Geology, Geochemistry, and Geochronology of the Giant Pelitic Mafic-Type Karaburun Volcanogenic Massive Sulfide Deposit (Central Pontides, Turkey)

Abstract

Anatolia hosts different types of volcanogenic massive sulfide (VMS) deposits in the Eastern Pontides, Bitlis-Zagros suture zone, and Central Pontides. The recently discovered giant Karaburun deposit (similar to 125 million tonnes [Mt] grading 1.16 wt % Cu, 0.25 wt % Zn, and 0.05 wt % Co) of the Central Pontides is the largest VMS deposit in Turkey. The mineralization is hosted within the greenschist metamorphosed rocks of the Cangaldag Metamorphic Complex. Mineralization is associated with metamorphosed volcaniclastic, clastic detrital sedimentary, and deep marine sedimentary rocks, as well as crosscutting submarine mafic dikes and/or sills. The deposit mainly occurs as a stratiform Cu-Zn +/- Co sheet-like and tabular body that contains disseminated, banded, pyritic clastic, semimassive, and massive sulfide textures. The primary ore minerals are pyrite, chalcopyrite, sphalerite, magnetite, and trace galena. Supergene covellite, bornite, chalcocite, and digenite are observed. Surface weathering and oxidation resulted in hematite, goethite, lepidocrocite, malachite, and water-soluble copper minerals. Mineralization-stage pyrites yield an age of 163.6 +/- 7.1 Ma (Re-Os; Late Jurassic; lowermost Oxfordian), which is consistent with the ages of different components in the same rifting system. The delta S-34 values of pyrites range from 3.07 to 5.10 parts per thousand, suggesting a mixed origin between basalts and thermochemically reduced seawater sulfate. Late Cretaceous metamorphism caused brittle and ductile deformation within the sulfide phases, promoting the remobilization of metal-bearing minerals. Subsequent deformation phases likely led to the dismemberment and juxtaposition of mineralized levels. Together, the data indicate that Karaburun is a pelitic-mafic replacement-type VMS deposit that formed in a back-arc basin environment of the Jurassic ensimatic arc-back arc-rift system.