Occurrence of copper mineralization of Abgareh deposit based on geology, mineralogy and geochemical evidences, south of Damghan

The Torud-Chah Shirin volcanic-sedimentary arc, in the south of Kavir-e-Chah Jam depression (SE of Damghan), hosted many Pb, Zn, Cu, Ag and Au occurrences and deposits. Abgareh copper deposit is located in the northeastern part. Field and petrographic studies indicate that deposit area consist of andesite, basaltic andesite and basalt rocks and to a lesser extent crystal tuffs with a middle–upper Eocene age. The rocks are of high-K, calc-alkaline to shoshonitic in nature, and are formed in a magmatic arc setting in a subduction zone. According to the field observations and mineralogical studies, the mineralization in the region occurred in two stages: hypogene and supergene and weathering. Hypogen zone minerals are generally pyrite, chalcopyrite and bornite, while chalcocite, covellite, malachite and chrysocolla are considered as the main minerals in the supergene zone. Fractures resulting from faults in the rocks of the region created a favorable location for the influence of hydrothermal solution and it is considered as the main controller of mineralization. Most of the textures observed in the mineralization include vein-veinlets, open space filling, radial, replacement and disseminated forms. Geochemical studies indicate that copper has the most relative correlation with silver. Since silver has not been found as an independent crystalline phase, therefore copper was replaced by silver in chalcopyrite and chalcocite. Compared with chondrite and primitive mantle normalizing diagrams, the studied rocks show significant enrichment with respect to LREE and LILE and depletion in HREE and HFSE and negative anomalies in Ti and Nb elements. Based on the relevant diagrams, differential crystallization of mantle rocks had the essential role in the evolution of the studied rocks which were probably derived from enriched mantle. Based on petrography, structural control of mineralization, alteration type and its extention and simple mineralogy, it can be concluded that mineralization at Abgareh district has characteristics of an individual mineralization system. This system is related to evolution of hydrothermal fluid mineralization resulted in vein-type Cu mineralization.