^(40)Ar-^(39)Ar and U-Pb ages of metadiorite from the East Kunlun Orogenic Belt: Evidence for Early-Paleozoic magmatic zone and excess argon in amphibole minerals

作     者：CHEN Nengsong, SUN Min, ZHANG Kexin & ZHU YunhaiFaculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China Department of Earth Sciences, The University of Hong Kong, Hong Kong SAR, China 

作者机构：Faculty of Earth Sciences China University of Geosciences Wuhan China Department of Earth Sciences The University of Hong Kong Hong Kong SAR China 

出 版 物：《Chinese Science Bulletin》 (CHINESE SCIENCE BULLETIN)

年 卷 期：2001年第46卷第4期

页      面：330-333页

核心收录：

学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学] 

基　　金：the China Geological Survey Bureau (project on 1 : 250 000 scale geological mapping methods for orogens in western China) and The University of Hong Kong CRCG grant 

主　　题：East Kunlun Orogenic Belt metadiorite geochronology excess argon. 

摘      要：Single-grain zircon U-Pb and amphibole 40Ar-39Ar dating have been conducted on a deformed and metamorphosed diorite in the East Kunlun Orogenic Belt, which intruded into the middle Proterozoic Kuhai Group exposed in the south of Xiangride region, Dulan County, NW Qinghai Province. The zircon gives a concordant U-Pb age of (446.5±9.1) Ma. The amphibole yields Ar plateau age of (488.0±1.2) Ma and an isochronal age of (488.9±5.6) Ma. Age results of both stepwise released Ar and conventional K-Ar analysis are remarkably higher than that of zircon U-Pb, suggesting that the amphibole contains excess argon and the amphibole plateau age cannot be taken as the timing of metamorphism or deformation. The zircon age is interpreted to be crystallization age of the diorite pluton, which suggests that an Early-Paleozoic magmatic zone indeed existed in the East Kunlun Orogenic Belt stretching along the region south to the Golmud, Normuhong and Xiangride.