The mineralogy, petrography and geochemistry of Kesikköprü Fe-oxide deposit, Bala-Ankara

Kesikköprü iron-oxide deposit occured at the contact between rocks that crystalline limestone (locally dolomitic), mafic-ultramafic rocks composed of diorite, gabbro and pyroxenite, and granitoids consists of granite, granodiorite, monzonite and their porphyry. In this respect, the iron-oxide mineralization in the study area is controlled dominantly by lithological features rather than structural control. It is defined as partially magnesian and dominantly calcic skarn based on alteration mineralogy. Skarn in the study area is defined in two groups. The first is small and limited endoskarn formation, The second group is more widespread exoskarn formation. In general, endoskarn is characterized by garnet-pyroxene, while exoskarn zones are defined as garnet ± pyroxene, pyroxene ± garnet, epidote-garnet and epidote from granitoids to recrystallized limestone and mafic-ultramafic rocks. In Kesikköprü, epidote-garnet and epidote rich zones within exoskarns are important for magnetite mineralization. Geochemical results of Kesikköprü granitoid which is considered to be responsible for mineralization in this study indicate that all the granitoid samples in open pit area are subalkaline and calc-alkaline and shoshonitic in character. According to Al-saturation index, metalumina-partly peralumina in character and they are classified as I-type granitoid. Trace element patterns normalized to MORB show enrichment in Sr, K, Rb, Ba, Th, Ta, Nb, Ce, and, P an Zr in part, while depletion in Ti and Y. In tectonic classification diagrams, granitoids plot on intersection of syn-COLG, VAG and WPG field, indicating post-collision character for Kesikköprü granitoid. Compared with granitoids related to Fe-skarns, Kesikköprü granitoid has similar geochemical signature to Çelebi, Karamadazı and Murmano granitoids in CACC (Central Anatolian Crystalline Complex) and granitoid related to Fe-, Cu- ve Pb-Zn-skarns. The results obtained from this study indicate that Kesikköprü mineralization is a skarn type deposit with respect to alteration mineralogy and time-space relationship of mineralization. In addition to this, IOCG (Iron Oxide Copper Gold) potential of Kesikköprü mineralization should not be ignored as most of IOCG systems contain small scale skarn type mineralization.