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	Petrology of coesite-bearing eclogite from Habutengsu Valley, western Tianshan, NW China and its tectonometamorphic implication
	Lue, Z. ; Zhang, L. ; Du, J. ; Bucher, K.
	2009
关键词	Chinese western Tianshan coesite eclogite cold oceanic subduction phase diagram UHP metamorphism HIGH-PRESSURE METAMORPHISM P-T PATH HP-LT ROCKS TECTONIC IMPLICATIONS FACIES METAMORPHISM TEMPERATURE ROCKS UHP METAMORPHISM NORTHWEST CHINA SOUTH TIANSHAN TAUERN WINDOW
英文摘要	Coesite inclusions in garnet have been found in eclogite boudins enclosed in coesite-bearing garnet micaschist in the Habutengsu Valley, Chinese western Tianshan, which are distinguished from their retrograde quartz by means of optical characteristics, CL imaging and Raman spectrum. The coesite-bearing eclogite is mainly composed of porphyroblastic garnet, omphacite, paragonite, glaucophane and barroisite, minor amounts of rutile and dotted (or banded) graphite. In addition to coesite and quartz, the zoned porphyroblastic garnet contains inclusions of omphacite, Na-Ca amphibole, calcite, albite, chlorite, rutile, ilmenite and graphite. Multi-phase inclusions (e.g. Czo + Pg +/- Qtz, Grt II + Qtz and Chl + Pg) can be interpreted as breakdown products of former lawsonite and possibly chloritoid. Coesite occurs scattered within a compositionally homogenous but narrow domain of garnet (outer core), indicative of equilibrium at the UHP stage. The estimate by garnet-clinopyroxene thermometry yields peak temperatures of 420-520 degrees C at 2.7 GPa. Phase equilibrium calculations further constrain the P-T conditions for the UHP mineral assemblage Grt + Omp + Lws + Gln + Coe to 2.4-2.7 GPa and 470-510 degrees C. Modelled modal abundances of major minerals along a 5 degrees C km-1 geothermal gradient suggests two critical dehydration processes at similar to 430 and similar to 510 degrees C respectively. Computed garnet composition patterns are in good agreement with measured core-rim profiles. The petrological study of coesite-bearing eclogite in this paper provides insight into the metamorphic evolution in a cold subduction zone. Together with other reported localities of UHP rocks from the entire orogen of Chinese western Tianshan, it is concluded that the regional extent of UHP-LT metamorphism in Chinese western Tianshan is extensive and considerably larger than previously thought, although intensive retrogression has erased UHP-LT assemblages at most localities.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000271523900012&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; Geology; SCI(E); CPCI-S(ISTP); 78
语种	英语
DOI标识	10.1111/j.1525-1314.2009.00845.x
内容类型	其他
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/155876]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Lue, Z.,Zhang, L.,Du, J.,et al. Petrology of coesite-bearing eclogite from Habutengsu Valley, western Tianshan, NW China and its tectonometamorphic implication. 2009-01-01.

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