苏鲁造山带西北缘皇华-铁镢山段韧性剪切变形及年代学研究  

Ductile Shearing Deformation and Geochronological Characteristics of the Huanghua-Tiejueshan Areas in the Northwestern Margin of the Sulu Orogen

作　　者：李磊磊 王宗秀[1] 李春麟[1] 高万里[1] 谭元隆[1] 钱涛[1] 胡俊杰[1] 李会军[1] LI Leilei;WANG Zongxiu;LI Chunlin;GAO Wanli;TAN Yuanlong;QIAN Tao;HU Junjie;LI Huijun(Key Laboratory of Shale oil and Gas Survey, Institute of Geomechanics , Chinese Academy of Geological Sciences, Beijing, 100081;China University of Geosciences （Beijing）, Beijing, 100083)

机构地区：[1]中国地质科学院地质力学研究所,中国地质科学院页岩油气调查评价重点实验室,北京100081 [2]中国地质大学(北京),北京100083

出　　处：《地质学报》2018年第4期722-746,共25页Acta Geologica Sinica

基　　金：中国地质调查项目(编号：1212011120965)资助的成果;中国地质调查项目(编号：DD20189614)联合资助的成果; 国家重点研发计划项目(编号：2016YFC060020); 国家自然科学基金项目(编号：41702204)

摘　　要：苏鲁造山带经历了多期构造事件,现今构造样式复杂多样,位于其西北缘的皇华-铁镢山地区构造变形强烈,且发育呈北东东向展布的韧性剪切带,对韧性剪切带变形特征及年代学的研究有利于加深对苏鲁造山带晚中生代构造演化的认识。本文通过详细地野外调查和显微构造特征研究,对剪切带几何学和运动学进行了分析,并结合构造年代学资料探讨韧性剪切带的构造演化过程。结果显示,研究区韧性剪切带几何学形态表现为背形,在晚侏罗世-早白垩世期间经历了两期韧性变形作用:(1)早期韧性变形是由SEE向NWW近水平的滑脱作用造成,并发育与面理产状一致的伟晶岩脉,其LA-ICP-MS锆石U-Pb谐和年龄为150.1±1.1 Ma,表明早期韧性变形启动时间不晚于150 Ma。(2)晚期韧性变形是由NNW-SSE伸展滑覆造成,同变形期白云母^(40)Ar-^(39)Ar坪年龄为137.09±0.32Ma,与反等时线年龄一致,且侵入剪切带内无变形的闪长玢岩LA-ICP-MS锆石U-Pb谐和年龄分别为123.5±0.8Ma和127.1±1.6Ma,表明晚期韧性变形启动时间不晚于137Ma,并结束于127Ma之前。综合研究区内已有的研究成果,本次研究认为苏鲁造山带西北缘早期韧性变形发生于陆内造山的晚期阶段,而晚期韧性变形发生于造山后的伸展阶段,两期构造活动反映了苏鲁造山带构造体制转换过程,该转换过程与晚中生代中国东部岩石圈的伸展减薄及太平洋板块的俯冲密切相关。Experiencing multi-stage structural events,theSulu orogen currently presents current complex structural styles.The Huanghua-Tiejueshan areas,located in the northwestern margin of the Sulu orogeny,underwent intense structural deformation,and therefore formed an ENE-trending ductile shear zone.Therefore,study of the ductile shearing and geochronological characteristics of ductile shear zone will deepen understanding tectonic evolution of the Sulu orogen in late Mesozoic.In this paper,based on detailed field investigation and microstructure analysis,we analyzed the geometry and kinematic of shear zone and discussed the tectonic evolution of ductile shear zone combined with tectonic chronology.The results suggest that the ductile shear zone was geometrically shaped as an antiform and possibly experienced two stages of ductile shear deformation during the late Jurassic-early Cretaceous.（1）The early ductile deformation resulted from SEE-to NWW-trending near-horizontal detachment,accompanied by formation of pegmatite veins parallel to the attitude of the shear foliation.LA-ICP-MS zircon dating yielded an age of 150.1±1.1 Ma for the veins,indicating that the early ductile deformation initiated no later than 150 Ma.（2）The late ductile deformation was formed due to NNW-SSE trending extension.Simultaneously formed muscovite gives an plateau age of 137.09±0.32 Ma,which is consistent with the inverse isochron age.Moreover,undeformed dioritic porphyrite intruding into the ductile shear zone yields LA-ICP-MS U-Pb ages of 123.5±0.8 Ma and 127.1±1.6 Ma,indicating that the late ductile deformation started no later than 137 Ma and terminated prior to 127 Ma.Taking regional geological data into consideration,this study suggests that the early and late ductile deformation of the northwestern margin of the Sulu orogeny occurred at the late stage of intracontinental orogeny and post-orogenic extension,respectively.Two stages of tectonic activities reflect the tectonic regime transition in the Sulu orogeny.The tectonic regim

关 键 词：韧性剪切带 晚侏罗世-早白垩世 构造体制转换 ^40AR-^39AR年龄 苏鲁造山带 

分 类 号：P542[天文地球—构造地质学]