The Lancang metamorphic complex is a key component of the Three River Tethys Orogen in the SE Tibetan Plateau, with typical rock assemblages and deformation fabrics recording the subduction of the Paleo-Tethys Ocean and subsequent continental collision. In this study, we present new petrographic and structural observations, together with zircon U-Pb and mica 40Ar/39Ar geochronologic data, to reveal the deformation and kinematics of the Lancang metamorphic complex, thus providing insights into the Permian–Triassic evolution of the eastern Paleo-Tethys domain. The subduction of the Paleo-Tethys Ocean and subsequent collision resulted in a range of structural features, including penetrative regional foliations, thrusts, asymmetric folds at various scales, and ductile deformation fabrics such as asymmetric boudins and porphyroclasts. Zircon U-Pb dating of foliated gabbro and 40Ar/39Ar dating of mica schist and mylonite, which preserve shortening fabrics, suggest that the Paleo-Tethys Ocean was subducted during the Late Carboniferous to Permian–Early Triassic, and the collision of the Baoshan and Simao blocks mainly occurred during ca. 237–230 Ma in the SE Tibetan Plateau. Regional deformation likely shifted from shortening to extension ca. 230 Ma, as reflected by post-collision high-K calc-alkaline magmatism. Our results document regional structural patterns and place timing constraints on the evolution of the Paleo-Tethys Ocean.

中文翻译：

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澜沧变质杂岩的运动学和年代学：对古特提斯地区演化的启示

澜沧变质杂岩是青藏高原东南部三河特提斯造山带的重要组成部分，其典型的岩石组合和变形组构记录了古特提斯洋俯冲和随后的大陆碰撞。在这项研究中，我们提出了新的岩相和结构观测结果，以及锆石U-Pb和云母40Ar/39Ar年代学数据，揭示了澜沧变质杂岩的变形和运动学，从而为东部地区二叠纪-三叠纪演化提供了见解。古特提斯域。古特提斯洋的俯冲和随后的碰撞导致了一系列结构特征，包括穿透性区域叶理、逆冲断层、不同尺度的不对称褶皱以及延性变形结构，例如不对称布丁和碎斑岩。叶状辉长岩的锆石 U-Pb 定年和云母片岩和糜棱岩的 40Ar/39Ar 定年（保留了缩短组构）表明，古特提斯洋在晚石炭世至二叠纪 - 早三叠世期间俯冲，以及宝山和早三叠世的碰撞。思茅区块主要发生在大约 237–230 Ma，青藏高原东南部。区域变形可能从缩短转变为延伸。230 Ma，反映为碰撞后高钾钙碱性岩浆作用。我们的结果记录了区域结构模式，并对古特提斯海洋的演化施加了时间限制。