东特提斯喜马拉雅下白垩统碎屑锆石U-Pb年代学及其古地理

U-Pb Age of Detrital Zircons from Lower Cretaceous in Eastern Tethyan Himalaya and Its Paleogeography

东特提斯喜马拉雅在中生代位于东冈瓦纳大陆的结合部位,其古地理对于了解东冈瓦纳大陆裂解至关重要.对东特提斯喜马拉雅塔嘎地区沉积地层进行了详细的碎屑锆石U-Pb年代学研究.结果表明,东特提斯喜马拉雅塔嘎地区采样剖面沉积下限为126.6±2.7 Ma.碎屑锆石年龄谱显示东特提斯喜马拉雅塔嘎地区采样地层主要包含~520 Ma、~890 Ma和~1 200 Ma的特征峰值年龄,对比结果表明东特提斯喜马拉雅塔嘎地区沉积地层碎屑锆石年龄谱与印度东部和澳大利亚西南部地层碎屑锆石年龄谱具有一定的相似性.结合东冈瓦纳岩浆活动记录以及该剖面下部玄武岩年龄,东特提斯喜马拉雅塔嘎地区地层沉积于东特提斯喜马拉雅从东冈瓦纳大陆分离时期,其物质来源可能为印度东部、澳大利亚西南部以及南极大陆.

The eastern Tethyan Himalaya is located at the combination area of eastern Gondwana during the Mesozoic, and its paleogeography plays a vital role in understanding the breakup of eastern Gondwana. A detailed chronological study of detrital zircons was carried out on the sedimentary strata in Taga area. The zircon U-Pb isotope results show that the youngest age is126.6±2.7 Ma, suggesting that the lower limit of sampling section was the Early Cretaceous. The U-Pb age spectra of detrital zircons reveal three major age peaks at ~520 Ma, ~890 Ma, and ~1 200 Ma, of which the comparison with those from adjacent areas indicates similar age populations with eastern India and southwestern Australia. New results, together with the surrounding magmatic activity and the age of basalts in the lower part of sampling section, support that the studied section should be developed during the separation of the eastern Tethyan Himalayan from eastern Gondwana, and the main provenance of the sampling section might be from eastern India, southwestern Australia, and Antarctic.