DOI: 10.1016/j.epsl.2020.116288
论文题名: Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin
作者: Luo M. ; Torres M.E. ; Hong W.-L. ; Pape T. ; Fronzek J. ; Kutterolf S. ; Mountjoy J.J. ; Orpin A. ; Henkel S. ; Huhn K. ; Chen D. ; Kasten S.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 541 语种: 英语
中文关键词: deep biosphere
; diagenesis
; Fe-AOM
; Hikurangi margin
; volcanic ash
英文关键词: Carbon
; Isotopes
; Methane
; Oxidation
; Positive ions
; Sediments
; Sulfur compounds
; Underwater mineral resources
; Volcanoes
; Anaerobic oxidation of methanes
; Isotopic composition
; Mass balance considerations
; Maximum concentrations
; Numerical modeling approach
; Seafloor drilling
; Sequential extraction
; Sulfate-methane transitions
; Iron compounds
; carbon cycle
; chemical alteration
; concentration (composition)
; iron
; marine sediment
; methane
; porewater
; volcanic ash
; Hikurangi Margin
; Pacific Ocean
英文摘要: We present geochemical data collected from volcanic ash-bearing sediments on the upper slope of the northern Hikurangi margin during the RV SONNE SO247 expedition in 2016. Gravity coring and seafloor drilling with the MARUM-MeBo200 allowed for collection of sediments down to 105 meters below seafloor (mbsf). Release of dissolved Sr2+ with isotopic composition enriched in 86Sr (87Sr/86Sr minimum = 0.708461 at 83.5 mbsf) is indicative of ash alteration. This reaction releases other cations in the 30-70 mbsf depth interval as reflected by maxima in pore-water Ca2+ and Ba2+ concentrations. In addition, we posit that Fe(III) in volcanogenic glass serves as an electron acceptor for methane oxidation, a reaction that releases Fe2+ measured in the pore fluids to a maximum concentration of 184 μM. Several lines of evidence support our proposed coupling of ash alteration with Fe-mediated anaerobic oxidation of methane (Fe-AOM) beneath the sulfate-methane transition (SMT), which lies at ∼7 mbsf at this site. In the ∼30-70 mbsf interval, we observe a concurrent increase in Fe2+ and a depletion of CH4 with a well-defined decrease in δ13C-CH4 values indicative of microbial fractionation of carbon. The negative excursions in δ13C values of both DIC and CH4 are similar to that observed by sulfate-driven AOM at low SO4 2− concentrations, and can only be explained by the microbially-mediated carbon isotope equilibration between CH4 and DIC. Mass balance considerations reveal that the iron cycled through the coupled ash alteration and AOM reactions is consumed as authigenic Fe-bearing minerals. This iron sink term derived from the mass balance is consistent with the amount of iron present as carbonate minerals, as estimated from sequential extraction analyses. Using a numerical modeling approach we estimate the rate of Fe-AOM to be on the order of 0.4 μmol cm−2 yr−1, which accounts for ∼12% of total CH4 removal in the sediments. Although not without uncertainties, the results presented reveal that Fe-AOM in ash-bearing sediments is significantly lower than the sulfate-driven CH4 consumption, which at this site is 3.0 μmol cm−2 yr−1. We highlight that Fe(III) in ash can potentially serve as an electron acceptor for methane oxidation in sulfate-depleted settings. This is relevant to our understanding of C-Fe cycling in the methanic zone that typically underlies the SMT and could be important in supporting the deep biosphere. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165143
Appears in Collections: 气候变化与战略
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作者单位: Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, 201306, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266061, China; College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, OR 97331, United States; Geological Survey of Norway, Trondheim (NGU), Norway; MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany; Faculty of Geosciences, University of Bremen, Bremen, Germany; GEOMAR Helmholtz Centre for Ocean Research, Kiel, 24148, Germany; National Institute of Water and Atmospheric Research, Wellington, New Zealand; Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
Recommended Citation:
Luo M.,Torres M.E.,Hong W.-L.,et al. Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin[J]. Earth and Planetary Science Letters,2020-01-01,541