The paper demonstrates the hydrocarbon influence on ikaite (CaCO₃ ∙ 6H₂O) formation that is a calcium carbonate hexahydrate commonly found in sediments of polar and subpolar seas. The relevance of the study stems from the impact of hydrocarbon generation and oxidation on increasing dissolved inorganic carbon concentrations, thereby promoting the formation of authigenic carbonates. For this reason, carbonates are the principal authigenic minerals in gas seeps and mud volcanoes; they are also frequently encountered in wells drilled within oil and gas fields. Diagenetic degradation of Organic Matter in seafloor sediments within the sulfate reduction zone is considered the primary mechanism of ikaite crystallization, as this process causes the release of phosphate ions into pore waters, inhibiting the formation of anhydrous calcium carbonates. Another mechanism stabilizing ikaite is microbial methane generation below the sulfate reduction zone, which also contributes to increased phosphate ion concentrations. Anaerobic oxidation of methane does not release phosphate ions and therefore acts only as a secondary factor in ikaite formation, mainly by increasing total alkalinity. Theoretically, ikaite may also crystallize during the formation or dissociation of gas hydrates, which should result in anomalous oxygen and hydrogen isotope compositions (δ¹8O and δD).