Formation conditions and geochemistry of the Tütün Tepeleri (Baskil-Elazig/Türkiye) Fe-oxide-Cu-Au (IOCG) mineralization

Abstract

The Tütün Tepeleri Fe-Oxide-Cu-Au (IOCG) mineralization is located in the Eastern Taurus Mountains (Baskil-Elazığ/Turkey) and it is associated with Baskil magmatites (diorite, gabbro and tonalite) cut by Late Cretaceous Bilaser Tepe magmatites (quartized diorite, granite, granodiorite, tonalite porphyry, monzosyenite, monzonite, aplite and diorite porphyry). Baskil Magmatites are Coniacian-Santonian (82–86 Ma), calc-alkaline in character and I-type. Bilaser Tepe Magmatics are Campanian (73–74 Ma) and represent an extensional environment after the collision of oceanic arc and the Taurus platform. In this study, the Sodic-calcic alteration zone in the Tütün Tepeleri region, which was determined as Porphyry type mineralization by different researchers, was determined for the first time and the mineralizations were evaluated in terms of Fe-Oxide-Cu-Au (IOCG) deposits. Three types of alteration zones have been identified in the region, including the sodic-calcic alteration zone. These are sodic-calcic (tremolite-actinolite, albite, epidote, chlorite, magnetite), potassic (biotite, quartz, chlorite, K-feldspar, anhydrite) and sericitic (sericite, carbonate, quartz, chlorite, illite) alterations. Sodic-calcic alteration is more widespread in the region than >1 km², reaches thicknesses of 500 m, and is occasionally overlain by potassic alterations, just like similar Fe-Oxide-Cu-Au (IOCG) deposits in the world. Tütün Tepeleri mineralizations are in the form of rare magnetite veins with intense magnetite dispersion within the sodic-calcic alteration developed in diorites. Mineral paragenesis is in the form of magnetite, molybdenite, pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, hematite, malachite and azurite, and Ti content in magnetites is determined as 0.13–0.64%. Fe content is 20.13% on average. Formation temperatures in fluid inclusions measured in ore-bearing quartz veins are 320.3 °C on average and salinity is 11.32% NaCl equivalent on average. Isotope analysis results of these mineralizations show δ³⁴S_pyrite = 6–8.9; δ³⁴S_c.pyrite = 3.8–5.5; δ¹⁸O_quartz was determined in the range of 10.8–13.2 and δD = (−37) – (−53). When the alteration types determined with isotope analysis results showing that the mineralization occurred in a magmatic-hydrothermal system, the low Ti content in the magnetites, the formation temperature and salinity values are evaluated together, it was anticipated that Tütün Tepeleri mineralization is an example of Fe-Oxide-Cu-Au (IOCG) deposits formed in a hydrothermal-magmatic system.