Formation of HP-LT rocks and their tectonic implications in the western Tianshan Orogen, NW China: geochemical and age constraints

	Formation of HP-LT rocks and their tectonic implications in the western Tianshan Orogen, NW China: geochemical and age constraints
	Gao, J ; Klemd, R
刊名	LITHOS
	2003
卷号	66 期号:1-2 页码:1-22
关键词	HP-LT rocks chemical composition Sm-Nd isochron Ar-40/Ar-39 plateau age Tianshan
ISSN号	0024-4937
文献子类	Article
英文摘要	The Western Tianshan high-pressure/low-temperature metamorphic belt in northwestern China formed within a Paleozoic accretionary wedge on the south side of the Yili-Central Tianshan plate. It comprises various lithologies, including mafic metavolcanic rocks, metavolcaniclastic rocks, metagreywacke, marble and serpentinite. The metavolcanics comprise eclogite, omphacitite, epidosite and blueschist. The trace and rare-earth element characteristics of these rocks indicate MORB to OIB affinities suggesting a seamount-like setting for the protoliths of these rocks. The epsilon(Nd) value of the eclogite (+8.9) indicates that the protolith was derived from a long-term depleted mantle, i.e. an N-MORB source, supporting the trace and rare-earth element characteristics of these samples. Sm-Nd isochron dating of 343 +/- 44 Ma (Omp-Gln-Grt-WR) and an age of 346 +/- 3 Ma (Grt-Gln) were determined using an eclogite boudin within blueschist. A well-defined Ar-40/Ar-39 plateau age of 344 +/- 1 Ma was obtained for crossite from an omphacite-phengite-bearing blueschist and is concordant with the Sm-Nd isochron age for the eclogite, suggesting that neither argon loss nor excess argon affected the crossite. A well-defined Ar-40/Ar-39 plateau age of 331 +/- 2 Ma was determined for phengite from the same sample. The high-pressure metamorphic rocks were formed by the B-type subduction of a Paleozoic 'South Tianshan Ocean' about 344 Ma ago. They were, however, exhumed to higher crustal levels during the collision of the Tarim and Yili-Central Tianshan plates about 331 Ma ago, similar to an 'Alpine-type' tectonic regime. (C) 2002 Elsevier Science B.V All rights reserved.
WOS关键词	HIGH-PRESSURE METAMORPHISM ; ECLOGITE-FACIES ROCKS ; NORTHWESTERN CHINA ; EXCESS ARGON ; RB-SR ; SOUTH TIANSHAN ; OCEANIC-CRUST ; CENTRAL-ASIA ; TIEN-SHAN ; SM-ND
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000180902400001
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/78359]
专题	中国科学院地质与地球物理研究所
通讯作者	Gao, J
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Mineral Resources, Beijing 100029, Peoples R China 2.Univ Wurzburg, Mineralog Inst, D-97074 Wurzburg, Germany
推荐引用方式 GB/T 7714	Gao, J,Klemd, R. Formation of HP-LT rocks and their tectonic implications in the western Tianshan Orogen, NW China: geochemical and age constraints[J]. LITHOS,2003,66(1-2):1-22.
APA	Gao, J,&Klemd, R.(2003).Formation of HP-LT rocks and their tectonic implications in the western Tianshan Orogen, NW China: geochemical and age constraints.LITHOS,66(1-2),1-22.
MLA	Gao, J,et al."Formation of HP-LT rocks and their tectonic implications in the western Tianshan Orogen, NW China: geochemical and age constraints".LITHOS 66.1-2(2003):1-22.