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Allende Meteorite

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George R Rossman – 1st expert on this subject based on the ideXlab platform

  • Allendeite sc4zr3o12 and hexamolybdenum mo ru fe two new minerals from an ultrarefractory inclusion from the Allende Meteorite
    American Mineralogist, 2014
    Co-Authors: John R Beckett, George R Rossman

    Abstract:

    During a nanomineralogy investigation of the Allende Meteorite with analytical scanning electron microscopy, two new minerals were discovered; both occur as micro- to nano-crystals in an ultrarefractory inclusion, ACM-1. They are Allendeite, Sc_4Zr_3O_(12), a new Sc- and Zr-rich oxide; and hexamolybdenum (Mo,Ru,Fe,Ir,Os), a Mo-dominant alloy. Allendeite is trigonal, R3, ɑ = 9.396, c = 8.720, V = 666.7 A^3, and Z = 3, with a calculated density of 4.84 g/cm^3 via the previously described structure and our observed chemistry. Hexamolybdenum is hexagonal, P6_3/mmc, ɑ = 2.7506, c = 4.4318 A, V = 29.04 A^3, and Z = 2, with a calculated density of 11.90 g/cm^3 via the known structure and our observed chemistry. Allendeite is named after the Allende Meteorite. The name hexamolybdenum refers to the symmetry (primitive hexagonal) and composition (Mo-rich). The two minerals reflect conditions during early stages of the formation of the Solar System. Allendeite may have been an important ultrarefractory carrier phase linking Zr-,Sc-oxides to the more common Sc-,Zr-enriched pyroxenes in Ca-Al-rich inclusions. Hexamolybdenum is part of a continuum of high-temperature alloys in Meteorites supplying a link between Os- and/or Ru-rich and Fe-rich meteoritic alloys. It may be a derivative of the former and a precursor of the latter.

  • grossmanite cati3 alsio6 a new pyroxene from the Allende Meteorite
    American Mineralogist, 2009
    Co-Authors: George R Rossman

    Abstract:

    Grossmanite, Ca(Ti3+,Mg,Ti4+)AlSiO6 with an end-member formula CaTi3+AlSiO6, is a new member of the Ca clinopyroxene group, where the trivalent cations are dominant in the M1 site with Ti3+ being the dominant trivalent cation. It occurs as micrometer-sized crystals along with spinel and perovskite in a melilite host in Ca-, Al-rich refractory inclusions from the Allende Meteorite. The mean chemical composition determined by electron microprobe analysis of the type material is (wt%) SiO2 27.99, Al2O3 24.71, CaO 24.58, Ti2O3 10.91, TiO2 6.68, MgO 4.45, Sc2O3 0.43, V2O3 0.19, ZrO2 0.13, FeO 0.08, Cr2O3 0.03, sum 100.20. Its empirical formula calculated on the basis of 6 O atoms is Ca1.00[(Ti0.353+Al0.18Sc0.01V0.013+)∑0.55Mg0.25Ti0.194+]∑1.00(Si1.07Al0.93)∑2.00O6. Grossmanite is monoclinic, C 2/ c; a = 9.80 A, b = 8.85 A, c = 5.36 A, β = 105.62°, V = 447.70 A3, and Z = 4. Its electron back-scatter diffraction pattern is an excellent match to that of Ti3+-rich pyroxene with the C 2/ c structure. The five strongest calculated X-ray powder diffraction lines are [ d spacing in A, ( I ), hkl ] 2.996 (100) (221), 2.964 (31) (310), 2.581 (42) (002), 2.600 (28) (131), 2.535 (47) (221). The name is for Lawrence Grossman, a cosmochemist at the University of Chicago.

  • Grossmanite, CaTi3+AlSiO6, a new pyroxene from the Allende Meteorite
    American Mineralogist, 2009
    Co-Authors: Chi Ma, George R Rossman

    Abstract:

    Grossmanite, Ca(Ti3+,Mg,Ti4+)AlSiO6 with an end-member formula CaTi3+AlSiO6, is a new member of the Ca clinopyroxene group, where the trivalent cations are dominant in the M1 site with Ti3+ being the dominant trivalent cation. It occurs as micrometer-sized crystals along with spinel and perovskite in a melilite host in Ca-, Al-rich refractory inclusions from the Allende Meteorite. The mean chemical composition determined by electron microprobe analysis of the type material is (wt%) SiO2 27.99, Al2O3 24.71, CaO 24.58, Ti2O3 10.91, TiO2 6.68, MgO 4.45, Sc2O3 0.43, V2O3 0.19, ZrO2 0.13, FeO 0.08, Cr2O3 0.03, sum 100.20. Its empirical formula calculated on the basis of 6 O atoms is Ca1.00[(Ti0.353+Al0.18Sc0.01V0.013+)∑0.55Mg0.25Ti0.194+]∑1.00(Si1.07Al0.93)∑2.00O6. Grossmanite is monoclinic, C 2/ c; a = 9.80 A, b = 8.85 A, c = 5.36 A, β = 105.62°, V = 447.70 A3, and Z = 4. Its electron back-scatter diffraction pattern is an excellent match to that of Ti3+-rich pyroxene with the C 2/ c structure. The five strongest calculated X-ray powder diffraction lines are [ d spacing in A, ( I ), hkl ] 2.996 (100) (221), 2.964 (31) (310), 2.581 (42) (002), 2.600 (28) (131), 2.535 (47) (221). The name is for Lawrence Grossman, a cosmochemist at the University of Chicago.

Junichi Matsuda – 2nd expert on this subject based on the ideXlab platform

  • an attempt to characterize phase q noble gas raman spectroscopy and transmission electron microscopy in residues prepared from the Allende Meteorite
    Geochimica et Cosmochimica Acta, 2010
    Co-Authors: Junichi Matsuda, Sachiko Amari, Kazuhiko Morishita, Masayuki Nara, Hidetomo Tsukamoto, Chie Miyakawa, Tetsuya Uchiyama, Seiji Takeda

    Abstract:

    We have prepared a HF–HCl residue and its oxidized residue of the Allende Meteorite and have measured the elemental concentrations and the isotopic compositions of noble gases. In the HF–HCl reside, noble gases are enriched in colloidal fraction compared to the non-colloidal fraction by a factor of 2–4. The heavy noble gases were evidently lost after the oxidization, indicating that phase Q (carrier of planetary heavy noble gases) was removed by the oxidation. The Raman spectroscopic parameters show that the colloidal fraction of the HF–HCl residue is more amorphous compared to the non-colloidal fraction. As the ion irradiation converts carbon into a more amorphous form, our result indicates that the “plasma model” is more plausible than the “labyrinth model” as the origin of phase Q. TEM (Transmission Electron Microscope) observations also show such a trace of ion irradiation. While the TEM observations did not show any large difference between the HF–HCl residue and its oxidized residue, the Raman spectroscopic parameters changed discretely resulting from the oxidization. This observation indicates that the oxidization not only dissolved and removed oxidized carbon, but also changed the carbon structure itself to a more amorphous (disordered) state. The Raman spectroscopic results indicate the possibility that release of Q-gas during oxidation is not accompanied by mass loss and that the release of Q-gas simply resulted from rearrangement of carbon structure during oxidation.

  • raman spectroscopic study of the noble gas carrier q in the Allende Meteorite
    Geochemical Journal, 2009
    Co-Authors: Junichi Matsuda, Kazuhiko Morishita, Masayuki Nara, Sachiko Amari

    Abstract:

    We report Raman spectroscopic results of four density-separated fractions of a floating fraction (material similar to HF-HCl residues enriched in heavy noble gases) of the Allende Meteorite. The Raman analyses were performed at two laser powers of 0.5 mW and 2-6 mW with the excitation wavelength of 532 nm. The typical Raman spectra of carbon were observed for all the samples, but these carbonaceous materials were very sensitive to the laser power at the analysis. The Raman parameters except for the intensity ratio of D band and G band are similar in all the fractions at the low laser power, but they changed at the high laser power in a different manner, probably due to the different degree of laser-induced heating. Our findings are that phase Q (the carrier of noble gas of the normal isotopic composition in Meteorites) is enriched in the graphitic carbon having larger domain size compared to the major carbon in Allende and that this carbon is most affected by the laser heating.

  • an attempt to separate q from the Allende Meteorite by physical methods
    Geochimica et Cosmochimica Acta, 2003
    Co-Authors: Sachiko Amari, Shiho Zaizen, Junichi Matsuda

    Abstract:

    Abstract In order to characterize the planetary noble gas carrier Q, we separated a Q-rich floating fraction from the Allende Meteorite into ten fractions by a combination of colloidal and density separations. All five noble gases in the separated fractions were analyzed by pyrolysis in 600 and 1600°C temperature steps. Half of Q in the floating fraction is concentrated in the fraction C1-8D with the density of 1.65 ± 0.04 g/cm 3 . All the separated fractions show similar isotopic ratios except for 40 Ar/ 36 Ar ratios. C1-8D has the lowest 38 Ar/ 36 Ar and 40 Ar/ 36 Ar ratios (0.18784 ± 0.00020 and 4.36 ± 0.15, respectively) in the 1600°C fraction, confirming that the fraction is enriched in Q. Most grains in C1-8D are carbonaceous with small amounts of F and O. These results imply either that the density of Q is 1.65 ± 0.04 g/cm 3 or that Q preferentially sticks to matter of that density. All the separates have similar Q to diamond ratios, indicating that Q and diamond are closely associated.

Edward D Young – 3rd expert on this subject based on the ideXlab platform

  • mg isotope heterogeneity in the Allende Meteorite measured by uv laser ablation mc icpms and comparisons with o isotopes
    Geochimica et Cosmochimica Acta, 2002
    Co-Authors: Edward D Young, Albert Galy, Nick S Belshaw

    Abstract:

    First results from a new UV laser ablation MC-ICPMS method for measuring Mg isotope ratios in situ in meteoritical materials show that there are mass-dependent variations in 25 Mg and 26 Mg up to 1.5 ‰ per amu in chondrules and 0.3‰ per amu in a CAI from the Allende Meteorite. In both cases the mass-dependent fractionation is associated with alteration. Comparisons with laser ablation O isotope data indicate that incorporation of pre-existing grains of forsterite with distinct Mg and O isotopic compositions and post-formation alteration both contributed to the variability in Mg isotope ratios in the chondrules, resulting in a correlation between high 25 Mg and low 17 O. The laser ablation analyses of the CAI show that high-precision determinations of both 25 Mg and 26 Mg can be used to discriminate features of the 26 Al- 26 Mg isotope system that are relevant to chronology from those that result from element mobility. Copyright © 2002 Elsevier Science Ltd

  • uv laser ablation and irm gcms microanalysis of 18o 16o and 17o 16o with application to a calcium aluminium rich inclusion from the Allende Meteorite
    Geochimica et Cosmochimica Acta, 1998
    Co-Authors: Edward D Young, David W Coutts, D Kapitan

    Abstract:

    Abstract Analyses of 18O/16O and 17O/16O in silicate and oxide minerals by UV laser ablation of 100 × 80 × 50 μm sample pits combined with irm-GCMS yield precision and accuracy similar to that of conventional methods. This represents a 100-fold reduction in minimum size relative to other fluorination methods based on gas-source mass spectrometry and enables high-precision in-situ intracrystalline analysis of silicate minerals. Analyses of almandine, forsterite, and schorl of known isotopic compositions indicate an analytical precision of ±0.3‰ (1σ) in δ18O and ±0.4 in δ17O with an accuracy of similar magnitude. Application to meteoritic samples is demonstrated by in-situ analysis of pyroxene and melilite from a type B CAI inclusion from the Allende Meteorite. The CAI data adhere to the carbonaceous chondrite anhydrous mineral line defined by conventional macroscopic fluorination methods and demonstrate that non-mass dependent differences of 1‰ amu−1 are discernible. The unique combination of analytical and spatial resolution afforded by the new UV laser microprobe will allow high-precision mapping of the distribution of anomalous oxygen in minerals from calcium-aluminum-rich inclusions on a previously unattainable scale.

  • UV laser ablation and irm-GCMS microanalysis of 18O/16O and 17O/16O with application to a calcium-aluminium-rich inclusion from the Allende Meteorite
    Geochimica et Cosmochimica Acta, 1998
    Co-Authors: Edward D Young, David W Coutts, D Kapitan

    Abstract:

    Abstract Analyses of 18O/16O and 17O/16O in silicate and oxide minerals by UV laser ablation of 100 × 80 × 50 μm sample pits combined with irm-GCMS yield precision and accuracy similar to that of conventional methods. This represents a 100-fold reduction in minimum size relative to other fluorination methods based on gas-source mass spectrometry and enables high-precision in-situ intracrystalline analysis of silicate minerals. Analyses of almandine, forsterite, and schorl of known isotopic compositions indicate an analytical precision of ±0.3‰ (1σ) in δ18O and ±0.4 in δ17O with an accuracy of similar magnitude. Application to meteoritic samples is demonstrated by in-situ analysis of pyroxene and melilite from a type B CAI inclusion from the Allende Meteorite. The CAI data adhere to the carbonaceous chondrite anhydrous mineral line defined by conventional macroscopic fluorination methods and demonstrate that non-mass dependent differences of 1‰ amu−1 are discernible. The unique combination of analytical and spatial resolution afforded by the new UV laser microprobe will allow high-precision mapping of the distribution of anomalous oxygen in minerals from calcium-aluminum-rich inclusions on a previously unattainable scale.