气候变化领域集成服务门户(CCPortal): Recycling of ancient subduction-modified mantle domains in the Purang ophiolite (southwestern Tibet)

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DOI	10.1016/j.lithos.2016.06.025
	Recycling of ancient subduction-modified mantle domains in the Purang ophiolite (southwestern Tibet)
	Gong, Xiao-Han; Shi, Ren-Deng; Griffin, W. L.; Huang, Qi-Shuai; Xiong, Qing; Chen, Sheng-Sheng; Zhang, Ming; O'Reilly, Suzanne Y.
通讯作者	Gong, XH (通讯作者)
发表日期	2016
ISSN	0024-4937
EISSN	1872-6143
起始页码	11
结束页码	26
卷号	262
英文摘要	Ophiolites in the Indus-Yarlung Zangbo (IYZ) suture (southern Tibet) have been interpreted as remnants of the Neo-Tethyan lithosphere. However, the discovery of diamonds and super-reducing, ultra-high pressure (SuR-UHP) mineral assemblages (e.g., coesite after stishovite, olivine after wadsleyite, native metals, alloys, and moissanite) in some of these massifs and associated chromitites requires a re-evaluation of their origin and evolution. A new petrological and geochemical study of the Purang ophiolite in the western IYZ suture sheds new lights on these issues. The depleted harzburgites of the Purang massif have low modal contents of clinopyroxene (<2%), and high Cr# [100*Cr3+/(Cr3+ + Al3+)] in spinel (>40 similar to 70) and pyroxenes (>16 in orthopyroxene, and >20 in clinopyroxene), suggesting high degrees of melt extraction (>20%). These features are not consistent with formation in a (ultra-) slow-spreading mid-ocean ridge. These peridotites have high modal contents of orthopyroxene; this, and the extremely high Cr# of spinels in these peridotites, suggests modification in a subduction zone. The clinopyroxene-rich harzburgites and lherzolites contain rare spinel-pyroxene symplectites after garnet. Their clinopyroxenes have low MREE-to-HREE ratios ((Sm/Yb)(N) < 0.1) at relatively high HREE concentrations, and are Na-rich but Nd-poor. The relatively enrichment of Na but depletion of Nd in clinopyroxene cannot be explained by refertilization with MORB melts but are consistent with an origin from Na-rich subcontinental lithospheric mantle (SCLM). All lines of evidence suggest that these peridotites underwent initial melting in the stability field of garnet-fades peridotites, followed by additional melting in the spinel-facies mantle. Whole-rock Os isotopic compositions of the Purang peridotites give ancient T-RD model ages (up to 1.3 Ga), indicating that the formation of these ancient depletion residues predated the opening of Neo-Tethyan Ocean. These observations, together with recent studies on other IYZ peridotites, suggest that the Purang peridotites are genetically unrelated to the associated mafic crust. Instead, they represent ancient SCLM domains, initially formed beneath a continental margin, and then modified by subduction, before they were incorporated into the Neo-Tethyan ocean basin. This model is consistent with the deep-mantle-recycling model for the presence of SuR-UHP phases in the IYZ ophiolites. The infiltration of MORB melts through these ancient depleted peridotites during their final exhumation in a (ultra-) slow-spreading center may have refertilized them to produce the clinopyroxene-rich peridotites. (C) 2016 Elsevier B.V. All rights reserved.
关键词	YARLUNG-ZANGBO SUTURE OCEANIC UPPER-MANTLE MID-ATLANTIC RIDGE ULTRAHIGH-PRESSURE CHROMITITES SPINEL-PYROXENE SYMPLECTITE MELT-ROCK INTERACTION SUB-ARC MANTLE ABYSSAL PERIDOTITES TRACE-ELEMENT YUNGBWA OPHIOLITE
英文关键词	Purang ophiolite; Subcontinental lithospheric mantle; Mantle recycling; Indus-Yarlung Zangbo suture; Tibet
语种	英语
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
WOS类目	Geochemistry & Geophysics ; Mineralogy
WOS记录号	WOS:000384783500002
来源期刊	LITHOS
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/258804
推荐引用方式 GB/T 7714	Gong, Xiao-Han,Shi, Ren-Deng,Griffin, W. L.,et al. Recycling of ancient subduction-modified mantle domains in the Purang ophiolite (southwestern Tibet)[J]. 中国科学院青藏高原研究所,2016,262.
APA	Gong, Xiao-Han.,Shi, Ren-Deng.,Griffin, W. L..,Huang, Qi-Shuai.,Xiong, Qing.,...&O'Reilly, Suzanne Y..(2016).Recycling of ancient subduction-modified mantle domains in the Purang ophiolite (southwestern Tibet).LITHOS,262.
MLA	Gong, Xiao-Han,et al."Recycling of ancient subduction-modified mantle domains in the Purang ophiolite (southwestern Tibet)".LITHOS 262(2016).