THE PORTALES VALLEY METEORITE BRECCIA: EVIDENCE FOR IMPACT-INDUCED MELTING AND METAMORPHISM OF AN ORDINARY CHONDRITE
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dc.contributor.author | Rubin A.E. | |
dc.contributor.author | Ulff-Moller F. | |
dc.contributor.author | Wasson J.T. | |
dc.contributor.author | Carlson W.D. | |
dc.date.accessioned | 2021-02-10T01:44:58Z | |
dc.date.available | 2021-02-10T01:44:58Z | |
dc.date.issued | 2001 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=548209 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 2001, 65, 2, 323-342 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/24582 | |
dc.description.abstract | The Portales Valley H-chondrite fall is an annealed impact-melt breccia with coarse metal interstitial to angular and subrounded silicate clasts. The large metal-rich regions exhibit a Widmanstatten structure and contain very little troilite. We were able to examine a 16.5 kg metal-rich specimen of Portales Valley. Silicates contain numerous flecks of metallic Cu and curvilinear trails of tiny metallic Fe-Ni blebs, characteristic of shocked and annealed chondrites. One silicate clast appears to have experienced little (<10%) or no melting; it is essentially identical to normal H6 chondrites. Other clasts are finer grained and have a low abundance of recognizable relict chondrules; they are significantly enriched in troilite and depleted in metallic Fe-Ni relative to typical H chondrites. Their low metal abundance indicates that they are not simply ultra-recrystallized H6 chondrites. If the silicates in these clasts started off as normal H-chondrite material and were recrystallized to the same extent as the progenitor of the H6-like clast, then their low modal abundance of chondrules indicates that they experienced significant crushing and/or impact melting. We infer that most of the metal and troilite was lost from these silicate clasts during impact melting; it appears that troilite was reintroduced into the silicates, perhaps by an S2-rich vapor (that formed FeS by reacting with Fe vapor or residual metal). Portales Valley probably formed on a low-density, porous H-chondrite asteroid by a high-energy impact event that caused crushing and melting; the target material was buried deeply enough to undergo slow cooling. Meteorites that appear to have formed, at least in part, by analogous processes include IIE-an Netschaevo and EL6 Blithfield. | |
dc.title | THE PORTALES VALLEY METEORITE BRECCIA: EVIDENCE FOR IMPACT-INDUCED MELTING AND METAMORPHISM OF AN ORDINARY CHONDRITE | |
dc.type | Статья |
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