Eocene Masjeddaghi porphyry Cu-Au deposit; an example of island arc porphyry type deposit in NW Iran

The Masjeddgaghi Cu-Au deposit is located at the southeast of the Arasbaran zone, NW Iran, to the south of Lesser Caucasus. Mineralization in Masjeddaghi is associated with an Eocene dioritic subvolcanic pluton intruded into volcanic and sedimentary rocks. The Masjeddaghi intrusive is high K, calc alkaline- and meta-aluminous, and formed in post magmatism stage, in an island arc setting. Hydrothermal alteration is distinguished by potassic core marked by secondary biotite, and K-spar that grades outward into a chlorite-rich propylitic halo The ore mineral include chalcopyrite, associated with minor chalcocite, bornite, tetrahedrite, and trace amounts of molybdenite. Pyrite and magnetite are common associate. The Masjeddaghi deposit is elliptical in view, 500m in 400 in diameter, and mineralization has been traced for several hundred meters from surface exposures.. 40Ar/39Ar geochronology on secondary biotite from the potassic alteration zone indicates that mineralization, and accordingly the emplacement and crystallization of the Masjeddaghi porphyritic intrusion occurred 54.07 ± 0.53 Ma ago. Masjeddaghi ore deposit shows geology, mineralization and alteration characteristics similar to island arc porphyry type systems.