Morphology and formation mechanism of pyrite induced by the anaerobic oxidation of methane from the continental slope of the NE South China Sea

Enhanced framboidal pyrite formation related to anaerobic oxidation of methane in the sulfate-methane transition zone of the northern South China Sea

“…(D, E) Framboidal pyrite with secondary overgrowths. In D and E, the inner core consists of densely packed spherulitic pyrite microcrystals of a uniform submicron size, surrounded by a secondary crust of elongated marcasite (FeS 2 ) microcrystals (also seen in Zhang-M et al, 2014). (F) Spherical framboids with outer crusts consisting of secondary pyrite microcrystals.…”

“…This is an uncommon phenomenon in both modern and ancient sediments. Althoug framboid clusters have been reported in both older (e.g., Kalliokoski et al, 1974, and references therein) and recent studies (e.g., Mazumdar et al, 2011;Zhang-M et al, 2014;Shao et al, 2015;Egawa et al, 2015), no investigation to date has discussed their nature and mode of formation. In the study units, framboid clusters show a range of diameters, from several hundreds to a few thousands of microns (Fig.…”

Diagenetic disturbances of marine sedimentary records from methane‐influenced environments in the Fram Strait as indications of variation in seep intensity during the last 35 000 years

“…Canfield & Berner (1987) observed that in anoxic sediments with high content of organic carbon the hydrogen sulphide produced during organoclastic sulphate reduction caused the dissolution of magnetite and formation of pyrite, which is a paramagnetic mineral giving magnetic susceptibility values of near-zero. Iron oxides after dissolution by hydrogen sulphide recombine to reduced forms of iron sulphides such as greigite and mackinawite that readily convert to the stable pyrite (Dewangan et al 2013;Zhang et al 2014). Given the low accumulation rates of organic matter in the Atlantic zone over the western Svalbard margin (M€ uller & Stein 2014;Sanchez-Vidal et al 2015), the presence of hydrogen sulphide is most probably an indicator of ongoing AOM.…”

Using iron speciation in authigenic carbonates from hydrocarbon seeps to trace variable redox conditions

“…pyrite, siderite, ankerite) are among the diagenetic products of this process, and are frequently observed in association with the predominant calcium carbonate minerals at seeps (e.g. Chen et al, 2006;Dewangan et al, 2013;Gonz alez et al, 2012;Peckmann et al, 2001;Sun et al, 2015;Zhang et al, 2014). Numerous seafloor observations revealed significant variability of chemical and physical parameters and associated early diagenetic conditions within shallow subsurface sediments at seeps (e.g.…”

“…Lyons and Severmann, 2006;Owens et al, 2012;Raiswell and Canfield, 2012;Severmann et al, 2010;Scholz et al, 2014a,b), Fe is a potential redox proxy that allows constraining the formation conditions of marine sediments and sedimentary rocks. Studies on Fe in sediments at seeps and in authigenic seep deposits mainly focused on the geochemical cycling of Fe and the involved biogeochemical processes Beal et al, 2009;Gonz alez et al, 2012;Lemaitre et al, 2014;Pierre et al, 2014;Riedinger et al, 2014;Sivan et al, 2014;Sun et al, 2015;Zhang et al, 2014). In particular, Fe oxides can stimulate sulfate-driven AOM at seeps (Beal et al, 2009;Sivan et al, 2014).…”