西藏洞错晚白垩世花岗闪长斑岩:岩石圈拆沉的产物  

Late Cretaceous Dongco granodiorite porphyry,Tibet:Product of lithospheric delamination

作　　者：车旭 刘一鸣 范建军[4] 于云鹏[4] 郭润华[3] 权立诚[5] 解超明 王明[4] CHE Xu;LIU Yiming;FAN Jianjun;YU Yunpeng;GUO Runhua;QUAN Licheng;XIE Chaoming;WANG Ming(Institute of Disaster Prevention,Langfang 065201,Hebei,China;Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,Ministry of Education,Ocean University of China,Qingdao 266100,Shandong,China;College of Earth Science,Jilin University,Changchun 130061,Jilin,China;Applied Geology Research Center of China Geological Survey,Chengdu 610036,Sichuan,China)

机构地区：[1]防灾科技学院,河北廊坊065201 [2]自然资源部深部动力学重点实验室,中国地质科学院地质研究所,北京100037 [3]深海圈层与地球系统前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学,山东青岛266100 [4]吉林大学地球科学学院,吉林长春130061 [5]中国地质调查局应用地质研究中心,四川成都610036

出　　处：《地质通报》2021年第8期1357-1368,共12页Geological Bulletin of China

基　　金：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);中央高校基本科研业务费专项《青藏高原冈瓦纳大陆北缘构造演化历程及地球动力学机制》(编号:202012015);《青藏高原古-新特提斯洋构造演化异同》(编号:202072017)。

摘　　要：班公湖-怒江缝合带是国内外备受关注的特提斯构造域的重要组成部分,可为恢复和反演特提斯洋构造演化提供重要依据。对南羌塘地块南缘洞错地区晚白垩世花岗闪长斑岩进行了详细的岩石学、锆石U-Pb定年、全岩地球化学和Lu-Hf同位素研究。锆石U-Pb定年和Lu-Hf同位素研究结果显示,该花岗闪长斑岩形成时代为74.1±1.1 Ma,εHf(t)值为4.5~6.9。全岩地球化学特征显示,其为高钾钙碱性系列,富集轻稀土元素,轻重稀土元素分馏较强,具弱负Eu异常;富集Rb、Th、U、K和Pb,亏损Ba、Nb、Ta、La、Ce、P和Ti。该花岗闪长斑岩为加厚新生下地壳部分熔融的产物。在综合区域最新研究成果的基础上,认为该花岗闪长斑岩形成于后碰撞环境,为班公湖-怒江洋闭合后岩石圈拆沉的产物。The Bangong-Nujiang suture zone is an important part of Tethyan tectonic domain,which is significant for revealing the evolution of Tethys Ocean,Tibet Plateau.The Late Cretaceous granodiorite porphyry in Dongco area from Southern Qiangtang terrane was selected to study petrology,zircon U-Pb age,Lu-Hf isotopic and whole-rock geochemistry.Zircon U-Pb dating and Lu-Hf isotopic analysis yields an age of 74.1±1.1 Ma,with positiveεHf(t)values of 4.5~6.9.Geochemical data reveal that the granodiorite porphyry belong to high-K calc-alkaline series,enriched in light rare earth elements with weak negative Eu anomaly and strong fractionation between light and heavy rare earth elements.In spider diagram,it is enriched in Rb,Th,U,K and Pb,and depleted in Ba,Nb,Ta,La,Ce,P and Ti.It is inferred that the granodiorite porphyry was derived from partial melting of thickened juvenile lower crust.Combined with previous research,it is concluded that the Dongco granodiorite porphyry was emplaced in post-collision tectonic setting as the product of lithosphere delamination,postdating the closure of Bangong-Nujiang Ocean.

关 键 词：西藏 洞错 晚白垩世 花岗闪长斑岩 拆沉 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.12[天文地球—地质学]