Devonian sedimenatry facies and palaeogeography and sequence stratigraphy of the Tuoding copper mining district, Yunnan

The Devonian strata in the Tuoding region, Yunnan are widespread as fault blocks along the Jinsha River, especially on the eastern bank of the river. These strata may be composed of the Lower Devonian clastic rocks, Middle Devonian carbonate rocks and Upper Devonian clastic-carbonate rocks, and fall, according to sedimentary structures and lithology, into six distinct sedimentary facies:littoral, shallow sea and shelf, restricted platform, lagoon, biohermal and tidal-flat facies. There are gradations of the sediment configuration in the study area from the clastic shelf in the early stage to the carbonate platform sediments in the middle and finally to the mixed clastic-carbonate shelf in the late stage, indicating that the carbonate platform in this area was developed on a early clastic ramp. Five sedimentary sequences have been distinguished for the Devonian strata in the study area. The results of research in this paper have revealed that the copper mineralization occur in the highstand systems tract including the platform-bank laminated dolostone, dolarenite, pelleted dolostone and oncolite-oolitic dolostone.