Active Silica Diagenesis in the Deepest Hadal Trench Sediments

Luo, Min; Li, Weiding; Geilert, Sonja; Dale, Andrew W.; Song, Zijun; Chen, Duofu

doi:10.1029/2022gl099365

Cited by 16 publications

(4 citation statements)

References 52 publications

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“…Depth-integrated rates of AuSi precipitation at the SJ and SB sites are 0.40 mmol m −2 day −1 and 0.27 mmol m −2 day −1 , respectively. These rates are within the range previously derived for other delta (7.7 mmol m −2 day −1 ; Michalopoulos & Aller, 2004), marginal (0.1-5 mmol m −2 day −1 ; Ehlert et al, 2016;Ward et al, 2022a) and tectonically-active marine settings (0.07-21 mmol m −2 day −1 ; Geilert, Grasse, Doering, et al, 2020;Luo et al, 2022).…”

Section: Uncovering the Benthic Coupling Of Si And Fe Through Early D...supporting

confidence: 88%

Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads

Hendry

Hawkings

et al. 2023

Preprint

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Glacier meltwater supplies a significant amount of silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these essential nutrients reach the ocean is regulated by the processes occurring within fjords, which act as conduits from glacial rivers and subglacial discharge and the ocean. One key &#8211; but understudied &#8211; component of biogeochemistry within fjords is benthic cycling, especially in regions of rapid deposition of reactive particulates at fjord heads. Here, we explore the benthic cycling of Si and Fe at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including stable Si and Fe isotopes (&#948;30Si and &#948;56Fe respectively), and novel reaction-transport modelling for Si. A high diffusive flux of dissolved Fe from the fjord sediments compared to open ocean sediments is supported by both reductive and non-reductive dissolution of glacially-sourced reactive Fe phases, as reflected by the range of pore water stable Fe isotopes (&#948;56Fe from -2.7 to +0.8&#8240;). In contrast, the diffusive flux of dissolved Si from the fjord sediments is relatively low. High pore water &#948;30Si (up to +3.3&#8240;) observed near the Fe(II)-Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe but suppresses the release of dissolved Si at glaciated fjord heads. The redox sensitive coupling of Si and Fe has significant implications for our understanding of how essential nutrients are transport along fjord systems.

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Section: Uncovering the Benthic Coupling Of Si And Fe Through Early D...supporting

confidence: 88%

Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads

Hendry

Hawkings

et al. 2023

Preprint

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show abstract

“…Depth‐integrated rates of AuSi precipitation at the SJ and SB sites are 0.40 mmol m −2 day −1 and 0.27 mmol m −2 day −1 , respectively. These rates are within the range previously derived for other delta (7.7 mmol m −2 day −1 ; Michalopoulos & Aller, 2004 ), marginal (0.1–5 mmol m −2 day −1 ; Ehlert et al., 2016 ; Ward et al., 2022a ) and tectonically‐active marine settings (0.07–21 mmol m −2 day −1 ; Geilert, Grasse, Doering, et al., 2020 ; Geilert, Grasse, Wallmann, et al., 2020 ; Luo et al., 2022 ).…”

Section: Resultsmentioning

confidence: 99%

Benthic Dissolved Silicon and Iron Cycling at Glaciated Patagonian Fjord Heads

Hawkings

Bertrand

et al. 2022

Global Biogeochemical Cycles

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Glacier meltwater supplies silicon (Si) and iron (Fe) sourced from weathered bedrock to downstream ecosystems. However, the extent to which these nutrients reach the ocean is regulated by the nature of the benthic cycling of dissolved Si and Fe within fjord systems, given the rapid deposition of reactive particulate fractions at fjord heads. Here, we examine the benthic cycling of the two nutrients at four Patagonian fjord heads through geochemical analyses of sediment pore waters, including Si and Fe isotopes (δ30Si and δ56Fe), and reaction‐transport modeling for Si. A high diffusive flux of dissolved Fe from the fjord sediments (up to 0.02 mmol m−2 day−1) compared to open ocean sediments (typically <0.001 mmol m−2 day−1) is supported by both reductive and non‐reductive dissolution of glacially‐sourced reactive Fe phases, as reflected by the range of pore water δ56Fe (−2.7 to +0.8‰). In contrast, the diffusive flux of dissolved Si from the fjord sediments (0.02–0.05 mmol m−2 day−1) is relatively low (typical ocean values are >0.1 mmol m−2 day−1). High pore water δ30Si (up to +3.3‰) observed near the Fe(II)‐Fe(III) redox boundary is likely associated with the removal of dissolved Si by Fe(III) mineral phases, which, together with high sedimentation rates, contribute to the low diffusive flux of Si at the sampled sites. Our results suggest that early diagenesis promotes the release of dissolved Fe, yet suppresses the release of dissolved Si at glaciated fjord heads, which has significant implications for understanding the downstream transport of these nutrients along fjord systems.

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“…S1B). Some findings of reverse weathering along the shelf (5,42,43), the open ocean (44), and Hadal zone (45) were not quantified. Efflux of high δ 30 Si values to the water column via alteration of serpentine to an authigenic clay by seawater (10) and deep submarine groundwater inputs (46) point to additional sink and source terms, respectively, that were also not quantitatively considered in the 2021 summary (12).…”

Section: Discussionmentioning

confidence: 99%

Probing surface Earth reactive silica cycling using stable Si isotopes: Mass balance, fluxes, and deep time implications

Rahman,

Trower

2023

Sci. Adv.

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Geological reservoir δ 30 Si values have increasingly been applied as paleoclimate and paleoproductivity proxies. Many of these applications rely on the assumption that the surface Earth Si isotope budget is in mass balance with bulk silicate Earth, such that trends in δ 30 Si over time can be attributed to changes in flux to or from key silica reservoirs. We compiled δ 30 Si data from modern reservoirs representing the major sources and sinks of surface Earth reactive silica, to which we applied an inverse model to test assumptions about mass balance. We found that δ 30 Si values of reverse weathering products must closely match those of diatoms, conflicting with previous assumptions. Model results also revealed that of the 19 to 21 teramoles per year Si released during silicate mineral weathering, ~10 to 18 teramoles per year is stored in terrestrial silica sinks, consistent with assumptions of incongruent weathering reactions. Our results demonstrated that the modern silica cycle summary is in isotopic mass balance.

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Active Silica Diagenesis in the Deepest Hadal Trench Sediments

Cited by 16 publications

References 52 publications

Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads

Benthic dissolved silicon and iron cycling at glaciated Patagonian fjord heads

Benthic Dissolved Silicon and Iron Cycling at Glaciated Patagonian Fjord Heads

Probing surface Earth reactive silica cycling using stable Si isotopes: Mass balance, fluxes, and deep time implications

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