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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
投稿时间:2012-08-08  修订日期:2013-01-09  点此下载全文
引用本文:周印章,韩宝福,徐钊,任荣,苏犁.2014.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[J].地质学报,88(1):25-35
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作者单位E-mail
周印章 北京大学地球与空间科学学院 3826788@qq.com 
韩宝福 北京大学地球与空间科学学院  
徐钊 北京大学地球与空间科学学院  
任荣 北京大学地球与空间科学学院  
苏犁 中国地质大学(北京)地学实验中心  
基金项目:国家重点基础研究发展计划(973计划)
中文摘要: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(325~313 Ma)的花岗闪长岩和花岗岩、早二叠世(291~277 Ma)的钾长花岗岩和中细粒花岗岩及早白垩世(~134~130 Ma)的伟晶岩和石英二长岩。第一期构造变形事件为NW-SE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2~10米,并使伟晶岩变形为碎裂岩。
中文关键词:构造岩浆作用  构造解析  锆石U-Pb定年  晚古生代-中生代  NW-SE向伸展
 
Late Proterozoic-Mesozoic Tectonomagmatic Events in the Yingba Area, Western Inner Mongolia, China
NameInstitution
Yin-Zhang ZhouPeking University
Bao-Fu HanPeking University
Zhao XuPeking University
Rong RenPeking University
Li SuThe Geological Lab Center, China University of Geosciences, Beijing
Abstract:In this paper, we focused on the structural and geochronological analyses for the Yingba area in western Inner Mongolia, China. At least three stages of Late Proterozoic to Mesozoic tectonomagmatism have been identified. New and previous zircon U-Pb ages have revealed Carboniferous (325~313 Ma) granodiorite and porphyritic granite, Early Permian (291~277 Ma) alkaline granite and purple red medium-fine grained granite and Early Cretaceous (~134~130 Ma) pegmatite and quartz monzonite. The first tectonic event is characterized by NW-SE compression after the Early Permian (290.9±1.8 Ma), which generated the low-angle NW-dipping gneissic foliations in the granodiorite and alkaline granite. The second event is indicative of NW-SE extension, during which a SE dipping low-angle ductile shear zone, which is characterized by the medium-high temperature (450~650 ºC) mylonite, crosscut the gneissic granodiorite and gneissic alkaline granite, and so it apparently postdated the first tectonic event (<290.9±1.8 Ma). 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 Late Proterozoic to Mesozoic.
keywords:tectonomagmatism  structural analysis  zircon U-Pb dating  Late Proterozoic-Mesozoic  NW-SE extension
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