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    新疆东部哈尔里克山南麓石炭纪砂岩碎屑锆石SHRIMP U-Pb定年及其地质意义

    Detrital zircon SHRIMP U-Pb dating of Carboniferous sandstone from the southern foot of the Harlik Mountains, eastern Xinjiang,and its geological implications

    • 摘要: 提要:碎屑锆石研究是探讨其碎屑物质来源、源区特征、沉积时代和形成环境的一种有效途径。笔者通过对新疆东部哈尔里克山南麓石炭纪砂岩的47粒碎屑锆石SHRIMP U-Pb定年研究,获得的年龄为388~949 Ma,其主体为418~482 Ma。结合锆石的矿物学特征、CL图像特点以及哈尔里克山区域地质资料,得出如下结论:(1)哈尔里克山南麓所研究的砂岩中最年轻的碎屑锆石年龄是(388±9)Ma,这意味着这套地层不老于中泥盆世,结合区域地质资料,笔者认为这套沉积岩应是在晚石炭世沉积的;(2)所研究的砂岩的碎屑物质主要来源于哈尔里克山早古生代与岛弧演化相关的岩浆岩;(3)哈尔里克山经历了中奥陶世—早志留世与康古尔塔格洋壳残片代表的洋岩石圈板块向北俯冲有关的岛弧、石炭纪弧后盆地和晚石炭世末期弧后隆起的构造演化历史;晚石炭世末期弧后隆起是导致哈尔里克山与博格达山现今地质差异的主要原因。

       

      Abstract: Abstract:Research into detrital zircons is an effective approach to the sources and provenance features of detrital materials and depositional ages and environment. The authors performed SHRIMP U-Pb dating of 47 detrital zircon grains from Carboniferous sandstone at the southern piedmont of the Harlik Mountains, eastern Xinjiang, and obtained ages of 388 to 949 Ma, clustering at 418 to 482 Ma. Based on these dating data, combined with the mineralogical characteristics and CL images of zircons as well as the regional geological data of the Harlik Mountains, we may draw the following conclusions: (1) the youngest detrital zircon age of the studied sandstone is 388±9 Ma, implying that this sequence of the strata is not older than Middle Devonian in age and possibly was deposited in the Late Carboniferous according to the regional geological correlation; (2) the detrital materials of the studied sandstone were mainly derived from magmatic rocks related to the Early Paleozoic arc of the Harlik Mountains; and (3)the tectonic evolution of the Harlik Mountains progressed through the Middle Ordovician to Early Silurian magmatic arc related to northward subduction of the oceanic lithospheric plate represented by the Kanggurtag oceanic crustal fragment, Carboniferous back-arc basin and terminal Late Carboniferous back-arc uplift. The last event was probably the main cause for the present difference in geological outcrops between the Harlik and Bogda mountains.

       

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