Primary Research On Geochemistry And Geochronology Of The Laojunshan Metamorphic Core Complex, Southeastern Yunnan

According to the systematic researches on the geology, geochemistry and thermochronology of the Laojunshan metamorphic core complex, these preliminary conclusions had been drawn as follows.Firstly, in the Laojunshan area, it was indicated that there should exist the Paleoproterozoic basements rocks and Mesoproterozoic and Neoproterozoic magmatism, which related to the Neoproterozoic super mantle plume beneath South China Block and the breakup of the Rodinia Super-continent.Secondly, the Nanlao Gneiss and the Nanwenhe Granites were productions of same Caledonian magmatism related to collision between Yangtze and Cathaysia blocks, and both were S-type granites derived from partial-melting of the metamorphosed muldstone, sandstone and moderate-basic rock.Thirdly, the Laojunshan metamorphic core complex formed at ca. 250Ma to ca. 160Ma, followed by posterior brittle upheaving, and finally exhumated at the end of Tertiary.Forthly, two large scale mineralization events had been identified along the ductile-brittle and the ductile detachment systems, separately. The first one happened at ca. 220 Ma to ca. 200Ma and formed the Xinzhai and Nanyangtian tin-tungsten deposits, and the second took place at ca. 80 Ma and formed the Dulong tin-zinc deposit.Fifthly, North Vietnam Oldland was a part of the Cathaysia block before the collage between the Cathaysia and the Yangtze blocks. The terrane between Song Ma shear zone and Day Nui Con Voi shear zone was sheared about 600km along the left-lateral Ailaoshan-Red River Shear system, and was also a part of the South China Plate rather than a part of the Indochina Block.Sixthly, based on the geology, geochemistry and thermogeochronolgy, the tectonic implications of the Laojunshan metamorphic core complex had been discussed. The Song Ma Suture should present the collision between the Indochina...