东昆仑造山带索拉沟地区三叠纪赞岐质闪长岩的成因机制及其对古特提斯造山作用的启示  

Petrogenesis of Triassic Suolagou Sanukitoid-like Diorite in East Kunlun Orogen and Its Implications for Paleo-Tethyan Orogeny

作　　者：王巍 熊富浩[1,2] 马昌前 陈越[1] 黄虎 Wang Wei;Xiong Fuhao;Ma Changqian;Chen Yue;Huang Hu(College of Earth Science,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;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]成都理工大学地球科学学院,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]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2021年第8期2887-2902,共16页Earth Science

基　　金：国家自然科学基金项目(Nos.41602049,41972066)。

摘　　要：具有特殊成因机制的赞岐岩是探究深部岩浆动力学过程与区域构造演化的重要岩石探针之一.以东昆仑索拉沟地区赞岐质闪长岩为研究对象,开展系统的岩石学、年代学、元素地球化学和Lu-Hf同位素分析,厘定其岩石成因,揭示其对古特提斯造山作用的启示.锆石U-Pb年代学分析表明,索拉沟闪长岩形成于中三叠世(~243 Ma).岩石具有较低含量的SiO2(50.26%~57.40%),较高的全碱成分(Na_(2)O+K_(2)O=3.5%~6.3%)、MgO(6.0%~7.1%)和Mg#值(50.1~60.9),属于高镁钙碱性准铝质岩石.索拉沟闪长岩具有较高的Sr(622×10^(-6)~1 041×10^(-6))、Cr(30×10^(-6)~161×10^(-6))和Ni(19×10^(-6)~79×10^(-6))以及中等的Y(7.6×10^(-6)~24.3×10^(-6))和Yb(0.62~1.87)含量,与典型的高镁安山质赞歧岩成分类似.岩石富集轻稀土和大离子亲石元素(如Rb、K和Pb),亏损高场强元素(如Ta、Nb和Zr),具有弧岩浆岩的化学属性.Lu-Hf同位素研究揭示,索拉沟闪长岩起源于富集岩石圈地幔(εHf(t)=-2.4~-0.4,TDM=0.89~0.99 Ga).岩石成因分析表明,东昆仑索拉沟中三叠世赞岐质高镁闪长岩形成于陆缘弧背景,岩浆起源于富集岩石圈地幔,且岩浆经历了以角闪石和黑云母为主的分离结晶作用.中三叠世是东昆仑造山带古特提斯洋壳俯冲和地体碰撞的构造转换阶段,索拉沟赞岐质高镁闪长岩可能是俯冲作用结束时板片断离的岩浆响应.Sanukitoid with special genetic mechanism is one important petrological probe to study the magma dynamic processes and associated tectonic process.In this study,it presents petrology,geochronology,elemental geochemistry and Lu-Hf isotopic data on the Suolagou sanukitoid-like diorite in East Kunlun,aiming to characterize its petrogenesis and to reveal its implications on the Paleo-Tethyan orogeny.Zircon U-Pb dating shows that the Suolagou diorite was formed in the Middle Triassic (~243 Ma).Geochemically,they have low contents of Si O2(50.26%-57.40%),but high contents of total alkaline (Na_(2)O+K_(2)O=3.5%-6.3%),Mg O (6.0%-7.1%) and high Mg#(50.1-60.9),belonging to high magnesium,calc-alkaline and metaluminous series.The Suolagou diorites show geochemical similarities to high Mg#andesitic sanukitoids with high contents of Sr (622×10^(-6)-1 041×10^(-6)),Cr (30×10^(-6)-161×10^(-6)) and Ni (19×10^(-6)-79×10^(-6)),and moderate contents of Y(7.6×10^(-6)-24.3×10^(-6))and Yb(0.62×10^(-6)-1.87×10^(-6)).These rocks display remarkable enrichment in light rare earth elements and large-ion lithophile elements (such as Cs,Rb,K and Pb) but depletion in high-field strength elements (such as Ta,Nb and Zr),resembling the arcrelated magmatic rocks above subduction zone.Lu-Hf isotopes show that the Suolagou diorites were derived from partial melting of enriched lithospheric mantle (εHf(t)=-2.4 to-0.4,TDM=0.89-0.99 Ga).The~243 Ma sanukitoid-like diorite in East Kunlun were formed in a continental arc setting,i.e.,the parent magma derived from partial melting of enriched lithospheric mantle,subsequently followed by fractional crystallization of amphibole and biotite.This study suggests that the transition from Paleo-Tethyan oceanic slab subduction to terranes collision in East Kunlun occurred at Middle Triassic,and the Suolagou sanukitoid-like high-Mg diorites could be the magmatic response to the slab break-off at the end of subduction.

关 键 词：东昆仑 三叠纪 高镁闪长岩 赞岐岩 古特提斯 地球化学 地质年代学 

分 类 号：P581[天文地球—岩石学]