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.
Highlights
Turkey is a part of the Tethyan orogenic belt and hosts numerous porphyry- and epithermal-style Au deposits (Fig. 1A), which were formed during the closure of the northern and southern branches of the Neotethys Ocean, including subduction, subsequent post-collision, and extension events of western Tethyan orogeny since the Late Cretaceous
Most economic gold deposits (Fig. 1A, Table 1), including the Kisladag porphyry (862 Mt @ 0.52 g/t Au), Efemcukuru intermediate sulfidation (IS) (14.61 Mt @ 6.63 g/t Au), Inlice high sulfidation (HS) (0.63 Mt @ 2.36 g/t Au) and Oksüt HS (35.32 Mt @ 1.22 g/t Au, this study) deposits are hosted by Miocene to Pliocene volcanic-volcaniclastic rocks exposed at the northern and western margin of the Menderes massif and Afyon zone to the west of the central Anatolian crystalline complex (CACC, Fig. 1A)
Pb measurements were performed on a Thermo TRITON (TRITON Plus at ETH Zurich) thermal ionization mass spectrometer; Pb was measured in dynamic mode on a MasCom secondary electron multiplier and U was measured as UO2 in static mode on Faraday cups equipped with 1013 O resistors
Summary
Turkey is a part of the Tethyan orogenic belt and hosts numerous porphyry- and epithermal-style Au deposits (Fig. 1A), which were formed during the closure of the northern and southern branches of the Neotethys Ocean, including subduction, subsequent post-collision, and extension events of western Tethyan orogeny since the Late Cretaceous. These events resulted in thermal peaks magmatism asso ciated with porphyry Cu, epithermal Au and skarn deposits roughly in four main periods: Late Cretaceous, middle Eocene, Oligocene and Miocene (Baker, 2019; Kuscu et al, 2019). The ages of these deposits are: Efemcukuru (13.17 ± 0.25 Ma; Boucher, 2016), Kisladag (14.49 ± 0.06 Ma; Baker et al, 2016), Afyon-Sandikli (11.2 ± 05 Ma; Sonmez and Kuscu, 2020), and Inlice – Dogankoy (8.98 ± 0.11 Ma; Kuscu et al, 2019)
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