Origin and implications of troilite-orthopyroxene intergrowths in the brecciated diogenite Northwest Africa 7183
Origin and implications of troilite-orthopyroxene intergrowths in the brecciated diogenite Northwest Africa 7183
复制标题
西北非 7183 角砾状闪长岩中硫镁石-斜方辉石共生体的起源和意义
DOI：
10.1016/j.gca.2017.09.051
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发表时间：
2018
影响因子：
5
通讯作者：
Wang Ru-Cheng
中科院分区：
文献类型：
--
作者：
Zhang Ai-Cheng;Bu Yi-Fan;Pang Run-Lian;Sakamoto Naoya;Yurimoto Hisayoshi;Chen Li-Hui;Gao Jian-Feng;Du De-Hong;Wang Xiao-Lei;Wang Ru-Cheng
Troilite-orthopyroxene intergrowths are present as a common material in the brecciated diogenite Northwest Africa (NWA) 7183. In this study, we report on the petrographic, mineralogical, and rare earth element abundances of the troilite-orthopyroxene intergrowths to constrain their origin and assess their implications for the diverse petrogenesis of diogenites.Two groups of troilite-orthopyroxene intergrowths with various grain sizes and mineral chemistry have been observed in NWA 7183. One group of intergrowths contains fine-grained (<5 μm) olivine and chromite as inclusions in orthopyroxene (10–20 μm in size). The other group, in which orthopyroxene is more fine-grained (<10 μm in size), is closely associated with coarse irregular olivine grains. The orthopyroxene grains in both groups of troilite-orthopyroxene intergrowths are depleted in Cr, Al, Ti, and Ca compared with diogenitic orthopyroxene. Based on the texture and mineral chemistry, we suggest that the two groups of troilite-orthopyroxene intergrowths formed via reactions between diogenitic olivine and S-rich vapors, probably at different temperatures. The fact that some of the intergrowths are included in diogenitic lithic clasts indicates that the formation of the host diogenite should postdate the formation of the majority of troilite-orthopyroxene intergrowths. This relationship further implies that not all of the diogenites are cumulates that directly crystallized from the Vestan magma ocean. Instead, they probably originated from partial melting and recrystallization of magma ocean cumulates. The replacement of olivine by troilite and orthopyroxene intergrowths can partly explain why the expected olivine-rich lithologies were not detected at the two south pole impact basins on Vesta.
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影响因子：
5
作者：
A. Zhang;S. Itoh;N. Sakamoto;Rucheng Wang;H. Yurimoto
通讯作者：
A. Zhang;S. Itoh;N. Sakamoto;Rucheng Wang;H. Yurimoto
影响因子：
3.5
作者：
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G. Delpech;J. Lorand;M. Grégoire;J. Cottin;S. O’Reilly
影响因子：
3.5
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影响因子：
5
作者：
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通讯作者：
D. Mittlefehldt
影响因子：
2.2
作者：
K. Righter;M. Drake
通讯作者：
K. Righter;M. Drake