Depositional Features and Grain Size Characteristics of Sandstone-Type Ore of Jinding Pb-Zn Deposit in Lanping Basin

Jinding super-large Pb-Zn deposit is mainly composed of breccias-type and sandstone-type ore body, but the genesis and ownership of ore-hosted rocks are still unclear. The utilization of grainsize data to analyze the structure characteristics of the sediment grains can effectively determine the transport mode of sediments, judge the hydrodynamic conditions, distinguish the sedimentary environments, and analyze the genetic mechanism of sediments. Based on the probability cumulative grain-size curves and C - M graph, the authors studied in detail the grain-size characteristics of sandstone-type ore, and defined its sedimentary hydrodynamic type, then combined with the tectonic background of the sandstone-type ore body and ore microscopic structure characteristics, the genesis of sandstone-type ore was discussed. The result shows that the sandstone-type ore belongs to the fine sandstone-siltstone, the average particle size of 1.526Φ, positive skewness or very positive skewness, and material source for river sand. From Sahu environment discriminant and C - M graph, it can be seen that the sandstone in the study area is given priority to gravity flow deposits. The result shows that the sandstone is formed by fragmentary material handling in gravity flow and mixed with the bottom material, resuspension and sedimentary under the action of rapidly water.