中国科学院机构知识库网格
Chinese Academy of Sciences Institutional Repositories Grid
首页 机构 成果 学者
  
  1. CAS IR Grid
  2. 地质与地球物理研究所
  3. 中国科学院地质与地球物理研究所
  4. 中国科学院地球与行星物理重点实验室
Evidence for early impact on a hot differentiated planetesimal from Al-rich micro-inclusions in ungrouped achondrite Northwest Africa 7325

文献类型：期刊论文

作者Yang, Jing1; Zhan, Chi1; Miyahara, Masaaki2; Tan, Xu1; Gu, Lixin1; Lin, Yangting1,3
刊名GEOCHIMICA ET COSMOCHIMICA ACTA
出版日期2019-08-01
卷号258页码:310-335
ISSN号0016-7037
关键词NWA 7325 micro-inclusions impact melt hot planetesimal
DOI10.1016/j.gca.2019.03.010
英文摘要The ungrouped achondrite NWA 7325 is a cumulate olivine gabbro (Irving et al., 2013). It contains abundant and unique micro-inclusions of Ca-pyroxene (Bischoff et al., 2013) and spinel-like Al-Mg oxide (Goodrich et al., 2017) in plagioclase, indicating a remelting event induced either by impact (Goodrich et al., 2017) or by magma intrusion (Bischoff et al., 2013; Weber et al., 2016). In this work, a combined FIB-TEM study has been conducted on these micro-inclusions to address their petrogenesis and the related history of NWA 7325. TEM study revealed that micro-inclusions in the interiors of large plagioclase grains are Al-enriched spinel (Mg/Al atomic ratio: 0.03-0.4) with minor needle-like alpha-corundum, whereas those in the margins are predominantly Al-rich diopside (En(44.5-46.6)Fs(1.2-1.5)Wo(31.2-36.7)CaTs(17.6-22.4)) with minor forsterite (Fo(94.6-94.7)). The Mg/Al atomic ratios of the spinel micro-inclusions are negatively correlated with the distance away from the interface of plagioclase-pyroxene. Large plagioclase grains also exhibit a decrease in the Mg/Al atomic ratio from the rims to the cores. Based on the reaction texture at the interfaces of plagioclase-pyroxene, we infer that the Mg concentration gradient in large plagioclase grains could have resulted from Mg diffusion from the remelted rims of pyroxene into plagioclase. In addition, TEM observations showed that large plagioclase grains are not single crystals, but assemblages of submicron to micronsized crystals. The preservation of Mg concentration gradients, submicron-sized polycrystalline plagioclases, and the consistent presence of micro-inclusions within large plagioclase grains likely indicate complete remelting of plagioclase and partial remelting of pyroxene (only rims of pyroxene with plagioclase) followed by fast cooling. We propose that micro-inclusions of diopside, forsterite, Al-rich spinel and corundum crystallized from the melt, which developed a Mg concentration gradient during the remelting of NWA 7325. The heating temperatures of pyroxene and plagioclase in the remelting event were estimated to be 1274-1327 degrees C and >= 1530 degrees C, respectively. A subsequent cooling rate of similar to 500-650 degrees C/h at 1300 degrees C was found by fitting the measured Mg concentration gradient in large plagioclase grains with a Fick's second law model that incorporated the diffusion coefficients of Mg in plagioclase-melt. These results are better explained by a shock event; a magmatic intrusion process is ruled out. To achieve the coexistence of shock-induced high temperature (>= 1274 degrees C) in-situ melting and only undulatory extinction of forsterite grains, an ambient temperature of 1000-1100 degrees C in the surrounding, parent rock of NWA 7325 was required prior to impact. This work suggests a very early shock event when NWA 7325 was hot and buried in the crust of its parental planetesimal, which is a scenario consistent with its magma crystallization age (similar to 4.3 Ma after CAIs, e.g., Koefoed et al., 2016). This work also implies that impacts are a potential heat source for melting hot planetesimals in the early Solar System. (C) 2019 Elsevier Ltd. All rights reserved.
WOS关键词MARTIAN METEORITE ; TRACE-ELEMENTS ; SHOCK ; CRYSTALLIZATION ; CONSTRAINTS ; HISTORIES ; EVOLUTION ; DIFFUSION ; PETROLOGY ; CHROMIUM
资助项目National Natural Science Foundation of China[41603067] ; National Natural Science Foundation of China[41490631] ; National Natural Science Foundation of China[41490633] ; National Natural Science Foundation of China[41430105] ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences[QYZDJ-SSW-DQC001]
WOS研究方向Geochemistry & Geophysics
语种英语
出版者PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号WOS:000472708700019
资助机构National Natural Science Foundation of China ; National Natural Science Foundation of China ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences ; Key Research Program of Frontier Sciences, Chinese Academy of Sciences
源URL[http://ir.iggcas.ac.cn/handle/132A11/92522]  
专题地质与地球物理研究所_中国科学院地球与行星物理重点实验室
通讯作者Lin, Yangting
作者单位1.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Earth & Planetary Phys, Beijing 100029, Peoples R China
2.Hiroshima Univ, Grad Sch Sci, Dept Earth & Planetary Syst Sci, Hiroshima 7398526, Japan
3.Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100029, Peoples R China
推荐引用方式
GB/T 7714		 Yang, Jing,Zhan, Chi,Miyahara, Masaaki,et al. Evidence for early impact on a hot differentiated planetesimal from Al-rich micro-inclusions in ungrouped achondrite Northwest Africa 7325[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2019,258:310-335.
APA Yang, Jing,Zhan, Chi,Miyahara, Masaaki,Tan, Xu,Gu, Lixin,&Lin, Yangting.(2019).Evidence for early impact on a hot differentiated planetesimal from Al-rich micro-inclusions in ungrouped achondrite Northwest Africa 7325.GEOCHIMICA ET COSMOCHIMICA ACTA,258,310-335.
MLA Yang, Jing,et al."Evidence for early impact on a hot differentiated planetesimal from Al-rich micro-inclusions in ungrouped achondrite Northwest Africa 7325".GEOCHIMICA ET COSMOCHIMICA ACTA 258(2019):310-335.

入库方式： OAI收割

来源：地质与地球物理研究所

浏览0
下载0
收藏0
其他版本

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。