The late Miocene Öksüt high sulfidation epithermal Au-Cu deposit, Central Anatolia, Turkey: Geology, geochronology, and geochemistry

Abstract

The Öksüt high sulfidation (HS) epithermal Au (-Cu) deposit (35.32 million tonnes of ore at 1.22 g/t Au) is located in the Central Anatolian Volcanic Province (CAVP) at the south-eastern segment of the Central Anatolian Crystalline Complex (CACC). The deposit is hosted by large hydrothermal breccia bodies and hornblende-rich basaltic andesite porphyry of the Develidag Volcanic Complex (DVC), which were pervasively altered to form silicification and argillic assemblages. The host rocks and mineralization are covered by post-mineral pyroxene-rich basaltic andesite of DVC. The volcanic rocks have a medium-K calc-alkaline affinity similar to regional volcanic rocks of the DVC. The gold and copper mineralization is mostly associated with quartz and primary sulfides hosted by silicification and argillic alteration particularly quartz-alunite cemented breccias and subsequently enriched by supergene oxidation processes causing destabilization of the primary sulfides. The LA-ICP-MS zircon U-Pb geochronology indicates a range of 206Pb/238U ages between 5.4 and 6.0 Ma with an average mean age of autocrystic grains of 5.73 ± 0.06 Ma for the host hornblende-rich basaltic andesite porphyry and 5.67 ± 0.07 Ma for the post-mineralization basaltic andesite cover. The high-precision CA-ID-TIMS analysis of the youngest grains from both rock types defines ages 5.778 ± 0.013 Ma and 5.700 ± 0.019, respectively, which bracket the ore mineralization between 5.791 and 5.681 Ma, including the error uncertainty. Consequently, the Öksüt gold mineralization took place in a very narrow lifetime of 78 ± 32 Ka. This is the youngest age for an economic gold deposit in Turkey. © 2020 Elsevier B.V.