The mineralogy and geochemistry of the middle eoceneoligocene age germik formation evaporites in Karaköy (Hasankeyf/Batman)

Evaporite minerals (ie. gypsum and anhydrite) are minerals with high economic value, evaporite mineral beds are potential geological commodities that can be utilized in the construction business as building materials such as cement and plaster and in the agricultural practices, in organic agriculture as a yield enhancer and disinfectant. The discovery and the utilization of such deposits contributes to the economic growth of a country using local resources. In the proposed study, the purpose is the identification of the economically significant evaporate levels and establishing the mineralogical and geochemical characteristics of Middle Eocene-Oligocene/Late Germik formations found in the Batman region Hasankeyf district, South Eastern Province of Turkey. These mineral sediments that were defined as evaporite minerals in prior studies are known to be used by the local population for the restorations of historical artifacts and structures and it’s widely recognized as Roman mortar, Khorasan mortar or as 'Cas'. However no study was conducted on the geochemical and mineralogical properties of these mineral sediments. Methods used in this study can be classified in two groups as laboratory and field studies. The field studies were conducted on the evaporates in the vicinity of Karaköy village of Hasankeyf district (Batman) and the stratigraphic illustrations of the samples were done. The laboratory studies were conducted on the cross-sections of the samples to determine the petrographic properties, the mineralogical contents using XRD analysis and to determine the major-oxide, trace and rare earth element contents of the samples by ICP-MS analysis. Germik formations found in the studied field alternates between white, beige, gray, brownish, yellow and soft, diffuse layer, nodule and massif structured gypsum layers and occasionally dolomite containing limestone and clayish limestone. The alternation of the minerals starts from the base with dolomite and continues with gypsum as it get closer to the surface. In the X-Ray Diffraction – Whole Rock (XRD-TK) examinations of the rocks with fractured Germik formations (carbonated shale) and carbonate based (marn containing gypsum) and chemical based rocks (gypsum); phyllosilicate, dolomite, feldspar, quartz and calcite minerals were detected. According to the geochemical examinations, gypsum minerals, while having a significantly lower REE content comparative to the NASC, still shows some improvement comparative to chondrite. The lowest total REE concentration was obtained from the sample GF-2 (6.17 ppm) and the highest REE concentration was obtained from the sample GF-5 (10.33 ppm). In this study, the gypsum samples showed high contents of pure gypsum, which makes the samples also suitable for the manufacturing of trussed cement and blast furnace slag cement.