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Serpentine alteration as source of high dissolved silicon and elevated δ 30 5 Si 6 values to the marine Si cycle

Geilert, S.; Grasse, P.; Wallman, K.; Liebetrau, V.; Menzies, C.D.

Serpentine alteration as source of high dissolved silicon and elevated δ 30 5 Si 6 values to the marine Si cycle Thumbnail


Authors

S. Geilert

P. Grasse

K. Wallman

V. Liebetrau



Abstract

Serpentine alteration is recognized as an important process for element cycling, however, related silicon fluxes are unknown. Pore fluids from serpentinite seamounts sampled in the Mariana forearc region during IODP Expedition 366 were investigated for their Si, B, and Sr isotope signatures (δ30Si, δ11B, and 87Sr/86Sr, respectively) to study serpentinization in the mantle wedge and shallow serpentine alteration to authigenic clays by seawater. While serpentinization in the mantle wedge caused no significant Si isotope fractionation, implying closed system conditions, serpentine alteration by seawater led to the formation of authigenic phyllosilicates, causing the highest natural fluid δ30Si values measured to date (up to +5.2 ± 0.2‰). Here we show that seafloor alteration of serpentinites is a source of Si to the ocean with extremely high fluid δ30Si values, which can explain anomalies in the marine Si budget like in the Cascadia Basin and which has to be considered in future investigations of the global marine Si cycle.

Citation

Geilert, S., Grasse, P., Wallman, K., Liebetrau, V., & Menzies, C. (2020). Serpentine alteration as source of high dissolved silicon and elevated δ 30 5 Si 6 values to the marine Si cycle. Nature Communications, 11, Article 5123. https://doi.org/10.1038/s41467-020-18804-y

Journal Article Type Article
Acceptance Date Sep 15, 2020
Online Publication Date Oct 12, 2020
Publication Date 2020
Deposit Date Oct 5, 2020
Publicly Available Date Oct 22, 2020
Journal Nature Communications
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 11
Article Number 5123
DOI https://doi.org/10.1038/s41467-020-18804-y

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