上覆板块对大陆深俯冲构造响应:以胶辽地区为例  

Tectonic response of overriding plate to the continental deep subduction:Insights from the Jiao-Liao area

作　　者：孟令通 林伟[1,2] 任志恒 杨进辉 李金雁[1] MENG LingTong;LIN Wei;REN ZhiHeng;YANG JinHui;LI JinYan(State Key Laboratory of Lithospheric and Environmental Coevolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,China)

机构地区：[1]中国科学院地质与地球物理研究所,岩石圈演化与环境演变全国重点实验室,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]中国科学院新疆生态与地理研究所,乌鲁木齐830011

出　　处：《岩石学报》2024年第8期2287-2305,共19页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42202241、U2344213);国家重点研发计划(2016YFC0600102);博士后面上基金(2022M713128)联合资助.

摘　　要：在大陆深俯冲形成的超高压造山带中,由于超高压岩石折返构造的强烈改造,板块汇聚过程中的收缩构造难以在造山带内部识别,进而影响了对造山过程的完整认识。上覆板块,由于其构造部位的特殊性,较少受折返构造的影响,较大可能地记录了板块汇聚过程的收缩构造,成为理解板块汇聚过程和演化的关键地区。本文以华南板块大陆深俯冲过程中苏鲁超高压造山带上覆华北大陆岩石圈的构造响应为切入点,以胶辽地区为研究靶区,运用多尺度构造解析的方法,综合前人研究成果开展三叠纪收缩构造的流变学特点研究,结合造山带内部变形特征,探讨苏鲁超高压造山带及其上覆板块构造演化过程和动力学机制。研究结果表明,上覆板块在华南-华北汇聚过程中经历了早期上部向NE剪切的逆冲构造和晚期上部向SW剪切的反冲构造。早期收缩构造表现为胶北地体莱西单元早-中三叠世上部指向NE的韧性变形,辽东地体中-晚三叠世上部指向NE的韧性变形和极性向NE的褶皱-逆冲构造;从南向北,变形层次渐浅,时间渐新。晚期收缩构造主要表现为胶北地体林寺山单元晚三叠世早期上部指向SW的韧性变形和辽东地体层次较浅的上部向SW剪切的反冲构造。综合苏鲁超高压造山带晚三叠世晚期造成超高压变质岩石折返的伸展构造,我们建立了华南-华北板块汇聚的三阶段演化模型。我们认为华南板块的低角度-平板俯冲可能是造成上覆华北板块强烈收缩构造发育的重要原因。此外,华南-华北NE-SW向汇聚,但俯冲板块造山后折返方向为NW-SE向,造就了现今苏鲁超高压造山带的构造格局。The exhumation of ultra-high-pressure metamorphic rocks largely reforms the geometry of the orogenic belt related to continent deep subduction,making it difficult to identify the contractional structures formed during plate convergence.The overriding plate,due to being less influenced by exhumation,is key to understanding the plate convergence.This work focuses on the deformations of the overriding North China block when the South China block deeply subducted beneath the North China block,takes the Jiao-Liao area as the target,carries out the structural analysis,and combines previous results,to understand the tectonic response of the overriding plate.Then,we correlate the deformation events recorded in the subducted and overriding plates to understand the tectonic evolution of the Sulu orogenic belt and its geodynamics.Our study shows that the North China block(overriding plate)experienced Triassic NE-SW contractional tectonics related to the continental collision between the South China block and the North China block:NE-directed thrusting and SW-directed back-thrusting.The first contractional structure is characterized by Early to Middle Triassic top-to-the-NE ductile shearing in the Laixi unit,Jiaobei massif,and Middle to Late Triassic top-to-the-NE ductile shearing,NE-directed folding and thrusting in the Changshan Island and Lüshun-Dalian-Jinzhou area,Liaodong massif.From south to north,the ductile deformation evolves to the brittle-ductile one,and it seems that the deformation timing becomes younger.The second contractional structure is manifested by Late Triassic top-to-the-SW ductile shearing in the Linsishan unit,Jiaobei massif,and SW-directed back-thrusting in the Liaodong massif.Combined with the tectonics events developed in the Sulu orogenic belt,our new structural results allow us to build a three-stage evolution model for the continental collision between the South China block and the North China block.Our model also highlights that the flat-slab subduction of the South China block may account for

关 键 词：大陆深俯冲 上覆板块 三叠纪NE-SW向收缩构造 构造解析 苏鲁超高压造山带 

分 类 号：P542[天文地球—构造地质学]