白垩纪羌塘地体西南缘的陆-陆碰撞:来自班怒带西段的花岗岩约束  

Continent-continent collision at the southwestern margin of the Cretaceous Qiangtang terrane:Constraints from granite in the western Bangong-Nujiang Suture Zone

作　　者：付顺[1,3] 赵应权[2] 王进军 余瑜[2] 朱迎堂 傅星喆 FU Shun;ZHAO Yingquan;WANG Jinjun;YU Yu;ZHU Yingtang;FU Xingzhe;无(Sichuan Provincial Key Laboratory of Mathematical Geology,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;College of Mathematics and Physics,Chengdu University of Technology,Chengdu 610059,China;No.283 Team,Sichuan Geological Bureau,Dazhou 635099,China;Hainan Geological Bureau,Haikou 570206,China;Hope College,Southwest Jiaotong University,Chengdu 610400,China)

机构地区：[1]成都理工大学数学地质四川省重点实验室,四川成都610059 [2]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [3]成都理工大学数理学院,四川成都610059 [4]四川省核工业地质局二八三大队,四川达州635099 [5]海南省地质局,海南海口570206 [6]西南交通大学希望学院,四川成都650059

出　　处：《地学前缘》2022年第2期416-430,共15页Earth Science Frontiers

基　　金：国家科技基础资源调查专项“第二次青藏高原综合科学考察研究(2019QZKK0803)”项目。

摘　　要：羌塘地体西南缘布木错—雄巴日—羌多—赛登地区分布着大量呈岩株或岩枝状的中酸性基性侵入岩,其岩石地球化学特点是低SiO_(2)(67.99%~73.32%)、高Al_(2)O_(3)(12.82%~15.02%),属于过铝质花岗岩,里特曼指数(2.09~2.63)σ<3.3,属钙碱性花岗岩类;稀土元素显示为轻稀土较强富集和重稀土强亏损的特征,岩浆结晶分异程度较高。岩石地球化学特征和稀有元素特征图解指示花岗岩构造环境有一定的差异性,以I型为主,其形成及侵位应与古特提斯洋的闭合、新特提斯洋的扩张有关,属同碰撞型造山花岗岩。通过对该区多个花岗岩体锆石LA-ICPMS测定,测得其形成年代为116~107 Ma,与早白垩世晚期羌塘地体南缘的陆陆碰撞作用时间相吻合。A large number of moderately felsic to basic intrusive rocks in the forms of rock strains or rock branches are distributed in the southwestern margin of the Qiangtang terrane.These intrusive rocks are characterized by petrographic analysis as peraluminous granite with low SiO_(2)(67.99%73.32%)and high Al_(2)O_(3)(12.82%15.02%)contents,and defined as calc alkaline based on the Ritmann serial indices of 2.092.63(σ<3.3).They show strong enrichment of light rare earth elements(REE)and strong depletion of heavy REE,with a high degree of magma crystallographic differentiation.The geochemical characteristics of the rocks and REE in granite indicate its tectonic environment is mainly type I,with some variability,and its formation and intrusion should be related to the closure of the ancient Tethys Ocean and the expansion of the new Tethys Ocean,which suggests an intracontinental collisional orogenic granite origin.The zircon laser ablation inductively coupled plasma-mass spectrometry(LA-ICPMS)dating of several granite masses in this area yielded a formation age of 107116 Ma,which is consistent with the time of continent-continent collision at the southern margin of the Qiangtang terrane in the late Early Cretaceous.

关 键 词：白垩纪 羌塘地体 班怒带 陆陆碰撞 花岗岩 

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