华南板块中生代构造体制转换的最直接响应:吴川-四会走滑断裂带宏-微观构造解析  

Sensitive corresponding to tectonic transform of South China Block during Mesozoic:A case study on the Wuchuan-Sihui strike-slip fault zone

作　　者：张献河 黄建桦 张波[2] 李出安 王水石 侯照亮 刘佳宁 邱亮[4] ZHANG XianHe;HUANG JianHua;ZHANG Bo;LI ChuAn;WANG ShuiShi;HOU ZhaoLiang;LIU JiaNing;QIU Liang(Guangdong Geological Survey Institute,Guangzhou 510080,China;MOE Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Peking University,Beijing 100871,China;Guangdong Marine Geological Survey Institute,Guangzhou 510080,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Department of Geology,University of Vienna,Vienna 1090,Austria)

机构地区：[1]广东省地质调查院,广州510080 [2]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 [3]广东省海洋地质调查院,广州510080 [4]中国地质大学(北京)地球科学与资源学院,北京100083 [5]维也纳大学地质学系,维也纳1090

出　　处：《岩石学报》2024年第12期3923-3948,共26页Acta Petrologica Sinica

基　　金：广东省地质勘查与城市地质专项(2024-02);国家重点研发计划项目(2021YFA0716001)联合资助。

摘　　要：长度超过500km的吴川-四会走滑断裂带是东亚大陆边缘NE向走滑剪切体系的重要组成,其主要活动时期为中生代,该断裂系统是云开杂岩带的重要边界构造,但其变形特征、运动学和活动时间等仍存争议。宏-微观构造观测表明,吴川-四会断裂带存在右行走滑剪切运动。断裂带内,韧性、脆-韧性以及脆性构造均有出露,剪切带韧性面理主体向北西陡倾,发育近水平线理,存在逆冲运动分量。微观构造和石英CPOs组构特征分析表明,西南段为右行韧性走滑剪切,韧性变形温度约为400~500℃;剪切带向北东方向延伸,逐渐过渡为脆-韧性剪切带和脆性破裂带,剪切变形温度降低为350℃或200℃以下。断裂带内变形和未变形岩浆岩的锆石U-Pb年龄和独居石U-(Th)-Pb年龄限定,右行走滑剪切开始或发生于227Ma或稍早,190~181Ma仍持续剪切;它比该带的左行走滑剪切活动事件(230~220Ma)稍晚或近同期,但早于华南大陆中-晚中生代大规模岩浆活动事件(~180Ma),与古太平洋板块向西斜俯冲诱发的区域E-W向伸展构造的时间基本吻合。结合东亚大陆边缘普遍发生的走滑剪切体系、中生代岩浆活动及其空间展布特征,暗示东亚大陆的构造体制转换始于227Ma或~190Ma,从左行走滑剪切转换为右行走滑剪切,同时形成或诱发一系列NE向右行走滑断层带的再次活动。中生代华南陆内和板缘走滑剪切作用和走滑剪切运动学反转的发生,暗示华南由古特提斯构造体制转变为古太平洋构造体系控制,即板内走滑断裂活动和运动学转变是板缘构造体制转换的最直接结果和快速响应。The ca.500-km-long Wuchuan-Sihui Fault Zone is a major component of the NE striking strike-slip shearing system in the East Asia continental margin,which was active during the Mesozoic.Despite its importance,the kinematics and activity timing along the fault zone remain unclear.Our new observations on structures of this fault zone show that it experienced extensive dextral strike-slip shearing.Ductile,brittle-ductile and brittle structures are well exposed along and within the fault zone in Guangdong Province.The foliation of the shear zone predominantly dips steeply to the northwest and sub-horizontal lineation,and has a minor reverse component of motion.Analysis of microstructures and quartz CPOs suggests that the temperatures of the ductile deformation in this segment are within the range of 400~500℃.The shear zone extends northeastward,gradually transitioning into a brittle-ductile shear zone and a brittle fracture zone,with shear deformation temperatures decreasing to 350℃or below 200℃.Combined with structure investigation data collected from this zone,the in situ zircon U-Pb dating and U-(Th)-Pb monazite of the deformed and undeformed igneous rocks with dextral shearing initiated or occurred at 227Ma or slightly earlier,and continued during 190~181Ma.These new results are later than or the same as the sinistral strike-slip shearing(230~220Ma)along the zone,and slightly earlier than the Middle and Late Mesozoic magmatic activities(~180Ma),which is correlative to the timing of a regional E-W extensional setting/event during the Paleo-Pacific subduction.Our data,combined with previous published studies of this ductile strike-slip shear system in Yunkai terrain and adjacent region,imply that the tectonic transition in East Asia continent was initiated at the Late Triassic(~227Ma)or at the Early Jurassic(~190Ma)from sinistral transpressional setting into the dextral transtensional setting with the synchronous formation of a series of NE striking dextral shear zones or faults.This quick tectonic transition

关 键 词：走滑剪切 运动学反转 中生代 吴川-四会断裂 华南板块 构造体制转换 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学]