Abstract: Seabed methane seepage is common in areas with gas hydrate potential.Methane anaerobic oxidation and sulfate reduction occurring in these areas not only control the leakage of methane, but also facilitate the formation of authigenic minerals, which presenting itself as the enrichment of iron-bearing authigenic minerals in sediments rich in iron.This paper discussed the effect of sulfate reduction on the formation of iron-bearing authigenic minerals in a marine methane seepage environment through lab tests of methane-water-rock-bacteria reactions in a low-temperature and high-pressure reactor that simulated seabed sediment environment.The results showed decrease of pH, ORP and increase of HS^- and HCO₃^- concentration, indicating sulfate reduction and anaerobic oxidation of methane in the reactor.The total iron content in the solution decreased by about 7.5 mg/L before and after the tests, indicating iron-related precipitation.SEM images also showed precipitation of mostly iron sulfide with some ankerite and siderite.The paper suggested that a close relationship exist between the formation of authigentic minerals and microbial effect and that the interaction between sulfate reduction and anaerobic oxidation of methane play a positive role in the formation of iron-bearing authigenic minerals.This study may help in understanding further the forming mechanism of iron-bearing authigenic minerals in methane-seepage areas and its significance for gas hydrate prospecting.

Key words: methane seepage environment, reactor test, sulfate reduction, iron-bearing mineral, gas hydrate