Rates of carbonate cementation associated with sulphate reduction in DSDP/ODP sediments: implications for the formation of concretions

Abstract

Abstractduring sulphate depletion over these depth ranges are equivalent to a dispersed phase of approximately 1.5 wt.% CaCO 3 or 3 wt.% dolomite in a compacted sediment. The complete occlusion of sediment porosity observed in concretions with isotopic signatures suggesting carbonate sourced from sulphate reduction therefore requires more time (a depositional hiatus), 1 more rapid sulphate reduction (possibly by anaerobic methane oxidation) and/or the continued transport of isotopically light carbonate to the concretion site after sulphate reduction has ceased.

Organic carbon remineralisation and complex, early diagenetic solid–aqueous solution–gas interactions: Case study ODP Leg 204, Site 1246 (Hydrate Ridge)

“…Saturation 4 indices (SI; SI = log(IAP/K) with IAP the ion activity product and K the equilibrium constant) 5 with respect to the mineral phases of interest are initially set to 0 except for calcite. A 6 supersaturation with respect to calcite (SI=0.85) is assumed due to phosphate adsorption onto 7 calcium carbonate, in accordance with observations by Raiswell and Fisher (2004). 8…”

Microbially-driven formation of Cenozoic siderite and calcite concretions from eastern Austria

“…In contrast, hydrogenotrophic methanogenic archaea are highly selective in terms of their carbon source and preferentially take up 12 CO 2 , which results in a residual dissolved carbonate pool that is strongly enriched in 13 C (δ 13 C values of +24‰; Boehme et al, 1996). Carbonate minerals precipitated in the zone of methanogenesis have therefore positive δ 13 C values, again depending on the extent of mixing of different carbon sources (Irwin et al, 1977;Siegel et al, 1987;Kiriakoulakis et al, 2000;Lash and Blood, 2004;Raiswell and Fisher, 2004;Pearson and Nelson, 2005;Ziegenbalg et al, 2010;Hoffmann-Sell et al, 2011;Meister et al, 2011;Kuechler et al, 2012;Natalicchio et al, 2012;Birgel et al, 2015).…”

“…Nevertheless, the δ 13 C values of the carbonate carbon are commonly higher than those of the parent organic matter, because marine dissolved inorganic carbon with its δ 13 C value of around 0‰ is admixed during the precipitation process (Irwin et al, 1977;Coleman et al, 1985;Peckmann and Thiel, 2004). Consequently, the δ 13 C values of diagenetic carbonate precipitated in the zones of iron reduction and sulfate reduction commonly fall between -30‰ and 0‰, depending on the mixing of the two or more carbon sources (Irwin et al, 1977;Coleman et al, 1985;1993;Peckmann et al, 1999;Raiswell and Fisher, 2004;Loyd et al, 2012a;2012b). In contrast, hydrogenotrophic methanogenic archaea are highly selective in terms of their carbon source and preferentially take up 12 CO 2 , which results in a residual dissolved carbonate pool that is strongly enriched in 13 C (δ 13 C values of +24‰; Boehme et al, 1996).…”

“…If bacterial oxidation of organic matter or hydrogenotrophic methanogenesis were involved in the precipitation of carbonate, this is commonly reflected in the stable carbon isotopic composition of the resultant carbonate minerals (Irwin et al, 1977;Coleman et al, 1985;Siegel et al, 1987;Raiswell and Fisher, 2004). Iron-and sulfate-reducing bacteria most commonly assimilate carbon heterotrophically in marine sedimentary environments.…”

“…They form during shallow burial of sediments, preferably within the first tens of meters when the surrounding sediment is still unconsolidated, and are, thus, products of early diagenesis (Blome and Albert, 1985;Pye et al, 1990;Mozley, 1996;Raiswell and Fisher, 2004). Sellés-Martí-nez (1996) provided an elaborate classification scheme of various concretionary bodies, distinguishing between cements, veins, nodules, and concretions.…”