Cooling rates in the shock veins of chondrites: constraints on the (Mg, Fe)2SiO4 polymorph transformations |
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| Authors: | Ming Chen Xiande Xie A El Goresy B Wopenka T G Sharp |
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| Institution: | (1) Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou, China;(2) Max-Planck-Institutfür Kernphysik, 69029 Heidelberg, Germany;(3) Department of Earth and Planetary Sciences, Washington University, M063130 St.Louis, USA;(4) Department of Geology, Arizona State University, 85287-1404 Tempe, AZ, USA |
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| Abstract: | The occurrence of γ-phase, a high-pressure polymorph of olivine (α-phase), in the shock veins of Sixiangkou chondrite was
due to a greater cooling rate (> 10 000°C·s-1) in the veins. Because γ-phase partially reverted to β-phase and no back-transformation from β-phase to α-phase took place,
the shock veins of Peace River chondrite with a cooling rate of 1 000–2 000δC·s-1 contain a great amount of β-phase. In the shock veins of Mbale chondrite with a cooling rate of <500°C·s-1, the majority of γ-phase reverted to α-phase. The heat dissipation in shock veins took place after a stage of shock compression
of chondrite parent body, and the parent body was broken into fragmental pieces. Cooling rate in the shock veins constrained
the back-transformations of (Mg, Fe)2SiO4 high-pressure polymorphs.
Project of Chen and Xie supported by the National Natural Science Foundation of China (Grant No. 496720981, Natural Science
Foundation of Guangdong Province (Grant No. 960500), and the Science Foundation of Academia Sinica for the returned scholars. |
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| Keywords: | chondrite shock vein (Mg Fe)2SiO4 polymorph transformation cooling rate |
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