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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Frontiers Media S.A.
2021-03-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2021.551900/full |
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| author | J. Jotautas Baronas J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett Mia M. Bennett Olivier Rouxel Lincoln H. Pitcher Laurence C. Smith |
| author_facet | J. Jotautas Baronas J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett Mia M. Bennett Olivier Rouxel Lincoln H. Pitcher Laurence C. Smith |
| author_sort | J. Jotautas Baronas |
| collection | DOAJ |
| 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 significant differences in Ge behavior during subglacial and non-glacial weathering. |
| first_indexed | 2024-12-22T06:29:36Z |
| format | Article |
| id | doaj.art-54998dff9f854b23b718ddd95eb5917a |
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| language | English |
| last_indexed | 2024-12-22T06:29:36Z |
| publishDate | 2021-03-01 |
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| spelling | doaj.art-54998dff9f854b23b718ddd95eb5917a2022-12-21T18:35:45ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632021-03-01910.3389/feart.2021.551900551900Ge/Si and Ge Isotope Fractionation During Glacial and Non-glacial Weathering: Field and Experimental Data From West GreenlandJ. Jotautas Baronas0J. Jotautas Baronas1Douglas E. Hammond2Mia M. Bennett3Mia M. Bennett4Olivier Rouxel5Lincoln H. Pitcher6Laurence C. Smith7Department of Earth Sciences, University of Southern California, Los Angeles, CA, United StatesDepartment of Earth Sciences, University of Cambridge, Cambridge, United KingdomDepartment of Earth Sciences, University of Southern California, Los Angeles, CA, United StatesDepartment of Geography, University of California Los Angeles, Los Angeles, CA, United StatesDepartment of Geography, The University of Hong Kong, Hong Kong, ChinaIFREMER, Centre De Brest, Unité Géosciences Marines, Plouzané, FranceDepartment of Geography, University of California Los Angeles, Los Angeles, CA, United StatesDepartment of Geography, University of California Los Angeles, Los Angeles, CA, United StatesGlacial 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 significant differences in Ge behavior during subglacial and non-glacial weathering.https://www.frontiersin.org/articles/10.3389/feart.2021.551900/fullglacial weatheringgermaniumisotope fractionationAmorphous silicaexperimental dissolution |
| spellingShingle | J. Jotautas Baronas J. Jotautas Baronas Douglas E. Hammond Mia M. Bennett 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 Frontiers in Earth Science glacial weathering germanium isotope fractionation Amorphous silica experimental dissolution |
| title | 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_short | 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 |
| topic | glacial weathering germanium isotope fractionation Amorphous silica experimental dissolution |
| url | https://www.frontiersin.org/articles/10.3389/feart.2021.551900/full |
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