Gossan of the Yubileynoe massive sulfide deposit (South Urals): evidence for formation on the seafloor

Oxidation zone of the Yubileinoe massive sulfide deposit, South Urals, is buried beneath Jurassic sediments containing coalified plant remains. Mineralogy of gossan of this deposit is marked by the abundance of siderite. The carbon isotope composition (δ13C) in siderite varies from -20.0 to -23.4‰ PDB, which is close to δ13C variation in coals from the overlying sediments (-23.5 to -26.2‰ PDB). The formation of siderite is likely related to interaction between solutions of the Triassic oxidation zone and fermentation products of the organic matter.