LAUSR

Abstract The Rangraz copper deposit (5 Mt @ 0.83% Cu) is located 20 km north of Saveh city, Markazi Province, Iran, in the central Uromieh-Dokhtar volcano-plutonic belt. Host rocks are mainly composed of Eocene volcanic and volcaniclastic rocks that have been intruded by late Eocene quartz monzodiorites and basaltic-andesitic dikes. The dominant copper-related hydrothermal alteration types include silicification, sericitization, and chloritization-kaolinitization. The ore body takes the form of fault-hosted, NW-SE-striking lodes comprising pyrite, chalcopyrite, bornite, specular hematite and magnetite as the principal hypogene ore minerals. Gold (maximum spot assays of up to ca. 0.37 ppm Au) and silver (up to 20.6 ppm Ag) have also been recorded. The ore minerals are mainly confined to veins or veinlets showing crustiform, colloform, open space-filling, dissemination and replacements characteristics in texture. The principal gangue minerals are quartz, barite and calcite. Most of the fluid inclusions identified in quartz-chalcopyrite ± specular hematite veins contain two liquid and vapour phases at room temperature. The primary and pseudo-secondary fluid inclusions have low to intermediate homogenization temperatures between 134 and 338°C and salinities between 3.55 and 16.89 wt. % NaCl equivalents. The fluid inclusion data are consistent with a two-stage evolution of the mineralising system with initial metal precipitation at crustal depths of