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东昆中构造带具有复杂的物质组成与结构构造,其中沟里地区出露的原划石炭系浅变质沉积地层是东昆中蛇绿构造混杂岩基质岩系的重要组成部分,其形成时代和属性研究对东昆中构造带研究具有重要意义。运用LA-MC-ICP-MS锆石U-Pb年代学分析方法,对浅变质沉积地层变砂岩碎屑锆石进行详细研究,结果显示,碎屑锆石年龄谱可分为4组:(1)加里东期(499~565Ma)。(2)新元古代中期至早期(693~969Ma)。(3)古元古代晚期—中元古代中期(1254~1967Ma)。(4)新太古代—古元古代早期(2348~2776Ma)。结合前人研究资料认为浅变质沉积地层形成时间在427~499Ma,应归属于早古生代纳赤台岩群变沉积岩。其沉积物源以新元古代早期至中期响应Rodinia超大陆汇聚、裂解的物质记录及新太古代—元古代结晶基底为主,少量东昆仑地区加里东期与原特提斯洋扩张俯冲相关岩浆岩。东昆中构造带沟里地区基质地层主要是早古生代纳赤台岩群变沉积岩,而不是前人认为的石炭纪地层。东昆中构造带主要构造活动在早古生代末期就已经基本完成。
The structural belt in the East Kunlun area has complex material composition and structural structure. The original Carboniferous super-metamorphic sedimentary layer exposed in the ditch area is an important part of the mafic rock series in the Middle East. The formation time and Attribute research is of great significance to the study of the tectonic belts in East Kunming. The zircon zircon U-Pb dating from LA-MC-ICP-MS was used to study the detrital zircons from the metamorphic sedimentary rocks. The results show that the detrital zircon ages can be divided into four groups: (1 ) Caledonian period (499 ~ 565Ma). (2) Neoproterozoic metaphase to early period (693 ~ 969Ma). (3) Late Palaeozoic - Mesoproterozoic (1254 ~ 1967Ma). (4) Neo-Archean - Early Proterozoic (2348 ~ 2776Ma). According to the previous research data, the formation time of the shallow metamorphic sedimentary strata is 427 ~ 499Ma, which should be attributed to the Paleozoic Nadaitai rock group. The sediments were mainly from the Neoproterozoic to mid-Rodinian supercontinent convergence and pyrolysis, and the Neoproterozoic-Proterozoic crystalline basement. A small amount of Caledonian Eastern Proterozoic expansive and subducted magmatism rock. The basement strata in the structural belt with ditch in East Kunlun are mainly metamorphic sedimentary rocks of the Early Paleozoic Nachitai Group instead of the predecessor Carboniferous strata. The main tectonic activities in the eastern Kunqu structural belt have been basically completed in the late Paleozoic.