琼东南盆地二叠纪-三叠纪长英质岩浆作用:对南海北部陆缘构造属性与演化过程的启示  

Permian-Triassic felsic magmatism in the Qiongdongnan Basin:Implications for the tectonic properties and evolution of the northern continental margin of the South China Sea

作　　者：徐长贵[1] 侯明才[2] 吴克强 熊富浩 尤丽 李成祥 王文博 XU ChangGui;HOU MingCai;WU KeQiang;XIONG FuHao;YOU Li;LI ChengXiang;WANG WenBo(China National Off shore Oil Limited Corporation,Beijing 101000,China;Chengdu University of Technology,Chengdu 610059,China;China National Off shore Oil Limited Corporation-Hainan,Haikou 570100,China)

机构地区：[1]中国海洋石油有限公司,北京101000 [2]成都理工大学,成都610059 [3]中海石油(中国)有限公司海南分公司,海口570100

出　　处：《岩石学报》2024年第8期2450-2468,共19页Acta Petrologica Sinica

基　　金：中海石油(中国)有限公司科技项目(KJZH-2021-0003-00)资助。

摘　　要：琼东南盆地发育二叠纪-三叠纪岩浆岩类,为研究南海北部陆缘古构造属性与大地构造演化过程提供了岩石探针。本文以基底长英质岩浆岩为研究对象,开展岩石学、锆石U-Pb年代学、岩石地球化学和锆石Lu-Hf同位素研究,探讨琼东南盆地二叠纪-三叠纪岩浆岩的时空分布、岩石成因及动力学背景。LA-ICP-MS锆石U-Pb年代学表明,琼东南盆地发育二叠纪-早三叠世、中三叠世和晚三叠世三期长英质岩浆作用(271~217Ma),且岩浆活动具有自南向北迁移的趋势。岩石地球化学分析揭示,二叠纪-早三叠世长英质岩具有较低的FeO/MgO和10000×Ga/Al比值,且强烈亏损Zr、Hf、Nb、Ta等元素,属于典型的陆缘弧I型花岗岩类;中三叠世和晚三叠世岩浆岩均具有较高的SiO_(2)、Mg^(#)、10000×Ga/Al和FeO/MgO比值,大多属于A型花岗岩类。同时,二叠纪-早三叠世长英质岩具有较低的Hf同位素组成(ε_(Hf)(t)=-7.61~-0.65),而中-晚三叠世长英质岩则大多具有较高的Hf同位素组成。岩石成因分析揭示,二叠纪-早三叠世I型花岗岩类起源于古老陆壳的部分熔融,而中三叠世和晚三叠世A型花岗岩类则部分起源于古老长英质地壳熔融,部分则起源于新生地壳熔融,并伴随有壳幔相互作用。综合分析表明,二叠纪-三叠纪期间南海北部陆缘主要受控于古特提斯造山作用控制,且先后经历了二叠纪至早三叠世的古特提斯洋壳俯冲、中三叠世印支板块与华南板块碰撞以及晚三叠世碰撞后伸展等动力学过程。The large-scale Permian-Triassic magmatic rocks in the Qiongdongnan Basin provide a probe for studying the paleotectonic properties and evolution processes of the northern continental margin of the South China Sea.This study focuses on the felsic magmatic rocks,and conducts research on the petrology,zircon U-Pb geochronology,whole-rock geochemistry,and zircon Lu-Hf isotope,aiming to explore the spatiotemporal framework,petrogenesis,and dynamic background of the Permian-Triassic magmatic rocks in the Qiongdongnan Basin.LA-ICP-MS zircon U-Pb geochronology indicates three episodic felsic magmatism occurred in the Qiongdongnan Basin(271~217Ma),i.e.,Permian-Early Triassic,Middle Triassic,and Late Triassic,exhibiting a migration trend from south to north.The Permian-Early Triassic felsic rocks have low FeO/MgO and 10000×Ga/Al ratios with strongly depleted elements such as Zr,Hf,Nb,Ta,etc.,belonging to the typical I-type granites in continental margin arc.The Middle Triassic and Late Triassic felsic rocks have high SiO_(2),Mg^(#),10000×Ga/Al,and FeO/MgO ratios,mostly belonging to A-type granites.Besides,the Permian-Early Triassic felsic rocks have low Hf isotopes(ε_(Hf)(t)=-7.61~-0.65),while the Middle to Late Triassic felsic rocks have high Hf isotopes.Petrogenesis study reveals that the studied Permian-Early Triassic I-type granites were derived the partial melting of ancient crustal rocks,while the Middle Triassic and Late Triassic A-type granites either originated from the melting of the ancient felsic continental crust,or sourced from the juvenile crust or crust-mantle interaction.Comprehensive study shows that the northern continental margin of the South China Sea was mainly controlled by the Paleo-Tethys orogeny during the Permian-Triassic Period,and underwent dynamic processes such as the Paleo-Tethys oceanic subduction in the Permian-Early Triassic,the collision between the Indosinian and South China plates in the Middle Triassic,and post-collisional extension in the Late Triassic.

关 键 词：琼东南盆地 二叠纪-三叠纪 长英质岩 岩石成因 构造演化 古特提斯 

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