冈底斯中段厅宫地区比马组碎屑锆石U-Pb年龄

桑日群广泛分布于冈底斯火山岩浆弧的中东段，是新特提斯洋俯冲作用的代表性记录。本文对冈底斯中段厅宫地区桑日群比马组开展了碎屑锆石U-Pb同位素测年和地球化学特征研究，结果表明：比马组所含的碎屑锆石具有85.7~143.5Ma、160.2~191.2Ma、334.4~364.1Ma和904Ma四个年龄段，其中最年轻的碎屑锆石年龄为85.7±1.9Ma，结合古生物资料，认为比马组形成于早—晚白垩世，其物源主要来自于拉萨地块，尤其是冈底斯岩基剥蚀源区；岩石地球化学特征显示，比马组沉积主要来源于长英质岩石，是上地壳源区物质经风化剥蚀后搬运沉积形成。

U-Pb dating for detrital zircons from the Bima Formation, Tinggong, Tibet

The Sangri Group is widely distributed in the middle-east section of the Gangdise volcanic-magmatic arc, which is a representative record of the subduction of the New Tethys Ocean. The U-Pb dating for the detrital zircons from the Bima Formation of the Sangri Group in Tinggong area shows four ages, which are 85.7-143.5Ma,160.2-191.2Ma,334.4-364.1Ma and 904Ma respectively. Combining the youngest age (85.7±1.9Ma) with fossils obtained from the Bima Formation, the authors believe that the Bima Formation was formed between the early Cretaceous and the late Cretaceous, and its sedimentary materials were from the eroded volcanic-magmatic areas of the Lhasa block.