Writers : Rastad.E , Niroomand.Sh , Emami.M.H ,and Rashid Nezhad Omran.N
Refference : Geosciences Scientific Quarterly Journal,No.:37-38,P.:2
Publishing Year : 1380

Abstract :
Dashkasan antimony-arsenic-gold deposit is located in west Iran , 42 km NE of Qorveh (Kordestan provice). The area is a part o Sanandaj- Sirjan magmatic-metamorphic zone. Based on geological observations, the oldest rock units in the area belong to the Jurassic serie and are slates, phyllites and quartzites. The youngest unIts are Neogene volcano-clastic conglomerates, basaltic flows, block lavas anc Quaternary agglomerates. The plutonic rocks in the area consist of a Neogene (Pliocene?) calc-alkaline microgranite-microgranodiorite intrusive with microgranular porphyritic textures. The subvolcanic equivalent of these plutonic rocks, is represented as Agh Dagh and Sari Dagh dacite-rhyodacite domes.. Dashkasan mine is considered as a vein-type deposit in which its related mineralization is controlled by tectonic structures. The deposit is hosted by dacite, rhyodacite and microgranodiorite subvolcanic rocks which are mainly associated with silicic, argillic, and pyritic alterations. The ore parageneses in the veins includes quartz, stibnite, pyrite, realgar, orpiment, pyrrhotit, chalcopyrite, bornite, galena, boulangerite, aurostibite(?), gold, stibiconite, kermesite and iron-hydroxide. The Gold content of the veins ranges between 55 and 266ppm, whereas in sulfide-silicic zone, it ranges from 10 to 18 ppm. Gold grains are between 10 and 150 microns in diameter commonly occurring with quartz and in smaller sizes within the oxidized pyrites. Scanning Electron Microprobe (SEM) studies display quantities of Sb, Ag and Hg within the gold grains. The analytical results for samples from six lithogeochemical profiles vertically cutting the main stibnite veins in Agh Dagh and Sari Dagh areas indicate that high-grade gold is limited to stibnite veins and also to silicic-pyritic alteration zones, Fluid inclusion studies reveal that homogenization temperatures range between 183 C and 255 C and salinity from 8.9 to 188 wt % NaCl equivalnt. Field observations and laboratory studies show a close relationship between the antimony-arsenic-gold mineralization, and silicic solutions drived from subvolcanic body in the area. II is therefore suggested that, the mineralization belongs to eoithermal arouo and acid-sulfate tvoe.
Subject List : Genesis