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Surface characteristics, mineralogy and geochemistry of the gicik low–sulfidation epithermal au deposit (Ankara province, central anatolia)

Çil, Akın
Tethyan-Eurasian Metallogenic Belt was formed as a result of the Mesozoic-Cenozoic Alpine-Himalayan orogeny related to the opening and closure of the Tethyan ocean basins. Turkey forms a sector of this extensive belt, and hosts numerous precious and base metal deposits. Gicik Au mineralization is located at Sakarya zone and approximately 15 km north of Ankara. Gold mineralization is hosted within Middle Eocene (ca. 44 Ma) intermediate composition dacitic lavas and agglomerates that are widely exposed near Ankara, and unconformably overlying the Paleozoic metamorphic basement. Whole-rock geochemical analyses of volcanic rocks indicate that the volcanism is metaluminous, medium-K calc-alkaline in composition and related to subduction and post-collisional tectonic setting. Lithogeochemical and geochronological data strongly implies that the studied volcanic rocks belong to the earlier (Eocene) eruptive volcanic event at the north of Ankara which was followed by volcanic rocks of Galatean Volcanic Province (Miocene). These volcanic lithologies are cut by NNE–trending 2 to 10 meters thick siliceous veins that display stockwork, colloform banding and superimposed breccia textures or less commonly bladed textures. Main ore minerals in the Gicik area includes argentiferous tetrahedrite, pyrite and arsenopyrite. Alteration assemblages include widespread epidote-chlorite with less common calcite (propylitic), argillic (kaolinitesericite/illite-smectite-quartz-adularia) and silicification. 40Ar/39Ar age data obtained from sericite in Gicik deposit yielded age of 45 – 47 Ma suggesting synchronous formation of volcanism and mineralized system. Central Anatolia is remained relatively underexplored when compared to the eastern and western parts of the Eocene magmatic belt across the north of İzmir-Ankara-Erzincan suture. Presence of Eocene volcanism related Gicik mineralization in central Anatolia puts entire magmatic belt in a position potential to especially precious metal mineralization.