Petrology and geochemistry of Yamato 984028: a cumulate lherzolitic shergottite with affinities to Y 000027, Y 000047, and Y 000097
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概要
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We report the petrography, mineral and whole-rock chemistry (major-, trace-, and highly-siderophile element abundances, and osmium and oxygen isotope compositions) of a newly recognized lherzolitic shergottite, Yamato (Y) 984028. Oxygen isotopes (Δ17O = 0.218‰) confirm a martian origin for this meteorite. Three texturally distinctive internal zones and a partially devitrified fusion crust occur in the polished section of Y 984028 studied here. The zones include: 1) a poikilitic region with pyroxene enclosing olivine and chromite (Zone A); 2) a non-poikilitic zone with cumulate olivine, interstitial pyroxene, maskelynite and Ti-rich chromite (Zone B) and; 3) a monomict breccia (Zone C). The pyroxene oikocryst in Zone A is chemically zoned from Wo3–7En76–71 in the core region to Wo33–36En52–49 at the rim, and encloses more Mg-rich olivine (Fo74–70) in the core, as compared with olivines (Fo69–68) located at the oikocryst rim. Constraints from Fe–Mg partitioning between crystals and melt indicate that constituent minerals are not in equilibrium with the corresponding bulk-rock composition, implying that Y 984028 represents a cumulate. The whole-rock major- and trace-element compositions, and initial 187Os/188Os value (0.1281 ± 0.0002) of Y 984028 are similar to other lherzolitic shergottites and this sample is probably launch-paired with Y 793602, Y 000027, Y 000047, and Y 000097. The Os isotopic composition and highly-siderophile element (HSE) abundances of Y 984028 and other lherzolitic shergottites are consistent with derivation from a martian mantle source that evolved with chondritic Re/Os.
著者
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Amy J.V.
Planetary Geosciences Institute, Department of Earth & Planetary Sciences, University of Tennessee,
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Yang Liu1
Planetary Geosciences Institute, Department of Earth & Planetary Sciences, University of Tennessee,
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James M.D.
Department of Geology, University of Maryland, College Park, MD 20742, USA
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Igor S.
Department of Geology, University of Maryland, College Park, MD 20742, USA
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Douglas Rumble
Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA
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Harry Y.
Planetary Geosciences Institute, Department of Earth & Planetary Sciences, University of Tennessee,
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Richard J.
Department of Geology, University of Maryland, College Park, MD 20742, USA
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Lawrence A.
Planetary Geosciences Institute, Department of Earth & Planetary Sciences, University of Tennessee,
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James M.d.
Department Of Geology University Of Maryland College Park Md 20742 Usa
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Amy J.v.
Planetary Geosciences Institute Department Of Earth & Planetary Sciences University Of Tennessee
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Yang Liu1
Planetary Geosciences Institute Department Of Earth & Planetary Sciences University Of Tennessee
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Douglas Rumble
Geophysical Laboratory Carnegie Institution Of Washington Washington Dc 20015 Usa
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Yang Liu
Planetary Geosciences Institute, Department of Earth & Planetary Sciences, University of Tennessee,
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Yang Liu
Planetary Geosciences Institute Department Of Earth & Planetary Sciences University Of Tennessee
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Harry Y.
Planetary Geosciences Institute Department Of Earth & Planetary Sciences University Of Tennessee
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Richard J.
Department Of Geology University Of Maryland College Park Md 20742 Usa
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Lawrence A.
Planetary Geosciences Institute Department Of Earth & Planetary Sciences University Of Tennessee
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Igor S.
Department Of Geology University Of Maryland College Park Md 20742 Usa