using NanoSIMS ion mapping technique. A total of 37 C-anomalous grains and one O-anomalous grain have been identified, indicating an abundance of 63 ppm for presolar C-anomalous grains and 2 ppm for presolar oxides. Thirty-one silicon carbide (SiC), five carbonaceous grains, and one Al-oxide (Al2O3) were confirmed based on their elemental compositions determined by C-N-Si and O-Si-Mg-Al isotopic measurements. The overall abundance of SiC grains in Sutter's Mill (55 ppm) is consistent with those in other CM chondrites. The absence of presolar silicates in Sutter's Mill suggests that they were destroyed by aqueous alteration on the parent asteroid. Furthermore, SM2-4 shows heterogeneous distributions of presolar SiC grains (12-54 ppm) in different matrix areas, indicating that the fine-grained matrix clasts come from different sources, with various thermal histories, in the solar nebula.

  3. Exposure history of the Sutter's Mill carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Nishiizumi, K.; Caffee, M. W.; Hamajima, Y.; Reedy, R. C.; Welten, K. C.

    2014-11-01

    The Sutter's Mill (SM) carbonaceous chondrite fell in California on April 22, 2012. The cosmogenic radionuclide data indicate that Sutter's Mill was exposed to cosmic rays for 0.082 ± 0.008 Myr, which is one of the shortest ages for C chondrites, but overlaps with a small cluster at approximately 0.1 Myr. The age is significantly longer than proposed ages that were obtained from cosmogenic noble gas concentrations, which have large uncertainties due to trapped noble gas corrections. The presence of neutron-capture 60Co and 36Cl in SM indicates a minimum preatmospheric radius of approximately 50 cm, and is consistent with a radius of 1-2 m, as derived from the fireball observations. Although a large preatmospheric size was proposed, one fragment (SM18) contains solar cosmic ray-produced short-lived radionuclides, such as 56Co and 51Cr. This implies that this specimen was less than 2 cm from the preatmospheric surface of Sutter's Mill. Although this conclusion seems surprising, it is consistent with the observation that the meteoroid fragmented high in the atmosphere. The presence of SCR-produced nuclides is consistent with the high SCR fluxes observed during the last few months before the meteorite's fall, when its orbit was less than 1 AU from the Sun.

  4. Chondrules in H3 chondrites - Textures, compositions and origins

    NASA Technical Reports Server (NTRS)

    Lux, G.; Keil, K.; Taylor, G. J.

    1981-01-01

    Compositional and textural variations among chondrules in unequilibrated (type 3) H-group chondrites are examined in order to determine possible relations between chondrule compositions and textures. Bulk compositions of polished thin sections of 90 individual chondrules and 16 compound chondrule sets from the Sharps, Tieschitz and Bremervorde chondrites were measured by broad-beam electron probe analyses; the chondrules were also classified petrographically as barred olivine, porphyritic olivine, porphyritic pyroxene, barred pyroxene, radiating pyroxene or fine-grained. The mean compositions of each type are found to be distinct as verified by discriminant analysis, despite a large scatter, with the olivine-rich chondrules characterized by low SiO2 and high FeO and MgO contents, greater concentrations of TiO2, Al2O3, Na2O and K2O, and lower Cr2O3 and MnO relative to pyroxene-rich chondrules. Data suggest that composition, together with cooling rate, has played a conspicuous role in producing observed chrondrule textures, and are consistent with chondrule formation from mixtures of differing fractions of high-, intermediate- and low-temperature nebular condensates that underwent melting in space.

  5. Molybdenum Isotopic Composition of Iron Meteorites, Chondrites and Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2003-01-01

    Recent Mo isotopic studies of meteorites reported evidence for differences in isotopic compositions for whole rocks of some primitive and differentiated meteorites relative to terrestrial materials. Enrichments of r- and p-process isotopes of up to 3-4 units (e unit = parts in 10(exp 4) over s-process dominated isotopes are the most prominent features. Certain types of presolar grains show large enrichments in s-process isotopes, however, it was concluded on grounds of mass balance that incomplete digestion of such grains cannot explain the enrichments of r- and p-process isotopes in whole rocks of primitive chondrites. If the reported variability in r- and p-process isotope enrichments reflects the true isotopic characteristics of the whole rocks, the implications are quite profound. It would suggest the presence of large scale Mo isotopic heterogeneity within the solar accretion disk with likely collateral effects for other elements. However, such effects were not found for Ru isotopes, nor for Zr isotopes. Another recent Mo isotopic study by multi collector ICP-MS could not confirm the reported deviations in Allende, Murchison or iron meteorites. Here, we present new results for the Mo isotopic composition of iron meteorites, chondrites and CAIs obtained by negative thermal ionization mass spectrometry (NTIMS). We discuss analytical aspects and the homogeneity of Mo isotopic compositions in solar system materials.

  6. Survey of Large, Igneous-Textured Inclusions in Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Armstrong, K.; Ruzicka, A. M.

    2013-12-01

    Ordinary (O) chondrites are a class of primitive stony meteorites, and as a group comprise our most abundant samples of early solar system materials. Unique to O chondrites are igneous-textured inclusions up to 4 cm in diameter; about an order of magnitude larger than the much more abundant chondrules. These inclusions are almost always highly depleted in metal and sulfide relative to their host meteorite, but but otherwise have diverse characteristics. They exhibit a large range of textures, mineralogies, and bulk compositions, suggesting a variety of formation processes. They all crystallized from large melt volumes, the origins of which are poorly understood. Models proposed for their formation include (1) shock melting of ordinary chondrites with an associated loss of metal and sulfide; (2) melting of vapor-fractionated condensate mixture; (3) chondrule formation involving a larger melt production volume than typical for chondrules; and (4) igneous differentiation occurring within planetesimals sampled by ordinary chondrite parent bodies. Polished thin sections of inclusions from several O-chondrites have been examined with optical light microscopy (OLM) using a Leica DM 2500 petrographic microscope. Petrographic data such as texture, grain sizes and shapes were collected for the inclusions and their hosts in order to facilitate comparisons. Texturally, the inclusions were determined to fall into one of three distinct textural categories: porphyritic, fine granular, and skeletal. Mean grain sizes are on the order of 100 um for both microporphyritic and fine granular inclusions, with microporphyritic inclusions showing a much wider range of grain sizes. The largest grains in the microporphyritic inclusions are on average ~0.25 mm, with the grains of the mesostasis <100 microns. Skeletal olivine textures are defined as being dominated by crystals that are an order of magnitude longer across one direction than the other (e.g., 1 mm x 100 um). Five inclusions have

  7. Experimental Aqueous Alteration of the Allende CV3 Chondrite

    NASA Astrophysics Data System (ADS)

    Tomeoka, K.; Kojima, T.

    1995-09-01

    Aqueous alteration is an important process that prevailed in the early solar system. In order to better understand the aqueous alteration processes and conditions, we embarked in hydrothermal alteration experiments of the Allende CV3 chondrite. We here present the first results of our experiments. Samples of Allende were sealed in gold tubes with 1-N HCl and heated in a reactor vessel at 450 degrees C and 800 bars for 4 to 6 weeks. Thin sections were made from the run products and were observed and analyzed by a scanning electron microscope equipped with an EDS spectrometer. Our experiments produced remarkable alteration textures in the Allende chondrite. Parts of internal areas of most of the chondrules are replaced by brownish-to-greenish phyllosilicate, exhibiting an appearance closely similar to the altered ("spinach"-bearing) chondrules in CM chondrites. Fractures and interstices in chondrules and matrix, up to 20 micrometers in width and 1 mm in length, are filled with phyllosilicate, producing remarkable veins similar to those observed in CI chondrites. Mainly two kinds of phyllosilicates were produced. One contains major Mg and Fe and has compositions similar to Fe-rich saponite. This is the most common phyllosilicate that occurs in both chondrules and matrix; it is primarily formed by replacing olivine and low-Ca pyroxene. The other kind of phyllosilicate contains major Mg and Fe and variable Al; it is probably a mixture of two phases, so we tentatively call it high-Al phyllosilicates (HAP). HAP occurs mainly in chondrule mesostasis, where it is formed by replacing mesostasis glass. Chondrules and aggregates are altered from their edges to inward. Olivine in outer areas of chondrules and aggregates are enriched in Fe, and most of individual olivine grains show strong Fe-Mg zoning, indicating substantial Fe was added from matrix to chondrules. Mesostasis in central areas is preferentially replaced by HAP, while that in outer areas is replaced by saponite

  8. The valence and coordination of titanium in ordinary and enstatite chondrites

    NASA Astrophysics Data System (ADS)

    Simon, Steven B.; Sutton, Stephen R.; Grossman, Lawrence

    2016-09-01

    One way to better understand processes related to chondrite metamorphism is to evaluate changes in chondrite features as a function of petrologic type. Toward this end the valence and coordination of Ti in olivine and pyroxene in suites of ordinary (H, L, and LL) and enstatite (EH and EL) chondrites of types 3 through 6 have been determined with XANES spectroscopy. Trivalent Ti, typically 10-40% of the Ti in the analytical volumes, was found in ordinary chondrites of all types, despite the stability of oxidized iron in the samples. Average valences and the proportions of Ti that are in tetrahedral coordination generally decrease with increasing grade between types 3.0 and 3.5, increase from 3.5 to 4, and then level off. These trends are consistent with previous studies of chondrite oxidation states using other methods, except here the onset of oxidation is observed at a lower type, ∼3.5, than previously indicated (4). These results are also consistent with previous suggestions that oxidation of higher-grade ordinary chondrite samples involved exposure to aqueous fluids from melting of accreted ice. In the enstatite chondrites, typically 20-90% of the Ti is trivalent Ti, so it is reduced compared to Ti in the ordinary chondrites. Valence decreases slightly from petrologic type 3 to 4 and increases from 4 to 6, but no increases in tetrahedral coordination with petrologic type are observed, indicating a redox environment or process distinct from that of ordinary chondrite metamorphism. The presence of Ti4+ in the E chondrites supports previous suggestions that they formed from oxidized precursors that underwent reduction. Unlike ordinary chondrites, enstatite chondrites are thought to have been derived from a body or bodies that did not accrete ice, which could account for their different valence-coordination-petrologic type relationships. The hypothesis, based on observations of unmetamorphosed chondrules and supported by laboratory experiments, that equilibration

  9. Aliphatic amines in Antarctic CR2, CM2, and CM1/2 carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Aponte, José C.; McLain, Hannah L.; Dworkin, Jason P.; Elsila, Jamie E.

    2016-09-01

    Meteoritic water-soluble organic compounds provide a unique record of the processes that occurred during the formation of the solar system and the chemistry preceding the origins of life on Earth. We have investigated the molecular distribution, compound-specific δ13C isotopic ratios and enantiomeric compositions of aliphatic monoamines present in the hot acid-water extracts of the carbonaceous chondrites LAP 02342 (CR2), GRA 95229 (CR2), LON 94101 (CM2), LEW 90500 (CM2), and ALH 83100 (CM1/2). Analyses of the concentration of monoamines in these meteorites revealed: (a) the CR2 chondrites studied here contain higher concentrations of monoamines relative to the analyzed CM2 chondrites; (b) the concentration of monoamines decreases with increasing carbon number; and (c) isopropylamine is the most abundant monoamine in these CR2 chondrites, while methylamine is the most abundant amine species in these CM2 and CM1/2 chondrites. The δ13C values of monoamines in CR2 chondrite do not correlate with the number of carbon atoms; however, in CM2 and CM1/2 chondrites, the 13C enrichment decreases with increasing monoamine carbon number. The δ13C values of methylamine in CR2 chondrites ranged from -1 to +10‰, while in CM2 and CM1/2 chondrites the δ13C values of methylamine ranged from +41 to +59‰. We also observed racemic compositions of sec-butylamine, 3-methyl-2-butylamine, and sec-pentylamine in the studied carbonaceous chondrites. Additionally, we compared the abundance and δ13C isotopic composition of monoamines to those of their structurally related amino acids. We found that monoamines are less abundant than amino acids in CR2 chondrites, with the opposite being true in CM2 and CM1/2 chondrites. We used these collective data to evaluate different primordial synthetic pathways for monoamines in carbonaceous chondrites and to understand the potential common origins these molecules may share with meteoritic amino acids.

  10. Gallium and germanium in the metal and silicates of L- and LL-chondrites.

    NASA Technical Reports Server (NTRS)

    Chou, C.-L.; Cohen, A. J.

    1973-01-01

    Concentrations of Ga and Ge in the metal of 31 L-, 8 LL- and 2 H-chondrites, and in the silicates of 12 L- and LL-chondrites have been determined by spectrophotometric methods. The ranges of Ga contents in the metal of L- and LL-chondrites are 1.1 to 36.9 ppm and 1.0 to 34.1 ppm, respectively. The Ge content in the metal is positively correlated with Ga and ranges from 89.1 to 160 ppm and from 126 to 308 ppm for L- and LL-chondrites, respectively. The Ga content in the silicates of L-chondrites varies from 4.0 to 8.9 ppm. The Ga and Ge contents in the metal are clearly lower in unequilibrated than in equilibrated L- and LL-group chondrites. Unequilibrated and equilibrated chondrites are well separated in the plots of Ga vs Ge in the metal, and the L- and LL-groups are also well resolved. The Ga and Ge in the metal are well correlated with petrologic grade. This suggests that Ga and Ge variations in the metal are related to thermal metamorphism. There is evidence of an enrichment of Ga in the metal due to shock reheating.

  11. The histories of ordinary chondrite parent bodies - U, Th-He age distributions

    SciTech Connect

    Wasson, J.T.; Wang, Sichao Purple Mountain Observatory, Nanjing )

    1991-06-01

    Age patterns observed in meteorite groups reflect the different thermal or impact histories experienced by their parent bodies. To assess the number of ordinary chondrite (OC) parent bodies, rare-gas data in the Schultz and Kruse (1989) data base were used to calculate U, Th-He gas-retention ages. Most H- and LL-chondrite ages are high; about 81 percent are greater than 2.2 Ga. In contrast, most L-chondrite ages are low; about 69 percent are not greater than 2.2 Ga, and about 35 percent are not greater than 0.9 Ga. The latter fraction is substantially lower than the value of 44 percent given by Heymann (1967). The difference is attributed to the preferential inclusion of shocked L chondrites in early studies. Broad age peaks in the H and LL groups near 3.4 Ga probably reflect thermal loss during metamorphism, but in the H distribution there is a hint of minor outgassing 'events' near 1 Ga. The L/LL chondrites have chemical properties intermediate between and unresolvable from L and LL chondrites. The high ages of most L/LL chondrites are evidence against these originating on the L parent body; the L/LL age distribution is consistent with an origin on the LL parent body or on an independent body. 22 refs.

  12. The histories of ordinary chondrite parent bodies - U, Th-He age distributions

    NASA Astrophysics Data System (ADS)

    Wasson, John T.; Wang, Sichao

    1991-06-01

    Age patterns observed in meteorite groups reflect the different thermal or impact histories experienced by their parent bodies. To assess the number of ordinary chondrite (OC) parent bodies, rare-gas data in the Schultz and Kruse (1989) data base were used to calculate U, Th-He gas-retention ages. Most H- and LL-chondrite ages are high; about 81 percent are greater than 2.2 Ga. In contrast, most L-chondrite ages are low; about 69 percent are not greater than 2.2 Ga, and about 35 percent are not greater than 0.9 Ga. The latter fraction is substantially lower than the value of 44 percent given by Heymann (1967). The difference is attributed to the preferential inclusion of shocked L chondrites in early studies. Broad age peaks in the H and LL groups near 3.4 Ga probably reflect thermal loss during metamorphism, but in the H distribution there is a hint of minor outgassing "events" near 1 Ga. The L/LL chondrites have chemical properties intermediate between and unresolvable from L and LL chondrites. The high ages of most L/LL chondrites are evidence against these originating on the L parent body; the L/LL age distribution is consistent with an origin on the LL parent body or on an independent body.

  13. Localized Chemical Redistribution During Aqueous Alteration in CR2 Carbonaceous Chondrites EET 87770 and EET 92105

    NASA Technical Reports Server (NTRS)

    Burger, Paul V.; Brearley, Adrian J.

    2005-01-01

    Carbonaceous chondrites are primitive meteorites that are valuable because they preserve evidence of processes that occurred in the solar nebula and on asteroidal parent bodies. Among the carbonaceous chondrite groups, the CR group appears to contain a particularly pristine record of early solar system processes. Distinguishing characteristics of CR2 chondrites include a high abundance of chondrules (50-60 vol.%) and Fe, Ni metal (5-8 vol. %). These meteorites preserve evidence for varying degrees of aqueous alteration, manifested by progressive replacement of chondrule mesostasis by phyllosilicates. Recent studies have suggested that even in weakly altered chondrites, mass transfer occurred between chondrules and fine-grained matrices, implying that aqueous alteration must have followed lithification of the final meteorite parent body. Although petrographic characteristics of alteration in CR chondrites have been documented, mechanisms of alteration are still only poorly understood. For example, the relative rates and scales of elemental mobility as well as the sources and sinks for key elements are currently not constrained. An improved knowledge of these issues will contribute to an increased understanding of aqueous alteration reactions on meteorite parent bodies. This study expands on research conducted on Type IIA chondrules and chondrule fragments from two CR2 chondrites, EET 87770 and EET 92105. These chondrites have been weakly altered; chondrule mesostases show incipient alteration primarily where they are in direct contact with fine-grained matrices.

  14. 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.

  15. 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.

  16. Metal phases in ordinary chondrites: Magnetic hysteresis properties and implications for thermal history

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Magnetic properties are sensitive proxies to characterize FeNi metal phases in meteorites. We present a data set of magnetic hysteresis properties of 91 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 that dominates the induced magnetism and tetrataenite (both in the cloudy zone as single-domain grains, and as larger multidomain grains in plessite and in the rim of zoned taenite) dominates the remanent magnetism, in agreement with previous microscopic magnetic observations. The bulk metal contents derived from magnetic measurements are in agreement with those estimated previously from chemical analyses. We evidence a decreasing metal content with increasing petrologic type in ordinary chondrites, compatible with oxidation of metal during thermal metamorphism. Types 5 and 6 ordinary chondrites have higher tetrataenite content than type 4 chondrites. This is compatible with lower cooling rates in the 650-450 °C interval for higher petrographic types (consistent with an onion-shell model), but is more likely the result of the oxidation of ordinary chondrites with increasing metamorphism. In equilibrated chondrites, shock-related transient heating events above approximately 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 (e.g., following shock reheating or excavation after thermal metamorphism). Our data strengthen the view that the poor magnetic recording properties of multidomain kamacite and the secondary origin of tetrataenite make equilibrated ordinary chondrites challenging

  17. 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.

  18. 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.

  19. Extraterrestrial Amino Acids Identified in Metal-Rich CH and CB Carbonaceous Chondrites from Antarctica

    NASA Technical Reports Server (NTRS)

    Burton, Aaron S.; Elsila, Jamie E.; Hein, Jason E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-01-01

    Carbonaceous chondrites contain numerous indigenous organic compounds and could have been an important source of prebiotic compounds required for the origin of life on Earth or elsewhere. Extraterrestrial amino acids have been reported in five of the eight groups of carbonaceous chondrites and are most abundant in CI, CM, and CR chondritesbut are also present in the more thermally altered CV and CO chondrites. We report the abundance, distribution, and enantiomeric and isotopic compositions of simple primary amino acids in six metal-rich CH and CB carbonaceous chondrites that have not previously been investigated for amino acids: Allan Hills (ALH) 85085 (CH3), Pecora Escarpment(PCA) 91467 (CH3), Patuxent Range (PAT) 91546 (CH3), MacAlpine Hills (MAC) 02675(CBb), Miller Range (MIL) 05082 (CB), and Miller Range (MIL) 07411 (CB). Amino acid abundances and carbon isotopic values were obtained by using both liquid chromatography time-of-flight mass spectrometry and fluorescence, and gas chromatography isotope ratiomass spectrometry. The (delta D, delta C-13, delta N-15) ratios of multiple amino acids fall outside of the terrestrial range and support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids (1316 parts per million, ppm) while CB chondrite extracts had much lower abundances (0.22 ppm). The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites and contained elevated levels of beta-, gamma-, and delta-amino acids compared to the corresponding alpha-amino acids, providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites.

  20. 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

  1. Composition of matrix in the CR chondrite LAP 02342

    NASA Astrophysics Data System (ADS)

    Wasson, John T.; Rubin, Alan E.

    2009-03-01

    We report evidence of interchondrule matrix heterogeneity on a scale of ˜50 μm in the well-preserved CR2 chondrite LAP 02342. Despite minor effects resulting from asteroidal aqueous alteration, the matrix in this CR chondrite seems to preserve much of the compositional record of nebular fines. We carried out electron-microprobe studies using a 3-μm-diameter beam; we analyzed 10 elements in 36- or 49-point grids on 11 ca. 50 × 50-μm rectangular areas of matrix. Each grid area has a distinct composition, inconsistent with a simple model of matrix material having a uniform composition throughout the nebular formation region of the CR chondrites. On S-Fe, Mg-Si, K-Na and K-Al scatter diagrams, the grid areas (i.e., different matrix patches) are largely separated from each other; plots of means with 95% confidence limits demonstrate that the compositions are resolvable. Five matrix areas were analyzed again in duplicate runs; excellent agreement was observed between duplicate studies. LAP 02342 experienced two forms of mild aqueous alteration - as patchy enrichments in Ca (inferred to reflect CaCO 3) and as regions in which sulfide laths are embedded within phyllosilicates. Despite this evidence of aqueous transport, the effect on the composition of matrix is not resolvable. For example, matrix points that were adjacent to points with high CaCO 3 contents show elemental concentrations similar to those in regions having only one or two points with a Ca enrichment. It appears that secondary minerals are found in areas where there are suitable precursor phases and voids into which new phases could grow unimpeded. Calcium appears to be unique in forming a phase that greatly lowers the Ca ++ content of the aqueous medium, thus enhancing the rate of diffusion. Because chondrules vary widely in bulk composition, the formation of chondrules in small sets (100 or less) could generate "smoke" and mesostasis spray with compositions unique to each set. However, if these

  2. Depth Profiles of Cosmogenic Noble Gases in the Chondrite Knyahinya

    NASA Astrophysics Data System (ADS)

    Toe, S.; Lavielle, B.; Gilabert, E.; Simonoff, G. N.

    1993-07-01

    Concentrations and isotopic ratios of Ne, Ar, Kr, and Xe have been analyzed in 5-g size samples from different positions within the L5 chondrite Knyahinya. A previous work [1] has shown that Knyahinya experienced a single-stage exposure history (duration 40.5 Ma) as a meteoroid of approximately spherical shape (radius 45 cm). For these reasons, this meteorite represents a very interesting object to study depth profiles of cosmogenic nuclide concentrations and to test and improve model calculations of production rates. The procedure of extraction of noble gases adopted for this work, includes two pyrolyses respectively at about 450 degrees C and 650 degrees C, followed by a combustion step in pure O2 (15-25 torr pressure) at 650 degrees C before the complete melting of the sample [2]. This procedure allows a low-temperature extraction of a significant fraction of the Kr and Xe trapped noble gas component, leading to an enrichment of the cosmogenic component during the last temperature step. Concentration of trapped Ar, Kr, and Xe is 2-3 times lower than expected for a type 5 chondrite. The isotopic composition of the trapped Xe component analyzed in the combustion step is identical with the OC- Xe composition measured in Forest Vale [3]. Preliminary results show that concentration of cosmogenic 83Kr increases by 16% from the surface to the center when the ratio of cosmogenic 78Kr to 83Kr decreases from 0.157 to 0.136. The concentration of 81Kr has been measured in each sample. It increases from 0.0220 10^-12 cm^3 STP/g near the surface to 0.0255 10^-12 cm^3 STP/g at the center, in excellent agreement with the variations measured by Eugster [4] in other ordinary chondrites. Acknowledgments: This work was supported by C.N.R.S., by IN2P3 and by INSU (Programme National de Planetologie). References: [1] Graf Th. et al. (1990) GCA, 54, 2511-2520. [2] Gilabert E. and Lavielle B. (1991) Meteoritics, 26, 337. [3] Lavielle B. and Marti K. (1992) JGR, 97, 20875-20881. [4

  3. Mineralogic and petrologic study of the low-temperature minerals in carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Wood, J. A.

    1977-01-01

    Samples and petrographic thin sections of the Orgueil, Ivuna, and Alais chondrites were examined by optical, X-ray, and SEM techniques. Mineral species identified as primary vein constituents were epsomite, gypsum, and a calcium-magnesium carbonate. Relative abundances and textural relationships have suggested that fracture mineralization was a multi stage process, with individual mineralizations closely associated with impact brecciation events. Mass balance considerations of carbonaceous chondrite matrix support the prevailing view that the source of the fracture filling minerals was local. By inference they also suggest that the phyllosilicate matrix has been chemically altered and that there are probably very few primitive mineral phases in the primitive Cl chondrites.

  4. The early solar system abundance of /sup 244/Pu as inferred from the St. Severin chondrite

    SciTech Connect

    Hudson, G.B.; Kennedy, B.M.; Podosek, F.A.; Hohenberg, C.M.

    1987-03-01

    We describe the analysis of Xe released in stepwise heating of neutron-irradiated samples of the St. Severin chondrite. This analysis indicates that at the time of formation of most chondritic meteorites, approximately 4.56 x 10/sup 9/ years ago, the atomic ratio of /sup 244/Pu//sup 238/U was 0.0068 +- 0.0010 in chondritic meteorites. We believe that this value is more reliable than that inferred from earlier analyses of St. Severin. We feel that this value is currently the best available estimate for the early solar system abundance of /sup 244/Pu. 42 refs., 2 tabs.

  5. The Nature of C Asteroid Regolith Revealed from the Jbilet Winselwan CM Chondrite

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Chan, Queenie H. S.; Le, Loan; Kring, David; Cato, Michael; Fagan, Amy L.

    2016-01-01

    C-class asteroids frequently exhibit reflectance spectra consistent with thermally metamorphosed carbonaceous chondrites, or a mixture of phyllosilicate-rich material along with regions where they are absent. One particularly important example appears to be asteroid 162173 Ryugu, the target of the Hayabusa 2 mission, although most spectra of Ryugu are featureless, suggesting a heterogeneous regolith. Here we explore an alternative cause of dehydration of regolith of C-class asteroids - impact shock melting. Impact shock melting has been proposed to ex-plain some mineralogical characteristics of CB chondrites, but has rarely been considered a major process for hydrous carbonaceous chondrites.

  6. 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

  7. Thermal history of type-3 chondrites in the NASA antarctic collection

    NASA Astrophysics Data System (ADS)

    Bonal, L.; Quirico, E.; Montagnac, G.

    2014-07-01

    Chondrites are the most primitive meteorites. However, they were all modified in some ways by post-accretion geological processes operating on their asteroidal parent bodies. Hence, to decipher the formation(s) and origin(s) of their components, we must first understand how chondritic materials were modified in their asteroidal parent bodies. The modifications induced by secondary processes should not be underestimated and have to be precisely estimated before any interpretation of chondrite properties in terms of cosmochemistry. In particular, all chondrites contain some organic components that were potentially chemically and physically modified through post-accretion processes. A thin understanding of the induced evolution is required to allow for pertinent comparisons with other primitive extraterrestrial materials, such as cometary grains, to finally address questions such as the origin of organics in the Solar System. Type 3 chondrites experienced thermal metamorphism on their asteroidal parent body due to the radioactive decay of elements such as ^{26}Al. Temperatures higher than 300 °C were experienced on timescales of several thousands of years. Still, type 3 chondrites remain as unequilibrated rocks and common mineralogical thermometers cannot be applied. The polyaromatic carbonaceous matter is sensitive to thermal episodes (of long and short duration) experienced by the host meteorite. In particular, its structural order directly reflects the thermal history experienced on their parent bodies. The structural modification of the aromatic carbonaceous matter towards a higher order is irreversible, and independent of the mineralogy and degree of aqueous alteration. It is mainly controlled by the peak metamorphic temperature. Moreover, under the assumption of fairly similar organic precursors among chondrites of distinct groups, the structural order of polyaromatic organic matter allows for a direct comparison of their metamorphic grades. It is then possible

  8. Petrology and oxygen isotope compositions of chondrules in E3 chondrites

    NASA Astrophysics Data System (ADS)

    Weisberg, Michael K.; Ebel, Denton S.; Connolly, Harold C.; Kita, Noriko T.; Ushikubo, Takayuki

    2011-11-01

    Chondrules in E3 chondrites differ from those in other chondrite groups. Many contain near-pure endmember enstatite (Fs <1). Some contain Si-bearing FeNi metal, Cr-bearing troilite, and, in some cases Mg, Mn- and Ca-sulfides. Olivine and more FeO-rich pyroxene grains are present but much less common than in ordinary or carbonaceous chondrite chondrules. In some cases, the FeO-rich grains contain dusty inclusions of metal. The oxygen three-isotope ratios (δ 18O, δ 17O) of olivine and pyroxene in chondrules from E3 chondrites, which are measured using a multi-collection SIMS, show a wide range of values. Most enstatite data plots on the terrestrial fractionation (TF) line near whole rock values and some plot near the ordinary chondrite region on the 3-isotope diagram. Pyroxene with higher FeO contents (˜2-10 wt.% FeO) generally plots on the TF line similar to enstatite, suggesting it formed locally in the EC (enstatite chondrite) region and that oxidation/reduction conditions varied within the E3 chondrite chondrule-forming region. Olivine shows a wide range of correlated δ 18O and δ 17O values and data from two olivine-bearing chondrules form a slope ˜1 mixing line, which is approximately parallel to but distinct from the CCAM (carbonaceous chondrite anhydrous mixing) line. We refer to this as the ECM (enstatite chondrite mixing) line but it also may coincide with a line defined by chondrules from Acfer 094 referred to as the PCM (Primitive Chondrite Mineral) line ( Ushikubo et al., 2011). The range of O isotope compositions and mixing behavior in E3 chondrules is similar to that in O and C chondrite groups, indicating similar chondrule-forming processes, solid-gas mixing and possibly similar 16O-rich precursors solids. However, E3 chondrules formed in a distinct oxygen reservoir. Internal oxygen isotope heterogeneity was found among minerals from some of the chondrules in E3 chondrites suggesting incomplete melting of the chondrules, survival of minerals from

  9. Grain size distribution of the matrix in the Allende chondrite

    NASA Astrophysics Data System (ADS)

    Toriumi, M.

    1989-03-01

    Results are presented from analytical TEM, high-resolution TEM, and SEM studies of the Allende chondrite, showing that the matrix consists of very fine-grained Fe-rich olivine, Ca-poor and Fe-rich clinopyroxene, Fe-rich spinel, and Ni-bearing troilite. Slightly sintered and non-sintered very fine-grained aggregates are observed. The results suggest that the coarse-grained olivine aggregates experienced a heating event, whereas the ultrafine-grained aggregates did not. The size and frequency distributions of matrix grains are measured. The frequency distribution displays a long-term tail with power law and a log-normal pattern with a peak at 5 nm in the range from 1 to 10 nm. This suggests that the fine-grained matrix was probably formed at conditions far from equilibrium in the protosolar cloud.

  10. On mobile element transport in heated Abee. [chondrite thermal metamorphism

    NASA Technical Reports Server (NTRS)

    Ikramuddin, M.; Lipschutz, M. E.; Gibson, E. K., Jr.

    1979-01-01

    Abee chondrite samples were heated at 700 C for one week at 0.00001 to 0.001 atm Ne or at 0.00001 atm H2. Samples heated in Ne showed greater loss of Bi and Se and greater retention of Zn than those heated in H2. An inverse relationship between Zn retention and ambient Ne pressure was found. Seven trace elements (Ag, Co, Cs, Ga, In, Te, and Tl) were retained or lost to the same extent regardless of the heating conditions. Variations in the apparent activation energy for C above and below 700 C suggest that diffusive loss from different hosts and/or different mobile transport processes over the temperature range may have been in effect.

  11. Spectral evidence for a carbonaceous chondrite surface composition on Deimos

    NASA Technical Reports Server (NTRS)

    Pang, K. D.; Rhoads, J. W.; Lane, A. L.; Ajello, J. M.

    1980-01-01

    The surface compositions of Phobos and Deimos as determined by their UV-visible reflectance are compared in order to evaluate the hypothesis that the different surface morphologies of the two satellites are due to different mechanical properties. The UV-visible reflectance spectrum of Deimos is compiled from Mariner 9 UV spectrometry and Canopus star tracker photometry and ground-based colorimetry and polarimetry; the geometric albedo of Deimos is determined from Mariner 9 Canopus star tracker data. The reflectance spectra of Deimos and Phobos are found to be similar in a first approximation, exhibiting low, flat reflectivities in the visible and dropping off sharply in the UV, compatible with a probable carbonaceous chondrite nature for Deimos as well as Phobos and suggesting that their different surface morphologies are most likely due to different orbital histories.

  12. Rb-Sr studies of CI and CM chondrites

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Wetherill, G. W.

    1979-01-01

    Rb-Sr whole rock analyses have been performed on 2 CI and 3 CM chondrites. Four of these stones (Ivuna, Orgueil, Cold Bokkeveld and Erakot) were previously studied in this laboratory and were shown to be discordant from a 4.6 Gyr isochron. The fifth, Murchison, was not previously studied. The new data support the discordance of the first four stones, and indicate that Murchison is also discordant. Studies of Sr isotope ratios in unspiked Orgueil show that the discordance is not due to inhomogeneities in the Sr-84/Sr-86 ratio caused by incomplete mixing of nucleosynthesis products. In order to gauge the effects of weathering, two leaching experiments were performed on fresh, interior samples of Murchison; one for a period of 1.5 hr and the other for 117 hr. The results indicate that the relative solubility of nonradiogenic Sr is approximately twice that of Rb and radiogenic Sr is more soluble than the nonradiogenic Sr.

  13. Isotopic composition and concentration of sulfur in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Gao, X.; Thiemens, M. H.

    1993-07-01

    New sulfur isotopic ratio measurements are reported for seven carbonaceous chondrites. Newly developed procedures permit measurement of delta S-33, delta S-34, and delta S-36 at precisions significantly greater than previously reported. A search for S-36 nucleosynthetic anomalies coproduced with anomalies in, for example, Ti-50 and Ca-48 was negative. The high endemic sulfur concentration probably dilutes any S-36 anomaly, and separation of individual sulfur phases may be needed to identify S-36 carrier phases. Large internal isotopic variations are observed, deriving from parent body and possibly nebular processes. Chondrule separates from Allende demonstrate isotopic compositions which vary as a function of diameter. High-temperature gas-solid exchange and a two-component mixing model may account for the observations. High-resolution isotopic data and structural information are reported for organic sulfur compounds separated by chemical extractions. The insoluble organics appear to be of either aliphatic or alicyclic structure and are dominant phases.

  14. 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.

  15. Cosmogenic Radionuclides in Recently Fallen Chondrites Mihonoseki and Tahara

    NASA Astrophysics Data System (ADS)

    Shima, M.; Honda, M.; Yabuki, S.; Takahashi, K.

    1993-07-01

    Introduction: The chondrite Mihonoseki, L6, 6.38 kg, fell on December 10, 1992 [1]. The other chondrite, Tahara, fell on March 26, 1991, on the deck of car- carrier ship, M.S. Century-Highway No.1 of Kawasaki Kisen Kaisha Ltd., anchored at T-3 berth of Toyota Pier, at Toyohashi harbor, in Tahara-Center, Toyota Motor Corp., Tahara-machi, Atsumi-gun, Aichi-ken, Japan. Although the total mass is estimated to be more than 5 kg, only several fragments were recovered by crews. In fact, this was recognized by the event of Mihonoseki. Tahara was classified as H5 [2]. Gamma-Ray Counting: With whole mass of Mihonoseki, nondestructive gamma-ray countings started on December 15, 1992, using a pure Ge detector (ORTEC), 45 mm x 39 mm, horizontal type. Data collections were performed every day in the beginning and later about every week through February 3, 1993. A sample chamber was shielded with 15-cm-thick lead, 6-cm-thick iron, and 0.5-cm-thick plastic plates. For Tahara, another set (Canberra), 44 mm x 42 mm, coaxial type, was used. The 420-g fragment was mounted in the sample chamber shielded with 15-cm-thick lead, 2-cm-thick iron, 2-cm-thick copper, and 2-cm-thick plastic plates. The counting started in January 1993. The counting efficiencies for gamma rays as a function of energy, ranging between 122 keV (57Co) and 1809 keV (26Al), have been determined using three different standards. A mixed standard solution of nine-species gamma-ray emitters, QCY-44, reference time 12:00 GMT on February 1, 1993, was supplied from Amersham, England. The solution was dropped onto (1) chips of Al-foil, (2) chips of filter paper, or (3) olivine sand. Those standards were mixed thoroughly with mock materials, fine and coarse olivine sand and iron powder, and reagent KCl, standard for 40K, then filled into mock shells of Mihonoseki and Tahara, which were made of hard plastic and aluminum foil with epoxy resin, respectively. For Tahara, mocks with all three types of standards were examined for

  16. A model for the production of cosmogenic nuclides in chondrites

    NASA Technical Reports Server (NTRS)

    Graf, TH.; Baur, H.; Signer, P.

    1990-01-01

    A model is presented for calculating the production rates of cosmic-ray-produced He, Ne, and Ar as well as Be-10, Al-26, and Mn-53 in chondrites of variable size and shape. The predictions of this model are compared with published data for the meteorites ALH78084, St. Severin, and Keyes. The agreement is found to be about 5 percent for the concentrations of Be-10, Ne-21, Ne-22, Ar-38, and Mn-53, and to be better than 1 percent for the Ne-22/Ne-21 ratios. The correlation between P(Be-10)/P(Ne-21) and Ne-22/Ne-21 ratios is experimentally verified over a wide range of irradiation conditions.

  17. Bright Stuff on Ceres = Sulfates and Carbonates on CI Chondrites

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Chan, Queenie H. S.; Gounelle, Matthieu; Fries, Marc

    2016-01-01

    Recent reports of the DAWN spacecraft's observations of the surface of Ceres indicate that there are bright areas, which can be explained by large amounts of the Mg sulfate hexahydrate (MgSO4•6(H2O)), although the identification appears tenuous. There are preliminary indications that water is being evolved from these bright areas, and some have inferred that these might be sites of contemporary hydro-volcanism. A heat source for such modern activity is not obvious, given the small size of Ceres, lack of any tidal forces from nearby giant planets, probable age and presumed bulk composition. We contend that observations of chondritic materials in the lab shed light on the nature of the bright spots on Ceres

  18. STARDUST INVESTIGATION INTO THE CR CHONDRITE GROVE MOUNTAIN 021710

    SciTech Connect

    Zhao Xuchao; Lin Yangting; Floss, Christine; Bose, Maitrayee

    2013-05-20

    We report the presolar grain inventory of the CR chondrite Grove Mountain 021710. A total of 35 C-anomalous grains ({approx}236 ppm) and 112 O-anomalous grains ({approx}189 ppm) were identified in situ using NanoSIMS ion imaging. Of 35 C-anomalous grains, 28 were determined to be SiC grains by Auger spectroscopy. Seven of the SiC grains were subsequently measured for N and Si isotopes, allowing classification as one nova grain, one Y grain, one Z grain, and four mainstream grains. Eighty-nine out of 112 O-anomalous grains belong to Group 1, indicating origins in low-to-intermediate-mass red giant and asymptotic giant branch stars. Twenty-one are Group 4 grains and have origins in supernovae. Auger spectroscopic elemental measurements of 35 O-anomalous grains show that 33 of them are ferromagnesian silicates. They have higher Mg/(Mg+Fe) ratios than those reported in other meteorites, suggesting a lower degree of alteration in the nebula and/or asteroid parent bodies. Only two oxide grains were identified, with stoichiometric compositions of MgAl{sub 2}O{sub 4} and SiO{sub 2}, respectively. The presolar silicate/oxide ratio of GRV 021710 is comparable with those of the CR3 chondrites (QUE 99177 and MET 00426) and primitive interplanetary dust particles. In order to search for presolar sulfides, the meteorite was also mapped for S isotopes. However, no presolar sulfides were found, suggesting a maximum abundance of 2 ppm. The scarcity of presolar sulfides may be due to their much faster sputtering rate by cosmic rays compared to silicates.

  19. 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.

  20. Magnetic Classification of Ordinary Chondrites: Falls Versus Finds

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Sagnotti, L.; Consolmagno, G.; Folco, L.; Pesonen, L.; Terho, M.

    2001-12-01

    We have undertaken a magnetic susceptibility (K) survey of various meteorite collections in Italy and Vatican, using a large coil (8 cm) Kappabridge instrument. This original database, merged with previous data from Finnish and Czech collections [1], allows us to analyze about 650 different ordinary chondrites, equally distributed in 3 categories: falls, Antarctic and non-Antarctic finds (half from Sahara). For a large number of meteorites, especially falls, we measured numerous samples from various collections, allowing testing the homogeneity of K values. It appears that in the majority of falls logK values are reproducible within 0.1, even at the 1 cc levels. Finds are less homogeneous, together with some brecciated or veined falls, where one expects locally variable metal concentrations. When falls are taken separately from finds a very narrow range of logK values appear to characterize H, L and LL classes, with no overlap (excluding 8 percent of petrographically anomalous samples). On the other hand finds show a variable decrease of logK, correlated to weathering grade. Antarctic finds (mostly from Frontier Mountain) appear on average less affected by weathering although logK histogram is clearly shifted toward low values compared to finds. Interestingly the FRO histograms exhibit quite narrow peaks, while other finds show a larger spread. This can be tentatively explained by a predominance of a few individual showers as suggested by cosmogenic isotope features [2] . From our analysis of a large number of samples, it appears clearly that finds, even from Antarctic, have to be excluded for the purpose of defining mean magnetic properties of asteroids related to ordinary chondrites. Simple in-situ probes could be designed for future asteroid missions to identify meteorite type using our database. References: [1] Terho M. et al. (1993) Studia Geoph. Geod.. 37, 65-82 [2] Welten K.C. et al. (2001) Mete-oritics & Planet. Sci., 36, 301-318.

  1. Multiple precursors of secondary mineralogical assemblages in CM chondrites

    NASA Astrophysics Data System (ADS)

    Pignatelli, Isabella; Marrocchi, Yves; Vacher, Lionel. G.; Delon, RéMi; Gounelle, Matthieu

    2016-04-01

    We report a petrographic and mineralogical survey of tochilinite/cronstedtite intergrowths (TCIs) in Paris, a new CM chondrite considered to be the least altered CM identified to date. Our results indicate that type-I TCIs consist of compact tochilinite/cronstedtite rims surrounding Fe-Ni metal beads, thus confirming kamacite as the precursor of type-I TCIs. In contrast, type-II TCIs are characterized by complex compositional zoning composed of three different Fe-bearing secondary minerals: from the outside inwards, tochilinite, cronstedtite, and amakinite. Type-II TCIs present well-developed faces that allow a detailed morphological analysis to be performed in order to identify the precursors. The results demonstrate that type-II TCIs formed by pseudomorphism of the anhydrous silicates, olivine, and pyroxene. Hence, there is no apparent genetic relationship between type-I and type-II TCIs. In addition, the complex chemical zoning observed within type-II TCIs suggests that the alteration conditions evolved dramatically over time. At least three stages of alteration can be proposed, characterized by alteration fluids with varying compositions (1) Fe- and S-rich fluids; (2) S-poor and Fe- and Si-rich fluids; and (3) S- and Si-poor, Fe-rich fluids. The presence of unaltered silicates in close association with euhedral type-II TCIs suggests the existence of microenvironments during the first alteration stages of CM chondrites. In addition, the absence of Mg-bearing secondary minerals in Paris TCIs suggests that the Mg content increases during the course of alteration.

  2. Carbonaceous chondrites. II - Carbonaceous chondrite phyllosilicates and light element geochemistry as indicators of parent body processes and surface conditions

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Chang, S.

    1980-01-01

    Petrographic analyses of CM matrices characterized four phyllosilicates in Murray and Murchison meteorites and Fe- and Mg-serpentines in Nogoya. All phyllosilicates and bulk matrices show enrichment of K relative to Na when compared with bulk meteorites; the loss of Na and some Cl, and the addition of H2O, CO2, and water-soluble organics during alteration indicates a partially open system. Synthesis of soluble organic materials may have occurred in CM matrices before aqueous alteration of the precursive phases. Nogoya was 95% altered and has a bulk C content of 5.2%, higher than any meteorite; also, it has the lowest measured C-13/C-12 ratio of any carbonaceous chondrite except for Karoonda.

  3. Chemical studies of L-chondrites. I - A study of possible chemical sub-groups

    NASA Astrophysics Data System (ADS)

    Neal, C. W.; Dodd, R. T.; Jarosewich, E.; Lipschutz, M. E.

    1981-06-01

    Radiochemical neutron activation analysis of Ag, As, Au, Bi, Co, Cs, Ga, In, Rb, Sb, Te, Tl and Zn and major element data in 14 L4-6 and 3 LL5 chondrites indicates that the L-group is unusually variable and may represent at least 2 sub-groups differing in formation history. Chemical trends in the S/Fe-rich sub-group support textural evidence indicating late loss of a shock-formed Fe-Ni-S melt; the S/Fe-poor sub-group seemingly reflects nebular fractionation only. Highly mobile In and Zn apparently reflect shock-induced loss from L-chondrites. Data for L5 chondrites suggest higher formation temperatures and/or degrees of shock than for LL5 chondrites.

  4. Evidence for Impact Shock Melting in CM and CI Chondrite Regolith Samples

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Komatsu, Mutsumi; Le, Loan

    2014-01-01

    C class asteroids frequently exhibit reflectance spectra consistent with thermally metamorphosed carbonaceous chondrites, or a mixture of phyllosilicate-rich material along with regions where they are absent. One particularly important example appears to be near-Earth asteroid 1999 JU3, the target of the Hayabusa II sample return mission [1], although not all spectra indicate this. In fact most spectra of 1999 JU3 are featureless, suggesting a heterogeneous regolith. Here we explore an alternative cause of dehydration of regolith of C class asteroids - impact shock melting. Impact shock melting has been proposed to explain some mineralogical characteristics of CB chondrites, but has not been considered a major process for hydrous carbonaceous chondrites. What evidence is there for significant shock melting in the very abundant CMs, or less abundant but still important CI chondrites?

  5. Northwest Africa 5958: A weakly altered CM-related ungrouped chondrite, not a CI3

    NASA Astrophysics Data System (ADS)

    Jacquet, Emmanuel; Barrat, Jean-Alix; Beck, Pierre; Caste, Florent; Gattacceca, JéRôMe; Sonzogni, Corinne; Gounelle, Matthieu

    2016-05-01

    Northwest Africa (NWA) 5958 is a carbonaceous chondrite found in Morocco in 2009. Preliminary chemical and isotopic data leading to its initial classification as C3.0 ungrouped have prompted us to conduct a multitechnique study of this meteorite and present a general description here. The petrography and chemistry of NWA 5958 is most similar to a CM chondrite, with a low degree of aqueous alteration, apparently under oxidizing conditions, and evidence of a second, limited alteration episode manifested by alteration fronts. The oxygen isotopic composition, with ∆'17O = -4.3‰, is more 16O-rich than all CM chondrites, indicating, along with other compositional arguments, a separate parent body of origin. We suggest that NWA 5958 be reclassified as an ungrouped carbonaceous chondrite related to the CM group.

  6. CM chondrites exhibit the complete petrologic range from type 2 to 1

    NASA Astrophysics Data System (ADS)

    Zolensky, Michael E.; Mittlefehldt, David W.; Lipschutz, Michael E.; Wang, Ming-Sheng; Clayton, Robert N.; Mayeda, Toshiko K.; Grady, Monica M.; Pillinger, Colin; Barber, David

    1997-12-01

    The most phyllosilicate-rich members of the CM chondrite group were characterized. The possibility that the so-called C1 lithologic units in highly brecciated CM2 chondrites such as Cold Bokkeveld are actually completely hydrated CM2 chondrites is investigated. Accordingly, all sections of CMs available to the researchers were searched in order to locate additional highly processed lithologies. Several CM chondrites are briefly described which have greater proportions of matrix and phyllosilicates and smaller quantities of olivines and pyroxenes than is typical. Three completely hydrated CMs have also been identified and are called CM1s. These include EET 83334, ALH 88045, and a peculiar lithology in Kaidun (Zolensky et al., 1996b). How these lithologies further constrain physicochemical conditions on hydrous asteroids is described.

  7. Mars as the Parent Body for the CI Carbonaceous Chondrites: Confirmation of Early Mars Biology

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. E.

    2003-07-01

    Mounting evidence suggests that CI Carbonaceaous Chondrites belong in the Mars meteorite family. They thus represent samples, like ALH84001, of the Noachian surface environment, and are rich in organic matter, suggesting a living environment.

  8. Chondrule Formation Mechanisms in Protoplanetary Disks from Textural and Mineralogical Evidence Preserved in Unequilibrated Chondrites

    NASA Astrophysics Data System (ADS)

    Trigo-Rodriguez, J. M.; Martinez-Jimenez, M.; Tanbakouei, S.

    2016-08-01

    We study the chondrule size distribution of pristine chondrites in order to explore if it mimics that one expected from splattering due to stochastic collisions, or from thermal coagulation of micron-sized dust available in the protoplanetary disk.

  9. Implications of Shock Features in the Amphibole- and Mica-Bearing R Chondrites

    NASA Astrophysics Data System (ADS)

    Rubin, A. E.

    2013-09-01

    The amphibole- and mica-bearing R6 chondrites have distinct shock features consistent with formation near the asteroid surface. They may have been hydrated at elevated temperatures beneath an impermeable compressed zone below a large impact crater.

  10. Enstatite chondrites and enstatite achondrites (aubrites) were not derived from the same parent body

    USGS Publications Warehouse

    Brett, R.; Keil, Klaus

    1986-01-01

    Enstatite achondrites (aubrites) were not derived from known enstatite chondrites by melting and fractionation on one and the same parent body, for these and other reasons: (1) There is no satisfactory mechanism for fractionating metal plus troilite in enstatite chondrites to form these phases in different proportions and with different Ti contents in aubrites. (2) Many enstatite chondrites and aubrites are regolith or fragmental breccias, but clasts of one within the other have not been found. (3) Cosmic ray exposure ages of the two groups are difficult to explain if they are from the same parent body, but are easy to explain if they are from different parent bodies. Siderophile element abundances in metal from the Mt. Egerton meteorite, which consists of enstatite and metallic Fe,Ni, preclude it from being a complementary differentiate of the aubrites. Rather, it appears that Mt. Egerton was formed from the same source material as enstatite chondrites, but the components were mixed in different proportions. ?? 1986.

  11. First investigation of noble gases in the Dengli H3,8 chondrite

    NASA Technical Reports Server (NTRS)

    Ivanova, M. A.; Assonov, S. S.; Shukolyukov, Yu. A.

    1993-01-01

    The Dengli (H3,8) meteorite, which weighs 243.5 g, is a find from the Karakum desert. It is a complex microbreccia containing unusual clasts which are more typical for regolithic breccias than for H-chondrites. Based on comparisons of Xe and Kr content and isotopic composition, the Dengli does not differ significantly from other H-chondrites. Its exposure age is 7.6 Ma. That is in agreement with common data for the exposure age (6.2 + 0.2 Ma) of 350 H-chondrites. Dengli's K/Ar age (4.01 Ga) coincides with the same ages of many other H-chondrites. Thus the Dengli is not regolithic breccia, and it probably formed during accretion of its parent body.

  12. Titanium and Oxygen Isotope Compositions of Individual Chondrules from Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Bauer, K. K.; Schönbächler, M.; Fehr, M. A.; Vennemann, T.; Chaumard, N.; Zanda, B.

    2016-08-01

    We measured Ti and triple-O isotope compositions of individual chondrules (characterized by CT scanning) from ordinary chondrites. We will discuss correlations between Ti and ∆17O and their implication for the origin of nucleosynthetic anomalies.

  13. 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.

  14. Formation of Secondary Ca-Fe-Rich Assemblages in CV Chondrites

    NASA Astrophysics Data System (ADS)

    Ganino, C.; Libourel, G.

    2016-08-01

    Chondrites have multiplied evidences for metasomatic processes during the early solar system formation. Diversity in secondary Ca-Fe silicate provides information on T-X conditions and the open/closed-system behavior.

  15. A Three-Dimensional Survey of Metal Grain Size Distributions in Ordinary Chondrites: Effects of Metamorphism

    NASA Astrophysics Data System (ADS)

    Almeida, N. V.; Krzesińska, A.; Smith, C. L.; Downes, H.; Russell, S. S.

    2016-08-01

    Using X-ray micro-computed tomography, we have measured the volumes of metal grains in a selection of ordinary chondrites in order to investigate which trends are linked to static or impact metamorphism.

  16. Ordinary Chondrites of Chelyabinsk Meteorite and Comparison with Asteroid 25143 (Itokawa)

    NASA Astrophysics Data System (ADS)

    Voropaev, S.; Kocherov, A.; Korochantsev, A.; Petukhov, D.; Kaeter, D.; Ziemann, M.; Boettger, U.

    2016-08-01

    Itokawa and Chelyabinsk present unique opportunities for direct geochemical investigation of LL chondrites genesis and dynamical evolution. We compared data concerning theirs mineral phases in rock particles by means of Raman and SEM-EDX facilities.

  17. Fe and Ni Isotope Composition of Metal Grains from CH and CB Chondrites

    NASA Astrophysics Data System (ADS)

    Weyrauch, M.; Weyer, S.; Zipfel, J.

    2016-08-01

    Early condensates may be represented by zoned metals in CH and CBb chondrites. They display higher concentrations of Ni and more refractory elements in cores than in rims, and lighter Fe and Ni isotope signatures in cores than in rims.

  18. The early solar system abundance of Pu-244 as inferred from the St. Severin chondrite

    NASA Technical Reports Server (NTRS)

    Hudson, G. B.; Kennedy, B. M.; Podosek, F. A.; Hohenberg, C. M.

    1989-01-01

    The isotopic composition of Xe released in stepwise heating of neutron-irradiated samples of the St. Severin chondrite was measured. This analysis shows that at the time of formation of most chondritic meteorites, approximately 4.56 x 10 to the 9th yr ago, the atomic ratio of Pu-244/U-238 was 0.0068 + or - 0.0010 in chondritic meteorites. This value is believed to be more reliable that inferred from earlier analyses of St. Severin and is the best estimate for the early solar system abundance of Pu-244. The comparison of Xe compositions between irradiated and unirradiated samples shows that the composition of trapped (ambient) Xe in St. Severin has a significantly lower value of Xe-136/Xe-130 than average carbonaceous chondrites.

  19. 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.

  20. 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.

  1. Preservation of ancient impact ages on the R chondrite parent body: 40Ar/39Ar age of hornblende-bearing R chondrite LAP 04840

    NASA Astrophysics Data System (ADS)

    Righter, K.; Cosca, M. A.; Morgan, L. E.

    2016-09-01

    The hornblende- and biotite-bearing R chondrite LAP 04840 is a rare kind of meteorite possibly containing outer solar system water stored during metamorphism or postshock annealing deep within an asteroid. Because little is known regarding its age and origin, we determined 40Ar/39Ar ages on hornblende-rich separates of the meteorite, and obtained plateau ages of 4340(±40) to 4380(±30) Ma. These well-defined plateau ages, coupled with evidence for postshock annealing, indicate this meteorite records an ancient shock event and subsequent annealing. The age of 4340-4380 Ma (or 4.34-4.38 Ga) for this and other previously dated R chondrites is much older than most impact events recorded by ordinary chondrites and points to an ancient event or events that predated the late heavy bombardment that is recorded in so many meteorites and lunar samples.

  2. Preservation of ancient impact ages on the R chondrite parent body: 40Ar/39Ar age of hornblende-bearing R chondrite LAP 04840

    NASA Astrophysics Data System (ADS)

    Righter, K.; Cosca, M. A.; Morgan, L. E.

    2016-07-01

    The hornblende- and biotite-bearing R chondrite LAP 04840 is a rare kind of meteorite possibly containing outer solar system water stored during metamorphism or postshock annealing deep within an asteroid. Because little is known regarding its age and origin, we determined 40Ar/39Ar ages on hornblende-rich separates of the meteorite, and obtained plateau ages of 4340(±40) to 4380(±30) Ma. These well-defined plateau ages, coupled with evidence for postshock annealing, indicate this meteorite records an ancient shock event and subsequent annealing. The age of 4340-4380 Ma (or 4.34-4.38 Ga) for this and other previously dated R chondrites is much older than most impact events recorded by ordinary chondrites and points to an ancient event or events that predated the late heavy bombardment that is recorded in so many meteorites and lunar samples.

  3. Widespread evidence for high-temperature formation of pentlandite in chondrites

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Davidson, Jemma; McCoy, Timothy J.

    2016-09-01

    By investigating the compositional and textural evolution of sulfides within a wide range of relatively pristine, aqueously altered, and thermally metamorphosed chondrites we constrain the equilibration temperatures of sulfide minerals and compare them to the metamorphic history of their host meteorite. Sulfides in Mighei-like carbonaceous chondrites are complex as they equilibrated mostly between 100 and 135 °C, but some may have equilibrated at temperatures up to 600 °C. This is consistent with some CM chondrite sulfides forming at high temperature during chondrule cooling and others during low-temperature aqueous alteration and/or annealing. Karoonda-like carbonaceous chondrite sulfides equilibrated between 500 and 230 °C, which is consistent with formation during cooling and annealing after thermal metamorphism. Sulfides in the LL chondrites equilibrated between 600 and 230 °C, and are consistent with formation during chondrule cooling for Semarkona (LL3.00) and during cooling after thermal metamorphism for the equilibrated samples (types 4-6). Sulfides in the Rumuruti-like (R) chondrites equilibrated between 600 and 500 °C, and are consistent with formation after thermal metamorphism. The sulfides within the brachinite equilibrated between 600 and 400 °C, consistent with formation during cooling after thermal metamorphism. Contrary to the assertion that pentlandite is solely the product of low-temperature aqueous alteration in many chondrite groups, this study suggests that most sulfides in chondrites are formed at or upon cooling from high-temperature. The evaluation of a single mineral system within samples that retain petrographic context is vital to the interpretation of formation and alteration processes recorded by small extraterrestrial samples, such as those that have been returned by the spacecraft missions Stardust and Hayabusa and will be returned by OSIRIS-REx and Hayabusa2.

  4. 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.

  5. Chondrites: initial strontium-87/strontium-86 ratios and the early history of the solar system.

    PubMed

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

    1973-10-19

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

  6. Production of ferroan andesites by the experimental partial melting of an LL chondrite

    NASA Technical Reports Server (NTRS)

    Mcguire, J. C.; Jurewicz, A. J. G.; Jones, J. H.

    1994-01-01

    A partial melting experiment on the St. Severin (LL) chondrite produced a melt that was andesitic, having 54-60 wt% silica, at 1200 C and an oxygen fugacity of IW+2, two log units above the iron-wustite (IW) buffer. Under these same conditions, CV, CM, and L chondrites produced low-silica melts resembling angrites. This experimental study attempts to reproduce and explain this unusual result.

  7. Terrestrial ages, pairing, and concentration mechanism of Antarctic chondrites from Frontier Mountain, Northern Victoria Land

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Hillegonds, D. J.; Johnson, J. A.; Jull, A. J. T.; Wieler, R.; Folco, L.

    We report concentrations of cosmogenic 10Be, 26Al, 36Cl, and 41Ca in the metal phase of 26 ordinary chondrites from Frontier Mountain (FRO), Antarctica, as well as cosmogenic 14C in eight and noble gases in four bulk samples. Thirteen out of 14 selected H chondrites belong to two previously identified pairing groups, FRO 90001 and FRO 90174, with terrestrial ages of ˜40 and ˜100 kyr, respectively. The FRO 90174 shower is a heterogeneous H3-6 chondrite breccia that probably includes more than 300 individual fragments, explaining the high H/L chondrite ratio (3.8) at Frontier Mountain. The geographic distribution of 19 fragments of this shower constrains ice fluctuations over the past 50-100 kyr to less than ˜40 m, supporting the stability of the meteorite trap over the last glacial cycle. The second H-chondrite pairing group, FRO 90001, is much smaller and its geographic distribution is mainly controlled by wind-transport. Most L-chondrites are younger than 50 kyr, except for the FRO 93009/01172 pair, which has a terrestrial age of ˜500 kyr. These two old L chondrites represent the only surviving members of a large shower with a similar preatmospheric radius (˜80 cm) as the FRO 90174 shower. The find locations of these two paired L-chondrite fragments on opposite sides of Frontier Mountain confirm the general glaciological model in which the two ice flows passing both ends of the mountain are derived from the same source area on the plateau. The 50 FRO meteorites analyzed so far represent 21 different falls. The terrestrial ages range from 6 kyr to 500 kyr, supporting the earlier proposed concentration mechanism.

  8. Noble gases in the Bells (C2) and Sharps (H3) chondrites

    NASA Technical Reports Server (NTRS)

    Zadnik, M. G.

    1985-01-01

    The Bells and Sharps chondrites are of uncertain classification in virtue of their mineralogical and chemical peculiarities, prompting the present elemental and isotopic measurements of the noble gases in them, together with such quantities derivable from them as cosmogenic exposure and gas retention ages, as well as primordial gas contents. The radiogenic and, above all, the cosmogenic gases link Bells to the C2 group, while Sharps is found to lie in the second largest peak of the H-chondrite distribution.

  9. Studies of Brazilian meteorites. XIV - Mineralogy, petrology, and chemistry of the Conquista, Minas Gerais, chondrite

    NASA Technical Reports Server (NTRS)

    Keil, K.; Kirchner, E.; Gomes, C. B.; Jarosewich, E.; Murta, R. L. L.

    1978-01-01

    The Conquista chondrite is described and classified as an H4. The mineral composition is reported. H-group classification is based on described microscopic, electron microprobe, and bulk chemical studies. The evidence for petrologic type 4 classification includes the pronounced well-developed chondritic texture; the slight compositional variations in constituent phases; the high Ca contents of pyroxene and the presence of pigeonite; glassy to microcrystalline interstitial material rich in alkalis and SiO2; and twinned low-Ca clinopyroxene.

  10. The Osmium Isotopic Composition of Tagish Lake and Other Chondrites, Implications for Late Terrestrial Planetary Accretion

    NASA Technical Reports Server (NTRS)

    Brandon, A. D.

    2003-01-01

    The goals of this investigation are twofold. First, obtain high-precision Os isotope measurements of Tagish Lake and other chondrites by TIMS. Second, measure Re, Os, Pt, and other HSE concentrations by isotope dilution using TIMS and ICPMS. These measurements will determine whether this meteorite does in fact represent C-chondrite material with timeintegrated elevated Re/Os and Pt/Os with the implications to late accretion material characteristics.

  11. 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.

  12. Modal mineralogy of CI and CI-like chondrites by X-ray diffraction

    NASA Astrophysics Data System (ADS)

    King, A. J.; Schofield, P. F.; Howard, K. T.; Russell, S. S.

    2015-09-01

    The CI chondrites are some of the most hydrated meteorites available to study, making them ideal samples with which to investigate aqueous processes in the early Solar System. Here, we have used position-sensitive-detector X-ray diffraction (PSD-XRD) to quantify the abundance of minerals in bulk samples of the CI chondrite falls Alais, Orgueil and Ivuna, and the Antarctic CI-like chondrites Y-82162 and Y-980115. We find that Alais, Orgueil and Ivuna are dominated by a mixed serpentine/saponite phyllosilicate (81-84 vol%), plus minor magnetite (6-10%), sulphides (4-7%) and carbonates (<3%). This reflects an extended period of aqueous alteration and the near-complete transformation of anhydrous phases into a secondary mineral assemblage. The similarity in total abundance of phyllosilicate suggests that the CI chondrites all experienced the same degree of aqueous alteration on the parent body. In contrast, Y-82162 contains a highly disordered serpentine/saponite phyllosilicate (68 vol%), sulphide (19%), olivine (11%) and magnetite (2%). This mineralogy is distinct from that of the CI chondrites, attesting to both a different starting mineralogy and alteration history. The structure and relatively low abundance of the phyllosilicate, and the high abundance of olivine, are consistent with previous observations that Y-82162 represents CI-like material that following aqueous alteration suffered thermal metamorphism at temperatures >500 °C. Similarly, Y-980115 contains disordered serpentine/saponite (71 vol%), sulphide (19%), olivine (8%) and magnetite (2%), confirming that it too is a thermally metamorphosed CI-like chondrite. We suggest that the CI-like chondrites are derived from a different parent body than the CI chondrites, which underwent short-lived thermal metamorphism due to impacts and/or solar radiation.

  13. Restriction of parent body heating by metal-troilite melting: Thermal models for the ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Mare, Eleanor R.; Tomkins, Andrew G.; Godel, Belinda M.

    2014-04-01

    Ordinary chondrite meteorites contain silicates, Fe,Ni-metal grains, and troilite (FeS). Conjoined metal-troilite grains would be the first phase to melt during radiogenic heating in the parent body, if temperatures reached over approximately 910-960 °C (the Fe,Ni-FeS eutectic). On the basis of two-pyroxene thermometry of 13 ordinary chondrites, we argue that peak temperatures in some type 6 chondrites exceeded the Fe,Ni-FeS eutectic and thus conjoined metal-troilite grains would have begun to melt. Melting reactions consume energy, so thermal models were constructed to investigate the effect of melting on the thermal history of the H, L, and LL parent asteroids. We constrained the models by finding the proportions of conjoined metal-troilite grains in ordinary chondrites using high-resolution X-ray computed tomography. The models show that metal-troilite melting causes thermal buffering and inhibits the onset of silicate melting. Compared with models that ignore the effect of melting, our models predict longer cooling histories for the asteroids and accretion times that are earlier by 61, 124, or 113 kyr for the H, L, and LL asteroids, respectively. Because the Ni/Fe ratio of the metal and the bulk troilite/metal ratio is higher in L and LL chondrites than H chondrites, thermal buffering has the greatest effect in models for the L and LL chondrite parent bodies, and least effect for the H chondrite parent. Metal-troilite melting is also relevant to models of primitive achondrite parent bodies, particularly those that underwent only low degrees of silicate partial melting. Thermal models can predict proportions of petrologic types formed within an asteroid, but are systematically different from the statistics of meteorite collections. A sampling bias is interpreted to explain these differences.

  14. Textural evidence bearing on the origin of isolated olivine crystals in C2 carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Richardson, S. M.; Mcsween, H. Y., Jr.

    1978-01-01

    In some cases the mechanical competence of chondrules in carbonaceous chondrites has been reduced by alteration of their mesostasis glass to friable phyllosilicate, providing a mechanism by which euhedral olivines can be separated from chondrules. Morphological features of isolate olivine grains found in carbonaceous chondrites are similar to those of olivine phenocrysts in chondrules. These observations suggest that the isolated olivine grains formed in chondrules, by crystallization from a liquid, rather than by condensation from a vapor.

  15. 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.

  16. 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.

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

    DOE PAGES

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

    2015-06-23

    Here, 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 2.4 +1.8-1.3 Myr after calcium–aluminium-rich inclusions (CAIs), the oldest Solar System solids. In addition,more » measurements using our synthesized fayalite standard show that fayalite in the CV3 chondrite Asuka 881317 and CO3-like chondrite MacAlpine Hills 88107 formed and 4.2+0.8-0.7 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.« less

  18. 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.

  19. (40)Ar/(39)Ar Age of Hornblende-Bearing R Chondrite LAP 04840

    NASA Technical Reports Server (NTRS)

    Righter, K.; Cosca, M.

    2015-01-01

    Chondrites have a complex chronology due to several variables affecting and operating on chondritic parent bodies such as radiogenic heating, pressure and temperature variation with depth, aqueous alteration, and shock or impact heating. Unbrecciated chondrites can record ages from 4.56 to 4.4 Ga that represent cooling in small parent bodies. Some brecciated chondrites exhibit younger ages (much less than 4 to 4.4 Ga) that may reflect the age of brecciation, disturbance, or shock and impact events (much less than 4 Ga). A unique R chondrite was recently found in the LaPaz Icefield of Antarctica - LAP 04840. This chondrite contains approximately 15% hornblende and trace amounts of biotite, making it the first of its kind. Studies have revealed an equigranular texture, mineral equilibria yielding equilibration near 650-700 C and 250-500 bars, hornblende that is dominantly OH-bearing (very little Cl or F), and high D/H ratios. To help gain a better understanding of the origin of this unique sample, we have measured the (40)Ar/(39)Ar age (LAP 04840 split 39).

  20. On the Behavior of Phosphorus During the Aqueous Alteration of CM2 Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.; Chizmadia, Lysa J.

    2005-01-01

    During the earliest period of solar system formation, water played an important role in the evolution of primitive dust, both after accretion of planetesimals and possible before accretion within the protoplanetary disk. Many chondrites show evidence of variable degrees of aqueous alteration, the CM2 chondrites being among the most studied [1]. This group of chondrites is characterized by mineral assemblages of both primary and secondary alteration phases. Hence, these meteorites retain a particularly important record of the reactions that occurred between primary high temperature nebular phases and water. Studies of these chondrites can provide information on the conditions and environments of aqueous alteration and the mobility of elements during alteration. This latter question is at the core of a debate concerning the location of aqueous alteration, i.e. whether alteration occurred predominantly within a closed system after accretion (parent body alteration) or whether some degree of alteration occurred within the solar nebula or on ephemeral protoplanetary bodies prior to accretion. At the core of the parent body alteration model is the hypothesis that elemental exchange between different components, principally chondrules and matrix, must have occurred. chondrules and matrix, must have occurred. In this study, we focus on the behavior of the minor element, phosphorus. This study was stimulated by observations of the behavior of P during the earliest stages of alteration in glassy mesostasis in type II chondrules in CR chondrites and extends the preliminary observations of on Y791198 to other CM chondrites.

  1. 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

  2. Theoretical predictions of volatile bearing phases and volatile resources in some carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Ganguly, Jibamitra; Saxena, Surendra K.

    1989-01-01

    Carbonaceous chondrites are usually believed to be the primary constituents of near-Earth asteroids and Phobos and Diemos, and are potential resources of fuels which may be exploited for future planetary missions. The nature and abundances are calculated of the major volatile bearing and other phases, including the vapor phase that should form in C1 and C2 type carbonaceous chondrites as functions of pressure and temperature. The results suggest that talc, antigorite plus or minus magnesite are the major volatile bearing phases and are stable below 400 C at 1 bar in these chondritic compositions. Simulated heating of a kilogram of C2 chondrite at fixed bulk composition between 400 and 800 C at 1 bar yields about 135 gm of volatile, which is made primarily of H2O, H2, CH4, CO2 and CO. The relative abundances of these volatile species change as functions of temperature, and on a molar basis, H2 becomes the most dominant species above 500 C. In contrast, Cl chondrites yield about 306 gm of volatile under the same condition, which consist almost completely of 60 wt percent H2O and 40 wt percent CO2. Preliminary kinetic considerations suggest that equilibrium dehydration of hydrous phyllosilicates should be attainable within a few hours at 600 C. These results provide the framework for further analyses of the volatile and economic resource potentials of carbonaceous chondrites.

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

    SciTech Connect

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

    2015-06-23

    Here, 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 2.4 +1.8-1.3 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 4.2+0.8-0.7 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.

  4. 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).

  5. Relationship Between Iron Valence States of Serpentine in CM Chondrites and Their Aqueous Alteration Degrees

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; Zolensky, M.; Satake, W.; Le, L.

    2012-01-01

    The 0.6-0.7 micron absorption band observed for C-type asteroids is caused by the presence of Fe(3+) in phyllosilicates . Because Fe-bearing phyllosilicates, especially serpentine, are the most dominant product of aqueous alteration in the most abundant carbonaceous chondrites, CM chondrites, it is important to understand the crystal chemistry of serpentine in CM chondrites to better understand spectral features of C-type asteroids. CM chondrites show variable degrees of aqueous alteration, which should be related to iron valences in serpentine. It is predicted that the Fe(3+)/Sum of (Fe) ratios of serpentine in CM chondrites decrease as alteration proceeds by Si and Fe(3+) substitutions from end-member cronstedtite to serpentine, which should be apparent in the absorption intensity of the 0.6-0.7 micron band from C-type asteroids. In fact, the JAXA Hayabusa 2 target (C-type asteroid: 1993 JU3) exhibits heterogeneous spectral features (0.7 micron absorption band disappears by rotation). From these points of view, we have analyzed iron valences of matrix serpentine in several CM chondrites which span the entire observed range of aqueous alteration using Synchrotron Radiation X-ray Absorption Near-Edge Structure (SR-XANES). In this abstract we discuss the relationship between obtained Fe(3+)/Sum of (Fe) ratios and alteration degrees by adding new data to our previous studies

  6. Petrology and geochemistry of Patuxent Range 91501, a clast-poor impact-melt from the L chondrite parent body, and Lewis Cliff 88663, an L7 chondrite

    NASA Astrophysics Data System (ADS)

    Mittlefehldt, David W.; Lindstrom, Marilyn M.

    2001-03-01

    We have performed petrologic and geochemical studies of Patuxent Range 91501 and Lewis Cliff 88663. PAT 91501, originally classified as an L7 chondrite, is rather a unique, near total impact-melt from the L chondrite parent body. Lewis Cliff 88663 was originally classified as an "achondrite (?)," but we find that it is a very weakly shocked L7 chondrite. PAT 91501 is an unshocked, homogeneous, igneous-textured ultramafic rock composed of euhedral to subhedral olivine, low-Ca pyroxene, augite and chrome-rich spinels with interstitial albitic plagioclase and minor silica-alumina-alkali-rich glass. Only ~10% relict chondritic material is present. Olivine grains are homogeneous (Fa25.2-26.8). Low-Ca pyroxene (Wo1.9-7.2En71.9-78.2Fs19.9-20.9) and augite (Wo29.8-39.0En49.2-55.3Fs11.8-14.9) display a strong linear TiO2-Al2O3 correlations resulting from igneous fractionation. Plagioclase is variable in composition; Or3.0-7.7Ab79.8-84.1An8.2-17.2. Chrome-rich spinels are variable in composition and zoned from Cr-rich cores to Ti-Al-rich rims. Some have evolved compositions with up to 7.9 wt% TiO2. PAT 91501 bulk silicate has an L chondrite lithophile element composition except for depletions in Zn and Br. Siderophile and chalcophile elements are highly depleted due to sequestration in cm-size metal-troilite nodules. The minerals in LEW 88663 are more uniform in composition than those in PAT 91501. Olivine grains have low CaO and Cr2O3 contents similar to those in L5-6 chondrites. Pyroxenes have high TiO2 contents with only a diffuse TiO2-Al2O3 correlations. Low-Ca pyroxenes are less calcic (Wo1.6-3.1En76.5-77.0Fs20.4-21.4), while augites (Wo39.5-45.6En46.8-51.1Fs7.6-9.4) and plagioclases (Or2.6-5.7Ab74.1-83.1An11.2-23.3) are more calcic. Spinels are homogeneous and compositionally similar to those in L6 chondrites. LEW 88663 has an L chondrite bulk composition for lithophile elements, and only slight depletions in siderophile and chalcophile elements that are plausibly due

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

    NASA Astrophysics Data System (ADS)

    Sears, D. W. G.; Morse, A. D.; Hutchison, R.; Guimon, R. K.; Jie, Lu; Alexander, C. M. O'd.; Benoit, P. H.; Wright, I.; Pillinger, C.; Xie, Tian; Lipschutz, M. E.

    1995-03-01

    In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondrules, chondrules 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 Th data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B 1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group AS 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 ˜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 Th 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 chondrules, indicating metamorphism-related changes in the feldspar are responsible for the Th of the matrix. The Th data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence

  8. Interpretation of Ordinary Chondrites SNOM images: comparison with electromagnetic models

    NASA Astrophysics Data System (ADS)

    Longobardo, A.; Palomba, E.; Girasole, M.; Longo, G.; Pompeo, G.; Cricenti, A.

    2009-04-01

    To clarify the role of iron phase transformation induced in asteroid surfaces, we studied samples of Ordinary Chondrites of different types (different metallic content and shock degree) in laboratory, by means of the nanoimaging analytical technique SNOM (Scanning Near Field Optical Microscopy). In SNOM technique, a light beam is passed through an optical fiber, that ends in a tip. Tip width is smaller than light wavelength: in this way light passing through the aperture is confined by the dimension of the tip and hence a high spatial resolution (hundreds of nanometers) is obtained. Samples, whose dimensions are of micron order, is placed near the tip, in such a way that radiation emerging to the tip is forced to interact with it before diffracting out. Applying this technique, it's possible to retrieve a reflectivity image and a topographic image of the sample, having in this way evidence of npFe presence. Laboratory analysis is supported by theoretical modelling that is performed using a code that allows to obtain the electromagnetic fields distribution in 3D space, after interaction between radiation and sample, and hence a reflectivity image of the sample at a fixed wavelength. In the simulation, we consider a monochromatic plane wave addressed to a tip, 10 microns long and recovered by a thin silver layer. Sample, 700 nm far from the tip, is a 4mm2 square. In preliminary simulations, we chosen materials that are very common in Ordinary Chondrites such as the olivine (forsterite and fayalite) and pyroxenes. In the code every material is described by the following input parameters: isotropy, relative dielectric constant, magnetic permeability, electric, magnetic and thermal conductivity, opacity and density. Wavelengths considered here are 980 nm, 1050 nm, 1300 nm and 1550 nm, which correspond to maximum or minimum of olivine and pyroxenes reflectivity: in this way it's easier to have npFe evidence. The comparison between real and simulated SNOM reflectivity

  9. 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

  10. Thermal and impact history of the H chondrite parent asteroid during metamorphism: Constraints from metallic Fe-Ni

    NASA Astrophysics Data System (ADS)

    Scott, Edward R. D.; Krot, Tatiana V.; Goldstein, Joseph I.; Wakita, Shigeru

    2014-07-01

    We have studied cloudy taenite, metallographic cooling rates, and shock effects in 30 H3-6 chondrites to elucidate the thermal and early impact history of the H chondrite parent body. We focused on H chondrites with old Ar-Ar ages (>4.4 Gyr) and unshocked and mildly shocked H chondrites, as strongly shocked chondrites with such old ages are very rare. Cooling rates for most H chondrites at 500 °C are 10-50 °C/Myr and do not decrease systematically with increasing petrologic type as predicted by the onion-shell model in which types 3-5 are arranged in concentric layers around a type 6 core. Some type 4 chondrites cooled slower than some type 6 chondrites and type 3 chondrites did not cool faster than other types, contrary to the onion-shell model. Cloudy taenite particle sizes, which range from 40 to 120 nm, are inversely correlated with metallographic cooling rates and show that the latter were not compromised by shock heating. The three H4 chondrites that were used to develop the onion-shell model, Ste. Marguerite, Beaver Creek, and Forest Vale, cooled through 500 °C at ⩾5000 °C/Myr. Our thermal modeling shows that these rates are 50× higher than could be achieved in a body that was heated by 26Al and cooled without disturbance by impact. Published Ar-Ar ages do not decrease systematically with increasing petrologic type but do correlate inversely with cloudy taenite particle size suggesting that impact mixing decreased during metamorphism. Metal and silicate compositions in regolith breccias show that impacts mixed material after metamorphism without causing significant heating. Impacts during metamorphism created Portales Valley and two other H6 chondrites with large metallic veins, excavated the fast-cooled H4 chondrites around 3-4 Myr after accretion, and mixed petrologic types. Metallographic data do not require catastrophic disruption by impact during cooling.

  11. The Effects of Parent Body Processes on Amino Acids in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.

    2010-01-01

    To investigate the effect of parent body processes on the abundance, distribution, and enantiomeric composition of amino acids in carbonaceous chondrites, the water extracts from nine different powdered Cl, CM, and CR carbonaceous chondrites were analyzed for amino acids by ultrahigh performance liquid chromatography-fluorescence detection and time-of-flight mass spectrometry (UPLC-FD/ToF-MS). Four aqueously altered type 1 carbonaceous chondrites including Orgueil (C11), Meteorite Hills (MET) 01070 (CM1), Scott Glacier (SCO) 06043 (CM1), and Grosvenor Mountains (GRO) 95577 (CR1) were analyzed using this technique for the first time. Analyses of these meteorites revealed low levels of two- to five-carbon acyclic amino alkanoic acids with concentrations ranging from -1 to 2,700 parts-per-billion (ppb). The type 1 carbonaceous chondrites have a distinct distribution of the five-carbon (C5) amino acids with much higher relative abundances of the gamma- and delta-amino acids compared to the type 2 and type 3 carbonaceous chondrites, which are dominated by a-amino acids. Much higher amino acid abundances were found in the CM2 chondrites Murchison, Lonewolf Nunataks (LON) 94102, and Lewis Cliffs (LEW) 90500, the CR2 Elephant Moraine (EET) 92042, and the CR3 Queen Alexandra Range (QUE) 99177. For example, a-aminoisobutyric acid ((alpha-AIB) and isovaline were approximately 100 to 1000 times more abundant in the type 2 and 3 chondrites compared to the more aqueously altered type 1 chondrites. Most of the chiral amino acids identified in these meteorites were racemic, indicating an extraterrestrial abiotic origin. However, non-racemic isovaline was observed in the aqueously altered carbonaceous chondrites Murchison, Orgueil, SCO 06043, and GRO 95577 with L-isovaline excesses ranging from approximately 11 to 19%, whereas the most pristine, unaltered carbonaceous chondrites analyzed in this study had no detectable L-isovaline excesses. These results are consistent with the

  12. 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 ε182W compositions, whereas chondrule splits are characterized by high, but more variable, Hf/W ratios and ε182W 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 ε183W anomalies of several ε-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 ε182W 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

  13. 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

  14. The effects of parent body processes on amino acids in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Glavin, Daniel P.; Callahan, Michael P.; Dworkin, Jason P.; Elsila, Jamie E.

    2010-12-01

    To investigate the effect of parent body processes on the abundance, distribution, and enantiomeric composition of amino acids in carbonaceous chondrites, the water extracts from nine different powdered CI, CM, and CR carbonaceous chondrites were analyzed for amino acids by ultra performance liquid chromatography-fluorescence detection and time-of-flight mass spectrometry (UPLC-FD/ToF-MS). Four aqueously altered type 1 carbonaceous chondrites including Orgueil (CI1), Meteorite Hills (MET) 01070 (CM1), Scott Glacier (SCO) 06043 (CM1), and Grosvenor Mountains (GRO) 95577 (CR1) were analyzed using this technique for the first time. Analyses of these meteorites revealed low levels of two- to five-carbon acyclic amino alkanoic acids with concentrations ranging from approximately 1 to 2,700 parts-per-billion (ppb). The type 1 carbonaceous chondrites have a distinct distribution of the five-carbon (C5) amino acids with much higher relative abundances of the γ- and δ-amino acids compared to the type 2 and type 3 carbonaceous chondrites, which are dominated by α-amino acids. Much higher amino acid abundances were found in the CM2 chondrites Murchison, Lonewolf Nunataks (LON) 94102, and Lewis Cliffs (LEW) 90500, the CR2 Elephant Moraine (EET) 92042, and the CR3 Queen Alexandra Range (QUE) 99177. For example, α-aminoisobutyric acid (α-AIB) and isovaline were approximately 100 to 1000 times more abundant in the type 2 and 3 chondrites compared to the more aqueously altered type 1 chondrites. Most of the chiral amino acids identified in these meteorites were racemic, indicating an extraterrestrial abiotic origin. However, nonracemic isovaline was observed in the aqueously altered carbonaceous chondrites Murchison, Orgueil, SCO 06043, and GRO 95577 with L-isovaline excesses ranging from approximately 11 to 19%, whereas the most pristine, unaltered carbonaceous chondrites analyzed in this study had no detectable L-isovaline excesses. These results are consistent with the

  15. Magnetite in the unequilibrated CK chondrites: Implications for metamorphism and new insights into the relationship between the CV and CK chondrites

    NASA Astrophysics Data System (ADS)

    Dunn, Tasha L.; Gross, Juliane; Ivanova, Marina A.; Runyon, Simone E.; Bruck, Andrea M.

    2016-09-01

    Bulk isotopic and elemental compositions of CV and CK chondrites have led to the suggestion that both originate from the same asteroid. It has been argued that magnetite compositions also support this model; however, magnetite has been studied almost exclusively in the equilibrated (type 4-6) CKs. Magnetite in seven unequilibrated CKs analyzed here is enriched in MgO, TiO2, and Al2O3 relative to the equilibrated CKs, suggesting that magnetite compositions are affected by metamorphism. Magnetite in CKs is compositionally distinct from CVs, particularly in abundances of Cr2O3, NiO, and TiO2. Although there are minor similarities between CV and equilibrated CK chondrite magnetite, this is contrary to what we would expect if the CVs and CKs represent a single metamorphic sequence. CV magnetite should resemble CK3 magnetite, as both were metamorphosed to type 3 conditions. Oxygen fugacities and temperatures of CVox and CK chondrites are also difficult to reconcile using existing CV-CK parent body models. Mineral chemistries, which eliminate issues of bulk sample heterogeneity, provide a reliable alternative to techniques that involve a small amount of sample material. CV and CK chondrite magnetite has distinct compositional differences that cannot be explained by metamorphism.

  16. Survey of chondrule average properties in H-, L-, and LL-group chondrites - Are chondrules the same in all unequilibrated ordinary chondrites?

    NASA Technical Reports Server (NTRS)

    Gooding, J. L.

    1983-01-01

    The petrogenetic properties of chondrules in different unequilibrated ordinary chondrites (UOCs) are compared to averaged chondrule-suite values obtained from recent analyses of several H-group, L-group, and LL-group chondrites. The purpose of the study was to develop a data base for future statistical analyses of chondrite characteristics. Mean end-member compositions of olivine (mol percent Fa) and pyroxene (mol percent Fs) were used as indices of the relative degree of 'equilibration' of each chondrule suite. It is found that the bulk chondrule geometric-mean abundances of Na, Mg, and Ni are the same from one UOC to another, and show no major systematic trends related to the H-group, L-group, of LL-group parentage of the host chondrites. The patterns of rare-earth element abundances in the chondrules are also examined, and the results are compared with statistical analyses. It is concluded that multivariate statistical analysis of pooled UOC chondrule data is justified for chondrule bulk compositions, as long as the statistical results are not misinterpreted as the primary petrogenetic features of chondrules.

  17. Magnetite in the unequilibrated CK chondrites: Implications for metamorphism and new insights into the relationship between the CV and CK chondrites

    NASA Astrophysics Data System (ADS)

    Dunn, Tasha L.; Gross, Juliane; Ivanova, Marina A.; Runyon, Simone E.; Bruck, Andrea M.

    2016-07-01

    Bulk isotopic and elemental compositions of CV and CK chondrites have led to the suggestion that both originate from the same asteroid. It has been argued that magnetite compositions also support this model; however, magnetite has been studied almost exclusively in the equilibrated (type 4-6) CKs. Magnetite in seven unequilibrated CKs analyzed here is enriched in MgO, TiO2, and Al2O3 relative to the equilibrated CKs, suggesting that magnetite compositions are affected by metamorphism. Magnetite in CKs is compositionally distinct from CVs, particularly in abundances of Cr2O3, NiO, and TiO2. Although there are minor similarities between CV and equilibrated CK chondrite magnetite, this is contrary to what we would expect if the CVs and CKs represent a single metamorphic sequence. CV magnetite should resemble CK3 magnetite, as both were metamorphosed to type 3 conditions. Oxygen fugacities and temperatures of CVox and CK chondrites are also difficult to reconcile using existing CV-CK parent body models. Mineral chemistries, which eliminate issues of bulk sample heterogeneity, provide a reliable alternative to techniques that involve a small amount of sample material. CV and CK chondrite magnetite has distinct compositional differences that cannot be explained by metamorphism.

  18. Heavily-hydrated lithic clasts in CH chondrites and the related, metal-rich chondrites Queen Alexandra Range 94411 and Hammadah al Hamra 237

    NASA Astrophysics Data System (ADS)

    Greshake, A.; Krot, A. N.; Meibom, A.; Weisberg, M. K.; Zolensky, M. E.; Keil, K.

    2002-02-01

    Fine-grained, heavily-hydrated lithic clasts in the metal-rich (CB) chondrites Queen Alexandra Range (QUE) 94411 and Hammadah al Hamra 237 and CH chondrites, such as Patuxent Range (PAT) 91546 and Allan Hills (ALH) 85085, are mineralogically similar suggesting genetic relationship between these meteorites. These clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite, prismatic sulfides (pentlandite and pyrrhotite), and Fe-Mn-Mg-bearing Ca-carbonates set in a phyllosilicate-rich matrix. Two types of phyllosilicates were identified: serpentine, with basal spacing of ?0.73 nm, and saponite, with basal spacings of about 1.1-1.2 nm. Chondrules and FeNi-metal grains in CB and CH chondrites are believed to have formed at high temperature (>1300 K) by condensation in a solar nebula region that experienced complete vaporization. The absence of aqueous alteration of chondrules and metal grains in CB and CH chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the CH and CB parent bodies. The hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and FeNi-metal grains after these high-temperature components had been transported from their hot formation region to a much colder region of the solar nebula.

  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. Porosity of an Anhydrous Chondritic Interplanetary Dust Particle

    NASA Astrophysics Data System (ADS)

    Strait, M. M.; Thomas, K. L.; McKay, D. S.

    1995-09-01

    Determination of the density and porosity of Interplanetary Dust Particles (IDPs) is important in the dynamics of collisional and orbital evolution of small-sized particles. These measurements are also useful to suggest possible sources for IDPs based on comparisons with known extraterrestrial materials (e.g., chondrites). Previous work on IDPs shows a wide range of densities from very low (0.08 g/cm3 [1]) through low (0.3 g/cm3 [2]) to high (6.2 g/cm3 [3]), with an average density at 2.0 g/cm3 for 150 particles [2]. In another study, IDPs fall into two distinct density groups with mean values of 0.6 g/cm3 and 1.9g/cm3 [3]. In general, chondritic IDPs with lower density values most likely have appreciable porosity, suggesting they are primitive, uncompacted particles. It is believed that porosities greater than 70% are rare [2]. Sample In this study, porosity measurements were determined for one IDP, Clu17. This chondritic particle is a fragment of a large-sized IDP (L2008#5) known as a cluster particle. The cluster is composed of 53 fragments >5 micrometers in diameter; a detailed description of the cluster is given in [4]. IDP Clu17 has ~12 wt.% C and contains chondritic abundances (within 2xCI) for major elements. This fragment is dominated by fine-grained aggregates, also known as GEMS (glass with embedded metal and sulfide [5]), and contains some olivine, pyroxene, Fe-Ni sulfides, and carbonaceous material. Methods IDP Clu17 was analyzed for light elements quantitatively analysis using scanning electron microscopy and thin-window energy dispersive spectrometry [details of technique in 4]. Following the initial bulk chemical analysis, the particle was embedded in epoxy, thin sectioned using an ultramicrotome, and examined with a JEOL 2000 FX transmission electron microscope. Many of the sections were not complete; individual grains in some sections are lost during microtoming. Photos from nine of the best sections were digitized by scanning at 1200 dpi. The

  1. No nebular magnetization in the Allende CV carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Fu, R. R.; Lima, E. A.; Weiss, B. P.

    2014-10-01

    Magnetic fields in the solar nebula may have played a central role in mass and angular momentum transport in the protosolar disk and facilitated the accretion of the first planetesimals. Thought to be key evidence for this hypothesis is the high unblocking-temperature, randomly oriented magnetization in chondrules in the Allende CV carbonaceous chondrite. However, it has recently been realized that most of the ferromagnetic minerals in Allende are products of secondary processes on the parent planetesimal. Here we reevaluate the pre-accretional magnetism hypothesis for Allende using new paleomagnetic analyses of chondrules including the first measurements of mutually oriented subsamples from within individual chondrules. We confirm that Allende chondrules carry a high-temperature component of magnetization that is randomly oriented among chondrules. However, we find that subsamples of individual chondrules are also non-unidirectionally magnetized. Therefore, the high-temperature magnetization in Allende chondrules is not a record of nebular magnetic fields and is instead best explained by remagnetization during metasomatism in a <8 μT magnetic field. This low field intensity suggests that any core dynamo on the CV parent body decayed before the end of metasomatism, likely <40 My after the formation of calcium aluminum-rich inclusions (CAIs). Despite widespread practice, the magnetization in Allende should not be used to constrain magnetic fields in the protosolar nebula.

  2. Microstructure and Thermal History of Metal Particles in CH Chondrites

    NASA Technical Reports Server (NTRS)

    Goldstein, J. I.; Jones, R. H.; Kotula, P. G.; Michael, J. R.

    2005-01-01

    Fe-Ni metal particles with smooth Ni, Co, and Cr zoning patterns, 8-13 wt.% Ni in the center of the particle to 3-5 wt% Ni at the rim, have been identified in several CR-clan (CH, Bencubbinlike, and CR) chondrites. These zoning patterns are broadly consistent with an origin by gas-solid condensation in the solar nebula at temperatures between approximately 1500 to 1300 K and fast cooling rates, 2 to 25 K/day. Apparently, this condensate metal was not melted during chondrule formation or affected significantly in the solid-state by alteration during parent body processing. Consideration of diffusional redistribution of Ni, Co, Cr and siderophile elements have further constrained the calculated condensation temperatures and cooling rates of the zoned condensates. These condensate metals have irregular shapes and vary in size from 50 to 350 m as revealed in some detail by optical and SEM techniques. In addition to zoned condensate particles, other types of metal particles have been observed. These include zoned condensates with exsolution-precipitates, unzoned homogeneous metal with no exsolution precipitates, unzoned metal exhibiting exsolution precipitates and high Ni metal grains.

  3. Primordial Molecular Cloud Material in Metal-Rich Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2016-03-01

    The menagerie of objects that make up our Solar System reflects the composition of the huge molecular cloud in which the Sun formed, a late addition of short-lived isotopes from an exploding supernova or stellar winds from a neighboring massive star, heating and/or alteration by water in growing planetesimals that modified and segregated the primordial components, and mixing throughout the Solar System. Outer Solar System objects, such as comets, have always been cold, hence minimizing the changes experienced by more processed objects. They are thought to preserve information about the molecular cloud. Elishevah Van Kooten (Natural History Museum of Denmark and the University of Copenhagen) and co-authors in Denmark and at the University of Hawai'i, measured the isotopic compositions of magnesium and chromium in metal-rich carbonaceous chondrites. They found that the meteorites preserve an isotopic signature of primordial molecular cloud materials, providing a potentially detailed record of the molecular cloud's composition and of materials that formed in the outer Solar System.

  4. Distinct Distribution of Purines in CM and CR Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Stern, Jennifer C.; Glavin, Daniel P.; Smith, Karen E.; Martin, Mildred G.; Dworkin, Jason P.

    2010-01-01

    Carbonaceous meteorites contain a diverse suite of organic molecules and delivered pre biotic organic compounds, including purines and pyrimidines, to the early Earth (and other planetary bodies), seeding it with the ingredients likely required for the first genetic material. We have investigated the distribution of nucleobases in six different CM and CR type carbonaceous chondrites, including fivc Antarctic meteorites never before analyzed for nucleobases. We employed a traditional formic acid extraction protocol and a recently developed solid phase extraction method to isolate nucleobases. We analyzed these extracts by high performance liquid chromatography with UV absorbance detection and tandem mass spectrometry (HPLC-UV -MS/MS) targeting the five canonical RNAIDNA bases and hypoxanthine and xanthine. We detected parts-per-billion levels of nucleobases in both CM and CR meteorites. The relative abundances of the purines found in Antarctic CM and CR meteorites were clearly distinct from each other suggesting that these compounds are not terrestrial contaminants. One likely source of these purines is formation by HCN oligomerization (with other small molecules) during aqueous alteration inside the meteorite parent body. The detection of the purines adenine (A), guanine (0), hypoxanthine (HX), and xanthine (X) in carbonaceous meteorites indicates that these compounds should have been available on the early Earth prior to the origin of the first genetic material.

  5. Lithium isotope compositions of chondrules, CAI and a dark inclusion from Allende and ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Seitz, Hans-Michael; Zipfel, Jutta; Brey, Gerhard P.; Ott, Ulrich

    2012-05-01

    Bulk carbonaceous and ordinary chondrites have distinct Li isotope compositions, indicating the existence of local reservoirs and distinct formation conditions in the early solar system. These differences may be also recorded in the components that compose chondrites. Here, Li concentrations and Li isotope compositions of 89 chondrules, 10 CAI and 1 dark inclusion (DI) from the Allende (CV3) meteorite and from 5 ordinary chondrites of low petrologic types Semarkona, Bishunpur, Saratov, Bjurböle and Bremervörde are presented. In general, chondrules have highly variable Li isotope compositions, ranging from δ7Li of - 8.5 to + 10‰, whereby the mean isotope composition of chondrules separated from a single chondrite is slightly lighter than its bulk. Remarkable, however, are the differences in Li concentrations between bulk chondrite and chondrules. Of the entire set studied here, 98% of the chondrules have significantly lower Li abundances (in the range of 0.2 to 0.75 μg/g) than their hosts (typically around 1.5 μg/g). Our results indicate that Li elemental and isotopic fractionation has not occurred extensively during chondrule formation. Low, but highly variable Li abundances as well as the relatively large range in Li isotopes point to small-scale heterogeneities in the chondrule-forming reservoir. With respect to Li, such a non-chondritic reservoir is unique to all chondrules. The compositional differences in Li isotopes between bulk carbonaceous and ordinary chondrites (Seitz et al., 2007) are likely to be the result of mixing chondrules, CAI and matrix in different proportions.

  6. Ar-40/Ar-39 Age of Hornblende-bearing R Chondrite LAP 04840

    NASA Technical Reports Server (NTRS)

    Righter, K.; Cosca, M.

    2014-01-01

    Chondrites have a complex chronology due to several variables affecting and operating on chondritic parent bodies such as radiogenic heating, pressure and temperature variation with depth, aqueous alteration, and shock or impact heating [1]. Unbrecciated chondrites can record ages from 4.56 to 4.4 Ga that represent cooling in small parent bodies. Some brecciated chondrites exhibit younger ages (<<4 to 4.4 Ga) that may reflect the age of brecciation, disturbance, or shock and impact events (<< 4 Ga). A unique R chondrite was recently found in the LaPaz Icefield of Antarctica - LAP 04840 [2]. This chondrite contains approx.15% hornblende and trace amounts of biotite, making it the first of its kind. Studies have revealed an equigranular texture, mineral equilibria yielding equilibration near 650-700 C and 250-500 bars, hornblende that is dominantly OH-bearing (very little Cl or F), and high D/H ratios [8,9,10]. To help gain a better understanding of the origin of this unique sample, we have measured the Ar-40/Ar-39 age. Age of 4.290 +/- 0.030 Ga is younger than one would expect for a sample that has cooled within a small body [4], and one might instead attribute the age to a younger shock event, On the other hand, there is no evidence for extensive shock in this meteorite (shock stage S2; [3]), so this sample may have been reannealed after the shock event. This age is similar to Ar-Ar ages determined for some other R chondrites

  7. Aqueous Alteration of Carbonaceous Chondrites: New Insights from Comparative Studies of Two Unbrecciated CM2 Chondrites, Y 791198 and ALH 81002

    NASA Technical Reports Server (NTRS)

    Chizmadia, L. J.; Brearley, A. J.

    2004-01-01

    Carbonaceous chondrites are an important resource for understanding the physical and chemical conditions in the early solar system. In particular, a long-standing question concerns the role of water in the cosmochemical evolution of carbonaceous chondrites. It is well established that extensive hydration of primary nebular phases occurred in the CM and CI chondrites, but the location where this alteration occurred remains controversial. In the CM2 chondrites, hydration formed secondary phases such as serpentine, tochilinite, pentlandite, carbonate and PCP. There are several textural observations which suggest that alteration occurred before the accretion of the final CM parent asteroid, i.e. preaccretionary alteration. Conversely, there is a significant body of evidence that supports parent-body alteration. In order to test these two competing hypotheses further, we studied two CM chondrites, Y-791198 and ALH81002, two meteorites that exhibit widely differing degrees of aqueous alteration. In addition, both meteorites have primary accretionary textures, i.e. experienced minimal asteroidal brecciation. Brecciation significantly complicates the task of unraveling alteration histories, mixing components that have been altered to different degrees from different locations on the same asteroidal parent body. Alteration in Y-791198 is mostly confined to chondrule mesostases, FeNi metal and fine-grained matrix and rims. In comparison, the primary chondrule silicates in ALH81002 have undergone extensive replacement by secondary hydrous phases. This study focuses on compositional and textural relationships between chondrule mesostasis and the associated rim materials. Our hypothesis is: both these components are highly susceptible to aqueous alteration and should be sensitive recorders of the alteration process. For parent body alteration, we expect systematic coupled mineralogical and compositional changes in rims and altered mesostasis, as elemental exchange between these

  8. Thermally Mobile Trace Elements in Carbonaceous Chondrites From Cold and Hot Deserts

    NASA Astrophysics Data System (ADS)

    Lipschutz, M. E.

    2000-01-01

    Some decades ago, Anders and co-workers used RNAA to classify a number of trace elements as being volatile during nebular condensation and accretion into primitive objects based upon their strong depletion in (equilibrated) ordinary chondrites relative to C1 chondrites. Such elements, e.g. Ag, Bi, Cd, Cs, In, Se, Te, Tl, Zn and others, exhibit nearly constant, C1-normalized atomic abundances in C2 (CM2) and in C3 chondrites. They interpreted the near-constancy of these abundances according to a 2-component model in which volatiles were introduced into carbonaceous (and other) chondrites as C1 material which was diluted with differing proportions of high-temperature (i.e. volatile-free) components. In this view, mean volatile element abundances of 0.48 in C2 and 0.24-0.29 x C1 in C3 chondrites indicated that C2 and C3 chondrites are, respectively, about 1:1 and 1:2-3 mixtures of C1-like and high temperature materials. More recently, Xiao and Lipschutz found that C-normalized abundances of such volatile elements are nearly constant in most C2-6 chondrites (i.e. 25 non-Antarctic meteorites, nearly all falls, and 36 Antarctic finds) consistent with a 2-component mixing model. However, rather than being quantized, mean volatile element contents in each chondrite define a continuum from 0.92-0.14 x C1 for these 61 chondrites. A few carbonaceous chondrites, the first having been the NIPR consortium samples B-7904, Y-82162 and Y-86720, show an altered pattern: many of the volatile elements in each exhibit the usual constancy of C1-normalized atomic abundances, but modified by further depletion of Cd and other elements like Tl and Bi. These are the most mobile trace elements, i.e. those most readily vaporized and lost from primitive meteorites during week-long heating at greater than or equal to 400 C under low ambient pressures (initially 10-5 atm H2), simulating metamorphic conditions in a primitive parent body. Similarities between mobile element data for B-7904, Y-82162

  9. 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

  10. Thermally Mobile Trace Elements in Carbonaceous Chondrites From Cold and Hot Deserts

    NASA Technical Reports Server (NTRS)

    Lipschutz, M. E.

    2000-01-01

    Some decades ago, Anders and co-workers used RNAA to classify a number of trace elements as being volatile during nebular condensation and accretion into primitive objects based upon their strong depletion in (equilibrated) ordinary chondrites relative to C1 chondrites. Such elements, e.g. Ag, Bi, Cd, Cs, In, Se, Te, Tl, Zn and others, exhibit nearly constant, C1-normalized atomic abundances in C2 (CM2) and in C3 chondrites. They interpreted the near-constancy of these abundances according to a 2-component model in which volatiles were introduced into carbonaceous (and other) chondrites as C1 material which was diluted with differing proportions of high-temperature (i.e. volatile-free) components. In this view, mean volatile element abundances of 0.48 in C2 and 0.24-0.29 x C1 in C3 chondrites indicated that C2 and C3 chondrites are, respectively, about 1:1 and 1:2-3 mixtures of C1-like and high temperature materials. More recently, Xiao and Lipschutz found that C-normalized abundances of such volatile elements are nearly constant in most C2-6 chondrites (i.e. 25 non-Antarctic meteorites, nearly all falls, and 36 Antarctic finds) consistent with a 2-component mixing model. However, rather than being quantized, mean volatile element contents in each chondrite define a continuum from 0.92-0.14 x C1 for these 61 chondrites. A few carbonaceous chondrites, the first having been the NIPR consortium samples B-7904, Y-82162 and Y-86720, show an altered pattern: many of the volatile elements in each exhibit the usual constancy of C1-normalized atomic abundances, but modified by further depletion of Cd and other elements like Tl and Bi. These are the most mobile trace elements, i.e. those most readily vaporized and lost from primitive meteorites during week-long heating at greater than or equal to 400 C under low ambient pressures (initially 10(exp -5) atm H2), simulating metamorphic conditions in a primitive parent body. Similarities between mobile element data for B-7904, Y

  11. Thermally Mobile Trace Elements in Carbonaceous Chondrites from Cold and Hot Deserts

    NASA Technical Reports Server (NTRS)

    Lipschutz, M. E.

    1999-01-01

    Some decades ago, Anders and co-workers used RNAA to classify a number of trace elements as being volatile during nebular condensation and accretion into primitive objects based upon their strong depletion in (equilibrated) ordinary chondrites relative to C1 chondrites. Such elements, e.g. Ag, Bi, Cd, Cs, In, Se, Te, Tl, Zn and others, exhibit nearly constant, C1-normalized atomic abundances in C2 (CM2) and in C3 chondrites. They interpreted the near-constancy of these abundances according to a 2-component model in which volatiles were introduced into carbonaceous (and other) chondrites as Cl material which was diluted with differing proportions of high-temperature (i.e. volatile-free) components. In this view, mean volatile element abundances of 0.48 in C2 and 0.24-0.29 x C1 in C3 chondrites indicated that C2 and C3 chondrites are, respectively, about 1:1 and 1:2-3 mixtures of Cl-like and high temperature materials. More recently, C1 normalized abundances of such volatile elements are nearly constant in most C2-6 chondrites (i.e. 25 non-Antarctic meteorites, nearly all falls, and 36 Antarctic finds) consistent with a 2- component mixing model. However, rather than being quantized, mean volatile element contents in each chondrite define a continuum from 0.92-0.14 x Cl for these 61 chondrites. A few carbonaceous chondrites - the first having been the NIPR consortium samples B-7904, Y-82162 and Y-86720 - show an altered pattern: many of the volatile elements in each exhibit the usual constancy of C1-normalized atomic abundances, but modified by further depletion of Cd and other elements like Tl and Bi. These are the most mobile trace elements, i.e. those most readily vaporized and lost from primitive meteorites during week-long heating at greater than or equal to 400 C under low ambient pressures (initially 10 (exp -5) atm H2), simulating metamorphic conditions in a primitive parent body. Similarities between mobile element data for B-7904, Y-82162 and Y-86720 with

  12. Chemical studies of H chondrites - 9: Volatile trace element composition and petrographic classification of equilibrated H chondrites

    NASA Astrophysics Data System (ADS)

    Wolf, Stephen F.; Lipschutz, Michael E.

    1998-03-01

    To examine the thermal history of the parent(s) of equilibrated H chondrites, we treated data for 11 volatile trace elements (Co, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, and In in order of putative volatility) in 90 falls: 15 H4; 46 H5, and 29 H6. Using univariate statistical tests, contents of few of these elements differ significantly between any two of these suites. One element, Cs, differs systematically between all 3 pairs of suites: Co and Tl differ between 2 pairs of suites. For Co and Cs, contents varied as H4>H5>H6 while for Tl, H4600 K, with the suites deriving from a stratified parent object(s).

  13. Collisional erosion and the non-chondritic composition of the terrestrial planets.

    PubMed

    O'Neill, Hugh St C; Palme, Herbert

    2008-11-28

    The compositional variations among the chondrites inform us about cosmochemical fractionation processes during condensation and aggregation of solid matter from the solar nebula. These fractionations include: (i) variable Mg-Si-RLE ratios (RLE: refractory lithophile element), (ii) depletions in elements more volatile than Mg, (iii) a cosmochemical metal-silicate fractionation, and (iv) variations in oxidation state. Moon- to Mars-sized planetary bodies, formed by rapid accretion of chondrite-like planetesimals in local feeding zones within 106 years, may exhibit some of these chemical variations. However, the next stage of planetary accretion is the growth of the terrestrial planets from approximately 102 embryos sourced across wide heliocentric distances, involving energetic collisions, in which material may be lost from a growing planet as well as gained. While this may result in averaging out of the 'chondritic' fractionations, it introduces two non-chondritic chemical fractionation processes: post-nebular volatilization and preferential collisional erosion. In the latter, geochemically enriched crust formed previously is preferentially lost. That post-nebular volatilization was widespread is demonstrated by the non-chondritic Mn/Na ratio in all the small, differentiated, rocky bodies for which we have basaltic samples, including the Moon and Mars. The bulk silicate Earth (BSE) has chondritic Mn/Na, but shows several other compositional features in its pattern of depletion of volatile elements suggestive of non-chondritic fractionation. The whole-Earth Fe/Mg ratio is 2.1+/-0.1, significantly greater than the solar ratio of 1.9+/-0.1, implying net collisional erosion of approximately 10 per cent silicate relative to metal during the Earth's accretion. If this collisional erosion preferentially removed differentiated crust, the assumption of chondritic ratios among all RLEs in the BSE would not be valid, with the BSE depleted in elements according to their

  14. Chemical studies of H chondrites. 4: New data and comparison of Antarctic suites

    NASA Astrophysics Data System (ADS)

    Wolf, Stephen F.; Lipschutz, Michael E.

    1995-02-01

    We report data for the trace elements Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Ti, and In (ordered by putative volatility during nebular condensation and accretion) determined by neutron activation analysis in 13 H5 chondrites from Victoria Land and 20 H4-6 chondrites from Queen Maud Land, Antarctica. These and earlier results provide Antarctic sample suites of 34 chondrites from Victoria Land and 25 from Queen Maud Land. Treatment of data for the most volatile 10 elements (Rb to In) in these studies by multivariate statistical techniques more robust, as well as more conservative, than conventional linear discriminant analysis and logistic regression demonstrates that compositions differ at marginally significant levels. This difference cannot be explained by trivial (terrestrial) causes and becomes more significant, despite the smaller size of the database, when comparisons are limited to data from a single analyst and when all upper limits are eliminated from consideration. The Victoria Land and Queen Maud Land suites have different mean terrestrial ages (approximately 300 kyr and approximately 100 kyr, respectively) and age distributions, suggesting that a time-dependent variation of chondritic sources with different thermal histories is responsible. As a result, these two Antarctic suites are, on average, chemically distinguishable from each other. Since H chondrites serve as a paradigm for other meteorite classes, these results indicate that the near-Earth populations of planetary materials varied with time on the 105-year timescale.

  15. Cosmogenic radionuclides and noble gases in Antarctic H chondrites with high and normal natural thermoluminescence levels

    NASA Astrophysics Data System (ADS)

    Mokos, Jennifer L.; Franke, Luitgard; Scherer, Peter; Schultz, Ludolf; Lipschutz, Michael E.

    2000-07-01

    We report noble gas data for 37 H chondrites collected from the Allan Hills by EUROMET in the 1988/1989 Field Season. Among these are 16 specimens with high levels (>100 krad) of natural thermoluminescence (NTL), originally interpreted as signaling their derivation from a single meteoroid with an orbit that became Earth-crossing -~100 ka ago. One of these 16 is an H3 with a cosmic ray exposure age of ~33 Ma and clearly represents a separate fall. The other 15 H4-6 chondrites derive from 3 separate meteoroids, each of which is represented by a 5- or 6-member group. These groups have mean exposure ages of 3.7, 4.1 and 6.6 Ma: the middle-group members all contain solar Ne. The 2 younger groups also seem to each include a few H chondrites with normal NTL levels. Measurements of cosmogenic 10Be (1.5 Ma), 26Al (710 ka) and 36Cl (301 ka) in 14 of the high NTL chondrites indicate that all reflect a simple irradiation history. In contrast, many of a different, 38-member, randomly-selected suite of Antarctic H chondrites seem to have different cosmic ray irradiation histories. The 3.7 and 6.6 Ma groups from the 37-member Allan Hills suite come, respectively, from about 5-30 cm and about 5-10 cm depths in 80-125 cm and 60-125 cm-radius meteoroids.

  16. Shape, metal abundance, chemistry, and origin of chondrules in the Renazzo (CR) chondrite

    SciTech Connect

    Ebel, D.S.; Weisberg, M.K.; Hertz, J.; Campbell, A.J.

    2009-03-31

    We used synchrotron X-ray microtomography to image in 3-dimensions (3D) eight whole chondrules in a {approx}1 cm{sup 3} piece of the Renazzo (CR) chondrite at {approx}17 {micro}m per volume element (voxel) edge. We report the first volumetric (3D) measurement of metal/silicate ratios in chondrules and quantify indices of chondrule sphericity. Volumetric metal abundances in whole chondrules range from 1 to 37 volume % in 8 measured chondrules and by inspection in tomography data. We show that metal abundances and metal grain locations in individual chondrules cannot be reliably obtained from single random 2D sections. Samples were physically cut to intersect representative chondrules multiple times and to verify 3D data. Detailed 2D chemical analysis combined with 3D data yield highly variable whole-chondrule Mg/Si ratios with a supra-chondritic mean value, yet the chemically diverse, independently formed chondrules are mutually complementary in preserving chondritic (solar) Fe/Si ratios in the aggregate CR chondrite. These results are consistent with localized chondrule formation and rapid accretion resulting in chondrule + matrix aggregates (meteorite parent bodies) that preserve the bulk chondritic composition of source regions.

  17. Isotopic anomalies of noble gases in meteorites and their origins. III - LL-chondrites

    NASA Technical Reports Server (NTRS)

    Alaerts, L.; Lewis, R. S.; Anders, E.

    1979-01-01

    Nine LL-chondrites were studied by selective etching to characterize the noble gas components in three mineral fractions: HF-HCl-solubles, chromite and carbon. The Ne-20/Ar-36 ratio is considered, noting that chondrites of different petrologic types cannot all be derived from the same volatile rich ancestor, but must have formed over a range of temperatures, with correspondingly different volatile contents. Variations in the carbonaceous chondrite fission (CCFXe) component in LL3, LL5, and LL6 chondrites are discussed, noting that if CCFXe comes from a supernova, then its distribution in LL-chondrites requires three presolar carrier minerals of the right solubility properties, containing three different xenon components. However, if CCFXe comes from fission of a volatile superheavy element, then its decrease from LL3 to LL6 can be attributed to less complete condensation from the solar nebula. Finally, the three types of primordial xenon components which occur in different minerals of the same meteorite are described.

  18. Mineralogy and petrology of two ordinary chondrites and their correlation with other meteorites

    NASA Astrophysics Data System (ADS)

    Owocki, Krzysztof; Pilski, Andrzej

    2009-01-01

    Two ordinary chondrites are compared and classified using transmitted and reflected light microscopy and electron microprobe analyses. Both meteorites were confiscated by the Polish Customs Service at the border with Belarus. The first meteorite (called in this paper Terespol-1) is a L/LL6 chondrite, its classification being supported by the equilibrated compositions of olivine and orthopyroxene and the presence of large recrystallized feldspars (< 150 μm). The specimen examined experienced weak shock metamorphism (S3) and moderate weathering (although metal in the inner part of the meteorite seems to be unaffected by oxidization). The other meteorite (called in this paper Terespol-2) is a LL6 chondrite which experienced weak shock metamorphism (S3) and is unaffected by weathering. The Terespol-2 meteorite shares its classification with the Dhofar 1401 chondrite but the lack of data prevents further correlation. Both meteorites have been correlated with known findings from the Meteoritical Bulletin database and an attempt is made to identify their place of origin (fall event). Results indicate that Terespol-1 is most closely related to the Dhofar 1316 chondrite and we suggest that both meteorites at least came from the same parent body.

  19. High Precision Oxygen Three Isotope Analysis of Wild-2 Particles and Anhydrous Chondritic Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Nakashima, D.; Ushikubo, T.; Zolensky, Michael E.; Weisberg, M. K.; Joswiak, D. J.; Brownlee, D. E.; Matrajt, G.; Kita, N. T.

    2011-01-01

    One of the most important discoveries from comet Wild-2 samples was observation of crystalline silicate particles that resemble chondrules and CAIs in carbonaceous chondrites. Previous oxygen isotope analyses of crystalline silicate terminal particles showed heterogeneous oxygen isotope ratios with delta(sup 18)O to approx. delta(sup 17)O down to -50% in the CAI-like particle Inti, a relict olivine grain in Gozen-sama, and an olivine particle. However, many Wild-2 particles as well as ferromagnesian silicates in anhydrous interplanetary dust particles (IDPs) showed Delta(sup 17)O values that cluster around -2%. In carbonaceous chondrites, chondrules seem to show two major isotope reservoirs with Delta(sup 17)O values at -5% and -2%. It was suggested that the Delta(sup 17)O = -2% is the common oxygen isotope reservoir for carbonaceous chondrite chondrules and cometary dust, from the outer asteroid belt to the Kuiper belt region. However, a larger dataset with high precision isotope analyses (+/-1-2%) is still needed to resolve the similarities or distinctions among Wild-2 particles, IDPs and chondrules in meteorites. We have made signifi-cant efforts to establish routine analyses of small particles (< or =10micronsm) at 1-2% precision using IMS-1280 at WiscSIMS laboratory. Here we report new results of high precision oxygen isotope analyses of Wild-2 particles and anhydrous chondritic IDPs, and discuss the relationship between the cometary dust and carbonaceous chondrite chondrules.

  20. A plausible link between the asteroid 21 Lutetia and CH carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Moyano-Cambero, Carles E.; Trigo-Rodriguez, Josep M.; Llorca, Jordi; Fornasier, Sonia; Barucci, Maria A.; Rimola, Albert

    2016-08-01

    A crucial topic in planetology research is establishing links between primitive meteorites and their parent asteroids. In this study, we investigate the feasibility of a connection between asteroids similar to 21 Lutetia, encountered by the Rosetta mission in July 2010, and the CH3 carbonaceous chondrite Pecora Escarpment 91467 (PCA 91467). Several spectra of this meteorite were acquired in the ultraviolet to near-infrared (0.3-2.2 μm) and in the midinfrared to thermal infrared (2.5-30.0 μm or 4000 to ~333 cm-1), and they are compared here to spectra from the asteroid 21 Lutetia. There are several similarities in absorption bands and overall spectral behavior between this CH3 meteorite and 21 Lutetia. Considering also that the bulk density of Lutetia is similar to that of CH chondrites, we suggest that this asteroid could be similar, or related to, the parent body of these meteorites, if not the parent body itself. However, the apparent surface diversity of Lutetia pointed out in previous studies indicates that it could simultaneously be related to other types of chondrites. Future discovery of additional unweathered CH chondrites could provide deeper insight in the possible connection between this family of metal-rich carbonaceous chondrites and 21 Lutetia or other featureless, possibly hydrated high-albedo asteroids.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  3. Origin of dark clasts in the Acfer 059/El Djouf 001 CR2 chondrite

    NASA Technical Reports Server (NTRS)

    Endreb, M.; Keil, K.; Bischoff, A.; Speitel, B.; Clayton, R. N.; Mayeda, T. K.

    1994-01-01

    The ten specimens of the paired Acfer 059/El Djouf 001 CR2 chondrite contain abundant lithic fragments which we refer to as dark clasts. Petrological and mineralogical studies reveal that they are not related to the CR2 host meteorite but are similar to dark clasts in other CR2 chondrites. Dark clasts consist of chondrule and mineral fragments, phyllosilicate fragments and clusters, magnetite, sulfides and accessory phases, embedded into a very fine-grained, phyllosilicate-rich matrix. Magnetite has morphologies known from CI chondrites: spherules, framboids and platelets. Average abundances of major elements in the dark clasts are mostly in the range of both CR and CV chondrites, but strong depletions in Na and S are apparent. Oxygen isotopic compositions of two dark clasts suggest relationships to type 3 carbonaceous chondrites and dark inclusions in Allende. The dark clasts are clearly different in texture and mineralogical compositions from the host matrix of Acfer 059/El Djouf 001. Therefore, these dark clasts are xenoliths and are quite unlike the Acfer 059/El Djouf 001 CR2 host meteorite. We suggest that dark clasts accreted at the same time with all other components during the formation of Acfer 059/El Djouf 001 whole rock.

  4. FIB-TEM Investigations of Fe-NI-Sulfides in the CI Chondrites Alais and Orgueil

    NASA Technical Reports Server (NTRS)

    Berger, Eve L.; Lauretta, D. S.; Zega, T. J.; Keller, L. P.

    2013-01-01

    The CI chondrites are primitive meteorites with bulk compositions matching the solar photosphere for all but the lightest elements. They have been extensively aqueously altered, and are composed primarily of fine-grained phyllosilicate matrix material which is host to carbonates, sulfates, sulfides, and minor amounts of olivine and pyroxene. The alteration, while extensive, is heterogeneous. For example, CI-chondrite cubanite and carbonate grains differ on mm to sub-mm scales, demonstrating multiple aqueous episodes. CI-chondrite variability is also evidenced by degree of brecciation, abundance and size of coarse-grained phyllosilicates, olivine and pyroxene abundance, as well as Ni-content and size of sulfide grains. Our previous work revealed Orgueil sulfide grains with variable Ni-contents, metal:S ratios, crystal structures and textures. We continue to explore the variability of CI-chondrite pyrrhotite (Po, (FeNi)1-xS) and pentlandite (Pn, (Fe,Ni)9S8) grains. We investigate the microstructure of sulfides within and among CI-chondrite meteorites in order to place constraints on the conditions under which they formed.

  5. Chemical compositions and classifica tion of five thermally altered carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Noronha, Bianca A.; Friedrich, Jon M.

    2014-08-01

    To establish the chemical group provenance of the five thermally altered carbonaceous chondrites Asuka (A-) 881551, Asuka-882113, Elephant Moraine (EET) 96026, Mulga (west), and Northwest Africa (NWA) 3133, we quantified 44 trace elements in each of them. We also analyzed Larkman Nunatak (LAR) 04318 (CK4), Miller Range (MIL) 090001 (CR2), Roberts Massif (RBT) 03522 (CK5) as reference samples as their chemical group affinity is already recognized. We conclude that Asuka-881551, Asuka-882113, and Mulga (west) are thermally metamorphosed CK chondrites. Compositionally, Elephant Moraine 96026 most resembles the CV chondrites. NWA 3133 is the most significantly thermally altered carbonaceous chondrite in our suite of samples. It is completely recrystallized (no chondrules or matrix remain), but its bulk composition is consistent with a CV-CK clan provenance. The thermally labile element (e.g., Se, Te, Zn, and Bi) depletion in NWA 3133 indicates a chemically open system during the heating episode. It remains unclear if the heat necessary for its thermal alteration of NWA 3133 was due to the decay of 26Al or was impact related. Finally, we infer that MIL 090001, Mulga (west), and NWA 3133 show occasional compositional signatures indicative of terrestrial alteration. The alteration is especially evident within the elements Sr, Ba, La, Ce, Th, U, and possibly Sb. Despite the alteration, we can still confidently place each of the altered chondrites within an established chemical group or clan.

  6. Chemical studies of H chondrites. 4: New data and comparison of Antarctic suites

    NASA Technical Reports Server (NTRS)

    Wolf, Stephen F.; Lipschutz, Michael E.

    1995-01-01

    We report data for the trace elements Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Ti, and In (ordered by putative volatility during nebular condensation and accretion) determined by neutron activation analysis in 13 H5 chondrites from Victoria Land and 20 H4-6 chondrites from Queen Maud Land, Antarctica. These and earlier results provide Antarctic sample suites of 34 chondrites from Victoria Land and 25 from Queen Maud Land. Treatment of data for the most volatile 10 elements (Rb to In) in these studies by multivariate statistical techniques more robust, as well as more conservative, than conventional linear discriminant analysis and logistic regression demonstrates that compositions differ at marginally significant levels. This difference cannot be explained by trivial (terrestrial) causes and becomes more significant, despite the smaller size of the database, when comparisons are limited to data from a single analyst and when all upper limits are eliminated from consideration. The Victoria Land and Queen Maud Land suites have different mean terrestrial ages (approximately 300 kyr and approximately 100 kyr, respectively) and age distributions, suggesting that a time-dependent variation of chondritic sources with different thermal histories is responsible. As a result, these two Antarctic suites are, on average, chemically distinguishable from each other. Since H chondrites serve as a paradigm for other meteorite classes, these results indicate that the near-Earth populations of planetary materials varied with time on the 10(exp 5)-year timescale.

  7. Contrasting Early and Late Shock Effects on the L Chondrite Parent Body: Evidence from Ar Ages and Olivine Microstructures for Two Meteorites

    NASA Astrophysics Data System (ADS)

    Ruzicka, A. M.; Clay, P. L.; Hugo, R.; Joy, K. H.; Busemann, H.

    2015-07-01

    We discuss Ar age and olivine microstructure data for two L6 chondrites that provide a case study of contrasting shock effects in similar chondritic materials deformed in different epochs and under different conditions.

  8. Diverse Anhydrous Silicates in a Fine-Grained Rim in the Weakly Altered CM2 Chondrite Queen Elizabeth Range 97990: Evidence for the Localized Preservation of Pristine Nebular Dust in CM Chondrites.

    NASA Astrophysics Data System (ADS)

    Brearley, A. J.

    2016-08-01

    A fine-grained rim the QUE 97990 CM2 chondrite contains diverse submicron crystalline anhydrous silicates, including olivines, low-Ca and high Ca pyroxenes and represents a more pristine sample of nebular dust than is present in most CM chondrites.

  9. Experimental shock metamorphism of the Murchison CM carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Tomeoka, Kazushige; Yamahana, Yasuhiro; Sekine, Toshimori

    1999-11-01

    A series of shock-recovery experiments were carried out on the Murchison CM carbonaceous chondrite by using a single-stage propellant gun. The Murchison samples were shocked in nine experiments at peak pressures from 4 to 49 GPa. The recovered samples were studied in detail by using an optical microscope, a scanning electron microscope and an electron-probe microanalyzer. Chondrules are flattened in the plane of the shock front at 4 to 30 GPa. The mean aspect ratio of chondrules increases from 1.17 to 1.57 roughly in proportion to the intensity of shock pressure up to ˜25 GPa. At 25 to 30 GPa, the mean aspect ratio does not increase further, and chondrules show increasingly more random orientations and degrade their preferred orientations, and at ˜35 GPa, they are extensively disrupted. Most coarse grains of olivine and pyroxene are irregularly fractured, fracture density increases with increasing shock pressure and at ˜30 GPa almost all are thoroughly fractured with subgrains of <1 to 5 μm in size. At ˜20 GPa, subparallel fractures begin to form in the matrix in directions roughly perpendicular to the compression axis and their densities increase with pressure, especially dramatically at 25 to 30 GPa; thus, the sample is increasingly comminuted and becomes fragile. Local shock melting occurs as melt veins and pockets at 20 to 30 GPa. Fracture-filling veins of fine grains of matrix are also produced at 25 to 30 GPa. The melts and the fine grains seem to result mainly from frictional heating due to displacement along fractures. At ˜35 GPa, melting occurs pervasively throughout the matrix. The melts are mainly produced from the matrix; however, they are consistently more enriched in Fe, S, and Ca, which indicates that these elements are selectively incorporated into the melts. The melts contain tiny spherules of Fe-Ni metal, Fe sulfide, and numerous vesicles. At 49 GPa, the matrix is totally melted and coarse grains of olivine are partially melted. The melts

  10. Rare Earth Element Fractionation During Evaporation of Chondritic Material

    NASA Astrophysics Data System (ADS)

    Wang, J.; Davis, A. M.; Clayton, R. N.

    1993-07-01

    Evaporation experiments suggest that enrichments in the heavy isotopes of oxygen, magnesium, and silicon in some CAIs are caused by kinetic effects during evaporation [1]. Volatility-fractionated REE patterns found in some CAIs have been modeled with some success using equilibrium thermodynamics [2,3], but little is known about kinetic effects on REE patterns. We have begun an investigation of REE fractionation under conditions where large isotope effects are produced by the kinetic isotope effect. We synthesized a starting material containing CI chondritic relative proportions of MgO, Al2O3, SiO2, CaO, TiO2, and FeO, and doped it with 100 ppm each of the REE. Samples of this material were evaporated in a vacuum furnace [4] at 10^-6 torr and 1800 or 2000 degrees C for periods of a few seconds to 5 hr. The mass fraction evaporated ranged from 7.6 to 95.4%. Most residues consist of olivine and glass. Chemical compositions of the residues were determined by electron and ion microprobe. Results for selected elements are shown in Fig. 1. There is no significant evaporation of Ca, Al, and Ti up to 95% mass loss; the evaporation behavior of Mg, Si, and Fe is similar to that found by Hashimoto [5]. There is no significant evaporation of most of the REE up to 95% mass loss. Ce is much more volatile than the other REE under these conditions: a tenfold negative Ce anomaly developed between 60 and 70% mass loss and the anomaly reached 5 X 10^-4 at 95% mass loss. A small Pr anomaly (50% Pr loss) also appeared in the highest-mass-loss residue. Thermodynamic calculations show that Ce has approximately the same volatility as other LREE under solar nebular oxygen fugacity, but is much more volatile than the other REE under oxidizing conditions [6]. We suspect that conditions in the residue in our vacuum evaporation experiments became oxidizing because evaporation reactions involving most major element oxides involve release of oxygen. The four known HAL-type hibonite

  11. A Re-Examination of Nucleobases in Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Martins, Z.; Botta, O.; de Vries, M.; Becker, L.; Ehrenfreund, E.

    The biomolecular building blocks of life, as we know it, are amino acids, purines and pyrimidines. The latter two form the bases of DNA and RNA, molecules that are used in the storage, transcription and translation of genetic information in all terrestrial organisms. A dedicated search for these compounds in meteorites can shed light on the origins of life in two ways: (i) Results can help assess the plausibility of extraterrestrial formation of prebiotic molecules followed by their meteoritic delivery to the early Earth. (ii) Such studies can also provide insights into possible prebiotic synthetic routes. We will search for these compounds in selected carbonaceous chondrites using formic acid extraction and reverse phase high performance liquid chromatography (HPLC) to isolate specific nucleobases from the bulk meteorite material as previously reported [1,2,3]. We will also use a new technique, resonant two-photon ionization mass spectrometry (R2PI) that can, not only identify organic compounds by their mass, but at the same time by their vibronic spectroscopy [4]. R2PI dramatically enhances the specificity for certain compounds (e.g. amino acids, nucleobases) and allows for distinction of structural isomers, tautomers and enantiomers as well as providing additional information due to isotope shifts. The optical spectroscopy can thus help us to further discriminate between terrestrial and extraterrestrial nucleobases. References: [1] Van Der Velden, W. and Schwarts, A. W. (1977) Geochim. Cosmochim. Acta, 41, 961-968. [2] Stoks, P. G. and Schwartz, A. W. (1979a) Nature, 282, 709-10. [3] Glavin, D. P. and Bada, J. L. (2004) In Lunar and Planetary Science XXXV, Abstract # 1022, Houston. [4] Nir, E., Grace, L. I., Brauer, B. and de Vries, M. S. (1999) Journal of the American Chemical Society, 121, 4896-4897.

  12. Chondritic xenon in the Earth’s mantle

    NASA Astrophysics Data System (ADS)

    Caracausi, Antonio; Avice, Guillaume; Burnard, Peter G.; Füri, Evelyn; Marty, Bernard

    2016-05-01

    Noble gas isotopes are powerful tracers of the origins of planetary volatiles, and the accretion and evolution of the Earth. The compositions of magmatic gases provide insights into the evolution of the Earth’s mantle and atmosphere. Despite recent analytical progress in the study of planetary materials and mantle-derived gases, the possible dual origin of the planetary gases in the mantle and the atmosphere remains unconstrained. Evidence relating to the relationship between the volatiles within our planet and the potential cosmochemical end-members is scarce. Here we show, using high-precision analysis of magmatic gas from the Eifel volcanic area (in Germany), that the light xenon isotopes identify a chondritic primordial component that differs from the precursor of atmospheric xenon. This is consistent with an asteroidal origin for the volatiles in the Earth’s mantle, and indicates that the volatiles in the atmosphere and mantle originated from distinct cosmochemical sources. Furthermore, our data are consistent with the origin of Eifel magmatism being a deep mantle plume. The corresponding mantle source has been isolated from the convective mantle since about 4.45 billion years ago, in agreement with models that predict the early isolation of mantle domains. Xenon isotope systematics support a clear distinction between mid-ocean-ridge and continental or oceanic plume sources, with chemical heterogeneities dating back to the Earth’s accretion. The deep reservoir now sampled by the Eifel gas had a lower volatile/refractory (iodine/plutonium) composition than the shallower mantle sampled by mid-ocean-ridge volcanism, highlighting the increasing contribution of volatile-rich material during the first tens of millions of years of terrestrial accretion.

  13. Thermal history of type-3 chondrites in the NASA antarctic collection

    NASA Astrophysics Data System (ADS)

    Bonal, L.; Quirico, E.; Montagnac, G.

    2014-07-01

    Chondrites are the most primitive meteorites. However, they were all modified in some ways by post-accretion geological processes operating on their asteroidal parent bodies. Hence, to decipher the formation(s) and origin(s) of their components, we must first understand how chondritic materials were modified in their asteroidal parent bodies. The modifications induced by secondary processes should not be underestimated and have to be precisely estimated before any interpretation of chondrite properties in terms of cosmochemistry. In particular, all chondrites contain some organic components that were potentially chemically and physically modified through post-accretion processes. A thin understanding of the induced evolution is required to allow for pertinent comparisons with other primitive extraterrestrial materials, such as cometary grains, to finally address questions such as the origin of organics in the Solar System. Type 3 chondrites experienced thermal metamorphism on their asteroidal parent body due to the radioactive decay of elements such as ^{26}Al. Temperatures higher than 300 °C were experienced on timescales of several thousands of years. Still, type 3 chondrites remain as unequilibrated rocks and common mineralogical thermometers cannot be applied. The polyaromatic carbonaceous matter is sensitive to thermal episodes (of long and short duration) experienced by the host meteorite. In particular, its structural order directly reflects the thermal history experienced on their parent bodies. The structural modification of the aromatic carbonaceous matter towards a higher order is irreversible, and independent of the mineralogy and degree of aqueous alteration. It is mainly controlled by the peak metamorphic temperature. Moreover, under the assumption of fairly similar organic precursors among chondrites of distinct groups, the structural order of polyaromatic organic matter allows for a direct comparison of their metamorphic grades. It is then possible

  14. Further Observations of Fe-60-Ni-60 and Mn-53-Cr-53 Isotopic Systems in Sulfides from Enstatite Chondrites

    NASA Technical Reports Server (NTRS)

    Guan, Y.; Huss, G. R.; Leshin, L. A.

    2004-01-01

    Recent studies have shown that short-lived Fe-60 (t(sub 1/2) = 1.5 Ma) was present in some components of ordinary and enstatite chondrites when they formed. Here we report additional data on Fe-60 from sulfides in enstatite chondrites and on the potential relationship between the Fe-60-Ni-60 and Mn-53-Cr-53 systems.

  15. Vacuum ultraviolet reflectance spectra of groups L, LL, and E chondrites and of achondrites

    NASA Technical Reports Server (NTRS)

    Wagner, J. K.; Cohen, A. J.; Hapke, B. W.; Partlow, W. D.

    1980-01-01

    The reflectance spectra of individual meteorites of all classes are being measured in the vacuum ultraviolet (VUV) spectral wavelength region from 89 to 248 nm to evaluate the potential of VUV spectroscopy as a remote sensing method for planetary studies. In the present investigation, specimens of 15 group L chondrites, 13 group LL chondrites, 7 group E chondrites, and 18 achondrites were studied. Spectra were measured of both polished thin sections and powders of the meteorites, where both were available. Attention is given to measurements of mineral standards, shock effects, and meteorite data. It is concluded that the VUV spectra of meteorites should provide a useful basis for comparisons with spectra of asteroids and comet nuclei taken from spacecraft. VUV spectroscopy should make it possible to identify the major minerals present in a meteorite or asteroid.

  16. Identification of solar nebula condensates in interplanetary dust particles and unequilibrated ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Kloeck, W.; Thomas, K. L.; Mckay, D. S.

    1989-01-01

    Orthopyroxene and olivine grains, low in FeO, but containing MnO contents up to 5 wt percent were found in interplanetary dust particles (IDP) collected in the stratosphere. The majority of olivines and pyroxenes in meteorites contain less than 0.5 wt percent MnO. Orthopyroxenes and olivines high in Mn and low in FeO have only been reported from a single coarse grained chondrule rim in the Allende meteorite and from a Tieschitz matrix augite grain. The bulk MnO contents of the extraterrestrial dust particles with high MnO olivines and pyroxenes are close to CI chondrite abundances. High MnO, low FeO olivines and orthopyroxenes were also found in the matrix of Semarkona, an unequilibrated ordinary chondrite. This may indicate a related origin for minerals in extraterrestrial dust particles and in the matrix of unequilibrated ordinary chondrites.

  17. Nature and origin of matrix in the unique type 3 chondrite, Kakangari

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.

    1989-01-01

    The characteristics of the matrix of the Kakangari type-3 chondrite were investigated using high-resolution TEM and AEM. It was found that the textural and mineralogical characteristics of the fine-grained matrix of Kakangari are different from those of the other chondrite groups. Unlike the matrix phases present in the CV3 and CO3 chondrites, the matrix mineralogy of Kakangari contains clear information regarding its possible origin and thermal history. Data obtained are most consistent with an origin of Kakangari by annealing, without melting at high temperature (possibly during a chondrule-forming thermal event), of clusters or aggregates of ultrafine-grained amorphous or crystalline phases. The precursor materials were most likely to have been a mixture of nebula and presolar dust. Chondrules in Kakangari were probably formed from identical precursors to the matrix, but reached temperatures sufficiently high to produce melting.

  18. 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.

  19. Cristobalite-pyroxene in an L6 chondrite - Implications for metamorphism

    NASA Technical Reports Server (NTRS)

    Olsen, E. J.; Mayeda, T. K.; Clayton, R. N.

    1981-01-01

    CRISPY is a cristobalite-pyroxene assemblage in the L6 chondrite ALHA 76003. It was formed by reaction of a very siliceous inclusion with the surrounding olivine-rich rock. Oxygen isotopes show that the inclusion was derived from a source with non-chondritic isotopic composition. The isotopes also show that the oxygen of the pyroxene reaction product was derived by simple mixing of oxygen from the inclusion and its immediately adjacent surroundings, with exchange with the bulk meteorite limited to a distance of about a millimeter. The persistence of cristobalite in close proximity to olivine, and the lack of isotopic equilibration, show that the metamorphic processes that form petrographic grade 6 chondrites involve transport of major elements over distances only on the order of millimeters.

  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. Rare earth elements in Ca-phosphates of Allende carbonaceous chondrite

    SciTech Connect

    Ebihara, M.; Honda, M.

    1987-09-01

    The Ca-phosphate phases in the Allende CV3 meteorite were selectively dissolved in ammoniacal EDTA solution and measured for abundances of the rare earth elements (REE) by radiochemical neutron activation and mass-spectrometric isotope dilution analyses. The REE abundances in CA-phosphates of Allende are remarkably different from those of ordinary chondrites. All the REE except Eu were observed to be enriched by factors of 50-100 relative to the Cl values. This is 3-4 times lower than concentrations of REE in the ordinary-chondrite phosphates. Allende phosphates have a small positive Eu anomaly, in contrast to the large negative Eu anomaly in phosphates from ordinary chondrites. Though the positive Eu anomaly in Allende Ca-phosphates is puzzling, the lack of a negative Eu anomaly in Allende Ca-phosphates suggests that they never have been in equilibrium with Allende coarse-grained Ca, Al-rich inclusions or their precursor materials. 42 references.

  2. Extraterrestrial Amino Acids in Orgueil and Ivuna: Tracing the Parent Body of CI Type Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Meyer, Michael (Technical Monitor); Ehrenfreund, Pascale; Glavin, Daniel P.; Bota, Oliver; Cooper, George; Bada, Jeffrey

    2001-01-01

    Amino acid analyses using HPLC of pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna have found that beta-alanine, glycine, and gamma-amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from approx. 600 to 2,000 parts per billion (ppb). Other alpha-amino acids such as alanine, alpha-ABA, alpha-aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (less than 200 ppb). Carbon isotopic measurements of beta-alanine and glycine and the presence of racemic (D/L 1) alanine and beta-ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the CIs is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites.

  3. Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of CI type carbonaceous chondrites

    PubMed Central

    Ehrenfreund, Pascale; Glavin, Daniel P.; Botta, Oliver; Cooper, George; Bada, Jeffrey L.

    2001-01-01

    Amino acid analyses using HPLC of pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna have found that β-alanine, glycine, and γ-amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from ≈600 to 2,000 parts per billion (ppb). Other α-amino acids such as alanine, α-ABA, α-aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (<200 ppb). Carbon isotopic measurements of β-alanine and glycine and the presence of racemic (D/L ≈ 1) alanine and β-ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the CIs is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites. PMID:11226205

  4. Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies

    NASA Technical Reports Server (NTRS)

    Duba, A.

    1986-01-01

    The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 magnitudes greater than rock forming minerals such as Olivine up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at grain boundaries. The environment in the wake of the space station can be exploited to produce conditions which will allow pyrolysis of carbonaceous chondrites. An experimental package consisting of a one square meter shield attached to a 15 cm diameter by 40 cm long furnace and tied to a conductance bridge, furnace controller, and digital voltmeter inside the space station via umbilical cable could make the required measurements. Since heating rates as low as 0.1 C/hour are required to study kinetics of the pyrolysis reations which are the cause of the high conductivity of the carbonaceous chondrites, experimental times up to 3 months will be needed.

  5. Chemical studies of L chondrites. V: compositional patterns for 49 trace elements in 14 L4-6 and 7 LL4-6 falls

    NASA Astrophysics Data System (ADS)

    Friedrich, Jon M.; Wang, Ming-Sheng; Lipschutz, Michael E.

    2003-07-01

    To study compositional trends associated with open-system thermal metamorphism and shock-induced collisional breakup of L4-6 chondrite parent(s), we used inductively coupled plasma mass spectrometry and radiochemical neutron activation analysis to determine 49 trace elements in 62 falls. Trends for the 49 elements, especially of the 14 rare earth elements in 5 members of a putative L/LL group (Bjurböle, Cynthiana, Holbrook, Knyahinya, Sultanpur) and 9 additional L chondrites (Aïr, Aumieres, Bachmut, Forksville, Kandahar, Kiel, Milean, Narellan, Santa Isabel) differed markedly from those in the remaining normal 46 samples. Here, we report the data for the 14 L and putative L/LL chondrites and 7 LL (Appley Bridge, Athens, Bandong, Ensisheim, Mangwendi, Olivenza, Soko-Banja), analyzed to test the affinity of the putative L/LL suite to well-characterized LL chondrites. Compositional trends of the 14 atypical L chondrites (including Aïr's unique and possibly contaminated signature) and Mangwendi, an LL6 chondrite, indicate that each is compositionally unrepresentative of well-sampled, whole-rock chondrites. Indeed, half of the unrepresentative chondrites were ≤ 2-g samples. Compositionally, members of the putative L/LL chondrites demonstrate no affinities to normal LL chondrite falls. To establish compositional trends accompanying open-system, thermal episodes involving the L chondrite parent(s), we should ignore data for the 14 unrepresentative L chondrites reported here.

  6. Gradistic vs. Cladistic Views in the Classification of Chondrites: The (L,H) Dichotomy and the Missing L/LL Precursors (NIPR Statistics VI.)

    NASA Astrophysics Data System (ADS)

    Lukács, B.; Holba, A.; Bérczi, Sz.

    1999-03-01

    Chondritic parent body evolutionary trends were projected -- on the basis of the NIPR Antarctic dataset (Yanai et al, 1995) -- in multicomponent functions (i.e. Fe-C-H2O race) of chondrite types for all groups. We looked for the possible precursors of L/LL chondrites.

  7. Thermally metamorphosed carbonaceous chondrites from data for thermally mobile trace elements

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Sheng; Lipschutz, Michael E.

    1998-11-01

    We report RNAA data for U, Co, Au, Sb, Ga, Rb, Cs, Se, Ag, Te, Zn, In, Bi, Tl and Cd (ordered by increasing ease of vaporization and loss from Murchison CM2 chondrite during open-system heating) in 9 Antarctic C2 and C3 chondrites. These meteorites exhibit properties (obtained by reflectance spectroscopy, oxygen isotope mass spectrometry and/or mineralogy-petrology) suggesting thermal metamorphism in their parent bodies. Five of these (Asuka 881655, Yamato (Y) 793495, Y-790992, PCA 91008 and Y-86789, paired with Y-86720) exhibit significant depletion of the most thermally-mobile 1-5 trace elements consistent with open-system loss during extended parent body heating under conditions duplicated by week-long heating of Murchison C2 chondrite heated at 500-700 deg C in a low pressure (initially 10-5 atm) H atmosphere. From earlier data, three other C3 chondrites - Allan Hills (ALH) 81003, ALH 85003 and Lewis Cliffs 85332 - show significant Cd depletion. Nine additional C2 and C3 chondrites show no evidence of mobile trace element depletion - including Y-793321, which by all other criteria was mildly metamorphosed thermally. Either metamorphism of these nine occurred under closed conditions and/or alteration took place under such mild conditions that even Cd could not be lost. The RNAA data suggest that 10 of the 46 Antarctic carbonaceous chondrites (including 4 of 37 from Victoria Land and 6 of 9 from Queen Maud Land) exhibit open-system loss of at least some thermally mobile trace elements by heating in their parent bodies while none of the 25 non-Antarctic falls experienced this. These results are consistent with the idea that the Antarctic sampling of near-Earth material differs from that being sampled today.

  8. Thermal Processing and Radial Mixing of Dust: Evidence from Comets and Primitive Chondrites

    NASA Astrophysics Data System (ADS)

    Wooden, D. H.; Harker, D. E.; Brearley, A. J.

    2005-12-01

    Cometary nuclei provide evidence for the mixing of high and low temperature materials in the solar nebula. Comets contain abundant amorphous carbon, amorphous Fe-bearing (Fe-Mg) silicates, organic materials (CHON), and volatile ices and gases that have never experienced temperatures above ˜1000 K, ˜1000 K, ˜300 K, and 50--150 K, respectively. Two Oort cloud comets, Hale-Bopp and C/2001 Q4 (NEAT), contain a high mass fraction (˜0.7) of Mg-rich silicate crystals. The absence of crystalline silicates in the interstellar medium infers that these cometary silicates are grains of interstellar materials that were processed at high temperature in the solar nebula. Crystals are either condensates (˜1450 K) or amorphous silicate grains annealed into crystals (>≃1000 K). We review the current scenarios for condensation and for annealing of amorphous silicates into crystals. Type 3.0 chondrite matrices contain Mg-rich crystalline silicates in varying proportions to amorphous Fe-Mg silicates with highly variable Fe/Mg ratios. It is possible that the Mg-rich crystals in chondrites come from the same inner solar system source as crystals in comets. Mg-rich amorphous silicates are absent from both chondrite matrices and cometary interplanetary dust particles. Given the lack of a reservoir of Mg-rich amorphous silicates to anneal into Mg-rich crystals, we conclude that the Mg-rich crystals in comets and chondrites probably formed as condensates. Condensation of Mg-rich crystals occurs in the hot, inner regions of the young (<≃ 1--3×105 yr) protoplanetary disk. Condensation of Mg-rich crystals may have also occured under highly reducing conditions in the chondrite-forming zone. Examining comets and primitive chondrites together supports the concept of a dynamic nebula where radial mixing of high and low temperature materials was prevalent.

  9. 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.

  10. Assessing the Formation of Ungrouped Achondrite Northwest Africa 8186: Residue, Crystallization Product, or Recrystallized Chondrite?

    NASA Technical Reports Server (NTRS)

    Srinivasan, P.; McCubbin, F. M.; Agee, C. B.

    2016-01-01

    The recent discoveries of primitive achondrites, metachondrites, and type 7 chondrites challenge the long held idea that all chondrites and achondrites form on separate parent bodies. These meteorites have experienced metamorphic temperatures above petrologic type 6 and have partially melted to various degrees. However, because of their isotopic and compositional similarities to both undifferentiated and differentiated groups, the provenance of these 'type 6+' meteorites remains largely unknown. CK and CV chondrites have recently been linked to a few achondrites due to their strong compositional, mineralogical, and isotopic similarities], suggesting a common origin between these meteorites. Although CVs have generally undergone low degrees of alteration near petrologic type 3, CKs have experienced a wide range of thermal alteration from petrologic type 3 to 6. Thermal evolution models on early accreting bodies predict that an early forming body can partially differentiate due to radiogenic heating, and, as a result, form radial layers of material increasing in thermal grade (types 3 to 6+) from the unmelted chondritic surface towards the differentiated core.Northwest Africa (NWA) 8186 is an ungrouped achondrite that provides compelling evidence for higher degrees of thermal processing and/or melting and differentiation on some CK/CV parent bodies. NWA 8186 plots on the CCAM line on a 3-oxygen isotope diagram directly with CK and CV chondrites and also plots with the CKs in regards to Cr isotopes. This meteorite is dominated by Nickel(II)Oxygen-rich olivine (less than 80%), lacks iron metal, and contains four oxide phases, indicating a high fOxygen (above FMQ) similar to the CKs. Additionally, NWA 8186 does not contain chondrules. We have further investigated the origins of NWA 8186 by examining and comparing the bulk composition of this CK-like achondrite with CK and CV chondrites, allowing us to assess the various scenarios in which NWA 8186 may have formed from

  11. 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].

  12. Almahata Sitta—Fragment MS-CH: Characterization of a new chondrite type

    NASA Astrophysics Data System (ADS)

    Horstmann, Marian; Bischoff, Addi; Pack, Andreas; Laubenstein, Matthias

    2010-10-01

    Among the several hundred, mostly small meteorite fragments, recovered within the Almahata Sitta strewn field, one fragment (MS-CH), weighing 5.68 g, was detected that represents a new type of chondritic meteorite. The detection of short-lived cosmogenic radionuclides clearly indicates that this chondrite fragment results from a fresh meteorite fall consistent with the Almahata Sitta event in October 2008. The fundamental mineralogical characteristics of the Almahata Sitta fragment MS-CH can be summarized as follows: (1) the almost equilibrated olivine has high Fa contents of about 36 mole%. The fragment is of petrologic type 3.8 ± 0.1; (2) the metal abundance of the rock is on the order of 2.5 vol%; (3) the mean chondrule size has been determined to be roughly 450 μm; (4) point-counting and imaging indicate that the matrix abundance is approximately 45 vol%; (5) Cr-spinels have much lower TiO2 concentrations than typical spinels within R chondrites; (6) calcium-aluminum-rich inclusions are spinel-rich and severely altered having abundant Na- and/or Cl-rich alteration products. Spinel also contains significant concentrations of Fe and Zn; (7) magnetites and platinum-group element-rich phases (sulfides, tellurides, and arsenides) characteristic of both R and CK chondrites were not found in fragment MS-CH; and (8) the mean oxygen isotope composition of three small fragments of Almahata Sitta MS-CH is δ17O = +4.35‰, δ18O = +4.94‰, and Δ17O = +1.76‰. The oxygen isotopes relate MS-CH to R chondrites. No established chondrite group having all these characteristics exists.

  13. 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.

  14. 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.

  15. Hydrothermal alteration experiments: tracking the path from interstellar to chondrites organics

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Organic molecules are detected in primitive carbonaceous chondrites. The origin of these organics, whether formed prior the accretion phase, or in-situ on the parent body, is still a matter of debate. We have investigated experimentally the chemical evolution of interstellar organic molecules submitted to hydrothermal conditions, mimicking asteroidal alteration (T<200°C). In particular, we want to assess the potential catalytic role of clays minerals in the polymerization/degradation of organics. Hexamethylenetetramine (HMT, compound of C-N bonds) is used as a plausible interstellar precursors from icy grains. Experimental products reveal a large diversity of molecules, including nitrogen organic molecules similar to those found in chondrites.

  16. 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.

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

    SciTech Connect

    Ruzicka, A. )

    1990-06-01

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

  18. New mineralogical and chemical data on the Machinga (L6) chondrite, Malawi

    NASA Technical Reports Server (NTRS)

    Koeberl, Christian; Reimold, Wolf Uwe; Horsch, Hanna E.; Merkle, Roland K. W.

    1990-01-01

    The Machinga, southern Malawi, Africa, L6 chondrite (observed fall, January 22, 1981) contains accessory phases of metal, troilite, chromite, and native Cu (which is associated with limonite and found in zones of aqueous alteration). Rare accessory phases are apatite and pentlandite, which are uncommon in L6 chondrites. Major mineral constituents (olivine, orthopyroxene, and plagioclase) indicate shock effects at a level of about 15-20 GPa shock pressure. The meteorite is thus classified to be of L6d type. Melt pockets of widely variable composition are abundant.

  19. The petrography, mineralogy and origins of calcium sulphate within the Cold Bokkeveld CM carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Lee, M. R.

    1993-03-01

    A detailed scanning and transmission electron microscopy study was carried out on the Cold Bokkeveld chondrite. Fracture-filling calcium sulphate, calcium sulphate within calcitized chondrules and within the matrix calcite was examined. Results indicate that calcium sulphate is widespread and the majority of its crystals are fibrous. The calcium sulphate is composed of a fine-scale structure of hemihydrate and anhydrate which may have been formed by dehydration of primary gypsum during sample preparation. The timing and origin of aqueous solutions and alteration of the chondrite are discussed and possible links with CI meteorites are considered.

  20. The petrogenesis of L-6 chondrites - Insights from the chemistry of minerals

    NASA Technical Reports Server (NTRS)

    Curtis, D. B.; Schmitt, R. A.

    1979-01-01

    Measurements of the major, minor and trace element abundances of the major minerals of the L-6 chondrites Alfianello, Colby (WI) and Leedey are used to investigate the formation mechanisms of L-6 chondrites. Electron microprobe analysis was performed on individual grains of each mineral, and separated minerals were analyzed by instrumental and radiochemical neutron activation analysis. The compositions of the three meteorites are observed to be generally uniform, however different abundances and distributions of rare earth elements and Co and Ni indicate that the meteorites have different petrogenetic histories. Alkali element distributions are found to be incompatible with internal equilibration of a closed system.

  1. The Oxygen Isotopic Composition of MIL 090001: A CR2 Chondrite with Abundant Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; McKeegan, K. D.; Sharp, Z. D.

    2012-01-01

    MIL 090001 is a large (>6 kg) carbonaceous chondrite that was classified as a member of the CV reduced subgroup (CVred) that was recovered during the 2009-2010 ANSMET field season [1]. Based on the abundance of refractory inclusions and the extent of aqueous alteration, Keller [2] suggested a CV2 classification. Here we report additional mineralogical and petrographic data for MIL 090001, its whole-rock oxygen isotopic composition and ion microprobe analyses of individual phases. The whole rock oxygen isotopic analyses show that MIL 090001 should be classified as a CR chondrite.

  2. Mn-Cr isotopic systematics of Chainpur chondrules and bulk ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Bansal, B.; Shih, C.-Y.; Mittlefehldt, D.; Martinez, R.; Wentworth, S.

    1994-01-01

    We report on ongoing study of the Mn-Cr systematics of individual Chainpur (LL3.4) chondrules and compare the results to those for bulk ordinary chondrites. Twenty-eight chondrules were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by INAA. Twelve were chosen for SEM/EDX and high-precision Cr-isotopic studies on the basis of LL-chondrite-normalized Mn(LL), Sc(LL), (Mn/Fe)(LL), and (Sc/Fe)(LL) as well as their Mn/Cr ratios. Classification into textural types follows from SEM/EDX examination of interior surfaces.

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

    NASA Technical Reports Server (NTRS)

    Ruzicka, Alex

    1990-01-01

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

  4. Mn-Cr Systematics in Sphalerites and Niningerites From Qingzhen and Yamato69001: Implications Regarding Their Formation Histories

    NASA Astrophysics Data System (ADS)

    El Goresy, A.; Wadhwa, M.; Zinner, E. K.; Nagel, H.-J.; Janicke, J.; Crozaz, G.

    1992-07-01

    Recent Cr isotopic measurements of sphalerites and alabandites in three EL3 chondrites MAC88136, MAC88180, and MAC88184 and of sphalerites in the EH4 chondrite Indarch (El Goresy et al., 1992) revealed ^53Cr excesses (^53Cr*), resulting from the in situ decay of ^53Mn (tau(sub)1/2=3.7 Ma), in most grains analysed. However, the initial ^53Mn/^55Mn ratios calculated for these grains were quite variable, and it was concluded that redistribution of ^53Cr* by diffusional processes was the most likely cause for these variations. In a continuation of the previous work (El Goresy et al., 1992), we report new mineral-chemical and Cr-isotopic data for two EH3 chondrites, Qingzhen and Yamato 69001. The distribution of Fe, Mg, and Mn in niningerites and sphalerites occurring in individual sulfide assemblages was determined by electron microprobe analysis. Among the meteorites of the EH3 subgroup, Qingzhen and Yamato 69001 are unique in that niningerites in both meteorites display normal as well as reversed zoning, indicating complex thermal histories (Ehlers and El Goresy, 1988; Lin et al., 1989; Lin, 1991; Nagel, 1991). Niningerites have different MnS contents (9.2-32.6 mol% MnS in Qingzhen vs. 4.2- 6.3 mol% MnS in Yamato 69001), as do the sphalerites (4.0-9.2 mol% MnS in Qingzhen vs. 2.0-3.5 mol% in Yamato 69001). Sphalerites in both meteorites are normally zoned, with 46.0-49.8 mol% FeS in sphalerites from Qingzhen, and 42.3-49.7 mol% FeS in sphalerites from Yamato 69001. The spatial distributions of Fe and Mg in niningerites and of Fe and Mn in sphalerites indicate complex processes that may have occurred before accretion and/or during later metamorphic events in the parent body (El Goresy and Ehlers, 1989; Lin, 1991; Nagel, 1991). Ion microprobe measurements of 6 sphalerites and 3 niningerites in Qingzhen and of 3 sphalerites and 2 niningerites in Yamato 69001 showed that ^55Mn/^52Cr ratios in these sulfide phases are significantly lower than in sphalerites and

  5. The Effects of Thermal Metamorphism on the Amino Acid Content of the CI-Like Chondrite Y-86029

    NASA Technical Reports Server (NTRS)

    Burton, A. S.; Grunsfeld, S.; Glavin, D. P.; Dworkin, J. P.

    2014-01-01

    Carbonaceous chondrites con-tain a diverse suite of amino acids that varies in abundance and structural diversity depending on the degree of aqueous alteration and thermal histo-ry that the parent body experienced [1 - 3]. We recently determined the amino acid contents of several fragments of the Sutter's Mill CM2 chon-drite [4]. In contrast with most other CM2 chon-drites, the Sutter's Mill meteorites showed minimal evidence for the presence of indigenous amino acids. A notable difference between the Sutter's Mill meteorites and other CM2 chondrites are that the Sutter's Mill stones were heated to tempera-tures of 150 - 400 C [4], whereas most other CM2 chondrites do not show evidence for thermal met-amorphism [5]. Because empirical studies have shown that amino acids rapidly degrade in aqueous solutions above 150 C and the presence of miner-als accelerates this degradation [6], a plausible explanation for the lack of amino acids observed in the Sutter's Mill meteorites is that they were destroyed during metamorphic alteration. Fewer CI chondrites have been analyzed for amino acids because only a small number of these meteorites have been recovered. Nevertheless, indigenous amino acids have been reported in the CI chondrites Ivuna and Orgueil [7]. Here we report on the amino acid analysis of the CI-like chondrite, Yamato 86029 (Y-86029; sample size of 110 mg). Just as the Sutter's Mill meteorites were thermally metamporphosed CM2 chondrites, Y-86029 has experienced thermal metamorphism at higher temperatures than Orgueil and Ivuna (normal CI chondrites) experienced, possibly up to 600 C [8].

  6. 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.

  7. Exposure history and terrestrial ages of ordinary chondrites from the Dar al Gani region, Libya

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

    We measured the concentrations of noble gases in 32 ordinary chondrites from the Dar al Gani (DaG) region, Libya, as well as concentrations of the cosmogenic radionuclides 14C, 10Be, 26Al, 36Cl, and 41Ca in 18 of these samples. Although the trapped noble gases in five DaG samples show ratios typical of solar or planetary gases, in all other DaG samples, they are dominated by atmospheric contamination, which increases with the degree of weathering. Cosmic ray exposure (CRE) ages of DaG chondrites range from ~1 Myr to 53 Myr. The CRE age distribution of 10 DaG L chondrites shows a cluster around 40 Myr due to four members of a large L6 chondrite shower. The CRE age distribution of 19 DaG H chondrites shows only three ages coinciding with the main H chondrite peak at ~7 Myr, while seven ages are <5 Myr. Two of these H chondrites with short CRE ages (DaG 904 and 908) show evidence of a complex exposure history. Five of the H chondrites show evidence of high shielding conditions, including low 22Ne/21Ne ratios and large contributions of neutron-capture 36Cl and 41Ca. These samples represent fragments of two or more large pre-atmospheric objects, which supports the hypothesis that the high H/L chondrite ratio at DaG is due to one or more large unrecognized showers. The 14C concentrations correspond to terrestrial ages <35 kyr, similar to terrestrial ages of chondrites from other regions in the Sahara but younger than two DaG achondrites. Despite the loss of cosmogenic 36Cl and 41Ca during oxidation of metal and troilite, concentrations of 36Cl and 41Ca in the silicates are also consistent with 14C ages <35 kyr. The only exception is DaG 343 (H4), which has a 41Ca terrestrial age of 150 ± 40 kyr. This old age shows that not only iron meteorites and achondrites but also chondrites can survive the hot desert environment for more than 50 kyr. A possible explanation is that older meteorites were covered by soils during wetter periods and were recently exhumed by removal of

  8. Three Unusual Chondrules in the Bovedy (L3) Chondrite

    NASA Astrophysics Data System (ADS)

    Hill, H. G. M.

    1993-07-01

    The Bovedy (L3) chondrite [1] has recently been studied petrographically using SEM and EMPA as part of a general review of the Irish meteorites. The following chondrules are notable: Chondrule 1. A covered thin-section of the Bovedy (Sprucefield) meteorite contains a very highly-strained, ellipsoidal, radiating pyroxene chondrule with a semi-major axis of 2mm. The elongation ratio, 2.6 x, is higher than values published elsewhere [2]. Chondrule 2. A slab of Bovedy (~48 cm^2) contains an exceptionally large, ellipsoidal, porphyritic olivine chondrule (semi-major axis = 1.4 cm, minor axis = 0.8 cm). This is among the largest droplet chondrule on record [2]. The chondrule is texturally identical to other PO chondrules in the meteorite. Chondrule 3. A polished thin-section, prepared from the above slab, contains an ellipsoidal-to-irregular shaped glassy chondrule (Fig. 1). SEM and EMPA confirm a composition of pyroxenitic glass (brown) with globular and elongate inclusions of silica glass (colorless). Representative EMPA of the brown glass (in wt%) is: SiO2 57.49, Al2O3 0.93, Cr2O3 0.38, FeO 14.22, MnO 0.63, MgO 23.32, CaO 2.69, Na2O 1.03 (no other elements detected). This can be recast as a pyroxene with formula Ca(sub)0.10 Na(sub)0.07 Fe(sub)0.43Mg(sub)1.26Al(sub)0.04 Cr(sub)0.01Mn(sub)0.02Si(sub)2.08O(sub)6. The composition corresponds closely with that reported by [3] for a silica pyroxenite clast from the same meteorite. It suggests that the chondrule was derived by rapid melting of the material represented by the clast, which has been interpreted as an igneous fractionate formed in a planetary environment. References: [1] Graham A. L. et al. (1976) GCA, 40, 529-535. [2] Grossman J. N. et al. (1988) In Meteorites and the Early Solar System (J. F. Kerridge and M. S. Matthews, eds.), 619-659, Univ. Arizona. [3] Ruzicka A. and Boynton W. V. (1992) Meteoritics, 27, 283. Fig. 1, which appears here in the hard copy, shows a photograph of chondrule 3 photographed in

  9. Petrologic Locations of Nanodiamonds in Carbonaceous Chondrite Meteorites

    NASA Astrophysics Data System (ADS)

    Garvie, Laurence

    Nanodiamonds (NDs), with dimensions near two nanometers, are widespread accessory minerals in primitive meteorites. They have been studied extensively in concentrates made from acid-insoluble residues, but surprisingly little is known about their petrologic settings in the meteorites because they have not been studied in situ. Information about such settings is fundamental for determining how they formed and were incorporated into the meteorites. The primary goal of the planned research is to determine and compare the petrologic settings of NDs within matrix of different types of carbonaceous chondrites, with the long-term aim of providing new insights regarding the origin of NDs. This research will also provide new data on the structure and major and trace element compositions of individual NDs and regions within them. Transmission electron microscopes (TEMs) provide uniquely powerful information regarding chemical, bonding, and structural data on the scale needed to solve this problem, assuming the NDs can be located within the host matrix. We have developed methods of observing NDs in situ within the fine-grained matrix of primitive meteorites and will use various TEMs to accomplish that goal for several meteorites. High- resolution imaging and electron energy-loss spectroscopy (EELS) will permit determination of both structural and chemical information about the NDs and their adjacent minerals. By the middle of the proposed grant period, two state-of-the-art, aberration-corrected TEMs will have been installed at ASU and will be used to locate heavy elements such as Xe, Te, and Pd within the NDs. These TEMs permit the imaging of individual atoms of heavy elements with annular dark-field (ADF) imaging, and these atoms can be identified using EELS. The result of these new types of measurements will provide information about whether such elements, which have been used to determine whether NDs formed in supernovae, occur within the interiors or on the surfaces of

  10. Testing the origin of the magnetic record of chondrites

    NASA Astrophysics Data System (ADS)

    Kohout, T.; Kletetschka, G.; Pesonen, L. J.; Wasilewski, P. J.

    2006-05-01

    The method for determination of the meteorite magnetic record origin has been developed by Kletetschka et al, 2005. The technique utilizes a detailed AF (Alternating Field) demagnetization of NRM (Natural Remanent Magnetization), followed by AF demagnetization of the SIRM (Saturation Isothermal Remanent Magnetization) in the very same AF steps. The ratio of NRM(AF)/SIRM(AF) is plotted against AF demagnetization field. The slope of the NRM(AF)/SIRM(AF) curve contains information about the nature of NRM acquisition process. In the case of the TRM (ThermoRemanent Magnetization) or CRM (ChemoRemanent Magnetization) the coercivity spectrum of NRM should cover equally both the SD and MD particles resulting in the constant NRM(AF)/SIRM(AF) ratio. In the case of the IRM (Isothermal Remanent Magnetization) the low coercivity grains are much more susceptible to the magnetizing field that the high coercivity grains resulting in the increase of the NRM(AF)/SIRM(AF) ratio in the low coercivity (low AF field) region. We applied this method on three chondritic meteorites. The Neuschwanstein (EL6) reveals significant IRM component due to negative NRM(AF)/SIRM(AF) slope in the low AF fields. The chondrules of Bjurbole (L4) reveals constant NRM(AF)/SIRM(AF) ratio pointing on TRM (or CRM) origin of the NRM. The interesting feature was observed on chondrules from the Avanhandava (H4) meteorite. Systematically lower values of the NRM(AF)/SIRM(AF) ratio in the low AF range points to partial demagnetization of MD grains what can be explained as an effect of the impact demagnetization of the parent body or as an effect of the time-decay of the magnetization. The method can serve as fast tool to determine the nature and origin of the magnetic record of the extraterrestrial and terrestrial materials and has potential application in the paleointensity studies. Kletetschka G., Kohout T., Wasilewski P. J., Fuller M. (2005): Recognition of thermal remanent magnetization in rocks and meteorites

  11. 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.

  12. 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.

  13. Chemical studies of H chondrites. 6: Antarctic/non-Antarctic compositional differences revisited

    NASA Astrophysics Data System (ADS)

    Wolf, Stephen F.; Lipschutz, Michael E.

    1995-02-01

    We report data for the trace elements Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, T1, and In (ordered by putative volatility during nebular condensation and accretion) determined by radiochemical neutron activation analysis of 14 additional H5 and H6 chondrite falls. Data for the 10 most volatile elements (Rb to In) treated by the multivariate techniques of linear discriminant analysis and logistic regression in these and 44 other falls are compared with those of 59 H4-6 chondrites from Antarctica. Various populations are tested by the multivariate techniques, using the previously developed method of randomization-simulation to assess significance levels. An earlier conclusion, based on fewer examples, that H4-6 chondrite falls are compositionally distinguishable from the Antarctic suite is verified by the additional data. This distinctiveness is highly significant because of the presence of samples from Victoria Land in the Antarctic population, which differ compositionally from falls beyond any reasonable doubt. However, it cannot be proven unequivocally that falls and Antarctic samples from Queen Maud Land are compositionally distinguishable. Trivial causes (e.g., analyst bias, weathering) cannot explain the Victoria Land (Antarctic)/non-Antarctic compositional difference for paradigmatic H4-6 chondrites. This seems to reflect a time-dependent variation of near-Earth meteoroid source regions differing in average thermal history.

  14. Primitive Liquid Water of the Solar System in an Aqueous Altered Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Tsuchiyama, A.; Miyake, A.; Kitayama, A.; Matsuno, J.; Takeuchi, A.; Uesugi, K.; Suzuki, Y.; Nakano, T.; Zolensky, M. E.

    2016-01-01

    Non-destructive 3D observations of the aqueous altered CM chondrite Sutter's Mill using scanning imaging x-ray microscopy (SIXM) showed that some of calcite and enstatite grains contain two-phase inclusion, which is most probably composed of liquid water and bubbles. This water should be primitive water responsible for aqueous alteration in an asteroid in the early solar system.

  15. Building Chondrites: SPH Simulations of a Jet Flow in a 3D Protoplanetary Disc

    NASA Astrophysics Data System (ADS)

    Pignatale, F. C.; Gonzalez, J.-F.; Cuello, N.; Bourdon, B.; Fitoussi, C.

    2016-08-01

    We present SPH simulations of jet flows in 3D discs to investigate the transport of refractory material toward the outer cold disc regions. Dust grains are captured by the disc at distances up to 40 AU, with dust aggregates mimicking chondrites.

  16. Are H/L Chondrites Associated with the Disruption of Comet C/1919 Q2 Metcalf?

    NASA Astrophysics Data System (ADS)

    Trigo-Rodriguez, J. M.; Williams, I. P.

    2016-08-01

    We present evidence from historic meteorite falls (e.g. Cali and Tieschitz) about the existence of a high-inclination meteoroid stream originated by the disruption of comet C/1919 Q2 Metcalf that is the main source of the H/L chondrite interloper.

  17. A Raman Study of Carbonates and Organic Contents in Five CM Chondrites

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.; Bodnar, R. J.; Farley, C.; Cheung, J. C. H.

    2016-01-01

    Carbonates comprise the second most abundant class of carbon-bearing phases in carbonaceous chondrites after organic matter (approximately 2 wt.%), followed by other C-bearing phases such as diamond, silicon carbide, and graphite. Therefore, understanding the abundances of carbonates and the associated organic matter provide critical insight into the genesis of major carbonaceous components in chondritic materials. Carbonates in CM chondrites mostly occur as calcite (of varying composition) and dolomite. Properly performed, Raman spectroscopy provides a non-destructive technique for characterizing meteorite mineralogy and organic chemistry. It is sensitive to many carbonaceous phases, allows the differentiation of organic from inorganic materials, and the interpretation of their spatial distribution. Here, with the use of Raman spectroscopy, we determine the structure of the insoluble organic matter (IOM) in the matrix and carbonate phases in five CM chondrites: Jbilet Winselwan, Murchison, Nogoya, Santa Cruz, and Wisconsin Range (WIS) 91600, and interpret the relative timing of carbonate precipitation and the extent of the associated alteration events.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1990-06-01

    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.

  20. 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.; Bădescu, 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 μm and 2 μm 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

  1. Determination of 11 major and minor elements in chondritic meteorites by inductively coupled plasma mass spectrometry.

    PubMed

    Wolf, Stephen F; Compton, Joseph R; Gagnon, Christopher J L

    2012-10-15

    We have developed a new method for the quantification of 11 major and minor elements (Na, Mg, Al, P, S, K, Ca, Cr, Mn, Fe, and Ni) in chondritic meteorites by ICPMS using external calibration with a matrix-matched standard prepared from the Allende Standard Reference Meteorite. We have demonstrated the method's accuracy and assessed three different measures of precision by performing replicate dissolutions and analyses of 0.10-g samples of a homogenized samples of the CM2 meteorite Murchison and compared our results to literature values. We subsequently applied this method to the analysis of a set of four chondritic meteorites possessing a relatively wide range of chondritic compositions with results in accord with previously published values. Because our method is designed to use the same instrumentation and can use samples and standards prepared according to methods previously validated for the determination of a comprehensive suite of minor, trace, moderately and highly volatile trace elements (i.e., Li, Sc, Ti, V, Mn, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Ru, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, Ba, all 14 naturally occurring lanthanoids, Hf, W, Re, Ir, Pt, Tl, Bi, Th, and U) it complements these methods and allows a single laboratory to determine the concentrations of 60 elements in semimicroscopic amounts of chondritic material.

  2. Volatiles in fourteen interplanetary dust particles: A comparison with CI and CM chondrites

    NASA Technical Reports Server (NTRS)

    Bustin, R.; Gibson, E. K., Jr.; Wentworth, S. J.

    1993-01-01

    In an attempt to classify the nature of volatiles within interplanetary dust particles (IDP's), 14 IDP's using a laser microprobe/mass spectrometer (LM/MS) technique were studied. Volatile abundances and distributions found for the IDP's are compared with those measured for carbonaceous chondrites in order to determine if the IDP's are related to the parent bodies of these primitive meteorites.

  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 ~10 GPa, which did not destroy its unusually high porosity of ~27 vol%. Metallographic textures in LAP 031047 indicate heating above ~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 ~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 ~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. EXPLORING THE POTENTIAL FORMATION OF ORGANIC SOLIDS IN CHONDRITES AND COMETS THROUGH POLYMERIZATION OF INTERSTELLAR FORMALDEHYDE

    SciTech Connect

    Kebukawa, Yoko; Cody, George D.; David Kilcoyne, A. L. E-mail: yoko@ep.sci.hokudai.ac.jp

    2013-07-01

    Polymerization of interstellar formaldehyde, first through the formose reaction and then through subsequent condensation reactions, provides a plausible explanation for how abundant and highly chemically complex organic solids may have come to exist in primitive solar system objects. In order to gain better insight on the reaction, a systematic study of the relationship of synthesis temperature with resultant molecular structure was performed. In addition, the effect of the presence of ammonia on the reaction rate and molecular structure of the product was studied. The synthesized formaldehyde polymer is directly compared to chondritic insoluble organic matter (IOM) isolated from primitive meteorites using solid-state {sup 13}C nuclear magnetic resonance, Fourier transform infrared, and X-ray absorption near edge structure spectroscopy. The molecular structure of the formaldehyde polymer is shown to exhibit considerable similarity at the functional group level with primitive chondritic IOM. The addition of ammonia to the solution enhances the rate of polymerization reaction at lower temperatures and results in substantial incorporation of nitrogen into the polymer. Morphologically, the formaldehyde polymer exists as submicron to micron-sized spheroidal particles and spheroidal particle aggregates that bare considerable similarity to the organic nanoglobules commonly observed in chondritic IOM. These spectroscopic and morphological data support the hypothesis that IOM in chondrites and refractory organic carbon in comets may have formed through the polymerization of interstellar formaldehyde after planetesimal accretion, in the presence of liquid water, early in the history of the solar system.

  5. Comment on Mars as the Parent Body of the CI Carbonaceous Chondrites by J. E. Brandenburg

    NASA Technical Reports Server (NTRS)

    Treiman, Allan H.

    1996-01-01

    Geological and chemical data refute a martian origin for the CI carbonaceous chondrites. Here, I will first consider Brandenburg's [1996] proposal that the CI's formed as water-deposited sediments on Mars, and that these sediments had limited chemical interactions with their martian environment. Finally, I will address oxygen isotope ratios, the strongest link between the CIs and the martian meteorites.

  6. Investigation of pyridine carboxylic acids in CM2 carbonaceous chondrites: Potential precursor molecules for ancient coenzymes

    NASA Astrophysics Data System (ADS)

    Smith, Karen E.; Callahan, Michael P.; Gerakines, Perry A.; Dworkin, Jason P.; House, Christopher H.

    2014-07-01

    The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We also report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

  7. Inconclusive Evidence for Non-Terrestrial Isoleucine Enantiomeric Excesses in CR Chondrites

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie E.; Glavin, Daniel P.; Dworkin, Jason P.; Martins, Zita; Bada, Jeffrey L.

    2012-01-01

    Researchers recently described the soluble organic content of eight Antarctic CR carbonaceous chondrites and reported large enantiomeric excesses (ee) of L-isoleucine and Dalloisoleucine. The reported ee values decrease with inferred increases in aqueous alteration. We believe the conclusions presented in the manuscript are not fully justified and the data are potentially flawed.

  8. Simulation of possible regolith optical alteration effects on carbonaceous chondrite meteorites

    NASA Astrophysics Data System (ADS)

    Clark, Beth E.; Fanale, Fraser P.; Robinson, Mark S.

    1993-03-01

    As the spectral reflectance search continues for links between meteorites and their parent body asteroids, the effects of optical surface alteration processes need to be considered. We present the results of an experimental simulation of the melting and recrystallization that occurs to a carbonaceous chondrite meteorite regolith powder upon heating. As done for the ordinary chondrite meteorites, we show the effects of possible parent-body regolith alteration processes on reflectance spectra of carbonaceous chondrites (CC's). For this study, six CC's of different mineralogical classes were obtained from the Antarctic Meteorite Collection: two CM meteorites, two CO meteorites, one CK, and one CV. Each sample was ground with a ceramic mortar and pestle to powders with maximum grain sizes of 180 and 90 microns. The reflectance spectra of these powders were measured at RELAB (Brown University) from 0.3 to 2.5 microns. Following comminution, the 90 micron grain size was melted in a nitrogen controlled-atmosphere fusion furnace at an approximate temperature of 1700 C. The fused sample was immediately held above a flow of nitrogen at 0 C for quenching. Following melting and recrystallization, the samples were reground to powders, and the reflectance spectra were remeasured. The effects on spectral reflectance for a sample of the CM carbonaceous chondrite called Murchison are shown.

  9. Petrology and Geochemistry of LEW 88663 and PAT 91501: High Petrologic L Chondrites

    NASA Astrophysics Data System (ADS)

    Mittlefehldt, D. W.; Lindstrom, M. M.; Field, S. W.

    1993-07-01

    Primitive achondrites (e.g., Acapulco, Lodran) are believed to be highly metamorphosed chondritic materials, perhaps up to the point of anatexis in some types. Low petrologic grade equivalents of these achondrites are unknown, so the petrologic transition from chondritic to achondritic material cannot be documented. However, there are rare L chondrites of petrologic grade 7 that may have experienced igneous processes, and study of these may yield information relevant to the formation of primitive achondrites, and perhaps basaltic achondrites, from chondritic precursors. We have begun the study of the L7 chondrites LEW 88663 and PAT 91501 as part of our broader study of primitive achondrites. Here, we present our preliminary petrologic and geochemical data on these meteorites. Petrology and Mineral Compositions: LEW 88663 is a granular achondrite composed of equant, subhedral to anhedral olivine grains poikilitically enclosed in networks of orthopyroxene and plagioclase. Small grains of clinopyroxene are spatially associated with orthopyroxene. Troilite occurs as large anhedral and small rounded grains. The smaller troilite grains are associated with the orthopyroxene-plagioclase networks. PAT 91501 is a vesicular stone containing centimeter-sized troilite +/- metal nodules. Its texture consists of anhedral to euhedral olivine grains, anhedral orthopyroxene grains (some with euhedral clinopyroxene overgrowths), anhedral to euhedral clinopyroxene, and interstitial plagioclase and SiO2-Al2O3-K2O- rich glass. In some areas, olivine is poikilitically enclosed in orthopyroxene. Fine-grained troilite, metal, and euhedral chromite occur interstitial to the silicates. Average mineral compositions for LEW 88663 are olivine Fo(sub)75.8, orthopyroxene Wo(sub)3.4En(sub)76.2Fs(sub)20.4, clinopyroxene Wo(sub)42.6En(sub)47.8Fs(sub)9.6, plagioclase Ab(sub)75.0An(sub)21.6Or(sub)3.4. Mineral compositions for PAT 91501 are olivine Fo(sub)73.8, orthopyroxene Wo(sub)4.5En(sub)74.8Fs

  10. Amino acid analyses of type 3 chondrites Colony, Ornans, Chainpur, and Bishunpur

    NASA Astrophysics Data System (ADS)

    Chan, H.-S.; Martins, Zita; Sephton, Mark A.

    2012-09-01

    The CO3s Colony and Ornans and LL3s Chainpur and Bishunpur were analyzed for the first time for amino acids using gas chromatography-mass spectrometry (GC-MS). Type 3 chondrites have relatively unaltered metamorphic and petrological histories. Chainpur was the most amino acid rich of the four type 3 chondrites with a total amino acid abundance of 3330 parts per billion (ppb). The other type 3 chondrites had total amino acid abundances that ranged from 660 to 1110 ppb. A D/L ratio of <0.7 for all proteic amino acids suggests at least some amino acid terrestrial contamination. However, a small fraction of indigenous extraterrestrial amino acids cannot be excluded because of the presence of the nonprotein amino acid α-aminoisobutyric acid (α-AIB), and unusually high relative abundances (to glycine) of β-alanine and γ-ABA. The comparisons between the free and total amino acid contents of the samples also indicate a low free/total amino acid ratio (ranging from about 1:4 in CO chondrites to about 1:50 in Chainpur), which indicate that amino acids are present mainly in the bound form and were made detectable after acid hydrolysis.

  11. U-Pb Dating of the Shock Melt Veins in Two L6 Chondrites

    NASA Astrophysics Data System (ADS)

    Li, S.; Hsu, W.

    2016-08-01

    We present in situ U-Pb dating of apatite and their decomposed product tuite in two L6 chondrites. The Pb loss experienced by phosphate correlated with shock-induced change. They have recorded two major impact events on their parent body.

  12. Petrological Investigations of CAIs from Efremovka and NWA 3118 CV3 Chondrites

    NASA Astrophysics Data System (ADS)

    Ivanova, M. A.; Lorenz, C. A.; Korochantseva, E. V.; MacPherson, G. J.

    2010-03-01

    Several new big CAIs were extracted from the Efremovka and NWA 3118 CV3 chondrites to analyze petrology, chemistry and isotopic compositions. Here we report preliminary results on mineralogy, petrology and bulk chemistry of two CAIs, of Type B1 and of Type A.

  13. Simulation of possible regolith optical alteration effects on carbonaceous chondrite meteorites

    NASA Technical Reports Server (NTRS)

    Clark, Beth E.; Fanale, Fraser P.; Robinson, Mark S.

    1993-01-01

    As the spectral reflectance search continues for links between meteorites and their parent body asteroids, the effects of optical surface alteration processes need to be considered. We present the results of an experimental simulation of the melting and recrystallization that occurs to a carbonaceous chondrite meteorite regolith powder upon heating. As done for the ordinary chondrite meteorites, we show the effects of possible parent-body regolith alteration processes on reflectance spectra of carbonaceous chondrites (CC's). For this study, six CC's of different mineralogical classes were obtained from the Antarctic Meteorite Collection: two CM meteorites, two CO meteorites, one CK, and one CV. Each sample was ground with a ceramic mortar and pestle to powders with maximum grain sizes of 180 and 90 microns. The reflectance spectra of these powders were measured at RELAB (Brown University) from 0.3 to 2.5 microns. Following comminution, the 90 micron grain size was melted in a nitrogen controlled-atmosphere fusion furnace at an approximate temperature of 1700 C. The fused sample was immediately held above a flow of nitrogen at 0 C for quenching. Following melting and recrystallization, the samples were reground to powders, and the reflectance spectra were remeasured. The effects on spectral reflectance for a sample of the CM carbonaceous chondrite called Murchison are shown.

  14. Copper Sulfides in the R Chondrites: Evidence of Hydrothermal Alteration in Low Petrologic Types

    NASA Astrophysics Data System (ADS)

    Miller, K. E.; Lauretta, D. S.; Berger, E. L.; Thompson, M. S.; Zega, T. J.

    2016-08-01

    Bornite in the R chondrites formed via pre-accretionary processes. Hydrothermal alteration on the parent body between ~200° and 300°C resulted in replacement by chalcopyrite and isocubanite. These phases are found in a range of petrologic types.

  15. Search for effects of a supernova explosion 30 to 40 thousand years ago in chondrites

    NASA Technical Reports Server (NTRS)

    Alexeev, V. A.; Ustinova, G. K.

    1993-01-01

    The relative increases in Al-26 and Mn-53 equilibrium radioactivity of chondrites with different cosmic-ray exposure and terrestrial ages due to a possible supernova explosion 30-40 thousand years ago have been calculated. The results are discussed.

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

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.

    1990-01-01

    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).

  17. Hf-W Chronology of Chondrules and Metal from CR Chondrites

    NASA Astrophysics Data System (ADS)

    Budde, G.; Kleine, T.

    2016-08-01

    Hf-W systematics of CR chondrites indicate that they formed ~3 Ma after CAI formation. Metal and silicate fractions show different nucleosynthetic W isotope anomalies, implying that the silicates have a deficit in s-process W relative to the metal.

  18. Determination of 11 major and minor elements in chondritic meteorites by inductively coupled plasma mass spectrometry.

    PubMed

    Wolf, Stephen F; Compton, Joseph R; Gagnon, Christopher J L

    2012-10-15

    We have developed a new method for the quantification of 11 major and minor elements (Na, Mg, Al, P, S, K, Ca, Cr, Mn, Fe, and Ni) in chondritic meteorites by ICPMS using external calibration with a matrix-matched standard prepared from the Allende Standard Reference Meteorite. We have demonstrated the method's accuracy and assessed three different measures of precision by performing replicate dissolutions and analyses of 0.10-g samples of a homogenized samples of the CM2 meteorite Murchison and compared our results to literature values. We subsequently applied this method to the analysis of a set of four chondritic meteorites possessing a relatively wide range of chondritic compositions with results in accord with previously published values. Because our method is designed to use the same instrumentation and can use samples and standards prepared according to methods previously validated for the determination of a comprehensive suite of minor, trace, moderately and highly volatile trace elements (i.e., Li, Sc, Ti, V, Mn, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Ru, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, Ba, all 14 naturally occurring lanthanoids, Hf, W, Re, Ir, Pt, Tl, Bi, Th, and U) it complements these methods and allows a single laboratory to determine the concentrations of 60 elements in semimicroscopic amounts of chondritic material. PMID:23141337

  19. Investigation of Pyridine Carboxylic Acids in CM2 Carbonaceous Chondrites: Potential Precursor Molecules for Ancient Coenzymes

    NASA Technical Reports Server (NTRS)

    Smith, Karen E.; Callahan, Michael P.; Gerakines, Perry A.; Dworkin, Jason P.; House, Christopher H.

    2014-01-01

    The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We lso report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

  20. Investigation of Pyridine Carboxylic Acids in CM2 Carbonaceous Chondrites: Potential Precursor Molecules for Ancient Coenzymes

    NASA Technical Reports Server (NTRS)

    Smith, Karen E.; Callahan, Michael P.; Gerakines, Perry A.; Dworkin, Jason P.; House, Christopher H.

    2014-01-01

    The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We also report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.