Geological and geochemical characteristics and genesis of the Poshan silver deposit, Henan Province

Abstract：The Poshan superlarge silver deposit is located in the western end of the Weishancheng Au-Ag-dominated poly-metallic ore belt in Tongbai Mountains. The orebodies hosted in the horizons of carbonaceous sericite schist of the upper part of Neoproterozoic Waitoushan Formation (Pt3w3). Strictly controlled by the hosting strata and the Heqianzhuang anticline, the occurrences of orebodies are mainly shaped as stratiform, lode or lens. The dominated ore-type is altered tectonite. The ore-fluid belongs to the mesothermal, low salinity, low density, CO-2rich and K+-SO2-4 type fluid system. The ore-forming fluids were metamorphic in origin and generally evolved into meteoric water-sourced fluid in late metallogenic stage. The ore-forming elements including S and Pb must be mainly sourced from the Waitoushan Formation. The K-Ar isotopic ages of hydrothermal sericite and minette dyke are 103.6 Ma and 134 Ma, respectively, indicating the metallogenesis of the Poshan silver deposit formed in Early Cretaceous, when a tectonic setting changed from collisional compression to extension in Qinling-Tongbai orogen belt.