Özet:

In this study, the mineralogical, petrographic and geochemical features of the Eskigedik-Kızılçayır chromite ores were revealed and the locations of the chromite masses in the depths were tried to be determined by the Ground Penetrating Radar (GPR) method. There are ophiolitic rocks of the upper Cretaceous age in the area where the chromite open pits is located. The wall rock which is bearing the chromite deposites are substantially altered harzburgite and dunite. The chromite masses are within the completely serpentinized dunites and are in the form of small lenses and pods. The texture of the ore is mainly massive, sometimes scattered and nodular. The gangue minerals are rod-shaped serpentines. The size of the chromite grains is quite variable (2-30 mm), very fractured and mylonitized and the fractures are filled with serpentine. The geochemistry of the chromites and its host rocks are similar to the low-grade podiform chromite deposits in located at Turkey. The average Cr2O3, Al2O3 and Fe2O3 contents are 16%, 14% and 12%, respectively, and are high-aluminum chromites. It is mostly enriched with trace elements such as Co, Ni and V. The geochemical evidences suggest that these chromites are derived from a mantle source modified by subduction in the oceanic arc basin. In order to determine unexposed ore in the open field, GPR measurements were made with 100 MHz antenna along 83 lines on slope and open pit flatness. Measurements in the first excavation area of the open pit were carried out without any problems, but the wetness of the second excavation area limited GPR operations. Underground sections were obtained by applying data processing techniques to the raw data obtained from the measurements. Because of the physical properties of the chrome ore, the areas with higher reflectance than the wall rocks were accepted as chromite areas because of the significant geophysical indications. In slope steps in the open pit area, high reflection surfaces were observed along several lines and at different depths. On the other hand, the presence of highly reflective surfaces at depths of about 10m in the lower and upper flats in the open pit was identified along the many lines. In the lower flat of the open pit, it is firstly necessary to confirm by excavation whether chromite is present at the high reflectivity surface determined at a depth of 10-20m along the second parallel line. Once the chromite presence has been identified, the excavations firstly must be done in this area and in the upper flat of the open pit.

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