青海格尔木市黑海地区三叠系巴颜喀拉山群变质碎屑岩地球化学特征及物源分析

Geochemical characteristics and provenance analysis of the Triassic metasedimentary rocks of Bayan Har Group in Heihai area,Golmud City,Qinghai Province

巴颜喀拉地块位于青藏高原东北部,是古特提斯的主体,对其进行深入的研究不仅对确定古特提斯的演化过程与方式具有重要意义,而且对探讨该地区与古板块演化有关的成矿地质作用和矿产分布规律具有重要的现实意义。巴颜喀拉山群位于巴颜喀拉地块,对其物源研究较为薄弱。碎屑岩中的碎屑组分特征和地球化学特征可以反映物源区和沉积盆地的构造环境。本文通过对三叠系巴颜喀拉山群变碎屑岩岩相学特征、沉积结构特征、地球化学判别参数以及地球化学判别图解的研究,结合前人在这一地区所做的如古水流等相关工作,认为巴颜喀拉沉积盆地是在古老基底裂解的基础上形成的,存在裂陷扩张、海水加深的过程,具有大陆岛弧和活动大陆边缘型物源的特征,接受其北部东昆仑造山带碎屑的沉积,沉积物来自亲上地壳长英质源区。

The Bayan Har block, as the main body of Tethys, is located in the northeast of the Tibetan Plateau. Indepth study in this area is not only of great importance for determining the evolution of Tethys but also of important practical significance for the research on metallogenesis related to tectonic evolution and minerals distribution in this area. The Bayan Har Group is located in the Bayan Har block, where the research on its provenance is insufficient. Its detrital and chemical components can reflect the features of the provenance and tectonic setting. The authors＇ researches on petrological characteristics, depositional setting, geochemical indices and geochemical discrimination diagrams of clastic rocks of the Bayan Har Group, together with previous researches on paleocurrent of Bayan Hat Group clastic rocks, suggest that the Bayan Hat Triassic sedimentary basin was based on the splitting of the old basement, the process of ritt expansion did exist, the depth of water was increased,the tectonic setting was mainly characterized by the continental island arc and active continental margin, and the deposited sediments was derived from felsic rocks of upper continental crust of East Kunlun orogenic belt in the north.