GEOCHEMISTRY, FLUID INCLUSION THERMOMETRY AND PETROLOGY OF HIRED INTRUSIVE REALTED GOLD PROSPECTING, EASTERN IRAN

Hired the largest gold prospect is located 150 km south of Birjand, in eastern Iran. Host rocks are mainly Eocene andesites and dacites and some Jurassic, Cretaceous and Paleocene sedimentary rocks. Two groups of Oligocene-Miocene meta-aluminous granitoids intruded the Eocene volcanic and older sedimentary rocks. One group (reduced type) includes high-K to Shoshonite series biotite ± muscovite ± hornblende granites, granodiorites and monzonites, with magnetic susceptibility less than 30 ×10-5 SI. The second group (oxidized type) includes medium to high-K series biotite + hornblende + magnetite gabbros and diorites, with magnetic susceptibility greater than 300 ×10-5 SI.

Stockwork mineralization is associated within reduced granitoids. Several types of veinlets are found, including: 1. quartz-tourmaline-pyhrotite-arsenopyrite-gold; 2. quartz; 3. quartz-arsenopyrite-pyhrotite; 4. quartz-tourmaline-carbonate; and 5. tourmaline. Distal from the reduced intrusive rocks, skarn, replacement and vein type mineralization was formed. Paragnesis of veins in the distal area involves quartz–pyrite ± galena ± sphalerite ± chalcopyrite ± arsenopyrite ± calcite ± gold. Main alteration zones are tourmaline-sericite, tourmaline-chlorite-carbonate, quartz-tourmaline-sericite and propylitic. Propylitic alteration is dominant and covers a large area. Tourmaline is mainly found within stockwork veins.

The Au grades are between 400 to 5600 ppb, As 100-3000 ppm, Sb 30-200 ppm, Pb 70-2000 ppm, Sn 30-850 ppm and Cu 60-800 ppm. Primary fluid inclusions are two-phase liquid-rich types. Temperature of homogenization of primary fluid inclusions in quartz associated with tourmaline was > 500°C, associated with sulfides >500°C, with tourmaline-sulfide between 325-365°C, and with arsenopyrite between 151-247°C. Mineral paragenesis (arsenopyrite-pyhrotite) and stockwork mineralization within the reduced granites all indicate that Hired is a reduced intrusion related gold deposit. Besides Au, the area has potential for Sn mineralization.