中国东南部黄山运动及其花岗质岩浆活动与成矿作用  

Huangshan Movement in SE China and its granitic magmatism and mineralization

作　　者：汪相[1] WANG Xiang(School of Earth Sciences and Engineering,Nanjing University,Nanjing,210023)

机构地区：[1]南京大学地球科学与工程学院,南京210023

出　　处：《地质论评》2022年第5期1677-1728,共52页Geological Review

基　　金：国家自然科学基金资助项目(编号:41872047)的成果。

摘　　要：中国东南部存在着一系列早白垩世中—晚期Ⅰ型花岗岩与A型花岗岩复合在一起的北东向岩带。本研究选取这些岩带中的苏州、黄山、灵山和福州Ⅰ型花岗岩与A_(2)型花岗岩组合的复式岩体,对它们开展岩相学、岩石化学和锆石学的系统研究,从而首次确定:(1)作为复式花岗岩体中主体相的岩性为(含普通角闪石)黑云母二长花岗岩(为典型的I型花岗岩),由弱分异的壳源花岗岩浆结晶而成,其锆石U-Pb年龄的平均值为127.1±1.8 Ma,代表同造山花岗岩的定位年龄;(2)作为复式花岗岩体中补体相的岩性为铁锂云母/白云母碱长花岗岩(为典型的A_(2)型花岗岩),由与主体花岗岩同源的高分异花岗岩浆结晶而成,其锆石U-Pb年龄的平均值为105.4±1.3 Ma,代表造山后花岗岩的定位年龄;(3)与这些复式花岗岩体伴生的岩浆热液矿床中的锆石U-Pb年龄的平均值为106.4±2.3 Ma,代表中国东南部一次大规模成矿作用的时代。结合上述研究结果、中国东南部构造地质资料和花岗岩浆活动及其成矿作用的年代学数据,笔者认为,库拉板块于早白垩世初期向欧亚大陆的俯冲作用引起中国东南部地壳深部I型花岗岩浆房的形成和部分I型花岗岩浆上升定位;挤压高峰后,深部岩浆房中巨量的Ⅰ型花岗岩浆开始漫长的分离结晶作用,导致岩浆房上部出现高度富集成矿物质的残余岩浆;至早白垩世末期,中国东南部的构造环境进入伸展高峰期,深部岩浆房中高度分异的、体量极小的残余岩浆沿着张性断裂被动侵位;由于压力和温度的骤减,上升过程中的残余花岗岩浆发生流体—熔体溶离作用而分解为含大量成矿物质的硅质流体和碱性过铝质熔体,前者形成石英脉型矿床(或云英岩型/矽卡岩型矿床),后者形成A_(2)型花岗岩。造成中国东南部上述花岗质岩浆活动及其成矿作用的驱动力来源于一次新的造山作用——笔者A series of NE trending middle—late Early Cretaceous Ⅰ-type and A-type granites expose in SE China.This study investigates the Suzhou,Huangshan,Lingshan and Fuzhou Ⅰ-type and A_(2)-type granitic complexes in the belt for their petrographic,geochemical and zirconological characteristics.The work summarizes:(1)The(amphibole-bearing) biotite monzogranite,as a main intrusive phase of the granitic complexes,was formed from weakly fractionated granitic magma in the upper crust.This rock is typical I-type granite with zircon U-Pb age of 127.1±1.8 Ma,representing the emplacement time of syn-orogenic granite;(2)The zinnwaldite/muscovite alkali-feldspar granite formed as a subsequent intrusive phase of through the crystallization of highly fractionated granitic magma of the same origin.The rock is typical A_(2)-type granite with zircon U-Pb age of 105.4±1.3 Ma,representing the emplacement time of post-orogenic granite;(3)Ores correlated to these granitic complexes formed magmatic—hydrothermal deposits with zircon U-Pb age of 106.4±2.3 Ma,representing the time of a large-scale of mineralization in SE China.Combing the structural geology,geochronology of granitic magmatism,and the correlated mineralization in SE China,this study proposes that the subduction of the Kula plate under the Euro—Asiatic continent in the early period of Early Cretaceous caused crustal thicking,thrust faults,and anatexis in SE China.Magma chamber developed in the middle—lower crust and Ⅰ-type granites intruded in the upper crust as a main intrusive phase of the granitic complexes.After zenith of compressional subduction,the regional tectonic environment changed from compression to relaxation in SE China,Ⅰ-type granitic magma in deep-seated chamber underwent a long period of fractional crystallization and generated ore-forming material enriched residual magma at top of magma chamber.At the ending period of Early Cretaceous,the regional tectonic environment entered the extensional regime in SE China.The shearing—compressive faults

关 键 词：Ⅰ型花岗岩 A_(2)型花岗岩 复式花岗岩体 岩浆热液矿床 黄山运动 中国东南部 

分 类 号：P588.121[天文地球—岩石学] P612[天文地球—地质学]