FLUID INCLUSION EVOLUTION AT DARALU PORPHYRY COPPER DEPOSIT, SOUTHEAST IRAN

Daralu porphyry copper deposit is located 130 km south of Kerman, southeast Iran and lies in southern part of Urumieh–Dokhtar magmatic arc. The deposit is associated with granodioritic intrusive of Oligo-Miocene age which intruded Eocene volcano-sedimentary rocks. The Daralu stock emplacement in several pulses as well as copper mineralization was accompanied by both potassic and silicic-phyllic alterations. Four types of hypogene alteration are developed in the Daralu deposit: potassic, propylitic, argillic and silicic-phyllic. Hydrothermal mineralization studies within the Daralu deposit show four types of hydrothermal mineralization: (1) hypogene; (2) supergene; (3) oxidized and leached; (4) gossan. Three principal types of vein mineralization have been identified: Type I which is characterized by quartz, chalcopyrite, magnetite and pyrite with minor bornite and molybdenite; Type II contains chalcopyrite (as the main copper mineral in the Daralu deposit), pyrite and quartz, with traces of molybdenite; and Type III consisting of quartz and pyrite, with minor chalcopyrite.

Four types of fluid inclusions are present in quartz veins associated with the Daralu deposit: (1) mono-phase vapor, (2) liquid + vapor, (3) vapor + liquid and (4) multi-phase solid. Halite and hematite are the principal solid phases. Fluid inclusion data at Daralu showed that the two-phase liquid-rich fluid inclusions represent lower homogenization temperatures between 127 and 293^oC and low to moderate salinity (1.05 to 12.07 wt. % NaCl equivalent). The two-phase vapour-rich fluid inclusions demonstrate homogenization temperatures from 476 to 486 ^oC and moderate salinity (average 21.55 wt. % NaCl equivalent). The multi-phase solid inclusions exhibit moderate to high homogenization temperatures ranging from 231 to >510 ^oC and moderate to high salinity (30.4 to 59.66 wt. % NaCl equivalent). The coexistence of vapor-rich two-phase and multi-phase solid inclusions suggests that these fluid inclusions resulted from trapping of boiling fluids. Salinity–homogenization temperature relationships indicate two groups of fluids with early hydrothermal fluids represented by high temperature and high salinity interpreted to have caused potassic alteration and low temperature and low salinity fluids typical of silicic-phyllic alteration.