昌宁-孟连结合带中三叠世含放射虫硅质岩地层的古特提斯意义  

Radiolarian Chert Strata in Middle Triassic from Changning-Menglian Suture Zone and Implications for Paleo-Tethys

作　　者：罗亮[1] 谢韬[1] 王冬兵[1] 黄晓明 姜丽莉 李建忠[1] 彭智敏[1] Luo Liang;Xie Tao;Wang Dongbing;Huang Xiaoming;Jiang Lili;Li Jianzhong;Peng Zhimin(Chengdu Center of China Geological Survey,Chengdu 610081,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《地球科学》2020年第8期3014-3027,共14页Earth Science

基　　金：中国地质调查局项目(Nos.DD20190053,DD20160016);国家自然科学基金项目(No.41802031);第二次青藏高原综合科学考察研究项目(No.2019QZKK0702)。

摘　　要：昌宁-孟连结合带中三叠世地层记录了古特提斯洋晚期演化信息,为正确认识古特提斯构造古地理格局提供了重要的解剖窗口.云南省沧源县团结地区原划泥盆系曼信组岩性为硅质岩与泥岩互层夹砂岩层(透镜体),对其中长石砂岩和硅质岩分别开展锆石U-Pb测年和地球化学分析,在限定该地层时代的基础上探讨其古特提斯演化意义.长石砂岩夹层和透镜体碎屑锆石定年显示其时代分别不早于237.8±1.3 Ma和237.7±1.4 Ma,赋存地层区域上可与牡音河组对比.本次中三叠世放射虫硅质岩地层的发现,填补了本区残余盆地沉积记录.该地层中硅质岩的地球化学特征反映其形成于大陆边缘环境,结合其中陆源碎屑岩碎屑组分和副矿物特征,表明古特提斯残余洋盆规模有限.研究区三岔河组磨拉石沉积角度不整合于早期地层之上标志着残余洋盆最终闭合.The Middle Triassic strata in the Changning-Menglian suture zone record the evolution of the Paleo-Tethys Ocean in the late stage,providing an important window for the better understanding of the structure and geography of the Paleo-Tethys.The original Devonian Manxin Formation composed of siliceous,mudstone and sandstone interlayer(lens bodies)in Tuanjie area,Cangyuan County,Yunnan Province.The zircon U-Pb dating of arkose and geochemical analysis of siliceous rocks were carried out,respectively,and the significance of the Paleo-Tethys evolution was explored on the basis of limiting the formation age.Zircon U-Pb dating of arkose lens bodies and interlayers shows that their ages are not earlier than 237.8±1.3 Ma and 237.7±1.4 Ma,respectively,the stratum can be compared with the Muyinhe Formation.The discovery of the Middle Triassic stratum fills the blank of the sedimentary records in this area.Geochemical analysis of the siliceous rock in this stratum indicates that it was formed in the continental marginal environment.Combining with composition of granule in sedimentary rock and para-mineral characteristics,it shows that the scale of the residual oceanic basin of Paleo-Tethys is limited.The angular inconsistency of the molassic-type deposition of the Sanchahe Formation above the early stratum indicates the final closure of the residual ocean basin.

关 键 词：锆石U-Pb年龄 地球化学 含放射虫硅质岩 牡音河组 残留盆地 地质年代学 

分 类 号：P581[天文地球—岩石学]