Carbon and oxygen isotope compositions of fibrous carbonate minerals were measured by an isotope ratio mass spectrometer. The results suggest that the fibrous Mg calcite from the Black Sea were formed by sulphide-driven anaerobic oxidation of methane under reducing conditions, which contributes to the understanding of the formation of Neoproterozoic fibrous dolomite.

Funding information:K. C. Wong Education Foundation: http://dx.doi.org/10.13039/501100012692DAAD: http://dx.doi.org/10.13039/501100001655Guangzhou Elite Project (No. JY201223)Open Access Publication Fund of Universität Hamburg: http://dx.doi.org/10.13039/501100005711Measurement name: Carbon and oxygen isotope compositionsInstrument: ThermoFisher Scientific 253plus gas isotope ratio mass spectrometer with Kiel IV automated carbonate preparation devicePlace: MARUM Stable Isotope Laboratory, BremenMeasurement:Samples were grinded into powder. About 1 mg powder from each sample was measured by the standard phosphoric acid method.