Mineralogy, ore genesis and zircon U[sbnd]Pb age characteristics of the Cerattepe Cu[sbnd]Au (±Zn) deposit (Artvin, NE Turkey)

Abstract

The Cerattepe deposit is associated with bimodal felsic volcanics of the Kızılkaya Formation, which hosts the majority of VMS deposits in the Eastern Pontide Orogenic Belt. Pyrite, chalcopyrite, sphalerite, and bornite are the main sulfides, with minor galena, fahlores, marcasite, idaite, covellite, and chalcocite. Barite and quartz are the primary gangue minerals, with minor calcite and gypsum. Hematite, limonite, goethite, jarosite, and lepidocrocite are common oxide minerals. The sulfide ore is shaped by rapid cooling, zone refinement, replacement, and local deformation processes, which affect textural relationships and mineral paragenesis. Fluid inclusion studies have shown that the early stages of the ore were formed by boiling at temperatures of 250–355 °C and approximately 1900 m depth of sea water, while the later stages developed at temperatures as low as 148 °C. The Te temperatures imply that NaCl-dominated solutions with partial mixing of CaCl2 may be responsible for mineralization. The CO2 phase present in the early stages of the ore may have been derived from the interaction of hydrothermal solutions with the underlying carbonate rocks. Salinity values of 0.2–7.62 wt% NaCl equ., compatible with the average salinity of Kuroko type VMS deposits, indicate that the Cerattepe deposit was formed in a marine environment. The Co/Ni of pyrites (1–12, with an average of ∽2) and Zn/Cd of sphalerites (127–383) indicate an acidic source and magmatic source of acidic-andesitic for the ore-forming fluids, respectively. The δ34S values −4.4 ‰ – +9.63 ‰ indicate a magmatic sulfur source, with partial sulfate-reduced sulfur. A magmatic-related source is also inferred from δ18O values (+8.5 and + 9.5 ‰.) for the Cerattepe deposit. The leaching, zone refinement, and replacement processes, followed by remobilization and precipitation of the metals, resulted in gold enrichment in the oxide zone. The new zircon U[sbnd]Pb dating constrains the formation age of the Cerattepe deposit into a time span from 79 ± 1–76.8 ± 1 Ma, a younger age compared to other VMS deposits in the eastern Pontide region.