宗务隆构造带生格地区土尔根大坂组碎屑锆石年代学及其地质意义

Detrital zircon geochronology and its geological significance from Turgendaban formation in Shengge area of Zongwulong structural belt

宗务隆构造带,是一个发育于南祁连造山带之上的晚古生代-中生代的构造带,总体呈北西西向展布。对宗务隆群物质来源和沉积时代还存在不同认识,通过对宗务隆构造带中生格地区的土尔根大坂组微晶大理岩开展岩石地球化学和碎屑锆石年代学的研究,认为土尔根大坂组中的微晶大理岩原岩以陆源为主,伴有热水沉积作用,为海相-陆表海相沉积型石灰岩。沉积物源应当是构造带南侧为主的陆源剥蚀,北侧可能也有部分物源供给,并含有部分热水沉积。微晶大理岩的沉积时代晚于206 Ma,宗务隆群总体是一套弧前体系,在后期的闭合过程中,形成叠瓦状的俯冲增生楔,其时代应在早泥盆-晚三叠(D1-T3)之间。

The Zongwulong structural belt is a late paleozoic-mesozoic structural belt developed on the south Qilian orogenic belt,which is generally distributed in the NW direction.There are different understandings on the material source and sedimentary age of Zongwulong group.Based on the study of petrochemistry and detrital zircon geochronology of the microcrystalline marble of the Tuergendaban formation in Shengge area of Zongwulong structural belt,it is considered that the original rock of microcrystalline marble in Tuergendaban formation is mainly terrigenous,accompanied by hydrothermal sedimentation,which is marine epicontinental marine sedimentary limestone.The sediment source should be the continental erosion mainly in the south of the structural belt,and there may also be some provenance in the north side,and some hot water deposits during the sedimentation.The sedimentary age of the microcrystalline marble is later than 206 Ma.The Zongwulong group is generally a set of forearc system.In the late closure process,imbricate subduction accretion wedges were formed,and their ages should be between early devonian and late triassic.