Microchemical analyses of the alteration and sulfide minerals associated with the Şirindere gold mineralization at the Central Menderes Massif, West Turkiye

The present study focuses on the mineral chemistry data of hydrothermal alteration and sulfide minerals that are related to gold mineralization in the Şirindere area of the Ödemiş-Kirazlı tectonic unit of the Menderes Massif polymetamorphic complex, located in WestTurkiye. The study area contains paragneiss, orthogneiss, and various types of schists (muscovite-, tremolite-, and actinolite-schists) of the Pan-African basement rocks that constitute the central part of the Menderes Massif complex. Additionally, there are Permian garnet-mica schist and marble lenses, as well as Triassic orthogneiss, which are part of the Paleozoic cover series. The Şirindere gold mineralization occurred as gold-bearing quartz carbonate veins hosted within the garnet-mica schist. The veins exhibit boudinage patterns that run parallel to the schistosity direction within the shear zone, which has a N-S orientation, include two types of quartz crystals.The main types of hydrothermal alteration that occurred adjacent to the auriferous quartz-carbonate veins are silicification, chloritization, and sericitization, with subordinate carbonatization alteration types. The ore mineralogy includes pyrite and chalcopyrite associated with free native gold and native copper. The minerals albite, biotite, calcite, chlorite, garnet, sericite, and quartz have been analyzed using an electron microprobe, together with chalcopyrite, pyrite, and gold. According to the EPMA data, the biotite is categorized as magmatic and re-equilibrium Fe-biotite that originated from both crustal and crust-mantle sources within the peraluminous suites. Chlorite is mostly classified as Fe-chlorite (chamosite), which is formed within a temperature range of 249°C to 355°C with an average temperature of 275°C. Sericite has a larger proportion of muscovite (XMs) ranging from 0.89 to 0.96 (average XMs = 0.94), with a phengite content ranging from 0.35% to 1.55%. The EPMA trace element analyses of the pyrite minerals are plotted in the fields of magmatic-hydrothermal and carlin-type gold deposits. This pertains to sulfur derived from juvenile magmatic and/or upper mantle sources with slightly sedimentary origins. Furthermore, these pyrite minerals serve as the primary source of gold, as they include small mineral inclusions like visible gold and chalcopyrite. The pyrite has high amounts of gold, with maximum values reaching 270 ppm. It is hypothesized that the pyrite undergoes longer-term crystallization and co-precipitates with native gold and chalcopyrite. The Şirindere region has been affected by many metamorphic episodes and deformational events caused by various orogenies, including M1, M2, M3, and M6, as well as D3 and D4. During M6, which was represented by the Main Menderes Metamorphism (MMM) that occurred along the Alpine orogeny, it is believed that the gold mineralization in the study area resulted from the metamorphic fluid that formed due to the hydration and decarbonization of volcano-sedimentary rock. This fluid leached gold from the previously formed mafic rock, specifically the tremolite-actinolite schist (metagabbro) in the study area. The gold then migrated upwards along the N-S extensional shear (D3–D4). Hence, the evolution of gold-sulfide mineralization in the Şirindere area may be attributed to the regional metamorphism and deformation caused by the Alpine orogeny, which affected the pre-existing Pan-African basement units.

Keywords: EPMA data, geochemistry, gold-bearing quartz-carbonate veins, Menderes Massif, Şirindere(Aydın,Turkiye)