东昆仑洪水河地区三叠纪花岗岩类的岩石成因及其对古特提斯造山作用的启示  

Petrogenesis of Triassic Hongshuihe Granitoids in East Kunlun:Implications for the Paleo-Tethyan Orogeny

作　　者：李福睿 熊富浩[1,2] 马昌前 赵涵[1,4] 龚婷婷[1,4] Li Furui;Xiong Fuhao;Ma Changqian;Zhao Han;Gong Tingting(College of Earth Science,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu 610059,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation of Ministry of Natural Resources,Chengdu 610059,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]油气藏地质及开发工程国家重点实验室,四川成都610059 [3]中国地质大学地球科学学院,湖北武汉430074 [4]自然资源部构造成矿成藏重点实验室,四川成都610059

出　　处：《地球科学》2024年第2期639-655,共17页Earth Science

基　　金：国家自然科学基金项目(Nos.41602049,41972066);成都理工大学珠峰科学研究计划项目(No.2021ZF11412)。

摘　　要：东昆仑三叠纪岩浆岩的是研究古特提斯造山作用过程的重要探针.对东昆仑洪水河地区花岗岩类开展了详细的岩石学、年代学、地球化学和Sr-Nd同位素研究,探讨其成因机制及动力学背景.锆石U-Pb年代学研究表明,洪水河花岗闪长岩和花岗岩的结晶年龄分别为243.0 Ma±3.3 Ma和244.0 Ma±3.1 Ma.两类岩石均属于准铝质高钾钙碱性I型花岗岩,但花岗闪长岩具有较低的Na_(2)O/K_(2)O比值(0.78~0.96)和较高的Mg#(42~45).岩石均富集大离子亲石元素,亏损高场强元素,且具有富集的Sr-Nd同位素组成[εNd(t=243)=-6.53~-4.99,Isr=0.706871~0.709126].综合分析表明,洪水河地区三叠纪花岗岩类形成于古特提斯洋壳俯冲的陆缘弧环境,岩浆起源于中元代变质杂砂岩的部分熔融,且经历了不同程度的壳幔混合作用和分离结晶作用.研究揭示,古老大陆地壳的重熔与一定量的壳幔混合作用是东昆仑中三叠世大陆地壳的主要演化方式.Triassic magmatic rocks in East Kunlun are the key probe to study the Paleo-Tethyan orogeny.This paper presents a detailed petrological,chronological,geochemical and Sr-Nd isotopic study on the Hongshuihe granitoids in the East Kunlun to constrain their petrogenesis and dynamic setting.Zircon U-Pb chronology shows that the crystallization ages of the granodiorite and granites in the Hongshuihe pluton are 243.0 Ma±3.3 Ma and 244.0 Ma±3.1 Ma,respectively.The studied rocks are metaluminous,high-K calc-alkaline I-type granitoids,but the granodiorites have lower Na_(2)O/K_(2)O ratios(0.78-0.96)and higher Mg^(#)(42-45)than the granites.All rocks are enriched in large ion lithophile elements but depleted in high field strength elements,and have an enriched Sr-Nd isotopic composition[εNd(t)=-6.53~-4.99,Isr=0.706871~0.709126].Comprehensive studies indicate that the Hongshuihe middle Triassic granitoids were formed in the continental arc environment during the East Kunlun Paleo-Tethyan oceanic crust subduction,and their parental magmas were derived by partial melting of Mesoproterozoic metagreywackes followed by varying degrees of crust-mantle mixing and fractional crystallization.This study also shows that the re-working of ancient continental crust with a certain amount of crust-mantle mixing is the main evolutionary mechanism of Middle Triassic continental crust in the East Kunlun.

关 键 词：东昆仑 中三叠世 古特提斯 花岗岩类 岩石成因 岩石学 

分 类 号：P581[天文地球—岩石学]