Geological, geophysical and geochemical characteristics and comprehensive prospecting model of the Xiasai Ag-Pb-Zn deposit in the Yindun Island Arc

Abstract: Located in central of the Yindun Island Arc, the Xiasai Ag-Pb-Zn deposit is a typical hydrothermal vein deposit associated with early Cretaceous A-type granite. Orebodies commonly occur as lodes, lenses and strings of beads controlled by the NNW-trending faults. They pinch northward and are characterized by pinch out-reproduction and branching-complexing. From south to north, metallogenic element zoning is in order of Sn-Cu→Cu-Zn→Ag-Pb, constituting a complete metallogenic element zoning and ore mineral zoning related to magmatism. Ore-related hydrothermal alteration is well developed and dominated by silicification, sericitization and chloritization with a banded alteration zonation. The ore-forming process can be divided into five stages, i.e., cassiterite stage, arsenopyrite stage, sphalerite-chalcopyrite stage, silver-rich mineral-galena stage and pyrite-carbonate stage. The ?T positive anomalies of high-precision magnetic survey with extension of 20 m can be used as a geophysical prospecting indicator because they can accurately identify mineralized veins or ore-bearing faults. In addition, anomalies of soil geochemical survey with extension of 20 m consist of Ag, Pb, Zn and Cu elements, and their variation trend can also accurately identify mineralized veins or ore-bearing faults. Combined with geological, high-precision magnetic and soil geochemical characteristics of the Xiasai Ag-Pb-Zn deposit, the authors propose a comprehensive prospecting model in the search for new orebodies. The subsequent geological verification shows a good prospecting effect. It is thus held that the comprehensive prospecting model has important reference significance for the prospecting work of the Xiasai Ag-Pb-Zn deposit and hydrothermal veined Ag polymetallic deposits in the Xiasai-Lianlong Ag-Sn ore district within the central Yidun Island Arc of Southwest China.