Statistical evaluation of the geochemical data from Akoluk epithermal gold area (Ulubey–Ordu), NE Turkey

Abstract

The Akoluk gold mineralization area is located in the southern section of the western Pontide tectonic belt in the northeast of Turkey. The area of interest is intensely vegetated with hazelnut trees grown on a grass covered land. Rock exposures are quite limited, mainly encountered in small valleys. Therefore, soil geochemistry is the only useful tool in delineating the areas of gold mineralization. For this purpose, 375 soil samples were collected from the B-horizon of soil profile which is widely available in the area for a representative sampling. A vein type gold occurrence is confined to the fault zones crossing dacitic tuffs of Upper Cretaceous age. Faults are a conjugate set of a shear system, striking N 45–50 E, and N 55–60 W dipping 80–85 SE and 70–80 NW, respectively. Gold mineralization occurs generally as replacement of dacitic tuffs along the fault planes and less of void fillings. The main ore minerals are electrum, stibnite, zinkenite, pyrite, marcasite, realgar, orpiment, sphalerite, galena, chalcopyrite, malachite, and azurite, and the most common gangue minerals are barite and quartz. The soil is residual and well developed with a thickness ranging from 0.5 m to 1 m. The soil type in the study area is brown podzolic. A total of 375 soil samples were collected on 25 m intervals along N25W trending lines and 50 m apart throughout this study. Elements analyzed and interpreted are the ones which are known to have close association with gold. Ag, Sb, As, Mo, W, and Ba show a single very significant anomaly pattern. Several other small isolated anomalies are also observed due to sampling artifacts. The significant anomaly is circular in shape and has a diameter of approximately 200 m. The anomaly does not reflect the fracture system. This may be due to the fact that the sampling interval is wider than the fault zones. Cluster and factor analyses reveal that Zn, Mo, and W form a different suite which is not related to the same mineralizing system as gold. These elements form the deeper section of the mineralization which is partly exposed in the area. Since their anomalous patterns are coinciding with that of gold, the former appears to be the case.