Late Palaeozoic Ar-40/Ar-39 ages of the HP-LT metamorphic rocks from the   Kekesu Valley, Chinese southwestern Tianshan: new constraints on   exhumation tectonics

doi:10.1080/00206814.2015.1084487

CORC > 北京大学 > 地球与空间科学学院

	Late Palaeozoic Ar-40/Ar-39 ages of the HP-LT metamorphic rocks from the Kekesu Valley, Chinese southwestern Tianshan: new constraints on exhumation tectonics
	Xia, Bin ; Zhang, Lifei ; Bader, Thomas ; Shen, Tingting ; Chen, Nengsong
刊名	INTERNATIONAL GEOLOGY REVIEW
	2016
关键词	HP-LT rocks 40Ar/39Ar ages excess argon exhumation process Kekesu Valley SW Tianshan P-T PATH HIGH-PRESSURE METAMORPHISM MASSIF WESTERN ALPS K-AR AGE NW-CHINA EXCESS ARGON NORTHWESTERN CHINA UHP METAMORPHISM SOUTH TIANSHAN OROGENIC BELT
DOI	10.1080/00206814.2015.1084487
英文摘要	Although numerous ages have been obtained for the Chinese southwestern Tianshan high pressure/ultrahigh pressure-low temperature (HP/UHP-LT) metamorphic belt in the past two decades, its exhumation history is still controversial. The poor age constraint was related to the appealing low metamorphic temperatures and excess Ar commonly present under HP/UHP conditions. This study aims to provide new age constraints on the orogen's exhumation by obtaining Ar-40/Ar-39 mica ages using the conventional step-heating technique, with emphasis on the avoidance of excess Ar contamination. From a cross section along the Kekesu Valley, four samples, three from the HP-LT metamorphic belt (TK050, TK051, and TK081) and one from the southern margin of the low pressure metamorphic belt (TK097), were selected for Ar-40/Ar-39 dating. Phengites from garnet glaucophane schist TK050 and the surrounding rock garnet phengite schist TK051 yield comparable plateau ages of 321.4 +/- 1.6 and 318.6 +/- 1.6Ma, respectively, while epidote mica schist TK081 gives a younger plateau age of 293.3 +/- 1.5Ma. Considering the chemical compositions of phengites, mineral assemblages, and microstructures in the thin slices, we suppose that the former represents the time the HP rocks retrograded from the peak stage (eclogite facies) to the (epidote)-blueschist facies, whereas the latter reflects greenschist facies overprinting. Biotite and muscovite from two-mica quartzite TK097 give similar plateau ages of 253.0 +/- 1.3 and 247.1 +/- 1.2Ma, interpreted to date movement on the post collisional transcrustal South Nalati ductile shear zone. By combining our new ages with published data, a two-stage exhumation model is suggested for the Chinese southwestern Tianshan HP/UHP-LT metamorphic belt: initial fast exhumation to a depth of about 30-35km by similar to 320Ma was followed by relatively slow (similar to 1mmyear(-1)) uplift to similar to 10km by similar to 293Ma.; Major State Basic Research Development Programme [2015CB856105]; National Science Foundation of China [41330210, 41502043]; China Postdoctoral Science Foundation [2014M562083]; SCI(E); ARTICLE; xiabin@cug.edu.cn; 4; 389-404; 58
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/438452]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Xia, Bin,Zhang, Lifei,Bader, Thomas,et al. Late Palaeozoic Ar-40/Ar-39 ages of the HP-LT metamorphic rocks from the Kekesu Valley, Chinese southwestern Tianshan: new constraints on exhumation tectonics[J]. INTERNATIONAL GEOLOGY REVIEW,2016.
APA	Xia, Bin,Zhang, Lifei,Bader, Thomas,Shen, Tingting,&Chen, Nengsong.(2016).Late Palaeozoic Ar-40/Ar-39 ages of the HP-LT metamorphic rocks from the Kekesu Valley, Chinese southwestern Tianshan: new constraints on exhumation tectonics.INTERNATIONAL GEOLOGY REVIEW.
MLA	Xia, Bin,et al."Late Palaeozoic Ar-40/Ar-39 ages of the HP-LT metamorphic rocks from the Kekesu Valley, Chinese southwestern Tianshan: new constraints on exhumation tectonics".INTERNATIONAL GEOLOGY REVIEW (2016).