An approach to geochemical characterization of productive versus barren granitoids in terms of iron in Central Turkey

Abstract

The granitoids associated with, and without skarn type mineralizations in central Anatolia are termed as productive and barren granitoids, respectively. The study of the relationships between plutonic rocks in the Central Anatolian Crystalline Complex in central Turkey suggests a direct genetic connection between the composition of plutons, and their associated ore deposits. In order to discriminate between productive and barren granitoids, two Fe-skarn granitoids (Celebi and Karamadazi), and a series of barren plutons within central Anatolia were examined. The Karamadazi and Celebi granitoids are geochemically different from other barren plutons in Central Anatolia. The parameters governing the productivity of these granitoids were determined by principal component analysis (factor analysis) method. Based on this method, the factors controlling the geochemical characteristics of the Celebi granitoids are (Al 2O 3+MgO+Fe 2O 3+P 2O 5+TiO 2+CaO)/(SiO 2), (K 2O+Rb)/(Na 2O) and Rb/Sr ratios, and for the Karamadazi granitoid the Fe 2O 3+MnO+MgO+P 2O 5+Y)/(SiO 2+Rb) (FMMY/S) and (Na 2O)/(K 2O) ratios. These two granitoids are clearly distinguished from the barren Central Anatolian Granitoids (CAG) on Harker diagrams based on these controlling factors (parameters). Barren CAG plutons are different from the productive Celebi granitoids in their higher silica content and generally higher total alkali values. This study suggests that iron-producing granitoids are less differentiated and receive little contribution from continental crust compared to the barren granitoids. Higher apatite and zircon abundance in the Celebi granitoids suggest that the Celebi granitoids have more I-type characteristics compared to barren plutons of CAG. The Karamadazi granitoid is the most striking example for the granitoids in CAG, having a higher contribution from the continental crust as evidenced by higher Rb, Ba, Th, the highest mean Sc, V, and mean Zr, Y, Ni contents. Based on the factor analysis, it is proposed that the Karamadazi granitoid displays geochemical characteristics similar to the Terlemez and Agacoren granitoids of CAG. The factor analyses indicated that the first two factors are about the same for both the Fe-producing Celebi and Karamadazi granitoids. Therefore, this similarity has let to a conclusion that the productivity or non-productivity of the granitoids in Central Anatolia can be tested by examining and comparing the distribution of granitoids in diagrams designed according to the factors defined in this study.