Ophiolite-Hosted Copper and Gold Deposits of Southeastern Turkey: Formation and Relationship with Seafloor Hydrothermal Processes

Abstract

The paper documents evidence about the physical and chemical controls on the behaviour of Au and Cu sulphide deposits in fossil seafloor hydrothermal systems of SE Turkey. Observations from actively forming sulphides at mid-ocean ridges (MOR) and in back-arc environments are compared briefly with ancient analogues of gold and pyritic copper deposits such as Kisecik, Ergani and Siirt-Madenköy, formed at mid-oceanic ridges, or possibly at seamounts and back-arc settings. Many ophiolite-hosted Au- and Cu-deposits, of various sizes, are known to exist along the Bitlis-Zagros Suture Zone (BZS), the boundary between Anatolian and Arabian plates in SE Turkey. These deposits are associated with Cretaceous intra-oceanic supra-subduction zone ophiolitic slabs, such as Kızıldağ, the Bäer-Bassit massif (the southern extension of the Kızıldağ Massif in Syria), and the Yüksekova and Berit ophiolite bodies, which tectonically overlie the Mesozoic platform carbonates and Palaeozoic sediments of the Arabian plate. East of the BZS, ophiolitic segments of Tertiary age are strongly mineralized. Several Au and Co-Ni bearing pyritic Fe-Cu oxide and sulphide deposits associated with chloritized and spilitized basaltic pillow lavas or sheeted dykes crop out along the BZS. Volcanics associated with mineralisation closely resemble MOR sequences, sedimented ridges and back-arc environments in spreading centres of island arc systems. Ophiolitic rocks and the mineralogy of associated alteration are similar to characteristics of modern mid-oceanic ridge mineralization along the East Pacific Rise (EPR), Mid-Atlantic Ridge (TAG hyrothermal field) and Red Sea (Atlantis-II Deep).