Variation in peak P-T conditions across the upper contact of the UHP terrane, Dabieshan, China: gradational or abrupt?

doi:10.1111/j.1525-1314.2006.00670.x

	Variation in peak P-T conditions across the upper contact of the UHP terrane, Dabieshan, China: gradational or abrupt?
	Shi, Y.; Wang, Q.
刊名	JOURNAL OF METAMORPHIC GEOLOGY
	2006-12-01
卷号	24 期号:9 页码:803-822
关键词	Dabieshan eclogites peak P-T conditions Taihu area
ISSN号	0263-4929
DOI	10.1111/j.1525-1314.2006.00670.x
文献子类	Article
英文摘要	The Southern Dabieshan Terrane (SDT) has previously been divided into high-pressure (HP) and ultrahigh-pressure (UHP) terranes, and its regional extent and the tectonic nature of its boundaries are hotly debated topics. In this study, an eclogite-bearing area of 100 km(2) near Taihu is mapped in detail, and divided into Northern, Middle and Southern Zones on the basis of lithological characteristics. The Northern Zone consists of epidote-biotite gneiss and eclogite blocks, the Middle Zone includes granitic gneiss, biotite gneiss, eclogites and amphibolite, and the Southern Zone is composed mainly of garnet-bearing mica schist. The eclogites occur mainly as lens or blocks in the Northern and Middle Zones. The peak P-T conditions for 61 eclogite samples across the area are estimated using the Grt-Cpx Fe2+-Mg thermometers and the Grt-Cpx-Phe barometers. The results indicate three different P-T regions: 2.82-4.09 GPa/759-942 degrees C in the Northern Zone, and 2.00-3.54 GPa/641-839 degrees C in the granitic gneiss and 1.38-2.36 GPa/535-768 degrees C in the biotite gneiss from the Middle Zone. Combined with the spatial distribution of eclogites across the area, the P-T values for eclogites increase continuously from the south to the north, defining a reference 'geotherm' of 5 degrees C km(-1). However, some unreasonable apparent gradients can be established along two south-north profiles across the area, and display a P-T difference between the Northern and Middle zones. On the basis of the average P-T data for eclogites across the area, a gap of at least 0.3 GPa/20 degrees C exists between the Northern and Middle zones. By contrast, the P-T values of eclogites from the Middle zone show a coherent pattern with transitional characteristics from HP in the south to UHP in the north. We suggest that the SDT was a coherent slab during subduction, and was broken up by a major fault during exhumation, which was formed under UHP metamorphic conditions.
WOS关键词	COESITE-BEARING ECLOGITES ; PRESSURE METAMORPHIC BELT ; EAST-CENTRAL CHINA ; COOLING HISTORY ; MOUNTAINS ; SHAN ; ZIRCON ; GEOTHERMOMETER ; CONSTRAINTS ; EXHUMATION
WOS研究方向	Geology
语种	英语
出版者	BLACKWELL PUBLISHING
WOS记录号	WOS:000242017000002
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/66420]
专题	中国科学院地质与地球物理研究所
通讯作者	Shi, Y.
作者单位	Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Shi, Y.,Wang, Q.. Variation in peak P-T conditions across the upper contact of the UHP terrane, Dabieshan, China: gradational or abrupt?[J]. JOURNAL OF METAMORPHIC GEOLOGY,2006,24(9):803-822.
APA	Shi, Y.,&Wang, Q..(2006).Variation in peak P-T conditions across the upper contact of the UHP terrane, Dabieshan, China: gradational or abrupt?.JOURNAL OF METAMORPHIC GEOLOGY,24(9),803-822.
MLA	Shi, Y.,et al."Variation in peak P-T conditions across the upper contact of the UHP terrane, Dabieshan, China: gradational or abrupt?".JOURNAL OF METAMORPHIC GEOLOGY 24.9(2006):803-822.