Evidences of probable porphyry Cu-Au mineralization in Namegh area, Northeast of Kashmar: geology, Alteration, mineralization, geochemistry, and fluids inclusion studies

Namegh area is located northeastern Kashmar, Khorasan Razavi province, and centeral part of of Khaf-Kashmar-Bardaskan magmatic belt. Geology of the araea is covered by Eocene volcanic rocks having andesite to rhyolite composition, which are intruded by subvolcanic intrusions with monzonite, monzodiorite, and diorite composition. All of units are affected by well development alteration, which are silicified-sericitic, moderate argillic, and propylitic alteration zones. Mineralization is occurred as stockworck and disseminated. Primary minerals include chalcopyrite, pyrite, magnetite, and gold and secondary minerals include goethite, hematite, malachite, and azurite. High anomaly of Cu (up to 1%) and Au (up to 12 ppm) are correlated with strong silicified-sericitic alteration. Based on fluid inclusion studies, formation temperature of mineralization is between 404 to 551 ºC and it is occurred from NaCl-, and CaCl2-bearing fluid with 15 to 23 wt. % NaCl equivalent salinity. Decrease of temperature and HCl activity during boiling time and decrease of temperature due to mixing of magmatic and meteoric fluids could be the most important factors for formation of mineralization. Evidences of tectonic setting, lithology, development and types of alteration, mineralization form and limited outcrops, types of ore minerals, geochemical anomalies, types of fluid inclusions and temperature and salinity of fluid indicate the mineralization of Namegh is probably upper level of porphyry Cu-Au deposit. The Khaf-Kashmar-Bardaskan belt can be one of the most important porphyry deposits metallogenic zones of Iran due to tectonic setting and magmatic-mineralization evidences, which needs detailed exploration in future.