新疆哈拉阿拉特山太勒古拉组黑色页岩构造背景及物源分析

    Tectonic setting and provenance analysis for Tailegula Formation black shales in Hala-alat Mountain of Xinjiang

    • 摘要: 新疆哈拉阿拉特山地区(简称哈山地区)在晚石炭世为沟弧盆体系下岛弧较发育的构造格局,上石炭统太勒古拉组黑色页岩被认为是岛弧作用相对减弱时期海沟和弧前盆地深水沉积的产物,但尚缺乏地球化学依据。对哈山地区太勒古拉组黑色页岩开展探槽施工并进行采样分析,结果表明: 黑色页岩具有富MgO和Na2O,贫TiO2、Al2O3、Fe2O3及CaO,SiO2含量适中,大离子亲石元素相对贫乏,轻稀土相对富集,重稀土相对亏损,负Eu异常的特征,与上地壳稀土元素配分模式相近; 哈山地区太勒古拉组黑色页岩的构造背景主要为大陆岛弧,母岩属于中酸性-长英质物源,主要来自上地壳,物源区可能为北部的塔尔巴哈台—纳尔曼得早古生代沟弧带和谢米斯台—东泉晚古生代岛弧带。研究可为哈山地区巨厚页岩的物质来源提供参考。

       

      Abstract: The tectonic framework in Hala-alate Mountain area of Xinjiang at the Late Carboniferous is island arc developed under trench-arc-basin system, and the Upper Carboniferous Tailegula Formation black shale is considered to be a product of deep-water deposition in the trench and forearc basin during the period of island arc effect being relatively weakened, but with a lack of geochemical evidence. Trench exploration and sampling analysis were conducted on the black shales of Tailegula Formation in the study area. The results show that the black shale of Tailegula Formation in the study area is rich in MgO and Na2O, poor in TiO2, Al2O3, Fe2O3 and CaO2, and moderate in SiO2. The large ion lithophile element is relatively poor, and light rare earth element is relatively rich. The heavy rare earth element is relatively loss, and the δEu has negative anomaly, indicating similar distribution pattern with rare earth element in the upper crust. The tectonic setting of Tailegula Formation black shale in Hala-alate Mountain is mainly the continental island arc. The source rock belongs to intermediate to acid and felsic provenance, and it mainly originates from upper continental crust. The source region is probably Early Paleozoic trench-arc of Tarbagatay-Narmande and Late Paleozoic island arc of Xiemisitai-Dongquan in the north. This study could provide some references for the provenance analysis of the giant thick shales in Hala-alate Mountain area.

       

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