Stable silicon isotope signatures of marine pore waters – Biogenic opal dissolution versus authigenic clay mineral formation
Ehlert, Claudia ; Doering, Kristin LU
; Wallmann, Klaus
; Scholz, Florian
; Sommer, Stefan
; Grasse, Patricia
; Geilert, Sonja
and Frank, Martin
(2016)
In Geochimica et Cosmochimica Acta
191.
p.102-117
- Abstract
Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together... (More)
Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm−2 yr−1. The fractionation factor between the precipitates and the pore waters is estimated at −2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.
(Less)
- author
- Ehlert, Claudia
; Doering, Kristin
LU
; Wallmann, Klaus
; Scholz, Florian
; Sommer, Stefan
; Grasse, Patricia
; Geilert, Sonja
and Frank, Martin
- publishing date
- 2016-10-15
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Authigenic alumino-silicates, Biogenic opal, Pore water, Silicic acid, Silicon isotopes
- in
- Geochimica et Cosmochimica Acta
- volume
- 191
- pages
- 16 pages
- publisher
- Elsevier
- external identifiers
-
- scopus:84979746902
- ISSN
- 0016-7037
- DOI
- 10.1016/j.gca.2016.07.022
- language
- English
- LU publication?
- no
- additional info
- Funding Information: This work is a contribution of Sonderforschungsbereich 754 “Climate – Biogeochemistry Interactions in the Tropical Ocean” ( www.sfb754.de ), which is supported by the Deutsche Forschungsgemeinschaft . The Seventh Framework Program of the European Union supported the participation of F.S. (Marie Curie IOF 300648, BICYCLE). We thank M. Dibbern, B. Domeyer, R. Ebbinghaus, N. Glock, J. Heinze, C. Hensen, S. Kriwanek, A. Noffke, A. Petersen, R. Surberg and M. Türk for technical assistance during sampling and analysis. Publisher Copyright: © 2016 Elsevier Ltd
- id
- 2c864e32-7141-4919-83ae-da5208ab068a
- date added to LUP
- 2022-09-05 12:25:26
- date last changed
- 2022-09-15 21:46:29
@article{2c864e32-7141-4919-83ae-da5208ab068a,
abstract = {{<p>Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ<sup>30</sup>Si<sub>PW</sub>) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ<sup>30</sup>Si<sub>PW</sub> varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ<sup>30</sup>Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm<sup>−2</sup> yr<sup>−1</sup>. The fractionation factor between the precipitates and the pore waters is estimated at −2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.</p>}},
author = {{Ehlert, Claudia and Doering, Kristin and Wallmann, Klaus and Scholz, Florian and Sommer, Stefan and Grasse, Patricia and Geilert, Sonja and Frank, Martin}},
issn = {{0016-7037}},
keywords = {{Authigenic alumino-silicates; Biogenic opal; Pore water; Silicic acid; Silicon isotopes}},
language = {{eng}},
month = {{10}},
pages = {{102--117}},
publisher = {{Elsevier}},
series = {{Geochimica et Cosmochimica Acta}},
title = {{Stable silicon isotope signatures of marine pore waters – Biogenic opal dissolution versus authigenic clay mineral formation}},
url = {{http://dx.doi.org/10.1016/j.gca.2016.07.022}},
doi = {{10.1016/j.gca.2016.07.022}},
volume = {{191}},
year = {{2016}},
}