Lithological zoning and stable O and C isotopes distribution in carbonates in the Polish native sulfur deposits: Implications for origin of the ores

Abstract

The northern marginal part of the Polish Carpathian Foredeep hosts numerous native sulfur deposits associated with the Middle Miocene evaporite horizon. These deposits reveal lithological zoning, wherein both the barren and sulfur-bearing limestone zones are embedded within the gypsum basin area (zone). However, such zoning is incompatible with the bioepigenetic formation model of native sulfur deposits. Hence, their genesis remains enigmatic. Regional variations in stable oxygen and carbon isotope values of the limestones disclosed in the Osiek–Baranów Sandomierski native sulfur deposit are inconsistent with the molecular replacement of solid sulfate by calcium carbonate and native sulfur accumulations that expand from a fault zone into the gypsum basin. Instead, the distribution patterns of stable isotopes and sedimentological data suggest that a very shallow freshwater-dominated sedimentary–diagenetic environment developed in the hypersaline basin’s marginal zone, where the mixing of meteoric and highly saline water, as well as various bacterial processes, were responsible for lithological zoning and native sulfur distribution. The proposed results necessitate a reinterpretation of the epigenetic model of native sulfur ore formation.