The establishment of Ediacaran Dabure Formation in southern Qiangtang of northern Tibet and its significance
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摘要:
羌塘位于青藏高原腹地，构造上处于冈瓦纳大陆北缘。因其特殊的构造位置，羌塘地体的起源及构造演化对于探讨青藏高原的早期形成演化、冈瓦纳大陆裂解，以及特提斯洋演化等关键科学问题至关重要。最近，在羌塘南部达布热地区发现一套碎屑岩夹玄武岩的岩石组合，碎屑岩具有低成分成熟度的特点，虽然岩石发生了低绿片岩相变质，但仍然保留了原岩类复理石沉积的特点。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550Ma左右。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（约550Ma）。结合地层剖面及区域地层对比，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纪地层，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。
Abstract:The Qiangtang terrane is situated in the hinterland of the Tibetan Plateau on the northern margin of Gondwana. Because of its particular tectonic location, the understanding of the origin and tectonic evolution of the Qiangtang terrane is important in examining the formation and evolution of the Tibetan Plateau, the breakup of the Gondwana supercontinent, and the evolution of the Tethys Ocean. The Dabure clastic rocks discovered recently are characterized by low compositional and textural maturity, and have been affected by lower greenschist facies metamorphism. The deposits exhibit the typical features of turbidites. Based on detrital zircons U-Pb dating, the authors obtained the most reliable youngest age of detrital zircons from the Dabure clastic rocks, which is ca. 550Ma. Combining the data obtained by the authors with previous work on the basalts in the Dabure area (the Dabure basalts), the authors tentatively suggest that the Dabure clastic rocks represent the late Ediacaran (ca. 550Ma) sedimentary record of the Qiangtang terrane. On the basis of section measurement and regional correlation, the Ediacaran Dabure Formation was established. The establishment of the Dabure Formation not only has important theoretical significance for revealing the evolutionary history of the Qiangtang terrane in late Neoproterozoic but also provides new clues for tectonic evolution of the northeastern margin of Gondwana.
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Keywords:
- Tibetan Plateau /
- southern Qiangtang /
- clastic rocks /
- basalt /
- Ediacaran
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致谢: 样品的测试工作得到中国地质大学（北京）地学实验中心老师和同学的大力支持，参加野外工作的还有吉林大学地球科学学院杨德明老师、广州地球化学研究所张修政博士、中国地质科学研究院胡培远博士、河海大学吴浩博士及吉林大学西藏科研队伍的同学们，在此一并致以诚挚的谢意。
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图版Ⅰ
a.千枚岩野外照片；b.千枚岩显微照片；c.板岩野外照片；d.板岩显微照片；e.变质石英砂岩野外照片；f.变质石英砂岩显微照片；g.达布热玄武岩野外照片；h.达布热玄武岩显微照片
图版Ⅰ.
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