气候变化领域集成服务门户(CCPortal): Genesis of chromian spinets in the Purang mantle peridotites of the Yarlung-Zangbo Suture Zone, Tibet

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DOI	10.18654/1000-0569/2020.02.08
	Genesis of chromian spinets in the Purang mantle peridotites of the Yarlung-Zangbo Suture Zone, Tibet
	Bin, Zhao; Gong XiaoHan; Huang QiShuai; Shi RenDeng
通讯作者	Shi, RD (通讯作者)
发表日期	2020
ISSN	1000-0569
EISSN	2095-8927
起始页码	455
结束页码	468
卷号	36 期号:2
英文摘要	The Purang mantle peridotites, located in the western Yarlung Zangbo Suture Zone, are mainly composed of harzburgite, Cpx-harzburgite and a small amount of lherzolite and dunite. As an accessory mineral in the mantle peridotites, the chromian spinet can be used to be an important petrological indicator. Based on geological survey, the chromian spinets from Purang mantle peridotites are divided into three categories through lithographic observation in detail, electron probe, elemental distribution mapping of spinets and Electron Back Scattered Diffraction ( EBSD) analysis. Type I chromian spinets are euhedral crystal with a small size ( < 100 mu m) , which are distributed in large particles of orthopyroxenes or between olivines and pyroxenes. With the character of high Cr-# ( > 0. 6 ) and low Mg-# (0. 43 similar to 0. 57) , they were caused by boninitic melt metasomatism after partial melting. Type II chromian spinets show the characters of subhedral-irregular crystal and large particle size (>100 mu m). The type II spinets with medium Cr-# (0. 17 similar to 0. 42) and high Mg-#(0. 63 similar to 0. 77) were shaped by partial melting of the mantle. Type III spinets that show the characteristics of low Cr-# (0. 17 similar to 0. 28) and high Mg-# (0. 67 similar to 0. 77) are part of symplectite (rod-shaped, vermicular spinets closely associated with pyroxenes) , which form crystal structure with a large range in particle size. EBSD analysis for the constituent minerals of the symplectite shows similar Crystallographic Preferred Orientation (CPO) , which suggests that they represent the decomposition products of a precursor mineral. The similarity character of REE distribution between clinopyroxenes in symplectite and garnets from continental lithospheric mantle xenolith suggests that both the spinets and pyroxenes in symplectite were decomposed by high-pressure garnet ( majorite) which show the character of ancient sub-continental lithospheric mantle. As a result, it is speculated that the process of garnet degeneration, partial melting and melt permeation occurred in the upwelling process of the Purang mantle peridotites from the depth of garnet facies to spinet facies. The formation of the rock may undergo the continental rift stage in the early Wilson Cycle. The body of the rock underwent low degree of partial melting as the Mid-Ocean-Ridge ( MOR) environment while part of the rock was partially affected by silica-rich and magnesium-rich boninitic melts.
关键词	SOUTHERN TIBET PETROGENETIC INDICATOR LUOBUSA OPHIOLITE DONGBO OPHIOLITE VOLCANIC-ROCKS WESTERN PART ABYSSAL ORIGIN GEOCHEMISTRY LHERZOLITE
英文关键词	Chromian spinel; Partial melting; Melt metasomatism; Decomposition of garnet; Purang mantle peridotites
语种	英语
WOS研究方向	Geology
WOS类目	Geology
WOS记录号	WOS:000533618000008
来源期刊	ACTA PETROLOGICA SINICA
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/259894
推荐引用方式 GB/T 7714	Bin, Zhao,Gong XiaoHan,Huang QiShuai,et al. Genesis of chromian spinets in the Purang mantle peridotites of the Yarlung-Zangbo Suture Zone, Tibet[J]. 中国科学院青藏高原研究所,2020,36(2).
APA	Bin, Zhao,Gong XiaoHan,Huang QiShuai,&Shi RenDeng.(2020).Genesis of chromian spinets in the Purang mantle peridotites of the Yarlung-Zangbo Suture Zone, Tibet.ACTA PETROLOGICA SINICA,36(2).
MLA	Bin, Zhao,et al."Genesis of chromian spinets in the Purang mantle peridotites of the Yarlung-Zangbo Suture Zone, Tibet".ACTA PETROLOGICA SINICA 36.2(2020).