Comparison of geological properties of Kaymaz (Eskişehir) and Himmetdede (Kayseri) gold deposits

Kaymaz (Eskişehir) Gold Mine (KGM) in Tavşanlı Zone and Himmetdede (Kayseri) Gold Mine (HGM) in Central Anatolian Massif are significant ore mineralizations operated economically. Gold mineralization is developed in Damdamca and Karakaya sites of KGM, within the contact of serpentinite and altered granite (main mineralization), while it is occurred in the metamorphic units in Kızılağıl Site and in the silicified serpentinites in the Mermerlik Site. Along with gold, there are also significant silver enrichments without gold content in the region. The types of alteration are silicification, argillization and rarely carbonation. There is also an intense iron oxide formation in the ore zone. The images showing the propagation of the clay minerals obtained in the remote sensing studies are in agreement with the propagation observed in the field, whereas the images showing SiO2 propagation do not overlap with the field. The serpentinite-granite contact forming the main ore zone is faulted. The major amount of the ore is formed within the serpentinite In the granite, a little amount of mineralization has occured near the contact. Hydrothermal solution engendering the mineralization has altered both of them. In the main ore zone and the Kızılağıl Site the gold content is concentrated in quartz rich sections. The gold grains in Mermerlik Site are observed in goethite ± lepidocrocite-rich sections. The opaque minerals found together with gold are chromite, Ni-sulphites, pyrite, arsenopyrite, galenite, native silver, acantite, iodargyrite and goethite ± lepidocrocite. According to chemical analyses, there is no significant correlation between gold and any element. In the fluid inclusion analyses, the homogenization temperatures measured in the quartz show variabilities according to the sites. Homogenization temperatures which indicate two different phases between 100-250 °C and 330-370 °C were measured in the main ore zone. Salinity values vary between 1.2-3.7%. In Kızılağıl Site, homogenization temperatures between 270-393 °C and salinity values ranging iv between 3.9-5.4% were measured. It is thought that these values are belonging to a different phase causing silver enrichment in the metamorphics. In HGM, the wall rock of the mineralization is gneiss interbanded with marble. The alterations observed in the site are argillization and silicification. There is intense goethite ± lepidocrocite formation in the site. HGM is divided into two zones as oxide zone at surface and sufide zone beneath the oxide zone, according to their ore minerals and alteration characteristics. The gold in the oxide zone are observed within the clay and cracks - joints. Most of the pyrite rarely encountered at this zone have replaced by goethite ± lepidocrocite. Gold grains detected in the sulphide zone are observed as inclusions in pyrite and between quartz crystals. Pyrite, arsenopyrite, enargite, galenite, cassiterite and rutile are other opaque minerals obtained in sulfidation zone. The homogenization temperatures measured in quartz which are gathered from these samples vary between 76-236 °C. Comparison of characteristics of these two mines showed that the mineralization in KGM is related to regional tectonism, while there is no relation between mineralization and tectonism in HGM. Fluid inclusion studies point to multiphase hydrothermal activity in the KGM whereas separate phases were not observed in the samples of the HGM. The comparison of alteration properties, mineral paragenesis and ore structure-texture relations of both sites showed that HGM's sulfide zone carries similarities with Carlin type deposits when the main mineralization of KGM is compatible with low sulfur epithermal systems. Similar to the supergene activities affecting Kızılağıl and Mermerlik sites of the KGM, it is thought that the mineralization developed in HGM's oxide zone is Gossan-type mineralization. Keywords: Kaymaz, Himmetdede, Turkey, Central Anatolia, gold, fluid inclusions, listvenite, low-sulfidation epithermal system, Carlin type, Gossan