Dataset Information

Serpentine alteration as source of high dissolved silicon and elevated ?³⁰Si values to the marine Si cycle.

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 (?³⁰Si, ?¹¹B, 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 ?³⁰Si 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 ?³⁰Si 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.

SUBMITTER: Geilert S

PROVIDER: S-EPMC7550359 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Serpentine alteration as source of high dissolved silicon and elevated δ30Si values to the marine Si cycle.

Geilert Sonja S Grasse Patricia P Wallmann Klaus K Liebetrau Volker V Menzies Catriona D CD

Nature communications 20201012 1

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 se ...[more]

PMID: 33046703

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Project description:Stable oxygen isotope (δ18O) compositions from vertebrate tooth enamel are widely used as biogeochemical proxies for paleoclimate. However, the utility of enamel oxygen isotope values for environmental reconstruction varies among species. Herein, we evaluate the use of stable oxygen isotope compositions from pronghorn (Antilocapra americana Gray, 1866) enamel for reconstructing paleoclimate seasonality, an elusive but important parameter for understanding past ecosystems. We serially sampled the lower third molars of recent adult pronghorn from Wyoming for δ18O in phosphate (δ18OPO4) and compared patterns to interpolated and measured yearly variation in environmental waters as well as from sagebrush leaves, lakes, and rivers (δ18Ow). As expected, the oxygen isotope compositions of phosphate from pronghorn enamel are enriched in 18O relative to environmental waters. For a more direct comparison, we converted δ18Ow values into expected δ18OPO4* values (δ18OW-PO4*). Pronghorn δ18OPO4 values from tooth enamel record nearly the full amplitude of seasonal variation from Wyoming δ18OW-PO4* values. Furthermore, pronghorn enamel δ18OPO4 values are more similar to modeled δ18OW-PO4* values from plant leaf waters than meteoric waters, suggesting that they obtain much of their water from evaporated plant waters. Collectively, our findings establish that seasonality in source water is reliably reflected in pronghorn enamel, providing the basis for exploring changes in the amplitude of seasonality of ancient climates. As a preliminary test, we sampled historical pronghorn specimens (1720 ± 100 AD), which show a mean decrease (a shift to lower values) of 1-2‰ in δ18OPO4 compared to the modern specimens. They also exhibit an increase in the δ18O amplitude, representing an increase in seasonality. We suggest that the cooler mean annual and summer temperatures typical of the 18th century, as well as enhanced periods of drought, drove differences among the modern and historical pronghorn, further establishing pronghorn enamel as excellent sources of paleoclimate proxy data.

Dataset Information

Serpentine alteration as source of high dissolved silicon and elevated ?³⁰Si values to the marine Si cycle.

Publications

Serpentine alteration as source of high dissolved silicon and elevated δ<sup>30</sup>Si values to the marine Si cycle.

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Dataset Information

Serpentine alteration as source of high dissolved silicon and elevated ?30Si values to the marine Si cycle.

Publications

Serpentine alteration as source of high dissolved silicon and elevated δ<sup>30</sup>Si values to the marine Si cycle.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Serpentine alteration as source of high dissolved silicon and elevated ?³⁰Si values to the marine Si cycle.