Geological and metallogenic investigation of chromite mineralization in Adaören - Boyalıca (Dursunbey-Balıkesir) region

This study covers an area of approximately 74 km2 in the vicinity of Adaören Neighborhood and Boyalıca Neighborhood of Dursunbey district of Balıkesir province. The aim of this study is to investigate the geological, mineralogical, petrographic and geochemical characteristics of chromite mineralizations observed in ophiolites in the Western Anatolia region and to investigate the formation environments and economic dimensions of the mineralization. A total of 37 ore and wall rock samples were taken from the study areas, 27 of these samples were crushed and ground to 0.90 microns and below in the chrome laboratory in the study area and turned into powder for analysis. Whole rock major oxide and trace element analyses were performed on 7 chromite and wall rock samples taken from the study area around Boyalıca Neighborhood and 20 chromite and wall rock samples taken from the study area around Adaören Neighborhood, and geochemical and geostatistical evaluations were made. In addition, petrographic thin sections were made from wall rocks and bright/polishing sections were made from chromite ore samples, and microscopic examinations were examined in detail and SEM analysis was performed to obtain detailed data. According to chemical analysis of chromite samples, chromites contain 9.43-50.4 % Cr2O3. According to analysis results of samples belonging to chromite mineralization, ratio (Cr/Fe ratio) value is between 1.17 and 3.11 and its average is 2.09. Average Cr2O3 content of chromite samples is 25.80 %, average Al2O3 content is 2.59 %, average MgO content is 28.25 % and average TiO2 content is around 0.083 %. Evaluation was made on comparative diagrams of % Cr2O3 and main oxide % MgO, % Fe2O3 and % Al2O3 ratios in chromite samples. Accordingly, as Al2O3 and Fe2O3 ratios contained in chromite ore increase, Cr2O3 ratio also increases and as MgO ratio decreases, Cr2O3 ratio increases. Among the main oxide values in chromite samples, Cr2O3 shows positive correlation with Al2O3 and Fe2O3, while it shows negative correlation with MgO. According to the cluster analysis results created based on the correlation coefficients made in accordance with the chemical analysis data of the samples, 5 main groups were determined in chromite ore samples and 6 main groups were determined in wall rock samples. According to the analysis values of chromite ore samples, it was determined that Cr2O3 had a very strong positive correlation with V, a strong positive correlation with Fe2O3 and Zr, and a strong negative correlation with Ni. According to the analysis results of chromite ore samples, it was determined that there were samples with EF > 25 values in terms of MgO, SiO2 and Cr2O3, indicating high enrichment. In the principal component analysis (PCA) evaluation, it was determined that the main oxide and trace elements, namely Cr2O3, Fe2O3, Al2O3 and V, moved together, the main oxide and trace elements, namely TiO2, MnO, Gd and Zn, showed a positive correlation, and the main oxide and trace elements, namely Sr, Sn, Re, Dy, Tb, Eu, Hf, W, Zr, Cl, S, Co, Ga, Ni, CaO, SiO2 and MgO, came into the environment later. According to the SEM analysis, it was determined that the S content of the mineral observed in the polishing sample varied between 36.80-40.71 % and the Ni content varied between 44.97-61.95 %, and according to the results of the SEM analysis, it was concluded that the mineral found in the 2 chromite samples was millerite. According to the chemical analysis results of chromite samples, ophiolitic chromite and stratiform chromite boundary distinction was made in TiO2-Cr2O3 diagram and it was determined that all chromite minerals remained within the ophiolitic chromite boundaries. In the triangle diagram prepared according to Cr2O3, Al2O3 and Fe2O3 contents, it is seen that the analysis results are located in the ferrichrome boundary region. It was determined that chromite mineralizations in the study areas were formed in boninitic magma and behind the arc. According to the chemical analysis results of chromite samples, it was determined that 2 samples in the TiO2-Al2O3 diagram fell on the common part of the island arc and subduction zone peridotite boundaries and 8 samples fell on the island arc boundaries. According to the analysis results of the chromite mineralization samples taken from the study areas, it is shown that the region is a Podiform (Alpine) type chromite deposit. In the light of these data, it was concluded that the chromite mineralizations in the study areas were formed in boninitic magma and behind the arc, showed podiform type chrome deposit feature, were located in the ferrichrome border region according to the analysis results, and had a high ratio value, thus they could be used in the production of ferrochrome used in stainless steel, metal and weapon production in the metallurgical industry.