青藏高原羌塘南部埃迪卡拉纪地层研究

The Qiangtang terrane is situated in the hinterland of the Tibet Plateau along the northern margin of Gondwana. Because of its particular tectonic location, an understanding of the origin and tectonic evolution of the Qiangtang terrane is important when examining the formation and evolution of the Tibet Plateau, the breakup of the Gondwana supercontinent, and the evolution of the Tethys Ocean. However, the origin and the early evolution of the Qiangtang terrane remain enigmatic. Recently, some preliminary studies suggest that the newly found clastic rocks in the Dabure area (herein referred to as the Dabure clastic rocks) represent the late Ediacaran (~550 Ma) sedimentary record of the Qiangtang terrane. Of course, in the course of the study there are many issues have not been resolved, to be further in-depth inquiry. This project focuses on the forming environment, provenance, formation age and tectonic significance of the Dabure clastic rocks in the southern Qiangtang. In order to solve these problems, we analysis the chronology, petrostratigraphy, geochemistry and isotopic geochronology features of the Dabure clastic rocks.This program is of not only important theoretical significance for revealing the evolutionary history of the Qiangtang terrane in late Neoproterozoic, but also provide new clues for tectonic evolution of the northeastern margin of Gondwana.

羌塘位于青藏高原北部，其早期演化历史一直备受学术界的关注，因其起源及早期演化历史与青藏高原的早期形成与演化密切相关。然而，由于地质资料的缺失，羌塘古生代以前的研究几近空白。申请者及团队人员在羌塘南部地区识别出一套碎屑岩夹玄武岩的岩石组合，初步研究结果表明其形成时代为新元古代晚期的埃迪卡拉纪，是目前羌塘地区首次发现的新元古代地层。目前对于该套地层尚有很多问题有待深入的研究工作。本次拟在详细的野外地质调查基础上，综合利用岩石学、岩石地层学、同位素年代学、地球化学等手段，查明达布热碎屑岩的形成时间，沉积环境以及物源，构造背景等，揭示羌塘新元古代晚期的构造演化历史。该项研究对于探讨羌塘乃至青藏高原的早期演化历史以及冈瓦大陆早期形成演化等地质问题具有重要的意义。

青藏高原由松潘甘孜、羌塘、拉萨以及喜马拉雅等地体组成，羌塘地处青藏高原中部，构造上处于冈瓦纳超大陆北缘。其早期演化历史一直备受学术界的关注，因其起源及早期演化历史与青藏高原的早期形成与演化密切相关。近期，申请者及团队人员在羌塘南部地区识别出一套碎屑岩夹玄武岩的岩石组合，研究结果表明其形成时代为新元古代晚期的埃迪卡拉纪，是目前羌塘地区首次发现的新元古代地层。本次工作在详细的野外地质调查基础上，综合利用岩石学、岩石地层学、同位素年代学、地球化学等手段，查明了达布热碎屑岩的形成时间，确定其具有浊流沉积的属性，形成于半深海到深海环境。根据碎屑锆石定年结果，该套地层中碎屑锆石的最年轻年龄为~550 Ma。此外，该套地层中玄武岩夹层的测年结果表明该套地层形成于埃迪卡拉纪(~550 Ma)。结合地层剖面以及区域地层对比，我们建立了埃迪卡拉纪达布热组。达布热组是羌塘地区首次发现的埃迪卡拉地层，该组地层的建立为探讨冈瓦纳大陆北缘构造演化提供了重要线索。