Metamorphic evolution, mineral chemistry and thermobarometry of schists and orthogneisses hosting ultra-high pressure eclogites in the Dabieshan of central China

	Metamorphic evolution, mineral chemistry and thermobarometry of schists and orthogneisses hosting ultra-high pressure eclogites in the Dabieshan of central China
	Carswell, DA ; Wilson, RN ; Zhai, M
刊名	LITHOS
	2000-04-01
卷号	52 期号:1-4 页码:121-155
关键词	ultra-high pressure schists orthogneisses eclogites phengites garnets
ISSN号	0024-4937
文献子类	Article
英文摘要	As is typical of ultra-high pressure (UHP) terrains, the regional extent of the UHP terrain in the Dabieshan of central China is highly speculative, since the volume of eclogites and paragneisses preserving unequivocal evidence of coesite and/or diamond stability is very small. By contrast, the common garnet (X-Mn = 0.18-0.45)-phengite (Si = 3.2-3.35)-zoned epidote (Ps(38-97))-biotite-titanite-two feldspars-quartz assemblages in the more extensive orthogneisses have been previously thought to have formed under low P-T conditions of ca. 400 +/- 50 degrees C at 4 kbar, However, certain orthogneiss samples preserve garnets with X-Ca up to 0.50, rutile inclusions within titanite or epidote and relict phengite inclusions within epidote with Si contents p.f.u. of up to 3.49 - overlapping with the highest values (3.49-3.62) recorded for phengites in samples of undoubted UHP schists. These and other mineral composition features (such as A-site deficiencies in the highest Si phengites, Na in garnets linked to Y + Yb substitution and Al F Ti-1 O-1 substitution in titanites) are taken to be pointers towards the orthogneisses having experienced a similar metamorphic evolution to the associated UHP schists and eclogites. Re-evaluated garnet-phengite and garnet-biotite Fe/Mg exchange thermometry and calculated 5 rutile + 3 grossular + 2SiO(2) + H2O = 5 titanite + 2 zoisite equilibria indicate that the orthogneisses may indeed have followed a common subduction-related clockwise P-T path with the UHP paragneisses and eclogites through conditions of P-max at ca. 690 degrees C-715 degrees C and 36 kbar to T-max at ca. 710 degrees C-755 degrees C and 18 kbar, prior to extensive re-crystallisation and re-equilibration of these ductile orthogneisses at ca. 400 degrees C-450 degrees C and 6 kbar. The consequential conclusion, that it is no longer necessary to resort to models of tectonic juxtapositioning to explain the spatial association of these Dabieshan orthogneisses with undoubted UHP lithologies. has far-reaching implications for the interpretation of controversial gneiss-eclogite relationships in other UHP metamorphic terrains. (C) 2000 Elsevier Science B.V. All rights reserved.
WOS关键词	COESITE-BEARING ECLOGITES ; COUNTRY ROCKS ; EASTERN CHINA ; GARNET ; SHAN ; MG ; FE ; PHENGITE ; TERRANE ; GEOTHERMOMETER
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000086267700009
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/76103]
专题	中国科学院地质与地球物理研究所
通讯作者	Carswell, DA
作者单位	1.Univ Sheffield, Dept Earth Sci, Sheffield S3 7HF, S Yorkshire, England 2.Univ Leicester, Dept Geol, Leicester LE1 7RH, Leics, England 3.Acad Sinica, Inst Geol, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Carswell, DA,Wilson, RN,Zhai, M. Metamorphic evolution, mineral chemistry and thermobarometry of schists and orthogneisses hosting ultra-high pressure eclogites in the Dabieshan of central China[J]. LITHOS,2000,52(1-4):121-155.
APA	Carswell, DA,Wilson, RN,&Zhai, M.(2000).Metamorphic evolution, mineral chemistry and thermobarometry of schists and orthogneisses hosting ultra-high pressure eclogites in the Dabieshan of central China.LITHOS,52(1-4),121-155.
MLA	Carswell, DA,et al."Metamorphic evolution, mineral chemistry and thermobarometry of schists and orthogneisses hosting ultra-high pressure eclogites in the Dabieshan of central China".LITHOS 52.1-4(2000):121-155.