Fluid evolution and ore genesis of the southern Chah-Palang W-(Cu–Au) deposit, SE Anarak, Iran

Mineralization of the southern Chah-Palang W (Cu–Au) deposit in the Yazd Block, central Iran are ore-bearing veins and veinlets commonly hosted by Jurassic sandstone and shale rocks of the Shemshak Formation that is intruded by younger dacitic domes. Tungsten and gold are temporally and spatially related to NW-trending, subvertical hydrothermal breccias veins with silicic–chloritic alterations. The deposit formed during granitic magmatism. Three stages of veins–veinlets are recognized: early-stage quartz 1, wolframite, scheelite 1, pyrite 1, chalcopyrite 1, and arsenopyrite1 vein–veinlets; intermediate stage: quartz 2, scheelite 2, gold, pyrite 2, chalcopyrite 2, arsenopyrite 2, pyrrhotite, bornite, native bismuth, niccolite, cobaltite, and sphalerite vein–veinlets; late-stage hematite: quartz and carbonate vein–veinlets. The first two stages are economic significance. The homogenization temperatures (Th) and salinities of fluid inclusion groups from the early stage (milky quartz) range from 260 to 288 °C and 5.1 to 12.7 wt.% NaCl equiv., respectively. In the intermediate stage (white quartz), the fluid temperature and salinity range from 223 to 247 °C and 3.5 to 9.5 wt.% NaCl equiv. The δ 34 S fluid values of pyrrhotite and chalcopyrite range between 5.7 and 9.2‰. The southern Chah-Palang mineralization is related to a magmatic geothermal system. δ 18 O fluid (8.61 to 3.44‰ values) suggest that the early-stage ore-forming fluids were primarily extracted from magmatic fluid, with the addition of meteoric water in the intermediate stage. Early-stage apatite precipitated mainly from a volatile-rich magmatic fluid. The oxygen isotopic data, fluid inclusions, and mineral chemistry of the apatite samples indicate that the ore-forming fluids of the vein-type southern Chah-Palang deposit were dominated by magmatic-hydrothermal fluids during the early stage and that meteoric water was added during fluid evolution.