Triassic eclogites from central Qiangtang, northern Tibet, China: Petrology, geochronology and metamorphic P-T path

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	Triassic eclogites from central Qiangtang, northern Tibet, China: Petrology, geochronology and metamorphic P-T path
	Zhai, QG (Zhai, Qing-Guo); Zhang, RY (Zhang, Ru-Yuan); Jahn, BM (Jahn, Bor-Ming); Li, C (Li, Cai); Song, SG (Song, Shu-Guang); Wang, J (Wang, Jun)
刊名	LITHOS
	2011
卷号	125 期号:1-2 页码:173-189
关键词	Tibet Qiangtang Eclogite Zircon U-Pb and (40)Ar/(39)Ar dating Oceanic subduction
ISSN号	0024-4937
英文摘要	High-pressure (HP)/low-temperature (LT) metamorphic rocks, such as eclogite and blueschist, are generally regarded as an indicator of subduction-zone metamorphism. Eclogites have recently been discovered in the central Qiangtang Block. Their occurrence is highly significant to the understanding of the closure of the Paleo-Tethys and tectonic evolution of northern Tibet. We report the results of petrological, mineralogical and geochronological investigations of these rocks, and discuss their tectonic implications. The Qiangtang eclogite occurs as blocks and lenses in Grt-Phn schist and marble, and is composed of garnet, omphacite, phengite and rutile. Eclogitic garnet contains numerous inclusions, such as glaucophane and phengite in the core, and omphacite in the mantle or inner rim. In strongly retrograded eclogite. the omphacite is replaced by glaucophane, barroisite and albite. Four stages of metamorphic evolution can be determined (1) prograde blueschist facies; (2) peak eclogite facies (3) decompression blueschist facies and (4) retrograde greenschist facies. Using the Grt-Omp-Phn geothermobarometer, a peak eclogite facies metamorphic condition of 410-460 degrees C and 2.0-2.5 GPa was determined. Zircon U-Pb dating gave ages of 230 +/- 3 Ma and 237 +/- 4 Ma for two eclogite samples. The ages are interpreted as the time of eclogite facies metamorphism. Moreover, (40)Ar/(39)Ar dating of phengite from the eclogite and Grt-Phn schist yielded ages about 220 Ma, which are probably indicative of the time of exhumation to the middle crust. We conclude that the HP/LI metamorphic rocks were formed by northward subduction of the Paleo-Tethys Ocean and they marked a Triassic suture zone between the Gondwana-derived block and Laurasia. (C) 2011 Elsevier B.V. All rights reserved.
学科主题	变质岩岩石学
WOS关键词	ULTRAHIGH-PRESSURE METAMORPHISM ; ZONE WESTERN ALPS ; U-PB ; TECTONIC IMPLICATIONS ; UHP METAMORPHISM ; GEOLOGICAL SIGNIFICANCE ; ZIRCON GEOCHRONOLOGY ; MICROPROBE ANALYSES ; OCEANIC SUBDUCTION ; EXCESS ARGON
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000292663600012
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/39351]
专题	中国地质调查局
作者单位	Peking Univ, Sch Earth & Space Sci, Beijing 100871, Peoples R China
推荐引用方式 GB/T 7714	Zhai, QG ,Zhang, RY ,Jahn, BM ,et al. Triassic eclogites from central Qiangtang, northern Tibet, China: Petrology, geochronology and metamorphic P-T path[J]. LITHOS,2011,125(1-2):173-189.
APA	Zhai, QG ,Zhang, RY ,Jahn, BM ,Li, C ,Song, SG ,&Wang, J .(2011).Triassic eclogites from central Qiangtang, northern Tibet, China: Petrology, geochronology and metamorphic P-T path.LITHOS,125(1-2),173-189.
MLA	Zhai, QG ,et al."Triassic eclogites from central Qiangtang, northern Tibet, China: Petrology, geochronology and metamorphic P-T path".LITHOS 125.1-2(2011):173-189.