Economic Geology
Behzad Hamamipour; H. A. Tajeddin; Leila Barahmand
Abstract
The Sebandoon gold deposit is located 40 km north of the Bardaskan in the northern part of the Central Iran. The rock units exposed in the area consist of upper Cretaceous volcano-sedimentary sequences of trachyte-trachyandesite, andesibasalt,tuff and carbonaceous shale which intruded by post Eocene ...
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The Sebandoon gold deposit is located 40 km north of the Bardaskan in the northern part of the Central Iran. The rock units exposed in the area consist of upper Cretaceous volcano-sedimentary sequences of trachyte-trachyandesite, andesibasalt,tuff and carbonaceous shale which intruded by post Eocene syenite-quartz monzonite subvolcanic intrusions and diabasic dikes. The main gold reservoir in the Sebandoon deposit has occurred in cone-shaped and mostly in the trachyte-trachyandesite lava with dimensions of 90×150 m in the surface which continue up to the depth of 70 m. The hydrothermal alterations occurred in the deposit area include silicic, sulphidic, partly argillic (supergen) and propylitic which two former contains most of the high grade gold ores. The main ore structures and textures in the deposit are vein-veinlets (stockwork) and breccia which consists of quartz, sulphide minerals and rare adularia. Primary ore mineral assemblages of the deposit are simple and consist of pyrite, sphalerite, chalcopyrite, bornite, galena, arsenopyrite and gold. Covellite, chalcocite and iron hydroxides are secondary minerals in the deposit. Gold grains with less of than 60 microns in size has been found as inclusion in pyrite and chalcopyrite, in sulfides rims and intergrowth with quartz. Fluid inclusion studies on ore-bearing quartz reveal that majority of primary inclusions are liquid-rich two-phase (LV). The studies indicate homogenization temperatures between 165 and 254°C and salinity between 0.9 to 7.8 wt% NaCl eq. Comparison of the main characteristics of the Sebandoon deposit with epithermal gold deposits reveals that the geology, alteration, ore mineralogy, geochemical characteristics and fluid inclusions of the Sebandoon gold deposit is similar to low to intermediate-sulphidation type epithermal deposits.
