ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    东昆中构造带沟里地区浅变质地层碎屑锆石UPb年龄及其地质意义

    Detrital Zircon U-Pb Age and Geological Significance of Metamorphic Strata at Gouli Area in the Central Tectonic Belt of East Kunlun

    • 摘要: 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(1 254~1 967Ma)。④新太古代-古元古代早期(2 348~2 776Ma)。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。

       

      Abstract: The composition and structures of the central tectonic belt in East Kunlun are very complicated, and the low metamorphic strata in Gouliarea serve as important parts of the central tectonic belt, so the study on the formation age, properties and sedimentary source of these metamorphic strata has important geological significances. In this paper, the metamorphic sandstone samples from the metamorphic strata in Gouli Area have been selected as the research objects, the detrital zircon LA-MC-ICP-MS U-Pb geochronology analysis has been conducted. Detrital zircon U-Pb age spectrum of the sandy slate samples can be divided into four groups:①The Caledonian (499~565 Ma). ②The Early-Middle Neoproterozoic (693~969Ma). ③Late Paleoproterozoic-the middle Mesoproterozoic (1 254~1 967Ma). ④The Neoarchean-early Paleoproterozoic (2 348~2 776Ma).The age group information indicates that, the formation ages of low metamorphic strata vary from 427Ma to 499Ma, belonging to the meta-sedimentary rocks of Early Paleozoic Naij Tal Group-complex. The sedimentary sources of epimetamorphic strata might response to the convergence and cracking of Rodinia supercontinent during Early-Middle Neoproterozoic, which were mainly sourced from the Neoarchean-Proterozoic crystallization basement, with few of them were came from the Caledonian magmatic rocks related to the the extention and subduction of the Proto-Tethys ocean in East Kunlun region. Therefore, the matrix strata of Gouli area in the central tectonic belt may be the meta-sedimentary rocks of Early Paleozoic Naij Tal Group-complex, which is different to the Carboniferous strata classified by the predecessors, and the main tectonic activities of the central tectonic belt had basically completed in the late Paleozoic.

       

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