地质学报2017，Vol.91Issue(8)：1729-1742,14.
西藏羌塘南缘青草山北花岗闪长岩锆石U-Pb年代学、地球化学特征及其成矿意义
Zircon U-Pb Geochronology and Geochemistry Characteristics of the North Qingcaoshan Granodiorite in the Southern Margin of Qiangtang, Tibet, and their Metallogenic Significance
摘要
Abstract
The North Qingcaoshan granodiorite,located in the southern margin of Qiangtang block and the northern part of the Bangongco Suture zone,occurs as dykes or stocks in the carbonatite of Longge Formation(P2l).The study carried out zircon U-Pb geochronology and trace element geochemistry analysis of the granodiorite.The results show that the magmatic zircons have an weighted 206Pb/238U age of 154.8 ±1.2Ma(MSWD=1.7),belonging to the late Jurassic.This age is quite consistent with that of Rena Co adakite dacite.Petrochemical analyses indicate that the granodiorite belongs to quasi-aluminous and calcalkalic series,and is enriched in light rare earth elements and large ion lithophile elements,depleted in heavy earth elements and high field-strength elements,with weak Eu anomalies,indicating characteristic of typical island-arc magma.The in-site trace elements analysis of zircons shows that the zircons are enriched in heavy rare earth and relatively depleted in light rare earth.All of the grains fall into the kimberlite range in the Nb/Ta-Y discrimination diagram of source rock,and all the samples plotted in the discrimination diagrams of tectonic environments of granodiorite also imply that they were derived from mantle magma.The granodiorite formed by the partial melting of subducted oceanic curst after the Bangongco-Nujiang oceanic crust subducted northward to the certain depth in later Jurassic stage,with contamination of mantle wedge during magma uprising.During emplacement of the magma,part of magma formed intermediate-felsic granodiorite magmatic chamber while the other part erupted the surface to form the Rena Co decites.关键词
锆石U-Pb年龄/花岗闪长岩/晚侏罗世/矽卡岩矿化/羌塘南缘Key words
Zircon U-Pb dating/granodiorite/Late Jurassic/skarn metallogenetic/southern margin of Qiangtang引用本文复制引用
张腾蛟,陈颖,李佑国..西藏羌塘南缘青草山北花岗闪长岩锆石U-Pb年代学、地球化学特征及其成矿意义[J].地质学报,2017,91(8):1729-1742,14.基金项目
本文为国家自然科学基金资助项目(批准号:40173022)的成果. （批准号:40173022）
