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DOI	10.1016/j.precamres.2012.06.016
	Archean mantle contributes to the genesis of chromitite in the Palaeozoic Sartohay ophiolite, Asiatic Orogenic Belt, northwestern China
	Shi, Rendeng; Griffin, William L.; O'Reilly, Suzanne Y.; Zhou, Meifu; Zhao, Guochun; Huang, Qishuai; Zhang, Xiaoran; Ding, Binghua; Ding, Lin
通讯作者	Shi, RD (通讯作者)
发表日期	2012
ISSN	0301-9268
EISSN	1872-7433
起始页码	87
结束页码	94
卷号	216
英文摘要	Podiform chromitites in ophiolite usually are interpreted as the crystallization products of mafic magmas, contemporaneous with the generation of the ophiolite at mid-oceanic ridges or back-arc spreading centres. However, the real ages of the chromitites can rarely be determined directly, because their chemistry provides few opportunities for geochronology. Here we employ the Re-187-Os-188 decay system (N-TIMS) to date the chromitite and a cross-cutting troctolite in the Sartohay ophiolite, northwestern China, and we have dated zircons separated from the troctolite by SHRIMP U-Pb methods. Inherited zircons from the troctolite yield a lower intercept age of 0.48 +/- 0.08 Ga and an upper intercept age of 2.28 +/- 0.11 Ga; two concordant grains give ages >2.4 Ga. Whole-rock Re-Os data for the troctolites and chromites plot between 2.45 Ga and 0.43 Ga reference isochrons. Plots of T-MA VS Os-187/Os-188 suggest mixing between ultra-depleted chromitite and suprachondritic troctolite, mainly affecting the Os-187/Os-188 of the troctolites; subsets of troctolite samples scatter around reference isochrons with ages of 0.4-0.5 Ga. The zircon data and the Re/Os data are consistent with published Sm-Nd evidence that the troctolites, and hence the Sartohay ophiolite, were formed in Palaeozoic time. However, the Os-187/Os-188 compositions of the chromites (0.1109 +/- 4 to 0.1249 +/- 5), give Neo-Proterozoic to Paleo-Archean model ages (T-MA = 0.8-3.5 Ga), indicating extraction from the primitive mantle as early as 3.5 Ga, some 3 Ga before the formation of the Sartohay ophiolite. A Re-Os apparent isochron age (2.45 Ga), the old T-MA model ages and the ancient zircon ages (>2.4 Ga) all are consistent with part formation of the Sartohay chromitite in Archean time, and then reworked in the Palaeozoic time. We suggest that a volume of early Archean depleted mantle remained within the Siberian lithospheric mantle for 2.5-3.0 Ga; it later became portions of the mantle wedge above the Paleozoic subduction zone of the Paleo-Asian Ocean, and ultimately was incorporated into the overthrust ophiolite. (C) 2012 Elsevier B.V. All rights reserved.
关键词	RE-OS SYSTEMATICS SUBCONTINENTAL LITHOSPHERIC MANTLE OSMIUM ISOTOPIC COMPOSITION PODIFORM CHROMITITES PERIDOTITE XENOLITHS SIBERIAN CRATON SR ISOTOPE BENEATH ND EVOLUTION
英文关键词	Chromitite; Sartohay ophiolite; Re-Os isotopes; Archean; Paleo-Asian Ocean
语种	英语
WOS研究方向	Geology
WOS类目	Geosciences, Multidisciplinary
WOS记录号	WOS:000308784900004
来源期刊	PRECAMBRIAN RESEARCH
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/258067
推荐引用方式 GB/T 7714	Shi, Rendeng,Griffin, William L.,O'Reilly, Suzanne Y.,et al. Archean mantle contributes to the genesis of chromitite in the Palaeozoic Sartohay ophiolite, Asiatic Orogenic Belt, northwestern China[J]. 中国科学院青藏高原研究所,2012,216.
APA	Shi, Rendeng.,Griffin, William L..,O'Reilly, Suzanne Y..,Zhou, Meifu.,Zhao, Guochun.,...&Ding, Lin.(2012).Archean mantle contributes to the genesis of chromitite in the Palaeozoic Sartohay ophiolite, Asiatic Orogenic Belt, northwestern China.PRECAMBRIAN RESEARCH,216.
MLA	Shi, Rendeng,et al."Archean mantle contributes to the genesis of chromitite in the Palaeozoic Sartohay ophiolite, Asiatic Orogenic Belt, northwestern China".PRECAMBRIAN RESEARCH 216(2012).