Occurrence of native copper mineralization within the volcanic host rocks of the Garmabe Paein Cu-Ag volcanogenic massive sulfide deposit, southeast of Shahrood

The Garmabe Paein copper-silver volcanogenic massive sulfide (VMS) deposit is located 290 km southeast of Shahrood and occurred within the Upper Cretaceous volcano-sedimentary sequence in the Sabzevar subzone, north-east of Iran. Native copper mineralization occurred within the Cretaceous volcanic host rocks of the Garmabe Paein deposit including andesite-basalt with amygdaloidal texture, trachyandesite and volcanic breccia, and Paleocene conglomerate, as vein-veinlets and disseminated forms. Geochemical studies indicate that the volcanic rocks have basaltic compositions and calc-alkaline nature, deposited within a back-arc basin. Major wall rock alterations are dominated by chloritic and minor zeolitic mineralization. This study shows that diagenesis and burial process in the host volcano-sedimentary sequence produced relatively hot and brine fluids which leached copper from the volcanic rocks and deposited as native copper under reduced conditions within the Late Cretaceous andesit-basalt and trachyandesite and Paleocene conglomerate. Considering host rock types, mineralogy and alteration, the native copper mineralization in the Garmabe Paein deposit show most similarity with the native copper mineralization in the basaltic rocks (Michigan-type), which occurred slightly after formation of the Garmabe Paein VMS deposit during diagenesis, burial metamorphism and uplift.