Investigon of some geoligical, mineralogical and geochemical properties of kiziltepe (Bolkardaği-Ulukişla-Niğde) gold-si̇lver-zi̇nc-lead deposit in the central taurus belt

The sulfide and non-sulfide Kızıltepe Au-Ag-Zn-Pb deposit, located in the Bolkar mountains, east of the Central Taurus Belt in Southern Turkey, was investigated in order to understand its formation mechanism as well as its geological, mineralogical and geochemical properties. The sulfide and non-sulfide ores in the deposit are located along the crack, fracture, fault, brecciated zone and in some places bedding planes of an overturned anticline within the Permo-Triassic low grade metamorphic platform type Bolkardağ carbonates. Primary sulfide ore residues, mainly composed of minerals such as pyrite, galena, sphalerite and fahlerz, and pyrites are occasionally transformed into marcasites, and pyrites are rarely accompanied by arsenopyrite minerals. Trace proportions of silver? minerals such as sulphate and covelline have been partially preserved in secondary and tertiary non-sulfide ores composed of Zn-Pb carbonates, Zn silicates and Fe-Mn oxy-hydroxides and in host rock crbonates. Much more dominant than primary sulfide ores, secondary and tertiary sulfide ores have either been displaced by surface weathering processes (autochthon) or redeposited in open tectonic lines and associated karstic spaces (allochthon). Mineralogical and petrographic studies were carried out with field observations as well as thin section optical and ore microscopes, XRD and SEM-EDS studies. Elemental scale point analyzes made during SEM-EDS studies and all rock major and trace element analyzes performed with ICP-MS and ICP-OES devices formed the basis of geochemical studies. Primary sulfide ores contain on average 32.08% Pb, 26.8% S, 20.41% Fe2O3, 15.22% Zn, 13.29% AK, 4.04% CaO and 1.84% SiO2. In statistical analysis, strong positive correlations between Fe-S, Al-K and Zn-Fe; Weak or very weak positive correlations between Zn-Ca, Mg-Ca, Pb-Ca, Al-Si and Mn-Fe, whereas strong negative correlations between Pb-AK and Pb-Fe; Weak or very weak negative correlations were also determined between Zn-Pb and Pb-Mg. Secondary-tertiary non-sulfide ores derived from primary sulfide ores contain an average of 30.81% Fe2O3, 11.73% AK, 11.27% MnO, 10.09% Pb, 5.06% Zn and 3.42% CaO. There are strong positive correlations between K-Al, S-Fe; weak positive correlations between Mg-Al, Pb-Fe, while strong negative correlations between S-Mn, S-P, and weak or very weak negative correlations between Mn-Fe, Fe-Si, P-Ca and Mn-Pb in the secondary-tertiary naon sulfide ores. Non-sulfide secondary-tertiary ores are enriched in Mn, Si, K, Al, Fe, C, and depleted in S, Mg, Pb, and P compared to sulfide primary ores. The contents of As, Cu, Sb, Cd and Sn, which are found at higher rates in primary sulfide ores than other trace elements, are 2518.2 ppm, 1181.9 ppm; 1107.6 ppm; 810.6 ppm and 730.4 ppm, respectively. Of these, high Cu, Sn and Cd values indicate a high-temperature formation, while As and Sb values indicate a low-temperature formation. As a result of multi-stage surface weathering and karstification processes, primary sulfide Zn-Pb ores were especially enriched in Au (1686.46 ppb) and Ag (>100ppm) and transformed into secondary non-sulfide Zn-(Pb) ores that yielded exploitable grades for Au and Ag as well as zinc and lead. Primary sulfide Zn-Pb ores have a total 8.66 ppm REE+Y; non-sulfide secondary Zn-(Pb) ores have a total REE+Y content of 18.16 ppm. Shale normalized primary sulfide ore samples exhibit similar flat or nearly flat REE patterns with weakly negative Ce (Average Ce/Ce*=0.79) and strongly positive Eu (Average Eu/Eu*=1.83) anomalies and chondritic Y/Ho ratios (Average 26). Non-sulfide secondary-tertiary ores have very similar REE+Y patterns with süper chondritic Y/Ho ratios (mean 39.7), distinct negative Ce (Ce/Ce*= Mean 0.77) and strongly positive Eu (Eu/Eu* = Avg. 10.17) anomalies. They show flat or nearly flat REE patterns. The most important difference between shale and primary and secondary-tertiary ores is that REE+Y contents are lower than Shale especially in primary ores and to a lesser extent in secondary-tertiary ores. The reason for this significant difference may be that the REE contents of the hydrothermal solutions associated with the lithospheric mantle-origin Horoz granodiorite, which is the main source of ore-forming solutions, are poorer than the hydrothermal solutions associated with a crustal magma. The geological, mineralogical, petrographic and geochemical data show that the Kızıltepe Au-Ag-Zn-Pb deposit has a three-stage formation model. The first stage is the intrusion of the lithospheric mantle-origin magma formed in the Bolkardağ region into the Permo-Triassic units and simulteneously emerged hydrothermal solutions in this process precipitating sulfide Zn-Pb ore veins, lenses and masses along the cracks, fractures, faults and brecciated zones in the Bolkardağ marbles. This process, which provides the formation of primary sulfidic Zn-Pb ores with hypogene epigenetic character, was resulted from the compressional tectonic regime causing a series of tectonic events such as subduction, collision and crustal thickening occurred simultaneously with the closure of the southern branch of the Neotethys oceanin Turkey, which started from the Late Cretaceous and became more active during the Late Paleocene-Early Eocene. The second phase is the transformation of primary sulfide Zn-Pb ores into earthy-crustic-renal-like secondary sulphur-free Zn-Pb ores consisting of Zn-Pb carbonate, -silicate and Fe-Mn oxy-hydroxides as a result of early surface weathering and karstification processes. The third stage is the transformation of both primary sulfide ore residues and secondary non-sulfur ores into Zn carbonate, Zn-silicate, Zn-hydrate and Fe-Mn oxy-hydroxide minerals to form tertiary sulfide-free Zn-Pb ores, with multi-stage late superficial weathering and internal karstification processes. and they are intertwined in the form of karst sediments in a very complex way together with the primary and secondary ores that have formed before.