Three minerals of the mayenite supergroup have been found in fluorellestadite-bearing metacarbonate rock (former fragment of petrified wood of ankeritic composition) from the dump at the Baturinskaya-Vostochnaya-1-2 mine. These are eltyubyuite Ca12Fe103+Si4O32Cl6, its fluorine analog Ca12Fe103+Si4O30F10, and chlormayenite–wadalite Ca12(Al,Fe)14O32Cl2–Ca12(Al,Fe)10Si4O32Cl2. The first two phases occur in the reaction mantle around hematite, magnesioferrite, and Ca-ferrite aggregates (“calciohexaferrite” CaFe12O19, “grandiferrite” CaFe4O7, and “dorrite phase” Ca2(Fe53+Mn0.53+Mg0.5)(Si0.5Fe5.53+)O20) and, rarely, as individuals in grained aggregates of fluorellestadite–cuspidine (± larnite ± rusinovite Ca10(Si2O7)3Cl2). Assemblages of zoned chlormayenite–wadalite crystals are found in grained aggregates of fluorellestadite– cuspidine, which lack Ca-ferrite. Also, harmunite CaFe2O4, chlorellestadite, fluorapatite, anhydrite, rondorfite Ca8Mg(SiO4)4Cl2, fluorine analog of rondorfite Ca8Mg(SiO4)4F2, “Mg-cuspidine” Ca3.5(Mg,Fe)0.5(Si2O7)F2, fluorite, barioferrite BaFe12O19, zhangpeishanite BaFCl, and other rare phases are identified in this rock. Data on the chemical composition and Raman spectroscopy of the mayenite-supergroup minerals are given. The genesis of metacarbonate rock is considered in detail: “oxidizing calcination” of Ca–Fe-carbonates with the formation of hematite and lime; reaction between hematite and lime with the formation of different Ca-ferrites; formation of larnite as a result of reaction between SiO2 and lime or CaCO3; and reactionary impact of hot Cl–F–S-bearing gases on early assemblages. Eltyubyuite and its fluorine analog crystallized at the stages of gas impact. It is presumed that the maximum temperature during the formation of rock reached 1200–1230 °C.

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