西藏班戈地区后碰撞花岗岩岩石成因及其对班公湖--怒江缝合带演化的约束  

Petrogenesis of post collisional granite in Bange area andits constraints on the evolution of Bangong Lake--Nujiang suture zone

作　　者：鲁洪涛 黄维平[2] 刘振宇[2] 郑明 李海峰[3] LU Hong-tao;HUANG Wei-ping;LIU Zhen-yu;ZHENG Ming;LI Hai-feng(Ministry of Natural Resources Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Geological Survey Institute of Jilin Province,Changchun 130102,Jilin,China;Collage of Earth Sciences and Resources,China University of Geosciences Beijing,Beijing 100083,China)

机构地区：[1]中国地质科学院矿产资源研究所成矿作用与资源评价重点实验室,北京100037 [2]吉林省地质调查院,吉林长春130102 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《吉林地质》2020年第1期12-23,共12页Jilin Geology

摘　　要：本文对班戈雪如岩体似斑状二长花岗岩进行了LA-ICP-MS锆石U-Pb定年、微量元素和全岩地球化学研究,探讨了其形成年代、成岩条件和构造背景。结果表明雪如岩体侵位于晚白垩世晚期(76±1 Ma),锆石饱和温度计和锆石Ti温度计计算其成岩温度分别为760~810℃和738~814℃,较低的锆石相对氧逸度反映成岩环境为还原环境。全岩地球化学分析结果显示其具有高硅、富碱和准铝质--弱过铝质特征,大离子亲石元素和LREE富集,高场强元素和HREE相对亏损。雪如岩体是中地壳部分熔融的产物,源区残留相为斜长角闪岩相,岩浆结晶过程中发生角闪石和斜长石的分离作用。地球化学投图结合区域构造演化显示其形成于后碰撞伸展环境,表明班公湖-怒江缝合带中段地区在晚白垩世晚期已经进入后碰撞伸展阶段。The zircon LA-ICP-MS U-Pb dating,zircon trace element and whole rock geochemistry of the Xueru porphyraceous monzonitic granite were conducted to constrain its emplacement age,petrogenesis and tectonic setting.The results indicate that the Xueru plutons emplaced at Upper Late Cretaceous(76±1 Ma),with the diagenetic temperature of 760~810℃average 786℃)and 738~814℃(average 771℃)from zircon saturation geothermometers and T i-in-zircon geothermometers,respectively.The lower oxygen fugaity of zircon indicates the reducing diagenetic environment.The Xueru plutons have characteristics of high silicon,rich alkali and paraluminous-weakly peraluminous,with the enrichment of LILE and LREE,and depletion of HFSE and HREE.The Xueru rocks is the product of partial melting of the middle crust.Residues of magma source are amphibolite facies.The separations of amphibole and plagioclase occured during the crystallization of magma.The Xueru intrusions were formed in the setting of post collision extension,which indicates that the middle of the Bangong Lake-Nujiang suture zone had entered post-collision extension stage in Late Cretaceous.

关 键 词：地质年代学 后碰撞 花岗岩 班公湖-怒江带 

分 类 号：P588.12[天文地球—岩石学]