Redistribution of elements in the heavily shocked Yanzhuang chondrite

Abstract

Redistribution of elements in the heavily shocked Yanzhuang chondriteAbstract-Compositions of metal, sulfide, olivine, pyroxene, and plagioclase/plagioclase glass were studied for the melted and unmelted parts of the heavily shocked H6(S6) chondrite-Yanzhuang. We found that the partitioning of some trace elements significantly changed between the 2 parts; compared with the corresponding minerals in the unmelted part, Ga is enriched in the metal, Co, Cr, and Zn are enriched in the sulfide, Cr is enriched in olivine and pyroxene, and Ti is enriched in the plagioclase glass of the melt pocket. These detailed studies of the mineral phases put constraints on 3 important parameters (temperature, pressure, and duration) associated with the post-shock melting process. The coexistence of melted and unmelted olivine in the melt pocket of Yanzhuang implies a peak temperature after shock that approaches the melting point of olivine. The lack of Ni in the olivine crystallized from a melt suggests crystallization of olivine at pressures below 10 kbar. The resetting of Ga partitioning between metal and silicate in the melt pocket indicates that the interval from the peak temperature after shock to the crystallization of metal-sulfide and plagioclase glass in the melted part of Yanzhuang is longer than 500 sec.

Eutectic metal + troilite + Fe‐Mn‐Na phosphate + Al‐free chromite assemblage in shock‐produced chondritic melt of the Yanzhuang chondrite

“…The Yanzhuang meteorite is classified as petrological type H6 chondrite, and considered to be one of the most heavily shocked and severely reheated chondrites described so far (Xie et al. ; Begemann et al (); Chen ; Kong and Xie ; Xie et al. ).…”

“…Some of the inclusions are elongated (Xie et al. ; Chen and Xie ; Kong and Xie ). The cooling rates during the solidification of dendrites were estimated as 6–30 °C s −1 in the interval 950–1400 °C (Chen et al.…”

“…The Yanzhuang meteorite is classified as petrological type H6 chondrite, and considered to be one of the most heavily shocked and severely reheated chondrites described so far (Xie et al 1991;Begemann et al (1992) ;Chen 1992;Kong and Xie 2003;Xie et al 2011). The meteorite consists of a highly deformed chondritic host and many shock-induced melt veins and melt pockets ( Fig.…”

“…, ; Leroux et al. ; Kong and Xie ). The cooling rates deduced from the structures of metal dendrites in the shock‐induced melts of chondrites range from 0.1 to 5000 °C s −1 (Scott ).…”

“…Metal and sulfide phases in the chondritic melt were completely molten and occur as rapidly solidified metal-troilite eutectic with dendritic or cellular texture, in which metallic dendrites were enclosed in a troilite groundmass (Scott 1982;Rubin 1985;Chen et al 1995aChen et al , 1995b. The investigation of textures, compositions, and microstructures in the metal-troilite eutectic can be used to construct the postshock thermal histories of chondritic meteorites (Begemann and Wlotzka 1969;Taylor and Heymann 1971;Smith and Goldstein 1977;Scott 1982;Rubin 1985;Chen and Xie 1995;Chen et al 1995aChen et al , 1995bLeroux et al 2000;Kong and Xie 2003). The cooling rates deduced from the structures of metal dendrites in the shock-induced melts of chondrites range from 0.1 to 5000°C s À1 (Scott 1982).…”