Miocene tectono-magmatic events and gold/poly-metal mineralizations in the Takab-Delijan belt, NW Iran

Abstract

The Takab-Delijan (T-D) magmatic belt in NW Iran is a part of the Zagros orogenic belt which has imminence with epithermal, porphyry and carlin types of mineralization. This magmatic belt has been classified into 3 different phases by radiometric dating, including early (16–24 Ma), middle-late (10–12 Ma), and late Miocene (8 > Ma), among which the gold/basemetal mineralization is related to the first two phases in this area. The lower Miocene phase formed during the formation of a metamorphic core complex and upwelling basement in the form of synextentional magmatism. This magmatic event is shaped in an extensional regime within shallow marine basins which are correlated with the limestone formation of Qom Formation (QF) in a pre- to syncollisional environment. This volcanism (edifice) acceded to the surface rapidly via NW extensional faults and made stratovolcanic structures in the Takab and Delijan areas. These complexes have been formed by sequences of pyroclastic and lava flows with a composition of dacite to andesite and trachyandesite that are crosscut by microdiorite porphyritic subvolcanic. These epithermal-porphyr systems are related to the Cu ± Au ± Ag deposits. The main phase of gold mineralization is related to the magmatic phase with middle-late Miocene and the age of ~10.7–12 Ma. The geological environment for forming this magmatic phase is related to the extensional- compressional regime by the right-lateral strike-slip shear zone during shortening, folding, and thickening in syn- to post-collisional events. The magmatism is in the form of dacitic to rhyolitic domes on the surface. The gold/silver mineralization is associated with the hydrothermal metal suite of As, Sb, Te, Pb, and Zn, and it is characterized by very low Cu contents of subvolcanic. The final stage of tectonic evolution events is the thrusting of prior normal faults and exhumation in the late Miocene-Pliocene age which is together with post-collision magmatism.