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<p>The Central Yunnan Basin (CYB) that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain, is a typical ‘red bed’ sedimentary basin formed since Late Triassic. The CYB is composed of mega-thick fluvial and lacustrine facies successions. However, the tectonic evolution and sedimentary provenance studies on this basin are scarce. In this study, we report new detrital zircon ages of four sandstones from the Lower Jurassic Fengjiahe Formation (FJF), including four major clusters of 2 060−1 810, 870−760, 485−430, and 280−254 Ma, with sporadic Archean, Cambrian, and Triassic ages. We interpret that the Archaean and Proterozoic zircons were mainly derived from the western Yangtze Block, which may recycle from the Jiangnan Orogen, the Cathaysia Block and the Proterozoic igneous rocks. Ordovician and Silurian zircons were probably from the Ailaoshan orogenic belt, and the Lancang Group in western Yunnan, as well as the Yangtze, Cathaysia and Indosinian blocks. Permian zircons probably came from the Ailaoshan orogenic belt and the Emeishan basalt. The youngest zircon age of ∼212.9 Ma indicates that the depositional age of the FJF is younger than the Norian stage. We also proposed a geodynamic model of the CYB and the Ailaoshan orogenic belt during the Mesozoic. The Simao Block to the west of the CYB constituted the Ailaoshan orogenic belt and collaged with the Yangtze Block during the Early Triassic, provided sedimentary provenance to the CYB. The Changning-Menglian zone that composed of the Baoshan and the Simao Blocks, uplifted in the Late Triassic and provided provenance to the CYB. Collapse of the Ailaoshan orogenic belt in Late Triassic probably provided channel for source materials that transported from the Lincang granites to the CYB. We propose a transtensional tectonic setting of the central Yunnan during the Early Jurassic, after a short collision during the Indosinian Movement in the Late Triassic.</p>

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Detrital Zircon Geochronology of Early Jurassic Successions in the Central Yunnan Basin, Southwest China: Implications of Sedimentary Provenance and Tectonic Evolution

  • 期刊论文

  • 发表日期：

    2025年8月13日

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  • Liangdong Luo,
  • Jun Wang,
  • Yujie Yuan,
  • Zerui Liu,
  • Mengyan Jiao,
  • Yingao Zhang,
  • Saike Zhang

摘要

The Central Yunnan Basin (CYB) that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain, is a typical ‘red bed’ sedimentary basin formed since Late Triassic. The CYB is composed of mega-thick fluvial and lacustrine facies successions. However, the tectonic evolution and sedimentary provenance studies on this basin are scarce. In this study, we report new detrital zircon ages of four sandstones from the Lower Jurassic Fengjiahe Formation (FJF), including four major clusters of 2 060−1 810, 870−760, 485−430, and 280−254 Ma, with sporadic Archean, Cambrian, and Triassic ages. We interpret that the Archaean and Proterozoic zircons were mainly derived from the western Yangtze Block, which may recycle from the Jiangnan Orogen, the Cathaysia Block and the Proterozoic igneous rocks. Ordovician and Silurian zircons were probably from the Ailaoshan orogenic belt, and the Lancang Group in western Yunnan, as well as the Yangtze, Cathaysia and Indosinian blocks. Permian zircons probably came from the Ailaoshan orogenic belt and the Emeishan basalt. The youngest zircon age of ∼212.9 Ma indicates that the depositional age of the FJF is younger than the Norian stage. We also proposed a geodynamic model of the CYB and the Ailaoshan orogenic belt during the Mesozoic. The Simao Block to the west of the CYB constituted the Ailaoshan orogenic belt and collaged with the Yangtze Block during the Early Triassic, provided sedimentary provenance to the CYB. The Changning-Menglian zone that composed of the Baoshan and the Simao Blocks, uplifted in the Late Triassic and provided provenance to the CYB. Collapse of the Ailaoshan orogenic belt in Late Triassic probably provided channel for source materials that transported from the Lincang granites to the CYB. We propose a transtensional tectonic setting of the central Yunnan during the Early Jurassic, after a short collision during the Indosinian Movement in the Late Triassic.