南祁连盆地上三叠统阿塔寺组碎屑岩地球化学特征及其源岩

Geochemistry Characteristics and Provenance Rock of the Upper Triassic Atasi Formation Detrital Rocks in the Southern Qilian Basin

南祁连盆地在晚三叠世时期处于陆相沉积,上三叠统阿塔寺组碎屑岩十分发育。盆地三叠系砂岩的岩性及岩相特征与二叠系非常相似,但是源岩构造背景、物质组成及物质来源与二叠系有所差异。根据地球化学主量元素、微量元素分析结果,上三叠统阿塔寺组源岩构造背景活动性较强,以活动性较强的大陆岛弧及活动大陆边缘为主,源岩物质组成以长英质火成岩为主。结合区域地质构造背景判断,南祁连盆地上三叠统阿塔寺组沉积物源区以北物源为主,以南物源为辅,中祁连的前震旦系及下古生界变质结晶岩系及花岗岩为其主要物源。

The Southern Qilian Basin deposits of the continental facies with the development of the detrital rocks in the Upper Triassic Atasi Formation. The lithology and lithofacies characteristics of Triassic sandstone is very similar to Permian sandstone,but the tectonic setting,material composition and the source area of Triassic source rock is different from Permian source rock in Southern Qilian Basin. According to the analysis results of major elements and trace elements of the sandstones,the source rocks of Upper Triassic Atasi Formation belong to an active tectonic setting,mostly like the continental island arc and active continental margin. The material composition of the source rock is mainly the felsic volcanic rock. The source area of the deposition of the Upper Triassic Period in Southern Qilian Basin is most possibly the metamorphic crystalline rock series and granite of the Presinian System and Lower Paleozoic from Middle Qilian integrated with the regional tectonic setting.