Gold Deposits in the Sanandaj-Sirjan Zone: Orogenic Gold Deposits or Intrusion-Related Gold Systems?

Most of the known large gold deposits in Iran are located along the SanandajSirjan Zone, western Iran, which hosts a wide range of gold deposit types. Gold deposits in the belt, hosted in upper Paleozoic to upper Mesozoic volcano-sedimentary sequences of lower greenschist to lower amphibolite metamorphic grade, appear to represent mainly orogenic and intrusion-related gold deposit types. The largest resource occurs at Muteh, with smaller deposits/occurrences at Zartorosht, Qolqoleh, Kervian, Qabaqloujeh, Kharapeh, and Astaneh. Although a major part of the gold deposits in the SanandajSirjan Zone are related to metamorphic devolatilization, some deposits including Muteh and Astaneh are related to short-lived disruptions in an extensional tectonic regime and are associated with magma generation and emplacement. The age of gold ore formation in the orogenic gold deposits is Late Cretaceous to Tertiary, reflecting peak-metamorphism during regional CretaceousPaleocene convergence and compression. The Oligocene to Pliocene age of most intrusion-related gold systems is consistent with the young structural setting of the gold ore bodies; these deposits are sequestered along normal faults, correlated with Middle to Late Tertiary extensional tectonic events. This relationship is comparable to the magmatic-metallogenetic evolution of the Urumieh-Dokhtar magmatic arc, where the number of different types of gold-copper deposits and the magnitude of the larger ones followed development of a magmatic arc. The appropriate explanation may be related to two different stages of gold mineralization consisting of a first compressional phase during the Late Cretaceous to Early-Middle Tertiary, which is related to orogenic gold mineralization in the Qolqoleh, Kervian, Qabaqloujeh, Kharapeh, and Zartorosht deposits, and the extensional phase during the Eocene to Pliocene that is recognized by young intrusion-related gold mineralization in the Muteh and Astaneh deposits.