Geology of the Aftabrou Polymetallic Deposit, Saveh, Iran

Abstract

Aftabrou polymetallic prospect is located at the contact of Oligo-Miocene calcalkaline granodioritic to dioritic and Eocene andesitic to basaltic volcanic complex in middle section of Urumiyeh-Dokhtar volcanic arc in NW of Saveh city. Petrographic study indicated that the volcanic rocks are mostly: lava and tuff. Composition of lavas is mainly andesite and tuffs are mainly composed of dacite to rhyodacite. Major phenocrysts in these rocks are plagioclase, clinopyroxene, hornblende and opac minerals. Petrographic and geochemical studies indicated an I-type granitoid and, calcalkaline magmatism associated with continental margin of subduction zone. This study determined three mineralization subzones of 0.2% -5.3% Cu, 0.02 -1.31 ppm Au and 1.2% -3.9% Zn. Fluid inclusion studies on quartzic veins associated with magmatism, demonstrated that homogenization temperatures of this mineralization fluid are between 170˚C to 330˚C, the salinity of the system is between 11.7 to 23.5 weight percent, density of this fluid is 0.8 -1.1 g/cm 3 and is occurred in depth of less than 1800 m of surface. Fluid inclusion studies suggested that formation of mineral deposit is simple cooling and mixing with atmospheric water and type of Aftabrou deposit is IOCG. In this base, it is assumed that this IOCG mineralization is occurred associate with magmatism that is formed as a result of Neo-Tethys oceanic subduction beneath the Central Iran zone which is replaced in the Orumieh-Dokhtar magmatic arc.