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| Bayon, Germain; Vigier, Nathalie; Burton, Kevin W.; Brenot, Agnès; Carignan, Jean; Etoubleau, Joel; Chu, Nan-chin. |
| Hafnium Hf-176/Hf-177 isotope ratio variations in marine records are thought to reflect changes in continental weathering through time, but the behavior of Hf in rivers, and during weathering, is not well understood. Here, we present Hf-176/Hf-177 data for rivers, bedrock, soils, and leaching experiments for the Moselle basin, Vosges, France. These data strongly suggest that the Hf-176/Hf-177 composition of river waters is controlled by preferential dissolution of accessory phases (i.e., apatite, sphene) versus more resistant minerals (e.g., K-feldspar) and linked to the intensity of silicate weathering. Estimates for the global isotopic composition of riverine Hf suggest that the ocean Hf budget may be dominated by river input, and variations seen in... |
| Tipo: Text |
Palavras-chave: Ocean chemistry; Silicate weathering; Rivers; Hafnium isotopes. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2078.pdf |
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| Baronas, J. Jotautas; West, A. Joshua; Burton, Kevin W.; Hammond, Douglas E.; Opfergelt, Sophie; Pogge Von Strandmann, Philip A. E.; James, Rachael H.; Rouxel, Olivier. |
| Chemical weathering of volcanic rocks in warm and humid climates contributes disproportionately to global solute fluxes. Geochemical signatures of solutes and solids formed during this process can help quantify and reconstruct weathering intensity in the past. Here, we measured silicon (Si) and germanium (Ge) isotope ratios of the soils, clays, and fluids from a tropical lowland rainforest in Costa Rica. The bulk topsoil is intensely weathered and isotopically light (mean ± 1σ: δ30Si = −2.1 ± 0.3‰, δ74Ge = −0.13 ± 0.12‰) compared to the parent rock (δ30Si = −0.11 ± 0.05‰, δ74Ge = 0.59 ± 0.07‰). Neoforming clays have even lower values (δ30Si = −2.5 ± 0.2‰, δ74Ge = −0.16 ± 0.09‰), demonstrating a whole‐system isotopic shift in extremely weathered systems.... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75484/76330.pdf |
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