WorldWideScience

Sample records for chondrites

  1. Halogens in CM Chondrites

    Science.gov (United States)

    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.

  2. Fluid Inclusions in Carbonaceous Chondrites

    Science.gov (United States)

    Saylor, J.; Zolensky, M. E.; Bodnar, R. J.; Le L.; Schwandt, C.

    2001-01-01

    Fluid inclusions are present in carbonaceous chondrites. Of the chondrites studied (CI1, CM1 and 2, CV3) fluid inclusions were found only in CM2s and CI1s, and by extrapolation are most likely to be found there in the future. Additional information is contained in the original extended abstract.

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

    Science.gov (United States)

    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. CV and CM chondrite impact melts

    Science.gov (United States)

    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.

  5. Electrical conductivity of chondritic meteorites

    Science.gov (United States)

    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.

  6. Petrology and mineralogy of CK chondrites: Implications for the metamorphism of the CK chondrite parent body

    OpenAIRE

    Takaaki, Noguchi

    1993-01-01

    The petrology and mineralogy of four CK chondrites, Karoonda (CK4), Maralinga (CK4), Yamato(Y)-693(CK4), and Elephant Moraine (EET) 87507 (CK5) were investigated in detail to estimate the origin of their quite heterogeneous plagioclases and the metamorphic history of CK chondrite parent body. EPMA analyses and SEM observations revealed that plagioclases in chondrules, CAIs, and matrices in CK chondrites have different compositional variations and that plagioclases in matrices display distinct...

  7. Carbonaceous Chondrite Clasts in HED Achondrites

    Science.gov (United States)

    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).

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

    Science.gov (United States)

    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 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 transfers), and the 0.9-1.2 μm region (due to Fe 2+ crystal field transitions), and generally dominate over mafic silicates. CM petrologic subtypes exhibit a positive correlation between degree of aqueous alteration and depth of the 0.7 μm absorption band. This is consistent with the decrease in fine-grained opaques that accompanies aqueous alteration. There is no consistent relationship between degree of aqueous alteration and evidence for a 0.65 μm region saponite-group phyllosilicate absorption band. Spectra of different subsamples of a single CM can show large variations in absolute reflectance and overall slope. This is probably due to petrologic variations that likely exist within a single CM chondrite, as duplicate spectra for a single subsample show much less spectral variability

  9. Noble gases in E-chondrites

    Science.gov (United States)

    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.

  10. Petrology of Amoeboid Olivine Aggregates in Antarctic CR Chondrites: Comparison With Other Carbonaceous Chondrites

    Science.gov (United States)

    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.

  11. The classification and complex thermal history of the enstatite chondrites

    Science.gov (United States)

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

    1995-01-01

    We have carried out instrumental neutron activation analysis of 11 enstatite chondrites and electron microprobe analyses of 17 enstatite chondrites, most of which were previously little described. We report here the third known EH5 chondrite (LEW 88180) and an unusual EL6 chondrite (LEW 87119), new data on four EL3 chondrites (ALH 85119, EET 90299, PCA 91020, and MAC 88136, which is paired with MAC 88180 and MAC 88184), the second EL5 chondrite (TIL 91714), and an unusual metal-rich and sulfide-poor EL3 chondrite (LEW 87223). The often discussed differences in mineral composition displayed by the EH and EL chondrites are not as marked after the inclusion of the new samples in the database, and the two classes apparently experienced a similar range of equilibrium temperatures. However, texturally the EL chondrites appear to have experienced much higher levels of metamorphic alteration than EH chondrites of similar equilibration temperatures. Most of the petrologic type criteria are not applicable to enstatite chondrites and, unlike the ordinary chondrites, texture and mineralogy reflect different aspects of the meteorite history. We therefore propose that the existing petrologic type scheme not be used for enstatite chondrites. We suggest that while 'textural type' reflects peak metamorphic temperatures, the 'mineralogical type' reflects equilibration during postmetamorphic (probably regolith) processes. Unlike the ordinary chondrites and EH chondrites, EL chondrites experienced an extensive low-temperature metamorphic episode. There are now a large number of enstatite meteorite breccias and impact melts, and apparently surface processes were important in determining the present nature of the enstatite chondrites.

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

    Science.gov (United States)

    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.

  13. Extraterrestrial Nucleobases in Carbonaceous Chondrites

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  15. Evidence of Microfossils in Carbonaceous Chondrites

    Science.gov (United States)

    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.

  16. Physical Property Comparison of Ordinary Chondrite Classes

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  18. Trace element geochemistry of CR chondrite metal

    CERN Document Server

    Jacquet, Emmanuel; Alard, Olivier; Kearsley, Anton T; Gounelle, Matthieu

    2015-01-01

    We report trace element analyses by laser ablation inductively coupled plasma mass spectrometry of metal grains from 9 different CR chondrites, distinguishing grains from chondrule interior ("interior grains"), chondrule surficial shells ("margin grains") and the matrix ("isolated grains"). Save for a few anomalous grains, Ni-normalized trace element patterns are similar for all three petrographical settings, with largely unfractionated refractory siderophile elements and depleted volatile Au, Cu, Ag, S. All types of grains are interpreted to derive from a common precursor approximated by the least melted, fine-grained objects in CR chondrites. This also excludes recondensation of metal vapor as the origin of the bulk of margin grains. The metal precursors presumably formed by incomplete condensation, with evidence for high-temperature isolation of refractory platinum-group-element (PGE)-rich condensates before mixing with lower temperature PGE-depleted condensates. The rounded shape of the Ni-rich, interior ...

  19. Chronology of enstatite chondrites and ureilites

    International Nuclear Information System (INIS)

    This paper summarizes the chronological studies on enstatite chondrites and ureilites, both of which are special groups of meteorites with unknown origins. Two unequilibrated enstatite chondrites, Qingzhen and Yamato 6901 (E3), showed the highly disturbed Rb-Sr system, while their silicate fractions yielded the 2.1 Ga isochron. The thermally metamorphosed enstatite chondrite Khairpur (E6) showed the older Rb-Sr age of 4.50 Ga. The parent body of E3 chondrites experienced late thermal event at low temperature, which broke down alkali-bearing sulfides in E3. The observed Rb-Sr data are consistent with the mobilization of Rb from alkali-sulfide to silicate phases. Ureilites show highly depleted trace elements abundance which makes it difficult to determine the age of the formation. The U-Pb and Sm-Nd age determination of low-Ca ureilite Goalpara showed that the Pb and Nd isotopes are heavily contaminated with terrestrial components. The acid residues of high-Ca ureilite MET-78008 were free of contamination and defined the old U-Pb age of 4.563±0.006 Ga. The early formation of ureilites supports their formation through the collisional destruction of the parent body. Including the ureilite date, many evolved meteorites formed within the first 10 million years of the solar system history. Future studies on meteorite chronology with the purpose of understanding the early history of the solar system should focus on the fine time resolution through the precise U-Pb age determination or the relative age determination using the extinct nuclides with half lives less than 10 million years. (author)

  20. Thermal history modeling of the H chondrite parent body

    CERN Document Server

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

    2012-01-01

    The cooling histories of individual meteorites can be empirically reconstructed by using ages from different radioisotopic chronometers with distinct closure temperatures. For a group of meteorites derived from a single parent body such data permit the reconstruction of the cooling history and properties of that body. Particularly suited are H chondrites because precise radiometric ages over a wide range of closure temperatures are available. A thermal evolution model for the H chondrite parent body is constructed by using all H chondrites for which at least three different radiometric ages are available. Several key parameters determining the thermal evolution of the H chondrite parent body and the unknown burial depths of the H chondrites are varied until an optimal fit is obtained. The fit is performed by an 'evolution algorithm'. Empirical data for eight samples are used for which radiometric ages are available for at least three different closure temperatures. A set of parameters for the H chondrite pare...

  1. The Cerro LOS Calvos and La Banderia chondrites

    Science.gov (United States)

    Whitlock, Randall; Lewis, Charles F.; Clark, James C.; Moore, Carleton B.

    1991-06-01

    The Cerro los Calvos meteorite is a single stone of 68.5 g found in the Nuevo Mercurio strewn field of Zacatecas, (Mexico). It is an unusual H4 chondrite. Its olivine (Fa12.5) and orthopyroxene (Fs 11.7, Wo 0.8) are reduced relative to typical H chondrites. The La Banderia meteorite of 54.3 g from the same vicinity is an LL5 chondrite of shock classification e.

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

    Science.gov (United States)

    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 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.

  3. A Collisional Origin to Earth's Non-chondritic Composition?

    OpenAIRE

    Bonsor, Amy; Leinhardt, Zoë M.; Carter, Philip J.; Elliott, Tim; Walter, Michael J.; Stewart, Sarah T.

    2014-01-01

    Several lines of evidence indicate a non-chondritic composition for Bulk Earth. If Earth formed from the accretion of chondritic material, its non-chondritic composition, in particular the super-chondritic 142Nd/144Nd and low Mg/Fe ratios, might be explained by the collisional erosion of differentiated planetesimals during its formation. In this work we use an N-body code, that includes a state-of-the-art collision model, to follow the formation of protoplanets, similar to proto-Earth, from d...

  4. Petrology and Cosmochemistry of a Suite of R Chondrites

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Henke, Stephan; Trieloff, Mario

    2016-01-01

    The construction of models for the internal constitution and the temporal evolution of large planetesimals, the parent bodies of chondrites, requires information on the heat conductivity of the complex mixture of minerals and iron metal found in chondrites. It is attempted to evaluate the heat conductivity of a multi-component mineral mixture and granular medium from the heat conductivities of its mixture components. Random mixtures of solids with chondritic composition and packings of spheres are numerically generated. The heat conduction equation is solved in high spatial resolution for a test cube filled with such matter. From the heat flux through the cube the heat conductivity of the mixture is derived. The model results for porous material are consistent with data for compacted sandstone, but are at odds with measurements for H and L chondrites. The discrepancy is traced back to shock modification of the currently available meteoritic material by impacts on the parent body over the last 4.5 Ga. This cau...

  7. Re-Os isotope geochemistry of three Chinese chondrites

    Institute of Scientific and Technical Information of China (English)

    ZHI XiaChen; QIN Xie; SHI RenDeng; HONG JiAn

    2007-01-01

    Three Chinese ordinary chondrites, including Jilin (H5), Boxian (LL3.8) and Lujiang (LL6), have been studied for their Re and Os abundances and Os isotopic composition in whole-chondrite samples, separated magnetic and nonmagnetic fractions, and nodules.The results indicate that the Re and Os abundances of the whole-chondrite samples are in the ranges of corresponding H- and LL-Groups, respectively.The Re and Os abundances of magnetic fraction from Boxian and Lujiang are within the range of high-Os IIAB and IIIAB irons, whereas those of nonmagnetic fractions of Boxian and Lujiang are lower than the whole-chondrite values.The Re and Os abundances of nodules in Jilin are in the range of the LL-Group.187Re/188Os and 187Os/188Os ratios of the three whole chondrites are in the range of ordinary chondrites which locate around the isochron of IIAB+IIIAB irons.187Re/188Os and 187Os/188Os ratios of the magnetic and nonmagnetic fractions from Boxian have a larger difference.The nonmagnetic fraction of Lujiang may contain a recent addition of Re, which causes deviation of the 187Re/188Os ratio from the irons isochron.The Re and Os abundances of nodules in Jilin are lower than those of the whole-chondrite, but their 187Os/188Os ratios are higher than that of the whole chondrite.

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

    Science.gov (United States)

    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].

  9. Origin of Thorium/Uranium Variations in Carbonaceous Chondrites

    OpenAIRE

    Goreva, J. S.; Burnett, D. S.

    2000-01-01

    Thorium-, U-, and Pb-isotopic analyses of a wide variety of planetary materials show that Th/U ratio (by weight) varies from 3.5 to 4.2. It is generally believed that chondritic meteorites contain refractory lithophile elements in a relative proportions close to solar, i.e., CI chondrites [1]. Surprisingly, a number of analyses of different types of carbonaceous chondrites show a large (at least a factor of 3) scatter in Th/U measurements [2]. The widest spread in Th/U is observed in the most...

  10. Carbonaceous chondrites and the origin of life

    Science.gov (United States)

    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.

  11. Multiple and Fast: The Accretion of Ordinary Chondrite Parent Bodies

    CERN Document Server

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

    2014-01-01

    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 only. Here we propose 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 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: i) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteor...

  12. Characterization of Luminescent Minerals in CM2 Chondrite (Jbilet Winselwan)

    Science.gov (United States)

    Kiku, Y. K.; Ohgo, S. O.; Nishido, H. N.

    2014-09-01

    We have characterized luminescent minerals of forsterite, diopside and spinel in the CM2 chondrite (Jbilet Winselwan) using SEM-CL and to discuss the formation of the luminescent minerals under aqueous conditions.

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

    Science.gov (United States)

    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.

  14. A Common Parent for IIE Iron Meteorite and H Chondrites

    Science.gov (United States)

    Teplyakova, S. N.; Humayun, M.; Lorenz, C. A.; Ivanova, M. A.

    2012-03-01

    We report new siderophile element abundances for the metal in the IIE irons — Watson, Tobychan, Elga, Verkhne Dnieprovsk, and Miles — to examine the possible genetic relations between IIE metal and H chondritic precursors.

  15. Ruthenium Isotopic Composition of Terrestrial Materials, Iron Meteorites and Chondrites

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  18. Distinct Purine Distribution in Carbonaceous Chondrites

    Science.gov (United States)

    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

  19. Terrestrial microbes in martian and chondritic meteorites

    Science.gov (United States)

    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

  20. Chondritic xenon in the Earth's mantle.

    Science.gov (United States)

    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

  1. Microchondrules in three unequilibrated ordinary chondrites

    Science.gov (United States)

    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

  2. Ordinary Chondrite Formation from two Components: Implied Connection to Planet Mercury

    OpenAIRE

    Herndon, J. Marvin

    2004-01-01

    Major element fractionation among chondrites has been discussed for decades as ratios relative to Si or Mg. Expressing ratios relative to Fe leads to a new relationship admitting the possibility that ordinary chondrite meteorites are derived from two components: one is a relatively undifferentiated, primitive component, oxidized like the CI or C1 chondrites; the other is a somewhat differentiated, planetary component, with oxidation state like the reduced enstatite chondrites. Such a picture ...

  3. On the aerodynamic redistribution of chondrite components in protoplanetary disks

    CERN Document Server

    Jacquet, Emmanuel; Fromang, Sébastien

    2012-01-01

    Despite being all roughly of solar composition, primitive meteorites (chondrites) present a diversity in their chemical, isotopic and petrographic properties, and in particular a first-order dichotomy between carbonaceous and non-carbonaceous chondrites. We investigate here analytically the dynamics of their components (chondrules, refractory inclusions, metal/sulfide and matrix grains) in protoplanetary disks prior to their incorporation in chondrite parent bodies. We find the dynamics of the solids, subject to gas drag, to be essentially controlled by the "gas-solid decoupling parameter" $S\\equiv \\textrm{St}/\\alpha$, the ratio of the dimensionless stopping time to the turbulence parameter. The decoupling of the solid particles relative to the gas is significant when $S$ exceeds unity. $S$ is expected to increase with time and heliocentric distance. On the basis of (i) abundance of refractory inclusions (ii) proportion of matrix (iii) lithophile element abundances and (iv) oxygen isotopic composition of chon...

  4. Rapid Classification of Ordinary Chondrites Using Raman Spectroscopy

    Science.gov (United States)

    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.

  5. Morro do Rocio - an unequilibrated H5 chondrite

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. Carbonaceous Chondrite Fragments in the Polymict Eucrite Yamato 791834

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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).

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

    Science.gov (United States)

    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 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.

  10. Nitrogen and light noble gases in Parsa enstatite chondrite

    Science.gov (United States)

    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.

  11. Petrology of Two Itokawa Particles: Comparison with Equilibrated LL Chondrites

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. Microscale Distribution of Hydrogen Isotopes in Two Carbonaceous Chondrites

    Science.gov (United States)

    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].

  15. An interplanetary dust particle with links to CI chondrites

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    International Nuclear Information System (INIS)

    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 ∼105 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Vernazza, P.; Barge, P. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Zanda, B.; Hewins, R. [Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), Sorbonne Universités, Muséum National d' Histoire Naturelle, UPMC Université Paris 06, UMR CNRS 7590, IRD UMR 206, 61 rue Buffon, F-75005 Paris (France); Binzel, R. P.; DeMeo, F. E.; Lockhart, M. [Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Hiroi, T. [Department of Geological Sciences, Brown University, Providence, RI 02912 (United States); Birlan, M. [IMCCE, Observatoire de Paris, 77 Av. Denfert Rochereau, F-75014 Paris Cedex (France); Ricci, L. [California Institute of Technology, MC 249-17, Pasadena, CA, 91125 (United States)

    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.

  20. Surviving High-temperature Components in CI Chondrites

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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).

  2. Comparing Amino Acid Abundances and Distributions Across Carbonaceous Chondrite Groups

    Science.gov (United States)

    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.

  3. Petrogenesis of opaque assemblages in the Ningqiang carbonaceous chondrite

    Institute of Scientific and Technical Information of China (English)

    HSU; WeiBiao

    2007-01-01

    Numerous round to oblate opaque assemblages (OAs) are found in chondrules and matrix of the Ningqiang carbonaceous chondrite. They are mainly composed of Ni-rich metal,magnetite,Fe,Ni-sulfides,with minor amounts of phosphate,phosphoran-olivine,pyroxene and trace amounts of nano-sized platinum-group metal alloys. The mineralogy of Ningqiang OAs is very similar to that of OAs previously reported in Ca,Al-rich inclusions of CV chondrites. Being a rare mineral phase in nature,phosphoran-olivine is thought to form by nonequilibrium reactions between P-bearing molten metal and olivine crystals during rapid cooling. Its occurrence in Ningqiang OAs indicates that the precursor of OAs was locally produced during chondrule formation,rather than directly condensed from the solar nebula as previously thought. The petrographic and mineralogical characteristics of Ningqiang OAs reveal that OAs formed by low temperature alterations of pre-existing homogeneous alloys within chondrules on a planetary body.

  4. Origin and chronology of chondritic components: A review

    Science.gov (United States)

    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 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 near the proto-Sun ( -10‰) and have ( 26Al/ 27Al) 0 similar to those in chondrules (events in regions with low ambient temperature

  5. Glanggang and Selakopi - Two new paired Indonesian chondrites

    Science.gov (United States)

    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.

  6. New Titanium Monosulfide Mineral Phase in Yamato 691 Enstatite Chondrite

    Science.gov (United States)

    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.

  7. The Tuxtuac, Mexico, meteorite, an LL5 chondrite fall

    Science.gov (United States)

    Graham, A. L.; Michel-Levy, M. Christophe; Danon, J.; Easton, A. J.

    1988-12-01

    The Tuxtuac meteorite fell in Zacatecas state, Mexico, on October 16, 1975, at 1820 hours. Two partly crusted masses, weighing 1924 g and 2340 g, were recovered. The stone is an ordinary chondrite, LL5, with olivine Fa30 and 19.22 wt pct total iron. The silicates contain numerous voids and a froth-like mesostasis is present within some chondrules. Metal phases present are kamacite (5.7-6.4 pct Ni, 6-7 pct Co) and high nickel metal (taenite 37-41 pct Ni, 1.7 + or - 0.3 pct Co; tetrataenite 47-52 pct Ni, 0.8-1.4 pct Co). The stone is unusual for an LL-group chondrite in that it exhibits neither large-scale brecciation features nor dark veins.

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

    Science.gov (United States)

    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.

  9. Magmatic sulfides in the porphyritic chondrules of EH enstatite chondrites

    CERN Document Server

    Piani, Laurette; Libourel, Guy; Tissandier, Laurent

    2016-01-01

    The nature and distribution of sulfides within 17 porphyritic chondrules of the Sahara 97096 EH3 enstatite chondrite have been studied by backscattered electron microscopy and electron microprobe in order to investigate the role of gas-melt interactions in the chondrule sulfide formation. Troilite (FeS) is systematically present and is the most abundant sulfide within the EH3 chondrite chondrules. It is found either poikilitically enclosed in low-Ca pyroxenes or scattered within the glassy mesostasis. Oldhamite (CaS) and niningerite [(Mg,Fe,Mn)S] are present in about 60% of the chondrules studied. While oldhamite is preferentially present in the mesostasis, niningerite associated with silica is generally observed in contact with troilite and low-Ca pyroxene. The chondrule mesostases contain high abundances of alkali and volatile elements as well as silica. Our data suggest that most of the sulfides found in EH3 chondrite chondrules are magmatic minerals that formed after the dissolution of S from a volatile-r...

  10. Timescales and settings for alteration of chondritic meteorites

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. FORMING CHONDRITES IN A SOLAR NEBULA WITH MAGNETICALLY INDUCED TURBULENCE

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Wakita, Shigeru; Matsumoto, Yuji; Oshino, Shoichi, E-mail: yasuhiro@caltech.edu [Center for Computational Astrophysics, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2016-03-20

    Chondritic meteorites provide valuable opportunities to investigate the origins of the solar system. We explore impact jetting as a mechanism of chondrule formation and subsequent pebble accretion as a mechanism of accreting chondrules 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 ≤10{sup 24} g (≤500 km in radius) in the solar nebula, impact jetting and subsequent pebble accretion can reproduce a number of properties of the meteoritic data. The properties include the present asteroid belt mass, the 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’ masses leads to the following implications: primordial asteroids that were originally ≥10{sup 24} 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 the origins of the solar system.

  12. Origin of unusual impact melt rocks, Yamato-790964 and 790143 (LL-chondrites)

    OpenAIRE

    Yamaguchi,Akira/Scott,Edward R.D./Keil,Klaus

    1998-01-01

    We have studied Yamato (Y)-790964 and-790143,which are unusual paired impact-melted LL chondrites. Some petrologic aspects of these impact melt rocks are similar to those of the impact melted L-chondrite, Ramsdorf; these meteorites experienced nearly total melting, yet partly preserve chondritic textures. Olivine and chromite grains in Y-790964 and olivine in Y-790143 are the only relicts of the precursor materials; they were solid clasts during impact melting. All other portions (i.e., chond...

  13. Investigation of the chemical composition of mineral fractions of the Tsarev chondrite

    Energy Technology Data Exchange (ETDEWEB)

    Semenova, L.F.; Fisenko, A.V.; Kashkarova, V.G.; Melnikova, L.N.; Bezrogova, E.V.; Pomytkina, V.A.; Lavrukhina, A.K.

    1984-01-01

    A selective-dissolution method was used to study the chemical composition of mineral fractions of the Tsarev chondrite. Redistributions of Na, K, and P were found in mineral fractions of L-chondrites which have experienced different degrees of impact metamorphism. It is shown that the normative composition of inclusions in olivine in the Tsarev chondrite is characterized by a high content of diopside and anorthite components. 24 references.

  14. Lunar and Planetary Science XXXV: Organics and Alteration in Carbonaceous Chondrites: Goop and Crud

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. Group IIE Iron Meteorites; Metal Composition, Formation, Relationship to Ordinary Chondrites

    Science.gov (United States)

    Wasson, J. T.; Scott, E. R. D.

    2011-03-01

    INAA data for metal in 8 new and 12 known IIE irons show they crystallized from various silicate-rich Fe-Ni melts with diverse S contents after impacts melted an ordinary chondrite asteroid that was probably more reduced than H chondrites.

  17. Chemical and physical studies of type 3 chondrites. VII - Annealing studies of the Dhajala H3.8 chondrite and the thermal history of chondrules and chondrites

    Science.gov (United States)

    Keck, B. D.; Guimon, R. K.; Sears, D. W. G.

    1986-01-01

    Samples of the Dhajala meteorite were annealed at 600-1000 C for 1, 2, 10, 20 and 100 h and their thermoluminescence (TL) properties were measured. After annealing at less than 900 deg, the TL sensitivity decreased by a factor of two; at higher temperatures, it fell by an order of magnitude. Data indicate that the annealing treatment caused the low-temperature feldspar in Dhajala to be converted to feldspar of a high-temperature (disordered) form. Low-temperature feldspar was found in the meteorite's TL-sensitive chondrules which comprised about 20 percent of those separated. It is suggested that these chondrules suffered greater crystallization of their mesostasis than the other chondrules, and equilibrated to lower temperatures. Based on TL data, there appears to be no relationship between post-metamorphic cooling rate and petrologic type for the 3.5-3.9 chondrites.

  18. Organic matter and metamorphic history of CO chondrites

    Science.gov (United States)

    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) 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 graphitized carbon [Rietmeijer, F., and MacKinnon, I. (1985) Poorly graphitized carbon as a new cosmothermometer for primitive extraterrestrial materials. Nature, 315, 733-736]. The trapped noble gas and C content appear to be sensitive but not precise metamorphic tracers, indicating that the "Ornans

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  1. Total Mass of Ordinary Chondrite Matter Originally Present in the Solar System

    CERN Document Server

    Herndon, J M

    2004-01-01

    Recently, I reported the discovery of a new fundamental relationship of the major elements (Fe, Mg, Si) of chondrites that admits the possibility that ordinary chondrite meteorites are derived from two components, a relatively oxidized and undifferentiated, primitive component and a somewhat differentiated, planetary component, with oxidation state like the highly reduced enstatite chondrites, which I suggested was identical to Mercury's complement of lost elements. Subsequently, on the basis of that relationship, I derived expressions, as a function of the mass of planet Mercury and the mass of its core, to estimate the mass of Mercury's lost elements, the mass of Mercury's alloy and rock protoplanetary core, and the mass of Mercury's gaseous protoplanet. Here, on the basis of the supposition that Mercury's complement of lost elements is in fact identical to the planetary component of ordinary chondrite formation, I estimate, as a function of Mercury's core mass, the total mass of ordinary chondrite matter o...

  2. Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts

    CERN Document Server

    Reddy, Vishnu; 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

    2012-01-01

    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 {\\mu}m 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 howar...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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 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 previous generations of

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

    Science.gov (United States)

    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.

  11. Cosmogenic Radionuclides in Recently Fallen Chondrites Mihonoseki and Tahara

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  13. STARDUST INVESTIGATION INTO THE CR CHONDRITE GROVE MOUNTAIN 021710

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Xuchao; Lin Yangting [Key Laboratory of the Earth' s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beituchengxi Road, Beijing 100029 (China); Floss, Christine [Laboratory for Space Sciences and Physics Department, Washington University, One Brookings Drive, St. Louis, MO 63130 (United States); Bose, Maitrayee, E-mail: linyt@mail.igcas.ac.cn [Department of Chemistry and Biochemistry, Arizona State University, P.O. Box 871604, Tempe, AZ 85287 (United States)

    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.

  14. Petrologic evidence for collisional heating of chondritic asteroids

    Science.gov (United States)

    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.

  15. Thermal and Impact History of the H Chondrite Parent Asteroid during Metamorphism: Constraints from Metallic Fe-Ni

    CERN Document Server

    Scott, Edward R D; Goldstein, Joseph I; Wakita, Shigeru

    2014-01-01

    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 Ar-Ar ages greater than 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 to 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, St...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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?

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  1. Microbeam analysis of four chondritic interplanetary dust particles for major elements, carbon and oxygen

    Science.gov (United States)

    Blanford, G. E.; Thomas, K. L.; Mckay, D. S.

    1988-01-01

    Chemical compositions determined using electron excited X-rays are reported for four interplanetary dust particles collected in the stratosphere. These analyses include measurements of carbon and oxygen abundances which are important elements in these primitive materials. Spot analyses show very heterogeneous compositions on a micrometer scale although average composition approaches that of C1 carbonaceous chondrites. While the spot analyses show intermediate compositions between cometary dust and carbonaceous chondrites, the heterogeneity more closely resembles that of comet Halley dust particles.

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

    Science.gov (United States)

    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.

  3. Super-chondritic Sm/Nd in Mars, Earth, and the Moon

    Science.gov (United States)

    Caro, G.; Bourdon, B.; Halliday, A. N.; Quitté, G.

    2007-12-01

    Differences in the isotopic abundance of 142Nd in planetary materials reflect the chronology and mechanisms by which crustal reservoirs formed during or shortly after accretion. Interpretation of these differences assumes that the terrestrial planets have a composition identical to that of chondritic meteorites. The ca. 20 ppm difference in 142Nd/144Nd between chondrites and the Earth's upper mantle may thus indicate very early (Rotenberg, E., Earth Planet. Sci. Lett. 223, 267-282 (2004).

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 (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.

  6. Some refractory and volatile element chemistry of CaS in enstatite chondrites

    Institute of Scientific and Technical Information of China (English)

    陈永亨; Paul H.Benoit

    1996-01-01

    INAA data for REE, Sc, Se, Br and Zn in CaS extracted from 5 enstatite chondrites (Qingzhen EH3, St. Marks EH5, Atlanta EL6, Hvittis EL6 and Pillistfer EL6) are reported. The results indicate that the REE abundances in CaS from unequilibrated enstatite chondrite, Qingzhen, are much higher than that from equilibrated ones. Similarly, the abundances of Sc, Se, Br and Zn in CaS from Qingzhen are higher than that in CaS grains from equilibrated chondrites, revealing that CaS is a previous condensate and is not simple residues of an evaporative process. Secondly, metamorphism has caused the redistribution of the trace elements among the minerals in enstatite chondrites, and this metamorphic fractionation reflects the differences from element volatilities and chemical properties. The REE patterns of CaS of enstatite chondrites and aubrites could not explain that aubrites were derived from known enstatite chondrites by igneous processing. And depleted europium in metamorphism and igneous process may be carried

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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).

  10. Bulk Chemical Composition of the Ningqiang Carbonaceous Chondrite:An Issue of Classification

    Institute of Scientific and Technical Information of China (English)

    WANG Guiqin; LIN Yangting

    2007-01-01

    The Ningqiang meteorite is a fall carbonaceous chondrite, containing various Ca-, Al-rich inclusions that usually escaped from secondary events such as high-temperature heating and lowtemperature alteration. However, it has not yet been classified into any known chemical group. In order to address this issue, 41 elements of the bulk Ningqiang meteorite were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atom emission spectrometry (ICP-AES) in this study. The Allende (CV3) carbonaceous chondrite and the Jilin (H5)ordinary chondrite were also measured as references, and our analyses are consistent with the previous results. Rare earth and other refractory lithophile elements are depleted in Ningqiang relative to both Allende and mean CK chondrites. In addition, the REE pattern of Ningqiang is nearly flat, while that of Allende shows slight enrichment of LREE relative to HREE. Siderophile elements of Ningqiang are close to those of mean CK chondrites, but lower than those of Allende. Our new analyses indicate that Ningqiang cannot be classified into any known group of carbonaceous chondrites, consistent with previous reports.

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

    Science.gov (United States)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  15. Cosmic-ray exposure ages of the ordinary chondrites and their significance for parent body stratigraphy

    Science.gov (United States)

    Crabb, J.; Schultz, L.

    1981-01-01

    Improved exposure ages are derived for 201 H, 203 L, and 38 LL chondrites in an effort to understand the characteristics of the chondrite parent body. The Ne-21 exposure ages were calculated from literature values taking into account shielding differences, a trapped component and radiogenic He. The exposure age distributions show clear peaks at 4.5 and 20 million years for the H chondrites, while the Ls and LLs appear more as a continuous series of intermediate peaks which may be modeled by at least six peaks between 1 and 35 million years in the case of L chondrites. The observations that every petrological type occurs in each large peak and contain solar wind gases suggest that the parent bodies have been fragmented and reassembled into a megabreccia. The H meteorites are proposed to represent the surface layer of a body with a substantial, active regolith as indicated by the relatively high abundances of solar gases. The L chondrites, on the other hand, are attributed to a parent body that was fragmented by collision about 500 million years ago.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    Science.gov (United States)

    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.

  19. Chondritic xenon in the Earth’s mantle

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 ± Floss et al. 2009. Ap. J. 697: 1242-1255. [2] Abreu N. M. 2007. [3] Tomeoka K. & Buseck P. R. 1988. GCA 52: 1627-1640. [4] Tomeoka K. & Buseck P. R. 1985. GCA 49: 21-49-2163. [5] Rubin A. et al. 2007. GCA 71: 2361-2382. Acknowledgements: Funded by NNX11AH10G grant and conducted at Penn State and ARES-JSC. Meteorite kindly pro-vided by the JSC Antarctic meteorite curators.

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

    CERN Document Server

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

    2015-01-01

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

  2. Sepctral Reflectance of Recently Fallen Chondrites and Some Igneous Rocks in China

    Institute of Scientific and Technical Information of China (English)

    林文祝; 高来之

    1991-01-01

    Polarization and radiation measurements and microwave studies show that the planets and the great majority of asteroids in the solar system are covered by soils similar to regolith on the moon surface.The soils repesent the composition of the asteroids and the geological elements of the planets. The spectral reflectance shows a tendency of decreasing from near ultraviolet,visible to near-infrared in order of LL→L→H→H with increasing Fe0/Fet rato and toward to absorption for Jilin,Xinyang and Zanoyang ordinary chondrites and Qinzhen enstatite chondrite recently fallen in China,The same chemical group of meteorites feature deeper absorption valleys with increasing metamorphic grade.The spectal reflectance of igneous rocks varies from strong to what is like that of H-group chondrites in order of acid→basic→ultrabasic rocks.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 soils during wetter periods and were recently exhumed by removal of these soils due to deflation during more arid periods, such as the current one, which started ~3000 years ago. Finally, based on the 26Al/21Ne and 10Be/21Ne systematics in 16 DaG meteorites, we derived more reliable estimates of the 10Be/21Ne production rate ratio, which seems more sensitive to shielding than was predicted by the semi-empirical model of Graf et al. (1990) but less sensitive than was predicted by the purely physical model of Leya et al. (2000).

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  7. The Confirmation of a New Type of Chondrites and Their Cosmochemical Significance

    Institute of Scientific and Technical Information of China (English)

    侯渭

    1996-01-01

    The data available show that some Antarctic carbonaceous chondrites are similar to Cl meteorites.Tehy contain a lot of phyllosilicate aggregates and the oxygen isotopic composition of the whole-rock samples is approximate to that of C1 chondrites,so they are named after quasi-C1(Q-C1)chondrites Unlike Cl metcorites,the Q-Cl chondites possess chondrule structrue,and the compositions of hih temperature condensates(chondrule fragments,mineral grains or aggregates)show that the oxygen fugacity varied within a wide range in the surroundings where they were formed,similar to the variation range from E.H.L,LL to C group chondrites.It is inferred that the Q-C1 chondrites could be formed at the edges far from the equator in the whole asteroid region of the solar nebular disk.where the nebula was lower in density and the condensates were lower in accretion velocity,so that the hydration of chon drules and matrix occurred during the late stage of nebular condensation.The discovery of the Q-Cl chondrites and the fact that the earth and other terrestrial planets contain water indicate that at the edges far from the equator in the terrestrial reigion of the solar nebular disk,a large amount of water was incorporated into the lattice of minerals in the condensates as a result of hydration during nebular condensation,and then found its way into the interior parts of the Earth and other terrestrial planets due to accretion.

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

    Science.gov (United States)

    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

  9. Pb-Pb dating of individual chondrules from the CBa chondrite Gujba

    DEFF Research Database (Denmark)

    Bollard, Jean Francois André; Connelly, James; Bizzarro, Martin

    2015-01-01

    with a weighted mean age of 4562.49±0.21Myr, consistent with its origin from the vapor-melt impact plume generated by colliding planetesimals. Formation in a debris disk mostly devoid of nebular gas and dust sets an upper limit for the solar protoplanetary disk lifetime at 4.8±0.3Myr. Finally, given the well......-stage impact origin. Here, we report high-precision internal isochrons for four individual chondrules of the Gujba chondrite to probe the formation history of CB chondrites and evaluate the concordancy of relevant short-lived radionuclide chronometers. All four chondrules define a brief formation interval...

  10. 40Ar - 39Ar dating of meteorites and the history of chondrite parent bodies

    International Nuclear Information System (INIS)

    The 40Ar-39Ar analyses of eleven ordinary chondrites and the unique meteorite Pontylyfni are presented. Results of previous 40Ar-39Ar age analyses have shown that the uncertainty in the calculated ages arises principally from the difficulties of interpretation of release patterns obtained from stepped heating experiments. For this reason considerable attention is paid to identifying the causes of complicating features in the age spectra. The ages obtained range from 4.52Ga to a lower limit of 4.38Ga and it is inferred that these date the time of cooling of the chondrites after formation and metamorphism. (author)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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].

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

    Science.gov (United States)

    Fegley, B.; Post, J. E.

    1985-11-01

    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.

  14. Petrologic Locations of Nanodiamonds in Carbonaceous Chondrite Meteorites

    Science.gov (United States)

    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

  15. Oxygen isotope systematics of chondrules in the Allende CV3 chondrite: High precision ion microprobe studies

    Digital Repository Service at National Institute of Oceanography (India)

    Rudraswami, N.G.; Ushikubo, T.; Nakashima, D.; Kita, N.T.

    in local dust-rich protoplanetary disk, from which the CV3 parent asteroid formed. A compilation of 225 olivine and low-Ca pyroxene isotopic data from 36 chondrules analyzed in the present study lie between carbonaceous chondrite anhydrous mineral (CCAM...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

    Science.gov (United States)

    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.

  19. Type distribution pattern and pairing of ordinary chondrites from Grove Mountains, Antarctica

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Twenty-eight meteorites were collected on blue ice in the Grove Mountains region, Antarctica, by the 16th Chinese Antarctic Research Expedition (CHINARE). 26 out of the stones are ordinary chondrites, and their chemical-petrographic types are assigned based on electron probe microanalyses, petrography and mineralogy. 6 of them are unequilibrated L-chondrites, and the other 20 chondrites are equilibrated, including 6 H-group (3 H4, 1 H5 and 2 H6), 9 L-group (3 L4, 1 L5 and 5 L6) and 5 LL-group (2 LL4 and 3 LL5). Detailed comparative study suggests that 10 of them (including other 2 chondrites collected by the 15th CHINARE) could be paired, and represent 5 individual fall events. Hence, all 32 meteorites collected from the Grove Mountains probably belong to 27 fall events, suggestive of meteorite transferring and concentrating processes. The Grove Mountains are likely a new meteorite-enriched region. Distribution patterns of chemical-petrographic type and mass of the Grove Mountains meteorites are significantly distinct from those found in other regions, indicative of their unique sources and/or concentration mechanism. However, more studies are required in order to clarify these differences.

  20. The Compositions of Six Chinese Ordinary Chondrites and Element Distributions in Their Different Phases

    Institute of Scientific and Technical Information of China (English)

    陈永亨; ERNSTPERNICKA; 等

    1992-01-01

    Six Chinese ordinary chondrites (four of them have fallen in recent years and the trace element abundances have not yet been reported for the other two) were examined.The contents of 21 elements (Na,Cr,Mn,Sc,Se,Zn,Br,Ni,Fe,Co,Ir,Cu,Ga,As,Au,Sb,Os,W,Re,Pt,and Ru)in the magnetic fractions and 20 elements (Na,K,Ca,Sc,Cr,Mn,Fe,Co,Ni,Zn,Se,Br,La,Sm,Eu,Yb,Lu,Ir,Au,and As) in the non-magnetic fractions were de-termined by INAA. The results indicate that the 5 H-group chondrites show almost no difference in composition,but they are different from the Zhaodong L-group chondrite in elemental abundance.As a normalized element(relative to CI),the concentrations of Ga in the magnetic fractions can be used to classify ordinary chondrites(H-,L- and LL-group).The bulk composition and modal weight of each component calculated from element concentrations in different phases are in good agreement with the bulk rock analyses presented in the literature.

  1. Characteristics in naturally and experimentally shocked chondrites: A clue to P-T conditions of impacted asteroids

    Institute of Scientific and Technical Information of China (English)

    谢先德; 陈鸣; 戴诚达; A.EI; Goresy

    2000-01-01

    The aim of this study is to compare the experimentally shock-induced features with those in naturally shocked chondrites and to test the feasibility of experimentally calibrating naturally induced features in shocked H- and L-chondrites. Samples of the Jilin chondrite (H5) were experimentally shock-loaded at the following peak pressures: 12, 27, 39, 53, 78, 83, 93 and 133 GPa respectively. Chondritic melts were first obtained at P>78 GPa and more than 60% melting was achieved at P~133 GPa. No high-pressure phases were observed in any of the shocked samples, neither in the deformed nor in the molten regions. Textural relations and mineral assemblages of the shocked samples are comparable to those encountered in the heavily shocked H-chondrite Yanzhuang but differ considerably from those found in heavily shocked L6 chondrites. Shock melt veins in L6 chondrites contain high-pressure polymorphs of olivine and pyroxene and high pressure liquidus phases. Scaling from shock experiments on millimeter-sized sam

  2. Characteristics in naturally and experimentally shocked chondrites: A clue to P-T conditions of impacted asteroids

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The aim of this study is to compare the experimentally shock-induced features with those in naturally shocked chondrites and to test the feasibility of experimentally calibrating naturally induced features in shocked H- and L-chondrites. Samples of the Jilin chondrite (H5) were experimentally shock-loaded at the following peak pressures: 12, 27, 39, 53, 78, 83, 93 and 133 GPa respectively. Chondritic melts were first obtained at P>78 GPa and more than 60% melting was achieved at P~133 GPa. No high-pressure phases were observed in any of the shocked samples, neither in the deformed nor in the molten regions. Textural relations and mineral assemblages of the shocked samples are comparable to those encountered in the heavily shocked H-chondrite Yanzhuang but differ considerably from those found in heavily shocked L6 chondrites. Shock melt veins in L6 chondrites contain high-pressure polymorphs of olivine and pyroxene and high pressure liquidus phases. Scaling from shock experiments on millimeter-sized samples to natural shock features on kilometer-sized asteroids poses considerable problems in quantifying the P-T conditions during natural shock events on asteroids.

  3. Trace element evidence for contrastive thermal histories of H4-6 and L4-6 chondrite parent bodies

    Energy Technology Data Exchange (ETDEWEB)

    Lingner, D.W.

    1985-01-01

    Earlier studies at Purdue revealed that tertiary shock (impact) heating is the main post-accretionary fractionation process for mobile and siderophilic trace elements in L4-6 chondrites. Lower contents of these elements in samples evidencing shock are attributable to loss (transport in an Fe-Ni-S eutectic or volatilization from collisional debris) upon breakup of the L parent body 500-650 Myr ago. Reported here are new radiochemical neutron activation analysis results for Ag, As, Au, Bi, Cd, Co, Cs, Ga, In, K, Rb, Sb, Se, Te, Tl and Zn in H4-6 chondrites as a function of /sup 40/Ar retention (a reliable shock indicator in L chondrites). Mobile element depletion in H chondrites with undisturbed /sup 40/Ar vs. unshocked L chondrites indicates a hotter environment (a shock event or higher accretion temperatures) for the former. Siderophiles are enriched in H relative to L chondrites, as expected. Within the H chondrite population, trace element relationships with /sup 40/Ar retention and petrologic type are complex and puzzling. These are discussed in detail in light of several proposed parent body models.

  4. The formation and alteration of the Renazzo-like carbonaceous chondrites

    Science.gov (United States)

    Schrader, Devin Lee

    This study investigates the pre-accretionary formation conditions of individual minerals within chondrules and whole-rock parent asteroid processes from the Renazzo-like carbonaceous (CR) chondrites. It presents a comprehensive work on the whole-rock O-isotope composition, sulfide-bearing opaque minerals, and type-II chondrules within the CR chondrites. Whole-rock O-isotope composition and minerals present in type-II chondrules are found to be related to the degree of parent asteroid aqueous alteration. Primary minerals within chondrules, formed prior to accretion of the CR chondrite parent asteroid, are used to constrain both the environment and the conditions present during chondrule formation. Chondrule formation, as recorded by chondrules in the CR chondrites, took place under dust- and ice-rich conditions relative to solar values. Type-II (FeO-rich) chondrules contain FeO-poor fragments compositionally similar to type-I (FeO-poor) chondrules; the formation of type-II chondrules may have occurred after the formation of type-I chondrules. The dust and ice abundances present during type-II chondrule formation were higher than those of type-I chondrules, although both populations probably exchanged with the same 16O-poor gas reservoir. Both the oxygen fugacity (fo 2) and sulfur fugacity (fs2) appear to have increased from type-I to type-II chondrule formation, and between individual type-II chondrules. The increase in fo2 and fs2 may be due to the dissipation of H2 in the early Solar System. Gas-solid oxidation/sulfidation of Fe,Ni metal is recorded in both type-I and type-II chondrules. This corrosion occurred either during chondrule cooling after formation, or during chondrule reheating events, and suggests that S was present in the gas phase. After chondrule formation the CR chondrite parent asteroid accreted 16O-poor ice and experienced variable degrees of aqueous alteration, possibly due to heterogeneity in accreted ice or ammonia abundances and/or differing

  5. Late Chondritic Additions and Planet and Planetesimal Growth: Evaluation of Physical and Chemical Mechanisms

    Science.gov (United States)

    Righter, Kevin

    2013-01-01

    Studies of terrestrial peridotite and martian and achondritic meteorites have led to the conclusion that addition of chondritic material to growing planets or planetesimals, after core formation, occurred on Earth, Mars, asteroid 4 Vesta, and the parent body of the angritic meteorites [1-4]. One study even proposed that this was a common process in the final stages of growth [5]. These conclusions are based almost entirely on the highly siderophile elements (HSE; Re, Au, Pt, Pd, Rh, Ru, Ir, Os). The HSE are a group of eight elements that have been used to argue for late accretion of chondritic material to the Earth after core formation was complete (e.g., [6]). This idea was originally proposed because the D(metal/silicate) values for the HSE are so high, yet their concentration in the mantle is too high to be consistent with such high Ds. The HSE also are present in chondritic relative abundances and hence require similar Ds if this is the result of core-mantle equilibration. Since the work of [6] there has been a realization that core formation at high PT conditions can explain the abundances of many siderophile elements in the mantle (e.g., [7]), but such detailed high PT partitioning data are lacking for many of the HSE to evaluate whether such ideas are viable for all four bodies. Consideration of other chemical parameters reveals larger problems that are difficult to overcome, but must be addressed in any scenario which calls on the addition of chondritic material to a reduced mantle. Yet these problems are rarely discussed or emphasized, making the late chondritic (or late veneer) addition hypothesis suspect.

  6. Oxygen isotopic constraints on the origin of Mg-rich olivines from chondritic meteorites

    Science.gov (United States)

    Libourel, Guy; Chaussidon, Marc

    2011-01-01

    Chondrules are the major high temperature components of chondritic meteorites which accreted a few millions years after the oldest solids of the solar system, the calcium-aluminum-rich inclusions, were condensed from the nebula gas. Chondrules formed during brief heating events by incomplete melting of solid dust precursors in the protoplanetary disk. Petrographic, compositional and isotopic arguments allowed the identification of metal-bearing Mg-rich olivine aggregates among the precursors of magnesian type I chondrules. Two very different settings can be considered for the formation of these Mg-rich olivines: either a nebular setting corresponding mostly to condensation-evaporation processes in the nebular gas or a planetary setting corresponding mostly to differentiation processes in a planetesimal. An ion microprobe survey of Mg-rich olivines of a set of type I chondrules and isolated olivines from unequilibrated ordinary chondrites and carbonaceous chondrites revealed the existence of several modes in the distribution of the ∆17O values and the presence of a large range of mass fractionation (several ‰) within each mode. The chemistry and the oxygen isotopic compositions indicate that Mg-rich olivines are unlikely to be of nebular origin (i.e., solar nebula condensates) but are more likely debris of broken differentiated planetesimals (each of them being characterized by a given ∆17O). Mg-rich olivines could have crystallized from magma ocean-like environments on partially molten planetesimals undergoing metal-silicate differentiation processes. Considering the very old age of chondrules, Mg-rich olivine grains or aggregates might be considered as millimeter-sized fragments from disrupted first-generation differentiated planetesimals. Finally, the finding of only a small number of discrete ∆17O modes for Mg-rich olivines grains or aggregates in a given chondrite suggests that these shattered fragments have not been efficiently mixed in the disk and

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

    Science.gov (United States)

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

    2013-12-01

    Isotopic similarity between the Earth-Moon system and enstatite chondrites (ECs) led to the idea that ECs were Earth's building blocks [1-3]. However, compared to Earth's mantle, ECs have low Fe0/Fe ratios, are enriched in volatile elements, and depleted in refractory lithophile elements and Mg [4]. Therefore, deriving Earth composition from ECs requires a loss of volatiles during or prior to accretion and sequestering a large fraction of Si in the deep Earth. Alternatively, the isotopic similarity between the Earth and ECs is explained by their formation from a common precursor that experienced different evolutionary paths resulting in the chemical difference [4]. The vestiges of such a precursor are still present in the unequilibrated ECs as FeO-rich silicates with O isotopic compositions identical to bulk ECs and Earth [5]. Conversion of such a precursor into the characteristic EC mineral assemblage requires high-temperature processing in an H-poor environment with high fS2 and fO2 close to that of the classic solar nebula [6], consistent with redox conditions inferred from Ti4+/Ti3+ ratios in EC pyroxene [7]. Under such conditions reaction of FeO-rich silicates with S-rich gas results in their replacement by the assemblage of FeO-poor silicates; Fe, Mg, Ca sulfides; free silica; and Si-bearing Fe,Ni metal alloy. The progressive sulfidation of ferromagnesian silicates in chondrules results in loss of Mg and addition of Fe, Mn, S, Na, K and, perhaps, other volatiles [6]. At the advanced stages of silicate sulfidation recorded in the metal-sulfide nodules [8], a portion of Si is reduced and dissolved in the Fe,Ni metal. This process is known to fractionate Si isotopes [9,10] and would explain the differences between the ECs and Earth's mantle [11]. The sulfidation of silicates also produces porous S-rich silica, a peculiar phase observed so far only in the ECs. It consists of a sinewy SiO2-rich framework enclosing numerous vesicles filled with beam

  8. A 3.6-b.y.-old impact-melt rock fragment in the Plainview chondrite: Implications for the age of the H-group chondrite parent body regolith formation

    International Nuclear Information System (INIS)

    Major, minor, trace and REE abundances as well as mineralogical and textural properties of a light-colored, poikilitic, metallic nickel-iron- and troilite-poor lithic fragment in the brecciated Plainview, Texas, H5 chondrite unambiguously show that the fragment is of H-group chondrite parentage, despite its non-chondritic texture and appearance. 40Ar-39Ar age dating indicates that the fragment is 3.63 b.y. old, whereas the Plainview host chondrite is 4.4 b.y. old. The fragment's texture and certain mineral compositions, such as relatively high CaO in olivine and orthopyroxene, the presence of alkali-rich feldspar and interstitial material, and metallic nickel-iron of Ni contents of 10-15 wt.% (martensite), indicate that the fragment formed by relatively fast cooling from a melt. (orig./ME)

  9. Oxygen Isotopic and Petrological Constraints on the Origin and Relationship of IIE Iron Meteorites and H Chondrites

    Science.gov (United States)

    McDermott, K. H.; Greenwood, R. C.; Franchi, I. A.; Anand, M.; Scott, E. R. D.

    2011-03-01

    New oxygen isotopic measurements of IIEs and H chondrites are indistinguishable — strengthening a possible common origin for these groups. Combining oxygen results with mineralogy, the nature of their parent body or bodies can be explored.

  10. Rare Earth Element Abundances and Pb-Pb Ages of Merrillite in Jinju H5 Chondrite: Implications to Shock Metamorphism

    Science.gov (United States)

    Goh, S.; Choi, B.-G.

    2016-08-01

    Jinju merrillite shows homogeneous REE abundances and relatively young Pb-Pb ages. Jinju H5 chondrite was probably neither equilibrated nor compacted prior to the impact and the shock made trace elements including REEs and U-Pb equilibrated.

  11. Experimental simulation of organic matter alteration in carbonaceous chondrites under an in situ micro FTIR spectroscopy

    Science.gov (United States)

    Kebukawa, Y.; Nakashima, S.; Saiki, K.; Zolensky, M. E.

    2007-12-01

    Carbonaceous chondrites contain organic matter up to a few weight percents, most of which consists of kerogen- like macromolecular material. Chondritic organic matter preserves signatures of various evolutional steps from presolar materials, through aqueous alteration and thermal metamorphism in the parent asteroid up to delivery to the Earth. The organic-mineral interactions during these processes are little known. We report here on the experimental simulation of organic matter alteration on carbonaceous chondrite parent body under micro FTIR spectroscopy with a heating stage. Leonardite humic acid (IHSS standard humic acid) and synthetic saponite or natural antigorite were used as the macromolecular organic matter and the matrix mineral. These powdered samples were dispersed by MilliQ water then dropped on a CaF2 plate and dried. They were heated in the heating stage from room temperature to 600 °C with a heating rate of 10 °C/min in air, Ar gas, and H2+CO2 gas mixture (mixing ratio 1:1). H2+CO2 gas mixture enables controls of not only oxygen fugacity but also water vapor fugacity, and aqueous processing on chondrite parent bodies can be partly simulated. IR spectra were collected at every 20 °C under the micro FTIR spectroscopy. Aliphatic C-H increased from room temperature to approximately 250 °C then decreased. Aromatic C-H increased from room temperature to around 400-450 °C then decreased. These aliphatic C-H decrease and aromatic C-H increase are faster in air than in Ar or H2+CO2. These CH changes of leonardite humic acid are slower with the presence of saponite. These results indicate that organic matter transformation might be prevented by the clay mineral (saponite). Some carbonaceous chondrite samples mixed with the organic material (leonardite humic acid) will also be investigated by the same way. These results will elucidate interactions of chondritic macromolecular organic matter with matrix minerals during parent body processes.

  12. The deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing irradiation.

    Science.gov (United States)

    Laurent, Boris; Roskosz, Mathieu; Remusat, Laurent; Robert, François; Leroux, Hugues; Vezin, Hervé; Depecker, Christophe; Nuns, Nicolas; Lefebvre, Jean-Marc

    2015-01-01

    Primitive carbonaceous chondrites contain a large array of organic compounds dominated by insoluble organic matter (IOM). A striking feature of this IOM is the systematic enrichment in deuterium compared with the solar hydrogen reservoir. This enrichment has been taken as a sign of low-temperature ion-molecule or gas-grain reactions. However, the extent to which Solar System processes, especially ionizing radiation, can affect D/H ratios is largely unknown. Here, we report the effects of electron irradiation on the hydrogen isotopic composition of organic precursors containing different functional groups. From an initial terrestrial composition, overall D-enrichments and differential intramolecular fractionations comparable with those measured in the Orgueil meteorite were induced. Therefore, ionizing radiation can quantitatively explain the deuteration of organics in some carbonaceous chondrites. For these meteorites, the precursors of the IOM may have had the same isotopic composition as the main water reservoirs of the inner Solar System. PMID:26461170

  13. Chondrites isp. Indicating Late Paleozoic Atmospheric Anoxia in Eastern Peninsular India

    Directory of Open Access Journals (Sweden)

    Biplab Bhattacharya

    2014-01-01

    Full Text Available Rhythmic sandstone-mudstone-coal succession of the Barakar Formation (early Permian manifests a transition from lower braided-fluvial to upper tide-wave influenced, estuarine setting. Monospecific assemblage of marine trace fossil Chondrites isp. in contemporaneous claystone beds in the upper Barakar succession from two Gondwana basins (namely, the Raniganj Basin and the Talchir Basin in eastern peninsular India signifies predominant marine incursion during end early Permian. Monospecific Chondrites ichnoassemblage in different sedimentary horizons in geographically wide apart (~400 km areas demarcates multiple short-spanned phases of anoxia in eastern India. Such anoxia is interpreted as intermittent falls in oxygen level in an overall decreasing atmospheric oxygenation within the late Paleozoic global oxygen-carbon dioxide fluctuations.

  14. Ion irradiation of carbonaceous chondrites as a simulation of space weathering on C-complex asteroids

    Science.gov (United States)

    Lantz, C.; Brunetto, R.; Barucci, M. A.; Bachelet, C.; Baklouti, D.; Bourçois, J.; Dartois, E.; Duprat, J.; Duret, P.; Engrand, C.; Godard, M.; Ledu, D.; Mivumbi, O.; Fornasier, S.

    2015-10-01

    We are investigating the effects of space weathering on primitive asteroids using ion irradiation on their meteoritic analogs. To do so, we exposed several carbonaceous chondrites (CV Allende, COs Lancé and Frontier Mountain 95002, CM Mighei, CI Alais, and ungrouped Tagish Lake) to 40 keV He+ ions as a simulation of solar wind irradiation using fluences up to 6.1016 ions/cm2 (implantation platform IRMA at CSNSM Orsay). As a test for our new experimental setup, we also studied samples of olivine and diopside. We confirm the reddening and darkening trends on S-type objects, but carbonaceous chondrites present a continuum of behaviors after ion irradiation as a function of the initial albedo and carbon content: from red to blue and from dark to bright.

  15. Cosmic-ray exposure and gas retention ages of the Guangmingshan (H5) chondrite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Isotopic compositions of noble gases from the Guangmingshan chondrite were analyzed. Based on the analyses of cosmogenic nuclei, cosmic-ray exposure age of the meteorite is (65± 10.0) Ma (3He), (80 ± 12) Ma (21Ne) and (65 ± 10.0) Ma (38Ar), with an average of 70 Ma. This is the highest exposure age of H-group ordinary chondrites. Gas retention ages of K-Ar and U, Th-4He are (4230±100) Ma and (3300±60) Ma, respectively. The smaller ages of 3He than 21Ne and 4He than 40Ar suggest that both 3He and 4He lost together. This is probably related to a solar heating effect of a meteorite with a small perihelion during the last exposure period.``

  16. Mineralogy and Microstructures of Shock-Induced Melt Veins in Chondrites

    Science.gov (United States)

    Sharp, Thomas G.

    2000-01-01

    The applicability of phase equilibrium data to the interpretation of shock-induced melt veins can only be tested by a detailed study of melt- vein mineralogy to see how high-pressure assemblages vary as a function of shock conditions inferred from other indicators. We have used transmission electron microscopy (TEM), analytical electron microscopy (AEM), scanning electron microscopy (SEM), electron microprobe analysis (EMA) and optical petrography to characterize the mineralogy, microstructures, and compositions of melt veins and associated high-pressure minerals in shocked chondrites and SNC meteorites. In the processes, we have gained a better understanding of what melt veining can tell us about shock conditions and we have discovered new mineral phases in chondritic and SNC meteorites.

  17. Thermal evolution and sintering of chondritic planetesimals II. Improved treatment of the compaction process

    CERN Document Server

    Gail, Hans-Peter; Trieloff, Mario

    2014-01-01

    Reconstruction of the thermal history of individual meteorites which can be assigned to the same parent body allows to derive general characteristics of the parent body, which hold important clues on the planetary formation process. This requires to construct models for the heating of such bodies by short lived radioactives, in particular by 26Al, and its cooling by heat conduction, which then are compared with the cooling histories of the meteorites. The heat conductivity of the planetesimal material depends critically on the porosity of the chondritic material and changes by sintering of the material at elevated temperatures and pressures. Compaction of a granular material is a key process for the thermal history of the parent bodies of meteorites. The modelling of the compaction process is improved by applying concepts originally developed for hot isostatic pressing in metallurgical processes. It is extended to a binary mixture of matrix and chondrules, as observed in chondrites. By comparison with publish...

  18. Titanium-rich oxide-bearing plagioclase-olivine inclusions in the unusual Ningqiang carbonaceous chondrite

    OpenAIRE

    Lin,Yangting /Kimura,Makoto

    1997-01-01

    Two plagioclase-olivine inclusions (POIs) from the unusual Ningqiang carbonaceous chondrite were studied to understand their mineralogy and crystallization history. In addition to the major phases plagioclase, spinel, olivine and pyroxene, Ningqiang POIs are characterized by interstitial assemblages composed of Ca-rich and Ca-poor pyroxenes, Ti-rich oxides and the other phases. The Ti-rich oxides include an unidentified titanium mineral series referred to as phase T, Ca-rich and Mg, Fe-rich a...

  19. Checking Contamination during Storage of Carbonaceous Chondrites for Micro FTIR Measurements

    Science.gov (United States)

    Zolensky, Michael E.

    2008-01-01

    We examined organic contamination by Fourier transform infrared micro spectroscopic (micro FTIR) measurements of carbonaceous chondrite samples. Carbonaceous chondrites, Tagish Lake (C2), Murchison (CM2) and Moss (CO3), and some mineral powder samples pressed on aluminum plates were measured by micro FTIR before and after storage in several containers with silicone rubber mat. During storage, samples did not touch directly anything except the holding aluminum plates. The carbonaceous chondrites containing hydrous minerals (Tagish Lake and Murchison) pressed on aluminum plates and measured by transmission-reflection micro FTIR measurements were found to be contaminated during storage after only one day, as revealed by an increase of approximately 2965 /cm and approximately 1260 /cm peaks. The Moss meteorite which contains no hydrous minerals, did not show an increase of these peaks, indicating no organic contamination. This difference is probably related to the differing mineralogy and physical properties (including porosity and permeability) of these chondrites. Hydrous minerals such as antigorite, muscovite, montmorillonite and silica gel showed organic contamination by the same infrared measurements, while anhydrous materials such as SiO2 and KBr showed no contamination. These results indicate importance of surface OH groups for the organic contamination. Organic contamination was found on silica gel samples pressed on aluminum plates when they were stored within containers including silicone rubber, silicone grease or adhesive tape. Long path gas cell FTIR measurements for silicone rubber indicated methylsiloxane oligomers were released from the silicone rubber. In-situ heating infrared measurements on the contaminated antigorite and Tagish Lake showed decrease of the 1262 /cm (Si-CH3) and 2963 /cm (CH3) peaks from room temperature to 200-300 C indicating desorption of volatile contaminants. These results indicate that careful preparation and storage are

  20. In Situ Mapping of the Organic Matter in Carbonaceous Chondrites and Mineral Relationships

    Science.gov (United States)

    Clemett, Simon J.; Messenger, S.; Thomas-Keprta, K. L.; Ross, D. K.

    2012-01-01

    Carbonaceous chondrite organic matter represents a fossil record of reactions that occurred in a range of physically, spatially and temporally distinct environments, from the interstellar medium to asteroid parent bodies. While bulk chemical analysis has provided a detailed view of the nature and diversity of this organic matter, almost nothing is known about its spatial distribution and mineralogical relationships. Such information is nevertheless critical to deciphering its formation processes and evolutionary history.

  1. Proto-Planetary Disk Chemistry Recorded by D-Rich Organic Radicals in Carbonaceous Chondrites

    OpenAIRE

    Remusat, Laurent; Robert, François; Meibom, Anders; Mostefaoui, Smail; Delpoux, Olivier; Binet, Laurent; Gourier, Didier; Derenne, Sylvie

    2009-01-01

    Insoluble organic matter (IOM) in primitive carbonaceous meteorites has preserved its chemical composition and isotopic heterogeneity since the solar system formed ~4.567 billion years ago. We have identified the carrier moieties of isotopically anomalous hydrogen in IOM isolated from the Orgueil carbonaceous chondrite. Data from high spatial resolution, quantitative isotopic NanoSIMS mapping of Orgueil IOM combined with data from electron paramagnetic resonance spectroscopy reveals that orga...

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

    Science.gov (United States)

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

    2011-01-01

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

  3. The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

    Science.gov (United States)

    Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

    2016-06-01

    The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate

  4. Nebular dead zone effects on the D/H ratio in chondrites and comets

    CERN Document Server

    Ali-Dib, Mohamad; Petit, Jean-Marc; Mousis, Olivier; Vernazza, Pierre; Lunine, Jonathan I

    2015-01-01

    Comets and chondrites show non-monotonic behaviour of their Deuterium to Hydrogen (D/H) ratio as a function of their formation location from the Sun. This is difficult to explain with a classical protoplanetary disk model that has a decreasing temperature structure with radius from the Sun. We want to understand if a protoplanetary disc with a dead zone, a region of zero or low turbulence, can explain the measured D/H values in comets and chondrites. We use time snapshots of a vertically layered disk model with turbulent surface layers and a dead zone at the midplane. The disc has a non-monotonic temperature structure due to increased heating from self-gravity in the outer parts of the dead zone. We couple this to a D/H ratio evolution model in order to quantify the effect of such thermal profiles on D/H enrichment in the nebula. We find that the local temperature peak in the disk can explain the diversity in the D/H ratios of different chondritic families. This disk temperature profile leads to a non-monoton...

  5. The Spatial Distribution of Organic Matter and Mineralogical Relationships in Carbonaceous Chondrites

    Science.gov (United States)

    Clemett, S. J.; Messenger, S.; Thomas-Keprta, K. L.; Nakamura-Messenger, K.

    2012-01-01

    Organic matter present within primitive carbonaceous meteorites represents the complex conglomeration of species formed in a variety of physically and temporally distinct environments including circumstellar space, the interstellar medium, the Solar Nebula & Jovian sub-nebulae and asteroids. In each case, multiple chemical pathways would have been available for the synthesis of organic molecules. Consequently these meteorites constitute a unique record of organic chemical evolution in the Universe and one of the biggest challenges in organic cosmochemistry has been in deciphering this record. While bulk chemical analysis has provided a detailed description of the range and diversity of organic species present in carbonaceous chondrites, there is virtually no hard experimental data as to how these species are spatially distributed and their relationship to the host mineral matrix, (with one exception). The distribution of organic phases is nevertheless critical to understanding parent body processes. The CM and CI chondrites all display evidence of low temperature (organics and synthesis of new organics coupled to aqueous mineral alteration. To address such issues we have applied the technique of microprobe two-step laser desorption / photoionization mass spectrometry (L2MS) to map in situ the spatial distribution of a broad range of organic species at the micron scale in the freshly exposed matrices of the Bells, Tagish Lake and Murchison (CM2) carbonaceous chondrites.

  6. The Effect of Aqueous Alteration in Antarctic Carbonaceous Chondrites from Comparative ICP-MS Bulk Chemistry

    Science.gov (United States)

    Alonso-Azcarate, J.; Trigo-Rodriguez, J. M.; Moyano-Cambero, C. E.; Zolensky, M.

    2014-01-01

    Terrestrial ages of Antarctic carbonaceous chondrites (CC) indicate that these meteorites have been preserved in or on ice for, at least, tens of thousands of years. Due to the porous structure of these chondrites formed by the aggregation of silicate-rich chondrules, refractory inclusions, metal grains, and fine-grained matrix materials, the effect of pervasive terrestrial water is relevant. Our community defends that pristine CC matrices are representing samples of scarcely processed protoplanetary disk materials as they contain stellar grains, but they might also trace parent body processes. It is important to study the effects of terrestrial aqueous alteration in promoting bulk chemistry changes, and creating distinctive alteration minerals. Particularly because it is thought that aqueous alteration has particularly played a key role in some CC groups in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive. With the goal to learn more about terrestrial alteration in Antarctica we are obtaining reflectance spectra of CCs, but also performing ICP-MS bulk chemistry of the different CC groups. A direct comparison with the mean bulk elemental composition of recovered falls might inform us on the effects of terrestrial alteration in finds. With such a goal, in the current work we have analyzed some members representative of CO and CM chondrite groups.

  7. Phosphate control on the Th/U variations in ordinary chondrites: Improving solar system abundances

    Science.gov (United States)

    Goreva, J. S.; Burnett, D. S.

    2001-01-01

    Isotope dilution thorium and uranium analyses by inductively-coupled plasma mass spectrometry of 12 samples of Harleton (L6) show a much larger scatter than was previously observed in equilibrated ordinary chondrites. Th/U linearly correlates with 1/U in Harleton and in the total equilibrated ordinary chondrite data set as well. Such a correlation suggests a two component mixture and this trend can be quantitatively modeled as reflecting variations in the mixing ratio between two phosphate phases: chlorapatite and merrillite. The major effect is due to apatite variations, which strongly control the whole rock U concentrations. Phosphorous variations will tend to destroy the Th/U vs. 1/U correlation, and measured P concentrations on exactly the same samples as U and Th show a factor of 3 range. It appears that the P variations are compensated by inverse variations in U (a dilution effect) to preserve the Th/U vs. 1/U correlation. Because variations in whole rock Th/U are consequences of phosphate sampling, a weighted average of high accuracy Th/U measurements in equilibrated ordinary chondrites should converge to a significantly improved average solar system Th/U. Our best estimate of this ratio is 3.53 with ?mean = 0.10.

  8. Presolar diamond, silicon carbide, and graphite in carbonaceous chondrites: implications for thermal processing in the solar nebula

    Science.gov (United States)

    Huss, Gary R.; Meshik, Alex P.; Smith, Julie B.; Hohenberg, C. M.

    2003-12-01

    We have determined abundances of presolar diamond, silicon carbide, graphite, and Xe-P1 (Q-Xe) in eight carbonaceous chondrites by measuring the abundances of noble gas tracers in acid residues. The meteorites studied were Murchison (CM2), Murray (CM2), Renazzo (CR2), ALHA77307 (CO3.0), Colony (CO3.0), Mokoia (CV3 ox), Axtell (CV3 ox), and Acfer 214 (CH). These data and data obtained previously by Huss and Lewis (1995) provide the first reasonably comprehensive database of presolar-grain abundances in carbonaceous chondrites. Evidence is presented for a currently unrecognized Ne-E(H) carrier in CI and CM2 chondrites. After accounting for parent-body metamorphism, abundances and characteristics of presolar components still show large variations across the classes of carbonaceous chondrites. These variations correlate with the bulk compositions of the host meteorites and imply that the same thermal processing that was responsible for generating the compositional differences between the various chondrite groups also modified the initial presolar-grain assemblages. The CI chondrites and CM2 matrix have the least fractionated bulk compositions relative to the sun and the highest abundances of most types of presolar material, particularly the most fragile types, and thus are probably most representative of the material inherited from the sun's parent molecular cloud. The other classes can be understood as the products of various degrees of heating of bulk molecular cloud material in the solar nebula, removing the volatile elements and destroying the most fragile presolar components, followed by chondrule formation, metal-silicate fractionation in some cases, further nebula processing in some cases, accretion, and parent body processing. If the bulk compositions and the characteristics of the presolar-grain assemblages in various chondrite classes reflect the same processes, as seems likely, then differential condensation from a nebula of solar composition is ruled out as

  9. Origins and Asteroid Main-Belt Stratigraphy for H-, L-, LL-Chondrite Meteorites

    Science.gov (United States)

    Binzel, Richard; DeMeo, Francesca; Burbine, Thomas; Polishook, David; Birlan, Mirel

    2016-10-01

    We trace the origins of ordinary chondrite meteorites to their main-belt sources using their (presumably) larger counterparts observable as near-Earth asteroids (NEAs). We find the ordinary chondrite stratigraphy in the main belt to be LL, H, L (increasing distance from the Sun). We derive this result using spectral information from more than 1000 near-Earth asteroids [1]. Our methodology is to correlate each NEA's main-belt source region [2] with its modeled mineralogy [3]. We find LL chondrites predominantly originate from the inner edge of the asteroid belt (nu6 region at 2.1 AU), H chondrites from the 3:1 resonance region (2.5 AU), and the L chondrites from the outer belt 5:2 resonance region (2.8 AU). Each of these source regions has been cited by previous researchers [e.g. 4, 5, 6], but this work uses an independent methodology that simultaneously solves for the LL, H, L stratigraphy. We seek feedback from the planetary origins and meteoritical communities on the viability or implications of this stratrigraphy.Methodology: Spectroscopic and taxonomic data are from the NASA IRTF MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) [1]. For each near-Earth asteroid, we use the Bottke source model [2] to assign a probability that the object is derived from five different main-belt source regions. For each spectrum, we apply the Shkuratov model [3] for radiative transfer within compositional mixing to derive estimates for the ol / (ol+px) ratio (and its uncertainty). The Bottke source region model [2] and the Shkuratov mineralogic model [3] each deliver a probability distribution. For each NEA, we convolve its source region probability distribution with its meteorite class distribution to yield a likelihood for where that class originates. Acknowledgements: This work supported by the National Science Foundation Grant 0907766 and NASA Grant NNX10AG27G.References: [1] Binzel et al. (2005), LPSC XXXVI, 36.1817. [2] Bottke et al. (2002). Icarus 156, 399. [3

  10. Multivariate Statistical Analysis of Volatile Trace Elements in H Chondrites: Implications for Parent Body Structure

    Science.gov (United States)

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

    1993-07-01

    The perception among meteoriticists is that contents of the volatile trace elements systematically decrease with shock and particularly petrologic type. This perception affects views that investigators have of the early history and structure of the H chondrite parent body. Measurement of a variety of volatile trace elements in a statistically significant number of samples accompanied by chemometric data analysis techniques developed for interpretation of trace- element data [1] should maximize the amount of genetic information available from the volatile trace elements and offer clues to the early thermal history of the H chondrite parent body. Volatile trace-element data exist for 58 H chondrite falls: the complete dataset includes Co, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, and In (listed in increasing order of volatility) [2,3]. This dataset includes 13 H4, 32 H5, and 13 H6 chondrites, which cover the full range of shock facies from a through f. To examine the effect that shock has on volatile trace-element concentrations in H4-6 chondrites, we have compared data for the least-shocked samples (shock facies a-b) with the most shocked samples (shock facies c-f) using both univariate (Student's t-test) and multivariate techniques (linear discriminant analysis). The results demonstrate no reason to doubt the null hypothesis of no difference in volatile trace-element composition between shocked and unshocked H4-6 chondrites at any reasonable significance level. This situation contrasts sharply with the strong difference found between shocked and unshocked L chondrites [4]. The role of shock in establishing volatile trace- element contents in H and L chondrites clearly differs. Univariate comparisons between H4, H5, and H6 chondrites demonstrate that only Cs varies significantly with petrologic type (prob. > F 0.0006) with concentration decreasing monotonically with increasing petrographic type. Box- and-whisker plots of volatile trace-element contents reveal a general

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

    Science.gov (United States)

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

    2007-09-01

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

  12. Highly 15N-Enriched Chondritic Clasts in the Isheyevo Meteorite

    Energy Technology Data Exchange (ETDEWEB)

    Bonal, L; Huss, G R; Krot, A N; Nagashima, K; Ishii, H A; Bradley, J P; Hutcheon, I D

    2009-01-14

    The metal-rich carbonaceous chondrites (CB and CH) have the highest whole-rock {sup 15}N enrichment ({delta}{sup 15}N up to +1500{per_thousand}), similar to {delta}{sup 15}N values reported in micron-sized regions (hotspots) of Interplanetary Dust Particles (IDPs) of possibly cometary origin and fine-grained matrices of unmetamorphosed chondrites. These {sup 15}N-rich hotspots are commonly attributed to low-temperature ion-molecule reactions in the protosolar molecular cloud or in the outer part of the protoplanetary disk. The nature of the whole-rock {sup 15}N enrichment of the metal-rich chondrites is not understood. We report a discovery of a unique type of primitive chondritic clasts in the CH/CB-like meteorite Isheyevo, which provides important constraints on the origin of {sup 15}N anomaly in metal-rich chondrites and nitrogen-isotope fractionation in the Solar System. These clasts contain tiny chondrules and refractory inclusions (5-15 {micro}m in size), and abundant ferromagnesian chondrule fragments (1-50 {micro}m in size) embedded in the partly hydrated, fine-grained matrix material composed of olivines, pyroxenes, poorly-organized aromatic organics, phyllosilicates and other hydrous phases. The mineralogy and oxygen isotope compositions of chondrules and refractory inclusions in the clasts are similar to those in the Isheyevo host, suggesting formation at similar heliocentric distances. In contrast to the previously known extraterrestrial samples, the fine-grained material in the clasts is highly and rather uniformly enriched in {sup 15}N, with bulk {delta}{sup 15}N values ranging between +1000 and +1300{per_thousand}; the {delta}{sup 15}N values in rare hotspots range from +1400 to +4000{per_thousand}. Since fine-grained matrices in the lithic clasts are the only component containing thermally unprocessed (during CAI and chondrule formation or during impact melting) materials that accreted into the metal rich chondrite parent body(ies), the {sup 15}N

  13. Rhenium-osmium systematics of calcium-aluminium-rich inclusions in carbonaceous chondrites

    Science.gov (United States)

    Becker, H.; Morgan, J.W.; Walker, R.J.; MacPherson, G.J.; Grossman, J.N.

    2001-01-01

    The Re-Os isotopic systematics of calcium-aluminium-rich inclusions (CAIs) in chondrites were investigated in order to shed light on the behavior of the Re-Os system in bulk chondrites, and to constrain the timing of chemical fractionation in primitive chondrites. CAIs with relatively unfractionated rare earth element (REE) patterns (groups I, III, V, VI) define a narrow range of 187Re/188Os (0.3764-0.4443) and 187Os/188Os (0.12599-0.12717), and high but variable Re and Os abundances (3209-41,820 ppb Os). In contrast, CAIs that show depletions in highly refractory elements and strongly fractionated REE patterns (group II) also show a much larger range in 187Re/188Os (0.409-0.535) and 187Os/188Os (0.12695-0.13770), and greater than an order of magnitude lower Re and Os abundances than other groups (e.g., 75.7-680.2 ppb Os). Sixteen bulk CAIs and CAI splits plot within analytical uncertainty of a 4558 Ga reference isochron, as is expected for materials of this antiquity. Eight samples, however, plot off the isochron. Several possible reasons for these deviations are discussed. Data for multiple splits of one CAI indicate that the nonisochronous behavior for at least this CAI is the result of Re-Os reequilibration at approximately 1.6 Ga. Thus, the most likely explanation for the deviations of most of the nonisochronous CAIs is late-stage open-system behavior of Re and Os in the asteroidal environment. The 187Os/188Os-Os systematics of CAIs are consistent with previous models that indicate group II CAIs are mixtures of components that lost the bulk of their highly refractory elements in a previous condensation event and a minor second component that provided refractory elements at chondritic relative proportions. The high Re/Os of group II CAIs relative to other CAIs and chondrite bulk rocks may have been caused by variable mobilization of Re and Os during medium- to low-temperature parent body alteration ??4.5 Ga ago. This model is favored over nebular models, which

  14. Asteroid 6 Hebe: The probable parent body of the H-Type ordinary chondrites and the IIE iron meteorites

    Science.gov (United States)

    Gaffey, Michael J.; Gilbert, Sarah L.

    1998-11-01

    The S(IV)-type asteroid 6 Hebe is identified as the probable parent body of the H-type ordinary chondrites and of the IIE iron meteorites. The ordinary chondrites are the most common type of meteorites falling to Earth, but prior to the present study no large mainbelt source bodies have been confirmed. Hebe is located adjacent to both the (6 and 3:1 resonances, and has been previously suggested as a major potential source of the terrestrial meteorite flux. Hebe exhibits subtle rotational spectral variations indicating the presence of some compositional variations across its surface. The silicate portion of the surface assemblage of Hebe is consistent, both in overall average and in its range of variation, with the silicate components in the suite of H-type chondrites. The high albedo of Hebe rules out a lunar-style space weathering process to produce the weakened absorption features and reddish spectral slope in the S-type spectrum of Hebe. Linear unmixing models show that a typical nickel-iron metal spectrum is consistent with the component which modifies an H-chondrite spectrum to produce the S-type spectrum of Hebe. Based on the association between the H chondrites and the IIE iron meteorites, our model suggests that large impacts onto the relatively metal-rich H chondrite target produced melt bodies (sheets or pods) which differentiated to form thin, laterally extensive near-surface layers of NiFe metal. Fragments of the upper silicate portions of these melt bodies are apparently represented by some of the igneous inclusions in H-chondrite breccias. Alternately, masses of metal could have been deposited on the surface of Hebe by the impact of a core or core fragment from a differentiated parent body of H chondrite composition. Subsequent impacts preferentially eroded and depleted the overlying silicate and regolith components exposing and maintaining large masses of metal at the optical surface of Hebe. In this interpretation, the nonmagmatic IIE iron

  15. Refractory Inclusion Size Distribution and Fabric Measured in a Large Slab of the Allende CV3 Chondrite

    Science.gov (United States)

    Srinivasan, P.; Simon, Justin I.; Cuzzi, J. N.

    2013-01-01

    Aggregate textures of chondrites reflect accretion of early-formed particles in the solar nebula. Explanations for the size and density variations of particle populations found among chondrites are debated. Differences could have risen out of formation in different locations in the nebula, and/or they could have been caused by a sorting process [1]. Many ideas on the cause of chondrule sorting have been proposed; some including sorting by mass [2,3], by X-winds [4], turbulent concentration [5], and by photophoresis [6]. However, few similar studies have been conducted for Ca-, Al-rich inclusions (CAIs). These particles are known to have formed early, and their distribution could attest to the early stages of Solar System (ESS) history. Unfortunately, CAIs are not as common in chondrites as chondrules are, reducing the usefulness of studies restricted to a few thin sections. Furthermore, the largest sizes of CAIs are generally much larger than chondrules, and therefore rarely present in most studied chondrite thin sections. This study attempts to perform a more representative sampling of the CAI population in the Allende chondrite by investigating a two decimeter-sized slab.

  16. Ca-, Al-rich Inclusions in Three New Carbonaceous Chondrites from the Grove Mountains, Antarctica:New Evidence for a Similar Origin of the Objects in Various Groups of Chondrites

    Institute of Scientific and Technical Information of China (English)

    DAI Deqiu; LIN Yangting; MIAO Bingkui; SHENG Wenjie; WANG Daode

    2004-01-01

    Three new carbonaceous chondrites (GRV 020025, 021579 and 022459) collected from the Grove Mountains(GRV), Antarctica, have been classified as the CM2, CO3 and CV3 chondrites, respectively. A total of 27 Ca- and Al-rich inclusions have been found in the three meteorites, which are the earliest assemblages formed in the solar nebula. Most of the inclusions are intensively altered, with abundant phyllosilicates in the inclusions from GRV 020025 and FeO enrichment of spinel in those from GRV 022459. Except for one spinel-spherule in each of GRV 020025 and 021579, all the inclusions can be classified as Type A-like or spinel-pyroxene-rich inclusions, and they probably represent the continuum of solar nebular condensation. In addition, most of the inclusions in these meteorites share much similarity in both petrography and mineral chemistry, suggesting a similar origin of Ca-Al-rich inclusions in various chondrites.

  17. Magnesium and 54Cr isotope compositions of carbonaceous chondrite chondrules – Insights into early disk processes

    Science.gov (United States)

    Olsen, Mia B.; Wielandt, Daniel; Schiller, Martin; Van Kooten, Elishevah M.M.E.; Bizzarro, Martin

    2016-01-01

    We report on the petrology, magnesium isotopes and mass-independent 54Cr/52Cr compositions (μ54Cr) of 42 chondrules from CV (Vigarano and NWA 3118) and CR (NWA 6043, NWA 801 and LAP 02342) chondrites. All sampled chondrules are classified as type IA or type IAB, have low 27Al/24Mg ratios (0.04–0.27) and display little or no evidence for secondary alteration processes. The CV and CR chondrules show variable 25Mg/24Mg and 26Mg/24Mg values corresponding to a range of mass-dependent fractionation of ~500 ppm (parts per million) per atomic mass unit. This mass-dependent Mg isotope fractionation is interpreted as reflecting Mg isotope heterogeneity of the chondrule precursors and not the result of secondary alteration or volatility-controlled processes during chondrule formation. The CV and CR chondrule populations studied here are characterized by systematic deficits in the mass-independent component of 26Mg (μ26Mg*) relative to the solar value defined by CI chondrites, which we interpret as reflecting formation from precursor material with a reduced initial abundance of 26Al compared to the canonical 26Al/27Al of ~5 × 10−5. Model initial 26Al/27Al values of CV and CR chondrules vary from (1.5 ± 4.0) × 10−6 to (2.2 ± 0.4) × 10−5. The CV chondrules display significant μ54Cr variability, defining a range of compositions that is comparable to that observed for inner Solar System primitive and differentiated meteorites. In contrast, CR chondrites are characterized by a narrower range of μ54Cr values restricted to compositions typically observed for bulk carbonaceous chondrites. Collectively, these observations suggest that the CV chondrules formed from precursors that originated in various regions of the protoplanetary disk and were then transported to the accretion region of the CV parent asteroid whereas CR chondrule predominantly formed from precursor with carbonaceous chondrite-like μ54Cr signatures. The observed μ54Cr variability in chondrules from

  18. Magnesium and 54Cr isotope compositions of carbonaceous chondrite chondrules - Insights into early disk processes

    Science.gov (United States)

    Olsen, Mia B.; Wielandt, Daniel; Schiller, Martin; Van Kooten, Elishevah M. M. E.; Bizzarro, Martin

    2016-10-01

    We report on the petrology, magnesium isotopes and mass-independent 54Cr/52Cr compositions (μ54Cr) of 42 chondrules from CV (Vigarano and NWA 3118) and CR (NWA 6043, NWA 801 and LAP 02342) chondrites. All sampled chondrules are classified as type IA or type IAB, have low 27Al/24Mg ratios (0.04-0.27) and display little or no evidence for secondary alteration processes. The CV and CR chondrules show variable 25Mg/24Mg and 26Mg/24Mg values corresponding to a range of mass-dependent fractionation of ∼500 ppm (parts per million) per atomic mass unit. This mass-dependent Mg isotope fractionation is interpreted as reflecting Mg isotope heterogeneity of the chondrule precursors and not the result of secondary alteration or volatility-controlled processes during chondrule formation. The CV and CR chondrule populations studied here are characterized by systematic deficits in the mass-independent component of 26Mg (μ26Mg∗) relative to the solar value defined by CI chondrites, which we interpret as reflecting formation from precursor material with a reduced initial abundance of 26Al compared to the canonical 26Al/27Al of ∼5 × 10-5. Model initial 26Al/27Al values of CV and CR chondrules vary from (1.5 ± 4.0) × 10-6 to (2.2 ± 0.4) × 10-5. The CV chondrules display significant μ54Cr variability, defining a range of compositions that is comparable to that observed for inner Solar System primitive and differentiated meteorites. In contrast, CR chondrites are characterized by a narrower range of μ54Cr values restricted to compositions typically observed for bulk carbonaceous chondrites. Collectively, these observations suggest that the CV chondrules formed from precursors that originated in various regions of the protoplanetary disk and were then transported to the accretion region of the CV parent asteroid whereas CR chondrule predominantly formed from precursor with carbonaceous chondrite-like μ54Cr signatures. The observed μ54Cr variability in chondrules from CV

  19. Petrologic evolution of CM chondrites: The difficulty of discriminating between nebular and parent-body effects

    Science.gov (United States)

    Kerridge, J. F.; McSween, H. Y., Jr.; Bunch, T. E.

    1994-07-01

    We wish to draw attention to a major controversy that has arisen in the area of CM-chondrite petrology. The problem is important because its resolution will have profound implications for ideas concerning nebular dynamics, gas-solid interactions in the nebula, and accretionary processes in the nebula, among other issues. On the one hand, cogent arguments have been presented that 'accretionary dust mantles,' were formed in the solar nebula prior to accretion of the CM parent asteroid(s). On the other hand, no-less-powerful arguments have been advanced that a significant fraction of the CM lithology is secondary, produced by aqueous alteration in the near-surface regions of an asteroid-sized object. Because most, if not all, CM chondrites are breccias, these two views could coexist harmoniously, were it not for the fact that some of the coarse-grained lithologies surrounded by 'accretion dust mantles' are themselves of apparently secondary origin. Such an observation must clearly force a reassessment of one or both of the present schools of thought. Our objective here is to stimulate such a reassessment. Four possible resolutions of this conflict may be postulated. First, perhaps nature found a way of permitting such secondary alteration to take place in the nebula. Second, maybe dust mantles could form in a regolith, rather than a nebular, environment. Third, it is possible that dust mantles around secondary lithologies are different from those around primary lithologies. Finally, perhaps formation of CM chondrites involved a more complex sequence of events than visualized so far, so that some apparently 'primary' processes postdated certain 'secondary' processes.

  20. HRTEM and EFTEM Observations of Matrix in the Oxidized CV3 Chondrite ALH 84028: Implications for the Origins of Matrix Olivines

    Science.gov (United States)

    Abreu, Neyda M.; Brearley, Adrian J.

    2003-01-01

    The determination of the nature, distribution, and origin of organic material in carbonaceous chondrites is fundamental to understanding early solar nebular conditions and the origin of life. Using a variety of extraction techniques, followed by detailed chemical analysis, an extensive suite of organic compounds has been identified in carbonaceous chondrites. These data have provided key information on the diversity and isotopic composition of the organic component in chondrites. However, one disadvantage of extraction techniques is that all information regarding the spatial distribution of the organics on a fine scale is lost. This is especially important for the insoluble macromolecular carbon, which constitutes approximately 70% of the carbon in carbonaceous chondrites such as Murchison. The distribution and mineralogical associations may provide important constraints on the possible origins of the carbonaceous material. Our previous studies of the CV3 chondrites Allende and Vigarano have demonstrated that energy filtered transmission electron microscopy (EFTEM), combined with high resolution TEM (HRTEM) are powerful tools for the in situ characterization of insoluble organic matter in carbonaceous chondrites. In this study, we have used SEM and TEM techniques to characterize the matrix mineralogy of the CV3 chondrite ALH 84028 and examine the distribution and mineralogical associations of carbon. We are especially interested in establishing whether the occurrence of poorly graphitized carbon (PGC), observed in Allende matrix olivines, is common to all oxidized CV3 chondrites or is a unique feature of Allende.

  1. Exposure ages and radiogenic ages of ureilite(GRV 024516) and ordinary chondrite(GRV 024517) from Antarctica

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The GRV 024516 and GRV 024517 meteorite samples collected from Grove Montains,Antactica are ureilite and H5 ordinary chondrite,respectively.Based on the study of mineralogy-petrology ,the cosmic-ray exposure ages and gas retention ages of these two meteorites were determinated and calculated.Their cosmic-ray exposure ages are 33.3 Ma ,51.7 Ma,and gas retention ages are 1936.8 Ma and 3720 Ma,respectively.The ureilite contains diamond,graphite and amorphous C,which are mainly carrier of noble gases indicating obviously shock metamorphism effects,which induced 40Ar partial loss. The H5 chondrite indicates thermal metamorphism of parent body,its gas retention age fall the range between 3220 Ma and 4510 Ma of the least shocked H5 chondrites.

  2. High-pressure phases in shock-induced melt of the unique highly shocked LL6 chondrite Northwest Africa 757

    Science.gov (United States)

    Hu, Jinping; Sharp, Thomas G.

    2016-07-01

    Northwest Africa 757 is unique in the LL chondrite group because of its abundant shock-induced melt and high-pressure minerals. Olivine fragments entrained in the melt transform partially and completely into ringwoodite. Plagioclase and Ca-phosphate transform to maskelynite, lingunite, and tuite. Two distinct shock-melt crystallization assemblages were studied by FIB-TEM analysis. The first melt assemblage, which includes majoritic garnet, ringwoodite plus magnetite-magnesiowüstite, crystallized at pressures of 20-25 GPa. The other melt assemblage, which consists of clinopyroxene and wadsleyite, solidified at ~15 GPa, suggesting a second veining event under lower pressure conditions. These shock features are similar to those in S6 L chondrites and indicate that NWA 757 experienced an intense impact event, comparable to the impact event that disrupted the L chondrite parent body at 470 Ma.

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

    Digital Repository Service at National Institute of Oceanography (India)

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

    evidence of evolved asteroids, similar to chondritic or achondritic parent bodies (e.g., Taylor et al., 2007; Genge et al., 2008; Gounelle et al., 2009; Badjukov et al., 2010; Cordier et al., 2011a, b, 2012; Suavet et al., 2010; Van Ginneken et al., 2012... is much less (Taylor et al., 2000; Yada et al., 2004; Prasad et al., 2013). They are expected to have sampled a wide variety of parent bodies, including those known to us through meteorite studies, and some that have not yet been sampled (Brownlee...

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

    Duba, AL

    1987-01-01

    Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.

  6. Powder X-Ray Diffraction of the Grain Components of Carbonaceous Chondrite Meteorites.

    Science.gov (United States)

    Furton, D. G.; Hurt, Kendra; Bos, Abram

    Carbonaceous chondrite meteorites are thought to bring to Earth samples of primordial interstellar material. Detailed chemical analysis of meteorites representative of this class (i.e., Allende, Murchison, and Orgueil) establish the primordial character of the material they include and, among other things, reveal that nanometer-sized diamond grains are present in the carbonaceous component of these meteorites at about the 1,000 ppm level (Lewis et al. 1987, Nature, 326, 160). The high abundance of nanodiamonds in these meteoritic samples contributes to the hypothesis that nanodiamonds are present in the interstellar medium at relatively high abundance, but direct observational support of this hypothesis is not so conclusive. (It may also be, according to Dai et al. (2002, Nature, 418, 157), that the nanodiamond grains were formed in situ). On the other hand, there is a growing body of observational evidence that indicates nanometer-sized silicon grains are present in the interstellar medium at relatively high abundance (e.g., Smith & Witt 2001, ApJ, 565, 304). But, silicon nanoparticles have yet to be discovered in a sample of carbonaceous chondrite meteorite. It is relevant in this context that the chemical process that has been used to extract nanodiamond grains from meteoritic samples involves dissolving in strong acid the silicate component of the meteorite. The process is ultimately destructive to any silicon grains that may be present and possibly even alters the nanodiamonds it is used to extract (Mutschke et al. 1995, ApJL, 454, L160). There does not appear to be a similar chemical process that could be used to extract silicon nanoparticles from meteoritic samples. We are in the process of establishing to what extent powder X-ray diffraction can be use as a non-destructive analytical tool to examine nanometer-sized grain components of carbonaceous chondrite meteorites. We present powder X-ray diffraction patterns obtained from samples of the Murchison and

  7. The magnetic effects of brecciation and shock in meteorites. I - The LL-chondrites

    Science.gov (United States)

    Brecher, A.; Stein, J.; Fuhrman, M.

    1977-01-01

    The magnetic behavior of eight LL chondrites is analyzed in detail, and some implications for their modes of formation and evolutionary history are examined. Petrographic features of the specimens are described, and their initial magnetic characteristics are discussed. The demagnetization behavior of the initial magnetization is investigated along with the saturation remanence behavior and paleomagnetic-field intensities. The results indicate that a magnetic field of 0.01 to 0.1 Oe may have been present during postimpact cooling and that severe shock metamorphism may have given rise to the observed magnetic moments and behavior, even in the absence of ambient magnetic fields.

  8. The Gao-Guenie impact melt breccia—Sampling a rapidly cooled impact melt dike on an H chondrite asteroid?

    Science.gov (United States)

    Schmieder, Martin; Kring, David A.; Swindle, Timothy D.; Bond, Jade C.; Moore, Carleton B.

    2016-06-01

    The Gao-Guenie H5 chondrite that fell on Burkina Faso (March 1960) has portions that were impact-melted on an H chondrite asteroid at ~300 Ma and, through later impact events in space, sent into an Earth-crossing orbit. This article presents a petrographic and electron microprobe analysis of a representative sample of the Gao-Guenie impact melt breccia consisting of a chondritic clast domain, quenched melt in contact with chondritic clasts, and an igneous-textured impact melt domain. Olivine is predominantly Fo80-82. The clast domain contains low-Ca pyroxene. Impact melt-grown pyroxene is commonly zoned from low-Ca pyroxene in cores to pigeonite and augite in rims. Metal-troilite orbs in the impact melt domain measure up to ~2 mm across. The cores of metal orbs in the impact melt domain contain ~7.9 wt% of Ni and are typically surrounded by taenite and Ni-rich troilite. The metallography of metal-troilite droplets suggest a stage I cooling rate of order 10 °C s-1 for the superheated impact melt. The subsolidus stage II cooling rate for the impact melt breccia could not be determined directly, but was presumably fast. An analogy between the Ni rim gradients in metal of the Gao-Guenie impact melt breccia and the impact-melted H6 chondrite Orvinio suggests similar cooling rates, probably on the order of ~5000-40,000 °C yr-1. A simple model of conductive heat transfer shows that the Gao-Guenie impact melt breccia may have formed in a melt injection dike ~0.5-5 m in width, generated during a sizeable impact event on the H chondrite parent asteroid.

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

    Science.gov (United States)

    Ruzicka, Alex; Hugo, Richard; Hutson, Melinda

    2015-08-01

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

  10. Whole‐rock 26Al‐26Mg systematics of amoeboid olivine aggregates from the oxidized CV3 carbonaceous chondrite Allende

    DEFF Research Database (Denmark)

    Olsen, Mia Bjørg Stolberg; Krot, Alexander N.; Larsen, Kirsten K.;

    2011-01-01

    Abstract– We report on mineralogy, petrography, and whole-rock 26Al-26Mg systematics of eight amoeboid olivine aggregates (AOAs) from the oxidized CV chondrite Allende. The AOAs consist of forsteritic olivine, opaque nodules, and variable amounts of Ca,Al-rich inclusions (CAIs) of different types....... (2008). In contrast, whole-rock 26Al-26Mg isotope systematics of CAIs and AOAs from the reduced CV chondrite Efremovka define a single isochron with a slope of (5.25± 0.01) × 10−5 (Larsen et al. 2011). We infer that the excesses in 26Mg* present in Allende AOAs are due to their late-stage open...

  11. Uranium-lead Isotope Evidence in the Shelyabinsk LL5 Chondrite Meteorite for Ancient and Recent Thermal Events

    Science.gov (United States)

    Lapen, T. J.; Kring, D. A.; Zolensky, M. E.; Andreasen, R.; Righter, M.; Swindle, T. D.; Beard, S. P.; Swindle, T. D.

    2014-01-01

    The impact histories on chondrite parent bodies can be deduced from thermochronologic analyses of materials and isotope systems with distinct apparent closure temperatures. It is especially critical to better understand the geological histories and physical properties of potenally hazardous near-Earth asteroids. Chelyabinsk is an LL5 chondrite meteorite that was dispersed over a wide area tens of kilometers south of the town of Chelyabinsk, Russia by an explosion at an altitude of 27 km at 3:22 UT on 15 Feb 2013 [1,2]. The explosion resulted in significant damage to surrounding areas and over 1500 injuries along with meteorite fragments being spread over a wide area [1].

  12. Early history of Earth's crust-mantle system inferred from hafnium isotopes in chondrites

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Haack, Henning; Rosing, M.;

    2003-01-01

    The Lu to Hf decay series has been widely used to understand the nature of Earth's early crust-mantle system. The interpretation, however, of Lu-Hf isotope data requires accurate knowledge of the radioactive decay constant of Lu (¿176), as well as bulk-Earth reference parameters. A recent...... calibration of the ¿176 value calls for the presence of highly unradiogenic hafnium in terrestrial zircons with ages greater than 3.9 Gyr, implying widespread continental crust extraction from an isotopically enriched mantle source more than 4.3 Gyr ago, but does not provide evidence for a complementary...... depleted mantle reservoir. Here we report Lu-Hf isotope measurements of different Solar System objects including chondrites and basaltic eucrites. The chondrites define a Lu-Hf isochron with an initial Hf/Hf ratio of 0.279628 ± 0.000047, corresponding to ¿176 = 1.983 ± 0.033 x 10yr using an age of 4.56 Gyr...

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

    CERN Document Server

    Moyano-Cambero, Carles E; Llorca, Jordi; Fornasier, Sonia; Barucci, Maria A; Rimola, Albert

    2016-01-01

    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 to 2.2 {\\mu}m) and in the mid-infrared to thermal infrared (2.5 to 30.0 {\\mu}m 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 studi...

  14. The Chromium Isotopic Composition of the Ungrouped Carbonaceous Chondrite Tagish Lake

    Science.gov (United States)

    Petitat, M.; Birck, J.-L.; Luu, T. H.; Gounelle, M.

    2011-07-01

    Early solar materials bear a variety of isotopic anomalies that reflect compositional differences deriving from distinct stellar nucleosynthetic processes. As shown in previous studies, the stepwise dissolution with increasing acid strengths of bulk rock carbonaceous chondrites liberates Cr with both excesses and deficits in 53Cr and 54Cr relative to the terrestrial standard. The magnitude of the 54Cr variations within a meteorite decreases in the sequence CI1 > CR2 > CM2 > CV3 > CO3 > CK4 and correlates with the degree of metamorphism of each carbonaceous chondrite class. This study shows that the Tagish Lake meteorite presents the highest excesses in 54Cr ever measured in a bulk silicate phase. According to this study, the Tagish Lake meteorite is composed of the least re-equilibrated material known at this time. The magnitude of 54Cr variation decreases now in the following sequence: Tagish Lake (ungrouped CI2) > Orgueil (CI1) > Murchison (CM2) > Allende (CV2). Moreover, this study shows that excesses in 53Cr relative to Earth can be interpreted as representing the extent of aqueous alteration on meteorite parent bodies. Finally, the high 54Cr anomalies measured in this meteorite make Tagish Lake one of the major targets to decipher the host of these anomalies.

  15. Chondritic-like xenon trapped in Archean rocks: A possible signature of the ancient atmosphere

    Science.gov (United States)

    Pujol, Magali; Marty, Bernard; Burgess, Ray

    2011-08-01

    Ancient sedimentary rocks may have retained a record of the past atmospheric composition. We present evidence for the geological preservation of remnants of the Archean atmosphere. Hydrothermal quartz containing fluid inclusions from a core drilled in 3.5 Ga-old terrains at North Pole, (Western Australia), has a Ar-Ar plateau age of 3.0 ± 0.2 Ga. An Archean age is confirmed independently by 130Ba- 130Xe dating of fluid inclusions. Xenon trapped in the present sample and in 3.5 Ga-old barite from the same locality (Pujol et al., 2009; Srinivasan, 1976) presents an isotopic composition intermediate between the atmospheric composition and that of chondritic, or solar, xenon. In contrast, the stable isotopes of neon and krypton are isotopically atmospheric. This observation suggests that the well known but unexplained enrichment of heavy Xe isotopes in the atmosphere relative to cosmochemical (chondritic or solar) end-members was progressive, and not complete ≥ 3 Ga ago. This Xe isotopic fractionation might have taken place during prolongated irradiation of the atmosphere by the ancient Sun.

  16. Classification of 24 New Ordinary Chondrites from the Grove Mountains, Antarctica

    Institute of Scientific and Technical Information of China (English)

    LU Ren; MIAO Bingkui; WANG Guiqing; DAI Deqiu; LIN Yangting; OUYANG Ziyuan; LI Chunlai

    2004-01-01

    Petrography and mineral chemistry of 24 ordinary chondrites from the Grove Mountains, Antarctica, have been studied in order to identify their chemical-petrographic types. These samples were selected from a total of 4448 Grove Mountains (GRV) meteorites collected during the 19th Chinese Antarctic Research Expedition so as to make an estimation of the large GRV meteorite collection. The chemical-petrographic types of these meteorites are presented below: 1 H3, 2 H4,4 H5, 2 H6, 1 L4, 7 L5, 5 L6, 1 LL4 and 1 LL6. The new data weaken the previous report that unequilibrated ordinary chondrites are unusually abundant in the Grove Mountains region. However, this work confirms significant differences in distribution patterns of chemical-petrographic types between the Grove Mountains and other regions in Antarctica. Many of these meteorites show significant terrestrial weathering, probably due to a high abundance ratio of meteorites found in moraines to those on blue ice. Nine meteorites experienced severe shock metamorphism, as evidenced by undulose extinction and intense fracturing of silicates and presence of shock-induced melt veins and pockets. These heavily shocked meteorites provided us with natural samples for the study of high-pressure polymorphs of minerals.

  17. Dipeptides and Diketopiperazines in the Yamato-791198 and Murchison Carbonaceous Chondrites

    Science.gov (United States)

    Shimoyama, Akira; Ogasawara, Ryo

    2002-04-01

    The Yamato-791198 and Murchison carbonaceous chondrites were analyzed for dipeptides and diketopiperazines as well as amino acids and hydantoins by gas chromatography combined with mass spectrometry. Glycylglycine (gly-gly) and cyclo(gly-gly) were detected at the concentrations of 11 and 18 pmol g^-1, respectively, in Yamato-791198, and 4 and 23 pmol g^-1, respectively, in Murchison. No other dipeptide and diketopiperazine were detected. Five hydantoins were detected at 8 to 65 pmol g^-1 in Yamato-791198 and seven in Murchison at 6 to 104 pmol g^-1. Total concentration of the glycine (gly) dimers is approximately four orders of magnitude less than the concentration of free gly in Yamato-791198, and three orders of magnitude less than that in Murchison. The absence of L- and LL-stereoisomers of dipeptides consisting of protein amino acids indicates that gly-gly and cyclo(gly-gly) detected are native to the chondrites and not from terrestrial contaminants. A possibility was discussed that the gly dimers might have been formed by condensation of gly monomers but not formed through N-carboxyanhydrides of gly.

  18. New Nd-142 Evidence for a Non-Chondritic Composition of the Moon

    Science.gov (United States)

    Nyquist, L.; Touboul, M.; Kleine, T.; Bourdon, B.; Shih, C.Y.

    2009-01-01

    The coupled Sm-147,146-Nd-143,142 systematics of lunar samples has been extensively studied for estimating the timescale of lunar differentiation. The published datasets yield consistent ages for Nd isotopic closure within the lunar mantle of approx.200 Myr after CAI formation. Although this time constraint is consistent with estimates derived from Hf-W chronometry of the Moon (>60 Myr after CAI formation), there is debate as to whether this age has chronological significance. Furthermore, there are discrepancies regarding the Nd isotope composition of the bulk Moon. Rankenburg et al. obtained a epsilon Nd-142 vs. Sm-147/Nd-144 correlation for lunar samples passing though the chondritic reference value (Sm-147/Nd-144 = 0.1967, epsilon Nd-142 = -0.21), suggesting that the Moon has a chondritic bulk composition. In contrast, the other datasets define a correlation line that passes approx.10-20 ppm above, suggesting that the Moon has a superchondritic Sm-147/Nd-144 (approx.0.206), close to that of the early depleted Earth (EDM). We present new Sm-Nd data for a high-Ti mare basalt (70135), two low-Ti mare basalt (LAP 02205 and MIL 05035) and a KREEPy low-Ti mare basalt (NWA 2977). These data are used to evaluate the significance of the Sm-Nd systematics for constraining the timescale of lunar differentiation and the bulk Nd isotope composition of the Moon.

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

    Science.gov (United States)

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

    2013-12-01

    Understanding how the Earth obtained and ultimately retained its volatiles is important for our overall understanding of large scale planetary evolution. Numerous models exist for the heterogeneous accretion of volatiles to early Earth, but accounting for all elements through accretion of typical planetary building blocks (e.g., CI chondrites) is difficult. Proto-planetary collisions resulting in the accretion of volatile-poor material under reducing conditions followed by accretion of volatile-rich material under oxidizing conditions has been suggested in such models [e.g., 1]. The heavy halogens (Cl, Br and I), a group of moderately volatile elements, are excellent tracers of planetary processing due to their low abundance and incompatible nature. Therefore characterizing halogen abundance and distribution in materials that accreted to form the planets, e.g., primitive meteorites, is crucial. One group of primitive meteorites, the enstatite chondrites (EC's), are amongst the most reduced materials in the solar system as evidenced by their unique mineral assemblage. Yet despite forming under ultra-reducing conditions, they are enriched in the moderately volatile elements, such as the halogens. The ECs are of particular interest owing to their oxygen isotopic composition which plots along the terrestrial fractionation line, linking them isotopically to the Earth-Moon system. These samples can thus potentially provide clues on the accretion of moderately volatile element rich material under reducing conditions, such as it may have existed during the early stages of Earth's accretion. Chlorine, Br and I concentrations in ECs were determined through step-heating small neutron-irradiated samples (0.3 to 3.3 mg) and measured by mass spectrometry using the noble gas proxy isotopes 38ArCl/Cl, 80KrBr/Br and 128XeI/I. The EH chondrites are consistently enriched in the heavy halogens (up to 330 ppm Cl, 2290 ppb Br and 180 ppb I), compared to other ordinary and carbonaceous

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

    Science.gov (United States)

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

    2011-01-01

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

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

    CERN Document Server

    Piani, Laurette; Remusat, Laurent

    2015-01-01

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

  2. Chemical studies of H chondrites-10 : contents of thermally labile trace elements are unaffected by late heating.

    Energy Technology Data Exchange (ETDEWEB)

    Wang, M.-S.; Wolf, S. F.; Lipschutz, M. E.; Chemical Engineering; Purdue Univ.

    1999-09-01

    We have used radiochemical neutron activation analysis (RNAA) to determine 15 trace elements, including 10 moderately and highly volatile ones - Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, In (in increasing volatility order) - in 6 H chondrite falls with low 3He contents. These plus prior RNAA data provide a compositional database of 92 H4-6 chondrite falls. Three suites of samples can be identified from their noble gas contents: 44 with 'normal' contents, and, therefore, 'normal' orbits and cosmic ray exposure histories; 8 that lost radiogenic gases, presumably by shock late in their histories; and 17 that lost cosmogenic gases by heating during close solar approach. We used the standard multivariate statistical techniques of linear discriminant analysis and logistic regression to compare contents of the 10 moderately and highly volatile trace elements, listed above, in these 3 suites. We found no significant differences. This contrasts sharply with similar comparisons involving random falls and H4-6 chondrites that landed on Earth at specific time intervals. Apparently, contents of volatile trace elements in H4-6 chondrites were established early in their histories and they are so retentively sited that loss during later heating episodes did not occur.

  3. Outgassing of Ordinary Chondritic Material and Some of its Implications for the Chemistry of Asteroids, Planets, and Satellites

    CERN Document Server

    Schaefer, L; Schaefer, Laura; Fegley, Bruce

    2006-01-01

    We used chemical equilibrium calculations to model thermal outgassing of ordinary chondritic material as a function of temperature, pressure, and bulk compositions and use our results to discuss outgassing on asteroids and the early Earth. The calculations include ~1,000 solids and gases of the elements Al, C, Ca, Cl, Co, Cr, F, Fe, H, K, Mg, Mn, N, Na, Ni, O, P, S, Si, and Ti. The major outgassed volatiles from ordinary chondritic material are CH4, H2, H2O, N2, and NH3(the latter at conditions where hydrous minerals form). Contrary to widely held assumptions, CO is never the major C-bearing gas during ordinary chondrite metamorphism. The calculated oxygen fugacity (partial pressure) of ordinary chondritic material is close to that of the quartz-fayalite-iron (QFI) buffer. Our results are insensitive to variable total pressure, variable volatile element abundances, and kinetic inhibition of C and N dissolution in Fe metal. Our results predict that Earth's early atmosphere contained CH4, H2, H2O, N2, and NH3; ...

  4. A Complex Exposure History of the Gold Basin L4-Chondrite Shower from Cosmogenic Radionuclides and Noble Gases

    Science.gov (United States)

    Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Masarik, J.; Wieler, R.

    2001-01-01

    Cosmogenic radionuclides and noble gases in samples of the Gold Basin L-chondrite shower indicate a complex exposure history, with a first stage exposure on the parent body, followed by a second stage of approx. 19 Myr in a meteoroid 3-4 m in radius. Additional information is contained in the original extended abstract.

  5. Metamorphosed CM and CI Carbonaceous Chondrites Could Be from the Breakup of the Same Earth-crossing Asteroid

    Science.gov (United States)

    Zolensky, Michael; Abell, Paul; Tonui, Eric

    2005-01-01

    Far from being the relatively unprocessed materials they were once believed to be, we now know that a significant number of carbonaceous chondrites were thermally metamorphosed on their parent asteroid(s). Numerous studies indicate that 7 "CM" and 2 "CI" chondrites have been naturally heated, variously, at from 400 to over 700 C on their parent asteroid(s). Petrographic textures reveal that this thermal metamorphism occurred after the dominant aqueous alteration phase, although some meteorites show evidence of a heating event between two aqueous alteration episodes, i.e. pro- and retrograde aqueous alteration. Aside from the issues of the identification of the transient heat source, timing of metamorphism, and the relation of these materials (if any) to conventional CM and CI chondrites, there is also a mystery related to their recovery. All of these meteorites have been recovered from the Antarctic; none are falls or finds from anyplace else. Indeed, the majority have been collected by the Japanese NIPR field parties in the Yamato Mountains. In fact, one estimate is that these meteorites account for approx. 64 wt% of the CM carbonaceous chondrites at the NIPR. The reasons for this are unclear and might be due in part to simple sampling bias. However we suggest that this recovery difference is related to the particular age of the Yamato Mountains meteorite recovery surfaces, and differences in meteoroid fluxes between the Yamato meteorites and recent falls and substantially older Antarctic meteorites. Additional information is included in the original extended abstract.

  6. Chondrule Glass Alteration in Type IIA Chondrules in the CR2 Chondrites EET 87770 and EET 92105: Insights into Elemental Exchange Between Chondrules and Matrices

    Science.gov (United States)

    Burger, Paul V.; Brearley, Adrian J.

    2004-01-01

    CR2 carbonaceous chondrites are a primitive group of meteorites that preserve evidence of a variety of processes that occurred in the solar nebula as well as on asteroidal parent bodies. CR2 chondrites are distinct from other carbonaceous chondrites by (among other properties) their relatively high abundance of chondrules (50-60 vol. %) and Fe,Ni metal (5-8 vol. %) [1]. Like the CM2 chondrites, the CRs have been affected by aqueous alteration and according to [2] show a range of degrees of alteration. In weakly- altered CR chondrites, fine-grained matrices and chondrule rims have been partially altered and chondrule mesostases show evidence of incipient aqueous alteration. In these meteorites, glassy mesostasis is still common. However, some CR chondrites, (e.g. Renazzo and Al Rais) show evidence of much more extensive alteration with complete replacement of chondrule mesostasis [2] by chlorite and serpentine. Although the general characteristics of alteration of the CR chondrites have been described, the details of alteration reactions in these meteorites remain unclear. In addition, the setting for aqueous alteration is poorly understood: both asteroidal and preaccretionary alteration scenarios have been proposed [2].

  7. Thermal history of type 3 chondrites from the Antarctic meteorite collection determined by Raman spectroscopy of their polyaromatic carbonaceous matter

    Science.gov (United States)

    Bonal, Lydie; Quirico, Eric; Flandinet, Laurène; Montagnac, Gilles

    2016-09-01

    This paper is focused on the characterization of the thermal history of 151 CV, CO and unequilibrated ordinary chondrites (UOCs) from the NASA Antarctic meteorite collection, using an approach based on the structure of the included polyaromatic carbonaceous matter determined by Raman spectroscopy. 114 out of these 151 chondrites provided Raman spectra of carbonaceous matter and allowing to assign a petrologic type, which mostly reflects the peak temperature experienced by the rock on the parent body. A thorough review of literature shows however that it is not possible to deduce a peak temperature because accurate calibration is not available. Twenty-three new weakly metamorphosed chondrites have been identified: MIL 07671 (CV3.1); DOM 08006 (CO3.0); DOM 03238, MIL 05024, MIL 05104, MIL 07193 (CO3.1); TIL 82408, LAR 06279 (LL3.05-3.1); EET 90628 (L3.0); GRO 06054, QUE 97008 (L3.05), ALHA 77176, EET 90066, LAR 04380, MET 96515, MIL 05050 (L3.1); ALHA 78133, EET 87735, EET 90909, LEW 87208, PRE 95401 (L3.05-3.1); MCY 05218 (H3.05-3.1) and MET 00506 (H3.1). This study confirms that the width of the D band (FWHMD) and the ratio of the peak intensity of the D and G bands (ID/IG) are the most adapted tracers of the extent of thermal metamorphism in type 3 chondrites. It also unambiguously shows, thanks to the large number of samples, that the width of the G band (FWHMG) does not correlate with the maturity of polyaromatic carbonaceous matter. This parameter is nevertheless very valuable because it shows that Raman spectra of CV chondrites preserve memory of either the metamorphic conditions (possibly oxidation controlled by aqueous alteration) or the nature of the organic precursor. Oxidation memory is our preferred interpretation, however an extensive petrologic characterization of this CV series is required to get firm conclusions. Pre-graphitic carbonaceous matter is reported in seven chondrites and is even the only carbonaceous material detected in the chondrites

  8. GEMS-like material in the matrix of the Paris meteorite and the early stages of alteration of CM chondrites

    Science.gov (United States)

    Leroux, H.; Cuvillier, P.; Zanda, B.; Hewins, R. H.

    2015-12-01

    The Paris meteorite is a weakly altered CM chondrite that has been discovered recently (Hewins et al., 2014). Its matrix offers the opportunity to search for well-preserved pristine pre-accretional material, as well as to study the earliest stages of aqueous alteration in the CM parent body. The study of the matrix of Paris has been conducted by analytical transmission electron microscopy on focused ion beam sections extracted from matrix areas showing different degrees of aqueous alteration. The least altered matrix sample consists of amorphous silicate grains, a few hundreds of nm in size, separated from one another by an abundant porosity. The amorphous silicates enclose numerous Fe-sulfide nanograins and their average composition is close to the chondritic composition. They share many similarities with GEMS (glass with embedded metal and sulfides) grains present in chondritic-porous interplanetary dust particles and with primitive type 3.0 carbonaceous chondrites. This first discovery of GEMS-like texture in a CM chondrite suggests that GEMS grains could have been the building blocks of the CM matrices. In more aqueously altered samples, pronounced microstructural heterogeneities were detected at the micrometer scale. The matrix consists mostly of a mixture of amorphous material and Fe-rich, spongy to fine-fibrous, poorly crystalline phyllosilicates. The porosity fraction is significantly reduced and the mixed amorphous-fibrous material frequently forms a continuous groundmass. The close association between these two material types suggests a replacement mechanism due to aqueous alteration. Chemical compositions correlate strongly with the microstructure. The amorphous material has a composition close to the chondritic value while the fine-fibrous phyllosilicate material is Fe-enriched. This Fe enrichment is found to be continuous from weakly to more heavily altered areas, in which the fibrous morphology is coarser and better crystalline. Cronstedtite with

  9. Renewed Search for FUN (Fractionated and Unidentified Nuclear Effects) in Primitive Chondrites

    Energy Technology Data Exchange (ETDEWEB)

    Tollstrup, D L; Wimpenny, J B; Yin, Q -; Ebel, D S; Jacobsen, B; Hutcheon, I D

    2011-04-07

    Ca-Al-rich inclusions (CAIs) found in primitive chondrites record processes and conditions of the earliest solar system as they are the oldest known solid objects formed in the solar system [1,2]. CAIs with fractionation and unidentified nuclear anomalies (FUN CAIs; [3]) are very rare and thusfar found exclusively in CV carbonaceous chondrites (e.g., Allende and Vigarano)[4]. FUN CAIs are characterized by large nucleosynthetic anomalies in several elements (Ca, Ti, Si, Sr, Ba, Nd, and Sm), large mass-dependant isotope fractionation (Mg, Si, and O), and very little initial {sup 26}Al [4,5 and reference therein]. Formation of FUN CAIs by thermal processing of presolar dust aggregates prior to the injection of {sup 26}Al into the protoplanetary disk has been proposed. More recently [5] proposed that FUN CAIs formed from a protosolar molecular cloud after injection of {sup 26}Al but before {sup 26}Al and {sup 27}Al were completely homogenized. Therefore discovering more FUN CAIs to perform U-Pb and other short-lived chronometric dating will provide key constraints on the age of the solar system, the isotopic composition of the protosolar molecular cloud, the earliest stages of the thermal processing in the solar system and the timing of {sup 26}Al and other short-lived radionuclide injection into the nascent solar system. Most known FUN CAIs were discovered and studied > 30 yr ago, and their isotope ratios determined using thermal ionization mass spectrometry (TIMS). Most of these FUN CAIs were almost or entirely consumed during their respective analyses. [5] recently identified a new FUN CAI (NWA 779 KS-1) based on O and Mg isotope ratios determined by SIMS and MCICPMS, respectively. We have initiated a systematic search for FUN CAIs in primitive chondrites, taking advantage of the large mass-dependant Mg isotope effects known for FUN inclusions with little or no inferred {sup 26}Al. Our strategy is to use newly developed sample cells capable of holding very large

  10. Oxygen isotope and petrological study of silicate inclusions in IIE iron meteorites and their relationship with H chondrites

    Science.gov (United States)

    McDermott, Kathryn H.; Greenwood, Richard C.; Scott, Edward R. D.; Franchi, Ian A.; Anand, Mahesh

    2016-01-01

    The origin of silicate-bearing irons, especially those in groups IAB, IIICD, and IIE, is poorly understood as silicate should have separated rapidly from molten metal. Here we report the results of high precision oxygen isotope analysis of silicate inclusions in eleven group IIE meteorites and a petrological study of silicate inclusions in ten IIE irons including those in Garhi Yasin and Tarahumara, which have not been described in detail before. Oxygen isotopes have also been analysed in 20 H chondrites to investigate their possible relationship with the IIE irons. Based on petrographic observations and mineral analysis, the silicate-bearing IIE meteorites have been divided into four types according to the nature of their silicate inclusions: (1) primitive chondritic, (2) evolved chondritic, (3) differentiated with >10 vol.% orthopyroxene, and (4) differentiated with oxygen isotope compositions, a genetic relationship between IIE irons and H chondrites is supported by our new data. However, derivation of both groups from one parent body seems unlikely. Instead, both groups probably sampled similar precursor materials and accreted at a similar nebular location. Our data suggest that the IIE meteorites formed on an internally heated H/HH chondrite-like body that experienced the initial stages of differentiation in response to radiogenic heating. However, prior to full differentiation the IIE parent body experienced a major hit-and-run style collision that resulted in silicate-metal mixing. The initial stages of this event involved a phase of rapid cooling that prevented unmixing of metal and silicates. Reassembly of the IIE parent body produced a large regolith blanket that facilitated subsequent slow cooling. The IIE parent body has probably experienced numerous subsequent less catastrophic collisions. The development of alkali glass textures in some differentiated inclusions is probably the result of one of these later events.

  11. Bulk compositions of metallic Fe-Ni of chondrites: Constraints on fractionation of siderophile and chalcophile elements

    Institute of Scientific and Technical Information of China (English)

    XU Lin; LIN Yangting; WANG Shijie; OUYANG Ziyuan

    2009-01-01

    Bulk compositions of metallic Fe-Ni from two equilibrated ordinary chondrites, Jilin (H5) and Anlong (H5), and two unequilibrated ones, GRV 9919 (L3) and GRV 021603 (H3), were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The CI-, Co-normalized abundances of siderophile and chalcophile elements of metallic Fe-Ni from the unequilibrated ordinary chondrites correlate with 50% condensation temperatures (i.e., volatility) of the elements. The refractory siderophile elements (i.e., platinum group elements, Re), Au, Ni and Co show a flat pattern (1.01(CI Co-normalized), while moderate elements (As, Cu, Ag, Ga, Ge, Zn) decrease with volatility from 0.63(CI (Co-normalized, As) to 0.05(CI (Co-normalized, Zn). Cr and Mn show deficit relative to the trend, probably due to their main partition in silicates and sulfides (nonmagnetic). Metallic Fe-Ni from the equilibrated ordinary chondrites shows similar patterns, except for strong deficit of Cr, Mn, Ag and Zn. It is indicated that these elements were almost all partitioned into silicates and/or sulfides during thermal metamorphism. The similar deficit of Cr, Mn, Ag and Zn was also found in iron meteorites.Our analyses demonstrate similar behaviors of W and Mo as refractory siderophile elements during condensation of the solar nebula, except for slight depletion of Mo in the L3 and H5 chondrites. The Mo-depletion of metallic Fe-Ni from GRV 9919 (L3) relative to GRV 021603 (H3) could be due to a more oxidizing condition of the former than the latter in the solar nebula. In contrast, the Mo-depletion of the metallic Fe-Ni from the H5 chondrites may reflect partition of Mo from metal to silicates and/or sulfides during thermal metamorphism in the asteroidal body.

  12. K-Ca Dating of Alkali-Rich Fragments in the Y-74442 and Bhola LL-Chondritic Breccias

    Science.gov (United States)

    Yokoyama, T; Misawa, K.; Okano, O; Shih, C. -Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2013-01-01

    Alkali-rich igneous fragments in the brecciated LL-chondrites, Krahenberg (LL5) [1], Bhola (LL3-6) [2], Siena (LL5) [3] and Yamato (Y)-74442 (LL4) [4-6], show characteristic fractionation patterns of alkali and alkaline elements [7]. The alkali-rich fragments in Krahenberg, Bhola and Y-74442 are very similar in mineralogy and petrography, suggesting that they could have come from related precursor materials [6]. Recently we reported Rb-Sr isotopic systematics of alkali-rich igneous rock fragments in Y-74442: nine fragments from Y-74442 yield the Rb-Sr age of 4429 plus or minus 54 Ma (2 sigma) for lambda(Rb-87) = 0.01402 Ga(exp -1) [8] with the initial ratio of Sr-87/Sr-86 = 0.7144 plus or minus 0.0094 (2 sigma) [9]. The Rb-Sr age of the alkali-rich fragments of Y-74442 is younger than the primary Rb-Sr age of 4541 plus or minus 14 Ma for LL-chondrite whole-rock samples [10], implying that they formed after accumulation of LL-chondrite parental bodies, although enrichment may have happened earlier. Marshall and DePaolo [11,12] demonstrated that the K-40 - Ca-40 decay system could be an important chronometer as well as a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [13,14] and more recently Simon et al. [15] determined K-Ca ages of lunar granitic rocks, and showed the application of the K-Ca chronometer for K-rich planetary materials. Since alkali-rich fragments in the LL-chondritic breccias are highly enriched in K, we can expect enhancements of radiogenic Ca-40. Here, we report preliminary results of K-Ca isotopic systematics of alkali-rich fragments in the LL-chondritic breccias, Y-74442 and Bhola.

  13. Oxygen isotopic compositions of chondrules from the metal-rich chondrites Isheyevo (CH/CB b), MAC 02675 (CB b) and QUE 94627 (CB b)

    Science.gov (United States)

    Krot, Alexander N.; Nagashima, Kazuhide; Yoshitake, Miwa; Yurimoto, Hisayoshi

    2010-04-01

    It has been recently suggested that (1) CH chondrites and the CB b/CH-like chondrite Isheyevo contain two populations of chondrules formed by different processes: (i) magnesian non-porphyritic (cryptocrystalline and barred) chondrules, which are similar to those in the CB chondrites and formed in an impact-generated plume of melt and gas resulted from large-scale asteroidal collision, and (ii) porphyritic chondrules formed by melting of solid precursors in the solar nebula. (2) Porphyritic chondrules in Isheyevo and CH chondrites are different from porphyritic chondrules in other carbonaceous chondrites ( Krot et al., 2005, 2008a,b). In order to test these hypotheses, we measured in situ oxygen isotopic compositions of porphyritic (magnesian, Type I and ferroan, Type II) and non-porphyritic (magnesian and ferroan cryptocrystalline) chondrules from Isheyevo and CB b chondrites MAC 02675 and QUE 94627, paired with QUE 94611, using a Cameca ims-1280 ion microprobe. On a three-isotope oxygen diagram ( δ17O vs. δ18O), compositions of chondrules measured follow approximately slope-1 line. Data for 19 magnesian cryptocrystalline chondrules from Isheyevo, 24 magnesian cryptocrystalline chondrules and 6 magnesian cryptocrystalline silicate inclusions inside chemically-zoned Fe,Ni-metal condensates from CB b chondrites have nearly identical compositions: Δ17O = -2.2 ± 0.9‰, -2.3 ± 0.6‰ and -2.2 ± 1.0‰ (2 σ), respectively. These observations and isotopically light magnesium compositions of cryptocrystalline magnesian chondrules in CB b chondrites ( Gounelle et al., 2007) are consistent with their single-stage origin, possibly as gas-melt condensates in an impact-generated plume. In contrast, Δ17O values for 11 Type I and 9 Type II chondrules from Isheyevo range from -5‰ to +4‰ and from -17‰ to +3‰, respectively. In contrast to typical chondrules from carbonaceous chondrites, seven out of 11 Type I chondrules from Isheyevo plot above the terrestrial

  14. Radar-enabled recovery of the Sutter's Mill meteorite, a carbonaceous chondrite regolith breccia.

    Science.gov (United States)

    Jenniskens, Peter; Fries, Marc D; Yin, Qing-Zhu; Zolensky, Michael; Krot, Alexander N; Sandford, Scott A; Sears, Derek; Beauford, Robert; Ebel, Denton S; Friedrich, Jon M; Nagashima, Kazuhide; Wimpenny, Josh; Yamakawa, Akane; Nishiizumi, Kunihiko; Hamajima, Yasunori; Caffee, Marc W; Welten, Kees C; Laubenstein, Matthias; Davis, Andrew M; Simon, Steven B; Heck, Philipp R; Young, Edward D; Kohl, Issaku E; Thiemens, Mark H; Nunn, Morgan H; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Cahill, Thomas A; Lawton, Jonathan A; Barnes, David; Steele, Andrew; Rochette, Pierre; Verosub, Kenneth L; Gattacceca, Jérôme; Cooper, George; Glavin, Daniel P; Burton, Aaron S; Dworkin, Jason P; Elsila, Jamie E; Pizzarello, Sandra; Ogliore, Ryan; Schmitt-Kopplin, Phillipe; Harir, Mourad; Hertkorn, Norbert; Verchovsky, Alexander; Grady, Monica; Nagao, Keisuke; Okazaki, Ryuji; Takechi, Hiroyuki; Hiroi, Takahiro; Smith, Ken; Silber, Elizabeth A; Brown, Peter G; Albers, Jim; Klotz, Doug; Hankey, Mike; Matson, Robert; Fries, Jeffrey A; Walker, Richard J; Puchtel, Igor; Lee, Cin-Ty A; Erdman, Monica E; Eppich, Gary R; Roeske, Sarah; Gabelica, Zelimir; Lerche, Michael; Nuevo, Michel; Girten, Beverly; Worden, Simon P

    2012-12-21

    Doppler weather radar imaging enabled the rapid recovery of the Sutter's Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand's parameter = 2.8 ± 0.3). Sutter's Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted. PMID:23258889

  15. Mossbauer Spectra of Weathered H5 Ordinary Chondrites from Reg EL Acfer, Algeria

    Science.gov (United States)

    Berry, F.; Oates, G.; Bland, P.; Pillinger, C. T.

    1992-07-01

    Approximately 380 meteorite specimens have been retrieved from the Acfer region of the Sahara desert, Algeria. To date, 26 of these have been classified H5 (Bischoff et al., 1990, 1991, 1992). Being the most common meteorite type and having a tightly constrained mineralogy (Mason, 1965), H5 chondrites are ideal candidates for investigating terrestrial weathering products in meteorites. Arid climate, uniform topography, and lack of a concentration/movement mechanism makes it likely that meteorites throughout Reg el Acfer were weathered by a common mechanism. Jull et al. (1991) showed a correlation in meteorites from Roosevelt County between terrestrial ^14C ages and a qualitative weathering scale. An aim of the present study is to provide a quantitative measure of weathering for the Acfer region that might allow an estimate of terrestrial age, as well as information on pairing. Meteorite Specimens: Approximately 1 g of sample was used, prepared by grinding under acetone to prevent oxidation during crushing, until a homogenized powder was produced. Mossbauer spectra were recorded at 298 degrees K with a microprocessor controlled Mossbauer spectrometer using a ^57Co/Rh source. Drive velocity was calibrated with the same source and a metallic iron foil. Results: The H5 chondrite Acfer 146 (Bischoff, forthcoming Meteoritical Bulletin) was found on 19/11/90 at coordinates 27 degrees 38'N, 4 degrees 05'E. This meteorite gave a spectrum dominated by quadrupole split absorption characteristics of Fe^2+ in a forsteritic olivine structure. A sample of the outer crust showed the additional presence of Fe^3+. XRD was insensitive to the unequivocal identification of the phases present in the two samples and given that the Mossbauer parameters of the hydrolyzed Fe^3+ species and ferric oxyhydroxides are very similar it is not possible at this stage to identify the oxidized phase. Clearly, however, the results demonstrate the sensitivity of Mossbauer spectroscopy to the products

  16. The structure and composition of metal particles in two type 6 ordinary chondrites

    Science.gov (United States)

    Holland-Duffield, C. E.; Williams, D. B.; Goldstein, J. I.

    1991-01-01

    The microstructure and composition of taenite particles were examined in two type-6 ordinary chondrites, Kernouve (H6) and Saint Severin (LL6), using reflected light microscopy and a combination of electron optical instruments. It was found that, in both meteorites, the taenite particles consisted of a narrow rim of high-Ni taenite and a central region of cloudy zone similar to those present in iron meteorites. The microstructure of the cloudy zone in Saint Severin was coarser than that in Kernouve , due to the higher Ni content and slower cooling rate of the former. Three microstructural zones were observed in the outer taenite rim of both meteorites, the origin of which is considered likely to be due to the presence of ordered domain boundaries or to the presence of two phases FeNi and FeNi3 in the high-Ni region of the outer taenite rim.

  17. Rapid Contamination During Storage of Carbonaceous Chondrites Prepared for Micro FTIR Measurements

    Science.gov (United States)

    Kebukawa, Yoko; Nakashima, Satoru; Otsuka, Takahiro; Nakamura-Messenger, Keiko; Zolensky, ichael E.

    2008-01-01

    The carbonaceous chondrites Tagish Lake and Murchison, which contain abundant hydrous minerals, when pressed on aluminum plates and analyzed by micro FTIR, were found to have been contaminated during brief (24 hours) storage. This contamination occurred when the samples were stored within containers which included silicone rubber, silicone grease or adhesive tape. Long-path gas cell FTIR measurements for silicone rubber revealed the presence of contaminant volatile molecules having 2970 cm(sup -1) (CH3) and 1265 cm(sup -1) (Si-CH3) peaks. These organic contaminants are found to be desorbed by in-situ heating infrared measurements from room temperature to 200-300 C. Careful preparation and storage are therefore needed for precious astronomical samples such as meteorites, IDPs and mission returned samples from comets, asteroids and Mars, if useful for FTIR measurements are to be made.

  18. Trace-Element Constraints on Origin of SiO2-bearing Clasts in Ordinary Chondrites

    Science.gov (United States)

    Misawa, K.; Kanazawa, M.; Bridges, J. C.; Nakamura, N.; Hutchison, R.

    1995-09-01

    Silica-rich igneous-textured clasts are found in OC [1-6]. The SiO2-bearing clasts found in the Parnallee (LL3.6) and Farmington (L5) chondrites are isotopically unique [4-6]. They plot on a mixing line defined between UOC chondrules and an 16(sub)O-depleted end member in the oxygen three isotope diagram. We analyzed trace elements including REE by MSID technique for SiO2-bearing clasts (CB1, CB4, CB7, and CB8) from Parnallee. Some major and minor elements of CB8 were determined by AA or ICP-AES. The CI-chondrite normalized REE patterns of the clasts are shown in Fig. 1. CB8 has a high Si/Mg ratio (2.5), although its bulk Mg/(Mg + Fe) and Fe/Mn ratios (0.79 and 51, respectively) are within the range of chondritic values. Refractory elements Ca and Al are highly fractionated in CB8; the clast is enriched in Ca (3 x CI) but depleted in Al (0.7 x CI). CB1, CB4, and CB7 also show Ca enrichment (3-7 x CI). CB8 is depleted in moderately volatile lithophiles Mn, Na, K, and Rb (0.18-0.71 x CI), siderophile elements Fe, Co, and Ni (0.0041-0.39 x CI), and chalcophile element Zn (0.076 x CI). The SiO2-bearing clasts analyzed exhibit a gradual depletion from LREE to HREE (CI-normalized La/Lu ratios vary from 1.6 to 18) and a large positive Eu anomaly (Eu/Eu*=2.4-14) along with a depletion of La. This LREE/HREE fractionation is inversely correlated with SiO2 contents of the clasts. Abundance of Sr is parallel to that of Eu in CB8. However, Sr is depleted compared with Eu in the other clasts. These abundance patterns are quite different from those of typical ferromagnesian chondrules in UOCs, SiO2-bearing pyroxene-rich clast in Hedjaz (L3.7) [3], and silica-rich orthopyroxenite Bo-1 in Bovedy (L3) [7]. Absence of metal and sulfide, low abundances of siderophile and chalcophile elements in the clasts imply that metal and sulfide were removed from precursor material before or during clast formation. General REE patterns of SiO2-bearing clasts from Parnallee suggest that they were

  19. The structure and composition of metal particles in two type 6 ordinary chondrites

    Energy Technology Data Exchange (ETDEWEB)

    Holland-duffield, C.E.; Williams, D.B.; Goldstein, J.I. (Intel Corp., Albuquerque, NM (USA) Lehigh University, Bethlehem, PA (USA))

    1991-06-01

    The microstructure and composition of taenite particles were examined in two type-6 ordinary chondrites, Kernouve (H6) and Saint Severin (LL6), using reflected light microscopy and a combination of electron optical instruments. It was found that, in both meteorites, the taenite particles consisted of a narrow rim of high-Ni taenite and a central region of cloudy zone similar to those present in iron meteorites. The microstructure of the cloudy zone in Saint Severin was coarser than that in Kernouve , due to the higher Ni content and slower cooling rate of the former. Three microstructural zones were observed in the outer taenite rim of both meteorites, the origin of which is considered likely to be due to the presence of ordered domain boundaries or to the presence of two phases FeNi and FeNi3 in the high-Ni region of the outer taenite rim. 21 refs.

  20. Carbon, hydrogen and nitrogen isotopes in solvent-extractable organic matter from carbonaceous chondrites

    Science.gov (United States)

    Becker, R. H.; Epstein, S.

    1982-01-01

    CCl4 and CH3OH solvent extractions were performed on the Murray, Murchison, Orgueil and Renazzo carbonaceous chondrites. Delta-D values of +300-+500% are found in the case of the CH3OH-soluble organic matter. The combined C, H and N isotope data makes it unlikely that the CH3OH-soluble components are derivable from, or simply related to, the insoluble organic polymer found in the same meteorites. A relation between the event that formed hydrous minerals in CI1 and CM2 meteorites and the introduction of water- and methanol-soluble organic compounds is suggested. Organic matter soluble in CCl4 has no N, and delta-C-13 values are lower than for CH3OH-soluble phases. It is concluded that there either are large isotopic fractionations for carbon and hydrogen between different soluble organic phases, or the less polar components are partially of terrestrial origin.

  1. Molecular Composition of Carbonaceous Globules in the Bells (CM2) Chondrite

    Science.gov (United States)

    Clemett, S. J.; Nakamura-Messenger, K.; Thomas-Keprta, K. L.; Robinson, G.-A.; Mckay, D. S.

    2009-01-01

    Some meteorites and IDPs contain micron-size carbonaceous globules that are associated with significant H and/or N isotopic anomalies. This has been interpreted as indicating that such globules may contain at least partial preserved organic species formed in the outer reaches of the proto-solar disk or the presolar cold molecular cloud. Owing to their small sizes, relatively little is known about their chemical compositions. Here we present in situ measurements of aromatic molecular species in organic globules from the Bells (CM2) chondrite by microprobe two-step laser mass spectrometry. This meteorite was chosen for study because we have previously found this meteorite to contain high abundances of globules that often occur in clusters. The Bells (CM2) globules are also noteworthy for having particularly high enrichments in H-2. and N-15. In this study, we identified individual globules and clusters of globules using native UV fluorescence.

  2. A depleted, not ideally chondritic bulk Earth: The explosive-volcanic basalt loss hypothesis

    Science.gov (United States)

    Warren, Paul H.

    2008-04-01

    It has long been customary to assume that in the bulk composition of the Earth, all refractory-lithophile elements (including major oxides Al 2O 3 and CaO, all of the REE, and the heat-producing elements Th and U) occur in chondritic, bulk solar system, proportion to one another. Recently, however, Nd-isotopic studies (most notably Boyet M. and Carlson R. W. (2006) A new geochemical model for the Earth's mantle inferred from 146Sm- 142Nd systematics. Earth Planet. Sci. Lett.250, 254-268) have suggested that at least the outer portion of the planet features a Nd/Sm ratio depleted to ˜0.93 times the chondritic ratio. The primary reaction to this type of evidence has been to invoke a "hidden" reservoir of enriched matter, sequestered into the deepest mantle as a consequence of primordial differentiation. I propose a hypothesis that potentially explains the evidence for Nd/Sm depletion in a very different way. Among the handful of major types of differentiated asteroidal meteorites, two (ureilites and aubrites) are ultramafic restites so consistently devoid of plagioclase that meteoriticists were once mystified as to how all the complementary plagioclase-rich matter (basalt) was lost. The explanation appears to be basalt loss by graphite-fueled explosive volcanism on roughly 100-km sized planetesimals; with the dispersiveness of the process dramatically enhanced, relative to terrestrial experience, because the pyroclastic gases expand into vacuous space (Wilson L. and Keil K. (1991) Consequences of explosive eruptions on small Solar System bodies: the case of the missing basalts on the aubrite parent body. Earth Planet. Sci. Lett.104, 505-512). By analogy with lunar pyroclastic products, the typical size of pyroclastic melt/glass droplets under these circumstances will be roughly 0.1 mm. Once separated from an asteroidal or planetesimal gravitational field, droplets of this size will generally spiral toward the Sun, rather than reaccrete, because drag forces such the

  3. The fractionation of noble gases in diamonds of CV3 Efremovka chondrite

    Science.gov (United States)

    Fisenko, A. V.; Verchovsky, A. B.; Semjonova, L. F.; Shukolyukov, Yu. A.

    1993-01-01

    It was shown that in diamonds of Efremovka CV3 the noble gases with normal isotopic compositions are fractionated in different degree while the correlation of isotopic anomalous components is nearly constant. Some data for noble gases in DE-4 sample of Efremovka chondrite are considered. In contrast to DE-2 sample the DE-4 was treated except conc. HClO4, 220 C in addition with mixture of conc. H2SO4+H3PO4 (1:1), 220 C, twice. Noble gases analysis were performed in Germany at Max Plank Institute fur Chemie. Noble gases were released by oxidation of samples at stepped heating from 420 C to 810 C and by pyrolysis at 580, 590, and 680 C.

  4. The amino acid and hydrocarbon contents of the Paris meteorite, the most primitive CM chondrite

    Science.gov (United States)

    Martins, Zita; Modica, Paola; Zanda, Brigitte; Le Sergeant d'Hendecourt, Louis

    2015-04-01

    The Paris meteorite is reported to be the least aqueously altered CM chondrite [1,2], and to have experienced only weak thermal metamorphism [2-5]. The IR spectra of some of Paris' fragments suggest a primitive origin for the organic matter in this meteorite, similar to the spectra from solid-state materials in molecular clouds [6]. Most of the micron-sized organic particles present in the Paris matrix exhibit 0 amino acids and the synthesis of β- and γ-amino acids. When plotted with several CM chondrites, Paris has the lowest relative abundance of β-alanine/glycine (0.15) for a CM chondrite, which fits with the relative abundance of β-alanine/glycine increasing with increasing aqueous alteration [10,11]. In addition, our results show that the isovaline detected in this meteorite is racemic (D/L= 0.99 ± 0.08; L-enantiomer excess (%) = 0.35 ± 0.5; corrected D/L = 1.03; corrected L-enantiomer excess (%) = -1.4 ± 2.6). Although aqueous alteration does not create by itself an isovaline asymmetry, it may amplify a small enantiomeric excess. Therefore, our data may support the hypothesis that aqueous alteration is responsible for the high L-enantiomer excess of isovaline observed in the most aqueously altered carbonaceous meteorites [12,13]. Paris has n-alkanes ranging from C16 to C25 and 3- to 5-ring non-alkylated polycyclic aromatic hydrocarbons (PAHs). The lack of alkylated PAHs in Paris seems to be related to the low degree of aqueous alteration on its parent body [9,14]. The extra-terrestrial aliphatic and aromatic hydrocarbon content of Paris may have an interstellar origin or contribution from interstellar precursors. In summary, the soluble organic content of the primitive CM chondrite Paris possibly relates to late phases of condensed phase chemistry in molecular clouds. References: [1] Blanchard et al. (2011) Abstract #5322. Meteoritics and Planetary Science 46:A21. [2] Caillet Komorowski et al. (2011) Abstract #5289. Meteoritics and Planetary Science 46

  5. Thermal recalcitrance of the organic D-rich component of ordinary chondrites

    Science.gov (United States)

    Remusat, L.; Piani, L.; Bernard, S.

    2016-02-01

    Carbonaceous and ordinary chondrites (CCs and OCs) contain insoluble organic matter (IOM) with large D-excess compared to other objects in the solar system. The higher the temperature experienced by CCs, the lower the D/H ratio of their IOM. It seems to be the opposite for OCs. Here, we report NanoSIMS H- (and N-) isotopic imaging of IOM of three OCs that experienced thermal metamorphism in the sequence Semarkona, Bishunpur and GRO 95502. In addition, we performed flash heating experiments on the IOM of GRO 95502 at 600 °C and characterized the residues using NanoSIMS, Raman and XANES spectroscopy. The present study shows that, in contrast to IOM of CI, CM and CR, IOM of OCs exhibits very few D-rich (or 15N-rich) hotspots. Furthermore, although the evolution of the molecular structure of OC and CC IOM is similar upon heating, their D/H ratios do not follow the same trend: the D/H of OC IOM drastically increases while the D/H of CC IOM decreases. In contrast to CC IOM, the D-rich component of which does not survive at high temperatures, the present results highlight the thermal recalcitrance of the D-rich component of OC IOM. This suggests that CCs and OCs did not accrete the same organic material, thereby challenging the hypothesis of a common precursor on chondritic parent bodies. The present results support the hypothesis that OC IOM contains an organic component that could originate from the interstellar medium.

  6. Organic Analysis in the Miller Range 090657 CR2 Chondrite: Part 2 Amino Acid Analyses

    Science.gov (United States)

    Burton, A. S.; Cao, T.; Nakamura-Messenger, K.; Berger, E. L.; Messenger, S.; Clemett, S. J.; Aponte, J. C.; Elsila, J. E.

    2016-01-01

    Primitive carbonaceous chondrites contain a wide variety of organic material, ranging from soluble discrete molecules to insoluble, unstructured kerogen-like components, as well as structured nano-globules of macromolecular carbon. The relationship between the soluble organic molecules, macromolecular organic material, and host minerals are poorly understood. Due to the differences in extractability of soluble and insoluble organic materials, the analysis methods for each differ and are often performed independently. The combination of soluble and insoluble analyses, when performed concurrently, can provide a wider understanding of spatial distribution, and elemental, structural and isotopic composition of organic material in primitive meteorites. Using macroscale extraction and analysis techniques in combination with in situ microscale observation, we have been studying both insoluble and soluble organic material in the primitive CR2 chondrite Miller Range (MIL) 090657. In accompanying abstracts (Cao et al. and Messenger et al.) we discuss insoluble organic material in the samples. By performing the consortium studies, we aim to improve our understanding of the relationship between the meteorite minerals and the soluble and insoluble organic phases and to delineate which species formed within the meteorite and those that formed in nebular or presolar environments. In this abstract, we present the results of amino acid analyses of MIL 090657 by ultra performance liquid chromatography with fluorescence detection and quadrupole-time of flight mass spectrometry. Amino acids are of interest because they are essential to life on Earth, and because they are present in sufficient structural, enantiomeric and isotopic diversity to allow insights into early solar system chemical processes. Furthermore, these are among the most isotopically anomalous species, yet at least some fraction are thought to have formed by aqueously-mediated processes during parent body alteration.

  7. Spade: An H Chondrite Impact-melt Breccia that Experienced Post-shock Annealing

    Science.gov (United States)

    Rubin, Alan E.; Jones, Rhian H.

    2006-01-01

    The low modal abundances of relict chondrules (1.8 Vol%) and of coarse (i.e. >= 2200 micron-size) isolated mafic silicate grains (1.8 Vol%) in Spade relative to mean H6 chondrites (11.4 and 9.8 vol%, respectively) show Spade to be a rock that has experienced a significant degree of melting. Various petrographic features (e.g., chromite-plagioclase assemblages, chromite veinlets, silicate darkening) indicate that melting was caused by shock. Plagioclase was melted during the shock event and flowed so that it partially to completely surrounded nearby mafic silicate grains. During crystallization, plagioclase developed igneous zoning. Low-Ca pyroxene that crystallized from the melt (or equilibrated with the melt at high temperatures) acquired relatively high amounts of CaO. Metallic Fe-Ni cooled rapidly below the Fe-Ni solws and transformed into martensite. Subsequent reheating of the rock caused transformation of martensite into abundant duplex plessite. Ambiguities exist in the shock stage assignment of Spade. The extensive silicate darkening, the occurrence of chromite-plagioclase assemblages, and the impact-melted characteristics of Spade are consistent with shock stage S6. Low shock (stage S2) is indicated by the undulose extinction and lack of planar fractures in olivine. This suggests that Spade reached a maximum prior shock level equivalent to stage S6 and then experienced post-shock annealing (probably to stage Sl). These events were followed by a less intense impact that produced the undulose extinction in the olivine, characteristic of shock stage S2. Annealing could have occurred if Spade were emplaced near impact melts beneath the crater floor or deposited in close proximity to hot debris within an ejecta blanket. Spade firmly establishes the case for post-shock annealing. This may have been a common process on ordinary chondrites (OC) asteroids.

  8. Detection of serpentine in exogenic carbonaceous chondrite material on Vesta from Dawn FC data

    Science.gov (United States)

    Nathues, Andreas; Hoffmann, Martin; Cloutis, Edward A.; Schäfer, Michael; Reddy, Vishnu; Christensen, Ulrich; Sierks, Holger; Thangjam, Guneshwar Singh; Le Corre, Lucille; Mengel, Kurt; Vincent, Jean-Baptist; Russell, Christopher T.; Prettyman, Tom; Schmedemann, Nico; Kneissl, Thomas; Raymond, Carol; Gutierrez-Marques, Pablo; Hall, Ian; Büttner, Irene

    2014-09-01

    The Dawn mission’s Framing Camera (FC) observed Asteroid (4) Vesta in 2011 and 2012 using seven color filters and one clear filter from different orbits. In the present paper we analyze recalibrated HAMO color cubes (spatial resolution ∼60 m/pixel) with a focus on dark material (DM). We present a definition of highly concentrated DM based on spectral parameters, subsequently map the DM across the Vestan surface, geologically classify DM, study its spectral properties on global and local scales, and finally, compare the FC in-flight color data with laboratory spectra. We have discovered an absorption band centered at 0.72 μm in localities of DM that show the lowest albedo values by using FC data as well as spectral information from Dawn’s imaging spectrometer VIR. Such localities are contained within impact-exposed outcrops on inner crater walls and ejecta material. Comparisons between spectral FC in-flight data, and laboratory spectra of meteorites and mineral mixtures in the wavelength range 0.4-1.0 μm, revealed that the absorption band can be attributed to the mineral serpentine, which is typically present in CM chondrites. Dark material in its purest form is rare on Vesta’s surface and is distributed globally in a non-uniform manner. Our findings confirm the hypothesis of an exogenic origin of the DM by the infall of carbonaceous chondritic material, likely of CM type. It further confirms the hypothesis that most of the DM was deposited by the Veneneia impact.

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

    Science.gov (United States)

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

    2015-11-01

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

  10. Application of an alkylammonium method for characterization of phyllosilicates in CI chondrites

    Science.gov (United States)

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

    1994-01-01

    Many meteorites and interplanetary dust particles (IDP's) with primitive compositions contain significant amounts of phyllosilicates, which are generally interpreted as evidence of protoplanetary aqueous alteration at an early period in the solar system. These meteorites are chondrites of the carbonaceous and ordinary varieties. Characterization of phyllosilicates in these materials is important because of the important physico-chemical information they hold, e.g., from well characterized phyllosilicates, thermodynamic stability relations and hence the conditions of formation of phyllosilicates in the parent body of the meteorite can be predicted. Although we are at a rudimentary level of understanding of the minerals resulting from the aqueous alteration in the early solar nebula, we know that the most common phyllosilicates present in chondritic extraterrestrial materials are serpentines, smectites, chlorites, and micas. The characterization of fine grained minerals in meteorites and IDP's rely heavily on electron beam instruments, especially transmission electron microscopy (TEM). Typically, phyllosilicates are identified by a combination of high resolution imaging of basal spacings, electron diffraction analysis, and chemical analysis. Smectites can be difficult to differentiate from micas because the smectites loose their interlayer water and the interlayers collapse to the same basal spacing as mica in the high vacuum of the TEM. In high-resolution TEM (HRTEM) images, smectite basal spacings vary from 1 nm up to 1.5 nm, while micas show 1 or 2 nm basal spacings. Not only is it difficult to differentiate smectites from micas, but there is no way of identifying different classes of smectites in meteorites and IDP's. To differentiate smectites from micas and also to recognize the charge differences among smectites, an alkylammonium method can be employed because the basal spacings of alkylammonium saturated smectites expand as a function of alkylamine chain

  11. Oxygen- and magnesium-isotope compositions of calcium-aluminum-rich inclusions from CR2 carbonaceous chondrites

    Science.gov (United States)

    Makide, Kentaro; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Hutcheon, Ian D.; Bischoff, Addi

    2009-09-01

    We report both oxygen- and magnesium-isotope compositions measured in situ using a Cameca ims-1280 ion microprobe in 20 of 166 CAIs identified in 47 polished sections of 15 CR2 (Renazzo-type) carbonaceous chondrites. Two additional CAIs were measured for oxygen isotopes only. Most CR2 CAIs are mineralogically pristine; only few contain secondary phyllosilicates, sodalite, and carbonates - most likely products of aqueous alteration on the CR2 chondrite parent asteroid. Spinel, hibonite, grossite, anorthite, and melilite in 18 CAIs have 16O-rich (Δ 17O = -23.3 ± 1.9‰, 2 σ error) compositions and show no evidence for postcrystallization isotopic exchange commonly observed in CAIs from metamorphosed CV carbonaceous chondrites. The inferred initial 26Al/ 27Al ratios, ( 26Al/ 27Al) 0, in 15 of 16 16O-rich CAIs measured are consistent with the canonical value of (4.5-5) × 10 -5 and a short duration (oxygen- and magnesium-isotope compositions (˜11 and 23‰/amu, respectively), a deficit of 26Mg, and a relatively low ( 26Al/ 27Al) 0 = (2.0 ± 1.7) × 10 -5. This could be the first FUN ( Fractionation and Unidentified Nuclear effects) CAI found in CR2 chondrites. Because this inclusion is slightly 16O-depleted compared to most CR2 CAIs and has lower than the canonical ( 26Al/ 27Al) 0, it may have experienced multistage formation from precursors with nonsolar magnesium-isotope composition and recorded evolution of oxygen-isotope composition in the early solar nebula over 0.9+2.2-0.7 My. Eight of the 166 CR2 CAIs identified are associated with chondrule materials, indicating that they experienced late-stage, incomplete melting during chondrule formation. Three of these CAIs show large variations in oxygen-isotope compositions (Δ 17O ranges from -23.5‰ to -1.7‰), suggesting dilution by 16O-depleted chondrule material and possibly exchange with an 16O-poor (Δ 17O > -5‰) nebular gas. The low inferred ( 26Al/ 27Al) 0 ratios of these CAIs (2 My after crystallization

  12. Synchrotron X-Ray Fluorescence Analysis of Trace Elements in Focused Ion Beam Prepared Sections of Carbonaceous Chondrite Iron Sulfides (CM and CR) and Associated Metal (CR)

    Science.gov (United States)

    Singerling, S. A.; Sutton, S. R.; Lanzirotti, A.; Newville, M.; Brearley, A. J.

    2016-08-01

    This study presents data on trace element abundances in CM and CR sulfides and metals. We determined that Ge and Zn were observed to be depleted relative to CI chondrite while the more volatile Se was observed to be enriched.

  13. REE and Hf distribution among mineral phases in the CV-CK clan: A way to explain present-day Hf isotopic variations in chondrites

    Science.gov (United States)

    Martin, Céline; Debaille, Vinciane; Lanari, Pierre; Goderis, Steven; Vandendael, Isabelle; Vanhaecke, Frank; Vidal, Olivier; Claeys, Philippe

    2013-11-01

    Chondrites are among the most primitive objects in the Solar System and constitute the main building blocks of telluric planets. Among the radiochronometers currently used for dating geological events, Sm-Nd and Lu-Hf are both composed of refractory, lithophile element. They are thought to behave similarly as the parent elements (Sm and Lu) are generally less incompatible than the daughter elements (Nd and Hf) during geological processes. As such, their respective average isotopic compositions for the solar system should be well defined by the average of chondrites, called Chondritic Uniform Reservoir (CHUR). However, while the Sm-Nd isotopic system shows an actual spread of less than 4% in the average chondritic record, the Lu-Hf system shows a larger variation range of 28% [Bouvier A., Vervoort J. D. and Patchett P. J. (2008) The Lu-Hf and Sm-Nd isotopic composition of CHUR: Constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets. Earth Planet. Sci. Lett.273, 48-57]. To better understand the contrast between Sm-Nd and Lu-Hf systems, the REE and Hf distribution among mineral phases during metamorphism of Karoonda (CK) and Vigarano-type (CV) carbonaceous chondrites has been examined. Mineral modes were determined from elemental mapping on a set of five CK chondrites (from types 3-6) and one CV3 chondrite. Trace-element patterns are obtained for the first time in all the chondrite-forming minerals of a given class (CK chondrites) as well as one CV3 sample. This study reveals that REE are distributed among both phosphates and silicates. Only 30-50% of Sm and Nd are stored in phosphates (at least in chondrites types 3-5); as such, they are not mobilized during early stages of metamorphism. The remaining fraction of Sm and Nd is distributed among the same mineral phases; these elements are therefore not decoupled during metamorphism. Of the whole-rock total of Lu, the fraction held in phosphate decreases significantly

  14. 187Re-187Os systematics, highly siderophile element, S-Se-Te abundances in the components of unequilibrated L chondrites

    Science.gov (United States)

    Kadlag, Yogita; Becker, Harry

    2016-01-01

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

  15. Search for extinct natural radioactivity of Pb205 via thallium-isotope anomalies in chondrites and lunar soil.

    Science.gov (United States)

    Huey, J. M.; Kohman, T. P.

    1972-01-01

    Thallium and Pb204 contents were determined by stable-isotope-dilution analysis in 16 chondrites, one achondrite, and Apollo 11 and 12 lunar fines. Meteoritic thallium contents vary over a large range, 0.02 to 100 ppb, corresponding to the fact that thallium is a highly fractionated volatile element. Lunar thallium contents are less than 5 ppb. The Tl205/Tl203 ratio was determined in most of the samples, with precision ranging from 0.03% to several percent depending mainly on the amount of thallium present. No variations from the terrestrial ratio were observed. The chondritic isochron slope for Pb205 (13.8-m.y. half-life) is less than or equal to 0.00009 (99% confidence level), corresponding to an interval of at least 60 m.y. and possibly exceeding 120 m.y. between the termination of s-process nucleosynthesis and the lead-thallium fractionations.

  16. Multi-scale three-dimensional characterization of iron particles in dusty olivine: Implications for paleomagnetism of chondritic meteorites

    DEFF Research Database (Denmark)

    Einsle, Joshua F.; Harrison, Richard J.; Kasama, Takeshi;

    2016-01-01

    Dusty olivine (olivine containing multiple sub-micrometer inclusions of metallic iron) in chondritic meteorites is considered an ideal carrier of paleomagnetic remanence, capable of maintaining a faithful record of pre-accretionary magnetization acquired during chondrule formation. Here we show how...... the magnetic architecture of a single dusty olivine grain from the Semarkona LL3.0 ordinary chondrite meteorite can be fully characterized in three dimensions, using a combination of focused ion beam nanotomography (FIB-nT), electron tomography, and finite-element micromagnetic modeling. We present a three...... and remanence vectors can sometimes lie at very large (tens of degrees) angles to the principal axes. The subtle details of the morphology can control the overall remanence state, leading in some cases to a dominant contribution from the bulk spins to the net remanence, with profound implications for predicting...

  17. Oxygen Isotopes in Early Solar System Materials: A Perspective Based on Microbeam Analyses of Chondrules from CV Carbonaceous Chondrites

    Science.gov (United States)

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

    2004-01-01

    Some of the biggest challenges to understanding the early history of the solar system include determining the distribution of oxygen isotopes amongst materials that existed in the solar nebula, and interpreting the processes that might have resulted in the observed isotopic distributions. Oxygen isotope ratios in any individual mineral grain from a chondritic meteorite may be the cumulative product of a variety of processes, including stellar nucleosynthetic events, gas/solid interactions in the molecular cloud, mixing of independent isotopic reservoirs in the nebula, mass-independent processing in the nebula, and mass-dependent fractionation effects in various environments. It is not possible to unravel this complex isotopic record unless the distribution of oxygen isotope ratios in chondritic materials is fully understood.

  18. In situ oxygen isotope compositions in olivines of different types of cosmic spherules: An assessment of relationships to chondritic particles

    Digital Repository Service at National Institute of Oceanography (India)

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

    et al., 2015a). The micrometeorites that have entered Earth’s atmosphere at high zenith angle and low velocity are interesting because their petrologic and isotopic characteristics are largely preserved thereby providing constraints on the parent... et al., 2012). Oxygen isotope studies complemented by mineralogical compositions are vital to unravel the complexity involved in distinguishing the known components of micrometeorites and their parent bodies. For carbonaceous chondrites...

  19. Crystallography of Magnetite Plaquettes and their Significance as Asymmetric Catalysts for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    Science.gov (United States)

    Chan, Q. H. S.; Zolensky, M. E.

    2015-01-01

    We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

  20. An ion probe study of the sulphur isotopic composition of Fe-Ni sulphides in CM carbonaceous chondrites

    OpenAIRE

    Bullock, E. S.; McKeegan, K. D.; Gounelle, M.; Grady, M. M.; Russell, S.S

    2004-01-01

    From the Introduction: The CM chondrites have endured variable degrees of aqueous alteration [1] which has changed their original mineralogy. A detailed study of the petrology and mineralogy of the sulphides in a suite of increasingly aqueously altered CMs, combined with sulphur isotope data measured in situ, can provide clues as to whether differences in the CM group are a result of different degrees of aqueous alteration, or whether they are the result of nebular heterogeneity.

  1. Extended chronologies of aqueous alteration in the CM2 carbonaceous chondrites: evidence from carbonates in Queen Alexandra Range 93005

    OpenAIRE

    Lee, M.; Lindgren, P.; Sofe, M.; Alexander, C.; Wang, J.

    2012-01-01

    The Antarctic CM2 carbonaceous chondrite QUE 93005 contains four compositionally distinct carbonates, namely breunnerite, calcite, dolomite and a Ca-poor dolomite. These carbonates can form monomineralic grains, or may be intergrown as bimineralic grains consisting of dolomite plus breunnerite and dolomite plus calcite, or polymineralic grains containing an intergrowth of breunnerite, Ca-poor dolomite and calcite. Carbonates in all grain types have inclusions of Fe,Ni sulphides and/or Mg-Fe p...

  2. Partition coefficients for Al, Ca, Ti, Cr, and Ni in olivine obtained by melting experiment on an LL6 chondrite

    Science.gov (United States)

    Miyamoto, M.; Mikouchi, T.; Mckay, G. A.

    1994-01-01

    We report the partition coefficients for Ca, Al, Ti, Cr, and Ni in olivine obtained through a series of melting experiments on an LL6 chondrite under varying conditions of temperature and oxygen fugacity. It is necessary to examine the variation of partition coefficients up to extremely reducing conditions in order to study meteoritic olivines. For Ca, Al, and Cr, the partition coefficients tend to decrease as temperature increases, but do not change even under extremely reducing conditions.

  3. Weathering of Ordinary Chondrites from Algeria and Australia as a Climatic Indicator

    Science.gov (United States)

    Bland, P. A.; Berry, F. J.; Pillinger, C. T.

    1995-09-01

    Introduction: Recently it has been recognized that ordinary chondrite meteorites resident in desert regions may preserve information about the climate at the time of their arrival on Earth in the degree to which they are weathered [1], providing that a stable surface has existed at the accumulation site. We present here a comparison of ^57Fe Mossbauer spectroscopy data for additional meteorites for which terrestrial ages exist, recovered from Reg el Acfer, Algeria and the Nullarbor Region, Australia. Results and Discussion: The data presented in Fig. 1 compare abundance of ferric iron oxide/oxyhydroxide species against terrestrial age [2, 3] for ordinary chondrites from Australia (a) and Algeria (b). Even with an increased dataset for Australian meteorites (compared to that already presented [1]) the initial hypothesis remains intact i.e. meteorite weathering over time is sensitive to changes in climate. Peaks in oxidation at around 2,000, 7,000 and 23,000 years correspond to periods of speleothem formation [4] and high lake level status [5]. Similarly, a period of low oxidation between 12,000-20,000 years is mirrored in low lake level status [5] and aridity in the Nullarbor [6]. The mechanism by which meteorites may record palaeoclimatic information is given in [1]. A correlation that strengthens our case is that where data from both H and L(LL) chondrites are available (i.e. around 7,000-8,000 years) the two plots are similar, indicating a broadscale environmental effect. In contrast, the distribution for meteorites from the Acfer region appears to be more random, with no correlation between H and L(LL) data. The difference may be related to the stability of the respective accumulation surfaces. The surface of the Nullarbor appears to have been stable over the last 30,000 years [7]. The Algerian and Libyan Sahara, however, has experienced several episodes of active fluvial processes over the last 10,000 years [8] which may have profoundly effected the meteorites

  4. Evidence for 26Al in Feldspars from the H4 Chondrite Ste. Marguerite

    Science.gov (United States)

    Zinner, E.; Gopel, C.

    1992-07-01

    One of the important questions for the history of the early solar system is whether or not there was enough ^26Al to melt small planetary bodies through the heat released by its decay. Although there is ample evidence for the existence of live ^26Al in refractory inclusions (Wasserburg and Papanastassiou, 1982; Hutcheon, 1982; Podosek et al., 1991), CAIs are special objects with peculiar properties and their Al is not necessarily representative of that of their host meteorites nor the early solar systems. Furthermore, some inclusions do not show any evidence for ^26Al (Wasserburg and Papanastassiou, 1982; Ireland, 1990; Virag et al., 1991), raising the possibility of ^26Al heterogeneity. The only previous observation of ^26Mg excesses attributed to the decay of ^26Al outside of CAIs was in an igneous clast from Semarkona (Hutcheon and Hutchison, 1989) leading to the conclusion that ^26Al indeed could have been a heat source for planetary melting. We have measured Al-Mg in plagioclase grains from the H4 chondrite Ste. Marguerite by ion microprobe mass spectrometry. Feldspars from H4 chondrites are good samples for addressing the problem of ^26Al as heat source because most Al resides in this phase and some H4s experienced fast cooling (Pellas and Storzer, 1981); in fact, the possibility of live ^26Al in feldspars from H4 chondrites that cooled fast has been predicted by Pellas and Storzer (1981). Furthermore, extremely precise absolute Pb/Pb ages exist for these meteorites (Gopel et al., 1991). Figure 1 shows the measurements on five feldspar crystals. All show ^26Mg excesses. A fit through the data points and the normal ^26Mg/^24Mg ratio of 0.13962 obtained from Lake County plagioclase measured under the same instrumental conditions as the Ste. Marguerite samples yields a (^26Al/^27Al)(sub)0 ratio of (2.0 +- 0.6) x 10^-7. If interpreted chronologically this ratio dates the retention of radiogenic ^26Mg in Ste. Marguerite feldspar to 5.6 +- 0.4 Ma after the

  5. In situ observation of D-rich carbonaceous globules embedded in NWA 801 CR2 chondrite

    Science.gov (United States)

    Hashiguchi, Minako; Kobayashi, Sachio; Yurimoto, Hisayoshi

    2013-12-01

    Eighty-five D-rich carbonaceous particles were identified in the matrix of the NWA 801 CR2 chondrite using isotope microscopy. The occurrence of 67 D-rich carbonaceous particles was characterized using secondary electron microscopy combined with X-ray elemental mapping. The close association of H and C, and D-enrichment suggests that the D-rich carbonaceous particles correspond to organic matter. The D-rich organic particles were scattered ubiquitously throughout the matrix at a concentration of approximately 660 ppm. The morphology of the D-rich carbonaceous particles is globular up to about 1 μm in diameter and is classified into four types: ring globules, round globules, irregular-shaped globules, and globule aggregates. The ring globules are ring-shaped organic matter containing silicate and/or oxide, with or without a void in the center. This is the first report of silicate and oxide grains surrounded by D-rich organic matter. The globule aggregates are composed of several D-rich organic globules mixed with silicates. Morphology of ring globules is very similar to core-mantle grain produced in the molecular cloud or in the outer solar nebula inferring by astronomy, suggesting that the organic globules have formed by UV photolysis in the ice mantle. Silicates or oxides attached to D-rich organic globules are the first observation among chondrites so far and may be unique nature of CR2 chondrites. The hydrogen isotopic compositions of the ring globules, round globules, irregular-shaped globules, and globule aggregates are δD = 3000-4800, 2900-8100, 2700-11,000, and 2500-11,000‰, respectively. Variations of D/H ratio of these organic globules seemed to be attributed to variations of D/H ratio of the organic radicals or differences of content of the D-rich organic radicals. There are no significant differences in the hydrogen isotopic compositions among the four types of D-rich carbonaceous matter. The D-enrichments suggest that these organic globules have

  6. Organic Analysis in the Miller Range 090657 CR2 Chondrite: Part 3 C and N Isotopic Imaging

    Science.gov (United States)

    Messenger, S.; Nakamura-Messenger, K.; Elsila, J. E.; Berger, E. L.; Burton, A. S.; Clemett, S. J.; Cao, T.

    2016-01-01

    Primitive carbonaceous chondrites contain a wide variety of organic material, ranging from soluble discrete molecules to insoluble nanoglobules of macro-molecular carbon. The relationship between the soluble organic molecules, macromolecular organic material, and host minerals are poorly understood. Large H, C and N isotopic anomalies suggest some organic components formed in low-T interstellar or outer Solar System environments. The highest isotope anomalies occur in m-scale inclusions in the most primitive materials, such as cometary dust and the least altered carbonaceous chondrites. Often, the hosts of these isotopically anomalous 'hotspots' are discrete organic nanoglobules that probably formed in the outermost reaches of the protosolar disk or cold molecular cloud. Molecular and isotopic studies of meteoritic organic matter are aimed at identifying the chemical properties and formation processes of interstellar organic materials and the subsequent chemical evolutionary pathways in various Solar System environments. The combination of soluble and insoluble analyses with in situ and bulk studies provides powerful constraints on the origin and evolution of organic matter in the Solar System. Using macroscale extraction and analysis techniques as well as microscale in situ observations we have been studying both insoluble and soluble organic material in primitive astromaterial samples. Here, we present results of bulk C and N isotopic measurements and coordinated in situ C and N isotopic imaging and mineralogical and textural studies of carbonaceous materials in a Cr2 carbonaceous chondrite. In accompanying abstracts we discuss the morphology and distribution of carbonaceous components and soluble organic species of this meteorite.

  7. Hydrogen and major element concentrations on 433 Eros: Evidence for an L- or LL-chondrite-like surface composition

    Science.gov (United States)

    Peplowski, Patrick N.; Bazell, David; Evans, Larry G.; Goldsten, John O.; Lawrence, David J.; Nittler, Larry R.

    2015-03-01

    A reanalysis of NEAR X-ray/gamma-ray spectrometer (XGRS) data provides robust evidence that the elemental composition of the near-Earth asteroid 433 Eros is consistent with the L and LL ordinary chondrites. These results facilitated the use of the gamma-ray measurements to produce the first in situ measurement of hydrogen concentrations on an asteroid. The measured value, 1100-700+1600 ppm, is consistent with hydrogen concentrations measured in L and LL chondrite meteorite falls. Gamma-ray derived abundances of hydrogen and potassium show no evidence for depletion of volatiles relative to ordinary chondrites, suggesting that the sulfur depletion observed in X-ray data is a surficial effect, consistent with a space-weathering origin. The newfound agreement between the X-ray, gamma-ray, and spectral data suggests that the NEAR landing site, a ponded regolith deposit, has an elemental composition that is indistinguishable from the mean surface. This observation argues against a pond formation process that segregates metals from silicates, and instead suggests that the differences observed in reflectance spectra between the ponds and bulk Eros are due to grain size differences resulting from granular sorting of ponded material.

  8. Cosmic-ray exposure histories of two Antarctic meteorites from Chinese collections and the Guangmingshan and Zhuanghe chondrites

    Institute of Scientific and Technical Information of China (English)

    WANG; Daode(王道德); LIN; Yangting(林杨挺); LIU; Xiaohan(刘小汉); JU; Yitai(琚宜太)

    2003-01-01

    Concentrations of noble gases of two Antarctic meteorites (GRV 98002, 98004) from Chinese collections, and the Guangmingshan and Zhuanghe chondrites were measured. Based on the petrography and mineralogy of these meteorites, and production rates of the cosmogenic nuclides, we calculated cosmic-ray exposure and gas retention ages of the four chondrites. Exposure ages of the four chondrites are 0.052 Ma ± 0.008 Ma (GRV 98004, H5), 17.0 Ma ± 2.5 Ma (GRV98002, L5), 3.8 Ma ± 0.6 Ma (Zhuanghe, H5), and 68.9 Ma ± 10 Ma (Guangmingshan, H5), respectively. The exposure age of GRV 98004 is the lowest value of Antarctic meteorites reported up to date; while that of Guangmingshan is higher than other Chinese meteorites of H-group. Both GRV 98002 and Zhuanghe have low 4He concentrations, probably due to shock effects or solar heating at orbits with small perihelion distances during cosmic-ray exposure. On the other hand, losses of cosmogenic 3He and 4He are correlated with both GRV 98002 and Guangmingshan.

  9. Searching for Extraterrestrial Amino Acids in a Contaminated Meteorite: Amino Acid Analyses of the Canakkale L6 Chondrite

    Science.gov (United States)

    Burton, A. S.; Elsila, J. E.; Glavin, D. P.; Dworkin, J. P.; Ornek, C. Y.; Esenoglu, H. H.; Unsalan, O.; Ozturk, B.

    2016-01-01

    Amino acids can serve as important markers of cosmochemistry, as their abundances and isomeric and isotopic compositions have been found to vary predictably with changes in parent body chemistry and alteration processes. Amino acids are also of astrobiological interest because they are essential for life on Earth. Analyses of a range of meteorites, including all groups of carbonaceous chondrites, along with H, R, and LL chondrites, ureilites, and a martian shergottite, have revealed that amino acids of plausible extraterrestrial origin can be formed in and persist after a wide range of parent body conditions. However, amino acid analyses of L6 chondrites to date have not provided evidence for indigenous amino acids. In the present study, we performed amino acid analysis on larger samples of a different L6 chondite, Canakkale, to determine whether or not trace levels of indigenous amino acids could be found. The Canakkale meteor was an observed fall in late July, 1964, near Canakkale, Turkey. The meteorite samples (1.36 and 1.09 g) analyzed in this study were allocated by C. Y. Ornek, along with a soil sample (1.5 g) collected near the Canakkale recovery site.

  10. Earth's Uranium and Thorium content and geoneutrinos fluxes based on enstatite chondrites

    Science.gov (United States)

    Javoy, Marc; Kaminski, Edouard

    2014-12-01

    The Earth's thermal evolution is controlled by the amount of heat released by the radioactive decay of 40K, 238U, 235U and 232Th. Their crust and upper mantle content is inferred from direct sampling, whereas estimating the lower mantle concentrations requires indirect constraints, such as those brought by primitive chondrites, or by geoneutrinos. Here we follow the framework of "E-Earth" models, based on the isotopic and chemical composition of E-chondrites (EC), to calculate U and Th concentrations in the Earth's present day mantle, and the corresponding geoneutrinos flux. The model uses a compilation of data of U and Th contents of EC and account for the Earth differentiation and crust extraction. We obtain that the Bulk Silicate Earth (BSE) contains 15.4±1.8 ppb of Uranium and 51.3±4.4 ppb of Thorium, and has an average Th/U mass ratio of 3.4±0.4, with a peak value around 3.15. The prediction of geoneutrinos events originating from the mantle (i.e., without taking into account the local contribution of the crust) is 5.1±1.0 TNU, with 4.3±0.9 TNU coming from Uranium, and 0.8±0.2 TNU from Thorium. These numbers are in good agreement with the most recent KamLAND detector estimate, and compatible with the (higher) Borexino flux. On the other hand, the KamLAND constraints are not consistent with the high content of heat producing elements in the mantle predicted by the simple application of parameterized convection model to the thermal evolution of the Earth's mantle. Since the measurement error in the mantle neutrino flux is currently dominated by the crustal contribution, geoneutrinos cannot for now discriminate between CI-based and EH-base models of the Earth's composition. Further progress is expected if an ocean based geoneutrino detector is deployed.

  11. Magnetite as Possible Template for the Synthesis of Chiral Organics in Carbonaceous Chondrites

    Science.gov (United States)

    Chan, Q. H. S.; Zolensky, M. E.

    2014-01-01

    The main goal of the Japanese Aerospace Ex-ploration Agency (JAXA) Hayabusa-2 mission is to visit and return to Earth samples of a C-type asteroid (162173) 1999 JU3 in order to understand the origin and nature of organic materials in the Solar System. Life on Earth shows preference towards the set of organics with particular spatial arrangements, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life 'determines' to use the left- (L-) form over the right- (D-) form of amino acids, resulting in a L-enantiomeric excess (ee). Recent studies have shown that L-ee is found within the alpha-methyl amino acids in meteorites [1, 2], which are amino acids with rare terrestrial occurrence, and thus point towards a plausible abiotic origin for ee. One of the proposed origins of chiral asymmetry of amino acids in meteorites is their formation with the presence of asymmetric catalysts [3]. The catalytic mineral grains acted as a surface at which nebular gases (CO, H2 and NH3) were allowed to condense and react through Fisher Tropsch type (FTT) syntheses to form the organics observed in meteorites [4]. Magnetite is shown to be an effective catalyst of the synthesis of amino acids that are commonly found in meteorites [5]. It has also taken the form as spiral magnetites (a.k.a. 'plaquettes'), which were found in various carbonaceous chondrites (CCs), including C2s Tagish Lake and Esseibi, CI Orgueil, and CR chondrites [e.g., 6, 7, 8]. In addition, L-ee for amino acids are common in the aqueously altered CCs, as opposed to the unaltered CCs [1]. It seems possible that the synthesis of amino acids with chiral preferences is correlated to the alteration process experienced by the asteroid parent body, and related to the configuration of spiral magnetite catalysts. Since C-type asteroids are considered to be enriched in organic matter, and the spectral data of 1999 JU3 indicates a certain de-gree of aqueous alteration [9], the Hayabusa-2 mission serves as

  12. The Origin of Non-chondritic HSE Ratios in the Earth's Mantle

    Science.gov (United States)

    Laurenz, V.; Rubie, D. C.; Frost, D. J.; Jacobson, S. A.; Morbidelli, A.; Palme, H.; Vogel, A. K.

    2015-12-01

    It is generally thought that Earth's mantle abundances of highly siderophile elements (HSE) were established by the addition of a chondritic late veneer to a mantle that was stripped of HSEs by core formation. A long-standing problem with this hypothesis is that the mantle's suprachondritic Pd/Ir and Ru/Ir ratios cannot be reconciled with any known meteorite group. To address this issue, we modelled the effect of metal-silicate segregation on abundances of the HSE and S in the Earth's mantle by including these elements in a combined accretion/core-formation model. Because in our model only a small fraction of the mantle equilibrates with core-forming metal, the bulk mantle HSE abundances are too large by the end of accretion. Sulfur abundances also greatly exceed S-saturation levels at magma ocean crystallisation temperatures, leading to the formation of a global immiscible sulfide melt that segregated to the core, thus removing HSEs from the mantle [1]. To better constrain the role of sulfide segregation on the HSE budget of the mantle, we experimentally determined the sulfide-silicate partitioning of Pt, Pd, Ru and Ir under high P-T conditions. Results show that Pd and Ru are less chalcophile at pressures above ~20 GPa compared to Pt and Ir, as opposed to the metal-silicate system where Ru is more siderophile than Pt [2]. These results are included in our model, which now involves localized segregation of core-forming metal followed by widespread exsolution and segregation of immiscible sulfide liquids. Platinum and Ir are efficiently extracted from the mantle whereas significant concentrations of Ru and Pd remain. Late veneer addition occurs after sulfide segregation has ceased due to magma ocean solidification. This model reproduces perfectly the non-chondritic Ru/Ir and Pd/Ir ratios of the mantle, reflecting incomplete removal of Ru and Pd from the mantle with core-forming sulfide melts. [1] O'Neill (1991) GCA 55, 1159-1172. [2] Mann et al. (2012) GCA 84, 593-613.

  13. Rubidium isotopes in primitive chondrites: Constraints on Earth's volatile element depletion and lead isotope evolution

    Science.gov (United States)

    Nebel, O.; Mezger, K.; van Westrenen, W.

    2011-05-01

    The bulk silicate Earth (BSE) shows substantial deficits in volatile elements compared to CI-chondrites and solar abundances. These deficits could be caused by pre-accretionary depletion in the solar nebula during condensation of solids, or by later heat-driven evaporation during collision of small bodies that later accreted to form the Earth. The latter is considered to result in isotope fractionation for elements with low condensation temperatures that correlates with the degree of depletion. Here, we report first high-precision isotope ratio measurements of the moderately volatile and lithophile trace element Rb. Data from seventeen chondrite meteorites show that their Rb isotope abundances are nearly indistinguishable from Earth, not deviating more than 1 per mil in their 87Rb/85Rb. The almost uniform solar system Rb isotope pool suggests incomplete condensation or evaporation in a single stage is unlikely to be the cause of the volatile element deficit of the Earth. As Rb and Pb have similar condensation temperatures, we use their different degrees of depletion in the BSE to address the mechanisms and timing of terrestrial volatile depletion. The Rb isotope data are consistent with a scenario in which the volatile budget of the Earth was generated by a mixture of a highly volatile-element depleted early Proto-Earth with undepleted material in the course of terrestrial accretion. Observed Pb and Rb abundances and U-Pb and Rb-Sr isotope systematics suggest that volatile addition occurred at approximately the same time at which last core-mantle equilibration was achieved. In line with previous suggestions, this last equilibration involved a second stage of Pb (but not Rb) depletion from the BSE. The timing of this second Pb loss event can be constrained to ~ 110 Ma after the start of the solar system. This model supports a scenario with core storage of Pb in the aftermath of a putative Moon forming giant impact that also delivered the bulk of the volatile

  14. A Deep Moho in "Small Planet" Vesta and Implication Regarding the Chondritic Nature of Protoplanets

    Science.gov (United States)

    Clenet, H.; Jutzi, M.; Barrat, J. A.; Asphaug, E. I.; Benz, W.; Gillet, P.

    2014-12-01

    Asteroid 4-Vesta is the only differentiated protoplanet [1] which has been extensively explored by a space probe, and is represented by a large collection of basaltic and ultramafic samples, the Howardite-Eucrite-Diogenite (HED) meteorites. High-resolution global mapping by the Dawn probe revealed that the south polar depression is composed of two overlapping impact basins, Veneneia and Rheasilvia [2]. Numerical simulations taking into account both sequential events [3] show that surface material in the northern hemisphere of Vesta came from a depth of about 20 km, whereas the exposed southern material comes from a depth of 60 to 100 km. Recent magma-ocean crystallization models [4], which consider a chondritic initial composition, predict a crustal thickness of 30-40 km. Thus a succession of two impacts would have dug well into the olivine-rich mantle. Here we use the results from 3D smooth particle hydrodynamics impact simulations to show that, not only the floor of the basins should expose very deep lithologies, but that a significant proportion of the rocks which have escaped from Vesta during the second impact originated from depth much greater than 40 km. We also mapped locally Vesta's mineralogy with images from the Dawn VIR spectrometer. The lack of olivine-rich lithologies in the Veneneia/Rheasilvia region, and the simultaneous lack of mantle samples among the vestoids and HEDs together provide evidence that the crust-mantle boundary (or Moho) was not reached during the two impacts, and entails that Vesta's Moho is deeper than 80 km [5]. With a deep Moho, it appears clear that the mantle is much thinner than expected, leading to the conclusion that Vesta contains far less olivine than predicted by magma-ocean crystallization models. This could be an evidence that its bulk chemical composition deviates substantially from a chondritic composition for major elements, alike as for sodium and other volatiles. [1] Russell et al, Science 336, 684-686, 2012

  15. The Anatomy and Bulk Composition of CAI Rims in the Vigarano (CV3) Chondrite

    Science.gov (United States)

    Ruzicka, A.; Boynton, W. V.

    1993-07-01

    A striking feature of Ca,Al-rich inclusions (CAIs) in chondrites is the presence of mineralogical layers that typically form rim sequences up to 50 micrometers thick [1]. Many ideas regarding the origin of CAI rims have been proposed, but none are entirely satisfactory. The detailed mineralogy and bulk compositions of relatively unaltered CAI rims in the Vigarano (CV3) chondrite described here provide constraints on hypotheses of rim formation. Rim Mineralogy: CAIs in Vigarano consist of melilite (mel)- and spinel (sp)- rich varieties, both of which are rimmed [2]. Around mel-rich objects, the layer sequence is CAI interior --> sp-rich layer (sometimes absent) --> mel/anorthite (anor) layer --> Ti-Al-rich clinopyroxene (Tpx) layer --> Al- diopside (Al-diop) layer --> olivine (ol) +/- Al-diop layer --> host matrix. The sequence around sp-rich objects differs from this in that the mel/anor layer is absent. Both the sp-rich layer around mel-cored CAIs and the cores of sp-rich CAIs in Vigarano are largely comprised of a fine-grained (anor layer is sometimes monomineralic, consisting of mel alone, or bimineralic, consisting of both mel and anor. Where bimineralic, anor typically occurs in the outer part of the layer. In places, anor (An(sub)99-100) has partially altered to nepheline and voids. Rim mel is systematically less gehlenitic than mel in the CAI interiors, especially compared to mel in the interior adjacent to the rims. The Tpx layer (>2 and up to 15 wt% TiO2) and Al-diop layer ( sp + fo --> sp + fo + anor or mel or Tpx) that does not correspond to observed rim sequences. It thus appears that (1) the rim region did not form through crystallization of molten CAIs; and (2) rim layers did not originate solely by the crystallization of a melt layer present on a solid CAI core [4,5]. References: [1] Wark D. A. and Lovering J. F. (1977) Proc. LSC 8th, 95-112. [2] Ruzicka A. and Boynton W. V. (1991) Meteoritics, 26, 390-391. [3] Stolper E. (1982) GCA, 46, 2159

  16. Thermal history of the H-chondrite parent body: Implications for metamorphic grade and accretionary time-scales

    Science.gov (United States)

    Monnereau, Marc; Toplis, Michael J.; Baratoux, David; Guignard, Jérémy

    2013-10-01

    Multiple temperature-age constraints for eight H-chondrite samples have been used to provide insight into the thermal history of their parent-body through combination with numerical models of thermal evolution assuming internal heating by 26Al and conductive cooling. The effect of spreading accretion out over time is the principal focus of this work. A wide range of body size and date of accretion is systematically tested for different values of accretion rate in order to quantify and illustrate the parameter space that is consistent with the available thermo-chronological data. We conclude that the H-chondrite samples considered have a thermal history consistent with a parent body that at some stage had a concentric 'onion-shell' internal structure. That body had a radius no larger than 130 km, and accretion most probably took place over a time interval on the order of 0.0-0.2 Myr, approximately 2 Myr after CAI condensation. In any case, the time interval of accretion is unlikely to have been more than 0.5 Myr supporting evidence in favour of rapid accretion, possibly through reassembly of the fragments of an earlier generation of bodies. Furthermore, the H-chondrites studied here are inferred to have come from a wide depth range within the body where they experienced metamorphism, indicating that preservation of the onion-shell structure is unlikely. The presence of an insulating regolith does not modify this conclusion, as appropriate thermal histories for the three H6 samples considered cannot be reproduced at depths near the surface. Asteroid 6-Hebe may be the parent body of the H-chondrites, but the high bulk density of the latter is difficult to reconcile with a 'rubble-pile' structure of pure H-chondrite material. Finally, optimized thermal histories are used to constrain the temperatures characterizing boundaries between petrological types (800, 1000, and 1140 K for the H3/4, H4/5, and H5/6 boundaries respectively). In detail, the type 6 samples studied

  17. Application of Scanning-Imaging X-Ray Microscopy to Fluid Inclusion Candidates in Carbonates of Carbonaceous Chondrites

    Science.gov (United States)

    Tsuchiyama, Akira; Nakano, Tsukasa; Miyake, Akira; Akihisa, Takeuchi; Uesugi, Kentaro; Suzuki, Yoshio; Kitayama, Akira; Matsuno, Junya; Zolensky, Michael E.

    2016-01-01

    In order to search for such fluid inclusions in carbonaceous chondrites, a nondestructive technique using x-ray micro-absorption tomography combined with FIB sampling was developed and applied to a carbonaceous chondrite. They found fluid inclusion candidates in calcite grains, which were formed by aqueous alteration. However, they could not determine whether they are really aqueous fluids or merely voids. Phase and absorption contrast images can be simultaneously obtained in 3D by using scanning-imaging x-ray microscopy (SIXM). In refractive index, n=1-sigma+i(beta), in the real part, 1-sigma is the refractive index with decrement, sigma, which is nearly proportional to the density, and the imaginary part, beta, is the extinction coefficient, which is related to the liner attenuation coefficient, mu. Many phases, including water and organic materials as well as minerals, can be identified by SIXM, and this technique has potential availability for Hayabusa-2 sample analysis too. In this study, we examined quantitative performance of d and m values and the spatial resolution in SIXM by using standard materials, and applied this technique to carbonaceous chondrite samples. We used POM ([CH2O]n), silicon, quartz, forsterite, corundum, magnetite and nickel as standard materials for examining the sigma and mu values. A fluid inclusion in terrestrial quartz and bi-valve shell (Atrina vexillum), which are composed of calcite and organic layers with different thickness, were also used for examining the spatial resolution. The Ivuna (CI) and Sutter's Mill (CM) meteorites were used as carbonaceous chondrite samples. Rod- or cube-shaped samples 20-30 micron in size were extracted by using FIB from cross-sectional surfaces of the standard materials or polished thin sections of the chondrites, which was previously observed with SEM. Then, the sample was attached to a thin W-needle and imaged by SIXM system at beamline BL47XU, SPring-8, Japan. The slice thickness was 109.3 nm

  18. The isotope composition of selenium in chondrites constrains the depletion mechanism of volatile elements in solar system materials

    Science.gov (United States)

    Vollstaedt, Hauke; Mezger, Klaus; Leya, Ingo

    2016-09-01

    Solar nebula processes led to a depletion of volatile elements in different chondrite groups when compared to the bulk chemical composition of the solar system deduced from the Sun's photosphere. For moderately-volatile elements, this depletion primarily correlates with the element condensation temperature and is possibly caused by incomplete condensation from a hot solar nebula, evaporative loss from the precursor dust, and/or inherited from the interstellar medium. Element concentrations and interelement ratios of volatile elements do not provide a clear picture about responsible mechanisms. Here, the abundance and stable isotope composition of the moderately- to highly-volatile element Se are investigated in carbonaceous, ordinary, and enstatite chondrites to constrain the mechanism responsible for the depletion of volatile elements in planetary bodies of the inner solar system and to define a δ 82 / 78 Se value for the bulk solar system. The δ 82 / 78 Se of the studied chondrite falls are identical within their measurement uncertainties with a mean of - 0.20 ± 0.26 ‰ (2 s.d., n = 14, relative to NIST SRM 3149) despite Se abundance depletions of up to a factor of 2.5 with respect to the CI group. The absence of resolvable Se isotope fractionation rules out a kinetic Rayleigh-type incomplete condensation of Se from the hot solar nebula or partial kinetic evaporative loss on the precursor material and/or the parent bodies. The Se depletion, if acquired during partial condensation or evaporative loss, therefore must have occurred under near equilibrium conditions to prevent measurable isotope fractionation. Alternatively, the depletion and cooling of the nebula could have occurred simultaneously due to the continuous removal of gas and fine particles by the solar wind accompanied by the quantitative condensation of elements from the pre-depleted gas. In this scenario the condensation of elements does not require equilibrium conditions to avoid isotope

  19. Petrology of the Baszkowka L5 chondrite: A record of surface-forming processes on the parent body

    Science.gov (United States)

    Przylibski, T. A.; Pilski, A. S.; Zagożdżon, P. P.; Kryza, R.

    2003-06-01

    We review the petrology of Baszkowka, present new microprobe data on mineral constituents, and propose a model for surface properties of the parent body consistent with these data. The low shock index and high porosity of the Baszkowka L5 chondrite mean that considerable primary textural and petrographic detail is preserved, allowing insight into the structure and evolution of the parent body. This meteorite formed in a sedimentary environment resembling that in which pyroclastic rocks are deposited. The origin of the component chondrules, achondritic fragments (mostly olivine and pyroxene aggregates), chondritic-achondritic aggregates, and compound chondrules can be explained by invoking collision of 2 melted or partially melted planetesimals, each covered with a thin crust. This could have happened at an early stage in the evolution of the solar system, between 1 and 2 Myr after its origin. The collision resulted in the formation of a cloud containing products of earlier magmatic crystallization (chondrite and achondrite fragments) from which new chondrules were created. Particle collision in this cloud produced fragmented chondrules, chondritic-achondritic aggregates, and compound chondrules. Within this low-density medium, these particles were accreted on the surface of the larger of the planetesimals involved in the collision. The density of the medium was low enough to prevent grain-size sorting of the components but high enough to prevent the total loss of heat and to enable the welding of fragments on the surface of the body. The rock material was homogenized within the cloud and, in particular, within the zone close to the planetesimal surface. The hot material settled on the surface and became welded as molten or plastic metal, and sulfide components cemented the grains together. The process resembled the formation of welded ignimbrites. Once these processes on the planetesimal surface were completed, no subsequent recrystallization occurred. The high

  20. The thermal release of HG from chondrites and their thermal histories

    Science.gov (United States)

    Jovanovic, S.; Reed, G. W.

    1985-08-01

    A quantitative treatment and implications of isothermal and linear heating data on Hg in meteorites are given as a sequel to a more qualitative analysis of meteorite thermal histories (Reed and Jovanovic, 1968). Studies of Hg in terrestrial metamorphic rocks establish that thermal events to which meteorites were subjected fall in the same temperature range, of 400-900 C, as exists during terrestrial metamorphism. Hg diffusion parameters based on data from the linear and isothermal heating experiments are calculated. The conclusions are: (1) Meteorites experienced thermal events of the same magnitude as those measured by primarily mineralogical metamorphic indicators reviewed by Dodd (1969); (2) no correspondence with mineralogical-petrological metamorphic grade is evident; (3) Hg data for some chondrites correlate with shock facies (non-thermal) indicators (Dodd and Jarosewich, 1979); (4) small Hg activation energies (6-14 kcal/mole) require that the meteorites must have been stored in closed systems until low temperatures were attained. Hg must be presented as an involatile mineral(s) or as a substituent in a host phase at temperatures below 100 C. Consistent with this interpretation is the fact that despite diffusion times of 100-1,000,000 years at 200 K, Hg was retained in small objects over cosmic ray exposure periods of a hundred-million years.

  1. Synchrotron Radiation XRD Analysis of Indialite in Y-82094 Ungrouped Carbonaceous Chondrite

    Science.gov (United States)

    Mikouchi, T.; Hagiya, K.; Sawa, N.; Kimura, M.; Ohsumi, K.; Komatsu, M.; Zolensky, M.

    2016-01-01

    Y-82094 is an ungrouped type 3.2 carbonaceous chondrite, with abundant chondrules making 78 vol.% of the rock. Among these chondrules, an unusual porphyritic Al-rich magnesian chondrule is reported that consists of a cordierite-like phase, Al-rich orthopyroxene, cristobalite, and spinel surrounded by an anorthitic mesostasis. The reported chemical formula of the cordierite-like phase is Na(0.19)Mg(1.95)Fe(0.02)Al(3.66)Si(5.19)O18, which is close to stoichiometric cordierite (Mg2Al3[AlSi5O18]). Although cordierite can be present in Al-rich chondrules, it has a high temperature polymorph (indialite) and it is therefore necessary to determine whether it is cordierite or indialite in order to better constrain its formation conditions. In this abstract we report on our synchrotron radiation X-ray diffraction (SR-XRD) study of the cordierite-like phase in Y-82094.

  2. Hydrogen Isotopes of Glassy and Phyllosilicate Spherules in Al Rais (CR) and Orgueil (CI) Chondrites

    Institute of Scientific and Technical Information of China (English)

    GUAN Yunbin; Michael E. ZOLENSKY

    2004-01-01

    The hydroxyl in phyllosilicate minerals is the most common occurrence of water in primitive meteorites.Direct hydrogen isotopic analysis of this water component using an ion microprobe has been made in some glassy or phyllosilicate spherules from the Al Rais (CR) and Orgueil (CI) chondrites. The spherules from Al Rais show large deuterium excesses (δD = +200 - +800) relative to terrestrial standards, whereas deuterium-enrichments in the spherules from Orgueil are much smaller (δD = +40 - +130‰). The phyllosilicate spherules are products of aqueous alteration of glassy precursors. In A1 Rais the phyllosilicate spherules have relatively higher δD values than the glassy ones, indicating that water introduced during aqueous alteration was deuterium-enriched. The deuterium-enrichments in the phyllosilicate spherules from Orgueil could result from isotopic exchange under thermodynamic conditions within the solar nebula. The much larger δD excesses of the Al Rais spherules, however, cannot be attributed to the similar process;instead, an interstellar origin needs to be invoked.

  3. Origin of organic matter in the early solar system. VII - The organic polymer in carbonaceous chondrites

    Science.gov (United States)

    Hayatsu, R.; Matsuoka, S.; Anders, E.; Scott, R. G.; Studier, M. H.

    1977-01-01

    Degradation techniques, including pyrolysis, depolymerization, and oxidation, were used to study the insoluble polymer from the Murchison C2 chondrite. Oxidation with Cr2O7(2-) or O2/UV led to the identification of 15 aromatic ring systems. Of 11 aliphatic acids identified, three dicarboxylic acids presumably came from hydroaromatic portions of the polymer, whereas eight monocarboxylic acids probably derive from bridging groups or ring substituents. Depolymerization with CF3COO4 yielded some of the same ring systems, as well as alkanes (C1 through C8) and alkenes (C2 through C8), alkyl (C1 through C5) benzenes and naphthalenes, and methyl- or dimethyl -indene, -indane, -phenol, -pyrrole, and -pyridine. All these compounds were detected below 200 C, and are therefore probably indigenous constituents. The properties of the meteoritic polymer were compared with the properties of a synthetic polymer produced by the Fischer-Tropsch reaction. It is suggested that the meteoritic polymer was also produced by surface catalysis.

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

    CERN Document Server

    Nittler, Larry R; Gallino, Roberto; Hoppe, Peter; Nguyen, Ann N; Stadermann, Frank J; Zinner, Ernst K

    2008-01-01

    We report isotopic data for a total of 96 presolar oxide grains found in residues of several unequilibrated ordinary chondrite meteorites. Identified grain types include Al2O3, MgAl2O4, hibonite (CaAl12O19) and Ti oxide. This work greatly increases the presolar hibonite database, and is the first report of presolar Ti oxide. O-isotopic compositions of the grains span previously observed ranges and indicate an origin in red giant and asymptotic giant branch (AGB) stars of low mass (<2.5 MSun) for most grains. Cool bottom processing in the parent AGB stars is required to explain isotopic compositions of many grains. Potassium-41 enrichments in hibonite grains are attributable to in situ decay of now-extinct 41Ca. Inferred initial 41Ca/40Ca ratios are in good agreement with model predictions for low-mass AGB star envelopes, provided that ionization suppresses 41Ca decay. Stable Mg and Ca isotopic ratios of most of the hibonite grains reflect primarily the initial compositions of the parent stars and are gener...

  5. Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

    Science.gov (United States)

    Keil, K.; Fuchs, L. H.

    1971-01-01

    Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

  6. Orbit and dynamic origin of the recently recovered Annama's H5 chondrite

    CERN Document Server

    Trigo-Rodriguez, Josep M; Gritsevich, Maria; Moreno-Ibáñez, Manuel; Bottke, William F; Williams, Iwan; Lupovka, Valery; Dmitriev, Vasily; Kohout, Tomas; Grokhovsky, Victor

    2015-01-01

    We describe the fall of Annama meteorite occurred in the remote Kola Peninsula (Russia) close to Finnish border on April 19, 2014 (local time). The fireball was instrumentally observed by the Finnish Fireball Network. From these observations the strewnfield was computed and two first meteorites were found only a few hundred meters from the predicted landing site on May 29th and May 30th 2014, so that the meteorite (an H4-5 chondrite) experienced only minimal terrestrial alteration. The accuracy of the observations allowed a precise geocentric radiant to be obtained, and the heliocentric orbit for the progenitor meteoroid to be calculated. Backward integrations of the orbits of selected near-Earth asteroids and the Annama meteoroid showed that they rapidly diverged so that the Annama meteorites are unlikely related to them. The only exception seems to be the recently discovered 2014UR116 that shows a plausible dynamic relationship. Instead, analysis of the heliocentric orbit of the meteoroid suggests that the ...

  7. Composition and clues to the origin of refractory metal nuggets extracted from chondritic meteorites

    Science.gov (United States)

    Schwander, D.; Berg, T.; Harries, D.; Schönhense, G.; Ott, U.

    2014-10-01

    Refractory metal nuggets (RMNs) contain elements, such as Os, Ir, Mo, and Ru, which are predicted to condense from a cooling gas of solar composition simultaneously with CAI-minerals. Berg et al. identified a large number of RMNs in acid-resistant residues of the Murchison meteorite and suggested that they are pristine condensates. In extending the work of these authors, we have improved the chemical extraction process to enrich the concentration of RMNs in the residue sample and prepared three additional RMN-rich residues from the chondritic meteorites Murchison, Allende, and Leoville. The results show that, while their origin is clearly solar, the compositions in detail of RMNs from all three meteorites do not match well with a simple condensation model based on equilibrium thermodynamics and ideal solid solution of all metals. Thus, we find that a primary formation by direct condensation, as suggested previously, is unlikely for most of the studied grains and that alternative scenarios should be considered in future work. The results also show that several, but not all, alloys from Allende and Leoville have undergone processes, such as metamorphic oxidation and sulfidization in the meteoritic environment, in which they lost, e.g., W and Mo. For Murchison and several Leoville and Allende RMNs, we propose a pristine nature.

  8. The production rate of cosmogenic 21-Ne in chondrites deduced from 81-Kr measurements

    Science.gov (United States)

    Schultz, L.; Freundel, M.

    1986-01-01

    Cosmogenic Ne-21 is used widely to calculate exposure ages of stone meteorites. In order to do so, the production rate P(21) must be known. This rate, however, is dependent on the chemical composition of the meteorite as well as the mass of, and position within, the meteoroid during its exposure to the cosmic radiation. Even for a mean shielding the production rates determined from measurments of different radionuclides vary by a factor of two. A method that can be used to determine exposure ages of meteorites that avoids shielding and chemical composition corrections is the -81-Kr-Kr-method. However, for chondrites, in many cases, the direct determination of production rates for the Kr isotopes is prevented by the trapped gases and the neutron effects on bromine. Therefore, this method was applied to four eucrite falls and then their 81-Kr-83-Kr-ages were compared to their cosmogenic Ne-21 and Ar-38 concentrations. The eucrites Bouvante-le-Haut, Juvinas, Sioux County, and Stannern were chosen for these measurements because of their similar chemical composition regarding the major elements.

  9. Identification of a Compound Spinel and Silicate Presolar Grain in a Chondritic Interplanetary Dust Particle

    Science.gov (United States)

    Nguyen, A. N.; Nakamura-Messenger, K.; Messenger, S.; Keller, L. P.; Kloeck, W.

    2014-01-01

    Anhydrous chondritic porous interplanetary dust particles (CP IDPs) have undergone minimal parent body alteration and contain an assemblage of highly primitive materials, including molecular cloud material, presolar grains, and material that formed in the early solar nebula [1-3]. The exact parent bodies of individual IDPs are not known, but IDPs that have extremely high abundances of presolar silicates (up to 1.5%) most likely have cometary origins [1, 4]. The presolar grain abundance among these minimally altered CP IDPs varies widely. "Isotopically primitive" IDPs distinguished by anomalous bulk N isotopic compositions, numerous 15N-rich hotspots, and some C isotopic anomalies have higher average abundances of presolar grains (375 ppm) than IDPs with isotopically normal bulk N (<10 ppm) [5]. Some D and N isotopic anomalies have been linked to carbonaceous matter, though this material is only rarely isotopically anomalous in C [1, 5, 6]. Previous studies of the bulk chemistry and, in some samples, the mineralogy of select anhydrous CP IDPs indicate a link between high C abundance and pyroxene-dominated mineralogy [7]. In this study, we conduct coordinated mineralogical and isotopic analyses of samples that were analyzed by [7] to characterize isotopically anomalous materials and to establish possible correlations with C abundance.

  10. A Search for Subkilometer-sized Ordinary Chondrite Like Asteroids in the Main-Belt

    CERN Document Server

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

    2015-01-01

    The size-dependent effects of asteroids on surface regolith and collisional lifetimes suggest that small asteroids are younger than large asteroids. In this study, we performed multicolor main-belt asteroid (MBA) survey by Subaru telescope/Suprime-Cam to search for subkilometer-sized ordinary chondrite (Q-type) like MBAs. The total survey area was 1.5 deg^2 near ecliptic plane and close to the opposition. We detected 150 MBAs with 4 bands (B, V , R, I) in this survey. The range of absolute magnitude of detected asteroids was between 13 and 22 magnitude, which is equivalent to the size range of kilometer to sub-kilometer diameter in MBAs. From this observation, 75 of 150 MBAs with color uncertainty less than 0.1 were used in the spectral type analysis, and two possible Q-type aster- oids were detected. This mean that the Q-type to S-type ratio in MBAs is < 0.05. Meanwhile, the Q/S ratio in near Earth asteroids (NEAs) has been estimated to be 0.5 to 2 (Binzel et al., 2004; Dandy et al., 2003). Therefore, Q-t...

  11. I-Xe Dating: The Time Line of Chondrule Formation and Metamorphism in LL Chondrites

    Science.gov (United States)

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

    2005-01-01

    Refractory inclusions, considered to be the oldest solids formed in the solar nebula. (4567.2 0.6 Ma) [1], are common in many carbonaceous and in some ordinary and enstatite chondrites. High-precision Pb- Pb ages for CAI s and chondrules (from different meteorites) suggested that chondrule formation appeared to have started about 2 Ma later than that of CAIs [1]. However, recent 26Al/26Mg data suggest simultaneous formation of CAI s and chondrules in Allende [2]. The I-Xe ages of CAI s in Allende are about 2 Ma younger than the I-Xe ages of Allende chondrules [3] but, like all chronometers, the I-Xe system records closure time of its particular host phase. In the case of Allende CAI s, the major iodine-bearing phase is sodalite, a secondary phase presumably formed by aqueous alteration, so I-Xe reflects the post-formational processes in these objects. In chondrules the iodine host phases vary and can reflect formation and/or alteration but, to put chondrule ages on a quantative basis, some problems should first be addressed.

  12. Photoluminescence of silicon-vacancy defects in nanodiamonds of different chondrites

    CERN Document Server

    Shiryaev, A A; Semjonova, L F; Khomich, A A; Vlasov, I I

    2015-01-01

    Photoluminescence spectra show that silicon impurity is present in lattice of some nanodiamond grains (ND) of various chondrites as a silicon-vacancy (SiV) defect. The relative intensity of the SiV band in the diamond-rich separates depends on chemical composition of meteorites and on size of ND grains. The strongest signal is found for the size separates enriched in small grains; thus confirming our earlier conclusion that the SiV defects preferentially reside in the smallest (less than 2 nm) grains. The difference in relative intensities of the SiV luminescence in the diamond-rich separates of individual meteorites are due to variable conditions of thermal metamorphism of their parent bodies and/or uneven sampling of nanodiamonds populations. Annealing of separates in air eliminates surface sp2-carbon, consequently, the SiV luminescence is enhanced. Strong and well-defined luminescence and absorption of the SiV defect is a promising feature to locate cold (< 250 {\\deg}C) nanodiamonds in space.

  13. HRTEM and EFTEM Studies of Phyllosilicate-Organic Matter Associations in Matrix and Dark Inclusions in the EET92042 CR2 Carbonaceous Chondrite

    Science.gov (United States)

    Abreu, Neyda M.; Brearley, Adrian J.

    2005-01-01

    Based on petrologic and isotopic observations, the CR chondrites represent one of the most primitive carbonaceous chondrite groups. The organic matter in CR chondrite matrices is considered to be among the most ancient carbonaceous matter known, potentially providing a link between organic matter in the interstellar medium and our solar system [1]. However, the organic chemistry of CR chondrites may be complicated by the fact that these meteorites have undergone moderate secondary alteration, which potentially overprints primordial features [2]. Although the general effects of this alteration have been documented [2], the details of the fine-grained mineralogy and alteration styles of CR matrices are not fully understood. Here we present TEM observations of matrix in EET 92042, a CR chondrite that contains particularly primitive insoluble organic matter [1]. Preliminary studies [3] determined that EET 92042 matrix is heterogeneous in terms of mineralogy, texture, and petrographic fabric on the micron scale. EET 92042 contains magnetite-rich regions, foliated matrix and dark inclusions (DIs). Some chondrules show fine-grained rims, similar to those described by [4].

  14. Precise determination of rare earth elements, thorium and uranium in chondritic meteorites by inductively coupled plasma mass spectrometry. A comparative study with radiochemical neutron activation analysis

    International Nuclear Information System (INIS)

    An inductively coupled plasma mass spectrometry (ICP-MS) procedure for determining trace amounts of rare earth elements (REEs), Th and U in chondritic meteorites (chondrites) is presented. As chondrites have low contents of these elements (10-2 to 10-4xcrustal rock averages), the procedure was designed to be performed in as small a scale as possible in order to reduce the procedural blank. Serious matrix effects (ion suppression) may be caused by high Fe contents (20-35 wt.), which could be eliminated by applying appropriate internal standards (Rh for Y, In and Tl for lanthanides, and Bi for Th and U) and dilution factors (104 for Y and 103 for the rest of elements). Radiochemical neutron activation analysis (RNAA) was also applied for determining 10 REEs (La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb and Lu) in chondrites. It is found that both ICP-MS and RNAA have comparable detection limits for REEs. ICP-MS, however, has the great advantage that all REEs (including Y), Th and U can be determined with similar precision. Three Antarctic chondrites for which some anomalous REE abundances had been reported by RNAA, were also analyzed by ICP-MS but no anomalies were found, which implies the limitation of RNAA data in discussing the REE abundances in detail

  15. Bidirectional reflectance spectroscopy of carbonaceous chondrites: Implications for water quantification and primary composition

    Science.gov (United States)

    Garenne, A.; Beck, P.; Montes-Hernandez, G.; Brissaud, O.; Schmitt, B.; Quirico, E.; Bonal, L.; Beck, C.; Howard, K. T.

    2016-01-01

    In this study, we measured bidirectional reflectance spectra (0.5-4.0 μm) of 24 CMs, five CRs, one CI, one CV, and one C2 carbonaceous chondrites. These meteorites are known to have experienced an important variability in their relative degrees of aqueous alteration degree (Rubin et al. [2007]. Geochim. Cosmochim. Acta 71, 2361-2382; Howard et al. [2009]. Geochim. Cosmochim. Acta 73, 4576-4589; Howard et al. [2011]. Geochim. Cosmochim. Acta 75, 2735-2751; Alexander et al. [2013]. Geochim. Cosmochim. Acta 123, 244-260). These measurements were performed on meteorite powders inside an environmental cell under a primary vacuum and heated at 60 °C in order to minimize adsorbed terrestrial water. This protocol allows controlling of atmospheric conditions (i.e. humidity) in order to avoid contamination by terrestrial water. We discuss various spectral metrics (e.g. reflectance, band depth, single-scattering albedo, …) in the light of recent bulk composition characterization (Howard et al. [2009]. Geochim. Cosmochim. Acta 73, 4576-4589; Howard et al. [2015]. Geochim. Cosmochim. Acta 149, 206-222; Alexander et al. [2012]. Science 337, 721; Beck et al. [2014]. Icarus 229, 263-277; Garenne et al. [2014]. Geochim. Cosmochim. Acta 137, 93-112). This study reveals variability of reflectance among meteorite groups. The reflectance is not correlated with carbon or hydrogen abundance neither with measured grain size distribution. We suggest that it is rather controlled by the nature of accreted components, in particular the initial matrix/chondrule proportion. Band depth, integrated band depth, mean optical path length, normalized optical path length, effective single-particle absorption thickness were calculated on the so called 3-μm band for reflectance spectra and for single scattering albedo spectra. They were compared with hydrated phase proportions from previous study on the same meteorites by thermogravimetric analyses and infrared spectroscopy in transmission. We find

  16. Impact melting of the largest known enstatite meteorite: Al Haggounia 001, a fossil EL chondrite

    Science.gov (United States)

    Rubin, Alan E.

    2016-09-01

    Al Haggounia 001 and paired specimens (including Northwest Africa [NWA] 2828 and 7401) are part of a vesicular, incompletely melted, EL chondrite impact melt rock with a mass of ~3 metric tons. The meteorite exhibits numerous shock effects including (1) development of undulose to weak mosaic extinction in low-Ca pyroxene; (2) dispersion of metal-sulfide blebs within silicates causing "darkening"; (3) incomplete impact melting wherein some relict chondrules survived; (4) vaporization of troilite, resulting in S2 bubbles that infused the melt; (5) formation of immiscible silicate and metal-sulfide melts; (6) shock-induced transportation of the metal-sulfide melt to distances >10 cm (7) partial resorption of relict chondrules and coarse silicate grains by the surrounding silicate melt; (8) crystallization of enstatite in the matrix and as overgrowths on relict silicate grains and relict chondrules; (9) crystallization of plagioclase from the melt; and (10) quenching of the vesicular silicate melt. The vesicular samples lost almost all of their metal during the shock event and were less susceptible to terrestrial weathering; in contrast, the samples in which the metal melt accumulated became severely weathered. Literature data indicate the meteorite fell ~23,000 yr ago; numerous secondary phases formed during weathering. Both impact melting and weathering altered the meteorite's bulk chemical composition: e.g., impact melting and loss of a metal-sulfide melt from NWA 2828 is responsible for bulk depletions in common siderophile elements and in Mn (from alabandite); weathering of oldhamite caused depletions in many rare earth elements; the growth of secondary phases caused enrichments in alkalis, Ga, As, Se, and Au.

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

    Science.gov (United States)

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

    2004-01-01

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

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

    Science.gov (United States)

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

    2006-12-01

    Although we recently classified NWA 2828 as an aubrite [1], our examination of new material (now comprising over 120 stones totaling >27 kg) requires revision of that classification. New information on the find site in Algeria indicates that these stones were excavated from a subsurface deposit, and we have found terrestrial rhyolite pebbles and sandy matrix attached to several NWA 2828 stones (see images at http://www.ess.washington.edu/meteoritics). Thus this is a rare example of a paleo-meteorite or 'fossil' meteorite. Some stones contain sparse (stone contain up to 6.5 wt.% Ni. These secondary minerals signify terrestrial alteration of primary metal, sulfides, phosphides, nitrides and glass in an ancient fluvial and/or acidic lacustrine environment. The dominant primary phase in NWA 2828 is enstatite (En98.4Wo1.4), which forms stubby prismatic grains (lacking polysynthetic twinning indicative of inverted clinoenstatite [cf., 1]). Our original classification was based on a very small specimen of an apparently igneous-textured rock, but the discovery of chondrules and the absence of twinned enstatite now suggests that it is instead an unequilibrated enstatite chondrite. Additional primary phases noted previously [1] are sodic plagioclase (An14- 15Or3-4), troilite, graphite, daubreelite, alabandite, oldhamite, schreibersite, glass and very rare kamacite. The well-formed, round chondrules containing glass coupled with the unrecrystallized matrix lead us to re-classify NWA 2828 as an EL3 chondrite. We also must revise our opinion [1] about the relationship between NWA 2828 and material classified as EL chondrites NWA 2965 and NWA 2736, which evidently come from the more extensively weathered top of the same ancient conglomerate layer as NWA 2828. [1] Irving A.J. et al. (2006) 69th Met. Soc. Mtg., #5264 (MAPS 41 Suppl., A84)

  19. Oxygen Isotope Evidence for the Relationship between CM and CO Chondrites: Could they Both Coexist on a Single Asteroid

    Science.gov (United States)

    Greenwood, R. C.; Howard, K. T.; Franchi, I. A.; Zolensky, M. E.; Buchanan, P. C.; Gibson, J. M.

    2014-01-01

    Water played a critical role in the early evolution of asteroids and planets, as well as being an essential ingredient for life on Earth. However, despite its importance, the source of water in the inner solar system remains controversial. Delivery of water to Earth via comets is inconsistent with their relatively elevated D/H ratios, whereas carbonaceous chondrites (CCs) have more terrestrial-like D/H ratios [1]. Of the eight groups into which the CCs are divided, only three (CI, CM, CR) show evidence of extensive aqueous alteration. Of these, the CMs form the single most important group, representing 34% of all CC falls and a similar percentage of finds (Met. Bull. Database). CM material also dominates the population of CC clasts in extraterrestrial samples [2, 3]. The Antarctic micrometeorites population is also dominated by CM and CI-like material and similar particles may have transported water and volatiles to the early Earth [4]. CCs, and CMs in particular, offer the best opportunity for investigating the evolution of water reservoirs in the early solar system. An important aspect of this problem involves identifying the anhydrous silicate component which co-accreted with ice in the CM parent body. A genetic relationship between the essentially anhydrous CO group and the CMs was proposed on the basis of oxygen isotope evidence [5]. However, previous CM whole-rock oxygen isotope data scattered about a line of approximately 0.5 that did not intersect the field of CO chondrites [5]. Here we discuss new oxygen isotope data which provides additional constraints on the relationship between CO and CM chondrites.

  20. Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle

    Science.gov (United States)

    Teng, F.-Z.; Wadhwa, M.; Helz, R.T.

    2007-01-01

    To investigate whether magnesium isotopes are fractionated during basalt differentiation, we have performed high-precision Mg isotopic analyses by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) on a set of well-characterized samples from Kilauea Iki lava lake, Hawaii, USA. Samples from the Kilauea Iki lava lake, produced by closed-system crystal-melt fractionation, range from olivine-rich cumulates to highly differentiated basalts with MgO content ranging from 2.37 to 26.87??wt.%. Our results demonstrate that although these basalts have diverse chemical compositions, mineralogies, crystallization temperatures and degrees of differentiation, their Mg isotopic compositions display no measurable variation within the limits of our external precision (average ??26Mg = - 0.36 ?? 0.10 and ??25Mg = - 0.20 ?? 0.07; uncertainties are 2SD). This indicates that Mg isotopic fractionation during crystal-melt fractionation at temperatures of ??? 1055????C is undetectable at the level of precision of the current investigation. Calculations based on our data suggest that at near-magmatic temperatures the maximum fractionation in the 26Mg/24Mg ratio between olivine and melt is 0.07???. Two additional oceanic basalts, two continental basalts (BCR-1 and BCR-2), and two primitive carbonaceous chondrites (Allende and Murchison) analyzed in this study have Mg isotopic compositions similar to the Kilauea Iki lava lake samples. In contrast to a recent report [U. Wiechert, A.N. Halliday, Non-chondritic magnesium and the origins of the inner terrestrial planets, Earth and Planetary Science Letters 256 (2007) 360-371], the results presented here suggest that the Bulk Silicate Earth has a chondritic Mg isotopic composition. ?? 2007.

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

    Science.gov (United States)

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

    2012-01-01

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

  2. UV to far-IR reflectance spectra of carbonaceous chondrites. I. Implications for remote characterization of dark primitive asteroids targeted by sample-return missions

    CERN Document Server

    Trigo-Rodriguez, Josep M; Llorca, Jordi; Fornasier, Sonia; Barucci, Maria A; Belskaya, Irina; Martins, Zita; Rivkin, Andy S; Dotto, Elisabetta; Madiedo, José M; Alonso-Azcárate, Jacinto

    2013-01-01

    We analyze here a wide sample of carbonaceous chondrites from historic falls (e.g. Allende, Cold Bokkeveld, Kainsaz, Leoville, Murchison, Murray and Orgueil), and from NASA Antarctic collection in order to get clues on the role of aqueous alteration in promoting the reflectance spectra diversity evidenced in the most primitive chondrite groups. We particularly focus in the identification of spectral features and behavior that can be used to remotely identify primitive carbonaceous asteroids. The selected meteorite specimens are a sample large enough to exemplify how laboratory reflectance spectra of rare groups of carbonaceous chondrites exhibit distinctive features that can be used to remotely characterize the spectra of primitive asteroids. Our spectra cover the full electromagnetic spectrum from 0.2 to 25 microns by using two spectrometers. First one is a UV-NIR spectrometer that covers the 0.2 to 2 microns window, while the second one is an Attenuated Total Reflectance IR spectrometer covering the 2 to 25...

  3. P-O-rich sulfide phase in CM chondrites: Constraints on its origin on the CM parent body

    Science.gov (United States)

    Zhang, Ai-Cheng; Itoh, Shoichi; Yurimoto, Hisayoshi; Hsu, Wei-Biao; Wang, Ru-Cheng; Taylor, Lawrence A.

    2016-01-01

    CM chondrites are a group of primitive meteorites that have recorded the alteration history of the early solar system. We report the occurrence, chemistry, and oxygen isotopic compositions of P-O-rich sulfide phase in two CM chondrites (Grove Mountains [GRV] 021536 and Murchison). This P-O-rich sulfide is a polycrystalline aggregate of nanometer-size grains. It occurs as isolated particles or aggregates in both CM chondrites. These grains, in the matrix and in type-I chondrules from Murchison, were partially altered into tochilinite; however, grains enclosed by Ca-carbonate are much less altered. This P-O-rich sulfide in Murchison is closely associated with magnetite, FeNi phosphide, brezinaite (Cr3S4), and eskolaite (Cr2O3). In addition to sulfur as the major component, this sulfide contains ~6.3 wt% O, ~5.4 wt% P, and minor amounts of hydrogen. Analyses of oxygen isotopes by SIMS resulted in an average δ18O value of -22.5 ‰ and an average Δ17O value of 0.2 ± 9.2 ‰ (2σ). Limited variations in both chemical compositions and electron-diffraction patterns imply that the P-O-rich sulfide may be a single phase rather than a polyphase mixture. Several features indicate that this P-O-rich sulfide phase formed at low temperature on the parent body, most likely through the alteration of FeNi metal (a) close association with other low-temperature alteration products, (b) the presence of hydrogen, (c) high Δ17O values and the presence in altered mesostasis of type-I chondrules and absence in type-II chondrules. The textural relations of the P-O-rich sulfide and other low-temperature minerals reveal at least three episodic-alteration events on the parent body of CM chondrites (1) formation of P-O-rich sulfide during sulfur-rich aqueous alteration of P-rich FeNi metal, (2) formation of Ca-carbonate during local carbonation, and (3) alteration of P-O-rich sulfide and formation of tochilinite during a period of late-stage intensive aqueous alteration.

  4. Mineralogy and Petrography of MIL 090001, a Highly Altered CV Chondrite from the Reduced Sub-Group

    Science.gov (United States)

    Keller, Lindsay P.

    2011-01-01

    MIL 090001 is a large (greater than 6 kg) CV chondrite from the reduced subgroup (CV(sub red)) that was recovered during the 2009-2010 ANSMET field season [1]. The CV(sub red) subgroup meteorites retain primitive characteristics and have escaped the Na and Fe meta-somatism that affected the oxidized (CV(sub ox)) subgroups. MIL 090001 is, however, reported to be altered [1], and thus a major objective of this study is to characterize its mineralogy and petrography and the extent of the alteration.

  5. Widespread oxidized and hydrated amorphous silicates in CR chondrites matrices: Implications for alteration conditions and H2 degassing of asteroids

    Science.gov (United States)

    Le Guillou, Corentin; Changela, Hitesh G.; Brearley, Adrian J.

    2015-06-01

    The CR chondrites carry one of the most pristine records of the solar nebula materials that accreted to form planetesimals. They have experienced very variable degrees of aqueous alteration, ranging from incipient alteration in their matrices to the complete hydration of all of their components. In order to constrain their chemical alteration pathways and the conditions of alteration, we have investigated the mineralogy and Fe oxidation state of silicates in the matrices of 8 CR chondrites, from type 3 to type 1. Fe-L edge X-ray Absorption Near Edge Structure (XANES) was performed on matrix FIB sections using synchrotron-based scanning transmission X-ray microscopy (STXM). The Fe3+ / ∑ Fe ratio of submicron silicate particles was obtained and coordinated with TEM observations. In all the least altered CR chondrites (QUE 99177, EET 87770, EET 92042, LAP 02342, GRA 95229 and Renazzo), we find that the matrices consist of abundant submicron Fe-rich hydrated amorphous silicate grains, mixed with nanometer-sized phyllosilicates. The Fe3+ / ∑ Fe ratios of both amorphous and nanocrystalline regions are very high with values ranging from 68 to 78%. In the most altered samples (Al Rais and GRO 95577), fine-grained phyllosilicates also have a high Fe3+ / ∑ Fe ratio (around 70%), whereas the coarse, micrometer-sized phyllosilicates are less oxidized (down to 55%) and have a lower iron content. These observations suggest the following sequence: submicron Fe2+-amorphous silicate particles were the building blocks of CR matrices; after accretion they were quickly hydrated and oxidized, leading to a metastable, amorphous gel-like phase. Nucleation and growth of crystalline phyllosilicates was kinetically-limited in most type 3 and 2 CRs, but increased as alteration became more extensive in Al Rais and GRO 95577. The decreasing Fe3+ / ∑ Fe ratio is interpreted as a result of the transfer of Fe3+ from silicates to oxides during growth, while aqueous alteration progressed

  6. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.

    2012-01-01

    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

  7. The CO chondrites: Major recent Antarctic finds, their thermal and radiation history, and describing the metamorphic history of members of the class

    Science.gov (United States)

    Sears, Derek W. G.

    2016-09-01

    Thermoluminescence (TL) properties of 29 CO chondrites from the Miller Range (MIL) and five chondrites from the Dominion Range (DOM) have been measured. MIL has a relatively strong natural TL signal (19.6 ± 14.7 krad), while some of the DOM samples have a very weak natural TL signal (fragments represent more than one fall. The induced TL data for the MIL samples studied here are consistent with them all being from a single fragmented meteorite. Small (50 mg) chips have TL properties similar to 500 mg chips, so that the smaller chips are representative, although samples taken from original masses less than ∼2 g have low natural TL suggesting that they were heated during atmospheric fall. The properties of CO chondrites are reviewed in terms of their petrologic types. Correlations between TL sensitivity, the most quantitative technique for evaluating metamorphic alteration in CO chondrites, and data for olivine composition and heterogeneity, matrix composition, inert gas content, metal composition (Ni, Co, and Cr in the kamacite), bulk carbon, C and O isotopes, graphite ordering, spectral reflectance at 0.8 μm, and textural characteristics of the ameboid olivine and Ca-rich inclusions are examined. The petrographic types appear to be largely metamorphic in origin with perhaps a minor role for metasomatism. Contrary to recent proposals it is here argued that petrologic type definitions should (1) be specific enough to be meaningful, but broad enough to be simple in application and robust to new developments, (2) be descriptive and not interpretative, (3) should not oversimplify and obscure important class-to-class differences, and (4) take account of all the available information, while avoiding reliance on any one technique or single observation whose application is based on interpretation. With these considerations in mind the petrographic type definitions for CO chondrites are restated and the petrologic type of 3.2 assigned to both the MIL and DOM CO

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

    Science.gov (United States)

    Koeberl, Christian; Shukolyukov, Alex; Lugmair, Guenter

    2004-01-01

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

  9. Whole-rock Al-Mg systematics of amoeboid olivine aggregates from the oxidized CV3 carbonaceous chondrite Allende

    DEFF Research Database (Denmark)

    Olsen, M.B.; Krot, A.N.; Larsen, Kirsten Kolbjørn;

    2011-01-01

    We report on mineralogy, petrography, and whole-rock Al- Mg systematics of eight amoeboid olivine aggregates (AOAs) from the oxidized CV chondrite Allende. The AOAs consist of forsteritic olivine, opaque nodules, and variable amounts of Ca,Al-rich inclusions (CAIs) of different types, and show......, and Si were introduced, whereas Ca was removed from AOAs and used to form the Ca,Fe-rich silicate rims around AOAs. The whole-rock Al- Mg systematics of the Allende AOAs plot above the isochron of the whole-rock Allende CAIs with a slope of (5.23±0.13)×10 reported by Jacobsen et al. (2008). In contrast......, whole-rock Al- Mg isotope systematics of CAIs and AOAs from the reduced CV chondrite Efremovka define a single isochron with a slope of (5.25±0.01)×10 (Larsen et al. 2011). We infer that the excesses in Mg present in Allende AOAs are due to their late-stage open-system metasomatic alteration. Thus...

  10. Photophoretic separation of metals and silicates: the formation of Mercury like planets and metal depletion in chondrites

    CERN Document Server

    Wurm, Gerhard; Rauer, Heike

    2013-01-01

    Mercury's high uncompressed mass density suggests that the planet is largely composed of iron, either bound within metal (mainly Fe-Ni), or iron sulfide. Recent results from the MESSENGER mission to Mercury imply a low temperature history of the planet which questions the standard formation models of impact mantle stripping or evaporation to explain the high metal content. Like Mercury, the two smallest extrasolar rocky planets with mass and size determination, CoRoT-7b and Kepler-10b, were found to be of high density. As they orbit close to their host stars this indicates that iron rich inner planets might not be a nuisance of the solar system but be part of a general scheme of planet formation. From undifferentiated chondrites it is also known that the metal to silicate ratio is highly variable which must be ascribed to pre-planetary fractionation processes. Due to this fractionation most chondritic parent bodies - most of them originated in the asteroid belt - are depleted in iron relative to average solar...

  11. Mineralogy, reflectance spectra, and physical properties of the Chelyabinsk LL5 chondrite, insight into shock induced changes in asteroid regoliths

    CERN Document Server

    Kohout, Tomas; Grokhovsky, Victor I; Yakovlev, Grigoriy A; Haloda, Jakub; Halodova, Patricie; Michallik, Radoslaw M; Penttilä, Antti; Muinonen, Karri

    2014-01-01

    The mineralogy and physical properties of Chelyabinsk meteorites (fall, February 15, 2013) are presented. Three types of meteorite material are present, described as the light-colored, dark-colored, and impact-melt lithologies. All are of LL5 composition with the impact-melt lithology being close to whole-rock melt and the dark-colored lithology being shock-darkened due to partial melting of iron metal and sulfides. This enables us to study the effect of increasing shock on material with identical composition and origin. Based on the magnetic susceptibility, the Chelyabinsk meteorites are richer in metallic iron as compared to other LL chondrites. The measured bulk and grain densities and the porosity closely resemble other LL chondrites. Shock darkening does not have a significant effect on the material physical properties, but causes a decrease of reflectance and decrease in silicate absorption bands in the reflectance spectra. This is similar to the space weathering effects observed on asteroids. However, ...

  12. Carbon and oxygen isotope composition of carbonates from an L6 chondrite: Evidence for terrestrial weathering from the Holbrook meteorite

    Science.gov (United States)

    Socki, R. A.; Gibson, E. K.; Jull, A. J. T.; Karlsson, H. R.

    1991-01-01

    Terrestrial weathering in meteorites is an important process which alters pristine elemental and isotopic abundances. The Holbrook L6 chondrite fell in 1912. Material was recovered at the time of the fall, in 1931, and 1968. The weathering processes operating on the freshly fallen meteorite in a semi-arid region of northeastern Arizona have been studied after a ground residence of 19 and 56 years. It has been shown that a large portion of the carbonate material in 7 Antarctic ordinary chondrites either underwent extensive isotopic exchange with atmospheric CO2, or formed recently in the Antarctic environment. In fact it has been demonstrated that hydrated Mg-carbonates, nesquehonite and hydromagnesite, formed in less than 40 years on LEW 85320. In order to help further constrain the effects of terrestrial weathering in meteorites, the carbon and oxygen isotopes extracted from carbonates of three different samples of Holbrook L6: a fresh sample at the time of the fall in 1912, a specimen collected in 1931, and a third specimen collected at the same site in 1968.

  13. Organic Analysis of Catalytic Fischer-Tropsch Type Synthesis Products: Are they Similar to Organics in Chondritic Meteorites?

    Science.gov (United States)

    Yazzie, Cyriah A.; Locke, Darren R.; Johnson, Natasha M.

    2014-01-01

    Fischer-Tropsch Type (FTT) synthesis of organic compounds has been hypothesized to occur in the early solar nebula that formed our Solar System. FTT is a collection of abiotic chemical reactions that convert a mixture of carbon monoxide and hydrogen over nano-catalysts into hydrocarbons and other more complex aromatic compounds. We hypothesized that FTT can generate similar organic compounds as those seen in chondritic meteorites; fragments of asteroids that are characteristic of the early solar system. Specific goals for this project included: 1) determining the effects of different FTT catalyst, reaction temperature, and cycles on organic compounds produced, 2) imaging of organic coatings found on the catalyst, and 3) comparison of organic compounds produced experimentally by FTT synthesis and those found in the ordinary chondrite LL5 Chelyabinsk meteorite. We used Pyrolysis Gas Chromatography Mass Spectrometry (PY-GCMS) to release organic compounds present in experimental FTT and meteorite samples, and Scanning Electron Microscopy (SEM) to take images of organic films on catalyst grains.

  14. Ca-carbonate in the Orgueil (CI) carbonaceous chondrite: Mineralogy, microstructure and implications for parent body history

    Science.gov (United States)

    Lee, Martin R.; Nicholson, Kirsty

    2009-04-01

    The Orgueil CI carbonaceous chondrite is a breccia and some of its constituent clasts contain Ca-carbonate grains whose mineralogy is undetermined, but may yield new information on the history of its asteroidal or cometary parent body. Characterisation of one such clast shows that in addition to Ca-carbonate it contains magnetite, olivine and orthopyroxene grains that are supported within a finely crystalline saponite-serpentine-ferrihydrite groundmass. The Ca-carbonate grains are typically rounded, less than 10 μm in diameter, and backscatter Kikuchi patterns identify all those analysed as calcite. Electron backscatter diffraction orientation contrast maps show that most calcites have sub-μm sized e-twins, some of which are cut by corroded grain margins. These microstructures demonstrate that the clast experienced very mild shock during aqueous alteration and probably accompanying impact 'gardening' of the parent body regolith. The sample studied hosts several other millimeter sized clasts and a fine grained clastic matrix that are free of Ca-carbonate, olivine and orthopyroxene although can contain apatite, dolomite and pyrrhotite. Within one of these clasts is a network of phyllosilicate-magnetite veins that are inferred to have acted as fluid flow conduits during parent body aqueous alteration. Sulphur-rich reaction rims within the same clast are likely to have formed during post-fall remobilization and crystallization of pre-terrestrial sulphates. This study provides good evidence for alteration of the CI carbonaceous chondrites in a dynamic parent body regolith.

  15. Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Tatsunori, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2015-01-01

    Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

  16. Mineral associations and character of isotopically anomalous organic material in the Tagish Lake carbonaceous chondrite

    Science.gov (United States)

    Zega, Thomas J.; Alexander, Conel M. O.'D.; Busemann, Henner; Nittler, Larry R.; Hoppe, Peter; Stroud, Rhonda M.; Young, Andrea F.

    2010-10-01

    We report a coordinated analytical study of matrix material in the Tagish Lake carbonaceous chondrite in which the same small (⩽20 μm) fragments were measured by secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), electron energy-loss spectroscopy (EELS), and X-ray absorption near-edge spectroscopy (XANES). SIMS analysis reveals H and N isotopic anomalies (hotspots), ranging from hundreds to thousands of nanometers in size, which are present throughout the fragments. Although the differences in spatial resolution of the SIMS techniques we have used introduce some uncertainty into the exact location of the hotspots, in general, the H and N isotopic anomalies are spatially correlated with C enrichments, suggesting an organic carrier. TEM analysis, enabled by site-specific extraction using a focused-ion-beam scanning-electron microscope, shows that the hotspots contain an amorphous component, Fe-Ni sulfides, serpentine, and mixed-cation carbonates. TEM imaging reveals that the amorphous component occurs in solid and porous forms, EDS indicates that it contains abundant C, and EELS and XANES at the C K edge reveal that it is largely aromatic. This amorphous component is probably macromolecular C, likely the carrier of the isotopic anomalies, and similar to the material extracted from bulk samples as insoluble organic matter. However, given the large sizes of some of the hotspots, the disparity in spatial resolution among the various techniques employed in our study, and the phases with which they are associated, we cannot entirely rule out that some of the isotopic anomalies are carried by inorganic material, e.g., sheet silicates. The isotopic composition of the organic matter points to an initially primitive origin, quite possibly within cold interstellar clouds or the outer reaches of the solar protoplanetary disk. The association of organic material with secondary phases, e.g., serpentine

  17. Mineralogy, Degree of Brecciation, and Aqueous Alteration of CI Chondrites Orgueil, Ivuna, and Alais

    Science.gov (United States)

    Endress, M.; Bischoff, A.

    1993-07-01

    The textural and mineralogical properties of the CI-chondrites Orgueil, Ivuna, and Alais were studied by electron microscopy in order to obtain new insights into the history and evolution of the CI parent body. Degree of Brecciation. The electron optical investigation of Orgueil, Ivuna, and Alais revealed that the three samples experienced different degrees of brecciation: (1) Orgueil is highly brecciated. It consists of abundant clastic matrix (clasts usually modal abundance of carbonates (up to 10 vol%) and a lack of sulfates; the second is enriched in sulfates, but contains no carbonates, and the third lithology can be characterized by its high abundance of coarse-grained phyllosilicate fragments. Mineralogy. As phases >5 micrometers in size we observed magnetite, sulfides, carbonates, Ca-phosphate, olivine (Fachunks (up to 300 micrometers in size; especially in Ivuna). The Ca-phosphates contain small amounts of FeO (1-2 wt%), MnO (1 wt%), and Na2O (up to 3 wt%). Sulfates mostly occur as vein fillings in Alais (mainly gypsum) and Orgueil (mainly epsomite), but such veins are lacking in our Ivuna sample. Here, single sulfate grains (<10 micrometers) are rarely dispersed throughout the matrix. Aqueous alteration. Based on a study of Orgueil and Y-82162, [1,2] proposed a model, that during late stage aqueous alteration Fe-rich solutions readily decompose coarse-grained phyllosilicate clusters to fine-grained phyllosilicates and ferrihydrite and that contemporaneously sulfates were formed. Since Y-82162 contains abundant phyllosilicate clusters, but no ferrihydrite and no sulfate, Y-82162 should be less altered than Orgueil [1]. Considering this model we can distinguish between Orgueil, Ivuna, and Alais based on the degree of alteration. The abundance of phyllosilicate fragments is low in Orgueil, but high in Ivuna and Alais. In contrast to Orgueil, Ivuna contains no ferrihydrite [3,4] and very little sulfate. Therefore, the degree of aqueous alteration appears to

  18. Hydrothermal venting on carbonaceous chondritic elevations on 1 Ceres and 4 Vesta

    Science.gov (United States)

    Hoffmann, Martin; Nathues, Andreas; Platz, Thomas; Thangjam, Guneshwar

    2016-04-01

    Framing Camera images of the Dawn spacecraft [1] led to the discovery of recent geologic activity on Ceres, including deposition of salts, formation of near surface haze [2], and impact associated spectral diversity. More detailed analyses revealed widespread flow features, partly composed of granular material, but also indicating sites of fluidized areas of the surface and sub-surface. The unexpected discovery of deposits of carbonaceous chondritic material on Vesta associated with indications of considerable amounts of volatiles at large impact structures hint at similar processes [3, 4]. Near large crater walls on both proto-/dwarf-planets, montes and domes appear to be associated with uplift and even release of water-driven material including salts and clays [5, 6]. We report morphologic and color band spectroscopic characteristics of selected key features on 1 Ceres and 4 Vesta which demonstrate this context. A first analysis indicates compositional differences of the proportion of the content of salts and phyllosilicates, e. g. on the different elevations of the primary and secondary spots in Occator and some flow features. The distribution and diversity of these color features is further characterized by a comparison with more widespread properties on the whole surface. During this investigation, not only the link between salt deposits and different types of materials at the centers of activity could be described, but we also offer an intriguing new interpretation of one of the most prominent surface features of Vesta: Lucaria Tholus. Several analogies with similar features and properties of Mars [7] further support the view of a related origin. References: [1] Sierks, H. et al., Space Sci. Rev., 163, 263-327, 2011. [2] Nathues, A. et al., Nature 528, 237-240, 2015. [3] Reddy, V. et al. Icarus, 221, 544-559, 2012. [4] Scully, J. E. C. et al., EPSC Abstracts 8, 2013-242-2, 2013. [5] Platz, T. et al. LPSC 2016 [6] Ruesch, O. et al. LPSC 2016 [7] Platz, T. et

  19. Isotopically uniform, 16O-depleted calcium, aluminum-rich inclusions in CH and CB carbonaceous chondrites

    Science.gov (United States)

    Krot, Alexander N.; Nagashima, Kazuhide; Petaev, Michail I.

    2012-04-01

    In situ oxygen-isotope measurements of calcium-aluminum-rich inclusions (CAIs) from the metal-rich carbonaceous chondrites Isheyevo (CH/CB-like), Acfer 214 paired with Acfer 182 (CH), QUE 94411 paired with QUE 94627 (CBb), and Hammadah al Hamra 237 (CBb) revealed the presence of a common population of igneous, isotopically uniform, 16O-depleted inclusions: Δ17O (average ± 2 standard deviations) = -7 ± 4‰, -6 ± 5‰, and -8 ± 3‰, respectively. All CAIs from CBs and a significant fraction of those from CHs and Isheyevo are 16O-depleted. Most of the 16O-depleted CAIs consist of Ti-poor Al-diopside, spinel, melilite, and forsterite and surrounded by a single- and double-layered rim of forsterite ± diopside. The 16O-depleted CAIs composed of hibonite, grossite, melilite, and spinel, and surrounded by the multilayered melilite + diopside ± forsterite rims are less common. Some of the 16O-depleted refractory igneous inclusions composed of Al-diopside, forsterite, and ±spinel have chondrule-like textures (skeletal or barred). They are mineralogically most similar to Al-diopside-rich chondrules found in metal-rich carbonaceous chondrites and composed of Al-diopside, forsterite, Al-rich low-Ca pyroxene, ±glassy mesostasis, and ±spinel, suggesting there is a continuum between these objects. We suggest that (i) most of the isotopically uniform and 16O-depleted CAIs resulted from remelting of pre-existing, possibly 16O-rich refractory inclusions. The remelting may have occurred during formation of the magnesian, non-porphyritic (cryptocrystalline and skeletal) chondrules in CHs, CBs, and Isheyevo either by an unspecified, late, single-stage, highly-energetic event or in an impact-generated plume previously hypothesized for their origin; both mechanisms probably occurred in the solar nebula (i.e., in the presence of the nebula gas). The forsterite ± pyroxene rims around 16O-depleted CAIs may have resulted from evaporation-recondensation of silicon and magnesium

  20. The appearance of Carbonaceous Chondrites on (1) Ceres from observations by the Dawn Framing Camera

    Science.gov (United States)

    Schäfer, Tanja; Schäfer, Michael; Mengel, Kurt; Cloutis, Edward A.; Izawa, Matthew R. M.; Thangjam, Guneshwar; Hoffmann, Martin; Platz, Thomas; Nathues, Andreas; Kallisch, Jan; Ripken, Joachim; Russel, Christopher T.

    2016-04-01

    NASA's Dawn spacecraft reached dwarf planet Ceres in March 2015 and started data acquisition using three different instruments. These are the Framing Camera (FC; [1]), the Visible & Infrared Spectrometer (VIR; [2]), and the Gamma Ray and Neutron Detector (GRaND; [3]). In our work we focus on the potential appearance of carbonaceous chondritic (CC) material on the cerean surface using Dawn FC color mosaics covering the VIS/NIR wavelength region. In preparation of the Dawn arrival at Ceres, a discrimination scheme for CC groups using FC color ratios was developed by [4] and is based on 121 CC laboratory spectra compiled from RELAB. As the cerean surface material mainly differs by its spectral slope over the whole FC wavelength range (0.44-0.97 μm), we classified the color mosaics by this parameter. We applied the CC discrimination scheme only to those regions on the cerean surface (more than 90 %) which exhibit spectral slopes ≥ -1 % reflectance per μm to exclude the strongly negative sloped regions of large young craters such as Occator, Haulani, and Oxo. These are not likely to be similar to pure CC material as can be seen by their brightness and their bluish spectral slope [5]. We found that the surface material of Ceres is, among the suite of CCs, most similar to Ivuna samples artificially heated to 200 and 300°C [6] and unusual CCs, which naturally experienced heating. The latter ones comprise Dhofar 225, Y-86789 and Y-82162, which have been determined to have undergone aqueous alteration and subsequent thermal metamorphism (e.g. [7,8]).Our comparison with VIR data shows, that the spectra of Ivuna heated to 200°C and 300°C match well the OH-absorption at 2.7 μm but do not show the smaller 3.05-3.1 μm absorption observed on Ceres [9,10,11]. Nevertheless, the remarkably flat UV drop-off detected on the cerean surface may, at least spectrally, correspond to highly aqueously altered and subsequently thermally metamorphosed CC material. Further alteration of

  1. A New Modal Analysis Method to put Constraints on the Aqueous Alteration of CR Chondrites and Estimate the Unaltered CR Composition

    Science.gov (United States)

    Perronnet, M.; Zolensky, M. E.; Gounelle, M.; Schwandt, C. S.

    2007-01-01

    carbonaceous chondrites are of the major interest since they contain one of the most primitive organic matters. However, aqueous alteration has more or less overprinted their original features in a way that needed to be assessed. That was done in the present study by comparing the mineralogy of the most altered CR1 chondrite, GRO 95577, to a less altered CR2, Renazzo. Their modal analyses were achieved thanks to a new method, based on X-ray elemental maps acquired on electron microprobe, and on IDL image treatment. It allowed the collection of new data on the composition of Renazzo and confirmed the classification of GRO 95577 as a CR1. New alteration products for CRs, vermiculite and clinochlore, were observed. The homogeneity of the Fe-poor clays in the CR1 and the distinctive matrix composition in the two chondrites suggest a wide-range of aqueous alteration on CRs. The preservation of the outlines of the chondrules in GRO 95577 and the elemental transfers of Al, Fe and Ca throughout the chondrule and of Fe and S from the matrix to the chondrule favor the idea of an asteroidal location of the aqueous alteration. From their mineralogical descriptions and modal abundances, the element repartitions in Renazzo and GRO 95577 were computed. It indicates a possible relationship between these two chondrites via an isochemical alteration process. Knowing the chemical reactions that occurred during the alteration, it was thus possible to decipher the mineralogical modal abundances in the unaltered CR body.

  2. Evidence for Oxygen-Isotope Exchange in Chondrules and Refractory Inclusions During Fluid-Rock Interaction on the CV Chondrite Parent Body

    Science.gov (United States)

    Krot, A. N.; Nagashima, K.

    2016-08-01

    Plagioclase in chondrules, CAIs and AOAs from the carbonaceous chondrite Kaba (CV3.1) experienced oxygen-isotope exchange with a metasomatic fluid responsible for the formation of magnetite, fayalite and Ca,Fe-rich silicates on the CV parent body.

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

    Science.gov (United States)

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

    2001-01-01

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

  4. Noble Gases in the Monahans Chondrite and Halite: Ar-39 - Ar-40 Age, Space Exposure Age, Trapped Solar Gases, and Neutron Fluence

    Science.gov (United States)

    Garrison, Daniel H.; Bogard, Donald D.

    2000-01-01

    For the Monahans chondrite and halite, we determined Ar-39 - Ar-40 ages of silicate = 4.53 Ga, halite > 4.3 Ga; a space exposure age of approx. 5 Ma; a regolith pre-irradiation; solar gas concentrations in the dark phase; and a regolith thermal neutron fluence.

  5. The L3-6 chondritic regolith breccia Northwest Africa (NWA) 869: (I) Petrology, chemistry, oxygen isotopes, and Ar-Ar age determinations

    Science.gov (United States)

    Metzler, Knut; Bischoff, Addi; Greenwood, Richard C.; Palme, Herbert; Gellissen, Marko; Hopp, Jens; Franchi, Ian A.; Trieloff, Mario

    2011-05-01

    Northwest Africa (NWA) 869 consists of thousands of individual stones with an estimated total weight of about 7 metric tons. It is an L3-6 chondrite and probably represents the largest sample of the rare regolith breccias from the L-chondrite asteroid. It contains unequilibrated and equilibrated chondrite clasts, some of which display shock-darkening. Impact melt rocks (IMRs), both clast-free and clast-poor, are strongly depleted in Fe,Ni metal, and sulfides. An unequilibrated microbreccia, two different light inclusions and two different SiO2-bearing objects were found. Although the matrix of this breccia appears partly clastic, it is not a simple mixture of fine-grained debris formed from the above lithologies, but mainly represents an additional specific lithology of low petrologic type. We speculate that this material stems from a region of the parent body that was only weakly consolidated. One IMR clast and one SiO2-bearing object show Δ17O values similar to bulk NWA 869, suggesting that both are related to the host rock. In contrast, one light inclusion and one IMR clast appear to be unrelated to NWA 869, suggesting that the IMR clast is contaminated with impactor material. 40Ar-39Ar analyses of a type 4 chondrite clast yield a plateau age of 4402 ± 7 Ma, which is interpreted to be the result of impact heating. Other impact events are recorded by an IMR clast at 1790 ± 36 Ma and a shock-darkened clast at 2216 ± 40 Ma, demonstrating that NWA 869 escaped major reset in the course of the event at approximately 470 Ma that affected many L-chondrites.

  6. Chondritic Xenon in the Earth's mantle: new constrains on a mantle plume below central Europe

    Science.gov (United States)

    Caracausi, Antonio; Avice, Guillaume; Bernard, Peter; Furi, Evelin; Marty, Bernard

    2016-04-01

    Due to their inertness, their low abundances, and the presence of several different radiochronometers in their isotope systematics, the noble gases are excellent tracers of mantle dynamics, heterogeneity and differentiation with respect to the atmosphere. Xenon deserves particular attention because its isotope systematic can be related to specific processes during terrestrial accretion (e.g., Marty, 1989; Mukhopadhyay, 2012). The origin of heavy noble gases in the Earth's mantle is still debated, and might not be solar (Holland et al., 2009). Mantle-derived CO2-rich gases are particularly powerful resources for investigating mantle-derived noble gases as large quantities of these elements are available and permit high precision isotope analysis. Here, we report high precision xenon isotopic measurements in gases from a CO2 well in the Eifel volcanic region (Germany), where volcanic activity occurred between 700 ka and 11 ka years ago. Our Xe isotope data (normalized to 130Xe) show deviations at all masses compared to the Xe isotope composition of the modern atmosphere. The improved analytical precision of the present study, and the nature of the sample, constrains the primordial Xe end-member as being "chondritic", and not solar, in the Eifel mantle source. This is consistent with an asteroidal origin for the volatile elements in Earth's mantle and it implies that volatiles in the atmosphere and in the mantle originated from distinct cosmochemical sources. Despite a significant fraction of recycled atmospheric xenon in the mantle, primordial Xe signatures still survive in the mantle. This is also a demonstration of a primordial component in a plume reservoir. Our data also show that the reservoir below the Eifel region contains heavy-radiogenic/fissiogenic xenon isotopes, whose ratios are typical of plume-derived reservoirs. The fissiogenic Pu-Xe contribution is 2.26±0.28 %, the UXe contribution is negligible, the remainder being atmospheric plus primordial. Our

  7. Early solar system. Early accretion of water in the inner solar system from a carbonaceous chondrite-like source.

    Science.gov (United States)

    Sarafian, Adam R; Nielsen, Sune G; Marschall, Horst R; McCubbin, Francis M; Monteleone, Brian D

    2014-10-31

    Determining the origin of water and the timing of its accretion within the inner solar system is important for understanding the dynamics of planet formation. The timing of water accretion to the inner solar system also has implications for how and when life emerged on Earth. We report in situ measurements of the hydrogen isotopic composition of the mineral apatite in eucrite meteorites, whose parent body is the main-belt asteroid 4 Vesta. These measurements sample one of the oldest hydrogen reservoirs in the solar system and show that Vesta contains the same hydrogen isotopic composition as that of carbonaceous chondrites. Taking into account the old ages of eucrite meteorites and their similarity to Earth's isotopic ratios of hydrogen, carbon, and nitrogen, we demonstrate that these volatiles could have been added early to Earth, rather than gained during a late accretion event.

  8. Isotopic composition of carbonaceous-chondrite kerogen Evidence for an interstellar origin of organic matter in meteorites

    Science.gov (United States)

    Kerridge, J. F.

    1983-01-01

    Stepwise combustion has revealed systematic patterns of isotopic heterogeneity for C, H and N in the insoluble organic fraction (m-kerogen) from the Orgueil and Murray carbonaceous chondrites. Those patterns are essentially identical for both meteorites, indicating a common source of m-kerogen. The data cannot be reconciled with a single mass-fractionation process acting upon a single precursor composition. This indicates either a multi-path history of mass-dependent processing or a significant nucleogenetic contribution, or both. If mass-fractionation were the dominant process, the magnitude of the observed isotopic variability strongly suggests that ion-molecule reactions at very low temperatures, probably in interstellar clouds, were responsible. In any case, an interstellar, rather than solar nebular, origin for at least some of the meteoritic organic matter is indicated. This has interesting implications for the origin of prebiotic molecules, temperatures in the early solar system, and the isotopic compositions of volatiles accreted by the terrestrial planets.

  9. High-temperature water-rock interactions and hydrothermal environments in the chondrite-like core of Enceladus.

    Science.gov (United States)

    Sekine, Yasuhito; Shibuya, Takazo; Postberg, Frank; Hsu, Hsiang-Wen; Suzuki, Katsuhiko; Masaki, Yuka; Kuwatani, Tatsu; Mori, Megumi; Hong, Peng K; Yoshizaki, Motoko; Tachibana, Shogo; Sirono, Sin-iti

    2015-10-27

    It has been suggested that Saturn's moon Enceladus possesses a subsurface ocean. The recent discovery of silica nanoparticles derived from Enceladus shows the presence of ongoing hydrothermal reactions in the interior. Here, we report results from detailed laboratory experiments to constrain the reaction conditions. To sustain the formation of silica nanoparticles, the composition of Enceladus' core needs to be similar to that of carbonaceous chondrites. We show that the presence of hydrothermal reactions would be consistent with NH3- and CO2-rich plume compositions. We suggest that high reaction temperatures (>50 °C) are required to form silica nanoparticles whether Enceladus' ocean is chemically open or closed to the icy crust. Such high temperatures imply either that Enceladus formed shortly after the formation of the solar system or that the current activity was triggered by a recent heating event. Under the required conditions, hydrogen production would proceed efficiently, which could provide chemical energy for chemoautotrophic life.

  10. Identification of silicate and carbonaceous presolar grains by SIMS in the type-3 enstatite chondrite ALHA81189

    International Nuclear Information System (INIS)

    An isotope ratio imaging technique using the HokuDai isotope microscope system has been applied to in situ survey for presolar grains in the type-3 enstatite chondrite ALHA81189. Rastered and static ion beam were used for primary beam. Lateral resolution of the isotope image was achieved to be 0.4 μm for static ion beam mode and to be 0.6 μm for rastered ion beam mode. As a result, the abundances of presolar grains are 150-200% larger under the static ion beam mode than under the rastered ion beam mode. Development of image processing introducing isotopography of 32S-, 24Mg16O- and 56Fe- succeeded to increase efficiency of presolar grain characterization. Using the static ion beam and introducing appropriate isotopography were very useful methods of in situ characterization of presolar grains in meteorites

  11. PHOTOPHORETIC SEPARATION OF METALS AND SILICATES: THE FORMATION OF MERCURY-LIKE PLANETS AND METAL DEPLETION IN CHONDRITES

    International Nuclear Information System (INIS)

    Mercury's high uncompressed mass density suggests that the planet is largely composed of iron, either bound within metal (mainly Fe-Ni) or iron sulfide. Recent results from the MESSENGER mission to Mercury imply a low temperature history of the planet which questions the standard formation models of impact mantle stripping or evaporation to explain the high metal content. Like Mercury, the two smallest extrasolar rocky planets with mass and size determination, CoRoT-7b and Kepler-10b, were found to be of high density. As they orbit close to their host stars, this indicates that iron-rich inner planets might not be a nuisance of the solar system but be part of a general scheme of planet formation. From undifferentiated chondrites, it is also known that the metal to silicate ratio is highly variable, which must be ascribed to preplanetary fractionation processes. Due to this fractionation, most chondritic parent bodies—most of them originated in the asteroid belt—are depleted in iron relative to average solar system abundances. The astrophysical processes leading to metal silicate fractionation in the solar nebula are essentially unknown. Here, we consider photophoretic forces. As these forces particularly act on irradiated solids, they might play a significant role in the composition of planetesimals forming at the inner edge of protoplanetary disks. Photophoresis can separate high thermal conductivity materials (iron) from lower thermal conductivity solids (silicate). We suggest that the silicates are preferentially pushed into the optically thick disk. Subsequent planetesimal formation at the edge moving outward leads to metal-rich planetesimals close to the star and metal depleted planetesimals farther out in the nebula.

  12. PHOTOPHORETIC SEPARATION OF METALS AND SILICATES: THE FORMATION OF MERCURY-LIKE PLANETS AND METAL DEPLETION IN CHONDRITES

    Energy Technology Data Exchange (ETDEWEB)

    Wurm, Gerhard [Fakultaet fuer Physik, Universitaet Duisburg-Essen, Lotharstr. 1, D-47057 Duisburg (Germany); Trieloff, Mario [Institut fuer Geowissenschaften, Universitaet Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg (Germany); Rauer, Heike, E-mail: gerhard.wurm@uni-due.de [Institut fuer Planetenforschung, Extrasolare Planeten und Atmosphaeren, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), Rutherfordstrasse 2, D-12489 Berlin (Germany)

    2013-05-20

    Mercury's high uncompressed mass density suggests that the planet is largely composed of iron, either bound within metal (mainly Fe-Ni) or iron sulfide. Recent results from the MESSENGER mission to Mercury imply a low temperature history of the planet which questions the standard formation models of impact mantle stripping or evaporation to explain the high metal content. Like Mercury, the two smallest extrasolar rocky planets with mass and size determination, CoRoT-7b and Kepler-10b, were found to be of high density. As they orbit close to their host stars, this indicates that iron-rich inner planets might not be a nuisance of the solar system but be part of a general scheme of planet formation. From undifferentiated chondrites, it is also known that the metal to silicate ratio is highly variable, which must be ascribed to preplanetary fractionation processes. Due to this fractionation, most chondritic parent bodies-most of them originated in the asteroid belt-are depleted in iron relative to average solar system abundances. The astrophysical processes leading to metal silicate fractionation in the solar nebula are essentially unknown. Here, we consider photophoretic forces. As these forces particularly act on irradiated solids, they might play a significant role in the composition of planetesimals forming at the inner edge of protoplanetary disks. Photophoresis can separate high thermal conductivity materials (iron) from lower thermal conductivity solids (silicate). We suggest that the silicates are preferentially pushed into the optically thick disk. Subsequent planetesimal formation at the edge moving outward leads to metal-rich planetesimals close to the star and metal depleted planetesimals farther out in the nebula.

  13. 87Rb-87Sr chronology of H chondrites: constraint and speculations on the early evolution of their parent body

    International Nuclear Information System (INIS)

    A precise 87Rb-87Sr whole-rock isochron for H chrondrites and an internal isochron for Tieschitz (H3) have been determined. The age and 87Sr/86Sr initial ratio of the whole rocks are 4.25 +- 0.05 b.y. and 0.69876 +- 0.00040 (lambda(87Rb) = 1.42 X 10-11 yr-1). For Tieschitz, whereas handipicked separates plot on a well-defined line, heavy liquid separates scatter in the 87Rb/86Sr vs. 87Sr/86Sr diagram. Leaching experiments by heavy liquids indicate that they might have a sizeable effect on Tieschitz minerals. The age and 87Sr/86Sr initial ratio as determined by handpicked separates are 4.53 +- 0.06 b.y. and 0.69880 +- 0.00020, indistinguishable from the whole-rock isochron. These results are interpreted as 'primitive isochrons' dating the condensation of chondrites from the solar nebula. The best value of this event is given by joining both isochrons together at 4.518 +- 0.026 b.y. and 87Sr/86Sr = 0.69881 +- 0.00016. The near identity of this initial ratio with the one of Allende white inclusions argues in favor of a sharp isochronism of condensation from a 87Sr/86Sr homogeneous nebula. Data from Guarena and Richardton are interpreted as secondary internal isochrons, 100 m.y. after the condensation of the whole rocks. The data are then used to constrain a thermal evolution model of the H chondrite parent body. This body might have a 150-175 km radius, and might have been heated by 26Al. An 26Al/27Al ratio of 4-6 X 10-6 is enough for heating such a body. Further tests for this model are proposed. (Auth.)

  14. The CO chondrites: Major recent Antarctic finds, their thermal and radiation history, and describing the metamorphic history of members of the class

    Science.gov (United States)

    Sears, Derek W. G.

    2016-09-01

    Thermoluminescence (TL) properties of 29 CO chondrites from the Miller Range (MIL) and five chondrites from the Dominion Range (DOM) have been measured. MIL has a relatively strong natural TL signal (19.6 ± 14.7 krad), while some of the DOM samples have a very weak natural TL signal (age of ∼450-700 ka, while some of the DOM samples have a terrestrial age of ∼100 ka but a perihelion of ∼0.8 AU. The DOM meteorites also show considerable heterogeneity in their induced TL properties, also suggesting that the DOM fragments represent more than one fall. The induced TL data for the MIL samples studied here are consistent with them all being from a single fragmented meteorite. Small (50 mg) chips have TL properties similar to 500 mg chips, so that the smaller chips are representative, although samples taken from original masses less than ∼2 g have low natural TL suggesting that they were heated during atmospheric fall. The properties of CO chondrites are reviewed in terms of their petrologic types. Correlations between TL sensitivity, the most quantitative technique for evaluating metamorphic alteration in CO chondrites, and data for olivine composition and heterogeneity, matrix composition, inert gas content, metal composition (Ni, Co, and Cr in the kamacite), bulk carbon, C and O isotopes, graphite ordering, spectral reflectance at 0.8 μm, and textural characteristics of the ameboid olivine and Ca-rich inclusions are examined. The petrographic types appear to be largely metamorphic in origin with perhaps a minor role for metasomatism. Contrary to recent proposals it is here argued that petrologic type definitions should (1) be specific enough to be meaningful, but broad enough to be simple in application and robust to new developments, (2) be descriptive and not interpretative, (3) should not oversimplify and obscure important class-to-class differences, and (4) take account of all the available information, while avoiding reliance on any one technique or

  15. Identification and Characterization of Early Solar system Organic Matter Preserved in Chondritic Porous Interplanetary Dust Particles

    Science.gov (United States)

    Flynn, George; Wirick, Sue; Keller, Lindsay

    2015-04-01

    The chondritic porous interplanetary dust particles (CP IDPs), collected by NASA from the Earth's stratosphere, have experienced minimal aqueous or thermal alteration since their formation. These CP IDPs are the best preserved samples of the minerals and organic matter that was present in the primitive Solar Nebula that are currently available for laboratory analysis [1]. The ~10 μm CP IDPs are aggregates of tens-of-thousands of mostly sub-micron grains of diverse compositions and mineralogies. Many of the individual mineral grains are coated by a 50 to 200 nm thick rims of carbonaceous material, and other carbonaceous material occurs as larger, discrete subunits within the particles [2]. We characterize this carbonaceous material using two high-resolution, synchrotron-based instruments: a Scanning Transmission X-ray Microscope (STXM) to locate and map the carbon and to identify its major functional groups by X-ray Absorption Near-Edge Structure (XANES) spectroscopy, and a micro-Fourier Transform Infrared (μ-FTIR) spectrometer to further characterize the functional groups by mid-infrared spectroscopy. Carbon-XANES spectroscopy identifies the rims coating the individual grains in CP IDPs as organic matter, dominated by the C=C, likely C-rings, and the C=O functional groups [3]. This structure, with the organic rims being the contact surfaces between the grains, implies a 3-step formation sequence: grain condensation, organic rim emplacement, and, finally, aggregation of the grains to form the dust particles. This suggests these organic rims formed very early in the evolution of the Solar Nebula, after grain condensation but before grain aggregation [3]. These organic rims coat grains of diverse compositions, including silicates, sulfides, and carbonates, which is inconsistent with formation by Fischer-Tropsch-like, mineral-specific catalysis, one of the mechanisms suggested for the formation of primitive organic matter. Our observations are consistent with an

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

    CERN Document Server

    Jacquet, Emmanuel; Gounelle, Matthieu

    2016-01-01

    We report in situ LA-ICP-MS trace element analyses of silicate phases in olivine-bearing chondrules in the Sahara 97096 (EH3) enstatite chondrite. Most olivine and enstatite present rare earth element (REE) patterns comparable to their counterparts in type I chondrules in ordinary chondrites. They thus likely share a similar igneous origin, likely under similar redox conditions. The mesostasis however frequently shows negative Eu and/or Yb (and more rarely Sm) anomalies, evidently out of equilibrium with olivine and enstatite. We suggest that this reflects crystallization of oldhamite during a sulfidation event, already inferred by others, during which the mesostasis was molten, where the complementary positive Eu and Yb anomalies exhibited by oldhamite would have possibly arisen due to a divalent state of these elements. Much of this igneous oldhamite would have been expelled from the chondrules, presumably by inertial acceleration or surface tension effects, and would have contributed to the high abundance ...

  17. Structure of high-molecular carbonaceous compound in carbonaceous chondrites and formation of IR-spectroscopically similar compounds in the laboratory

    Science.gov (United States)

    Murae, T.

    1997-05-01

    Main components of carbonaceous matter in carbonaceous chondrites are high molecular organic matter. Examinations of the compounds using pyrolysis GC/MS and FT-IR indicated the structural resemblance of major part of the molecule for all of the compounds from different types of carbonaceous chondrites (8 Antarctic and 2 none-Antarctic meteorites). A carbonaceous matter derived from graphite on a shock experiment using a rail gun (1g projectile at 7 km/s) showed similar IR spectrum to those of the meteoritic high-molecular organic matter. C-60 fulleren also gave a similar compound (with minor differences in IR spectra) on a shock experiment under the same conditions. A shock experiment using coronene also examined.

  18. Extremely rapid cooling of a carbonaceous-chondrite chondrule containing very 16O-rich olivine and a 26Mg-excess

    Science.gov (United States)

    Yurimoto, Hisayoshi; Wasson, John T.

    2002-12-01

    We describe a phenocryst in a CO-chondrite type-II chondrule that we infer to have formed by melting an amoeboid olivine aggregate (AOA). This magnesian olivine phenocryst has an extremely 16O-rich composition Δ 17O (=δ 17O - 0.52 · δ 18O) = -23‰. It is present in one of the most pristine carbonaceous chondrites, the CO3.0 chondrite Yamato 81020. The bulk of the chondrule has a very different Δ 17O of -1‰, thus the Δ 17O range within this single chondrule is 22‰, the largest range encountered in a chondrule. We interpret the O isotopic and Fe-Mg distributions to indicate that a fine-grained AOA assemblage was incompletely melted during the flash melting that formed the chondrule. Some Fe-Mg exchange but negligible O-isotopic exchange occurred between its core and the remainder of the chondrule. A diffusional model to account for the observed Fe-Mg and O-isotopic exchange yields a cooling rate of 10 5 to 10 6 K hr -1. This estimate is much higher than the cooling rates of 10 1 to 10 3 K hr -1 inferred from furnace simulations of type-II chondrule textures (e.g. Lofgren, 1996); however, our cooling-rate applies to higher temperatures (near 1900 K) than are modeled by the crystal-growth based cooling rates. We observed a low 26Al/ 27Al initial ratio ((4.6 ± 3.0) · 10 -6) in the chondrule mesostasis, a value similar to those in ordinary chondrites (Kita et al., 2000). If the 26Al/ 27Al system is a good chronometer, then chondrule I formed about 2 Ma after the formation of refractory inclusions.

  19. Opaque Minerals in LL3.0-6 Chondrites I:Mineralogy of Ti-oxides and 53Mn-53Cr Systematics of Ilmenite

    Institute of Scientific and Technical Information of China (English)

    KIMURA Makoto; SUGIURA Naoji; NAKAJIMA Haruna; Michael K. WEISBERG

    2004-01-01

    We conducted a systematic study of oxide minerals in LL3.0-6 chondrites, and found ilmenite, rutile,perovskite and an unknown A1-Ti-Zr-oxide. Ilmenite is low in abundance, but is present in the chondrules and matrix of all the samples that we studied. The MnO content of ilmenite in LL3.0-3.3 is lower than that in LL3.5-6. The low concentration of MnO in the former is due to crystallization from chondrules melts at high temperatures. On the other hand, ilmenite composition in LL3.5-6 reflects thermal metamorphism. Therefore, ilmenite is indicative of petrologic type.We also made the first measurements of the 53Mn-53Cr systematics of ilmenite in ordinary chondrites. The age for ilmenite in Y790256 (LL6) is determined to be about 2 Ma older than angrites. This may represent the metamorphic age of the LL chondrites.

  20. On the Chemical Evolution of Upper Mantle of the Early Earth—An Experimental Study on Melting of the Silicate Phase in Jilin Chondrite at High Pressures

    Institute of Scientific and Technical Information of China (English)

    谢鸿森; 方虹; 等

    1989-01-01

    Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terrestrial plaets.Therefore,it is reasonable to take chondrites as starting materials in the study of the chemical evolution of the early earth.The sillicate phase in the Jilin chondrite (H5)was chosen for this purpose because it possesses a chemical composition similar to that of the primitive mantle.The melting experiment was carried out at 20-30 k bar and has rsulted in a product which contains1-5% melts in addition to solid cryustal phase.The chemical composition of the melt phases and the partitioning of various elements between the coexisting silicate melts are geochemically similar to those of anatectic rocks on the earth.This can thus serve as the basis for discussing the chemical evolution of the early upper mantle.

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

    Science.gov (United States)

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

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

  2. Weathering of ordinary chondrites from Oman: Correlation of weathering parameters with 14C terrestrial ages and a refined weathering scale

    Science.gov (United States)

    Zurfluh, Florian J.; Hofmann, Beda A.; Gnos, Edwin; Eggenberger, Urs; Jull, A. J. Timothy

    2016-09-01

    We have investigated 128 14C-dated ordinary chondrites from Oman for macroscopically visible weathering parameters, for thin section-based weathering degrees, and for chemical weathering parameters as analyzed with handheld X-ray fluorescence. These 128 14C-dated meteorites show an abundance maximum of terrestrial age at 19.9 ka, with a mean of 21.0 ka and a pronounced lack of samples between 0 and 10 ka. The weathering degree is evaluated in thin section using a refined weathering scale based on the current W0 to W6 classification of Wlotzka (1993), with five newly included intermediate steps resulting in a total of nine (formerly six) steps. We find significant correlations between terrestrial ages and several macroscopic weathering parameters. The correlation of various chemical parameters including Sr and Ba with terrestrial age is not very pronounced. The microscopic weathering degree of metal and sulfides with newly added intermediate steps shows the best correlation with 14C terrestrial ages, demonstrating the significance of the newly defined weathering steps. We demonstrate that the observed 14C terrestrial age distribution can be modeled from the abundance of meteorites with different weathering degrees, allowing the evaluation of an age-frequency distribution for the whole meteorite population.

  3. Origin of magnetite in oxidized CV chondrites: in situ measurement of oxygen isotope compositions of Allende magnetite and olivine

    Science.gov (United States)

    Choi, B. G.; McKeegan, K. D.; Leshin, L. A.; Wasson, J. T.

    1997-01-01

    Magnetite in the oxidized CV chondrite Allende mainly occurs as spherical nodules in porphyritic-olivine (PO) chondrules, where it is associated with Ni-rich metal and/or sulfides. To help constrain the origin of the magnetite, we measured oxygen isotopic compositions of magnetite and coexisting olivine grains in PO chondrules of Allende by an in situ ion microprobe technique. Five magnetite nodules form a relatively tight cluster in oxygen isotopic composition with delta 18O values from -4.8 to -7.1% and delta 17O values from -2.9 to -6.3%. Seven coexisting olivine grains have oxygen isotopic compositions from -0.9 to -6.3% in delta 18O and from -4.6 to -7.9% in delta 17O. The delta 17O values of the magnetite and coexisting olivine do not overlap; they range from -0.4 to -2.6%, and from -4.0 to -5.7%, respectively. Thus, the magnetite is not in isotopic equilibrium with the olivine in PO chondrules, implying that it formed after the chondrule formation. The delta 17O of the magnetite is somewhat more negative than estimates for the ambient solar nebula gas. We infer that the magnetite formed on the parent asteroid by oxidation of metal by H2O which had previously experienced minor O isotope exchange with fine-grained silicates.

  4. In-situ X-ray CT results of damage evolution in L6 ordinary chondrite meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Cuadra, Jefferson A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hazeli, Kavan [Univ. of Alabama, Huntsville, AL (United States); Ramesh, K. T. [Johns Hopkins Univ., Baltimore, MD (United States). Hopkins Extreme Materials Inst.; Martz, Harry [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nondestructive Characterization Inst.

    2016-06-17

    These are slides about in-situ X-ray CT results of damage evolution in L6 ordinary chondrite meteorites. The following topics are covered: mechanical and thermal damage characterization, list of Grosvenor Mountain (GRO) meteorite samples, in-situ x-ray compression test setup, GRO-chipped reference at 0 N - existing cracks, GRO-chipped loaded at 1580 N, in-situ x-ray thermal fatigue test setup, GRO-B14 room temperature reference, GRO-B14 Cycle 47 at 200°C, GRO-B14 Cycle 47 at room temperature, conclusions from qualitative analysis, future work and next steps. Conclusions are the following: Both GRO-Chipped and GRO-B14 had existing voids and cracks within the volume. These sites with existing damage were selected for CT images from mechanically and thermally loaded scans since they are prone to damage initiation. The GRO-Chipped sample was loaded to 1580 N which resulted in a 14% compressive engineering strain, calculated using LVDT. Based on the CT cross sectional images, the GRO-B14 sample at 200°C has a thermal expansion of approximately 96 μm in height (i.e. ~1.6% engineering strain).

  5. Composition of Potentially Hazardous Asteroid (214869) 2007 PA8: An H Chondrite from the Outer Asteroid Belt

    CERN Document Server

    Sanchez, Juan A; Dykhuis, Melissa; Lindsay, Sean; Corre, Lucille Le

    2015-01-01

    Potentially hazardous asteroids (PHAs) represent a unique opportunity for physical characterization during their close approaches to Earth. The proximity of these asteroids makes them accessible for sample-return and manned missions, but could also represent a risk for life on Earth in the event of collision. Therefore, a detailed mineralogical analysis is a key component in planning future exploration missions and developing appropriate mitigation strategies. In this study we present near-infrared spectra (0.7-2.55 microns) of PHA (214869) 2007 PA8 obtained with the NASA Infrared Telescope Facility during its close approach to Earth on November 2012. The mineralogical analysis of this asteroid revealed a surface composition consistent with H ordinary chondrites. In particular, we found that the olivine and pyroxene chemistries of 2007 PA8 are Fa18(Fo82) and Fs16, respectively. The olivine-pyroxene abundance ratio was estimated to be 47%. This low olivine abundance and the measured band parameters, close to t...

  6. An experimental study of pyroxene crystallization during rapid cooling in a thermal gradient; applications to komatiites and chondrites

    Directory of Open Access Journals (Sweden)

    S. Bouquain

    2013-03-01

    Full Text Available To investigate the crystallization of pyroxene in spinifex-textured komatiites and in chondrites we undertook a series of experiments in which compositions in the CMAS system were cooling rapidly in a thermal gradient. Cooling rates were generally between 5 to 10 °C h−1 but some runs were made at 100–200 °C h−1; thermal gradients were between 10 and 20 °C cm−1. These conditions reproduced those at various levels in the crust of komatiitic lava flow. The starting composition was chosen to have pigeonite on the liquidus and a majority of the experiments crystallized zoned pigeonite-diopside crystals like those in komatiite lavas. A~conspicuous aspect of the experimental results was their lack of reproduceability. Some experiments crystallized forsterite whereas others that were run under similar conditions crystallized two pyroxenes and no forsterite; some experiments were totally glassy but others totally crystallized to pyroxene. The degree of supercooling at the onset of pyroxene crystallization was variable, from less than 25 °C to more than 110 °C. We attribute these results to the difficulty of nucleation of pyroxene. In some cases forsterite crystallized metastably and modified the liquid composition to inhibit pyroxene crystallization; in others no nucleation took place until a large degree of supercooling was achieved, then pyroxene crystallized rapidly. Pigeonite crystallized under a wide range of conditions, at cooling rates from 3 to 100 °C h−1. The notion that this mineral only forms at low cooling rates is not correct.

  7. Coordinated Isotopic and Mineral Characterization of Highly Fractionated 18O-Rich Silicates in the Queen Alexandra Range 99177 CR3 Chondrite

    Science.gov (United States)

    Nguyen, A. N.; Keller, L. P.; Messenger, S.; Rahman, Z.

    2016-01-01

    Carbonaceous chondrites contain a mixture of solar system condensates, pre-solar grains, and primitive organic matter. Each of these materials record conditions and processes in different regions of the solar nebula, on the meteorite parent body, and beyond the solar system. Oxygen isotopic studies of meteorite components can trace interactions of distinct oxygen isotopic reservoirs in the early solar system and secondary alteration processes. The O isotopic compositions of the earliest solar system condensates fall along a carbonaceous chondrite anhydrous mineral (CCAM) line of slope approximately 1 in a plot of delta 17O against delta 18O. This trend is attributed to mixing of material from 16O-poor and 16O-rich reservoirs. Secondary processing can induce mass-dependent fractionation of the O isotopes, shifting these compositions along a line of slope approximately 0.52. Substantial mass-dependent fractionation of O isotopes has been observed in secondary minerals in CAIs, calcite, and FUN inclusions. These fractionations were caused by significant thermal or aqueous alteration. We recently reported the identification of four silicate grains with extremely fractionated O isotopic ratios (delta 18O equals 37 - 55 per mille) in the minimally altered CR3 chondrite QUE 99177. TEM analysis of one grain indicates it is a nebular condensate that did not experience substantial alteration. The history of these grains is thus distinct from those of the aforementioned fractionated materials. To constrain the origin of the silicate grains, we conducted further Mg and Fe isotopic studies and TEM analyses of two grains.

  8. Planetary Bioresources and Astroecology. 1. Planetary Microcosm Bioassays of Martian and Carbonaceous Chondrite Materials: Nutrients, Electrolyte Solutions, and Algal and Plant Responses

    Science.gov (United States)

    Mautner, Michael N.

    2002-07-01

    The biological fertilities of planetary materials can be assessed using microcosms based on meteorites. This study applies microcosm tests to martian meteorites and analogues and to carbonaceous chondrites. The biological fertilities of these materials are rated based on the soluble electrolyte nutrients, the growth of mesophile and cold-tolerant algae, and plant tissue cultures. The results show that the meteorites, in particular the Murchison CM2 carbonaceous chondrite and DaG 476 martian shergottite, contain high levels of water-extractable Ca, Mg, and SO 4-S. The martian meteorites DaG 476 and EETA 79001 also contain higher levels of extractable essential nutrients NO 3-N (0.013-0.017 g kg -1) and PO 4-P (0.019-0.046 g kg -1) than the terrestrial analogues. The yields of most of the water-extractable electrolytes vary only by factors of 2-3 under a wide range of planetary conditions. However, the long-term extractable phosphate increases significantly under a CO 2 atmosphere. The biological yields of algae and plant tissue cultures correlate with extractable NO 3-N and PO 4-P, identifying these as the limiting nutrients. Mesophilic algae and Asparagus officinalis cultures are identified as useful bioassay agents. A fertility rating system based on microcosm tests is proposed. The results rate the fertilities in the order martian basalts > terrestrial basalt, agricultural soil > carbonaceous chondrites, lava ash > cumulate igneous rock. The results demonstrate the application of planetary microcosms in experimental astroecology to rate planetary materials as targets for astrobiology exploration and as potential space bioresources. For example, the extractable materials in Murchison suggest that concentrated internal solutions in carbonaceous asteroids (3.8 mol L -1 electrolytes and 10 g L -1 organics) can support and disperse microorganisms introduced by natural or directed panspermia in early solar systems. The results also suggest that carbonaceous asteroids

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

    Science.gov (United States)

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

    2015-04-01

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

  10. The Halite-Bearing Zag and Monahans (1998) Meteorite Breccias: Shock Metamorphism, Thermal Metamorphism and Aqueous Alteration on the H-Chondrite Parent Body

    Science.gov (United States)

    Rubin, Alan E.; Zolensky, Michael E.; Bodnar, Robert J.

    2002-01-01

    Zag and Monahans (1998) are H-chondrite regolith breccias comprised mainly of lightcolored metamorphosed clasts, dark clasts that exhibit extensive silicate darkening, and a halite-bearing clastic matrix. These meteorites reflect a complex set of modification processes that occurred on the H-chondrite parent body. The light-colored clasts are thermally metamorphosed H5 and H6 rocks that were fragmented and deposited in the regolith. The dark clasts formed from light-colored clasts during shock events that melted and mobilized a significant fraction of their metallic Fe-Ni and troilite grains. The clastic matrices of these meteorites are rich in solar-wind gases. Parent-body water was required to cause leaching of chondri tic minerals and chondrule glass; the fluids became enriched in Na, K, CI, Br, AI, Ca, Mg and Fe. Evaporation of the fluids caused them to become brines as halides and alkalies became supersaturated; grains of halite (and, in the case of Monahans (1998), halite with sylvite inclusions) precipitated at low temperatures (less than or equal to 100 C) in the porous regolith. In both meteorites fluid inclusions were trapped inside the halite crystals. Primary fluid inclusions were trapped in the growing crystals; secondary inclusions formed subsequently from fluid trapped within healed fractures.

  11. SNOW COVER OF THE CENTRAL ANTARCTICA (VOSTOK STATION AS AN IDEAL NATURAL TABLET FOR COSMIC DUST COLLECTION: PRELIMINARY RESULTS ON THE IDENTIFICATION OF MICROMETEORITES OF CARBONACEOUS CHONDRITE TYPE

    Directory of Open Access Journals (Sweden)

    E. S. Bulat

    2012-01-01

    Full Text Available During the 2010/11 season nearby the Vostok station the 56th Russian Antarctic Expedition has collected surface snow in a big amount from a 3 m deep pit using 15 220 L vol. containers (about 70 kg snow each. Snow melting and processing by ultra-centrifugation was performed in a clean (class 10 000 and 100 laboratory. Total dust concentrations were not exceeded 37.4 mkg per liter with particle dispersal mode around 2.5 mkm. To analyze the elemental composition of fine dust particles aimed to reveal Antarctic micrometeorites (AMM two electron microscopy devices equipped with different micro-beams were implemented. As a preliminary result, three particles (of 107 analyzed featured by Mg content clearly dominated over Al along with Si and Fe as major elements (a feature of carbonaceous chondrites were observed. By this the Vostok AMM CS11 collection was established. The occurrence of given particles was averaged 2.8% – the factual value obtained for the first time for chondritic type AMM at Vostok which should be considered as the lowest estimate for all other families of AMM. Given the reference profile of total dust content in East Antarctic snow during Holocene (18 mkg/kg the MM deposition in Antarctica was quantified for the first time – 14 tons per day for carbonaceous chondrites for the Vostok AMM CS11 collection and up to 245 tons per day for all MM types for the Concordia AMM DC02 collection. The results obtained allowed to prove that snow cover (ice sheet in total of Central East Antarctica is the best spot (most clean of other natural locations and always below 0 ºC for collecting native MM deposited on the Earth during the last million years and could be useful in deciphering the origin and evolution of solid matter in our Solar System and its effects on Earth-bound biogeochemical and geophysical processes including the life origin. The farther analyses of the Vostok AMMs are in a progress.

  12. Organic Analysis in Miller Range 090657 and Buckley Island 10933 CR2 Chondrites: Part 1 In-Situ Observation of Carbonaceous Material

    Science.gov (United States)

    Cao, T.; Nakamura-Messenger, K.; Berger, E. L.; Burton, A. S.; Messenger, S.; Clemett, S. J.

    2016-01-01

    Primitive carbonaceous chondrites contain a wide variety of organic material, ranging from soluble discrete molecules to insoluble unstructured kerogen-like component as well as structured nano-globules of macromolecular carbon. The relationship between the soluble organic molecules, macromolecular organic material, and host minerals are poorly understood. Due to the differences in extractability of soluble and insoluble organic materials, the analysis methods for each differ and are often performed independently. The combination of soluble and insoluble analyses, when performed concurrently, can provide a wider understanding on spatial distribution, and elemental, structural and isotopic composition of organic material in primitive meteorites. Furthermore, they can provide broader perspective on how extraterrestrial organic ma-terials potentially contributed to the synthesis of life's essential compounds such as amino acids, sugar acids, activated phosphates and nucleobases.

  13. Better Alternative to "Astronomical Silicate": Laboratory-Based Optical Functions of Chondritic/Solar Abundance Glass With Application to HD161796

    CERN Document Server

    Speck, A K; Hofmeister, A M

    2015-01-01

    "Astronomical" or "circumstellar" silicate optical functions (real and imaginary indices of refraction n and k have been previously derived from compositionally and structurally disparate samples; past values were compiled from different sources in the literature, and are essentially kluges of observational, laboratory, and extrapolated or interpolated values. These synthetic optical functions were created because astronomers lack the quantitative data on amorphous silicates at all wavelengths needed for radiative transfer modeling. This paper provides optical functions that (1) are created with a consistent methodology, (2) use the same sample across all wavelengths, and (3) minimize interpolation and extrapolation wherever possible. We present electronic data tables of optical functions derived from mid-ultraviolet to far-infrared laboratory transmission spectra for two materials: iron-free glass with chondritic/solar atmospheric abundances, and metallic iron. We compare these optical functions to other pop...

  14. Shock effects and argon loss in samples of the Leedey L6 chondrite experimentally shocked to 29-70 GPa pressures

    Science.gov (United States)

    Bogard, Donald; Horz, Fred; Johnson, Pratt

    1987-01-01

    The recovery of polished 600-micron-thick 7-mm-diameter disk samples and powder samples of the Leedey L6 chondrite from 29-70-GPa experimental shocks is investigated experimentally under vacuum conditions, with a focus on the possible direct shock loss of radiogenic Ar. The results of petrographic examination of the shocked samples and Ar isotope measurements are presented in tables, graphs, and micrographs and characterized in detail. The principal damage mechanisms are identified as mechanical disaggregation and increasing cataclasis, with little melting. The degassing of radiogenic Ar is found to be relatively modest and to increase with shock pressure and sample porosity; it is attributed to a combination of mechanical grain disruption and feldspar melting. It is inferred that Ar loss in naturally shocked materials (especially those showing few signs of melting) probably occurs during extended exposure to high temperatures during impact formation.

  15. Mobility of iron and nickel at low temperatures: Implications for 60Fe-60Ni systematics of chondrules from unequilibrated ordinary chondrites

    Science.gov (United States)

    Telus, Myriam; Huss, Gary R.; Ogliore, Ryan C.; Nagashima, Kazuhide; Howard, Daryl L.; Newville, Matthew G.; Tomkins, Andrew G.

    2016-04-01

    The Fe and Ni isotopic composition of ferromagnesian silicates in chondrules from unequilibrated ordinary chondrites (UOCs) have been used to estimate the initial abundance of the short-lived radionuclide, 60Fe, in the early Solar System. However, these estimates vary widely, and there are systematic discrepancies in initial 60Fe/56Fe ratios inferred from in situ and bulk analyses of chondrules. A possible explanation is that the Fe-Ni isotope system in UOC chondrules has not remained closed (a necessary condition for isotopic dating), and Fe and Ni have been redistributed since the chondrules formed. In order to evaluate this, we collected high-spatial-resolution X-ray fluorescence (XRF) maps of UOC chondrules to better understand the distribution and mobility of Fe and Ni at the low metamorphic temperatures of these chondrites. We used synchrotron X-ray-fluorescence microscopy to map the distribution of Fe, Ni and other elements in portions of 71 chondrules from 8 UOCs (types 3.00-3.2). The synchrotron XRF maps show clear enrichment of Fe and/or Ni in fractures ranging down to micrometer scale in chondrules from all UOCs analyzed for this study regardless of petrologic type and regardless of whether fall or find, indicating that there was significant exchange of Fe and Ni between chondrules and matrix and that the Fe-Ni system was not closed. Sixty percent of chondrules in Semarkona (LL3.00) have Fe and Ni enrichment along fractures, while 80-100% of chondrules analyzed from the other UOCs show these enrichments. Mobilization was likely a result of fluid transport of Fe and Ni during aqueous alteration on the parent body and/or during terrestrial weathering. In situ and bulk Fe-Ni analyses that incorporate extraneous Fe and Ni from chondrule fractures will result in lowering the inferred initial 60Fe/56Fe ratios.

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

    Science.gov (United States)

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

    2014-01-01

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

  17. Elephant Moraine 96029, a very mildly aqueously altered and heated CM carbonaceous chondrite: Implications for the drivers of parent body processing

    Science.gov (United States)

    Lee, Martin R.; Lindgren, Paula; King, Ashley J.; Greenwood, Richard C.; Franchi, Ian A.; Sparkes, Robert

    2016-08-01

    Elephant Moraine (EET) 96029 is a CM carbonaceous chondrite regolith breccia with evidence for unusually mild aqueous alteration, a later phase of heating and terrestrial weathering. The presence of phyllosilicates and carbonates within chondrules and the fine-grained matrix indicates that this meteorite was aqueously altered in its parent body. Features showing that water-mediated processing was arrested at a very early stage include a matrix with a low magnesium/iron ratio, chondrules whose mesostasis contains glass and/or quench crystallites, and a gehlenite-bearing calcium- and aluminium-rich inclusion. EET 96029 is also rich in Fe,Ni metal relative to other CM chondrites, and more was present prior to its partial replacement by goethite during Antarctic weathering. In combination, these properties indicate that EET 96029 is one of the least aqueously altered CMs yet described (CM2.7) and so provides new insights into the original composition of its parent body. Following aqueous alteration, and whilst still in the parent body regolith, the meteorite was heated to ∼400-600 °C by impacts or solar radiation. Heating led to the amorphisation and dehydroxylation of serpentine, replacement of tochilinite by magnetite, loss of sulphur from the matrix, and modification to the structure of organic matter that includes organic nanoglobules. Significant differences between samples in oxygen isotope compositions, and water/hydroxyl contents, suggests that the meteorite contains lithologies that have undergone different intensities of heating. EET 96029 may be more representative of the true nature of parent body regoliths than many other CM meteorites, and as such can help interpret results from the forthcoming missions to study and return samples from C-complex asteroids.

  18. Silica and Pyroxene in IVA Irons; Possible Formation of the IVA Magma by Impact Melting and Reduction of L-LL-Chondrite Materials Followed by Crystallization and Cooling

    Science.gov (United States)

    Wasson, John T.; Matsunami, Yoshiyuki; Rubin, Alan E.

    2006-01-01

    Group IVA is a large magmatic group of iron meteorites. The mean DELTA O-17 (= delta O-17 - 0.52(raised dot) delta O-18) of the silicates is approx. plus or minus 1.2%o, similar to the highest values in L chondrites and the lowest values in LL chondrites; delta O-18 values are also in the L/LL range. This strongly suggests that IVA irons formed by melting L-LL parental material, but the mean Ni content of IVA irons (83 mg/g) is much lower than that of a presumed L-LL parent (approx. 170 mg/g) and the low-Ca pyroxene present in two IVA meteorites is Fs13, much lower than the Fs20-29 values in L and LL chondrites. Thus, formation from L-LL precursors requires extensive addition of metallic Fe, probably produced by reduction of FeS and FeO. Group IVA also has S/Ni, Ga/Ni, and Ge/Ni ratios that are much lower than those in L-LL chondrites or any chondrite group that preserves nebular compositions, implying loss of these volatile elements during asteroidal processing. We suggest that these reduction and loss processes occurred near the surface of the asteroid during impact heating, and resulted partly from reduction by C, and partly from the thermal dissociation of FeS and FeO with loss of O and S. The hot (approx. 1770 K) low-viscosity melt quickly moved through channels in the porous asteroid to form a core. Two members of the IVA group, Sao Joao Nepomuceno (hereafter, SJN) and Steinbach, contain moderate amounts of orthopyroxene and silica, and minor amounts of low-Ca clinopyroxene. Even though SJN formed after approx. 26% crystallization and Steinbach formed after approx. 77% Crystallization of the IVA core, both could have originated within several tens of meters of the core-mantle interface if 99% of the crystallization occurred from the center outwards. Two other members of the group (Gibeon and Bishop Canyon) contain tabular tridymite, which we infer to have initially formed as veins deposited from a cooling SiO-rich vapor. The silicates were clearly introduced

  19. Physical and petrologic properties of ordinary chondrites and their taxonomic parameters%普通球粒陨石的物理和岩石学性质及其分类参数

    Institute of Scientific and Technical Information of China (English)

    王道德; 王桂琴

    2011-01-01

    不同球粒陨石群的物理和岩石学性质,包括球粒的平均大小、球粒结构类型、复合球粒、带火成边球粒及含硫化物的比例、化学组成及矿物学特征等可用以划分球粒陨石的化学-岩石类型和小行星类型,这些性质提供了不同球粒陨石群有用的分类参数及其形成环境的信息.由于不同球粒陨石群的△17O与日心距离存在有相关关系,因此,依据不同球粒陨石群形成时的尘粒量和△17O值随着距太阳距离的增大依次形成:EH-EL、OC(H、L、LL)、R、CR、CV-CK、CM-CO球粒陨石群,并推测早期太阳星云内曾发生过连续的化学分馏作用.%The physical and petrologic properties of the different chondrite groups, including mean size of the chondrules, proportions of the chondrule textural types, proportions of compound chondrule, the proportions of chondrules with igneous rims. and the proportions of chondrules that contain sulfide, chemical compositions and mineral features derived from the early solar nebula are used to classify chemical-petrologic types and asteroids.These properties provided useful taxonomic parameters for different chondrite group (EH, EL, H, L. LL. R, CV,CK. CR, CM, CO) and the information of their formation environment in which chondrules formed. There is correlation between △17O and heliocentric distance for these chondrite groups. Thus, different chondrite groups may be put in the order of EH-EL. OC (H, L, LL), R, CR. CV-CK. CM-CO, with increasing heliocentric formation distance. based on the amount of dust present where they formed and △17O values of different chondrite groups.We infer that continual chemical fractionation occurred in the early solar system.

  20. Comparison of the oxidation state of Fe in comet 81P/Wild 2 and chondritic-porous interplanetary dust particles

    Energy Technology Data Exchange (ETDEWEB)

    Ogliore, Ryan C.; Butterworth, Anna L.; Fakra, Sirine C.; Gainsforth, Zack; Marcus, Matthew A.; Westphal, Andrew J.

    2010-07-16

    The fragile structure of chondritic-porous interplanetary dust particles (CP-IDPs) and their minimal parent-body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alterations have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed {approx}300 ng of Wild 2 material - three orders of magnitude more material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are > 2{sigma} different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent-body, or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do not appear to be consistent with the origin of CP-IDPs. However, comets that formed from a different mix of nebular material and are more oxidized than Wild 2 could be the source of CP-IDPs.

  1. Uranium-lead age of the Bruderheim L6 chondrite and the 500-Ma shock event in the L-group parent body

    International Nuclear Information System (INIS)

    Measured Pb-Pb whole meteorite data for the Bruderheim L6 chondrite scatter slightly about a line passing above Canon Diablo lead and yielding an age of 4.482 + 0.017 Ga, using the terrestrial 238U/235U ratio of 137.88. The measured U isotopic composition for Bruderheim, using the dissolution procedures employed for these U-Pb studies, is near the terrestrial composition. In the concordia diagram the U-Pb data chiefly plot above the concordia curve and define a line which intersects the concordia curve at 4.536 + 0.006 Ga and 0.495 Ga, but the data for Bruderheim cannot be understood at all in terms of the more usual two- or three-stage episodic U-Pb models involving a fixed μ-value in the first stage. Most samples show an apparent excess of radiogenic lead for single-stage (closed system) evolution when Canon Diablo troilite is used for the initial lead composition. Evidence is presented to show that the apparent excess radiogenic lead cannot be explained by terrestrial contamination alone. (orig./ME)

  2. Comparison of the Oxidation State of Fe in Comet 81P/Wild 2 and Chondritic-Porous Interplanetary Dust Particles

    CERN Document Server

    Ogliore, R C; Fakra, S C; Gainsforth, Z; Marcus, M A; Westphal, A J

    2010-01-01

    The fragile structure of chondritic-porous interplanetary dust particles (CP- IDPs) and their minimal parent-body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alteration have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed ~300 nanograms of Wild 2 material - three orders of magnitude more material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are >2{\\sigma} different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent body, or parent bodies, of CP-IDPs. If all J...

  3. Spinel-bearing, Al-rich chondrules in two chondrite finds from Roosevelt County, New Mexico - Indicators of nebular and parent body processes

    Science.gov (United States)

    Mccoy, Timothy J.; Pun, Aurora; Keil, Klaus

    1991-01-01

    Two rare spinel-bearing Al-rich chondrules are identified in chondrite finds from Roosevelt County, New Mexico-RC 071 (L4) and RC 072 (L5). These chondrules have unusual mineralogies dominated by highly and asymmetrically zoned Al-Cr-rich spinels. Two alternatives exist to explain the origin of this zoning-fractional crystallization or metamorphism. Fractional crystallization formed the zoning of the trivalent cations and caused a localized depletion in chromites around the large Al-Cr-rich spinels. Diffusive exchange and partitioning of Fe and Mg between olivine and spinel during parent-body metamorphism can explain the asymmetric zoning of these elements. The bulk compositions of the chondrules suggest affinities with the Na-Al-Cr-rich chondrules, as would be expected from the abundance of Al-Cr-rich spinels. The most important factors are the temperature to which the molten chondrule was heated and the cooling rate during crystallization. These two chondrules cooled rapidly from near the liquidus, as indicated by the zoning, occurrence and sizes of spinels, radiating chondrule textures and localized chromite depletions.

  4. The case for vestiges of early solar system biota in carbonaceous chondrites: petroleum geochemical snapshots and possible future petroleum prospects on Mars expedition

    Science.gov (United States)

    Mukhopadhyay, Prasanta K.; Mossman, David J.; Ehrman, James M.

    2007-09-01

    This research documents the analysis and interpretation of selected Carbonaceous Chondrites (CC) including Murchison, Allende, NWA 3003, Dhofar 735, Orgueil, Tagish Lake and Vigarano using organic petrology, scanning electron microscopy, and petroleum geochemistry. The kerogen microstructures and bitumen within CCs closely resemble remnant 2.5 Ga terrestrial microbial-like structures and their biodegraded components and solid bitumen. In both instances, organoclasts are associated with framboidal iron sulfides or oxides and clay-like minerals. The organic-rich kerogens within three CCs (especially Murchison) might have served as petroleum source rocks for the early generation of hydrocarbons. The maturity varies between 0.7% (Orgueil) and 1.24% (Murchison), to 5.1 % Ro (Vigarano) with predicted maturation temperatures of 100° to 475°C. Geochemical analysis of selected CCs (Murchison, Orgueil, and Tagish Lake) reveal the organic richness and the presence of low molecular weight n-alkanes (C 10 to C 20), complex cyclo-and isoalkanes, nonhydrocarbons, elemental sulfur with abundant aromatic compounds, most of them similar to bacterial and algal derived petroleum products. Apart from the concept of panspermia, the data highlights that three CCs sustained a formation temperature (oil biomarkers. Therefore, the authors propose a model of a "universal unconventional petroleum system", which implies a prospect of oil and gas within the Martian environment and elsewhere within the Solar System.

  5. Extreme 54Cr-rich nano-oxides in the CI chondrite Orgueil -Implication for a late supernova injection into the Solar System

    CERN Document Server

    Qin, Liping; Alexander, Conel M O'D; Wang, Jianhua; Stadermann, Frank J; Carlson, Richard W; 10.1016/j.gca.2010.10.017

    2011-01-01

    Systematic variations in 54Cr/52Cr ratios between meteorite classes (Qin et al., 2010a; Trinquier et al., 2007) point to large scale spatial and/or temporal isotopic heterogeneity in the solar protoplanetary disk. Two explanations for these variations have been proposed, with important implications for the formation of the Solar System: heterogeneous seeding of the disk with dust from a supernova, or energetic-particle irradiation of dust in the disk. The key to differentiating between them is identification of the carrier(s) of the 54Cr anomalies. Here we report the results of our recent NanoSIMS imaging search for the 54Cr-rich carrier in the acid-resistant residue of the CI chondrite Orgueil. A total of 10 regions with extreme 54Cr-excesses ({\\delta}54Cr values up to 1500 %) were found. Comparison between SEM, Auger and NanoSIMS analyses showed that these 54Cr-rich regions are associated with one or more sub-micron (typically less than 200 nm) Cr oxide grains, most likely spinels. Because the size of the N...

  6. Origins of Al-rich chondrules: Clues from a compound Al-rich chondrule in the Dar al Gani 978 carbonaceous chondrite

    Science.gov (United States)

    Zhang, Ai-Cheng; Itoh, Shoichi; Sakamoto, Naoya; Wang, Ru-Cheng; Yurimoto, Hisayoshi

    2014-04-01

    Aluminum-rich chondrules are one of the most interesting components of primitive chondrites, because they have characteristics that are similar to both Ca, Al-rich inclusions (CAIs) and ferromagnesian chondrules. However, their precursor and formation history remain poorly constrained, especially with respect to their oxygen isotopic distributions. In this study, we report on the petrography, mineralogy, oxygen isotope ratios, and rare-earth-element compositions of a sapphirine-bearing Al-rich chondrule (SARC) in the ungrouped chondrite Dar al Gani (DaG) 978. The SARC has a complex core-mantle-rim texture; while both the core and the mantle are mainly composed of Al-rich enstatite and anorthite with minor amounts of mesostasis, these regions are distinguished by the presence of Fe-rich spinel and sapphirine in the core and their absence in the mantle. The rim of the SARC consists mainly of Fe-rich olivine, enstatite, and Fe-Ni metal. Spinel and some olivine grains in the SARC are 16O-rich, with Δ17O values down to -20‰ and -23‰, respectively. Enstatite, sapphirine, and most olivine grains have similar Δ17O values (∼ -7‰), which are lower than those of anorthite and the mesostasis (including augite therein) (Δ17O: ∼ -3‰). Mesostasis from both the core and mantle have Group II rare-earth-element (REE) patterns; however, the core mesostasis has higher REE concentrations than the mantle mesostasis. These observations provide a strong indication that the SARC formed by the melting and crystallization of a mixture of materials from Group II CAIs and ferromagnesian chondrules. Both spinel and olivine with 16O-rich features could be of relict origin. The 16O-poor isotopic compositions of most components in Al-rich chondrules can be explained by oxygen isotopic exchange between the melt and 16O-poor nebular gas (Δ17O: ∼ -7‰) during melting in chondrule-forming regions; whereas the anorthite and mesostasis could have experienced further oxygen isotopic

  7. Formation of replicating saponite from a gel in the presence of oxalate: implications for the formation of clay minerals in carbonaceous chondrites and the origin of life

    Science.gov (United States)

    Schumann, Dirk; Hartman, Hyman; Eberl, Dennis D.; Sears, S. Kelly; Hesse, Reinhard; Vali, Hojatollah

    2012-01-01

    The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (n(C)=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth.

  8. Formation of replicating saponite from a gel in the presence of oxalate: implications for the formation of clay minerals in carbonaceous chondrites and the origin of life.

    Science.gov (United States)

    Schumann, Dirk; Hartman, Hyman; Eberl, Dennis D; Sears, S Kelly; Hesse, Reinhard; Vali, Hojatollah

    2012-06-01

    The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (n(C)=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth.

  9. Microstructural constraints on complex thermal histories of refractory CAI-like objects in an amoeboid olivine aggregate from the ALHA77307 CO3.0 chondrite

    Science.gov (United States)

    Han, Jangmi; Brearley, Adrian J.

    2016-06-01

    We have carried out a FIB/TEM study of refractory CAI-like objects in one AOA from the ALHA77307 CO3.0 chondrite. The CAI-like objects in the AOA consist of a zoned sequence with a spinel-rich core through an intergrowth layer of spinel and Al-Ti-rich diopside to a diopside rim. The spinel-rich core consists of polycrystalline aggregates of spinel and ±minor melilite showing equilibrated grain boundary textures. The intergrowth layer contains fine-grained diopside and spinel with minor anorthite with highly curved and embayed grain boundaries. The diopside rim consists of polycrystalline aggregates of diopside. The compositions of pyroxene change significantly outward from Al-Ti-rich diopside in contact with the spinel-rich core to Al-Ti-poor diopside next to the surrounding olivine of the AOA. Overall microstructural and chemical characteristics suggest that the spinel-rich core formed under equilibrium conditions whereas the intergrowth layer is the result of reactions that occurred under conditions that departed significantly from equilibrium. The remarkable changes in formation conditions of the CAI-like objects may have been achieved by transport and injection of refractory objects into a region of a partially-condensed, Ca,Ti-saturated gas which reacted with spinel and melilite to form Al-Ti-rich diopside. Crystallographically-oriented TiO2 nanoparticles decorate the grain boundaries between spinel grains and between spinel and Al-Ti-rich diopside grains. During the disequilibrium back-reaction of spinel with a partially-condensed, Ca,Ti-saturated gas, metastable TiO2 nanoparticles may have condensed by an epitaxial nucleation mechanism and grown on the surface of spinel. These TiO2 nanoparticles are disordered intergrowths of the two TiO2 polymorphs, anatase and rutile. These nanoparticles are inferred to have nucleated as anatase that underwent partial transformation into rutile. The local presence of the TiO2 nanoparticles and intergrowth of anatase and

  10. A combined FE-SEM/EDS and μ-IR analysis of Carbonaceous Chondrites, analogue of the next returned asteroid samples

    Science.gov (United States)

    Dirri, Fabrizio; Palomba, Ernesto; Ferrari, Marco; Longobardo, Andrea; Rotundi, Alessandra

    2016-10-01

    A combined method for the analysis of extraterrestrial samples returned by spacecrafts foresees two different analytical techniques: Field Emission-Scanning Electron Microscope with Energy Dispersive Spectroscopy (FE-SEM/EDS) and Infrared μ-spectroscopy (μ-IR). These are non-destructive analytical techniques that allow obtaining mineral and organic information of the samples: μ-IR spectroscopy is able to provide thermal maps of selected area, whereas FE-SEM/EDS microscopy provides information on sample morphology and chemical composition. The combined results provide a complete overview of the sample mineralogy.In the past, different types of analysis were performed in order to characterise returned asteroid and cometary samples, and meteorites [e.g. 1,2,3]. Waiting for the analyses of the samples to be returned from primitive asteroids targets by Hayabusa 2 and Osiris Rex missions [4,5], we applied the combined FE-SEM/EDS and μ-IR techniques to Carbonaceous Chondrites (CC) meteorites as possible analogues. In particular, we selected 3 samples: Murchinson (CM2 group), characterised by small chondrules and refractory inclusions [6]; Orgueil (CI1 group) characterised by the absence of chondrules and refractory inclusion and with a high degree of hydration [7]; NWA2086 (CV3 group) with considerable amount of large mm-size chondrules, many surrounded by igneous rims [8]. A preliminary analysis was performed on the samples using a Stereo Microscope (Leica M205c) equipped with a digital camera in order to select regions of the samples showing a significant mineralogical heterogeneity.[1] Rotundi, A. et al., Meteorit. & Planet. Scie.,49,4,550–575,2014[2] Matrajt, G. et al.,A&A,416,3,983-990,2004[3] Naraoka, H. et al.,Geochem. J.,46,1,61-72,2012[4] Chasley, R. et al.,Icarus,235,5-22,2014[5] Yoshikawa, M. et al., 47th LPSC Abs,2016[6] Cronin, J.R. and Chang, S.,The Chemistry of Life's Origins, 416,209-258,1993[7] Tomeoka K. and Buseck P.R., Geochimica et Cosmochimica

  11. Carbon and Oxygen Isotope Measurements of Ordinary Chondrite (OC) Meteorites from Antarctica Indicate Distinct Terrestrial Carbonate Species using a Stepped Acid Extraction Procedure Impacting Mars Carbonate Research

    Science.gov (United States)

    Evans, M. E.; Niles, P. B.; Locke, D.

    2015-12-01

    The purpose of this study is to characterize the stable isotope values of terrestrial, secondary carbonate minerals from five OC meteorites collected in Antarctica. These samples were selected for analysis based upon their size and collection proximity to known Martian meteorites. They were also selected based on petrologic type (3+) such that they were likely to be carbonate-free before falling to Earth. This study has two main tasks: 1) characterize the isotopic composition of terrestrial, secondary carbonate minerals formed on meteorites in Antarctica, and 2) study the mechanisms of carbonate formation in cold and arid environments with Antarctica as an analog for Mars. Two samples from each meteorite, each ~0.5g, was crushed and dissolved in pure phosphoric acid for 3 sequential reactions: a) Rx0 for 1 hour at 30°C, b) Rx1 for 18 hours at 30°C, and c) Rx2 for 3 hours at 150°C. CO2 was distilled by freezing with liquid nitrogen from each sample tube, then separated from organics and sulfides with a TRACE GC using a Restek HayeSep Q 80/100 6' 2mm stainless column, and then analyzed on a Thermo MAT 253 IRMS in Dual Inlet mode. This system was built at NASA/JSC over the past 3 years and proof tested with known carbonate standards to develop procedures, assess yield, and quantify expected uncertainties. Two distinct species of carbonates are found based on the stepped extraction technique: 1) Ca-rich carbonate released at low temperatures, and 2) Mg, or Fe-rich carbonate released at high temperatures. Preliminary results indicate that most of the carbonates present in the ordinary chondrites analyzed have δ13C=+5‰, which is consistent with formation from atmospheric CO2 δ13C=-7‰ at -20°C. The oxygen isotopic compositions of the carbonates vary between +4‰ and +34‰ with the Mg-rich and/or Fe-rich carbonates possessing the lowest δ18O values. This suggests that the carbonates formed under a wide range of temperatures. However, the carbonate oxygen

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

    Science.gov (United States)

    Evans, Michael E.

    2015-01-01

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

  13. Re-Os systematics of komatiites and komatiitic basalts at Dundonald Beach, Ontario, Canada: Evidence for a complex alteration history and implications of a late-Archean chondritic mantle source

    Science.gov (United States)

    Gangopadhyay, Amitava; Sproule, Rebecca A.; Walker, Richard J.; Lesher, C. Michael

    2005-11-01

    Osmium isotopic compositions, and Re and Os concentrations have been examined in one komatiite unit and two komatiitic basalt units at Dundonald Beach, part of the 2.7 Ga Kidd-Munro volcanic assemblage in the Abitibi greenstone belt, Ontario, Canada. The komatiitic rocks in this locality record at least three episodes of alteration of Re-Os elemental and isotope systematics. First, an average of 40% and as much as 75% Re may have been lost due to shallow degassing during eruption and/or hydrothermal leaching during or immediately after emplacement. Second, the Re-Os isotope systematics of whole rock samples with 187Re/ 188Os ratios >1 were reset at ˜2.5 Ga, possibly due to a regional metamorphic event. Third, there is evidence for relatively recent gain and loss of Re in some rocks. Despite the open-system behavior, some aspects of the Re-Os systematics of these rocks can be deciphered. The bulk distribution coefficient for Os (D Ossolid/liquid) for the Dundonald rocks is ˜3 ± 1 and is well within the estimated D values obtained for komatiites from the nearby Alexo area and stratigraphically-equivalent komatiites from Munro Township. This suggests that Os was moderately compatible during crystal-liquid fractionation of the magmas parental to the Kidd-Munro komatiitic rocks. Whole-rock samples and chromite separates with low 187Re/ 188Os ratios (Kidd-Munro volcanic assemblage had evolved with a long-term chondritic Re/Os before eruption. The chondritic initial Os isotopic composition of the Kidd-Munro komatiites is indistinguishable from that of the projected contemporaneous convective upper mantle. The uniform chondritic Os isotopic composition of the Kidd-Munro komatiites contrasts with the typical large-scale Os isotopic heterogeneity in the mantle sources for ca. 89 Ma komatiites from the Gorgona Island, arc-related rocks and present-day ocean island basalts. This suggests that the Kidd-Munro komatiites sampled a late-Archean mantle source region that was

  14. Origin of the eclogitic clasts with graphite-bearing and graphite-free lithologies in the Northwest Africa 801 (CR2) chondrite: Possible origin from a Moon-sized planetary body inferred from chemistry, oxygen isotopes and REE abundances

    Science.gov (United States)

    Hiyagon, H.; Sugiura, N.; Kita, N. T.; Kimura, M.; Morishita, Y.; Takehana, Y.

    2016-08-01

    In order to clarify the origin of the eclogitic clasts found in the NWA801 (CR2) chondrite (Kimura et al., 2013), especially, that of the high pressure and temperature (P-T) condition (∼3 GPa and ∼1000 °C), we conducted ion microprobe analyses of oxygen isotopes and rare earth element (REE) abundances in the clasts. Oxygen isotopic compositions of the graphite-bearing lithology (GBL) and graphite-free lithology (GFL) show a slope ∼0.6 correlation slightly below the CR-CH-CB chondrites field in the O three-isotope-diagram, with a large variation for the former and almost homogeneous composition for the latter. The average REE abundances of the two lithologies show almost unfractionated patterns. Based on these newly obtained data, as well as mineralogical observations, bulk chemistry, and considerations about diffusion timescales for various elements, we discuss in detail the formation history of the clasts. Consistency of the geothermobarometers used by Kimura et al. (2013), suggesting equilibration of various elements among different mineral pairs, provides a strong constraint for the duration of the high P-T condition. We suggest that the high P-T condition lasted 102-103 years. This clearly precludes a shock high pressure (HP) model, and hence, strongly supports a static HP model. A static HP model requires a Moon-sized planetary body of ∼1500 km in radius. Furthermore, it implies two successive violent collisions, first at the formation of the large planetary body, when the clasts were placed its deep interior, and second, at the disruption of the large planetary body, when the clasts were expelled out of the parent body and later on transported to the accretion region of the CR chondrites. We also discuss possible origin of O isotopic variations in GBL, and presence/absence of graphite in GBL/GFL, respectively, in relation to smelting possibly occurred during the igneous process(es) which formed the two lithologies. Finally we present a possible

  15. Ordinary chondritic micrometeorites from the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    ShyamPrasad, M.; Rudraswami, N.G.; Babu, E.V.S.S.K.; VijayaKumar, T.

    Extraterrestrial particulate materials on the Earth can originate in the form of collisional debris from the asteroid belt, cometary material, or as meteoroid ablation spherules. Signatures that link them to their parent bodies become obliterated...

  16. Noble gases in twenty Yamato H-chondrites: Comparison with Allan Hills chondrites and modern falls

    Science.gov (United States)

    Loeken, TH.; Scherer, P.; Schultz, L.

    1993-01-01

    Concentration and isotopic composition of noble gases have been measured in 20 H-chrondrites found on the Yamato Mountains ice fields in Antarctica. The distribution of exposure ages as well as of radiogenic He-4 contents is similar to that of H-chrondrites collected at the Allan Hills site. Furthermore, a comparison of the noble gas record of Antarctic H-chrondrites and finds or falls from non-Antarctic areas gives no support to the suggestion that Antarctic H-chrondrites and modern falls derive from differing interplanetary meteorite populations.

  17. The Amino Acid Composition of the Sutter's Mill Carbonaceous Chondrite

    Science.gov (United States)

    Glavin, D. P.; Burton, A. S.; Elsila, J. E.; Dworkin, J. P.; Yin, Q. Z.; Cooper, G.; Jenniskens, P.

    2012-01-01

    In contrast to the Murchison meteorite which had a complex distribution of amino acids with a total C2 to Cs amino acid abundance of approx.14,000 parts-per-billion (ppb) [2], the Sutters Mill meteorite was found to be highly depleted in amino acids. Much lower abundances (approx.30 to 180 ppb) of glycine, beta-alanine, L-alanine and L-serine were detected in SM2 above procedural blank levels indicating that this meteorite sample experienced only minimal terrestrial amino acid contamination after its fall to Earth. Carbon isotope measurements will be necessary to establish the origin of glycine and beta-alanine in SM2. Other non-protein amino acids that are rare on Earth, yet commonly found in other CM meteorites such as aaminoisobutyric acid (alpha-AIB) and isovaline, were not identified in SM2. However, traces of beta-AIB (approx.1 ppb) were detected in SM2 and could be" extraterrestrial in origin. The low abundances of amino acids in the Sutter's Mill meteorite is consistent with mineralogical evidence that at least some parts of the Sutter's Mill meteorite parent body experienced extensive aqueous and/or thermal alteration.

  18. Heavily irradiated grains and neon isotope anomalies in carbonaceous chondrites

    Energy Technology Data Exchange (ETDEWEB)

    Audouze, J.; Bibring, J.P.; Dran, J.C.; Maurette, M.; Walker, R.M.

    1976-06-15

    High-voltage microscope observations of micron-sized grains extracted from a /sup 22/Ne-rich fraction of the Orgueil meteorite give strong experimental evidence for their heavy irradiation. It is further suggested that the excess of /sup 22/Ne measured in the same mineral separate can be explained by low-energy (<10 MeV) production by (p, a) reaction on /sup 25/Mg. A discussion of the astrophysical sites potentially responsible for the peculiar irradiation history of the meteoritic grains is presented. (AIP)

  19. Chemistry and Petrology of Chondrules from the Mokoia CV Chondrite

    Science.gov (United States)

    Jones, R. H.; Schilk, A. J.

    2000-01-01

    Bulk chemical compositions of 94 chondrules from Mokoia have been obtained by INAA. Elemental abundances are correlated with petrology. Chemical and petrological properties are very similar to chondrules from Allende and do not show strong alteration signatures.

  20. Shocked Feldspar in L Chondrites: Deformation, Transformation and Local Melting

    Science.gov (United States)

    Fudge, C.; Sharp, T. G.

    2016-08-01

    We present textures and compositional profiles of partially to completely transformed plagioclase to maskelynite. Evidence for transformation mechanisms, including solid state transformation and crystallization from melt will be discussed.

  1. Solar wind helium, neon and argon released by oxidation of metal grains from the Weston chondrite

    Science.gov (United States)

    Becker, R. H.; Rajan, R. S.; Rambaldi, E. R.

    1986-01-01

    A set of experiments were carried out to test the feasibility of determining unfractionated elemental and isotopic ratios for the noble gases in the presumably ancient solar wind present in the gas rich meteorites. The problems of diffusive loss was avoided by analyzing metal rather than the usual silicates. In order to avoid chemical, and even harsh physical, treatment of the sample, which might have affected the surfaces of metal grains, a means of analyzing the metal in the presence of residual silicate not removed by gentle crushing and magnetic separation was devised. Preliminary results given were obtained by taking advantage of the differing properties of metal and silicates with regard to diffusion. The results suggests that, with some modifications in the choice of pyrolysis and combustion temperatures and in the amount of O2 used, it should be possible, by oxidizing the surfaces of metal grains from gas rich meteorites, to obtain data on solar wind that has not been fractionated by diffusive loss.

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

    CERN Document Server

    Beitz, Eike; Mathieu, Romain; Pack, Andreas; Hezel, Dominik C

    2011-01-01

    We developed an experimental setup to test the hypothesis that accretionary dust rims around chondrules formed in the solar nebula at elevated temperatures. Our experimental method allows us to form dust rims around chondrule-analogs while being levitated in an inert-gas flow. We used micrometer-sized powdered San Carlos olivine to accrete individual dust particles onto the chondrule-analog at a temperature of 1100{\\deg}C. The resulting dust-rims were analyzed by means of two different techniques: one sample was investigated with non-destructive micro computer tomography, the other with a scanning electron microscope. Both methods give very similar results for the dust-rim structure and a mean dust-rim porosity of 60 percent, demonstrating that both methods are equally well suited for sample analysis. The chondrule-analog's bulk composition has no measurable effect on the accretion efficiency of the dust. We measured the chemical composition of chondrule-analog and dust-rim to check whether elemental exchange...

  3. The collisional evolution of undifferentiated asteroids and the formation of chondritic meteoroids

    CERN Document Server

    Beitz, Eike; Parisi, M Gabriela; Trigo-Rodríguez, Josep M

    2016-01-01

    Most meteorites are fragments from recent collisions experienced in the asteroid belt. In such a hyper-velocity collision, the smaller collision partner is destroyed, whereas a crater on the asteroid is formed or it is entirely disrupted, too. The present size distribution of the asteroid belt suggests that an asteroid with 100 km radius is encountered $10^{14}$ times during the lifetime of the Solar System by objects larger than 10 cm in radius; the formed craters cover the surface of the asteroid about 100 times. We present a Monte Carlo code that takes into account the statistical bombardment of individual infinitesimally small surface elements, the subsequent compaction of the underlying material, the formation of a crater and a regolith layer. For the entire asteroid, 10,000 individual surface elements are calculated. We compare the ejected material from the calculated craters with the shock stage of meteorites with low petrologic type and find that these most likely stem from smaller parent bodies that ...

  4. What Do We Know About Elemental Bulk Chondrule Compositions? Presenting the ChondriteDB Database

    Science.gov (United States)

    Hezel, D. C.; Harak, M.; Libourel, G.

    2016-08-01

    We compiled an elemental chondrule and matrix database for Big Data analyses (>3500 entires in 107 categories). We use this first overview of the entire chondrule population for comparisons and conclusions on chondrule formation conditions.

  5. Chemical Signatures of Interstellar Dusts Preserved in Primitive Chondrites and Inner Planets of the Solar System

    Science.gov (United States)

    Yin, Qing-Zhu

    2002-01-01

    We show that the inheritance of interstellar materials by the solar system is not only documented by the presence of presolar grains, various isotopic anomalies, but also expressed in the chemical element distribution in the inner solar system. Additional information is contained in the original extended abstract.

  6. Hidden secrets of deformation: Impact-induced compaction within a CV chondrite

    Science.gov (United States)

    Forman, L. V.; Bland, P. A.; Timms, N. E.; Collins, G. S.; Davison, T. M.; Ciesla, F. J.; Benedix, G. K.; Daly, L.; Trimby, P. W.; Yang, L.; Ringer, S. P.

    2016-10-01

    The CV3 Allende is one of the most extensively studied meteorites in worldwide collections. It is currently classified as S1-essentially unshocked-using the classification scheme of Stöffler et al. (1991), however recent modelling suggests the low porosity observed in Allende indicates the body should have undergone compaction-related deformation. In this study, we detail previously undetected evidence of impact through use of Electron Backscatter Diffraction mapping to identify deformation microstructures in chondrules, AOAs and matrix grains. Our results demonstrate that forsterite-rich chondrules commonly preserve crystal-plastic microstructures (particularly at their margins); that low-angle boundaries in deformed matrix grains of olivine have a preferred orientation; and that disparities in deformation occur between chondrules, surrounding and non-adjacent matrix grains. We find heterogeneous compaction effects present throughout the matrix, consistent with a highly porous initial material. Given the spatial distribution of these crystal-plastic deformation microstructures, we suggest that this is evidence that Allende has undergone impact-induced compaction from an initially heterogeneous and porous parent body. We suggest that current shock classifications (Stöffler et al., 1991) relying upon data from chondrule interiors do not constrain the complete shock history of a sample.

  7. The "White Angel": A Wollastonite-Bearing Refractory Inclusion in the Leoville Chondrite

    Science.gov (United States)

    Caillet, C. L. V.; Buseck, P. R.

    1992-07-01

    An unusual coarse-grained Ca-Al-rich inclusion (CAI) was discovered in the Leoville CV3 meteorite. The inclusion has a smooth shape, is flattened, and measures ~4 mm in maximum dimension. This compact CAI has a predominantly igneous texture but shows the effects of solid-state recrystallization. It displays multiple deformation features, as is common in other Leoville samples (Caillet et al., 1992). Some large crystals are twisted or oriented parallel to the lineation of the rock or show undulatory extinction and kink-banding. The inclusion consists mainly of melilite, but a striking feature is the occurrence of large wollastonite crystals forming areas up to 400 micrometers long. Such large wollastonites have not previously been reported from a CAI core. Other primary phases are perovskite (up to 120 micrometers across) and few Ti-V-rich fassaite crystals. Sparse idiomorphic crystals (10 micrometers across) of a Ti-rich mineral phase are poikilitically enclosed within melilite. Surprisingly, spinels are absent in this CAI. In transmitted light, the pyroxenes are an intense green color, and perovskite appears reddish pink to light violet. Wollastonite shows a pronounced blue luminescent color under the electron beam. This unique white inclusion is surrounded by relatively simple and regular rimming sequence consisting, from the inside outward, of spinel+perovskite, Al-rich melilite, Al-diopside, and olivine layers. Almost no alteration products, such as grossular or sodalite, were encountered around the CAI. However, two tiny anorthite crystals are partly replaced by nepheline. Calcite fills cracks perpendicular to the long axis of the CAI. However, some calcite patches (apparently replacing wollastonite) appear to have preexisted the faulting event(s). The texture indicates melilite was the first mineral to crystallize. Compositions range from Ak(sub)2 at the rim to Angstrom k(sub)40 in the interior with a mean value of Ak(sub)24. In most minerals, Na2O is below the detection limit but it reaches 0.15 wt% in Ak-rich melilite. FeO (Ca-Ti-phase found in Essebi by El Goresy et al. (1984) and contains 26.6 to 28.2 wt% TiO2 and probably crystallized late from the CAI. The bulk composition of the inclusion as determined by broad-beam microprobe methods is (in wt%): SiO2 ~ 29.59, Al2O3 ~ 24.65, CaO ~ 39.94, TiO2 ~ 2.02, MgO ~ 3.73, FeO ~ 0.1, MnO+Cr2O3 Ca and Ti and low Al contents together with the textures and mineral chemistry suggest a complex history for this anomalous type-A CAI. The "white angel" presumably represents an ancient condensate from an Al-depleted solar nebula reservoir that was subsequently melted under reducing conditions. References Caillet C., MacPherson G.J. and Zinner E.K. (1992) submitted to Geochim. Cosmochim. Acta. Beckett J.R. and Grossman L. (1986) Lunar and Planet. Sci. (abstract) 17, 36-37. Dowty E. and Clark J.R. (1973) Amer. Mineral. 58, 230-242. El Goresy A., Palme H., Yabuki H., Nagel K., Herrwerth I. and Ramdohr P. (1984) Geochim. Cosmochim. Acta. 48, 2283-2298.

  8. Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

    DEFF Research Database (Denmark)

    Van Kooten, Elishevah M M E; Wielandt, Daniel; Schiller, Martin;

    2016-01-01

    product of (26)Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling (26)Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last...

  9. Olivine Microstructures in the Miller Range 99301 (LL6) Ordinary Chondrite

    Science.gov (United States)

    Hutson, M. L.; Hugo, R.; Ruzicka, A. M.; Rubin, A. E.

    2009-03-01

    We used Transmission Electron Microscope (TEM) imaging to examine microstructures in MIL 99301 (LL6) olivine grains in order to understand more fully this meteorite’s deformation and thermal history.

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

    Science.gov (United States)

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

    2003-01-01

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

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

    OpenAIRE

    Beitz, Eike; Blum, Jürgen; Mathieu, Romain; Pack, Andreas; Hezel, Dominik C.

    2011-01-01

    We developed an experimental setup to test the hypothesis that accretionary dust rims around chondrules formed in the solar nebula at elevated temperatures. Our experimental method allows us to form dust rims around chondrule-analogs while being levitated in an inert-gas flow. We used micrometer-sized powdered San Carlos olivine to accrete individual dust particles onto the chondrule-analog at a temperature of 1100{\\deg}C. The resulting dust-rims were analyzed by means of two different techni...

  12. Iron Oxidation States of Matrix in Carbonaceous Chondrites Acfer 094 and MIL 07687

    Science.gov (United States)

    Vaccaro, E.; King, A. J.; Schofield, P. F.; Abyaneh, M. K.; Kaulich, B.; Russell, S. S.

    2016-08-01

    STXM Fe-oxidation state study in Acfer 094 and MIL 07687 matrix revealed high Fe3+/ΣFe ratios likely to be a primordial signature. Terrestrial weathering cannot be ruled out but is unlikely to have a pervasive effect throughout entire meteorites.

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

    Science.gov (United States)

    Kornacki, A. S.; Fegley, B.

    1984-02-01

    The evaluation of three models of the origin of spinel-rich chondrules and inclusions presented here includes new calculations of the major-element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval. Condensation calculations show that spinel-rich chondrules did not crystallize from metastable liquid condensates, and that spinel-rich inclusions are not aggregates of refractory nebular condensates. It is proposed that spinel-rich objects are fractionated distillation residues of small aggregates of primitive dust that lost Ca, Si-rich partial melts by evaporation, ablation, or splashing during collisions. This model also explains why spinel-rich chondrules and inclusions (1) are usually smaller than melilite-rich chondrules and inclusions; (2) often have highly fractionated trace-element compositions; and (3) usually do not contain Pt-metal nuggets even when they are more enriched in the Pt-group metals than nugget-bearing melilite-rich objects.

  14. Mid-infrared spectra of the shocked Murchison CM chondrite: comparison with astronomical observations of dust in debris disks

    OpenAIRE

    Morlok, A.; Koike, C.; Tomioka, N; Mann, I.; Tomeoka, K.

    2010-01-01

    We present laboratory mid-infrared transmission/absorption spectra obtained from matrix of the hydrated Murchison CM meteorite experimentally shocked at peak pressures of 10-49 GPa, and compare them to astronomical observations of circumstellar dust in different stages of the formation of planetary systems. The laboratory spectra of the Murchison samples exhibit characteristic changes in the infrared features. A weakly shocked sample (shocked at 10 GPa) shows almost no changes from the unshoc...

  15. Oxygen isotope and petrological study of silicate inclusions in IIE iron meteorites and their relationship with H chondrites

    OpenAIRE

    Mcdermott, Kathryn H.; Greenwood, Richard C.; Scott, Edward R. D.; Franchi, Ian A.; Anand, Mahesh

    2015-01-01

    The origin of silicate-bearing irons, especially those in groups IAB, IIICD, and IIE, is poorly understood as silicate should have separated rapidly from molten metal. Here we report the results of high precision oxygen isotope analysis of silicate inclusions in eleven group IIE meteorites and a petrological study of silicate inclusions in ten IIE irons including those in Garhi Yasin and Tarahumara, which have not been described in detail before. Oxygen isotopes have also been analysed in 20 ...

  16. Noble gases, C,N, and Si isotopes in interstellar SiC form the Murchison carbonaceous chondrite

    Science.gov (United States)

    Ming, Tang; Anders, Edward; Zinner, Ernst

    1988-01-01

    Isotopic measurements of presolar interstellar silicon carbide are presented. Silicon carbide was recently identified in a primitive meteorite Murray. There exists strong evidence that the silicon carbide predates the formation of the solar system and originated in the atmospheres of certain stars. Thus, this material provides a link with its stellar sources and gives the opportunity to study processes taking place in distant stars.

  17. Isotopic anomalies of noble gases in meteorites and their origins. VI Presolar components in the Murchison C2 chondrite

    Science.gov (United States)

    Alaerts, L.; Lewis, R. S.; Matsuda, J.-I.; Anders, E.

    1980-01-01

    Rare gases were analyzed by stepped heating in five fractions of a chemically resistant residue from Murchison that had been separated according to grain size and resistance to HClO4. Nine gas components were recognized, of which three appear to be presolar: (1) Ne-E(H) released at 1000-1600 C and located in spinel; (2) Ne-E(L) released at less than 800 C and apparently located in a carbonaceous phase of grain size up to 10 microns; and (3) s-process Xe and Kr released at 1200-1600 C and located in a poorly characterized, possibly carbonaceous phase, distinct from the host phase of Ne-E(L).

  18. Beryllium-Boron Systematics of Refractory Inclusions in CR2 and CV3 Chondrites: Evidence for 10Be Heterogeneity

    Science.gov (United States)

    Dunham, E.; Wadhwa, M.; Simon, S.; Grossman, L.

    2016-08-01

    Be-B systematics of Allende (CV3), Axtell (CV3), and NWA 5028 (CR2) CAIs suggests that 10Be was distributed heterogeneously in the early solar system which implies that 10Be was produced in the solar nebula by irradiation of nebular gas or dust.

  19. HSE Abundances in Angrites and HEDs: Core-Mantle Equilibration or Late Accretion Addition of a Chondritic Component

    Science.gov (United States)

    Rai, N.; Downes, H.; Smith, C. L.

    2016-08-01

    Using metal-silicate partitioning of HSEs together with their mantle abundances in Vesta and the APB respectively, we test whether formation of a metallic core could have led to the observed abundances of the HSEs, in the mantles of these bodies.

  20. Chondritic Models of 4 Vesta: Comparison of Predicted Internal Structure and Surface Composition/Mineralogy with Data from the Dawn Mission

    Science.gov (United States)

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

    2012-01-01

    Understanding the physical and chemical processes which led to the formation of the terrestrial planets remains one of the principal challenges of the Earth and planetary science communities. However, direct traces of the earliest stages of planet building have generally been wiped out on larger bodies such as the Earth or Mars, obscuring our view of how that process occurred. On the other hand, the planet building process would appear to have been arrested prematurely in the region between Mars and Jupiter, now populated by several hundred thousand compositionally diverse objects that escaped accretion into larger planets. Of these, the asteroid 4 Vesta is of particular interest as it is large (520 km diameter), and known to have a basaltic surface dominated by pyroxenes [1, 2]. Furthermore, visible-IR spectra of Vesta obtained by ground and space-based telescopes are remarkably similar to laboratory spectra measured on meteorites of the Howardite-Eucrite-Diogenite clan (HED), leading to the paradigm that the HEDs came from Vesta [2]. Geochemical and petrological studies of the HEDs confirm the differentiated nature of the near-surface region of their parent body, and imply that crust extraction occurred well within the first 10Ma of solar system history [3]. Vesta is therefore a prime target for studies that aim to constrain the earliest stages of planet building, and for that reason it is currently the subject of the Dawn mission [4].

  1. Stable Chlorine Isotopes and Elemental Chlorine by Thermal Ionization Mass Spectrometry and Ion Chromatography; Martian Meteorites, Carbonaceous Chondrites and Standard Rocks

    Science.gov (United States)

    Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C.-Y.; Fujitani, T.; Okano, O.

    2011-01-01

    Recently significantly large mass fractionation of stable chlorine isotopes has been reported for terrestrial and lunar samples [1,2]. In addition, in view of possible early solar system processes [3] and also potential perchlorate-related fluid/microbial activities on the Martian surface [4,5], a large chlorine isotopic fractionation might be expected for some types of planetary materials. Due to analytical difficulties of isotopic and elemental analyses, however, current chlorine analyses for planetary materials are controversial among different laboratories, particularly between IRMS (gas source mass spectrometry) and TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1,6,7] for isotopic analyses, as well as between those doing pyrohydrolysis and other groups [i.e. 6,8]. Additional careful investigations of Cl isotope and elemental abundances are required to confirm real chlorine isotope and elemental variations for planetary materials. We have developed a TIMS technique combined with HF-leaching/ion chromatography at NASA JSC that is applicable to analysis of small amounts of meteoritic and planetary materials. We present here results for several standard rocks and meteorites, including Martian meteorites.

  2. The 'Porky' Inclusion from the Axtell Carbonaceous Chondrite: A Hercynite-bearing Condensate with Large 48Ca and 50Ti Excesses

    Science.gov (United States)

    Caillet, C.; Zinner, E.

    1995-09-01

    Only a few hercynite-rich refractory inclusions have been identified to date [1,2]. Porky (450 micrometers long) is an unusual CAI with texturally distinct regions and dominant intergrown oxide mineral phases [3]. The core is a symplectitic vermicular intergrowth of ubiquitous ferroan spinel and ilmenite. Inwards branching of ilmenite crystals and projecting fan-shaped hibonite from the borders suggest crystallization from a fast cooling melt. Three marginal regions are mineralogically identical to the core: two fine-grained areas with acicular corroded crystals contrast with an altered spinel area. The inclusion is entirely rimmed by yellow luminescing Al-diopside. Hibonite exhibits pale orange luminescence. Broad beam analyses reveal high FeO (22.5 wt %) and low CaO/Al2O3 (0.024) for the whole CAI [3]. Si, Al and Ti concentrations are very similar to those of CM inclusions. There are no significant chemical differences between the coarse-grained core and the fine-grained regions. Hibonite shows widely varying concentrations (in wt %) of TiO2 (1.5-6.8), MgO (1.2-3.6) and FeO (0.7-4.7). Spinel contains much FeO (20.5-27). Hercynite close to the border of the inclusion next to hibonite has high MgO (11 wt%) and small amounts of Cr2O3 (0.15-1.55) and V2O3 (0.1-0.3), implying a melt origin. The Al-rich, Si-poor composition indicates that Porky experienced higher temperatures than CV3 inclusions. The presence of Fe-rich mineral phases, the lack of metal grains, the relatively high NiO concentration (average = 0.25), and the orange luminescence of hibonite indicate formation or re-equilibration in an oxidizing environment. Trace element patterns are basically volatility-fractionated and mostly ultrarefractory-depleted but vary from a Group II pattern in hercynite (to a lesser extent in hibonite and diopside) to extreme excesses of the less refractory elements Nb, Eu, Tm and Yb in a fine-grained region (Fig. 1). These patterns indicate condensation from a UR-depleted gas at varying temperatures (highest for the core, lowest for the fine-grained regions) and under varying redox conditions and trace element compositions. The refractory trace elements measured in hercynite are likely to reside in ilmenite (the abundances in this phase would then be ~15 times higher than shown in Fig. 1 for hercynite). In contrast to large 48Ca and 50Ti depletions in hibonite-hercynite inclusion Lanc HH-1 [2], Porky shows extreme excesses in 48Ca (37.3+/-5.9 (2s) per mil in hibonite and 27.4+/-4.8 per mil in diopside) and 50Ti (~62 per mil in hibonite and ilmenite). No clear 26Mg excess and no Mg and Fe isotopic mass fractionation were detected. Fe isotopic ratios in hercynite are normal; the Allende inclusion EK1-4-1 thus remains the only object in which a large 58Fe excess is associated with 48Ca and 50Ti excesses [4]. References: [1] Brigham C. A. et al. (1986) LPSC XVII, 85-86. [2] Fahey A. J. et al. (1994) GCA, 58, 4779-4793. [3] Caillet C. (1994) Meteoritics, 29, 453-454. [4] V"lkening J. and Papanastassiou D. A. (1989) Astrophys. J., 347, L43-L46.

  3. Ion microprobe analyses of oxygen three-isotope ratios of chondrules from the Sayh al Uhaymir 290 CH chondrite using a multiple-hole disk

    Digital Repository Service at National Institute of Oceanography (India)

    Nakashima, D.; Ushikubo, T.; Gowda, R.N.; Kita, N.T.; Valley, J.W.; Naga, K.

    challenges. We produced a new sample holder disk with multiple holes (three holes and seven holes), in which epoxy disks containing a single unknown sample and a standard grain are cast and polished. Performance tests for oxygen two-isotope analyses using San...

  4. Petrological Characteristics of the Fine-Grained CAIs from the Reduced CV Chondrites Thiel Mountains 07003 and 07007, and Origin of Anorthite

    Science.gov (United States)

    Kim, H.; Choi, B.-G.

    2016-08-01

    We classified nodules of FGIs into three types; melilite-bearing without anorthite, anorthite-bearing without melilite, and both melilite- and anorthite-bearing. The former two types are dominant while the latter is relatively rare.

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

    DEFF Research Database (Denmark)

    Olsen, Mia Bjørg Stolberg; Schiller, Martin; Krot, Alexander N.;

    2013-01-01

    Chondrules are igneous spherical objects preserved in chondritic meteorites and believed to have formed during transient heating events in the solar protoplanetary disk. Chondrules present in the metal-rich CB chondrites show unusual chemical and petrologic features not observed in other chondrit...

  6. Magnesium isotope evidence for single stage formation of CB chondrules by colliding planetesimals

    DEFF Research Database (Denmark)

    Olsen, M.B.; Schiller, Martin; Krot, A.N.;

    2013-01-01

    Chondrules are igneous spherical objects preserved in chondritic meteorites and believed to have formed during transient heating events in the solar protoplanetary disk. Chondrules present in the metal-rich CB chondrites show unusual chemical and petrologic features not observed in other chondrit...

  7. The building stones of the planets

    International Nuclear Information System (INIS)

    Chondritic meteorites are considered to represent samples of nebular material that accreted to form the terrestrial planets, with the most reduced chondrites (EH and EL) believed to form nearest the sun and the most oxidized (CM and CI) farthest from the sun. This paper presents evidence indicating that the CM and CO chondrites formed beyond 2.5 AU, i.e., farther from the sun than the ordinary chondrites. It is argued that the single generation of accumulation processes recorded in the ordinary chondrites is more representative of those occurring during the formation of the terrestrial planets, and that, inside 2 AU, only one kind of planetisimal formed at each distance from the sun. The interpretation of the chondritic evidence leads to the conclusion that the planet Mercury could have formed from building blocks that were closely related to the enstatite chondrites

  8. Early chemical history of the solar system

    Science.gov (United States)

    Grossman, L.; Larimer, J. W.

    1974-01-01

    By using equilibrium thermodynamics, the sequence of condensation of mineral phases from a cooling nebula of solar composition has been calculated. The theoretical models suggest that the chemistry and mineralogy of Ca-Al-rich inclusions in C2 and C3 chondrites were established during condensation at temperatures above 1300 K. Fractionation of such inclusions is necessary to account for the refractory element depletions of ordinary and enstatite chondrites relative to the carbonaceous chondrites. The metal-silicate fractionation in ordinary chondrites took place in the nebula at a temperature below 1000 K and at .00001 atm total pressure. The volatile element depletion of C2 and C3 chondrites relative to C1 chondrites took place during chondrule formation: the most volatile elements are depleted in ordinary chondrites because they accreted before these elements were totally condensed.

  9. CAIs in Semarkona (LL3.0)

    Science.gov (United States)

    Mishra, R. K.; Simon, J. I.; Ross, D. K.; Marhas, K. K.

    2016-01-01

    Calcium, Aluminum-rich inclusions (CAIs) are the first forming solids of the Solar system. Their observed abundance, mean size, and mineralogy vary quite significantly between different groups of chondrites. These differences may reflect the dynamics and distinct cosmochemical conditions present in the region(s) of the protoplanetary disk from which each type likely accreted. Only about 11 such objects have been found in L and LL type while another 57 have been found in H type ordinary chondrites, compared to thousands in carbonaceous chondrites. At issue is whether the rare CAIs contained in ordinary chondrites truly reflect a distinct population from the inclusions commonly found in other chondrite types. Semarkona (LL3.00) (fall, 691 g) is the most pristine chondrite available in our meteorite collection. Here we report petrography and mineralogy of 3 CAIs from Semarkona

  10. Mercury's Protoplanetary Mass

    OpenAIRE

    Herndon, J. Marvin

    2004-01-01

    Major element fractionation among chondrites has been discussed for decades as ratios relative to Si or Mg. Recently, by expressing ratios relative to Fe, I discovered a new relationship admitting the possibility that ordinary chondrite meteorites are derived from two components, a relatively oxidized and undifferentiated, primitive component and a somewhat differentiated, planetary component, with oxidation state like the highly reduced enstatite chondrites, which I suggested was identical t...

  11. Trace fossils of Marnoso-Arenacea Formation (Miocene), northern Italy: preliminary data

    Energy Technology Data Exchange (ETDEWEB)

    McBride, E.F.; Picard, M.D.

    1988-02-01

    Many horizons in the Marnoso-arenacea Formation contain rare to abundant trace fossils at numerous localities. Slope, fan, and basin-plain deposits have trace fossils dominated by the Nereites ichnofacies but include taxa from the Zoophycos ichnofacies plus Ohphiomorpha and Thalassinoides. Slope deposits contain Chondrites, Cosmorhaphe, Desmograpton, Helminthoida, Neonereites, Paleodictyon, Pelecypodichnus, Planolites, Punctorhaphe, and Scolicia; fan-channel deposits contain Chondrites and Planolites; fan-lobe deposits contain Chondrites, Ophiomorpha, Thalassinoides, Scolicia, and Zoophycos; and basin-plain deposits contain Chondrites, Helminthoida, Planolites, and Zoophycos. The distribution of hypichnial taxa may be in part the result of selective preservation (i.e., dependent on the depth of erosion by turbidity currents).

  12. Chemical analysis of organic molecules in carbonaceous meteorites

    NARCIS (Netherlands)

    Torrao Pinto Martins, Zita Carla

    2007-01-01

    Meteorites are extraterrestrial objects that survive the passage through the Earth’s atmosphere and impact the Earth's surface. They can be divided into several classes, the carbonaceous chondrites being one of them. Carbonaceous chondrites are the oldest and best preserved meteorites and contain a

  13. Electron microprobe study of a 'mysterite'-bearing inclusion from the Krymka LL-chrondrite

    Science.gov (United States)

    Grossman, L.; Allen, J. M.; Macpherson, G. J.

    1980-01-01

    The black inclusion from the Krymka LL3 chondrite previously found to contain 'mysterite' by Lewis et al. (1979) belongs to a hitherto unknown class of carbonaceous chondrites. Its olivine and pyroxene compositions, Fo 97-99 and En 96, respectively, are characteristic of carbonaceous chondrites and its plagioclase composition. An 100 is characteristic of C3's. It contains a peculiar group of Co-, Cr-rich metal grains whose compositions are similar, but not identical, to those in C2 chondrites. Its weight ratios of total Fe/SiO2 and SiO2/MgO are 0.74 and 1.43, respectively, and its atomic ratio of Si/Al is 10.7, exactly the same as in carbonaceous chondrites. Its bulk chemical composition is very close to that of the Murchison C2 chondrite. The association of mysterite with a special type of carbonaceous chondrite material suggests that mysterite formed by low-temperature condensation in a different region of the nebula from other carbonaceous chondrites.

  14. Thulium anomalies and rare earth element patterns in meteorites and Earth: Nebular fractionation and the nugget effect

    CERN Document Server

    Dauphas, N

    2015-01-01

    This study reports the bulk rare earth element (REEs, La-Lu) compositions of 41 chondrites, including 32 falls and 9 finds from carbonaceous (CI, CM, CO and CV), enstatite (EH and EL) and ordinary (H, L and LL) groups, as well as 2 enstatite achondrites (aubrite). The CI-chondrite-normalized REE patterns and Eu anomalies in ordinary and enstatite chondrites show more scatter in more metamorphosed than in unequilibrated chondrites. This is due to parent-body redistribution of the REEs in various carrier phases during metamorphism. The dispersion in REE patterns of equilibrated ordinary chondrites is explained by the nugget effect associated with concentration of REEs in minor phosphate grains. Terrestrial rocks and samples from ordinary and enstatite chondrites display negative Tm anomalies of ~-4.5 % relative to ca chondrites. In contrast, CM, CO and CV (except Allende) show no significant Tm anomalies. Allende CV chondrite shows large excess Tm (~+10 %). These anomalies are similar to those found in group II...

  15. Mineralogical Characterization of Baptistina Asteroid Family: Implications for K/T Impactor Source

    CERN Document Server

    Reddy, Vishnu; Lazzaro, Daniela; Michtchenko, Tatiana A; Gaffey, Michael J; Kelley, Michael S; Diniz, Thais Mothé; Candal, Alvaro Alvarez; Moskovitz, Nicholas A; Cloutis, Edward A; Ryan, Erin L; 10.1016/j.icarus.2011.08.027

    2011-01-01

    Bottke et al. (2007) linked the catastrophic formation of Baptistina Asteroid Family (BAF) to the K/T impact event. This linkage was based on dynamical and compositional evidence, which suggested the impactor had a composition similar to CM2 carbonaceous chondrites. However, our recent study (Reddy et al. 2009) suggests that the composition of (298) Baptistina is similar to LL-type ordinary chondrites rather than CM2 carbonaceous chondrites. This rules out any possibility of it being related to the source of the K/T impactor, if the impactor was of CM-type composition. Mineralogical study of asteroids in the vicinity of BAF has revealed a plethora of compositional types suggesting a complex formation and evolution environment. A detailed compositional analysis of 16 asteroids suggests several distinct surface assemblages including ordinary chondrites (Gaffey SIV subtype), primitive achondrites (Gaffey SIII subtype), basaltic achondrites (Gaffey SVII subtype and V-type), and a carbonaceous chondrite. Based on ...

  16. Coordinates Analyses of Hydrated Interplanetary Dust Particles: Samples of Primitive Solar System Bodies

    Science.gov (United States)

    Keller, L. P.; Snead, C.; McKeegan, K. D.

    2016-01-01

    Interplanetary dust particles (IDPs) collected in the stratosphere fall into two major groups: an anhydrous group termed the "chondritic-porous (CP) IDPs and a hydrated group, the "chondritic-smooth (CS) IDPs, although rare IDPs with mineralogies intermediate between these two groups are known [1]. The CP-IDPs are widely believed to be derived from cometary sources [e.g. 2]. The hydrated CS-IDPs show mineralogical similarities to heavily aqueously altered carbonaceous chondrites (e.g. CI chondrites), but only a few have been directly linked to carbonaceous meteorite parent bodies [e.g. 3, 4]. Most CS-IDPs show distinct chemical [5] and oxygen isotopic composition differences [6-8] from primitive carbonaceous chondrites. Here, we report on our coordinated analyses of a suite of carbon-rich CS-IDPs focusing on their bulk compositions, mineralogy, mineral chemistry, and isotopic compositions.

  17. Transport of solids in protoplanetary disks: Comparing meteorites and astrophysical models

    CERN Document Server

    Jacquet, Emmanuel

    2014-01-01

    We review models of chondrite component transport in the gaseous protoplanetary disk. Refractory inclusions were likely transported by turbulent diffusion and possible early disk expansion, and required low turbulence for their subsequent preservation in the disk, possibly in a dead zone. Chondrules were produced locally but did not necessarily accrete shortly after formation. Water may have been enhanced in the inner disk because of inward drift of solids from further out, but likely not by more than a factor of a few. Incomplete condensation in chondrites may be due to slow reaction kinetics during temperature decrease. While carbonaceous chondrite compositions might be reproduced in a ``two-component'' picture (Anders 1964), such components would not correspond to simple petrographic constituents, although part of the refractory element fractionations in chondrites may be due to the inward drift of refractory inclusions. Overall, considerations of chondrite component transport alone favor an earlier format...

  18. Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

    Science.gov (United States)

    Srinivasan, P.; Agee, C. B.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.

    2016-01-01

    CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approx.576-867 C. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Metallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120deg triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3+, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

  19. Reply to comment on "Chondritic-like xenon trapped in Archean rocks: A possible signature of the ancient atmosphere" by Pujol, M., Marty, B., Burgess, R., Earth and Planetary Science Letters 308 (2011) 298-306 by Pepin, R.O.

    Science.gov (United States)

    Pujol, Magali; Marty, Bernard; Burgess, Ray

    2013-06-01

    We thank Pepin (2013) for pointing-out an interesting issue concerning the interpretation of the xenon isotope data that we recently published (Pujol et al., 2011). We have analyzed noble gases trapped in quartz fluid inclusions from the 3.5 Ga-old Dresser Formation (Western Australia). Ar-Ar dating of the quartz yielded an age of 3.0±0.2 Ga, slightly younger than the formation age, but still clearly within the Archean eon. This study focused on the Xe isotopic signature of these fluids: the non-fissiogenic isotopes of xenon appear isotopically fractionated, with about 1% amu-1 enrichment in light isotopes. This isotopic mass fractionation was interpreted to represent an intermediate stage of atmosphere evolution.

  20. A nucleosynthetic origin for the Earth’s anomalous 142Nd composition

    Science.gov (United States)

    Burkhardt, C.; Borg, L. E.; Brennecka, G. A.; Shollenberger, Q. R.; Dauphas, N.; Kleine, T.

    2016-09-01

    A long-standing paradigm assumes that the chemical and isotopic compositions of many elements in the bulk silicate Earth are the same as in chondrites. However, the accessible Earth has a greater 142Nd/144Nd ratio than do chondrites. Because 142Nd is the decay product of the now-extinct 146Sm (which has a half-life of 103 million years), this 142Nd difference seems to require a higher-than-chondritic Sm/Nd ratio for the accessible Earth. This must have been acquired during global silicate differentiation within the first 30 million years of Solar System formation and implies the formation of a complementary 142Nd-depleted reservoir that either is hidden in the deep Earth, or lost to space by impact erosion. Whether this complementary reservoir existed, and whether or not it has been lost from Earth, is a matter of debate, and has implications for determining the bulk composition of Earth, its heat content and structure, as well as for constraining the modes and timescales of its geodynamical evolution. Here we show that, compared with chondrites, Earth’s precursor bodies were enriched in neodymium that was produced by the slow neutron capture process (s-process) of nucleosynthesis. This s-process excess leads to higher 142Nd/144Nd ratios; after correction for this effect, the 142Nd/144Nd ratios of chondrites and the accessible Earth are indistinguishable within five parts per million. The 142Nd offset between the accessible silicate Earth and chondrites therefore reflects a higher proportion of s-process neodymium in the Earth, and not early differentiation processes. As such, our results obviate the need for hidden-reservoir or super-chondritic Earth models and imply a chondritic Sm/Nd ratio for the bulk Earth. Although chondrites formed at greater heliocentric distances and contain a different mix of presolar components than Earth, they nevertheless are suitable proxies for Earth’s bulk chemical composition.

  1. A nucleosynthetic origin for the Earth's anomalous (142)Nd composition.

    Science.gov (United States)

    Burkhardt, C; Borg, L E; Brennecka, G A; Shollenberger, Q R; Dauphas, N; Kleine, T

    2016-01-01

    A long-standing paradigm assumes that the chemical and isotopic compositions of many elements in the bulk silicate Earth are the same as in chondrites. However, the accessible Earth has a greater (142)Nd/(144)Nd ratio than do chondrites. Because (142)Nd is the decay product of the now-extinct (146)Sm (which has a half-life of 103 million years), this (142)Nd difference seems to require a higher-than-chondritic Sm/Nd ratio for the accessible Earth. This must have been acquired during global silicate differentiation within the first 30 million years of Solar System formation and implies the formation of a complementary (142)Nd-depleted reservoir that either is hidden in the deep Earth, or lost to space by impact erosion. Whether this complementary reservoir existed, and whether or not it has been lost from Earth, is a matter of debate, and has implications for determining the bulk composition of Earth, its heat content and structure, as well as for constraining the modes and timescales of its geodynamical evolution. Here we show that, compared with chondrites, Earth's precursor bodies were enriched in neodymium that was produced by the slow neutron capture process (s-process) of nucleosynthesis. This s-process excess leads to higher (142)Nd/(144)Nd ratios; after correction for this effect, the (142)Nd/(144)Nd ratios of chondrites and the accessible Earth are indistinguishable within five parts per million. The (142)Nd offset between the accessible silicate Earth and chondrites therefore reflects a higher proportion of s-process neodymium in the Earth, and not early differentiation processes. As such, our results obviate the need for hidden-reservoir or super-chondritic Earth models and imply a chondritic Sm/Nd ratio for the bulk Earth. Although chondrites formed at greater heliocentric distances and contain a different mix of presolar components than Earth, they nevertheless are suitable proxies for Earth's bulk chemical composition.

  2. The nature of Earth's building blocks as revealed by calcium isotopes

    Science.gov (United States)

    Valdes, Maria C.; Moreira, Manuel; Foriel, Julien; Moynier, Frédéric

    2014-05-01

    Calcium is the fifth most abundant element in the Earth and in chondrites and is a pure lithophile element which does not partition into planetary cores. Therefore, the calcium isotopic composition of the mantle represents the bulk Earth and calcium isotopes have the potential to reveal genetic links between Earth and meteorites. However, whether calcium exhibits significant mass-dependent variations among Earth and the various chondrite groups, and the magnitude of these variations, is still contentious. Here we have developed a new method to analyze calcium isotope ratios with high precision using multiple-collector inductively-coupled-plasma mass-spectrometry. The method has been applied to a range of terrestrial and meteoritic samples. We find that the Earth, the Moon, and the aubrite parent body are indistinguishable from enstatite, ordinary, and CO chondritic meteorites. Therefore, enstatite chondrites cannot be excluded as components of Earth's building blocks based on calcium isotopes, as has been proposed previously. In contrast, CI, CV, CM and CR carbonaceous chondrites are largely enriched in lighter calcium isotopes compared to Earth, and, overall, exhibit a wide range in calcium isotopic composition. Calcium is the only major element, along with oxygen, for which isotopic variations are observed among carbonaceous chondrite groups. These calcium isotope variations cannot be attributed to volatility effects, and it is difficult to ascribe them to the abundance of isotopically light refractory inclusions. The calcium isotope data presented in this study suggest that both ordinary and enstatite chondrites are representative of the bulk of the refractory materials that formed Earth. On the basis of calcium isotopes, carbonaceous chondrites (with the exception of CO) are not representative of the fraction of condensable material that accreted to form the terrestrial planets and can be excluded as unique contenders for the building blocks of Earth; however

  3. Organic and volatile elements in the solar system

    Directory of Open Access Journals (Sweden)

    Remusat L.

    2012-01-01

    Full Text Available Chondrites and comets have accreted primitive materials from the early solar system. Those materials include organics, water and other volatile components. The most primitive chondrites and comets have undergone few modifications on their respective parent bodies and can deliver to laboratories components that were present at the origin of the protosolar nebula. Here I present a review of the organic material and volatile components that have been studied in the most primitive chondrites, and the last data from the stardust mission about the cometary record. This paper focuses on materials that can be studied in laboratories, by mass spectrometry, ion probes or organic chemistry techniques.

  4. Carbynes - Carriers of primordial noble gases in meteorites

    Science.gov (United States)

    Whittaker, A. G.; Watts, E. J.; Lewis, R. S.; Anders, E.

    1980-01-01

    Five carbynes (triply bonded allotropes of carbon) have been found by electron diffraction in the Allende and Murchison carbonaceous chondrites: carbon VI, VIII, X, XI, and (tentatively) XII. From the isotopic composition of the associated noble-gas components, it appears that the carbynes in Allende (C3V chondrite) are local condensates from the solar nebula, whereas at least two carbynes in Murchison (C2 chondrite) are of exotic, presolar origin. They may be dust grains that condensed in stellar envelopes and trapped isotropically anomalous matter from stellar nucleosynthesis.

  5. Noble gases in Tagish Lake

    OpenAIRE

    Grady, Monica; Verchovsky, Sasha; Franchi, Ian; Wright, Ian; Pillinger, Colin

    2001-01-01

    From the introduction: Tagish Lake has been classified as a CI2 chondrite [1] with an interstellar grain abundance enhanced over that of CI1 and CM2 chondrites [2]. Noble gases have been used as markers for the presence of exotic, presolar grains in chondritic meteorites: Xe-HL (nanodiamonds) and Xe-s/Ne-E (SiC). We have measured 4He, Ne, Ar and Xe in whole-rock Tagish Lake, and an orthophosphoric acid-resistant residue, in an effort to define more precisely the...

  6. The Nature and Origin of Aromatic Organic Matter in the Tagish Lake Meteorite

    Science.gov (United States)

    Clemett, S. J.; Keller, L. P.; Nakamura, K.; McKay, D. S.

    2004-01-01

    The Tagish Lake meteorite is an unusual carbonaceous chondrite that does not fit well within existing chondrite taxonomy. Bulk analyses suggest approx. 5 wt.% C of which approx. 1 wt.% is in the form of organic matter and the remainder is present as inorganic carbonate. The exact nature and form of this organic component is, as is the case with the other ordinary and carbonaceous chondrites, still poorly understood. Yet its significance has far reaching implications, from contributing to the abiotic evolution of the early Earth and Mars, to providing geothermal constraints in the evolution of the Solar nebula.

  7. Micrometeorite flux on Earth during the last ~50,000 years

    Digital Repository Service at National Institute of Oceanography (India)

    ShyamPrasad, M.; Rudraswami, N.G.; Panda, D.K.

    chondritic parent body; a single spherule (0.2% of the population) suggests an achondritic parent body. Unbiased collections spanning large areas temporally and spatially enlarge the inventory of the Earth-crossing meteoroid complex and provide valuable...

  8. Antarctic Meteorite Newsletter, Volume 31, No. 1

    Science.gov (United States)

    Satterwhite, Cecilia (Editor); Righter, Kevin (Editor)

    2008-01-01

    This newsletter reports 418 new meteorites from the 2004 and 2006 ANSMET seasons from the Cumulus Hills (CMS), LaPaz Ice Field (LAP), Graves Nunataks (GRA), Grosvenor Mountains (GRO), Larkman Nunatak (LAR), MacAlpine Hills (MAC), Miller Range (MIL), Roberts Massif (RBT), and Scott Glacier (SCO). These new samples include one iron, 1 eucrite, 1 mesosiderite, 6 CK chondrites (2 with pairing), 2 CV3 chondrites, 1 CM1, 7 CM2 (4 with pairing), 3 CR2 (2 with pairing), and one each of a type 3 L and H chondrites. The CK6 chondrites (LAR 06869, 06872, 06873) are unusual in that they have no discernable chondrules, extremely fine-grained texture, and are full of veins. This newsletter represents a break from recent newsletters in which we have announced many unusual and popular samples, including new lunar and martian meteorites, an unusual achondrite (GRA 06128 and 06129 the topic of a special session at this years LPSC).

  9. Bacterial morphologies in carbonaceous meteorites and comet dust

    CERN Document Server

    Wickramasinghe, N Chandra; Gibson, Carl H; Wallis, Jamie; Al-Mufti, Shirwan; Miyake, Nori

    2010-01-01

    Three decades ago the first convincing evidence of microbial fossils in carbonaceous chondrites was discovered and reported by Hans Dieter Pflug and his collaborators. In addition to morphology, other data, notably laser mass spectroscopy, confirmed the identification of such structures as putative bacterial fossils. Balloon-borne cryosampling of the stratosphere enables recovery of fragile cometary dust aggregates with their structure and carbonaceous matter largely intact. Scanning electron microscope studies of texture and morphology of particles in the Cardiff collection, together with Energy Dispersive X-ray identifications, show two main types of putative bio-fossils - firstly organic-walled hollow spheres around 10 microns across, secondly siliceous diatom skeletons similar to those found in carbonaceous chondrites and terrestrial sedimentary rocks and termed "acritarchs". Since carbonaceous chondrites (particularly Type 1 chondrites) are thought to be extinct comets the data reviewed in this article p...

  10. Chelyabinsk meteorite explains unusual spectral properties of Baptistina Asteroid Family

    CERN Document Server

    Reddy, Vishnu; Bottke, William; Cloutis, Ed; Izawa, Matt; O'Brien, Dave; Mann, Paul; Cuddy, Matt; Corre, Lucille Le; Gaffey, Michael; Fujihara, Gary

    2014-01-01

    We investigated the spectral and compositional properties of Chelyabinsk meteorite to identify its possible parent body in the main asteroid belt. Our analysis shows that the meteorite contains two spectrally distinct but compositionally indistinguishable components of LL5 chondrite and shock blackened/impact melt material. Our X-ray diffraction analysis confirms that the two lithologies of the Chelyabinsk meteorite are extremely similar in modal mineralogy. The meteorite is compositionally similar to LL chondrite and its most probable parent asteroid in the main belt is a member of the Flora family. Intimate mixture of LL5 chondrite and shock blackened/impact melt material from Chelyabinsk provides a spectral match with (8) Flora, the largest asteroid in the Flora family. The Baptistina family and Flora family overlap each other in dynamical space. Mineralogical analysis of (298) Baptistina and 9 small family members shows that their surface compositions are similar to LL chondrites, although their absorptio...

  11. Almahata Sitta News: Well-Known Varieties and New Species in the Zoo

    Science.gov (United States)

    Bischoff, A.; Ebert, S.; Patzek, M.; Horstmann, M.; Pack, A.; Decker, S.

    2016-08-01

    Mineralogical characteristics of 18 new samples from the Almahata Sitta strewn field are presented. Among the samples are 5 E chondrites, 12 samples of ureilitic origin (including a new trachyandesite), and an enstatite- and metal-rich achondrite.

  12. The Meteoritical Bulletin, No. 101

    Science.gov (United States)

    Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Herd, Christopher D. K.; Agee, Carl B.

    2015-09-01

    Meteoritical Bulletin 101 contains 2639 meteorites accepted by the Nomenclature Committee in 2012, including 1 fall (Battle Mountain), with 2308 ordinary chondrites, 156 carbonaceous chondrites, 63 HED achondrites, 17 relict meteorites, 16 Rumuruti chondrites, 15 enstatite chondrites, 15 ureilites, 10 iron meteorites, 9 lunar meteorites, 9 primitive achondrites, 8 ungrouped achondrites, 7 mesosiderites, 4 Martian meteorites, and 2 Pallasites, and with 1812 from Antarctica, 437 from Asia, 301 from Africa, 43 from South America, 21 from Europe (including Russia), 21 from North America, 3 from Oceania, and 1 from unknown. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at lpi.usra.edu/meteor/">http://www.lpi.usra.edu/meteor/.

  13. The Meteoritical Bulletin, No. 102

    Science.gov (United States)

    Ruzicka, Alex; Grossman, Jeffrey; Bouvier, Audrey; Herd, Christopher D. K.; Agee, Carl B.

    2015-09-01

    Meteoritical Bulletin 102 contains 3141 meteorites including 12 falls (Boumdeid (2003), Boumdeid (2011), Braunschweig, Chelyabinsk, Dongyang, Draveil, Heyetang, Indian Butte, Katol, Ladkee, Ouadangou, Xining), with 2611 ordinary chondrites, 264 HED achondrites, 124 carbonaceous chondrites, 30 ureilites, 20 Martian meteorites, 16 primitive achondrites, 16 Rumuruti chondrites, 15 mesosiderites, 12 iron meteorites, 10 lunar meteorites, 9 enstatite chondrites, 4 enstatite achondrites, 4 Pallasites, 4 ungrouped achondrites, and 2 angrites, and with 1708 from Antarctica, 956 from Africa, 294 from South America, 126 from Asia, 47 from North America, 6 from Europe (including Russia), and 4 from Oceania. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at lpi.usra.edu/meteor/">http://www.lpi.usra.edu/meteor/.

  14. Trace element analyses of spheres from the melt zone of the Greenland ice cap using synchrotron x ray fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Chevallier, P.; Jehanno, C.; Maurette, M.; Sutton, S.R.; Wang, J.

    1987-01-01

    Synchrotron x-ray fluorescence spectra of unpolished iron and chondritic spheres extracted from sediments collected on the melt zone of the Greenland ice cap allow the analysis of Ni, Cu, Zn, Ga, Ge, Pb, and Se with minimum detection limits on the order of several parts per million. All detected elements are depleted relative to chondritic abundance with the exception of Pb, which shows enrichments up to factor of 500. An apparent anticorrelation between the Ni-content and trace element concentration was observed in both types of spherules. The fractionation patterns of the iron and chondritic spheres are not complmementary and consequently the two iron spheres examined in this study are unlikely to result from the ejection of globules of Fe/Ni from parent chondritic micrometeoroids. 8 figs., 2 tabs.

  15. The IIE Iron Meteorite Family Tree: A Study of the Petrography and Oxygen Isotopes of the Non-Magmatic Group

    Science.gov (United States)

    McDermott, K. H.; Greenwood, R. C.; Franchi, I. A.; Anand, M.; Scott, E. R. D.

    2012-03-01

    Petrographic and isotopic analysis have shown three distinct relationships exist between the ordinary chondrites and IIE silicates, expanding our concept of the parent body and the thermal history it encountered.

  16. Is Asteroid 433 Eros Compositionally Homogeneous? New Analyses of NEAR-Shoemaker X-Ray Spectrometer Data

    Science.gov (United States)

    Nittler, L. R.; Trombka, J. I.

    2001-01-01

    We present new analysis techniques for NEAR-Shomaker X-ray spectrometer data to infer the compositional heterogeneity of asteroid 433 Eros. Preliminary results indicate a largely chondritic, homogeneous composition. Additional information is contained in the original extended abstract.

  17. Low Pressure Evidence of High Pressure Shock: Thermal Histories and Annealing in Shocked Meteorites

    Science.gov (United States)

    Sharp, T. G.; Hu, J.

    2016-08-01

    In this study we look at the mineralogy associated with shock veins in several highly shocked L chondrites to better understand shock conditions and the importance of thermal history in creating and destroying high-pressure minerals.

  18. A Stranger in the Midst: Searching for Relict Grains from Rare Meteorite Types in Mid-Ordovician Limestone Strata

    Science.gov (United States)

    Martin, E.; Schmitz, B.

    2016-08-01

    A layer of Mid-Ordovician limestone harbors exceptional amounts of L-chondritic chromite grains. The layer also contains grains from potentially rarer types of meteorites, following the discovery of the fossil meteorite Österplana 065.

  19. Generating potassium abundance variations in the Solar Nebula

    CERN Document Server

    Hubbard, Alexander

    2016-01-01

    An intriguing aspect of chondritic meteorites is that they are complementary: while their separate components have wildly varying abundances, bulk chondrites have nearly solar composition. This implies that the nearly-solar reservoirs in which chondrites were born were in turn assembled from sub-reservoirs of differing compositions that birthed the different components. We focus on explaining the potassium abundance variations between chondrules even within a single chondrite, while maintaining the observed CI $^{41}$K to $^{39}$K ratios. This requires physically separating potassium and chondrules while the temperature is high enough for K to be in the gas phase. We examine several mechanisms which could drive the dust through gas and show that to do so locally would have required long (sub-orbital to many orbits) time scales; with shortest potassium depletion time scales occurring in a scenario where chondrules formed high above the midplane and settled out of the evaporated potassium. While orbital time sc...

  20. Redistribution and Evolution of Organics During Aqueous Alteration: NanoSIMS-STXM-TEM Analyses of FIB Sections from Renazzo, Murchison and Orgueil

    Science.gov (United States)

    Le Guillou, C.; Remusat, L.; Bernard, S.; Brearley, A. J.

    2011-03-01

    What is the in situ spatial distribution and environment of organic grains in carbonaceous chondrites matrices? They seem to evolve physically and chemically during aqueous alteration and show relationship with phyllosilicates and carbonates.

  1. Abundances of presolar silicon carbide grains in primitive meteorites determined by NanoSIMS

    Science.gov (United States)

    Davidson, Jemma; Busemann, Henner; Nittler, Larry R.; Alexander, Conel M. O.'D.; Orthous-Daunay, François-Régis; Franchi, Ian A.; Hoppe, Peter

    2014-08-01

    It has been suggested that the matrices of all chondrites are dominated by a common material with Ivuna-like (CI) abundances of volatiles, presolar grains and insoluble organic matter (IOM) (e.g., Alexander, 2005). However, matrix-normalized abundances of presolar silicon carbide (SiC) grains estimated from their noble gas components show significant variations in even the most primitive chondrites (Huss and Lewis, 1995; Huss et al., 2003), in contradiction to there being a common chondrite matrix material. Here we report presolar SiC abundances determined by NanoSIMS raster ion imaging of IOM extracted from primitive members of different meteorite groups. We show that presolar SiC abundance determinations are comparable between NanoSIMS instruments located at three different institutes, between residues prepared by different demineralization techniques, and between microtomed and non-microtomed samples. Our derived SiC abundances in CR chondrites are comparable to those found in the CI chondrites (∼30 ppm) and are much higher than previously determined by noble gas analyses. The revised higher CR SiC abundances are consistent with the CRs being amongst the most primitive chondrites in terms of the isotopic compositions and disordered nature of their organic matter. Similar abundances between CR1, CR2, and CR3 chondrites indicate aqueous alteration on the CR chondrite parent body has not progressively destroyed SiC grains in them. A low SiC abundance for the reduced CV3 RBT 04133 can be explained by parent body thermal metamorphism at an estimated temperature of ∼440 °C. Minor differences between primitive members of other meteorite classes, which did not experience such high temperatures, may be explained by prolonged oxidation at lower temperatures under which SiC grains formed outer layers of SiO2 that were not thermodynamically stable, leading to progressive degassing/destruction of SiC.

  2. Mineralogy and chemical compositions of Colomera (IIE) silicate inclusions

    OpenAIRE

    Hsu, W.; H. Takeda; Huss, G. R.; Wasserburg, G. J.

    1997-01-01

    Irons of groups lAB and IIE contain silicate inclusions. In IAB irons, these inclusions are basically chondritic, but in IIE they vary from chondritic to highly differentiated [1,2]. In this work, we present detailed studies of mineralogy and trace-element geochemistry of eight silicate inclusions from Colomera with the goal of better understanding early planetary differentiation and possible genetic relationships between iron and stony meteorites.

  3. PALEONTOLOGY

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20111843Ma Huizhen(Guizhou Academy of Geologic Survey,Guiyang550005,China);Zhang LijunChondrites from the Devonian Neritic Cruziana Ichnofacies as Indicators of Palaeo-oxygenation Facies in South China (Advances in Earth Science,ISSN1001-8166,CN62-1091/P,25(9),2010,p.966-973,3illus.,1table,32refs.)Key words:ichnofossils,South ChinaChondrites widely occurred in the Devonian neritic Cruziana ichnofacies from the

  4. EVIDENCE FOR COMET STORMS IN METEORITE AGES

    Energy Technology Data Exchange (ETDEWEB)

    Perlmutter, S.; Muller, R.A.

    1987-10-01

    Clustering of cosmic-ray exposure ages of H chondritic meteorites occurs at 7 {+-} 3 and 30 {+-} 6 Myr ago. There is independent evidence that comet storms have occurred at the same times, based on the fossil record of family and genus extinctions, impact craters and glass, and geomagnetic reversals. We suggest that H chondrites were formed by the impact of shower comets on asteroids. The duration of the most recent comet shower was {le} 4 Myr, in agreement with storm theory.

  5. Geochemical arguments for an Earth-like Moon-forming impactor

    OpenAIRE

    Dauphas, Nicolas; Burkhardt, Christoph; Warren, Paul H.; Fang-Zhen, Teng

    2014-01-01

    Geochemical evidence suggests that the material accreted by the Earth did not change in nature during Earth's accretion, presumably because the inner protoplanetary disc had uniform isotopic composition similar to enstatite chondrites, aubrites and ungrouped achondrite NWA 5363/5400. Enstatite meteorites and the Earth were derived from the same nebular reservoir but diverged in their chemical evolutions, so no chondrite sample in meteorite collections is representative of the Earth's building...

  6. Iridium anomaly in the cretaceous-paleogene boundary at Højerup (Stevns Klint, Denmark) and Woodside Creek (New Zealand): The question of an enormous proportion of extraterrestrial component

    OpenAIRE

    Premović Pavle I.; Ilić Budimir S.; Đorđević Miloš G.

    2012-01-01

    The Cretaceous-Paleogene boundary clays at Højerup and Woodside Creek show anomalous enrichments of iridium compared with the marine sedimentary rocks. For the average iridium content of 465 ppb in CI chondrite the estimate of the carbonaceous chondritic proportions in the decarbonated iridium-rich boundary layers, based on the integrated iridium fluencies, is about 26% at Højerup and 65% at Woodside Creek. These proportions are most likely too high due to a significant Ir influx from t...

  7. The variation of Zn content in spinel group minerals and daubreelites of primitive achondrites

    OpenAIRE

    Chikami,Jun/Miyamoto,Masamichi/Takeda,Hiroshi

    1999-01-01

    We have studied the Zn content of spinel group mineral and daubreelite in primitive achondrites in order to clarify how the content of Zn, a moderately volatile element, reflects their formation process. Primitive achondrites have achondritic texture and chondrite-related chemistry and mineralogy. Because of these characteristics, primitive achondrites are thought to represent the transition from chondrites to achondrites. We have compared the Zn content in spinel group minerals of primitive ...

  8. Lunar and Planetary Science XXXV: Meteorites

    Science.gov (United States)

    2004-01-01

    The session "Meteorites" included the following reports:Description of a New Stony Meteorite Find from Bulloch County, Georgia; Meteorite Ablation Derived from Cosmic Ray Track Data Dhofar 732: A Mg-rich Orthopyroxenitic Achondrite Halogens, Carbon and Sulfur in the Tagish Lake Meteorite: Implications for Classification and Terrestrial Alteration; Electromagnetic Scrape of Meteorites and Probably Columbia Tiles; Pre-Atmospheric Sizes and Orbits of Several Chondrites; Research of Shock-Thermal History of the Enstatite Chondrites by Track, Thermoluminescence and Neutron-Activation (NAA) Methods; Radiation and Shock-thermal History of the Kaidun CR2 Chondrite Glass Inclusions; On the Problem of Search for Super-Heavy Element Traces in the Meteorites: Probability of Their Discovery by Three-Prong Tracks due to Nuclear Spontaneous Fission Trace Element Abundances in Separated Phases of Pesyanoe, Enstatite Achondrite; Evaluation of Cooling Rate Calculated by Diffusional Modification of Chemical Zoning: Different Initial Profiles for Diffusion Calculation; Mineralogical Features and REE Distribution in Ortho- and Clinopyroxenes of the HaH 317 Enstatite Chondrite Dhofar 311, 730 and 731: New Lunar Meteorites from Oman; The Deuterium Content of Individual Murchison Amino Acids; Clues to the Formation of PV1, an Enigmatic Carbon-rich Chondritic Clast from the Plainview H-Chondrite Regolith Breccia ;Numerical Simulations of the Production of Extinct Radionuclides and ProtoCAIs by Magnetic Flaring.

  9. The Ar-Ar age and petrology of Miller Range 05029: Evidence for a large impact in the very early solar system

    Science.gov (United States)

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

    2010-12-01

    Miller Range (MIL) 05029 is a slowly cooled melt rock with metal/sulfide depletion and an Ar-Ar age of 4517 ± 11 Ma. Oxygen isotopes and mineral composition indicate that it is an L chondrite impact melt, and a well-equilibrated igneous rock texture with a lack of clasts favors a melt pool over a melt dike as its probable depositional setting. A metallographic cooling rate of approximately 14 °C Ma-1 indicates that the impact occurred at least approximately 20 Ma before the Ar-Ar closure age of 4517 Ma, possibly even shortly after accretion of its parent body. A metal grain with a Widmanstätten-like pattern further substantiates slow cooling. The formation age of MIL 05029 is at least as old as the Ar-Ar age of unshocked L and H chondrites, indicating that endogenous metamorphism on the parent asteroid was still ongoing at the time of impact. Its metallographic cooling rate of approximately 14 °C Ma-1 is similar to that typical for L6 chondrites, suggesting a collisional event on the L chondrite asteroid that produced impact melt at a minimum depth of 5-12 km. The inferred minimum crater diameter of 25-60 km may have shattered the 100-200 km diameter L chondrite asteroid. Therefore, MIL 05029 could record the timing and petrogenetic setting for the observed lack of correlation of cooling rates with metamorphic grades in many L chondrites.

  10. Compositional Homogeneity of CM Parent Bodies

    Science.gov (United States)

    Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Cloutis, E. A.; DeMeo, F. E.; Dumas, C.; Hiroi, T.

    2016-09-01

    CM chondrites are the most common type of hydrated meteorites, making up ˜1.5% of all falls. Whereas most CM chondrites experienced only low-temperature (˜0°C–120°C) aqueous alteration, the existence of a small fraction of CM chondrites that suffered both hydration and heating complicates our understanding of the early thermal evolution of the CM parent body(ies). Here, we provide new constraints on the collisional and thermal history of CM-like bodies from a comparison between newly acquired spectral measurements of main-belt Ch/Cgh-type asteroids (70 objects) and existing laboratory spectral measurements of CM chondrites. It first appears that the spectral variation observed among CM-like bodies is essentially due to variations in the average regolith grain size. Second, the spectral properties of the vast majority (unheated) of CM chondrites resemble both the surfaces and the interiors of CM-like bodies, implying a “low” temperature (origin is the likely explanation for the existence of heated CM chondrites. Finally, similarly to S-type asteroids and (2) Pallas, the surfaces of large (D > 100 km)—supposedly primordial—Ch/Cgh-type main-belt asteroids likely expose the interiors of the primordial CM parent bodies, a possible consequence of impacts by small asteroids (D solar system.

  11. Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets

    CERN Document Server

    Schaefer, L

    2009-01-01

    We used chemical equilibrium and chemical kinetic calculations to model chemistry of the volatiles released by heating different types of carbonaceous, ordinary and enstatite chondritic material as a function of temperature and pressure. Our results predict the composition of atmospheres formed by outgassing during accretion of the Earth and other terrestrial planets. Outgassing of CI and CM carbonaceous chondritic material produces H2O-rich (steam) atmospheres in agreement with the results of impact experiments. However, outgassing of other types of chondritic material produces atmospheres dominated by other gases. Outgassing of ordinary (H, L, LL) and high iron enstatite (EH) chondritic material yields H2-rich atmospheres with CO and H2O being the second and third most abundant gases. Outgassing of low iron enstatite (EL) chondritic material gives a CO-rich atmosphere with H2, CO2, and H2O being the next most abundant gases. Outgassing of CV carbonaceous chondritic material gives a CO2-rich atmosphere with ...

  12. Compositional Homogeneity of CM Parent Bodies

    Science.gov (United States)

    Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Cloutis, E. A.; DeMeo, F. E.; Dumas, C.; Hiroi, T.

    2016-09-01

    CM chondrites are the most common type of hydrated meteorites, making up ˜1.5% of all falls. Whereas most CM chondrites experienced only low-temperature (˜0°C–120°C) aqueous alteration, the existence of a small fraction of CM chondrites that suffered both hydration and heating complicates our understanding of the early thermal evolution of the CM parent body(ies). Here, we provide new constraints on the collisional and thermal history of CM-like bodies from a comparison between newly acquired spectral measurements of main-belt Ch/Cgh-type asteroids (70 objects) and existing laboratory spectral measurements of CM chondrites. It first appears that the spectral variation observed among CM-like bodies is essentially due to variations in the average regolith grain size. Second, the spectral properties of the vast majority (unheated) of CM chondrites resemble both the surfaces and the interiors of CM-like bodies, implying a “low” temperature (body(ies). It follows that an impact origin is the likely explanation for the existence of heated CM chondrites. Finally, similarly to S-type asteroids and (2) Pallas, the surfaces of large (D > 100 km)—supposedly primordial—Ch/Cgh-type main-belt asteroids likely expose the interiors of the primordial CM parent bodies, a possible consequence of impacts by small asteroids (D < 10 km) in the early solar system.

  13. Ru isotope heterogeneity in the solar protoplanetary disk

    Science.gov (United States)

    Fischer-Gödde, Mario; Burkhardt, Christoph; Kruijer, Thomas S.; Kleine, Thorsten

    2015-11-01

    Nucleosynthetic isotope anomalies in bulk chondrites and differentiated meteorites reflect variable proportions of isotopically diverse presolar components in bulk planetary bodies, but the origin of these heterogeneities is not well understood. Here, the Ru isotope composition of a comprehensive suite of iron meteorites and bulk samples of ordinary, enstatite and carbonaceous chondrites, as well as acid leachates and an insoluble residue of the Allende chondrite are examined using newly developed multi-collector inductively coupled plasma mass spectrometry techniques. Except for IAB iron meteorites and enstatite chondrites, all investigated meteorites show well-resolved Ru isotope anomalies. Of these, within-group Ru isotopic variations observed for samples from a given chemical group of iron meteorites reflect secondary neutron capture induced Ru isotope shifts during prolonged cosmic ray-exposure. After correction of these cosmogenic effects using Pt isotopes as a neutron-dose monitor, the remaining Ru isotope anomalies are nucleosynthetic in nature and are consistent with a deficit in s-process Ru in iron meteorite parent bodies. Similarly, Ru isotope anomalies in bulk ordinary and carbonaceous chondrites also reflect a deficiency in s-process Ru. The sequential dissolution of Allende reveals the presence of an HF-soluble s-process carrier, which is either an unidentified presolar phase or a component that incorporated s-process Ru liberated from SiC grains during nebular or parent body processes. We show that varying proportions of the s-process carrier identified in Allende resulted in the correlated Ru isotope anomalies observed for bulk meteorites, and that all meteorites (except possibly IAB irons and enstatite chondrites) are depleted in this s-process component relative to Ru from the Earth's mantle. Bulk meteorites exhibit correlated Ru and Mo isotope anomalies, reflecting variable deficits of a common s-process component, but some iron meteorites and

  14. Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

    Science.gov (United States)

    Srinivasan, P.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.; Agee, C. B.

    2016-01-01

    CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approximately 576-867 degrees Centigrade. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Me-tallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120-degree triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3 plus, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

  15. FeO-rich silicates and Ca,Al-rich inclusions in Qingzhen andYamato 691 (EH3) meteo-rites: Evidence for migration of mass in the solar nebula

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Qingzhen and Yamato 691 (EH3) enstatite chondrites, which formed under extremely reducing conditions, are studied using the scanning electron microscope and electron probe microanalyzer. Both meteorites contain FeO-rich silicates and minor Ca, Al-rich inclusions. Most FeO-rich silicates are Ca-poor pyroxenes and occur as fragments in matrix. A few grains of FeO-rich silicates were found in chondrules, and FeO-rich olivine is rare. In Qingzhen, FeO-rich silicates commonly contain abundant dust-like Ni-poor metals, which probably formed through reduction of FeO. In contrast, only a few fragments of FeO-rich silicates in Yamato 691 enclose dust-like metals.This difference is consistent with a more reducing condition of Qingzhen than Yamato 691. Ca, Al-rich inclusions have similar modal compositions and mineral chemistry as their counterparts in carbonaceous chondrites. We suggest that (1)the FeO-rich silicates probably formed in oxidized regions of the solar nebula, and then moved into the enstatite chondrite locations; and (2) Ca, Al-rich inclusions in both enstatite chondrites and carbonaceous chondrites may have similar origins and reservoirs.``

  16. Size distributions and aerodynamic equivalence of metal chondrules and silicate chondrules in Acfer 059

    Science.gov (United States)

    Skinner, William R.; Leenhouts, James M.

    1993-01-01

    The CR2 chondrite Acfer 059 is unusual in that the original droplet shapes of metal chondrules are well preserved. We determined separate size distributions for metal chondrules and silicate chondrules; the two types are well sorted and have similar size distributions about their respective mean diameters of 0.74 mm and 1.44 mm. These mean values are aerodynamically equivalent for the contrasting densities, as shown by calculated terminal settling velocities in a model solar nebula. Aerodynamic equivalence and similarity of size distributions suggest that metal and silicate fractions experienced the same sorting process before they were accreted onto the parent body. These characteristics, together with depletion of iron in Acfer 059 and essentially all other chondrites relative to primitive CI compositions, strongly suggest that sorting in the solar nebula involved a radial aerodynamic component and that sorting and siderophile depletion in chondrites are closely related.

  17. Shock-produced vapor-grown crystals in the Yanzhuang meteorite

    Institute of Scientific and Technical Information of China (English)

    谢先德; 陈鸣

    1997-01-01

    Vapor-grown crystals intimately related to shock metamorphism of meteorites were found in the Yanzhuang (H6) chondrite which had been heavily impacted in the space. These crystals include: (i) subhedral low-Ca pyroxene occurring on the wall of the pores within a silicate melt pocket that experienced a shock temperature higher than 1 500℃, (ii)Fe-Ni needle-whiskers (taenite) occurring in the cracks in the partially melted chondritic facies that experienced a shock temperature of 850-1 300℃ , (iii) troilite with abundant microholes occurring in the cracks in the brecciated facies and the lightly deformed chondritic facies that experienced a shock temperature lower than 850℃ . The occurrence and mineralogical features of vapor-grown crystals show that vaporization of minerals could be produced in heavily impacted meteorites and that a small amount of crystals could be deposited in situ from vapor plus-

  18. Morphological Study of Insoluble Organic Matter Residues from Primitive

    Science.gov (United States)

    Changela, H. G.; Stroud, R. M.; Peeters, Z.; Nittler, L. R.; Alexander, C. M. O'D.; DeGregorio, B. T.; Cody, G. D.

    2012-01-01

    Insoluble organic matter (IOM) constitutes a major proportion, 70-99%, of the total organic carbon found in primitive chondrites [1, 2]. One characteristic morphological component of IOM is nanoglobules [3, 4]. Some nanoglobules exhibit large N-15 and D enrichments relative to solar values, indicating that they likely originated in the ISM or the outskirts of the protoplanetary disk [3]. A recent study of samples from the Tagish Lake meteorite with varying levels of hydrothermal alteration suggest that nanoglobule abundance decreases with increasing hydrothermal alteration [5]. The aim of this study is to further document the morphologies of IOM from a range of primitive chondrites in order to determine any correlation of morphology with petrographic grade and chondrite class that could constrain the formation and/or alteration mechanisms.

  19. Xe and Kr analyses of silicate inclusions from iron meteorites.

    Science.gov (United States)

    Bogard, D. D.; Huneke, J. C.; Burnett, D. S.; Wasserburg, G. J.

    1971-01-01

    Measurements have been conducted of the amounts and isotopic composition of Xe and Kr in silicate inclusions of several iron meteorites. It is shown that the Xe and Kr contents are comparable to chondritic values. The isotopic compositions show trapped gas of both chondritic and atmospheric composition. Large spallation effects occur in some of the meteorites; the spallation spectra in some instances differ from those reported for stone meteorites. In several meteorites, very large neutron capture effects on Br and I occur. All samples have pronounced Xe129 excesses which apparently indicate differences in the formation times from chondrites of less than about 100 million years; however, the presence of trapped Xe132 in silicates which were enclosed in molten Fe-Ni and cooled slowly proves that they were not entirely outgassed, so that some of the Xe129 excess may also be trapped.

  20. Compositional evolution during rocky protoplanet accretion

    CERN Document Server

    Carter, Philip J; Elliott, Tim; Walter, Michael J; Stewart, Sarah T

    2015-01-01

    The Earth appears non-chondritic in its abundances of refractory lithophile elements, posing a significant problem for our understanding of its formation and evolution. It has been suggested that this non-chondritic composition may be explained by collisional erosion of differentiated planetesimals of originally chondritic composition. In this work, we present N-body simulations of terrestrial planet formation that track the growth of planetary embryos from planetesimals. We simulate evolution through the runaway and oligarchic growth phases under the Grand Tack model and in the absence of giant planets. These simulations include a state-of-the-art collision model which allows multiple collision outcomes, such as accretion, erosion, and bouncing events, that enables tracking of the evolving core mass fraction of accreting planetesimals. We show that the embryos grown during this intermediate stage of planet formation exhibit a range of core mass fractions, and that with significant dynamical excitation, enoug...

  1. Timing of Formation of a Wassonite-bearing Chondrule

    Science.gov (United States)

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

    2014-01-01

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

  2. Khatyrka, a new CV3 find from the Koryak Mountains, Eastern Russia

    Science.gov (United States)

    MacPherson, Glenn J.; Andronicos, Christopher L.; Bindi, Luca; Distler, Vadim V.; Eddy, Michael P.; Eiler, John M.; Guan, Yunbin; Hollister, Lincoln S.; Kostin, Alexander; Kryachko, Valery; Steinhardt, William M.; Yudovskaya, Marina; Steinhardt, Paul J.

    2013-08-01

    A new meteorite find, named Khatyrka, was recovered from eastern Siberia as a result of a search for naturally occurring quasicrystals. The meteorite occurs as clastic grains within postglacial clay-rich layers along the banks of a small stream in the Koryak Mountains, Chukotka Autonomous Okrug of far eastern Russia. Some of the grains are clearly chondritic and contain Type IA porphyritic olivine chondrules enclosed in matrices that have the characteristic platy olivine texture, matrix olivine composition, and mineralogy (olivine, pentlandite, nickel-rich iron-nickel metal, nepheline, and calcic pyroxene [diopside-hedenbergite solid solution]) of oxidized-subgroup CV3 chondrites. A few grains are fine-grained spinel-rich calcium-aluminum-rich inclusions with mineral oxygen isotopic compositions again typical of such objects in CV3 chondrites. The chondritic and CAI grains contain small fragments of metallic copper-aluminum-iron alloys that include the quasicrystalline phase icosahedrite. One grain is an achondritic intergrowth of Cu-Al metal alloys and forsteritic olivine ± diopsidic pyroxene, both of which have meteoritic (CV3-like) oxygen isotopic compositions. Finally, some grains consist almost entirely of metallic alloys of aluminum + copper ± iron. The Cu-Al-Fe metal alloys and the alloy-bearing achondrite clast are interpreted to be an accretionary component of what otherwise is a fairly normal CV3 (oxidized) chondrite. This association of CV3 chondritic grains with metallic copper-aluminum alloys makes Khatyrka a unique meteorite, perhaps best described as a complex CV3 (ox) breccia.

  3. Noble gases in meteorites and terrestrial planets

    Science.gov (United States)

    Wacker, J. F.

    1985-01-01

    Terrestrial planets and chondrites have noble gas platforms that are sufficiently alike, especially Ne/Ar, that they may have acquired their noble gases by similar processes. Meteorites presumably obtained their noble gases during formation in the solar nebula. Adsorption onto C - the major gas carrier in chondrites - is the likely mechanism for trapping noble gases; recent laboratory simulations support this hypothesis. The story is more complex for planets. An attractive possibility is that the planets acquired their noble gases in a late accreting veneer of chondritic material. In chondrites, noble gases correlate with C, N, H, and volatile metals; by Occam's Razor, we would expect a similar coupling in planets. Indeed, the Earth's crust and mantle contain chondritic like trace volatiles and PL group metals, respectively and the Earth's oceans resemble C chondrites in their enrichment of D (8X vs 8-10X of the galactic D/H ratio). Models have been proposed to explain some of the specific noble gas patterns in planets. These include: (1) noble gases may have been directly trapped by preplanetary material instead of arriving in a veneer; (2) for Venus, irradiation of preplanetary material, followed by diffusive loss of Ne, could explain the high concentration of AR-36; (3) the Earth and Venus may have initially had similar abundances of noble gases, but the Earth lost its share during the Moon forming event; (4) noble gases could have been captured by planetestimals, possibly leading to gravitational fractionation, particularly of Xe isotopes and (5) noble gases may have been dissolved in the hot outer portion of the Earth during contact with a primordial atmosphere.

  4. Mineralogy of an unusual Cr-rich inclusion in the Los Martinez (L6) chrondritic breccia

    Science.gov (United States)

    Brearley, Adrian J.; Casanova, Ignacio; Miller, M. L.; Keil, Klaus

    1991-01-01

    During the petrological study of the L6 chondritic breccia, Los Martinez, we discovered a large, highly unusual Cr-rich inclusion whose mineralogy appears to be unique in both terrestrial and extraterrestrial occurrences. We carried out electron microprobe, scanning electron microscopy, and transmission electron microscopy investigations of this inclusion in order to determine its composition and mineralogy in detail and to establish its origin and possible relationship to other Cr-rich objects in chondritic meteorites. Details of the chemical composition, origin, and thermal history are given.

  5. Implications of Mars Pathfinder data for the accretion history of the terrestrial planets.

    Science.gov (United States)

    Bertka, C M; Fei, Y

    1998-09-18

    Accretion models of the terrestrial planets often assume planetary bulk compositions with nonvolatile element abundance ratios equivalent to those of C1 carbonaceous chondrites. The moment of inertia factor of Mars reported by the Pathfinder team is inconsistent with a bulk planet C1 Fe/Si ratio or Fe content, which suggests that C1 chondrite accretion models are insufficient to explain the formation of Mars and the other terrestrial planets. Future planetary accretion models will have to account for variations in bulk Fe/Si ratios among the terrestrial planets.

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

    Science.gov (United States)

    Ruzicka, A.; Floss, C.

    2004-01-01

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

  7. Samarium-neodymium systematics in kimberlites and in the minerals of garnet lherzolite inclusions

    Science.gov (United States)

    Basu, A.R.; Tatsumoto, M.

    1979-01-01

    The initial ratios of neodymium-143 to neodymium-144 in kimberlites ranging in age between 90 ?? 106 to 1300 ?? 106 years from South Africa, India, and the United States are different from the corresponding ratios in the minerals of peridotite inclusions in the kimberlites but are identical to the ratios in the basaltic achondrite Juvinas at the times of emplacement of the respective kimberlite pipes. This correlation between the kimberlites and Juvinas, which represents the bulk chondritic earth in rare-earth elements, strongly indicates that the kimberlite's source in the mantle is chondritic in rare-earth elements and relatively primeval in composition. Copyright ?? 1979 AAAS.

  8. Iridium anomaly in the cretaceous-paleogene boundary at Højerup (Stevns Klint, Denmark and Woodside Creek (New Zealand: The question of an enormous proportion of extraterrestrial component

    Directory of Open Access Journals (Sweden)

    Premović Pavle I.

    2012-01-01

    Full Text Available The Cretaceous-Paleogene boundary clays at Højerup and Woodside Creek show anomalous enrichments of iridium compared with the marine sedimentary rocks. For the average iridium content of 465 ppb in CI chondrite the estimate of the carbonaceous chondritic proportions in the decarbonated iridium-rich boundary layers, based on the integrated iridium fluencies, is about 26% at Højerup and 65% at Woodside Creek. These proportions are most likely too high due to a significant Ir influx from the nearby marine or continental site to these sections.

  9. The meteorite collection at Museo di Storia Naturale, Pisa University, Italy

    Science.gov (United States)

    Perchiazzi, Natale; D'Orazio, Massimo; Folco, Luigi

    2004-08-01

    The historical meteorite collection of Museo di Storia Naturale, Pisa University, is presented in this catalog. Dating back to at least 1860, the collection currently (as of June 2003) contains 30 specimens of 26 individual meteorites, representing about 50 kg of extraterrestrial material. The collection includes 2 carbonaceous chondrites, 12 ordinary chondrites, 1 achondrite, 4 stony-iron meteorites, and 7 iron meteorites, including three remarkable specimens: the main mass of Bagnone (48 kg), the fourth largest mass of Quenggouk (717.5 g), and a large (nearly) complete individual of the Siena showerfall (318.8 g).

  10. Meteorites from Grove Mountains, Antarctica:An overview

    Institute of Scientific and Technical Information of China (English)

    王道德; 林杨挺

    2003-01-01

    Thirty-two meteorites were collected in Grove Mountains area, Antarctica,by the 15th and 16th Chinese Antarctic Research Expeditions (CHINARE). Petrography and mineral chemistry of these meteorites are reviewed, among which there are one Martian lherzolite, one eucrite, one ungrouped iron meteorite, and six unequilibrated and twenty-three equilibrated ordinary chondrites. An equilibrated ordinary chondrite GRV 98004 (H5) has an unusually low cosmic-ray exposure age. Meteorite concentrating processes in Grove Mountains area are discussed. In addition, future studies on Grove Mountains (GRV) meteorites are proposed.

  11. Chondrule-like object from the Indian Ocean cosmic spherules

    Indian Academy of Sciences (India)

    K Reshma; N G Rudraswami; M Shyam Prasad

    2013-08-01

    Five hundred and eighteen cosmic spherules were identified among the 672 spherules handpicked from deep sea sediments by using Scanning Electron Microscope-Energy Dispersive Spectrometry (SEM-EDS). One of the spherules is found to enclose a spherical chondrule-like object that can be distinguished from the rest of the spherule by its shape, texture and composition and whose petrographic features, size and chemical composition are similar to chondrules from a chondritic meteorite, probably of carbonaceous chondritic nature. The present finding suggests that a small fraction of the particulate extraterrestrial matter enters the earth as fragments of larger meteorites.

  12. Maribo - a new CM fall from Denmark

    DEFF Research Database (Denmark)

    Haack, Henning; Grau, Thomas; Bischoff, Addi;

    2012-01-01

    Maribo is a new Danish CM chondrite, which fell on January 17, 2009, at 19:08:28 CET. The fall was observed by many eye witnesses and recorded by a surveillance camera, an all sky camera, a few seismic stations, and by meteor radar observatories in Germany. A single fragment of Maribo with a dry ...... CM chondrites, stepwise heating data indicating the presence of gas components hosted by presolar diamond and silicon carbide. The organics in Maribo include components also seen in Murchison as well as nitrogen-rich components unique to Maribo....

  13. Early Solar System Cryovolcanics in the Laboratory

    Science.gov (United States)

    Zolensky, M.; Fries, M.; Bodnar, R.; Yurimoto, H.; Itoh, S.; Steele, A.; Mikouchi, T.; Hagiya, K.; Ohsumi, K.; Le, L.; Rahman, Z.

    2013-01-01

    Two thermally-metamorphosed ordinary chondrite regolith breccias, Monahans 1998 (H5) and Zag (H3-6) contain fluid inclusion-bearing halite (NaCl) crystals, dated by K-Ar, Rb-Sr and I-Xe systematics to be approx. 4.5 billion years old. Heating/freezing studies of the aqueous fluid inclusions demonstrated that they were trapped near 25 C, and their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism.

  14. Meteorite-asteroid spectral comparison - The effects of comminution, melting, and recrystallization

    Science.gov (United States)

    Clark, Beth E.; Fanale, Fraser P.; Salisbury, John W.

    1992-01-01

    The present laboratory simulation of possible spectral-alteration effects on the optical surface of ordinary chondrite parent bodies duplicated regolith processes through comminution of the samples to finer rain sizes. After reflectance spectra characterization, the comminuted samples were melted, crystallized, recomminuted, and again characterized. While individual spectral characteristics could be significantly changed by these processes, no combination of the alteration procedures appeared capable of affecting all relevant parameters in a way that improved the match between chondritic meteorites and S-class asteroids.

  15. Reflectance spectroscopy and asteroid surface mineralogy

    Science.gov (United States)

    Gaffey, Michael J.; Bell, Jeffrey F.; Cruikshank, Dale P.

    1989-01-01

    Information available from reflectance spectroscopy on the surface mineralogy of asteroids is discussed. Current spectral interpretive procedures used in the investigations of asteroid mineralogy are described. Present understanding of the nature and history of asteroids is discussed together with some still unresolved issues such as the source of ordinary chondrites.

  16. A note on cement in asteroids

    Science.gov (United States)

    Bilalbegović, G.

    2016-09-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 μm were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 μm.

  17. Lunar and Planetary Science XXXV: Meteorites to and from the Moon and Mars: My Planet or Yours?

    Science.gov (United States)

    2004-01-01

    The titles in this section include: 1) Meteorites from Mars - Constraints from Numerical Modeling; 2) Iron Oxidation Products in Martian Ordinary Chondrite Finds as Possible Indicators of Liquid Water Exposure at Mars Exploration Rover Landings Sites; 3) Meteorites on Mars; 4) Sulfide Stability of Planetary Basalts; 5) Exposure and Terrestrial Histories of New Lunar and Martian Meteorites.

  18. Laser Irradiated Impact Experiments Show that Nanophase Iron Particles Formed by Shock-Induced Melting Rather than Vapor Deposition

    Science.gov (United States)

    Li, Y.; Li, S. J.; Xie, Z. D.; Li, X. Y.

    2016-08-01

    As the laser irradiated results of chondrite, Impact melting fractionation of ferromagnesian silicates induced by meteorites may be the major origin of np-Fe0, rather than vapour deposition origin only, especially for np-Fe0 in agglutinatic glasses.

  19. Instrumental neutron activation analysis of carbonatites from Panda Hill and Oldoinyo-Lengai, Tanzania

    International Nuclear Information System (INIS)

    Twenty nine (major and trace) elements including nine rare earth elements (REE) in African carbonatite samples were determined by instrumental neutron activation analysis (INAA). The geochemical behavior of trace elements in carbonatites, especially REE pattern (chondrite normalized), and the efficiency of neutron activation analysis compared to other methods are discussed in this study. (author)

  20. Tungsten isotopes in bulk meteorites and their inclusions—Implications for processing of presolar components in the solar protoplanetary disk

    Science.gov (United States)

    Holst, J. C.; Paton, C.; Wielandt, D.; Bizzarro, M.

    2016-01-01

    We present high precision, low- and high-resolution tungsten isotope measurements of iron meteorites Cape York (IIIAB), Rhine Villa (IIIE), Bendego (IC), and the IVB iron meteorites Tlacotepec, Skookum, and Weaver Mountains, as well as CI chondrite Ivuna, a CV3 chondrite refractory inclusion (CAI BE), and terrestrial standards. Our high precision tungsten isotope data show that the distribution of the rare p-process nuclide 180W is homogeneous among chondrites, iron meteorites, and the refractory inclusion. One exception to this pattern is the IVB iron meteorite group, which displays variable excesses relative to the terrestrial standard, possibly related to decay of rare 184Os. Such anomalies are not the result of analytical artifacts and cannot be caused by sampling of a protoplanetary disk characterized by p-process isotope heterogeneity. In contrast, we find that 183W is variable due to a nucleosynthetic s-process deficit/r-process excess among chondrites and iron meteorites. This variability supports the widespread nucleosynthetic s/r-process heterogeneity in the protoplanetary disk inferred from other isotope systems and we show that W and Ni isotope variability is correlated. Correlated isotope heterogeneity for elements of distinct nucleosynthetic origin (183W and 58Ni) is best explained by thermal processing in the protoplanetary disk during which thermally labile carrier phases are unmixed by vaporization thereby imparting isotope anomalies on the residual processed reservoir. PMID:27445452

  1. Refractory metal nuggets in different types of cosmic spherules.

    Digital Repository Service at National Institute of Oceanography (India)

    Rudraswami, N.G.; ShyamPrasad, M.; Plane, J.M.C.; Berg, T.; Feng, W.; Balgar, S.

    a fremdling-like object in a cosmic spherule which has a nugget encased in Fe–Ni and sulfide phases, similar to those typically observed in CAIs of CV or CO chondrites. The atmospheric entry for this rare cosmic spherule appears to have taken place...

  2. Generating potassium abundance variations in the Solar Nebula

    Science.gov (United States)

    Hubbard, Alexander

    2016-08-01

    An intriguing aspect of chondritic meteorites is that they are complementary: while their separate components have wildly varying abundances, bulk chondrites have nearly solar composition. This implies that the nearly solar reservoirs in which chondrites were born were in turn assembled from sub-reservoirs of differing compositions that birthed the different components. We focus on explaining the potassium abundance variations between chondrules even within a single chondrite, while maintaining the observed CI 41K to 39K ratios. This requires physically separating potassium and chondrules while the temperature is high enough for K to be in the gas phase. We examine several mechanisms which could drive the dust through gas and show that to do so locally would have required long (sub-orbital to many orbits) time scales; with shortest potassium depletion time-scales occurring in a scenario where chondrules formed high above the mid-plane and settled out of the evaporated potassium. While orbital time-scales are at odds with laboratory chondrule cooling rate estimates, any other model for the origin for the potassium abundance variation has to wrestle with the severe logistical difficulty of generating a plethora of correlated reservoirs which varied strongly in their potassium abundances, but not in their potassium isotope ratios.

  3. Asteroid Regolith Simulants: Development, Characteristics, and Testing

    Science.gov (United States)

    Britt, D. T.

    2015-12-01

    As part of a NASA Small Business Innovation Research (SBIR) award to the University of Central Florida and Deep Space Industries, we are developing a family of asteroid regolith simulants based on meteorite mineralogies but using terrestrial materials, to support NASAs exploration goals for asteroids. We are planning on developing five types of simulant based on the following meteorite types: CI-carbonaceous chondrite, CM-carbonaceous chondrite, Tagish Lake, L-ordinary chondrite, and iron. To the greatest extent reasonable (based on input costs and health/safety) we will duplicate the mineralogy, chemistry, oxidation state, hydration state, and particle size distribution found in regolith meteorites of each type. The major limitations on the fidelity of simulant will be health and safety issues for the users of the simulants. For example, much of the organic component of volatile-rich carbonaceous chondrites are in the form of Polycyclic Aromatic Hydrocarbons (PAHs). These are essentially combustion residues, possibly of complex regolith processing, with more carbon atoms than hydrogen. However, many PAHs are toxic, carcinogenic, and/or mutagenic. Several are banned in the European Union and California. This sort of material would endanger users, be impossible to distribute, and not make a useable regolith simulant. There are several reasonable, no-toxic alternatives to PAHs. We will report on the status of simulant development and the progress of our validation experiments.

  4. A note on cement in asteroids

    CERN Document Server

    Bilalbegovic, G

    2016-01-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 microns were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 microns.

  5. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites.

    Science.gov (United States)

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H; Ramasse, Quentin M; Hoppe, Peter; Nittler, Larry R

    2014-10-28

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight (15)N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C-O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C-O bonding environments and nanoglobular organics with dominant aromatic and C-N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid.

  6. Organic matter on asteroid 130 Elektra

    Science.gov (United States)

    Cruikshank, D. P.; Brown, R. H.

    1987-01-01

    Infrared absorption spectra of a low-albedo water-rich asteroid appear to show a weak 3.4-micrometer carbon-hydrogen stretching mode band, which suggests the presence of hydrocarbons on asteroid 130 Elektra. The organic extract from the primitive carbonaceous chondritic Murchison meteorite shows similar spectral bands.

  7. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites

    Science.gov (United States)

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H.; Ramasse, Quentin M.; Hoppe, Peter; Nittler, Larry R.

    2014-01-01

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight 15N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C–O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C–O bonding environments and nanoglobular organics with dominant aromatic and C–N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  8. Formation of the Mont Dieu IIE Non Magmatic Iron Meteorite, and Origin of its Silicate Inclusions

    Science.gov (United States)

    van Roosbroek, N.; Goderis, S.; Debaille, V.; Valley, J. W.; Claeys, Ph.

    2012-03-01

    Mont Dieu is an IIE nonmagmatic iron meteorite showing primitive features such as preserved chondrules and glass. SEM and geochemical analyses demonstrate that it most likely originated from an H-chondrite parent body impacted by a Fe-Ni projectile.

  9. Properties of the Guin ungrouped iron meteorite - The origin of Guin and of group-IIE irons

    Science.gov (United States)

    Rubin, A. E.; Jerde, E. A.; Zong, P.; Wasson, J. T.; Mayeda, T. K.

    1986-01-01

    The composition and structure of the Guin ungrouped iron meteorite inclusions have been investigated experimentally. The structural characteristics of polished and etched slabs of the meteorite were studied microscopically in reflected light. Modal abundances of troilite nodules and silicate inclusions were determined by weighing paper traces. The bulk composition of the silicate inclusions was calculated by combining modal phase abundances and mineral compositions. It is found that the largest silicate inclusion (2 x 4 cm) consists mostly of a shock-melted plagioclase-rich matrix surrounding large, partly melted augite grains. The oxygen isotopic composition of the inclusion is near that of LL chondrites. The inclusion is found to be similar in composition to selected melt pocket glasses in ordinary chondrites produced in situ by preferential melting of plagioclase rock due to shock compression. It is suggested that the Guin assemblage was formed by impact melting on a chondritic parent body. Silicate inclusions in IIE irons share many of the compositional and petrological characteristics of the Guin inclusions, indicating that IIE irons also formed by impact-melting of chondritic materials. Black and white photomicrographs of the silicate inclusions are provided.

  10. Veins in Silicates of IIE Iron Mont Dieu II: Melt Migration Caused by Impact?

    Science.gov (United States)

    Van Roosbroek, N.; Debaille, V.; Pittarello, L.; Hecht, L.; Claeys, Ph.

    2014-09-01

    Mont Dieu II is a ~450kg meteorite classified as IIE iron. The primitive silicate inclusions can be linked to the H-chondrites. Thick metal veins with angular clasts crosscut these inclusions and could point to an impact-melt migration formation.

  11. Nano-XRF Study of Earliest Solar Condensates in EL-3 Fragments from the Almahata Sitta TC3 Asteroid

    Science.gov (United States)

    Simionovici, A. S.; Lemelle, L.; Boyet, M.; Gillet, Ph.; Rivard, C.; El Goresy, A.

    2014-09-01

    A nano-XRF study of enstatite chondritic fragments of the Almahata Sitta TC3 asteroid was performed at the ID21 beamline of the ESRF synchrotron in Grenoble, France. We report on the identification and composition of idiomorphic sinoite crystals.

  12. New Individuals from the Almahata Sitta Strewn Field: Old Friends and Brand-New Fellows

    Science.gov (United States)

    Bischoff, A.; Ebert, S.; Patzek, M.; Horstmann, M.; Pack, A.; Barrat, J.-A.; Decker, S.

    2015-07-01

    Nine new samples (MS-MU-012-MS-MU-020) from the Almahata Sitta strewn field were studied including ureilitic samples, chondrites, and a unique sample (MS-MU-019). Among these MS-MU-012 is an unbrecciated, ureilitic feldspar-olivine-pyroxene rock.

  13. Trapping of xenon in ice - Implications for the origin of the earth's noble gases

    Science.gov (United States)

    Wacker, J. F.; Anders, E.

    1984-01-01

    Although the earth's atmosphere contains Ne, Ar, and Kr in about C1,2-chondrite proportions, Xe is depleted about 20-fold. To test the suggestion that the 'missing' Xe is trapped in Antarctic ice, distribution coefficients for Xe in artifically formed frost at -20 to -60 C were measured, using Xe-127 tracer. The values are 0.098 + or - 0.004 cc STP/g atm for trapping and less than 5 cc STP/g atm for trapping plus adsorption. If these results are representative of natural ice, then the Antarctic ice cap contains less than 1 percent of the atmospheric Xe inventory, or not greater than about 0.001 the amount needed for a C1,2-chondrite pattern. Two possibilities remain for the 'missing' Xe, both on the premise that the earth's noble gases, along with other volatiles, came from chondritic material: (1) xenon is preferentially retained in the mantle and lower crust, due to the strong affinity of Xe for clean silicate surfaces and amorphous carbon; and (2) the source material of the earth's volatiles had high, relatively unfractionated, Ar/Xe and Kr/Xe ratios, like the non-carbonaceous noble gas carriers in C3O and E-chondrites.

  14. Spectrophotometry and UBVRI photometry of Eros

    Science.gov (United States)

    Wisniewski, W. Z.

    1976-01-01

    Spectrophotometric and broad-band photoelectric observations of Eros are reported. No existing meteorite spectrum matches the asteroid data directly. Assemblages of iron or stony-iron with ordinary-chondrite material generate the best match for the reflectivity curve of Eros. Variability was found in the 0.6 micron band and V-R and V-I colors.

  15. Abundance, distribution, and origin of 60Fe in the solar protoplanetary disk

    CERN Document Server

    Tang, Haolan; 10.1016/j.epsl.2012.10.011

    2012-01-01

    Meteorites contain relict decay products of short-lived radionuclides that were present in the protoplanetary disk when asteroids and planets formed. Several studies reported a high abundance of 60Fe (t1/2=2.62+/-0.04 Myr) in chondrites (60Fe/56Fe~6*10-7), suggesting that planetary materials incorporated fresh products of stellar nucleosynthesis ejected by one or several massive stars that exploded in the vicinity of the newborn Sun. We measured 58Fe/54Fe and 60Ni/58Ni isotope ratios in whole rocks and constituents of differentiated achondrites (ureilites, aubrites, HEDs, and angrites), unequilibrated ordinary chondrites Semarkona (LL3.0) and NWA 5717 (ungrouped petrologic type 3.05), metal-rich carbonaceous chondrite Gujba (CBa), and several other meteorites (CV, EL H, LL chondrites; IIIAB, IVA, IVB iron meteorites). We derive from these measurements a much lower initial 60Fe/56Fe ratio of (11.5+/-2.6)*10-9 and conclude that 60Fe was homogeneously distributed among planetary bodies. This low ratio is consist...

  16. Highly Siderophile and Chalcophile Elements in Lunar Impact Rocks: Constraints on the Composition of Late Accreted Material

    Science.gov (United States)

    Gleißner, P.; Becker, H.

    2016-08-01

    HSE, Te, Se and S composition of ancient lunar impactites reveal the late accretion of chondrite-like material along with differentiated core metal. HSE patterns are consistent with parent body P/S ratios higher than most magmatic iron meteorites.

  17. Boron abundances and isotopic ratios of olivine grains on Itokawa returned by the Hayabusa spacecraft

    Science.gov (United States)

    Fujiya, Wataru; Hoppe, Peter; Ott, Ulrich

    2016-09-01

    We report the B abundances and isotopic ratios of two olivine grains from the S-type asteroid Itokawa sampled by the Hayabusa spacecraft. Olivine grains from the Dar al Gani (DaG) 989 LL6 chondrite were used as a reference. Since we analyzed polished thin sections in both cases, we expect the contribution from the solar wind B (rich in 10B) to be minimal because the solar wind was implanted only within very thin layers of the grain surface. The Itokawa and DaG 989 olivine grains have homogeneous B abundances (~400 ppb) and 11B/10B ratios compatible with the terrestrial standard and bulk chondrites. The observed homogeneous B abundances and isotopic ratios of the Itokawa olivine grains are likely the result of thermal metamorphism which occurred in the parent asteroid of Itokawa, which had a similar composition as LL chondrites. The chondritic B isotopic ratios of the Itokawa samples suggest that they contain little cosmogenic B (from cosmic-ray spallation reactions) rich in 10B. This observation is consistent with the short cosmic-ray exposure ages of Itokawa samples inferred from the small concentrations of cosmogenic 21Ne. If other Itokawa samples have little cosmogenic B as well, the enrichment in 10B found previously on the surface of another Itokawa particle (as opposed to the bulk grain study here) may be attributed to implanted solar wind B.

  18. Delivery of Organic Material and Water through Asteroid Impacts

    NARCIS (Netherlands)

    Mueller, Michael; Frantseva, Kateryna; van der Tak, Floris; Helmich, Frank P.

    2014-01-01

    Meteorites, specifically carbonaceous chondrites, are frequently invoked as the primary source of Earth's water and organic materials, crucial ingredients for the formation of life. We have started developing a dynamical model of the delivery of their parent bodies, primitive low-albedo asteroids, f

  19. 2P/Encke, the Taurid complex NEOs and the Maribo and Sutter’s Mill meteorites

    DEFF Research Database (Denmark)

    Tubiana, C.; Snodgrass, C.; Michelsen, Rene;

    2015-01-01

    , 2012, respectively. Their pre-atmospheric orbits place them in the middle of the Taurid meteoroid stream, which raises the intriguing possibility that comet 2P/Encke could be the parent body of CM chondrites. Methods. To investigate whether a relationship between comet 2P/Encke, the Taurid complex...

  20. New Indivisible Geoscience Paradigm

    CERN Document Server

    Herndon, J Marvin

    2011-01-01

    Earth's interior, I posit, is like one of the rare, oxygen-starved "enstatite chondrite" meteorites (and unlike a more-oxidized "ordinary chondrite" as has been believed for seventy years). Laboratory-analyzed enstatite-chondrite samples are comparable to having-in-hand impossibleto- gather deep-Earth samples. Enstatite-chondrite formation in oxygen-starved conditions caused oxygen-loving elements to occur, in part, as non-oxides in their iron-alloy. Observations, consistent with solar abundance and behavior of chemical elements, lead me to a new interpretation of: (1) Earth's early formation as a Jupiter-like gas-giant, (2) its decompressionpowered surface geology, (3) Earth's internal composition, and (4) a natural, planetocentric nuclear-fission reactor as source of both the geomagnetic field and energy channeled to surface "hot-spots". I present a unified vision of Earth formation and concomitant dynamics that explains in a logical and causally related way: (1) fluid Earth-core formation without wholeplan...

  1. A new type of solar-system material recovered from Ordovician marine limestone.

    Science.gov (United States)

    Schmitz, B; Yin, Q-Z; Sanborn, M E; Tassinari, M; Caplan, C E; Huss, G R

    2016-01-01

    From mid-Ordovician ∼470 Myr-old limestone >100 fossil L-chondritic meteorites have been recovered, representing the markedly enhanced flux of meteorites to Earth following the breakup of the L-chondrite parent body. Recently one anomalous meteorite, Österplana 065 (Öst 65), was found in the same beds that yield L chondrites. The cosmic-ray exposure age of Öst 65 shows that it may be a fragment of the impactor that broke up the L-chondrite parent body. Here we show that in a chromium versus oxygen-isotope plot Öst 65 falls outside all fields encompassing the known meteorite types. This may be the first documented example of an 'extinct' meteorite, that is, a meteorite type that does not fall on Earth today because its parent body has been consumed by collisions. The meteorites found on Earth today apparently do not give a full representation of the kind of bodies in the asteroid belt ∼500 Myr ago. PMID:27299793

  2. Reconstruction of exposure histories of meteorites from Antarctica and the Sahara

    Energy Technology Data Exchange (ETDEWEB)

    Neupert, U.; Neumann, S.; Leya, I.; Michel, R. [Hannover Univ. (Germany). Zentraleinrichtung fuer Strahlenschutz (ZfS); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Bonani, G.; Hajdas, I.; Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    {sup 10}Be, {sup 14}C, and {sup 26}Al were analyzed in H-, L-, and LL-chondrites from the Acfer region in the Algerian Sahara and from the Allan Hills/Antarctica. Exposure histories and terrestrial ages could be determined. (author) 3 figs., 2 refs.

  3. A New Old Meteorite Find from Claromeco, Argentina

    Science.gov (United States)

    Acevedo, R. D.; Subías, I.

    2012-09-01

    Two reddish brown meteoritic stones of 13 kg each were found in 1963 leaning against a windmill in a farm at argentine pampas (38º 48" 16"" S, 60º 07" 23"" W), but they are the focus of attention just now. This meteorite could be classified as a LL ordinary chondrite.

  4. Rare Earth Elements Distribution in Beryl

    International Nuclear Information System (INIS)

    Laser ablation method is applied to a double focusing inductively coupled plasma mass spectrometer to determine the rare earth element distribution in some selected beryl samples. White, green and blue beryl samples are selected from the Egyptian eastern desert. Distributions of chondrite- normalized plot for the rare earth element in the selected beryl samples are investigated

  5. Cosmic-ray-produced KR in St. Severin core AIII

    Science.gov (United States)

    Lavielle, B.; Marti, K.

    Kr isotopic abundances in 10 samples from core AIII of the St. Severin chondrite are reported, and the variation with depth of cosmic-ray produced Kr is discussed. It is shown that the ratio (Kr-78/Kr-83)c changes with depth and can be used as an irradiation hardness monitor. Cosmic-ray-produced Kr and Ne in the St. Severin core are compared with ratios observed in bulk chondrites. A linear correlation between (Ne-22/Ne-21)c and (Kr-78/Kr-83)c exists for bulk samples of chondrites of varying preatmospheric size, but does not exist in the St. Severin core. The calculated Kr-83 production rates, P83, are similar in H, L, and LL chondrites for samples of comparable shielding conditions. However, P83 rates increase by a factor of about 2 with shielding depth. The maximum observed P83 values correspond to (Kr-78/Kr-83)c factor of about 2 with shielding depth. The maximum observed P83 values correspond to (Kr-78/Kr-83)c less than about 0.14.

  6. Boron abundances and isotopic ratios of olivine grains on Itokawa returned by the Hayabusa spacecraft

    Science.gov (United States)

    Fujiya, Wataru; Hoppe, Peter; Ott, Ulrich

    2016-07-01

    We report the B abundances and isotopic ratios of two olivine grains from the S-type asteroid Itokawa sampled by the Hayabusa spacecraft. Olivine grains from the Dar al Gani (DaG) 989 LL6 chondrite were used as a reference. Since we analyzed polished thin sections in both cases, we expect the contribution from the solar wind B (rich in 10B) to be minimal because the solar wind was implanted only within very thin layers of the grain surface. The Itokawa and DaG 989 olivine grains have homogeneous B abundances (~400 ppb) and 11B/10B ratios compatible with the terrestrial standard and bulk chondrites. The observed homogeneous B abundances and isotopic ratios of the Itokawa olivine grains are likely the result of thermal metamorphism which occurred in the parent asteroid of Itokawa, which had a similar composition as LL chondrites. The chondritic B isotopic ratios of the Itokawa samples suggest that they contain little cosmogenic B (from cosmic-ray spallation reactions) rich in 10B. This observation is consistent with the short cosmic-ray exposure ages of Itokawa samples inferred from the small concentrations of cosmogenic 21Ne. If other Itokawa samples have little cosmogenic B as well, the enrichment in 10B found previously on the surface of another Itokawa particle (as opposed to the bulk grain study here) may be attributed to implanted solar wind B.

  7. Near-Earth Asteroid Origin for the Farmington Meteorite

    Science.gov (United States)

    Marti, K.; Mathew, K. J.

    2002-01-01

    We report nitrogen and xenon isotopic signatures in separated metal and non-magnetic phases of a catastrophically degassed L5 chondrite and discuss implications for the collisional event and the impactor. Additional information is contained in the original extended abstract.

  8. 26Al-26Mg deficit dating ultramafic meteorites and silicate planetesimal differentiation in the early Solar System?

    DEFF Research Database (Denmark)

    Baker, J.A.; Schiller, M.; Bizzarro, Martin

    2012-01-01

    Meteorites with significantly sub-chondritic Al/Mg that formed in the first 2million years of the Solar System should be characterised by deficits in the abundance of Mg (d Mg ) due to the absence of in-growth of Mg from the decay of short-lived Al (t =0.73Myr). However, these Mg deficits will be...

  9. Na-Fe-Phosphate Globules in Impact Metal-Troilite Associations of Chelyabinsk Meteorite

    Science.gov (United States)

    Sharygin, V. V.; Karmanov, N. S.; Podgornykh, N. M.

    2016-08-01

    Multi- and monophase phosphate globules have been found in the impact metal-troilite aggregates of the Chelyabinsk chondrite. Their phase composition varies and they contain galileiite, sarcopside, graftonite and Na-Fe-phosphate Na2(Fe,Mn)5(PO4)4.

  10. Evaporation of nebular fines during chondrule formation

    Science.gov (United States)

    Wasson, John T.

    2008-06-01

    Studies of matrix in primitive chondrites provide our only detailed information about the fine fraction (diameter solar nebula. A minor fraction of the fines, the presolar grains, offers information about the kinds of materials present in the molecular cloud that spawned the Solar System. Although some researchers have argued that chondritic matrix is relatively unaltered presolar matter, meteoritic chondrules bear witness to multiple high-temperature events each of which would have evaporated those fines that were inside the high-temperature fluid. Because heat is mainly transferred into the interior of chondrules by conduction, the surface temperatures of chondrules were probably at or above 2000 K. In contrast, the evaporation of mafic silicates in a canonical solar nebula occurs at around 1300 K and FeO-rich, amorphous, fine matrix evaporates at still lower temperatures, perhaps near 1200 K. Thus, during chondrule formation, the temperature of the placental bath was probably >700 K higher than the evaporation temperatures of nebular fines. The scale of chondrule forming events is not known. The currently popular shock models have typical scales of about 10 km. The scale of nebular lightning is less well defined, but is certainly much smaller, perhaps in the range 1 to 1000 m. In both cases the temperature pulses were long enough to evaporate submicrometer nebular fines. This interpretation disagrees with common views that meteoritic matrix is largely presolar in character and CI-chondrite-like in composition. It is inevitable that presolar grains (both those recognized by their anomalous isotopic compositions and those having solar-like compositions) that were within the hot fluid would also have evaporated. Chondrule formation appears to have continued down to the temperatures at which planetesimals formed, possibly around 250 K. At temperatures >600 K, the main form of C is gaseous CO. Although the conversion of CO to CH 4 at lower temperatures is kinetically

  11. Lunar and Planetary Science XXXVI, Part 1

    Science.gov (United States)

    2005-01-01

    Contents include the following: Observations with Near Infrared Spectrometer for Hayabusa Mission in the Cruising Phase. First Results of Quadrantid Meteor Spectrum. Compositional Investigation of Binary Near-Earth Asteroid 66063 (1998 RO1): A Potentially Undifferentiated Assemblage. Impact-induced Hydrothermal Activity on Early Mars. HRTEM and EFTEM Studies of Phyllosilicate-Organic Matter Associations in Matrix and Dark Inclusions in the EET92042 CR2 Carbonaceous Chondrite. Volumetric Analysis of Martian Rampart Craters. High Pressure Melting of H-Chondrite: A Match for the Martian Basalt Source Mantle. MERView: A New Computer Program for Easy Display of MER-acquired M ssbauer Data. Distribution, Exchange, and Topographic Control of Subsurface Ice on Mars. Shock-induced Damage Beneath Normal and Oblique Impact Craters. Amphitrites Patera Studied from the Mars Express HRSC Data. Oxygen Isotope Microanalysis of Enveloping Compound Chondrules in CV3 and LL3 Chondrites. Gamma-Ray Irradiation in the Early Solar System and the Conundrum of the Lu-176 Decay Constant. Magnesium Isotope Mapping of Silica-rich Grains Having. Extreme Oxygen Isotope Anomalies Extreme Oxygen Isotopic Anomalies from Irradiation in the Early Solar System, Re-Examining the Role of Chondrules in Producing the Elemental Fractionations in Chondrites. Meteorite Data on the Solar Modulation of Galactic Cosmic Rays and an Inference on the Solar Activity Influence on Climate of the Earth. Volatiles Enrichments and Composition of Jupiter. Thinking Like a Wildcatter Prospecting for Methane in Arabia Terra, Mars. Size Distribution of Genesis Solar Wind Array Collector Fragments. Initial Subdivision of Genesis Early Science Polished Aluminum Collector. Presolar Graphite and Its Noble Gases. Young Pb-Isotopic Ages of Chondrules in CB Carbonaceous Chondrites. Fe Isotopic Composition of Martian Meteorites. Petrology and Geochemistry of Nakhlite MIL 03346: A New Martian Meteorite from Antarctica.

  12. Applications of the 190Pt-186Os isotope system to geochemistry and cosmochemistry

    Science.gov (United States)

    Walker, R.J.; Morgan, J.W.; Beary, E.S.; Smoliar, M.I.; Czamanske, G.K.; Horan, M.F.

    1997-01-01

    Platinum is fractionated from osmium primarily as a consequence of processes involving sulfide and metal crystallization. Consequently, the 190Pt-186Os isotope system (190Pt ??? 186Os + ??) shows promise for dating some types of magmatic sulfide ores and evolved iron meteorites. The first 190Pt-186Os isochrons are presented here for ores from the ca. 251 Ma Noril'sk, Siberia plume, and for group IIAB magmatic iron meteorites. Given the known age of the Noril'sk system, a decay constant for 190Pt is determined to be 1.542 ?? 10-12a-1, with ??1% uncertainty. The isochron generated for the IIAB irons is consistent with this decay constant and the known age of the group. The 186Os/188Os ratios of presumably young, mantle-derived osmiridiums and also the carbonaceous chondrite Allende were measured to high-precision to constrain the composition of the modern upper mantle. These compositions overlap, indicating that the upper mantle is chondritic within the level of resolution now available. Our best estimate for this 186Os/188Os ratio is 0.119834 ?? 2 (2??M). The 190Pt/186Os ratios determined for six enstatite chondrites average 0.001659 ?? 75, which is very similar to published values for carbonaceous chondrites. Using this ratio and the presumed composition of the modern upper mantle and chondrites, a solar system initial 186Os/188Os ratio of 0.119820 is calculated. In comparison to the modern upper mantle composition, the 186Os/188Os ratio of the Noril'sk plume was approximately 0.012% enriched in 186Os. Possible reasons for this heterogeneity include the recycling of Pt-rich crust into the mantle source of the plume and derivation of the osmium from the outer core. Derivation of the osmium from the outer core is our favored model. Copyright ?? 1997 Elsevier Science Ltd.

  13. Implications for Core Formation of the Earth from High Pressure-Temperature Au Partitioning Experiments

    Science.gov (United States)

    Danielson, L. R.; Sharp, T. G.; Hervig, R. L.

    2005-01-01

    Siderophile elements in the Earth.s mantle are depleted relative to chondrites. This is most pronounced for the highly siderophile elements (HSEs), which are approximately 400x lower than chondrites. Also remarkable is the relative chondritic abundances of the HSEs. This signature has been interpreted as representing their sequestration into an iron-rich core during the separation of metal from silicate liquids early in the Earth's history, followed by a late addition of chondritic material. Alternative efforts to explain this trace element signature have centered on element partitioning experiments at varying pressures, temperatures, and compositions (P-T-X). However, first results from experiments conducted at 1 bar did not match the observed mantle abundances, which motivated the model described above, a "late veneer" of chondritic material deposited on the earth and mixed into the upper mantle. Alternatively, the mantle trace element signature could be the result of equilibrium partitioning between metal and silicate in the deep mantle, under P-T-X conditions which are not yet completely identified. An earlier model determined that equilibrium between metal and silicate liquids could occur at a depth of approximately 700 km, 27(plus or minus 6) GPa and approximately 2000 (plus or minus 200) C, based on an extrapolation of partitioning data for a variety of moderately siderophile elements obtained at lower pressures and temperatures. Based on Ni-Co partitioning, the magma ocean may have been as deep as 1450 km. At present, only a small range of possible P-T-X trace element partitioning conditions has been explored, necessitating large extrapolations from experimental to mantle conditions for tests of equilibrium models. Our primary objective was to reduce or remove the additional uncertainty introduced by extrapolation by testing the equilibrium core formation hypothesis at P-T-X conditions appropriate to the mantle.

  14. Searching for Organics Preserved in 4.5 Billion Year Old Salt

    Science.gov (United States)

    Zolensky, Michael E.; Fries, M.; Steele, A.; Bodnar, R.

    2012-01-01

    Our understanding of early solar system fluids took a dramatic turn a decade ago with the discovery of fluid inclusion-bearing halite (NaCl) crystals in the matrix of two freshly fallen brecciated H chondrite falls, Monahans and Zag. Both meteorites are regolith breccias, and contain xenolithic halite (and minor admixed sylvite -- KCl, crystals in their regolith lithologies. The halites are purple to dark blue, due to the presence of color centers (electrons in anion vacancies) which slowly accumulated as 40K (in sylvite) decayed over billions of years. The halites were dated by K-Ar, Rb-Sr and I-Xe systematics to be 4.5 billion years old. The "blue" halites were a fantastic discovery for the following reasons: (1) Halite+sylvite can be dated (K is in sylvite and will substitute for Na in halite, Rb substitutes in halite for Na, and I substitutes for Cl). (2) The blue color is lost if the halite dissolves on Earth and reprecipitates (because the newly-formed halite has no color centers), so the color serves as a "freshness" or pristinity indicator. (3) Halite frequently contains aqueous fluid inclusions. (4) Halite contains no structural oxygen, carbon or hydrogen, making them ideal materials to measure these isotopic systems in any fluid inclusions. (5) It is possible to directly measure fluid inclusion formation temperatures, and thus directly measure the temperature of the mineralizing aqueous fluid. In addition to these two ordinary chondrites halite grains have been reliably reported in several ureilites, an additional ordinary chondrite (Jilin), and in the carbonaceous chondrite (Murchison), although these reports were unfortunately not taken seriously. We have lately found additional fluid inclusions in carbonates in several additional carbonaceous chondrites. Meteoritic aqueous fluid inclusions are apparently relatively widespread in meteorites, though very small and thus difficult to analyze.

  15. Impact history of the Chelyabinsk meteorite: Electron microprobe and LA-ICP-MS study of sulfides and metals

    Science.gov (United States)

    Andronikov, A. V.; Andronikova, I. E.; Hill, D. H.

    2015-12-01

    Electron microprobe and LA-ICP-MS study of sulfides and metals from two fragments of the LL5 Chelyabinsk meteorite were conducted. The fragments are impact breccias, one fragment contains both chondritic and shock vein lithologies, and the other contains shock-darkened chondritic clasts and vesicular impact melts. The chondritic lithology and shock veins display very similar opaque mineral compositions. The mineral compositions in the impact-melt breccias are distinctly different. The brecciated state of the Chelyabinsk meteorite suggests strong involvement of shock-related processes during the evolution of the parent body. Multiple heavy impact events occurred on the parent asteroid and on the Chelyabinsk meteoroid itself over the time period from ca. 4.5 Ga until ca. 1.2 Ma. The shock veins were produced in situ on the parent body. The impact-melt breccias could have formed because of the dramatic impact to the parent LL-chondrite body that could be partly disintegrated. The fragment containing shock-darkened chondritic clasts and vesicular impact melt lithologies preserves a record of melting, volatilization, partial degassing, and quenching of the molten material. The abundance and size (up to 1 mm) of the vesicles suggest that the impact melt must have been buried at some depth after formation. After impact and subsequent melting occurred, the impact-induced pressure on the shallow asteroid interior was released that caused "boiling" of volatiles and generation of S-rich bubbles. Such an impact excavated down to depths of the body generating multiple fragments with complicated histories. These fragments reaccumulated into a gravitational aggregate and formed the parental meteoroid for the Chelyabinsk meteorite.

  16. Rutile is holding Nb and Ta in the mantle, negligible Nb and Ta in the core

    Science.gov (United States)

    McDonough, W. F.; Rudnick, R. L.

    2008-12-01

    Continental Crust has a significant depletion in Nb and Ta relative to La that has been attributed to convergent margin (arc) magmatism and greater retention of Nb and Ta in the mantle source. This depleted pattern is a consequence of the plotting order of elements, which has been established by the relative partitioning behavior of elements during MORB-OIB genesis. It is our hypothesis that rutile in subducting slabs or delaminated lower continental crust is the important phase causing Nb(Ta)-depletion in the continental crust, as well as lowering its Nb/Ta. Experimental studies reveal a range of Nb/Ta fractionation responses in residual rutile depending on temperature and phase relations(melting vs dehydration). Examples of rutile-bearing, refractory eclogites have been identified that serve as analog materials for residues of the continental crust. These rutiles have radiogenic Hf isotopes (Vervoort, unpubl. data), and thus are not recent precipitates from metasomatic melts, as has been recently suggested. What remains is to understand the total silicate Earth's mass balance. In this regard, it is worth noting that early Archean Barbarton komatiites possess chondritic La/Nb ratios, and Nb/Ta ~15, a value comparable to Allende CV3 chondrite. This observation is not consistent with the storage of Nb (or Ta) in the core and suggests that the silicate Earth controls the planetary budget of Nb and Ta. Constraints on the amount of Nb in the core must be evaluated by multi-element approaches, using ratios of refractory lithophile elements. Chondritic ratios for La/Nb and Nb/Ta are not defined simply as a single value with a restricted range and are not always constant, with examples of both negligible and distinct differences between groups of chondrites. The database for chondrites is still small for Nb and Ta.

  17. Chemical evidence for differentiation, evaporation and recondensation from silicate clasts in Gujba

    Science.gov (United States)

    Oulton, Jonathan; Humayun, Munir; Fedkin, Alexei; Grossman, Lawrence

    2016-03-01

    The silicate and metal clasts in CB chondrites have been inferred to form as condensates from an impact-generated vapor plume between a metal-rich body and a silicate body. A detailed study of the condensation of impact-generated vapor plumes showed that the range of CB silicate clast compositions could not be successfully explained without invoking a chemically differentiated target. Here, we report the most comprehensive elemental study yet performed on CB silicates with 32 silicate clasts from nine slices of Gujba analyzed by laser ablation inductively coupled plasma mass spectrometry for 53 elements. Like in other studies of CBs, the silicate clasts are either barred olivine (BO) or cryptocrystalline (CC) in texture. In major elements, the Gujba silicate clasts ranged from chondritic to refractory enriched. Refractory element abundances ranged from 2 to 10 × CI, with notable anomalies in Ba, Ce, Eu, and U abundances. The two most refractory-enriched BO clasts exhibited negative Ce anomalies and were depleted in U relative to Th, characteristic of volatilization residues, while other BO clasts and the CC clasts exhibited positive Ce anomalies with excess U (1-3 × CI), and Ba (1-6 × CI) anomalies indicating re-condensation of ultra-refractory element depleted vapor. The Rare Earth Elements (REE) also exhibit light REE (LREE) enrichment or depletion in several clasts with a range of (La/Sm)CI of 0.9-1.8. This variation in the LREE is essentially impossible to accomplish by processes involving vapor-liquid or vapor-solid exchange of REE, and appears to have been inherited from a differentiated target. The most distinctive evidence for inherited chemical differentiation is observed in highly refractory element (Sc, Zr, Nb, Hf, Ta, Th) systematics. The Gujba clasts exhibit fractionations in Nb/Ta that correlate positively with Zr/Hf and span the range known from lunar and Martian basalts, and exceed the range in Zr/Hf variation known from eucrites. Variations of

  18. 我国某些球粒陨石物质组成的初步研究

    Institute of Scientific and Technical Information of China (English)

    王道德; 欧阳自远

    1979-01-01

    Samples are avaibale for 27 stone meteorite fallings in China. 13 chondrites have been preliminary examined in terms of chemical and mineral compositions, cosmogenic nuclides, formation and exposure ages, impact effect and ehondrule structure. On the basis of chemical-petrological features these chondrites are classified into E4 (Qingzhen),H5 (Jilin, Cbangde, Shuangyang, Anlong, Xinyi, and Yangjiang), L4 (Renqiu, Junan,Heze. Rugao and Inner Mongolia)and LL5(Dongtai). E4 is characterized by high contents of iron and sulfur, with the former occurring mainly as Fe0 and FeS. From H5 through H5 to LL6 iron and nickel decrease gradually while FeO and the ratio of Fe silicate to total iron increase gradually, indicating a general inerease in the order E--H--L-LL in the extent of oxidation state at the time of formation. E4 consists mainly of enstatite and, to much less extent, free SiO2, but olivine is hardly to be found. The olivine propotions amount to 29.07, 41.98 and 51.36 percent in H5, L6 and LL5, respectively, with Fa increasing from 17 to 27 percent. Recrystallization has been noticed to different degrees in H4, H5, L5 and LL6 chondrites. The extent to which the original structure disappears and the boundaries of ohondroles become indistinct decreases from type 6 through type 5 to type 4, reflecting the different degrees of thermal metamorphism. Major minerals in the meteorites all exhibit signs of low to intermediate impact metamorphism. Specific activity, depth effect and orbit effect have also been measured on some chondritcs that fell in recent years and. some new information has been gained with respect to the orbit and source region for the meteorite parent bodies in space. This results show that the environment of formation of E group may be nearer to mars than O group. Chondrite of each chemical family has its own evolution history, and chondrites of different chemical families may have originated from parent bodies of different compositions. Or, owing to

  19. Where Did the Ureilite Parent Body Accrete? Constraints from Chemical and Isotopic Compositions

    Science.gov (United States)

    Goodrich, Cyrena; O'Brien, David P.

    2014-11-01

    Almahata Sitta and other polymict ureilites contain a remarkable diversity of materials, including EH, EL, OC, R- and CB chondrites, in addition to the dominant ureilitic material [1]. These materials represent at least 6 different parent asteroids and a wide range of chemical and isotopic environments in the early Solar System. To understand the origin of this diversity it is critical to know where (heliocentric distance) the ureilite parent body (UPB) accreted. The chemical and isotopic compositions of ureilite precursors (inferred from the compositions of ureilites) can provide clues. Lithophile element ratios such as Si/Mg and Mn/Mg [2,3], and deficits in neutron-rich Cr, Ti and Ni isotopes [3], indicate that ureilite precursors were similar to ordinary or enstatite chondrites (OC or EC), not carbonaceous chondrites (CC). In contrast, high carbon contents, carbon isotopes and oxygen isotopes suggest a genetic link to CC. This poses a conundrum considering the variation of asteroid types, which suggests that EC and OC dominate the inner asteroid belt and CC the outer belt. However, the CC-like oxygen isotopes of ureilites strongly suggest the effects of parent-body aqueous alteration [4,5], which clearly implies that the UPB accreted beyond the ice line. Lithophile element properties of ureilites compared with chondrites may not be a reliable indicator of location of accretion, because lithophile elements in chondrites are sited mainly in chondrules and the UPB accreted before most chondrules formed [6]. Ureilite Cr, Ti and Ni isotopes may indicate late introduction of the neutron rich isotopes of these elements to the CC-formation region [7]. We conclude that the UPB accreted in the outer belt, like CC. The UPB or one of its offspring must have migrated to the inner belt to acquire OC, EC and R-chondrite materials.[1] Horstmann M. & Bischoff A. [2014] Chemie der Erde 74, 149.[2] Goodrich C. [1999] MAPS 34, 109.[3] Warren P. [2011] GCA 46, 53.[4] Young E. [1999

  20. A combined diffusion and thermal modeling approach to determine peak temperatures of thermal metamorphism experienced by meteorites

    Science.gov (United States)

    Schwinger, Sabrina; Dohmen, Ralf; Schertl, Hans-Peter

    2016-10-01

    Carbonaceous chondrites are affected to different degrees by thermal and aqueous metamorphism on their parent bodies. However, the degree of alteration has been categorized mainly by relative scales and achieving quantitative information about metamorphic temperature by conventional mineral thermometry is problematic for low petrologic types. We have developed a general approach to estimate the metamorphic peak temperature experienced by type 3 chondrites from diffusion zoning in minerals, and have applied this approach to olivine in type I and type II chondrules of CO3 chondrites. To obtain metamorphic temperatures from diffusion zoning, we have combined diffusion modeling with thermal modeling of the meteorite parent body. The integrated diffusion coefficient over time (Γ) was identified as a useful parameter to quantify the extent of chemical change by diffusion occurring in a mineral during a given thermal history. Knowing the temperature dependence of the diffusion coefficient, Γ values can be calculated for each thermal history and be compared to the Γ values obtained from diffusion modeling. For thermal histories realistic for the parent body, Γ depends primarily on the metamorphic peak temperature, so that Γ values determined from diffusion profiles in meteorite minerals can be directly related to the metamorphic peak temperature. This general approach is relatively insensitive to uncertainties in the input parameters for the thermal model. We found that chemical zoning in type I and type II chondrule olivine of the CO chondrites Kainsaz and Lancé was largely influenced by solid state diffusion, which is evident from the observed correlation of zoning anisotropy with the crystallographic orientation. Chemical zoning in type II chondrule olivine is mainly igneous for CO chondrites of petrologic types up to at least 3.2 (Kainsaz) and was influenced only minor by diffusion during parent body metamorphism. Fe-Mg zoning in type II chondrule olivine and