Geochemistry, fluid inclusions and sulfur isotopes of the Govin epithermal Cu-Au mineralization, Kerman province, SE Iran

Abstract

Govin area is located southeast of the Urmieh-Dokhtar volcano- plutonic arc, which formed as the result of subduction of the Neo-tethyan oceanic crust beneath the central Iran continent. The arc hosts world-class Sar-Cheshmeh Cu porphyry deposit and many other Cu, Cu-Mo, Cu-Au porphyry, and Cu-Zn-Pb-Ag-Au skarn and epithermal deposits. The rock units in the Govin area include Eocene volcaniclastic rocks that intruded by post-Miocene hypabyssal quartz-monzonite, grano-diorite, diorite and quartz-diorite stocks. The stream sediment geochemical surveys display Cu, Au, Mo, Bi, Sb, Pb and As anomalies. The lithogeochemical prospecting in anomaly checking stage identified quartz veins with considerable abundances of Cu (2.98%) and Au (2.41 ppm). The ore-bearing quartz veins classify into quartz + iron oxides ± gold and quartz + sulfide ± gold. The dominant structural trend of vein systems is 60°–70° (NE-SW), with dips from 75° NW to vertical that cut altered andesite, porphyritic andesite, basaltic andesite and tuff. Mineral associations are quartz, adularia, chalcopyrite, pyrite, bornite, galena, sphalerite, as well as chalcocite, covellite, malachite, iron oxides and hydroxides in oxidized zones. Hydrothermal alteration is generally well-developed surrounding the ore-bearing systems. The main types of alterations in the area include propylitization, phyllic, and argillic associated with silicification. Fluid inclusions studies on quartz grains separated from mineralized veins exhibits the melting temperature of ice (Tm ice) values range from −12 to −1 °C corresponding to salinities of 2.5 to 37.04 wt% NaCl equiv. The superfluity LV fluid inclusions have salinity of 2.47 to 15.96 wt% NaCl equiv. The homogenization temperature of LV, VL and LVS fluid inclusions range from 146 to 366 °C, 405 to 425 °C and 236 to 270 °C, respectively. The fluid inclusions observations reveal that both dilution and boiling of fluids were important in the deposition of metals in the Govin. The δ34SCDT of pyrite and chalcopyrite grains associated with mineralized quartz veins range from −2.13‰ to −8.54‰ that indicate sulfur originated from host volcanic-sedimentary series in the area. The Cu-Au bearing quartz veins in the Govin area are classified as low-sulfidation epithermal system, located in closed association with the Sar-Cheshmeh and Darreh-Zar porphyry copper deposits.