内蒙古西部英巴地区晚古生代-中生代构造岩浆事件及其地质意义  

Late Paleozoic-Mesozoic Tectonomagmatic Events in the Yingba Area, Western Inner Mongolia,China,and Its Geological Implications

作　　者：周印章[1] 韩宝福[1] 徐钊[1] 任荣[1] 苏犁[2] 

机构地区：[1]教育部造山带与地壳演化重点实验室,北京大学地球与空间科学学院,北京100871 [2]中国地质大学(北京)地学实验中心,北京100083

出　　处：《地质学报》2014年第1期25-35,共11页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划(“973”项目)(编号2013CB429800);国家自然科学基金项目(编号90714006);中国地质调查局项目(编号1212010611803,1212010611817和1212011120135)资助的成果

摘　　要：本文以内蒙古西部英巴地区一个典型剖面为例，开展了详细的构造解析和年代学研究，初步构建这一地区晚古生代中生代的构造岩浆事件框架。这一地区至少发育三期岩浆活动和三期构造变形事件。锆石U—Pb定年结果和前人的资料显示，三期岩浆活动分别为石炭纪（325～313Ma）的花岗闪长岩和花岗岩、早二叠世（291～277Ma）的钾长花岗岩和中细粒花岗岩及早白垩世（约134～130Ma）的伟晶岩和石英二长岩。第一期构造变形事件为NWSE向挤压，发生在早二叠世之后，使花岗闪长岩和钾长花岗岩发生挤压变形，形成主体低角度北西倾的片麻理，局部发育同期褶皱，变形温度为450～600℃；第二期为NW—SE向伸展，大致发生在早白垩世，使片麻状花岗闪长岩和片麻状钾长花岗岩发生中高温（450-650℃）的糜棱岩化作用，形成南东倾的低角度韧性剪切带，具有正断性质，后被伟晶岩脉切穿。第三期为NW—SE向伸展，发生在早白垩世之后，形成北西倾的中角度脆性正断层，断距2～10m，并使伟晶岩变形为碎裂岩。In this study, one typical profile was selected to perform the structural and geochronological analyses in the Yingba area in western Inner Mongolia, China. At least three tectonomagmatic events during Late Paleozoic to Mesozoic in this area were identified and preliminarily constructed. Previous data and zircon U-Pb dating results in this study have revealed three tectonomagmatic events resulted in granodiorite and porphyritic granite in Carboniferous （325-313 Ma）, alkaline granite and purple red medium-fine grained granite in Early Permian （291-277 Ma） and pegmatite and quartz monzonite in Early Cretaceous （ab. 134 -130 Ma）. The first deformation event, characterized by NW--SE compression occurring after the Early Permian （290.9±1.8 Ma）, generated the low-angle NW-dipping gneissic foliations in the granodiorite and alkaline granite. Deformation temperature was 450 - 600℃. The second event, extending NW--SE and occurring at Early Cretaceous, generated a SE dipping low-angle ductile shear zone, which is characterized by the medium-high temperature （450-650 ℃） mylonite. The ductile shear zone is crosscut by the -134 Ma pegmatite veins, indicating that the extension occurred before the Early Cretaceous pegmatite veins. The third tectonic event is represented by NW-dipping moderate-angle brittle normal faults, which resulted from NW--SE extension after the Early Cretaceous and crushed the -134 Ma pegmatite into cataclasite. The Yingba area has recorded a typical process from the formation of an orogen to intracontinental extension during Irate Proterozoic to Mesozoic.

关 键 词：构造岩浆作用 锆石U—Pb定年 晚古生代中生代 

分 类 号：P546[天文地球—构造地质学]