Volcanogenic massive sulfide (VMS) deposits of Turkey

Abstract

Volcanogenic massive sulfide (VMS) deposits of Turkey occur in three tectonically distinct regions: (I) Kuroko-type deposits in the eastern Pontides Tectonic belt (EPTB); (II) Cyprus-type VMS deposits occur both in Küre area (Kastamonu) and along the Bitlis-Zagros Suture Zone (BZSZ), and (III) Besshi-type VMS deposits in the Hanönü–Taşköprü area (Kastamonu). The Kuroko type VMS deposits are all associated with Late Cretaceous felsic volcanics consisting mainly of dacitic and rhyolitic lavas and pyroclastics that outcrop within a narrow zone running parallel to eastern Black Sea coast and represent the axial zone of a paleo-magmatic arc. Subtypes of the deposits include Cu-, Zn-Cu-, Cu-Zn-, Zn-Pb-Cu metal associations. These deposits are typically mined for Cu, Zn, and Pb. Some of them may also contain significant gold (e.g. Cerattepe and Hod deposits - Artvin) and silver (e.g. Köprübaşı deposit - Giresun). The Cyprus type deposits occuring along the BZSZ are all allochthonous and associated with mafic volcanics of supra-subduction ophiolites: (I) Middle Eocene Maden Complex – a pile of mafic volcanics, pelagic sediments with limestone blocks and (II) Late Triassic-Late Cretaceous Koçali Complex – a sequence of tectonically imbricated slices of pelagic rock suites, platform carbonates, clastic sediments, serpentinites, and mafic volcanics. Major occurences include Madenköy (Şirvan-Siirt) - currently the largest known VMS deposit in Turkey with about 40 Mt reserve and Maden (aka Ergani) (Maden-Elazığ) area deposits, both hosted by the Maden Complex and Ortaklar (Gaziantep) hosted by the Koçali Complex. The VMS deposits occurring in the Küre area are also allochthonous and are all hosted within mafic volcanics-black shales of Late Triassic Küre Complex, a fairly thick pile of thrust-imbricated deep-sea sediments, intercalated with a dismembered supra-subduction ophiolite. Major past and current producers include Aşıköy, Toykondu, Kızılsu, and Bakibaba deposits. The Besshi-type VMS deposits are fairly recent discoveries. They only occur in Hanönü-Taşköprü area and hosted by Akgöl Formation, which consists of low-grade metamorphic siliciclastic sedimentary rocks within the Middle Jurassic Çangaldağ Complex comprising ensimatic island arc volcanics and front-arc basin sediments, remnants of oceanic crust, and volcano-clastics. Major examples include Zeybek, Hanönü, Gökırmak, and past producer Cozoğlu deposits, which are typically low grade but may reach up to 25 Mt.