Cihanpaşa (Yozgat) bölgesinin güney kesimindeki manganez cevherleşmesinin jeokimyasal özellikleri ve kökeni

Abstract

Late Cretaceous ophiolitic mélange complexes of the Izmir-Ankara-Erzincan Suture Zone (İAESZ) that is the remnant of the northern branch of the Neotethys Ocean host numerous manganese oxide deposits in Turkey. These deposits are observed within the red-violet radiolarian chert blocks belonging to mélange units. Of these mélange units, the Artova mélange is observed along the İAESZ in the northern part of the Kırşehir Massif, central Turkey, and is made up mainly of pelagic limestone, pillow basalt, radiolarian-chert blocks, and highly altered serpentinite. Mn-oxide mineralizations from Cihanpaşa (Yozgat, central Anatolia) region were analysed in order to determine their depositional conditions, paleo-redox signatures, origin and source. These mineralizations are composed mainly of an alternation of radiolarian cherts and mudstones that overlie altered pillow basalt in an overturned fold. Based on petrographic studies, the mineral paragenesis of the manganese oxide mineralizations is comprised predominantly of braunite, pyrolusite, pysilomelane and quartz. Geochemically, high Mn/Fe (60.2), low ΣREE (15.75 ppm) and Cu+Ni+Co (730 ppm), and a negative Ce anomaly and weakly negative Y/Y* anomaly (0.87) suggest that the Cihanpaşa manganese mineralizations formed in a submarine hydrothermal system. A negative Ce/Ce* anomaly (0.33), low Ceanom values (< − 0.54), and redox-sensitive tracers [V/(V + Ni) = 0.43, Ni/Co = 0.51, V/Mo = 6.15)] indicate that the manganese mineralization was formed by a hydrothermal system in an oxygenated marine sedimentary environment. Further, a weakly positive and negative Eu anomaly (0.84), high Lasn/Cesn (3.96), low Al/(Al + Fe) (0.34) and ΣREE/Fe (30.7x10-4) ratios highlighted that the Cihanpaşa manganese mineralizations were formed via impact of a low-T hydrothermal system, which is relatively close to the spreading ridge of the Izmir-Ankara-Erzincan Ocean.