印支造山带:Song Chay构造带  

Indosinian orogenic belt:Song Chay tectonic belt

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作  者:林伟[1,2] 王印 刘飞 孟令通[1,2] 吴钦颖 郭钊 李金雁 LIN Wei;WANG Yin;LIU Fei;MENG LingTong;WU QinYing;GUO Zhao;LI JinYan(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Geosteering&Logging Research Institute,Sinopec Matrix Corporation,Qingdao 266071,China;Wuhan Center of China Geological Survey,Wuhan 430205,China)

机构地区:[1]岩石圈演化国家重点实验室,中国科学院地质与地球物理研究所,中国科学院地球科学研究院,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]中石化经纬有限公司地质技术测控技术研究院,青岛266071 [4]中国地质调查局武汉地质调查中心,武汉430205

出  处:《岩石学报》2024年第1期1-28,共28页Acta Petrologica Sinica

基  金:国家自然科学基金项目(91855212、U2344213);岩石圈演化国家重点实验室项目(SKL-Z202205)联合资助.

摘  要:印支运动是二十世纪初法国地质学家根据越南北部晚三叠世大规模角度不整合所提出。越南北部的Song Chay构造带作为印支造山带概念的提出地,记录了大量经典的印支造山相关的信息,是理解印支造山带构造演化的关键地区。本文在课题组对Song Chay地区十多年研究基础上,结合前人研究成果,系统厘定了Song Chay构造带的几何空间格架、运动学特征及其演化过程。详细的野外地质考察表明,Song Chay构造带从SW向NE依次可以划分成:新生代的大象山单元、代表缝合带的Song Chay蛇绿混杂岩单元,以及越南东北部褶皱冲断系统。其中蛇绿混杂岩单元和褶皱冲断系统中发育NE-SW向矿物拉伸线理,并具有顶部向NE方向的剪切变形特征,指示了Song Chay洋壳向SW的俯冲以及向NE的逆冲过程。精确的年代学工作表明,Song Chay蛇绿混杂岩中斜长花岗岩的结晶年龄为356.4±2.9Ma,表明至少在早石炭世Song Chay洋就已经形成了成熟的大洋地壳。褶皱冲断带内部的低温年代学数据约束了顶部向NE的剪切变形年龄在250~245Ma之间,表明为华南和印支板块碰撞时间。另外,Song Chay蛇绿混杂岩基质中碎屑锆石物源研究表明,Song Chay蛇绿混杂岩基质中碎屑锆石主要是来自于俯冲的华南板块,只有很少一部分来自印支板块,因此推测Song Chay洋可能为一个十分有限的小洋盆。构造几何学、运动学以及碎屑锆石物源研究表明,在Song Chay构造带内的“滇-琼缝合带”两侧构造特征可对比,并未因“滇琼洋”的闭合而造成差异。因此,我们认为“滇-琼缝合带”并不能代表一个大洋。根据我们及前人的构造学、岩石学、年代学工作,建立了一个初步的Song Chay洋从晚石炭世至中三叠世的构造演化模型:(1)310~270Ma,Song Chay洋开始向SW俯冲到印支板块之下,此时岩浆弧并不发育,蛇绿混杂岩物源主要为华南板块;(2)270~250Ma,Song Chay洋Based on the large-scale Late Triassic angular unconformity in northern Vietnam,French geologists proposed the Indosinian Movement in the early 20 th century.The Song Chay tectonic belt in northern Vietnam,where the Indosinian orogeny was named,records a lot of information about the classical Indosinian orogenic belt and is the key area to understanding its tectonic evolution.According to our ten-year work on the Song Chay area and previous research results,this paper systematically reviews the geometry,kinematics,timing and evolution of the Song Chay tectonic belt.Detailed field work shows that the Song Chay tectonic belt can be divided into the Cenozoic Day Noi Con Voi unit,the Song Chay ophiolitic mélange unit and the NE Vietnam fold and thrust unit from SW to NE.In the ophiolitic mélange unit and the fold and thrust unit,NE-SW mineral and stretching lineations with top-to-the-NE kinematics indicate a SW-ward subduction and the corresponding NE-ward thrust of the Song Chay Ocean crust.Precise geochronological work shows that the crystallization age of the plagiogranite in the ophiolitic mélange unit is 356.4±2.9Ma,indicating that the Song Chay Ocean opened before the Early Carboniferous.The low-temperature geochronological data in the fold and thrust unit constrain the top-to-the-NE shearing between 250Ma and 245Ma,indicating the collision timing of 250~245Ma.In addition,the detrital zircons of the Song Chay ophiolitic mélange matrix were sourced from the downgoing South China block,and only a few ones were derived from the overriding Indochina block,so the Song Chay Ocean may be a very limited ocean basin.Structural analysis and detrital zircon dating suggest that the geometry and kinematics on both sides of the“Dian-Qion suture zone”are the same.Therefore,the“Dian-Qion suture zone”is hardly interpreted as a suture zone.Based on our and previous works in structural geology,petrology and geochronology,we proposed a tectonic evolution model of the Song Chay Ocean from Late Carboniferous to Middle T

关 键 词:印支运动 Song Chay构造带 构造解析 碎屑锆石 滇-琼缝合带 

分 类 号:P541[天文地球—构造地质学]

 

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