Geochemical zonality coefficients in the primary halo of Tavreh mercury prospect, northwestern Iran: implications for exploration of listwaenitic type mercury deposits

Abstract

The Tavreh mercury prospect is located in the NW of Iran. This prospect is a listwaenite alteration and mineralization system which is controlled by structural agents and is restricted to shear zones. In this study, the primary geochemical halo was investigated to estimate the level of erosion of mineralization based on the lithogeochemical data. These data were obtained by ICP-MS analysis following an aqua regia decomposition of 64 samples along 13 profiles and 30 samples collected from trenches. The prediction of the erosion level of a geochemical anomaly is usually accomplished by comparing the values of the vertical geochemical patterns with values of the same parameters that are known around similar mineralization. The (As.Sb.Ag/Cu.Co.Ni) (Vz 1 index) and (Sb.As/Pb.Zn) (Vz 2 index) zonation indices were used as geochemical indicators to detect the present level of geochemical anomalies in the Tavareh region. The average value of the Vz 1 index was 1.98 × 10 −4 , which is higher than the middle part of the recognized listwaenite-type mercury deposits and is lower than the upper part of the supra-ore halo. The average value of the Vz 2 index is 3.76, which also indicates a supra-ore geochemical halo. Values of Vz 1 and Vz 2 indices imply the presence of sub-cropping of the main part of the ore body in the Tavreh area. It is expected that values of Vz 1 and Vz 2 decrease with increasing depth.