藏东吉塘变质核杂岩组成及大地构造意义  

Composition and tectonic significance of Jitang metamorphic core complex in eastern Xizang

作　　者：冯翼鹏 王书来[1] 王根厚[2] 李典 刘函 鲁扬 唐宇 张培烈 韩宁 FENG Yipeng;WANG Shulai;WANG Genhou;LI Dian;LIU Han;LU Yang;TANG Yu;ZHANG Peilie;HAN Ning(Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China;Chengdu Center,China Geology Survey(Geosciences Innovation Center of Southwest China),Chengdu 610218,China;Rock Analysis Laboratory,Regional Geology Survey Institute of Hebei Province,Langfang 065099,China)

机构地区：[1]北京矿产地质研究院有限责任公司,北京100012 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]成都理工大学地球科学与资源学院,四川成都610059 [4]中国地质调查局成都地质调查中心(西南地质科技创新中心),四川成都610218 [5]河北省区域地质调查院,河北廊坊065099

出　　处：《沉积与特提斯地质》2024年第4期854-870,共17页Sedimentary Geology and Tethyan Geology

基　　金：国家自然科学基金项目(42172259);中国地质调查局地质调查项目(DD20190617,DD20221635)。

摘　　要：吉塘变质核杂岩是研究北澜沧江缝合带构造演化过程的重要窗口。本文通过对吉塘变质核杂岩进行构造岩性填图、构造解析及锆石U-Pb测年,将变质核杂岩自上而下解析为沉积盖层、韧性流变层及核部变质杂岩的“三元结构”,核部变质杂岩与韧性流变层之间以韧性拆离带相连,拆离带具有上盘向南东方向剪切的运动学特征。吉塘变质核杂岩中同剪切花岗质糜棱岩的锆石U-Pb年龄为(33.0±1.2)Ma^(28.4±0.6)Ma,剪切后脉体的锆石U-Pb年龄为(18.35±1.2)Ma。综合以上研究结果,推测吉塘变质核杂岩新生代的隆升过程为:强烈的走滑断层活动形成了拉分盆地,其伸展环境使地壳减薄,大量岩浆上涌,最终导致了吉塘变质核杂岩于渐新世—中新世的隆升。吉塘变质核杂岩为渐新世—中新世大型走滑断层作用导致的区域性造山后伸展及大规模南东向逃逸构造事件的产物。The Jitang metamorphic core complex is a key window for studying the tectonic evolution of the northern Lancangjiang zone.In this paper,through the study of structural lithology mapping,structural analysis,and zircon U-Pb dating,the Jitang metamorphic core complex is dissected from top to bottom into the upper unit(low-grade metamorphic or unmetamorphic sedimentary sequence),the middle unit(schists and phyllites),and the lower unit(gneiss core).The lower unit(gneiss core)and the middle unit are connected by a ductile detachment shear zone,with the shear sense of the ductile shear zones indicating southeastern shearing of the upper plate.The zircon U-Pb age of syn-tectonic granitic mylonite in the Jitang metamorphic core complex ranges from(33.0±1.2)Ma to(28.4±0.6)Ma,and that of the post-tectonic vein is(18.35±1.2)Ma.It is speculated that the Cenozoic uplift process of the Jitang metamorphic core complex is as follows:strong strike-slip fault activity leads to the formation of a pull-apart basin,whose extensional environment leads to crustal thinning and a large amount of magma upwelling.Finally,this process resulted in the uplift of the Jitang metamorphic core complex during the Oligocene-Miocene.It is concluded that the Jitang metamorphic core complex is the product of a regional post-orogenic extension and a large-scale south-east trending escape tectonic event caused by the Oligocene-Miocene large-scale strike-slip faulting.

关 键 词：藏东 吉塘变质核杂岩 韧性拆离带 锆石U-PB测年 花岗质糜棱岩 

分 类 号：P588.3[天文地球—岩石学] P542[天文地球—地质学]