南蒙古巴音苏赫图矿区英安岩地球化学特征及其构造意义  

Geochemical characteristics of dacite from the Bayinsuhetu deposit in South Mongolia and its tectonic implications

作　　者：郭志华 张宝林[2] 党永岐 侯金亮 张丽春 高磊 GUO Zhihua;ZAHNG Baolin;DANG Yongqi;HOU Jinliang;ZHANG Lichun;GAO Lei(Department of Geology,Mining Engineering College,North China University of Science and Technology,Tangshan 063009,Hebei,China;Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Bureau of Geological Exploration and Mineral Development of Hebei Province,Tangshan 063000,Hebei,China;Key Laboratory of Orogenic Belts and Crustal Evolution of Ministry of Education/School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]华北理工大学矿业工程学院地质系,河北唐山063009 [2]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [3]河北省地矿局第五地质大队,河北唐山063000 [4]造山带与地壳演化教育部重点实验室/北京大学地球与空间科学学院,北京100871

出　　处：《地质通报》2018年第2期458-466,共9页Geological Bulletin of China

基　　金："十一五"科技支撑计划重大项目<典型覆盖区金属矿综合地球物理定位预测技术开发及应用>(编号:2006BAB01A02);华北理工大学矿业工程学院校级博士科研启动基金项目<蒙古国巴音苏赫图钨矿床岩浆岩锆石年代学研究>(编号:20164043)

摘　　要：在南蒙古巴音苏赫图矿区古生代地层中新发现一套火山岩,其Rb-Sr同位素年龄为409±19Ma,与前人划分的地层年代(志留纪-泥盆纪)较吻合。英安岩的SiO_2含量为63.23%~73.36%,Al_2O_3含量为10.25%~15.56%。英安岩轻稀土元素富集,重稀土元素亏损,具有较强的负Eu异常。岩石学和地球化学综合研究表明,该套火山岩基本同期同源演化,且岩性变化较小,以流纹岩-英安岩类为主。根据钾含量,该套火山岩为中钾钙碱性系列。英安岩落在靠近盆岭构造域的位置,显示出略亏损的特征,与原始地幔PM端元接近。推测该套火山岩形成于古亚洲洋闭合过程中的岛弧环境,表明火山岩形成时古亚洲洋可能还没有闭合。A set of volcanic rocks were recently found in Palaeozoic strata in the Bayinsukhtuore district of South Mongolia.The RbSr isotopic age of the rocks is 409±19Ma,which is consistent with the chronological age(Silurian-Devonian)obtained from previous work.The SiO2 content of dacite is 63.23%~73.36%,while the Al2O3 content is 10.25%~15.56%.The dacite is LREE enrichment,HREE loss,and has strong Eu negative anomaly.Based on petrology and geochemistry,it is held that this set of volcanic rocks evolved in the same period and came from the same source.The lithologic character of the rocks is mainly of dellenite-dacite type,with little change.According to the Kalium analysis,the volcanic rocks were derived from the potassium calc-alkaline series.It is suggested that the melted mantle source area was reformed by the subducting plate.During this process the original magma was generated from the liquid mantle of the subducting zone.At the same time crustal contamination happened.The magmatic evolution would be the main reason for generating the combined set of the volcanic rocks.It also implies that this set of volcanic rocks was formed in the island arc during the closing of pal-Asia,which indicates that the closing of pal-Asia was later than the formation of this set of volcanic rocks.

关 键 词：南蒙古 火山岩 地球化学特征 地幔 成因 

分 类 号：P588.142[天文地球—岩石学] P591[天文地球—地质学]