Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering
<p>Rhenium (Re) is a trace element whose redox chemistry makes it an ideal candidate to trace a range of geochemical processes. Here, we report the first rhenium isotopic measurements (δ<sup>187</sup>Re) from river-borne materials to assess the influence of chemical weath...
| Main Authors: | , , |
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| Format: | Journal article |
| Language: | English |
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Elsevier
2021
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| _version_ | 1826307938035171328 |
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| author | Dellinger, M Hilton, RG Nowell, GM |
| author_facet | Dellinger, M Hilton, RG Nowell, GM |
| author_sort | Dellinger, M |
| collection | OXFORD |
| description | <p>Rhenium (Re) is a trace element whose redox chemistry makes it an ideal candidate to trace a range of geochemical processes. Here, we report the first rhenium isotopic measurements (δ<sup>187</sup>Re) from river-borne materials to assess the influence of chemical weathering on Re isotopes at continental scale. The δ<sup>187</sup>Re was measured in water, suspended sediments and bedloads from the Mackenzie River and its main Arctic tributaries in Northwestern Canada. We find that the δ<sup>187</sup>Re (relative to NIST SRM 989) of river waters ranges from −0.05‰ to +0.07‰, which is generally higher than the corresponding river sediment (−0.25‰ to +0.01‰). We show that the range of δ<sup>187</sup>Re in river sediments (∼0.30‰) is controlled by a combination of source bedrock isotopic variability (provenance) and modern oxidative weathering processes. After correcting for bedrock variability, the δ<sup>187</sup>Re of solids appear to be positively correlated with the amount of Re depletion related to oxidative weathering. This correlation, and the offset in δ<sup>187</sup>Re between river water and sediment, can be explained by preferential oxidation of reactive phases with high δ<sup>187</sup>Re (i.e. rock organic carbon, sulfide minerals), but could also result from fractionation during oxidation or the influence of secondary weathering processes. Overall, we find that both basin-average bedrock δ<sup>187</sup>Re (∼−0.05‰) and dissolved δ<sup>187</sup>Re (∼−0.01‰) in the Mackenzie River are lower than the δ<sup>187</sup>Re of Atlantic seawater (+0.12‰). These observations provide impetus for future work to constrain the Re isotope mass balance of seawater, and assess the potential for secular shifts in its δ<sup>187</sup>Re values over time, which could provide an additional isotopic proxy to trace current and past redox processes at Earth's Surface.</p> |
| first_indexed | 2024-03-07T07:10:40Z |
| format | Journal article |
| id | oxford-uuid:58addb04-1211-4ca9-9b91-a216c21b4029 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T07:10:40Z |
| publishDate | 2021 |
| publisher | Elsevier |
| record_format | dspace |
| spelling | oxford-uuid:58addb04-1211-4ca9-9b91-a216c21b40292022-06-22T14:17:37ZFractionation of rhenium isotopes in the Mackenzie River basin during oxidative weatheringJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:58addb04-1211-4ca9-9b91-a216c21b4029EnglishSymplectic ElementsElsevier2021Dellinger, MHilton, RGNowell, GM<p>Rhenium (Re) is a trace element whose redox chemistry makes it an ideal candidate to trace a range of geochemical processes. Here, we report the first rhenium isotopic measurements (δ<sup>187</sup>Re) from river-borne materials to assess the influence of chemical weathering on Re isotopes at continental scale. The δ<sup>187</sup>Re was measured in water, suspended sediments and bedloads from the Mackenzie River and its main Arctic tributaries in Northwestern Canada. We find that the δ<sup>187</sup>Re (relative to NIST SRM 989) of river waters ranges from −0.05‰ to +0.07‰, which is generally higher than the corresponding river sediment (−0.25‰ to +0.01‰). We show that the range of δ<sup>187</sup>Re in river sediments (∼0.30‰) is controlled by a combination of source bedrock isotopic variability (provenance) and modern oxidative weathering processes. After correcting for bedrock variability, the δ<sup>187</sup>Re of solids appear to be positively correlated with the amount of Re depletion related to oxidative weathering. This correlation, and the offset in δ<sup>187</sup>Re between river water and sediment, can be explained by preferential oxidation of reactive phases with high δ<sup>187</sup>Re (i.e. rock organic carbon, sulfide minerals), but could also result from fractionation during oxidation or the influence of secondary weathering processes. Overall, we find that both basin-average bedrock δ<sup>187</sup>Re (∼−0.05‰) and dissolved δ<sup>187</sup>Re (∼−0.01‰) in the Mackenzie River are lower than the δ<sup>187</sup>Re of Atlantic seawater (+0.12‰). These observations provide impetus for future work to constrain the Re isotope mass balance of seawater, and assess the potential for secular shifts in its δ<sup>187</sup>Re values over time, which could provide an additional isotopic proxy to trace current and past redox processes at Earth's Surface.</p> |
| spellingShingle | Dellinger, M Hilton, RG Nowell, GM Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering |
| title | Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering |
| title_full | Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering |
| title_fullStr | Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering |
| title_full_unstemmed | Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering |
| title_short | Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering |
| title_sort | fractionation of rhenium isotopes in the mackenzie river basin during oxidative weathering |
| work_keys_str_mv | AT dellingerm fractionationofrheniumisotopesinthemackenzieriverbasinduringoxidativeweathering AT hiltonrg fractionationofrheniumisotopesinthemackenzieriverbasinduringoxidativeweathering AT nowellgm fractionationofrheniumisotopesinthemackenzieriverbasinduringoxidativeweathering |