青海东昆南构造带战红山地区中酸性火山岩的发现及其地质特征  

DISCOVERY AND GEOLOGICAL CHARACTERISTICS OF INTERMEDIATE ACID VOLCANIC ROCKS IN THE ZHANHONGSHAN AREA,EAST KUNNAN TECTONIC BELT,QINGHAI

作　　者：付彦文 薛万文 王涛[1,2] 张金明 陈秉芳[1,2] Fu Yanwen;Xue Wanwen;Wang Tao;Zhang Jinming;Chen Bingfang(Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Laboratory of Qinghai Province,Xining,Qinghai 810012,China;Qinghai Institue of Geological Survey,Xining,Qinghai 810012,China)

机构地区：[1]青海省青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 [2]青海省地质调查院,青海西宁810012

出　　处：《矿物岩石》2019年第4期78-85,共8页Mineralogy and Petrology

基　　金：中国地质调查局项目《青海省都兰县尕日当地区1∶5×104四幅区域地质调查》(编号12120113028500)

摘　　要：在东昆南达里吉格塘-战红山一带新发现一套中酸性火山岩,岩性主要有流纹岩、英安岩、安山岩三种岩性。岩石地球化学特征参数为A/CNK在1.20~1.61之间,σ=1.41~1.67,K2O均值3.06%,属钙碱性系列,且Mg#平均值大于40。岩性中ΣREE=119.70~279.08×10-6,LREE/HREE=4.97~8.01,δEu=0.45~0.60。针对英安岩利用高精度LA-ICP-MS锆石U-Pb同位素测年结果显示形成年龄为248.4±4.3 Ma,属早三叠世晚期。研究成果确定区内该套中酸性火山岩形成于由俯冲向碰撞转换过渡阶段的活动大陆边缘构造环境,该套岩性锆石U-Pb年龄的确定及成因的探讨,为东昆仑布青山一带古特提斯洋盆在中三叠世早期的构造演化提供了重要的地质信息。A set of intermediate-acidic volcanic rocks of rhyolite,dacite and andesite have been found in the Dalijigetang-Zhanhongshan area of eastern Kunnan.Geochmical and chronological study of the volcanic rocks are carried out so as to discuss their formation age and tectonic setting.Geochemical analysis shows that the volcanic rocks have following characteristics:A/CNK ranges from 1.20 to 1.61 and σ from1.41 to 1.67.K2O has a mean value of 3.06%,Mg# is more than 40,belonging to calc-alkaline series and characteristic of low potassium and high aluminium.ΣREE is in the range of 119.70-279.08×10-6,LREE/HREE from 4.97 to 8.01,and δEu from 0.45 to 0.60.LA-ICP-MS zircon U-Pb dating for dacite yields a formation age of 248.4±4.3 Ma,indicating that the volcanic rocks were the late stage product in early Triassic.Based on the research results,it is proposed that the intermediate-acid volcanic rocks were formed in the active continental margin tectonic environment during the transitional period from subduction to collision.The determination of formation age of the volcanic rocks and the discussion of their genesis provide important geological information for the tectonic evolution of the Paleo-Tethys oceanic basin in Buqingshan area of east Kunlun in the early stage of middle Triassic period.

关 键 词：中酸性火山岩 地球化学 LA-ICP-MS锆石U-Pb 转换过渡 东昆南 

分 类 号：P588.14[天文地球—岩石学]