Tethyan evolution from early Paleozoic to early Mesozoic in southwest Yunnan

The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain. The abundant, well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto- and Paleo-Tethys. In this paper, we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic, based on stratigraphic, sedimentologic, and magmatic evidences. The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys. The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian (about 505 Ma). From the late Late Ordovician to the ealiest Silurian (about 450-442 Ma), the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean. The main collision stage occurred in the early Silurian (about 442-430 Ma) and the post-collision stage lasted from the mid-Silurian to the early Carboniferous (430-355 Ma). The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian, and the ocean was then subducted in an eastward direction in the middle Late Carboniferous (about 310 Ma). The initial collision stage in the Paleo-Tethys took place at the end of the Permian (about 253 Ma), and the main stage of the collision persisted into the early Ladinian (about 253-238 Ma). This was followed by post-collision extension from the late Ladinian to the early Jurassic (ca. 238-196 Ma). We suggest that the opening of Paleo- Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys. Additionally, the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean.