The Tectonic Setting And Lithofacies Paleogeography Of Early Stage Of Late Permian Wuchiapingian In Southeastern Yunnan

This paper focuses on the geological setting and palaeogeography of the main metallogenic epochs of southeastern Yunnan. On the basis of the summary of previous research and related research achievements, this paper regards lots of outcrop section, drill holes and renches as the main basis, based on the theory of sedimentology, palaeontology, palaeogeography and sequence stratigraphy tectonics, by using of geochemistry, the tectonic setting of the studied area was studied systematically. On this basis, build up sedimentary facies model of the Late Permian of Early Wuchiapingian in this district, and then We systematic study the palaeography of Early Wuchiapingian.The main results as follows:1. Based on geochemical characteristics of volcanic rocks from studied area and its neighboring areas, i.e. Jianshui of southeastern Yunnan and Western Guangxi Province, the author draw a conclusion that the tectonic setting was influenced by both Emeishan mantle Plume and the subduction of oceanic crust, resulting its tectonic setting of back-arc; the geochemical characteristics of sedimentary rocks and bauxites results suggest that the Emeishan basalts, granites are the main source of material for the bauxite ores and siltstone, sandstones, respectively. The precursor rocks for silty mudstone are basalts and granites; the geochemical characteristics of cherts implies the dual effects of both Emeishan mantle Plume and rupture.2. On the basis of predecessors study, combining with the rock styles and their combinatorial feature, depositional features, facies types, the paper puts forward a sedimentary facies model of offshore-epicontinental sea of the Late Permian of Early Wuchiapingian in this district.The types of subfacies and micro-facies of each sedimentation have been distinguished further, including swamp, supratidal, intertidal, subtidal and restricted shallow sea subfacies and micro-facies.3. On the basis of the quantitative and qualitative data of outcrops and well sections, according to the single factor analysis and multifactor comprehensive mapping method, the lithofacies palaeogeography of Wujiaping Early Stage of Late Permian in Wenshan, Southeast Yunnan, was studied and mapped, the research results as following:Kangdian old land and North Vietnam old land located to the west and Southeast of Wenshan during Late Permian Wuchiaping age; Kangdian old land and North Vietnam old land were the common material sources provider; the sediments of Tianshengqiao deposited in low-lying peat, which constituted the depocenter.