西昆仑晚三叠世巴尔达灵花岗岩体年代学、岩石地球化学及对古特提斯后碰撞构造演化的约束  

Geochronology and geochemistry of Late Triassic Baerdaling granitoids in West Kunlun orogenic belt and its constraints on the post-collision tectonic evolution of Paleo-Tethys

作　　者：杜保峰 李珊珊[1,3] 张荣臻 胡红雷 乔天荣 钱金龙 杨府 DU BaoFeng;LI ShanShan;ZHANG RongZhen;HU HongLei;QIAO TianRong;QIAN JinLong;YANG Fu(Frontiers Science Center for Deep-time Digital Earth,State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Henan Key Laboratory of Metal Mineral Mineralization Geological Processes and Resource Utilization,Henan Academy of Geology,Zhengzhou 450016,China;School of Science,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)深时数字地球前沿科学中心,地质过程与矿产资源国家重点实验室,地球科学与资源学院,北京100083 [2]河南省地质研究院,河南省金属矿产成矿地质过程与资源利用重点实验室,郑州450016 [3]中国地质大学(北京)数理学院,北京100083

出　　处：《岩石学报》2024年第6期1887-1906,共20页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41872080);中央返还新疆地质勘查基金项目(K15-1-LQ01);河南省科技攻关项目(242102320363)联合资助.

摘　　要：西昆仑造山带发育大量早中生代岩浆岩,其形成与古特提斯洋俯冲碰撞密切相关,而关于古特提斯后碰撞具体时限仍存在较大争议。巴尔达灵花岗岩体是西昆仑造山带面积最大的慕士塔格复式岩体组成部分,本文对其开展了岩石学、LA-ICPMS锆石U-Pb年代学及全岩主、微量元素分析,揭示了岩体形成时代、岩石成因与岩浆源区属性,并进一步探讨了古特提斯后碰撞构造演化过程。巴尔达灵花岗岩体主要岩性为花岗闪长岩、二长花岗岩和正长花岗岩,发育大量暗色微细粒包体。锆石U-Pb年龄分别为237Ma、233Ma和231Ma,表明岩体形成时代为晚三叠世早期。地球化学结果显示,岩石具有高铝、富碱和低镁特征,A/CNK为0.94~1.02,属准铝质-弱过铝质高钾钙碱性岩石。岩石分异指数偏高(67.3~81.1),岩浆演化以结晶分异为主,为分异程度偏高的I型花岗岩。岩石轻、重稀土元素分馏较为明显,具弱至中等负Eu异常,富集Rb、Th、U、Zr、Hf,亏损Ba、Nb、Sr、P、Ti;Nb/Ta比值(7.2~16.7)和Zr/Hf比值(28.4~40.3)偏低,而Rb/Sr比值(0.2~1.4)和La/Ta比值(20.0~56.4)较高,指示源岩以壳源为主,应有少量幔源物质的加入。结合区域演化,本文认为巴尔达灵花岗岩体形成于晚三叠世早期古特提斯后碰撞过程,与中三叠世同碰撞挤压向后碰撞伸展转换有关,并指示古特提斯演化进入后碰撞伸展期的起始时限应不晚于237Ma。Early Mesozoic magmatic rocks are widespread in the West Kunlun orogenic belt,and their formation is genetically linked to the subduction-collision of the Paleo-Tethys Ocean.However,the concrete tectonic evolution process of Paleo-Tethys Ocean remains controversial.Granitoids in the Baerdaling area are the part of Muztagata complex pluton,the largest complex in the West Kunlun orogenic belt,thus that is critical significance to decode the evolution of Paleo-Tethys.This study discusses their genesis,magma sources and ages through petrology,geochemistry and LA-ICP-MS zircon U-Pb chronology.Baerdaling granitoids mainly consist of granodiorite,monzogranite and syenogranite.The zircon U-Pb weighted mean 206 Pb/238 U age of corresponding lithology respectively are 237Ma,233Ma and 231Ma,which invaded in the early stage of Late Triassic.The whole-rock geochemical data show that Baerdaling granitoids with high Al 2O 3,alkali and low MgO are classified as metaluminium-slightly peraluminium and high potassium-calcium alkaline granitoids.The high rock differentiation index(67.3~81.1)suggest the magmatic evolution is dominated by crystallization differentiation and highly differentiated I-type granite.Rare earth elements are characterized by obviously high LREE/HREE ratios and weak to medium negative Eu with right-leaning pattern.Trace elements are obviously enriched with Rb,Th,U,Zr and Hf while depletion of Ba,Nb,Sr,P and Ti.In addition,Baerdaling granitoids have low Nb/Ta(7.2~16.7)and Zr/Hf(28.4~40.3),high Rb/Sr(0.2~1.4)and La/Ta(20.0~56.4),which indicate that the source of rocks was mainly derived from the crust material with minor amount of mantle magma.Combined with regional geological evolution,we conclude that Baerdaling granitoids were formed in the post-collision environment in the early stage of Late Triassic,which may be related to the transformation of Paleo-Tethys from the compressive of main collision to the extension of post-collision.This result also indicates that the time limit for the begin of the post-coll

关 键 词：巴尔达灵 I型花岗岩 后碰撞环境 晚三叠世 古特提斯 西昆仑 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]