西藏拉萨-日多中生代沉积盆地的性质及其形成演化

拉萨-日多中生代沉积盆地是随着南冈底斯叶巴陆缘火山弧的形成而发育起来的,研究该沉积盆地的性质及其形成演化对青藏高原大陆动力学研究具有特殊意义。文章对该沉积盆地的区域地质背景、充填特征、岩相古地理、物源特征及盆地伸展构造进行综合研究,通过在研究区新发现的中生代地层多底沟组—塔克那组中以顺层韧性剪切带、顺层掩卧褶皱等为主要构造样式的顺层剪切构造,提出了晚侏罗-早白垩世盆地性质为伸展型盆地;设兴组的充填和岩相古地理特征表明晚白垩世-早古新世时期盆地性质转变为收缩型盆地。通过综合研究分析,认为拉萨-日多中生代沉积盆地并非是弧后盆地,而是在叶巴火山弧台地上形成的以火山为边界的弧内盆地,并进一步将早中侏罗世—晚白垩世盆地的形成演化分为早期盆地形成阶段、中期盆地伸展阶段和晚期盆地挤压消亡阶段。

The nature and formation and evolution of Mesozoic sedimentary basins in Lhasa-Riduo

The Lhasa-Riduo-Mesozoic sedimentary basin developed along with the formation of volcanic arcs on the margin of the Yeba Earthy in the southern Gangdese. The study of the nature and evolution of the sedimentary basin is of special significance to the study of the continental dynamics of the Qinghai-Tibet Plateau. In this paper, a comprehensive study of the geological background, filling characteristics, lithofacies paleogeography, provenance characteristics, and basin extension structure of the sedimentary basin were carried out, in the newly discovered Mesozoic strata of the Duodigou Formation-Takena Formation, The ductile shear zone, bedding sheltered folds etc. are the main structural patterns of the bedding shear structure. The characteristics of Late Jurassic-Early Cretaceous basins are extensional basins; the filling and lithofacies palaeogeography of the Shexing Formation are suggested. During the Late Cretaceous-Early Paleocene, the nature of the basin turned into an extrusion. Through comprehensive research and analysis, it is believed that the Lhasa-Riduo Mesozoic sedimentary basin is not a back-arc basin, but an arc-inline basin bordered by volcanoes formed on the Yeba volcanic arc plateau, and further the early-middle Jurassic-late. The formation and evolution of the Cretaceous basin consisted of the formation stage of the early basin, the extension stage of the intermediate basin,and the extinction stage of the late basin.