青藏高原羌南-保山板块都古尔地区早白垩世变质辉长岩:对班公湖-怒江洋俯冲闭合的制约  

The Early Cretaceous Duguer metagabbro from Qiangnan-Baoshan block, Tibet Plateau: Implications for the subduction and closure of Bangong Co-Nujiang Ocean

作　　者：刘一鸣 李才[2] 李三忠[1,3] 解超明[2] 王明 范建军[2] 刘金恒[2] 郭润华[1,3] LIU Yiming;LI Cai;LI Sanzhong;XIE Chaoming;WANG Ming;FAN Jianjun;LIU Jinheng;GUO Runhua(Key Lab of Submarine Geosciences and Prospecting Techniques,Ministry of Education,and College of Marine Geosciences/Ocean University of China,Qingdao 266100,Shandong,China;College of Earth Science,Jilin University,Changchun 130061,Jilin,China;Laboratory of Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,Shandong,China)

机构地区：[1]海底科学与探测技术教育部重点实验室/中国海洋大学海洋地球科学学院,山东青岛266100 [2]吉林大学地球科学学院,吉林长春130061 [3]青岛海洋科学与技术国家实验室,海洋矿产资源评价与探测技术功能实验室,山东青岛266237

出　　处：《地质通报》2018年第8期1450-1463,共14页Geological Bulletin of China

基　　金：博士后创新人才支持计划项目《藏北羌塘中部奥陶系海相地层的沉积环境及成因机制探讨》(编号:BX201700216)、中国博士后科学基金项目《青藏高原中部尼则地区晚白垩世构造岩浆事件》(编号:2017M622273)、国家重点研发计划项目《燕山期多板块汇聚与陆缘构造过程》(编号:2017YFC0601401)、国家自然科学基金项目《青藏高原八宿地区寒武纪片麻状花岗岩:对冈瓦纳大陆北缘早古生代构造演化的制约》(批准号:41802232)、《青藏高原羌塘南部埃迪卡拉纪地层研究》(批准号:41602230)《班公湖

摘　　要：班公湖-怒江洋的俯冲闭合过程对于青藏高原早期形成与演化研究具有重要的意义。在羌南-保山板块腹地都古尔地区识别出早白垩世变质辉长岩。对其进行了详细的岩石学、年代学和全岩地球化学研究。锆石U-Pb测年结果显示,该辉长岩形成年龄为110.4±1.4Ma。全岩地球化学特征显示,该辉长岩具有碱性玄武岩的特征,富集轻稀土元素,轻、重稀土元素分馏较强,无明显的Eu异常;富集Rb、Pb、Nd和Ti,亏损Ba、K、Sr和Y,具有洋岛型玄武岩的亲缘性。该辉长岩为尖晶石-石榴子石二辉橄榄岩经低程度部分熔融的产物,源区存在少量的石榴子石残留。岩浆在上升过程中经历了少量下地壳物质的混染和以斜方辉石为主的分离结晶作用。在综合区域最新研究成果的基础上,认为该辉长岩形成于板内环境,为班公湖-怒江洋闭合后洋脊俯冲的产物。The subduction and closure of the Bangong Co-Nujiang Ocean are recognized as significant events in geotectonic evolution of Tibet Plateau.This study focused on the first identified Early Cretaceous metagabbro in Duguer area from central QiangnanBaoshan block.The authors report the results of petrological,zircon U-Pb age and whole-rock geochemical analyses.Zircon U-Pb age of 110.4±1.4Ma indicates emplacement during the late Early Cretaceous.Geochemical data for Duguer metagabbro indicate that it has an alkaline basalt affinity and is characterized by enrichment of light rare earth elements with no Eu anomaly,enrichment of Rb,Pb,Nd and Ti,and depletion of Ba,K,Sr and Y,similar to features of OIB.This metagabbro was derived from low partial melting of spinel-garnet lherzolites,with minor residual garnet.The ascending magma underwent minor lower crust contamination and orthopyroxene-donimated fractional crystallization.Combining the data obtained by the authors with previous research,the authors have reached the conclusion that the Duguer metagabbro was developed in an intraplate tectonic setting and was formed by ridge subduction after the closure of Bangong Co-Nujiang Ocean.

关 键 词：羌塘中部 都古尔 辉长岩 地球化学 班公湖-怒江洋 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.124[天文地球—地质学]