Sedimentary Sequence of the Lower Cambrian Qingxudong Formation in the Western Hunan and Eastern Guizhou Provinces and its Constrains on Lead-Zinc Mineralization

In the Western Hunan and Eastern Guizhou Provinces, the Lower Cambrian is well developed and marked by sedimentary succession from black shale to carbonate rocks. Vertically, the stratigraphic succession constitutes a second-order sequence that can be further subdivided into five third-order sequences, and that makes up of a larger scale upward-shoaling succession of sedimentary facies and demonstrates a growth process of the ramp carbonate platform. Horizontally, the principal lithofacies palaeogeographic units in the study area, i. e. carbonate tidal flat, subtidal facies of restricted platform and platform marginal bioherm (or bank) facies as well as basin facies from the northern to the southern have been described. All of them demonstrate a complicated palaeogeographic background. The stratabound lead-zinc deposits distributing between platform marginal facies and subtidal facies of restricted carbonate platform were dominated by the lithofacies palaeogeographic framework. The black shale of the Niutitang Formation is source bed for the lead-zinc mineralization and the Qingxudong Formation is the host rock (reservoir bed). The assemblage that made up of turbidite and algal bioherm (reef) and rudstone is a well developed succession for the lead-zinc deposits controlling.