Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland
Glacial environments offer the opportunity to study the incipient stages of chemical weathering due to the high availability of finely ground sediments, low water temperatures, and typically short rock-water interaction times. In this study we focused on the geochemical behavior of germanium (Ge) in...
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ftdoajarticles:oai:doaj.org/article:54998dff9f854b23b718ddd95eb5917a 2023-05-15T16:21:31+02:00 Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett Olivier Rouxel Lincoln H. Pitcher Laurence C. Smith 2021-03-01T00:00:00Z https://doi.org/10.3389/feart.2021.551900 https://doaj.org/article/54998dff9f854b23b718ddd95eb5917a EN eng Frontiers Media S.A. https://www.frontiersin.org/articles/10.3389/feart.2021.551900/full https://doaj.org/toc/2296-6463 2296-6463 doi:10.3389/feart.2021.551900 https://doaj.org/article/54998dff9f854b23b718ddd95eb5917a Frontiers in Earth Science, Vol 9 (2021) glacial weathering germanium isotope fractionation Amorphous silica experimental dissolution Science Q article 2021 ftdoajarticles https://doi.org/10.3389/feart.2021.551900 2022-12-31T12:57:45Z Glacial environments offer the opportunity to study the incipient stages of chemical weathering due to the high availability of finely ground sediments, low water temperatures, and typically short rock-water interaction times. In this study we focused on the geochemical behavior of germanium (Ge) in west Greenland, both during subglacial weathering by investigating glacier-fed streams, as well as during a batch reactor experiment by allowing water-sediment interaction for up to 2 years in the laboratory. Sampled in late August 2014, glacial stream Ge and Si concentrations were low, ranging between 12–55 pmol/L and 7–33 µmol/L, respectively (Ge/Si = 0.9–2.2 µmol/mol, similar to parent rock). As reported previously, the dissolved stable Ge isotope ratio (δ74Ge) of the Watson River was 0.86 ± 0.24‰, the lowest among global rivers and streams measured to date. This value was only slightly heavier than the suspended load (0.48 ± 0.23‰), which is likely representative of the bulk parent rock composition. Despite limited Ge/Si and δ74GeGe fractionation, both Ge and Si appear depleted relative to Na during subglacial weathering, which we interpret as the relatively congruent uptake of both phases by amorphous silica (aSi). Continued sediment-water interaction over 470–785 days in the lab produced a large increase in dissolved Si concentrations (up to 130–230 µmol/L), a much smaller increase in dissolved Ge (up to ∼70 pmol/L), resulting in a Ge/Si decrease (to 0.4–0.5 µmol/mol) and a significant increase in δ74Ge (to 1.9–2.2‰). We argue that during the experiment, both Si and Ge are released by the dissolution of previously subglacially formed aSi, and Ge is then incorporated into secondary phases (likely adsorbed to Fe oxyhydroxides), with an associated Δ74Gesecondary−dissolved fractionation factor of −2.15 ± 0.46‰. In summary, we directly demonstrate Ge isotope fractionation during the dissolution-precipitation weathering reactions of natural sediments in the absence of biological Ge and Si uptake, and highlight the ... Article in Journal/Newspaper glacier Greenland Directory of Open Access Journals: DOAJ Articles Greenland Frontiers in Earth Science 9 |
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English |
topic |
glacial weathering germanium isotope fractionation Amorphous silica experimental dissolution Science Q |
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glacial weathering germanium isotope fractionation Amorphous silica experimental dissolution Science Q J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett Olivier Rouxel Lincoln H. Pitcher Laurence C. Smith Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland |
topic_facet |
glacial weathering germanium isotope fractionation Amorphous silica experimental dissolution Science Q |
description |
Glacial environments offer the opportunity to study the incipient stages of chemical weathering due to the high availability of finely ground sediments, low water temperatures, and typically short rock-water interaction times. In this study we focused on the geochemical behavior of germanium (Ge) in west Greenland, both during subglacial weathering by investigating glacier-fed streams, as well as during a batch reactor experiment by allowing water-sediment interaction for up to 2 years in the laboratory. Sampled in late August 2014, glacial stream Ge and Si concentrations were low, ranging between 12–55 pmol/L and 7–33 µmol/L, respectively (Ge/Si = 0.9–2.2 µmol/mol, similar to parent rock). As reported previously, the dissolved stable Ge isotope ratio (δ74Ge) of the Watson River was 0.86 ± 0.24‰, the lowest among global rivers and streams measured to date. This value was only slightly heavier than the suspended load (0.48 ± 0.23‰), which is likely representative of the bulk parent rock composition. Despite limited Ge/Si and δ74GeGe fractionation, both Ge and Si appear depleted relative to Na during subglacial weathering, which we interpret as the relatively congruent uptake of both phases by amorphous silica (aSi). Continued sediment-water interaction over 470–785 days in the lab produced a large increase in dissolved Si concentrations (up to 130–230 µmol/L), a much smaller increase in dissolved Ge (up to ∼70 pmol/L), resulting in a Ge/Si decrease (to 0.4–0.5 µmol/mol) and a significant increase in δ74Ge (to 1.9–2.2‰). We argue that during the experiment, both Si and Ge are released by the dissolution of previously subglacially formed aSi, and Ge is then incorporated into secondary phases (likely adsorbed to Fe oxyhydroxides), with an associated Δ74Gesecondary−dissolved fractionation factor of −2.15 ± 0.46‰. In summary, we directly demonstrate Ge isotope fractionation during the dissolution-precipitation weathering reactions of natural sediments in the absence of biological Ge and Si uptake, and highlight the ... |
format |
Article in Journal/Newspaper |
author |
J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett Olivier Rouxel Lincoln H. Pitcher Laurence C. Smith |
author_facet |
J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett Olivier Rouxel Lincoln H. Pitcher Laurence C. Smith |
author_sort |
J. Jotautas Baronas |
title |
Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland |
title_short |
Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland |
title_full |
Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland |
title_fullStr |
Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland |
title_full_unstemmed |
Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West Greenland |
title_sort |
ge/si and ge isotope fractionation during glacial and non-glacial weathering: field and experimental data from west greenland |
publisher |
Frontiers Media S.A. |
publishDate |
2021 |
url |
https://doi.org/10.3389/feart.2021.551900 https://doaj.org/article/54998dff9f854b23b718ddd95eb5917a |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland |
genre_facet |
glacier Greenland |
op_source |
Frontiers in Earth Science, Vol 9 (2021) |
op_relation |
https://www.frontiersin.org/articles/10.3389/feart.2021.551900/full https://doaj.org/toc/2296-6463 2296-6463 doi:10.3389/feart.2021.551900 https://doaj.org/article/54998dff9f854b23b718ddd95eb5917a |
op_doi |
https://doi.org/10.3389/feart.2021.551900 |
container_title |
Frontiers in Earth Science |
container_volume |
9 |
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1766009523075547136 |