河南商城地区石门冲组时代归属及其构造背景  

AGE OF THE SHIMENCHONG FORMATION IN SHANGCHENG AREA OF HENAN PROVINCE AND ITS TECTONIC SETTING

作　　者：魏星[1] 李双应[1] 谢伟 柴广路 程成[1] WEI Xing;LI Shuang-ying;XIE Wei;CHAI Guang-lu;CHENG Cheng(College of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009)

机构地区：[1]合肥工业大学资源与环境工程学院

出　　处：《地层学杂志》2019年第2期219-226,共8页Journal of Stratigraphy

基　　金：中国地质调查局(12120113094300);安徽省公益性地质工作项目(2014-g-9);国家自然科学基金项目(41172097)共同资助

摘　　要：分布于桐柏-大别造山带北缘的石门冲组,由一套片岩、石英岩、大理岩等变质岩系组成,厚约1000 m。该地层的时代、构造归属一直存在较大争议。通过岩石组合、碎屑锆石同位素年代学和地球化学研究,进一步明确了石门冲组地层时代,恢复了原岩类型和沉积环境。最年轻的碎屑锆石年龄为449±12 Ma(YSG),表明石门冲组属于上奥陶统凯迪阶(钱塘江阶)。原岩主要为石英砂岩-长石砂岩-岩屑砂岩-页岩-白云岩组合,形成于滨-浅海环境。碎屑锆石最小年龄、年代相和沉积环境可以与佛子岭群下部祥云寨组相对比,应该属于原商城群的一部分。石门冲组形成于被动大陆边缘构造背景,物源区主要为类似于北秦岭奥陶纪岛弧、新元古代的扬子基底以及秦岭地块的中元古代基底等。Shimenchong Formation in the northern margin of the Tongbai-Dabie orogenic belt is composed of a series of metamorphic rocks such as schist, quartzite and marble, which is about 1000 m thick. However, there has been a great deal of controversy about the age and structural attribution of the formation. Through the study of rock assemblages, detrital zircon geochronology and geochemistry, this paper further confirms the stratigraphic age of the Shimenchong Formation, and has restored its protolith types and sedimentary environments.The youngest detrital zircon age is 449±12 Ma(YSG), indicating that the Shimenchong Formation belongs to the Upper Ordovician Katian. The protolith is mainly composed of quartz sandstone-feldspar sandstone-lithic sandstone-shale-dolomite, which was formed in littoral environment. The minimum age of detrital zircon, facies and sedimentary environment of the Shimenchong Formation can be compared with the Xiangyunzhai Formation of Fozilin Group, which should be a part of the original Shangcheng Group. Shimenchong Formation formed in the tectonic setting of passive continental margin with the sediments from the Ordovician island arc of the North Qinling area, Neoproterozoic basement of the Yangtze Block and Middle Proterozoic basement of the Qinling massif, etc.

关 键 词：锆石年代学 构造背景 石门冲组 晚奥陶世 桐柏-大别造山带 河南 

分 类 号：P534.42[天文地球—古生物学与地层学]