西藏得明顶地区叶巴组火山岩地球化学特征和同位素U-Pb年龄证据  

Evidences from Geochemistry and Zircon U-Pb Geochronology of Volcanic Rocks of Yeba Formation in Demingding Area,the East of Middle Gangdise,Tibet

作　　者：陈炜[1,2] 马昌前[3] 边秋娟[3] 胡远清[1,2] 龙桃成[2] 喻水林[2] 陈冬明 屠江海[1,2] 

机构地区：[1]中国地质大学研究生院,武汉430074 [2]湖北省鄂东北地质大队,湖北孝感432100 [3]中国地质大学地球科学学院,武汉430074 [4]湖北省地质调查院,武汉430022

出　　处：《地质科技情报》2009年第3期31-40,共10页Geological Science and Technology Information

基　　金：中国地质调查局矿产资源补偿费矿产勘查项目(矿调[2005]1-10]

摘　　要：对西藏得明顶地区叶巴组英安岩进行了锆石SHRIMP的U-Pb测年,获得(192.7±1.3)Ma的年龄值可代表得明顶地区叶巴组的年龄,其形成时代为早侏罗世,与达孜县地区叶巴组火山岩近同期。地质年代学研究和岩石组合特征显示,得明顶地区的叶巴组岩性主要为一套浅变质安山岩、英安岩、流纹岩、酸性凝灰岩夹少量碎屑岩、碳酸盐岩,可分为上、中、下3部分。地球化学特征显示,叶巴组为一套中酸性火山岩,可能是雅鲁藏布江洋向北俯冲、消减的产物,形成于岛弧环境。The dacite of the Yeba Formation in Demingding, Tibet is dated （192.7±1.3） Ma by zircon SHRIMP U-Pb dating, representing the age of the formation in the area. The dacite of the Yeba Formation was formed in Early Jurassic, nearly the same time as that of volcanic rocks of the Yeba Formation in Dazi regions. The study of the features of rock combination and geochronology shows that the Yeba For- mation is made up of shallow andesite, dacite, rhyolite, acid tuff with little clastic rock and carbonate rocks, and can be divided into upper, middle and lower parts. Geochemical characteristics illustrate that the rock of the Yeba Formation is the acidic volcanic rock, and may be a product of the northward subduction and reduction of the Yarlungzangbo ocean, and formed in the island arc environment.

关 键 词：早侏罗世 叶巴组 火山岩 年龄 得明顶 西藏 

分 类 号：P588.14[天文地球—岩石学]