藏北羌塘查郎拉地区中生代盆地沉积构造背景探讨

DISCUSSION ON THE SEDIMENTARY TECTONIC SETTING OF MESOZOIC BASIN IN CHALANGLA AREAS,QIANGTANG,NORTHERN TIBET

羌塘盆地查郎拉地区位于唐古拉山南坡 ,大地构造位置处在羌塘盆地羌南坳陷 ,出露地层为中生界及新生界 ,缺失古生界地层。为评价该区中、新生界含油气前景 ,应用沉积学和沉积地球化学方法 ,通过碎屑岩颗粒成分分析研究了该地区中生代的大地构造背景。首次提出该区中生代物源区应为碰撞造山带—前陆隆起区 ,具有增生基底特点 ;研究区所处的羌南坳陷总体为一拉张背景下的边缘前陆盆地 ,具有被动大陆边缘—活动大陆边缘过渡性质。

Chalangla area in Qiangtang basin in northern Tibet lies in the south slope of the Tanggula Mountains, and the southern depression of Qiangtang basin. Its exposure strata are Mesozoic and Cenozoic, in which there is no Palaeozoic. The author discusses the sedimentary tectonic setting of Mesozoic basin in Chalangla areas in Qiangtang Region in northern Tibet using sedimentology and sedimentary geochemical methods in order to evaluate prospect of oil gas for exploration in the area. From the analysis of grain compositions, chemical content and trace elements in sandstone the paper presents for the first time that the area from collision orogenic zone to forebulge was source area in Mesozoic, and the area is characterized by basement accretion. The Chalangla area in Qiangtang depression is a foreland basin, and it is of an interim between passive and active continental margins.