Description
Silicon (Si) plays a critical role during mineral dissolution and neo-formation processes in Earth’s near-surface environments and is mobilized during continental and seafloor silicate weathering and subsequently transported or released as silicic acid (Si(OH)4) to the ocean. In the modern ocean, Si(OH)4 is sequestered by silicifying organisms and various silicate minerals, such as authigenic clay minerals. The Si cycle is of particular interest within the critical zone (CZ), where Si is suspected to first precipitate as amorphous, gel-like phases, such as short-range ordered hydroxyaluminosilicates (HAS: e.g., allophane) and hydrous ferric silicates (HFS: e.g., hisingerite). These highly reactive minerals serve as precursors to the formation of important soil clay minerals, such as those of the smectite and kaolinite group. To decode the reaction paths and the environmental controls underlying HAS and HFS formation, the use of Si isotope fractionation can be a powerful tool. Therefore, a series of silica and allophane-hisingerite precipitation experiments at high temporal resolution has been performed to investigate and assess the kinetic Si isotope fractionation between the reactive fluid and the precipitating solid phase at room temperature. The kinetics of the precipitation reaction increased from amorphous Si < HAS < HFS. Further, large Si isotope fractionation followed by highly dynamic Si isotope exchange during HAS and HFS formation and structural re-organization was observed, following a Rayleigh-type fractionation model. Within 16 days, close to steady state conditions were reached, where the Si isotopic composition of the precipitates approached those found in allophanes and other clay minerals| Period | 29 May 2024 → 31 May 2024 |
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| Event title | Isotopen in Biogenic Silica |
| Event type | Conference |
| Location | Louvain-La-Neuve, BelgiumShow on map |
| Degree of Recognition | International |