Although pure metallic iron (i.e. that with an Fe content of greater than 99%) commonly occurs in achondrites, and within the returned soil from asteroids or the Lunar surface, it is rarely found in ordinary chondrites meteorites. Abundant nanophase iron particles (np-Fe) were identified in pyroxene glass, within the shock melt vein of Grove Mountains (GRV) 022115, which is an ordinary (L6) chondrite, with a shock stage determined as S5. The association of np-Fe-0, highly defective high pressure clinoenstatite (HP-CEn), silica glass, as well as vesicles, embedded in a pyroxene glass selvage within the shock melt vein in this meteorite suggests that these phases formed as the result of decomposition of the host pyroxene grain, a process induced by the shock event that affected GRV 022115. The reaction to account for this mineral breakdown can be written as: FeSiO3 -> Fe + SiO2 + 1/2O(2) up arrow (MgSiO3 remain in the HP-CEn). The pressure and temperature condition attending this reaction are estimated at 20-23 GPa and over 1800 degrees C, as indicated by the surrounded high-pressure mineral assemblage: ringwoodite, majorite, and magnesiowustite. This study provides evidence to the formation of np-Fe-0 derived from pyroxene, and HP-CEn quenched metastably in such shocked vein could preserve the metastable phase transitions history record. (C) 2019 Elsevier Ltd. All rights reserved. Publication name | GEOCHIMICA ET COSMOCHIMICA ACTA Volume: 272 Pages: 276-286 DOI: 10.1016/j.gca.2019.10.036 Published: MAR 1 2020 | Author(s) | Guo, Zhuang; Li, Yang; Liu, Shen; Xu, Huifang; Xie, Zhidong; Li, Shijie; Li, Xiongyao; Lin, Yangting; Coulson, Ian M.; Zhang, Mingming | Corresponding author(s) | LI Yang liyang@mail.gyig.ac.cn -Chinese Acad Sci, Ctr Lunar & Planetary Sci, Inst Geochem, Guiyang 550081, Peoples R China. LIU Shen liushen@nwu.edu.cn -Northwest Univ, State Key Lab Continental Dynam, Xian 710069, Peoples R China. -Northwest Univ, Dept Geol, Xian 710069, Peoples R China. | View here for the details
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