新疆西准噶尔早石炭世沉积地层的物源及构造环境

沉积物的地球化学和碎屑锆石特征在沉积岩物源分析及构造背景的研究中具有较为重要的作用.对克拉玛依后山地区早石炭世包古图组和太勒古拉组碎屑岩样品(共42个)进行了岩石学和地球化学研究，结果显示，这套碎屑岩的主量元素SiO₂含量为54.64%~73.14%，Al₂O₃含量相对较高(11.89%~19.36%)，(TFe₂O₃+MgO)含量比较高(3.97%~9.99%)，反映岩石化学成熟度偏低.岩石稀土元素含量变化较大，在83×10-6~252×10-6之间变化，无Ce异常，Eu呈微弱负异常，具有低的∑REE等特征，与大洋岛弧型砂岩相似.采自这2个组的碎屑锆石U-Pb定年结果表明，包古图组有340 Ma和440 Ma两个主峰值，主要来源于石炭纪、志留纪的源岩；太勒古拉组碎屑锆石主峰值为325 Ma，其年龄与地层年龄很接近，推测其主要来源于同沉积石炭纪岩石.根据主、微量及稀土元素等多个构造环境判别图解的综合分析，结果表明早石炭世包古图组和太勒古拉组沉积物的物源特征及沉积构造背景较为相似，主要为大洋岛弧-大陆岛弧环境下的中酸性火山岩，夹有少量基性火山岩. 

Provenance and Tectonic Settings of Early Carboniferous Sedimentary Strata in Western Junggar,Xinjiang

The geochemistry and detrital zircon characteristics of the sediments play an important role in the study of sedimentary provenance and their tectonic settings. This paper presents petrography and geochemical study of the Early Carboniferous Baogutu Group and Tailegula Group clastic rocks in Karamay area, western Junggar, NW Xinjiang. Geochemical data show that the sedimentary rocks have SiO₂ contents (54.64%-73.14%), relatively high Al₂O₃ contents (11.89%-19.36%) and high (TFe₂O₃+MgO) contents (3.97%-9.99%), indicating low chemical maturity. Their total rare earth element contents vary between 83×10-6 and 252×10-6, characterized by no Ce anomaly and slightly negative Eu anomalies, which is similar to those of sandstones formed at oceanic island arc setting. U-Pb dating results of detrital zircons show that Baogutu Group has 340 and 440 Ma two peak values. Detrital zircons of Tailegula Group show only one peak (325 Ma) and suggests that they were sourced from the Early Carboniferous rocks. Discrimination diagrams of the major and trace elements show that the provenance and tectonic settings of Early Carboniferous Baogutu and Tailegula groups sedimentary rocks were formed from the oceanic island arc and continental island arc acidic volcanic rocks, with minor mafic volcanic rocks.