Geological, mineralogical and geochemical characteristics of the lead-zinc deposits located in the yahyali-zamanti river (Kayseri) region

Zinc (Zn), found in Group 12, Period 4 of the periodic table, and Lead (Pb), found in Group 14, Period 6, are both a metal group elements. Common characteristics of metals include their excellent conductivity of heat and electricity and their malleability. Thanks to these properties, Pb and Zn have become widely preferred non-ferrous metals in recent years across sectors such as lead-acid batteries, galvanization, radioactive shielding, and alloys. Despite their low boiling points and good malleability, Pb-Zn ores possess a highly complex ore mineralogy. Mining activities in the Yahyalı-Zamantı (Kayseri) belt, located in the southeast of the Central Anatolia region, date back to ancient times. However, the formation and origin of the ore deposits in the region remain a subject of debate due to a lack of comprehensive research in the fields of geology and metallogeny. The Yahyalı-Zamantı belt hosts numerous carbonate-hosted Pb-Zn deposits that have been subjected primarily to regional folding and thrusting. Despite this, the structural controls governing the location of these ore deposits in the area have not been sufficiently understood in previous studies. In this study, three Pb-Zn deposits (the Zengan, Erva, and Almila mines) in the Yahyalı-Zamantı region were examined in detail from a geological, metallogenic, and geochemical perspective. Inferences regarding ore genesis were made through field investigations, geological mapping, analysis of ore geometry, and detailed geochemical methodologies. To better interpret the main source of the ore metals in the deposits, the origin of the ore-forming fluids, and the mechanism of ore formation, various geochemical analyses were conducted on samples collected from different levels/elevations of the mines. These analyses included: XRF, ICP-MS, ore microscopy, XRD, fluid inclusion, δO, δC, δS, stable and Pb radiogenic isotopes, and EPMA. For all three deposits, Pb-Zn mineralization primarily occurs within sedimentary rocks along the NW-trending faults of the Aladağ Unity, presenting as dense massive, stockwork, stratiform, and disseminated forms. The stratiform vein/lenticular ore bodies are found in the carbonate and calcareous cover rocks of the Middle Devonian-aged Aladağ Unity. The primary ore minerals of the Zengan Pb-Zn deposit are pyrite, sphalerite, galena, and cerussite. The secondary ore minerals include smithsonite, goethite, hemimorphite, and hematite, while the gangue minerals are calcite, quartz, kaolinite, muscovite, barite, and montmorillonite. For the Erva Pb-Zn deposit, the primary ore minerals are sphalerite, galena, and cerussite. The secondary ore minerals are smithsonite, goethite, hemimorphite, hematite, and anglesite, with gangue minerals consisting of calcite, quartz, montmorillonite, dolomite, muscovite, halloysite, and kaolinite. Finally, the Almila Pb-Zn deposit's primary ore minerals are pyrite, sphalerite, galena, and cerussite. Its secondary ore minerals include smithsonite, goethite, hemimorphite, hematite, and anglesite, and the gangue minerals found are quartz, calcite, montmorillonite, dolomite, muscovite, halloysite, and kaolinite. The results from the δO, δC, δS, and Pb isotopic compositions indicate that the ore-forming fluids for these deposits are multi-sourced and formed as a result of the mixing of various ore-forming fluids. Stable isotope results: The δ13CV−PDB and δ18OV−SMOW stable isotope results for the Zengan, Erva, and Almila mines are as follows: Zengan: δ13CV−PDB: ‰-3.44 – +1.13, δ18OV−SMOW: ‰+18.04 – +26.16; Erva: δ13CV−PDB: ‰+1.47 – +2.19, δ18OV−SMOW: ‰+24.55 – +25.04; Almila: δ13CV−PDB: ‰-5.07 – -3.76, δ18OV−SMOW: ‰+27.04 – +29.05. These δ13CV−PDB and δ18OV−SMOW values suggest that the carbon in the ore-forming fluids primarily originates from the dissolution of marine carbonates of the Aladağ Unity, mixed with mantle-derived carbon. Pb isotope results: During the metallogenic stage, the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb isotopic compositions of the sulfide minerals vary within the following ranges: 18.6 – 18.7; 15.7 – 15.8; 38.8 – 39.1. The Pb isotopic compositions are relatively concentrated in the upper continental crust and orogenic belt. Sulfur isotope results: The δ34SV−CDT values of galena samples collected from the Zengan, Erva, and Almila mines are: Zengan: ‰6.06 – 6.45; Erva: ‰9.50 – 9.66; Almila: ‰10.58 – 11.30. All three mines show sulfur values falling within the magmatic-evaporite range. Furthermore, the δ34SV−CDT values indicate that the sulfur may have been derived from a mixture of hydrothermal fluids from local carbonate-evaporite sequences through thermochemical sulfate reduction (TSR). This suggests the ore-forming metals likely have a mixed source from the crust and orogenesis. The total amount of Rare Earth Elements (REE) is relatively low. The ∑REE, ∑HREE (Heavy Rare Earth Elements), ∑LREE (Light Rare Earth Elements), and ∑HREE/LREE values for the Zengan, Erva, and Almila areas were found within the following ranges, respectively: Zengan: ∑REE: 10.50 – 45.80, ∑HREE: 6.80 – 30.20, ∑LREE: 3.70 – 17.20, ∑HREE/LREE: 0.64 – 2.06; Erva: ∑REE: 10.8 – 18.80, ∑HREE: 8.20 – 14.6, ∑LREE: 2.60 – 4.20, ∑HREE/LREE: 3.15 – 3.47; Almila: ∑REE: 4.60 – 9.90, ∑HREE: 3.10 – 6.80, ∑LREE: 1.50 – 3.10, ∑HREE/LREE: 2.06 – 2.20. For all three areas, ∑HREE is relatively enriched, while ∑LREE is depleted. Conclusion on Deposit Genesis: When considered as a whole, the geochemical results lead to the conclusion that the Zengan, Erva, and Almila (Kayseri) Pb-Zn deposits are Carbonate Replacement Deposit (CRD) type Pb-Zn deposits. Their origin is linked to intrusion-related lead-zinc deposits controlled by regional tectonism within carbonate rocks. Ore formations are stratigraphically controlled within the Aladağ Unit and structurally controlled along the NW-trending normal fault system. Deep-seated hydrothermal fluids played an active role in the formation of all three deposits. An extensional tectonic environment was dominant during the ore formation processes.