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

Hu, Yu; Dong, Feng; Chen, Linying; Zheng, Guodong; Peckmann, Jörn; Chen, Duofu

doi:10.1016/j.marpetgeo.2015.05.001

Cited by 16 publications

(6 citation statements)

References 75 publications

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“…Goethite is usually considered to act as an ideal substrate for Fe-reducing bacteria in natural ecosystems due to its low crystallinity and high specific surface area [26,[60][61][62]. Moreover, siderite has frequently been found in association with calcite in seep environments [63][64][65]. In this study, the presence of siderite and rhodochrosite indicates that they were formed in an alkaline and non-sulfidic environment with sufficient supplies of Fe-oxides [66,67].…”

Section: Petrological and Geochemical Signatures For Fe/mn Reduction mentioning

confidence: 73%

Petrographical and Geochemical Signatures Linked to Fe/Mn Reduction in Subsurface Marine Sediments from the Hydrate-Bearing Area, Dongsha, the South China Sea

Xiao

Zhou

et al. 2019

Minerals

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Fe and Mn oxides and (oxy)-hydroxides are the most abundant solid-phase electron acceptors in marine sediments, and dissimilatory Fe/Mn reduction usually links with the anaerobic oxidation of methane (AOM) and organic matter oxidation (OMO) in sediments. In this study, we report the results from subsurface marine sediments in the Dongsha hydrate-bearing area in the South China Sea. The petrological and geochemical signatures show that the Fe/Mn reduction mediated by AOM and OMO might occur in sediments above the sulfate-methane transition zone. X-ray diffraction and scanning electron microscopy analyses of sediments indicate that Fe(III)/Mn(IV)-oxides and authigenic carbonate minerals coexisted in the Fe/Mn reduction zone. The lower δ13C values of dissolved inorganic carbon, coupled with an evident increase in total inorganic carbon contents and a decrease in Ca2+ and Mg2+ concentrations indicate the onset of AOM in this zone, and the greater variation of PO43− and NH4+ concentrations in pore water suggests the higher OMO rates in subsurface sediments. Geochemical and mineralogical analyses suggest that the previously buried Fe(III)/Mn(IV) oxides might be activated and lead to the onset of Fe/Mn reduction induced by AOM and OMO. These findings may extend our understanding of the biogeochemical processes involved in Fe/Mn reduction in continental shelves with abundant methane, organic matter, and terrigenous metal oxides.

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Section: Petrological and Geochemical Signatures For Fe/mn Reduction mentioning

confidence: 73%

Petrographical and Geochemical Signatures Linked to Fe/Mn Reduction in Subsurface Marine Sediments from the Hydrate-Bearing Area, Dongsha, the South China Sea

Xiao

Zhou

et al. 2019

Minerals

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“…Thus, our REE + Y data could ultimately be the result of the superposition of multiple signals, such as strong dissolution of Fe (oxyhydr)oxides, organic matter F I G U R E 6 Litho-and chemostratigraphic profiles of the Jaíba carbonates, including carbon and oxygen isotopes (δ 13 C, δ 18 O), chromium isotopes (δ 53 Cr), strontium isotopes ratios ( 87 Sr/ 86 Sr), elemental strontium contents, and Mn/Sr ratios oxidation in the iron reduction zone, freshwater-saltwater REE fractionation, and 1%-2% detritic contamination. Nevertheless, the two hypotheses early mentioned are efficient in promoting iron enrichment in sediments and when added to microbial metabolic activity in seafloor microbial mats, both may be complementary processes in terms of metal cycling, organic matter remineralization, and late calcite and other minerals precipitation; all these potentially affecting REE mobilization (Deng et al, 2017;Hu et al, 2015;Raiswell & Canfield, 2012;Smrzka et al, 2020;Smrzka et al, 2019). The MREE enrichment recognized in our samples follows it and is linked to organic matter degradation in the Fe reduction zone, early diagenetic apatite crystallization, and precipitation of secondary calcite (e.g., Deng et al, 2017;Smrzka et al, 2020).…”

Section: Strong Contamination Of Fementioning

confidence: 99%

Microbially induced chromium isotope fractionation and trace elements behavior in lower Cambrian microbialites from the Jaíba Member, Bambuí Basin, Brazil

et al. 2020

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In east‐central Brazil, the Ediacaran‐Cambrian Bambuí Basin has the potential to provide a record of unique geochemical responses of Earth's ocean and atmosphere evolution during this key time interval. From this perspective, we studied an interval of the upper Bambuí Basin using sedimentologic, stratigraphic, and chemostratigraphic tools. The lower Cambrian Jaíba Member of the uppermost Serra da Saudade Formation is an interval of up to 60 m‐thick of carbonate rocks disposed into two shallowing upward trends. Inner to outer ramp and high‐energy shoal deposits are described, in which laminated microbialites are the prevailing sedimentary facies. REE + Y data suggest contamination by iron (oxy)hydroxides that are dissociated from the riverine detritic flux. Sedimentary iron enrichment may be related to the settling of iron nanoparticles in coastal environments, diagenetic iron mobilization, or both. MREE enrichment is caused by microbial degradation of organic matter in the iron reduction zone during the anoxic early‐diagenetic stage. Chromium isotopes yielded negatively fractionated values (δ53Cr = −0.69 to −0.27‰), probably resulting from biotic and abiotic reduction of dissolved Cr(VI) to light and less toxic Cr(III) within pores of microbial mats. The δ53Cr data of the Jaíba microbialite are thus a product of metabolic reactions in microbial mats and do not reflect seawater signal. The isotopic offset from seawater is feasible from molecular diffusion of Cr into pore water and reduction reactions occurring deep inside the mat, although the exact mechanism and consequences are not yet fully understood due to the poor preservation of metabolic reactions in the geological record. Our study suggests that Cr isotopes can be used to reconstruct Cr and other metals cycling within ancient microbial mats, and that caution should be taken when using past microbialites to infer seawater Cr records and redox state of the atmosphere and ocean.

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“…Otherwise, the geochemical cycling of Fe is redox-active in near-surface marine sediments and methane-rich layers (Froelich et al, 1979;Raiswell and Canfield, 2012;Riedinger et al, 2014;Hu et al, 2015a;Nevin and Lovley, 2002). Under normal reducing conditions, Fe exists mainly in divalent cationic form and forms sulfide or sometimes siderite.…”

Section: Introductionmentioning

confidence: 99%

“…In such environments, the release of hydrogen sulfide and bicarbonate through AOM leads to the reduction of Fe-oxyhydroxides and the precipitation of Fe sulfides (Hensen et al, 2003;März et al, 2008;Yang et al, 2018). Based on this, Fe speciation could be regarded as a tool to assess variable redox conditions during seepage history (Hu et al, 2015a). In addition, Fe speciation also contributes to the interpretation of fluctuations of redox-sensitive elements in the seepage-impact environment under various redox conditions.…”

Section: Introductionmentioning

confidence: 99%

Geochemical implications for gas hydrate occurrence and seepage at Sites GMGS5-W07 and W09 in Qiongdongnan Basin, South China Sea

Yang

et al. 2022

Front. Earth Sci.

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The compositions and morphological characteristics of minerals and the cycle of trace elements in sedimentary environments are considered to be powerful indicators for the occurrence and evolution of gas hydrates. In this article, total organic carbon (TOC) content, particle size distribution, mineral composition, element distribution, and iron speciation of sediments from sites GMGS5-W07 and GMGS5-W09 of the South China Sea are studied. The high content of TOC and the occurrence of authigenic mineral assemblages suggest the accumulation potential of gas hydrate at the two sites. In the methane-rich layers, redox-sensitive trace elements, such as Co, Ni, Cu, Zn, As, Sb, Fe, and Mn, are enriched while reducing conditions lead to the accumulation of Fe and the increase of Fe(II) species proportion in sediments. Enrichment factors and Pearson correlation analysis of trace elements show that the circulation of trace elements at site W07 is more strongly affected by methane-rich fluids than at site W09. Fe-oxyhydroxides play a critical role in the development of As and Sb enrichments, and in particular, seep fluids may be a pivotal extra input of Mo, As, and Sb at site W07. Therefore, more intense methane seepage might have happened at site W07, and this conjecture has been further confirmed by higher Sr/Ca in sediments. Based on these results, the change in seepage intensity is not associated with the occurrence of gas hydrate.

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

Cited by 16 publications

References 75 publications

Petrographical and Geochemical Signatures Linked to Fe/Mn Reduction in Subsurface Marine Sediments from the Hydrate-Bearing Area, Dongsha, the South China Sea

Petrographical and Geochemical Signatures Linked to Fe/Mn Reduction in Subsurface Marine Sediments from the Hydrate-Bearing Area, Dongsha, the South China Sea

Microbially induced chromium isotope fractionation and trace elements behavior in lower Cambrian microbialites from the Jaíba Member, Bambuí Basin, Brazil

Geochemical implications for gas hydrate occurrence and seepage at Sites GMGS5-W07 and W09 in Qiongdongnan Basin, South China Sea

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