Geological characteristics and metallogenic model of phosphate deposit of Kunyang type in Sichuan Province

The phosphate deposit of Kunyang type in Sichuan Province is located in Emeishan fault arch and Liang-shan depression fold bundle of upper Yangtze platform depression, belonging to the northern part of the Early Cambrian. The occurrence of phosphate deposit is in the middle and lower part of Mediping Formation of Lower Cambrian and it extends in layers, similar with the phosphorus bearing layer. The phosphate deposit has characters of stable sequence, wide distribution and large reserves, with great prospecting potential. The authors in this paper summarized the geological characteristics of the deposit and the distribution regularity of the deposit to analyze the metallogenic geological conditions and metallogenic elements such as metallogenic paleostructure and palaeogeographic environment, and establish the regional metallogenic model, on the basis of collecting and sorting out previous research data and achievements of exploration projects. It is considered that the mineralization of phosphate deposit of Kunyang type is mainly biochemical sedimentation, which belongs to a marine phosphate rock deposit formed by ionic combined precipitation and debris accumulation in a basin. The formation and distribution of the deposit are controlled by paleogeography and paleostructure, and the phosphorus deposits are mainly concentrated in the secondary sagbasin of the faulted basin formed along the South north oriented paleofault. The bay environment has hydrodynamic conditions from low energy to high energy, and several sub primary small basins formed by the geomorphic differentiation inside the bay, which make the bay a good place for phosphorus formation and accumulation. The results show the favorable conditions for the formation of phosphorus rich deposit are the abundant phosphorus source, the mechanical effects of crushing, scouring, winnowing and transportation in the medium high energy environment, and the suitable sedimentary environment in the small depression basin. The metallogenic model is biochemical deposition, crushing, scouring, winnowing, transportation and accumulation diagenesis and mineralization. The establishment of the metallogenic model provides a theoretical basis for scientific prospecting in the area and a direction for further prospecting.