藏北那曲盆地中—上侏罗统拉贡塘组浊流沉积特征及微量元素地球化学

藏北那曲地区中上侏罗统拉贡塘组发育典型的深水浊流沉积，根据浊积岩鲍马序列和粒度特征，可以进一步将其区分为近源砂质浊积岩和远源细屑浊积岩。微量及稀土元素地球化学研究表明，拉贡塘组浊积岩富集Cr、Co、Sc、Th等元素，无Ce负异常或负异常不明显，沉积物物源主要来自于变质岩区或再循环的沉积岩分布区。那曲盆地是冈底斯中生代多岛弧盆系统的组成部分之一，中上侏罗世深水浊流沉积形成于活动大陆边缘中的弧后盆地环境，该弧后盆地的形成与班公湖怒江中特提斯洋盆的洋壳向南的俯冲作用有关。

Sedimentary Characteristics and Trace Elements Geochemistry of Middle-Upper Jurassic Turbidite in Nagqu Basin, Tibet

The authors have identified deep water turbidite sediments in Middle Upper Jurassic strata of Nagqu basin,northern Gandise, Tibet. The turbidite sediments are characterized by typeical Buma sequence. According to grain sizes of sediments and sedimentary structures, turbidites can be classified into two sedimentary types, namely proximal sandy turbidite and distal muddy turbidite. Geochemical studies of rocks indicate that the sedimentary source rock of the turbidites was derived from southern old arc island chain. The apparent enrichment of trace elements Cr, Co, Sc and Th and the negative Eu anomaly of turbidites suggest that the turbidite was formed in the back arc basin environment of active continental margin, and the formation of Nagqu back arc basin was related to southward subduction of Bangong Lake Nujiang River ocean crust.