Petrography, geochemistry and mineral chemistry of Astarghan granodioritic stock, Kharvana, East-Azarbaidjan

The Astarghan copper-gold deposit is located about 50 km north of Tabriz, southeast of Kharvana, East-Azarbaidjan. The most important lithologic units in the area are a hypabyssal prophyritic granodioritic intrusive stock (Oligo-Miocene) and flysch-type sedimentry sequence consisting of limestone, limy sandstone and marl (Paleocene-Eocene). The plagioclases range in composition from oligoclase to andesine and K-feldspars are mainly orthoclase. Amphiboles are principally of calcic-type and vary in composition from magnesio-hastingsite to edenite. The stock is of I-type granites and meta-aluminous, belonging to high-k calc-alkaline to shoshonitic magma series, which are related to post-colission volcanic arcs. Intrusive body shows enrichment in elements such as La, Nd, Rb, U, Pb, Zr, Cs and P and depletion of Ce, Pr, Ta and Nb. LREEs relative to HREEs are also enriched. Electron probe micro-analyses of ore minerals proved the presence of native gold within sulfides (stibnite and tetrahedrite) and quartz veinlets. The highest gold content is within the structure of sulfosalts (tetrahedrite-tenantite) and low-temperature sulfides (stibnite). The presence of high values of gold-tracing elements such as Sb, Hg, Bi and As within the studied ores is in accordance with the studied geochemical halos of these elements in the area which, in turn, may indicate a low temperature for the formation of the ore minerals.