{"type": "FeatureCollection", "features": [{"id": "10.1016/j.chemgeo.2021.120283", "type": "Feature", "geometry": null, "properties": {"updated": "2026-05-31T06:56:42Z", "type": "Journal Article", "created": "2021-04-27", "title": "Imprint of chemical weathering and hydrothermalism on the Ge/Si ratio and Si isotope composition of rivers in a volcanic tropical island, Basse-Terre, Guadeloupe (French West Indies)", "description": "Abstract   A significant portion of the disproportionally high chemical weathering flux in volcanic island arcs may originate from hydrothermal fluid-rock interaction, thereby compromising the accurate estimate of atmospheric CO2 consumption rates. The objective of this study is to evaluate how the riverine Ge/Si ratio and Si isotopes, two well-established tracers of weathering, respond to hydrothermal inputs. The work took place in Basse-Terre, Guadeloupe, a tropical volcanic island with a dense river network, high chemical weathering fluxes and various hydrothermal surface manifestations. We characterized the Ge/Si ratio and \u03b430Si of 15 thermal springs, nine non-impacted (NI) rivers and 13 hydrothermally-impacted (HI) rivers. The soil solution from a highly weathered soil profile (Ferralsol) and a clayey-rock corresponding to the material exposed in an extinct hydrothermal system were also measured. A new purification method was successfully developed in order to allow the reliable measurement of Si isotopes in SO42\u2212- and Cl\u2212-rich thermal spring and HI river waters by mass spectrometry. Basse-Terre's thermal springs have variable Ge/Si ratios (0.05\u201321.03\u00a0\u03bcmol.mol\u22121) and \u03b430Si (0.71\u20131.50\u2030), but with no apparent relationship to the water compositional type. The Ge/Si ratio (0.15\u20132.57\u00a0\u03bcmol.mol\u22121) and Si isotope composition (0.26\u20131.21\u2030) values of the NI rivers reveal differences in the watersheds' weathering degree. Dissolution of Ge- and 28Si-rich secondary minerals explains the high Ge/Si and isotopically light composition of the northern NI rivers draining strongly weathered terranes. The Ge/Si ratio and \u03b430Si values measured for the NI and HI rivers overlap, implying that they cannot be used to diagnose hydrothermal contributions to river basins unambiguously. However, when combined with the Cl\u2212 and SO42\u2212 concentrations, the analysis of Ge and Si in the HI rivers suggests that water seeping through an extinct hydrothermal system produces SO4-rich drainages with distinctively lower Ge/Si ratios than those inferred for watersheds receiving thermal spring discharges associated with an active hydrothermal system. Overall, our results provide new constraints for applying and interpreting Ge/Si and Si isotope measurements to study weathering in volcanic environments.", "keywords": ["[SDE] Environmental Sciences", "Volcanic hydrothermal system", "Chemical weathering", "River geochemistry", "Si isotope", "Ge/Si ratio", "13. Climate action", "[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry", "Guadeloupe", "01 natural sciences", "6. Clean water", "0105 earth and related environmental sciences"]}, "links": [{"href": "https://doi.org/10.1016/j.chemgeo.2021.120283"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Chemical%20Geology", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1016/j.chemgeo.2021.120283", "name": "item", "description": "10.1016/j.chemgeo.2021.120283", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1016/j.chemgeo.2021.120283"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2021-09-01T00:00:00Z"}}, {"id": "10.1016/j.gca.2019.06.035", "type": "Feature", "geometry": null, "properties": {"license": "Open Access", "updated": "2026-05-31T06:57:10Z", "type": "Journal Article", "created": "2019-07-02", "title": "Experimentally determined Si isotope fractionation between zircon and quartz", "description": "Abstract   The silicon isotope composition of detrital quartz and zircon have the potential to inform us about secular changes to the silica cycle and weathering reactions on Earth. However, inferring source melt Si isotope composition from out-of-context minerals is hampered by the fact that, to-date, there is limited Si isotope equilibrium fractionation data for minerals. Here, we report experimental data to constrain Si isotope equilibrium fractionation between zircon and quartz, using two fundamentally different strategies, but with the same experimental design. First, zircon and quartz were hydrothermally synthesized from Zr(OH)4 and SiO2 at 1.5\u202fGPa and temperatures of 725, 800, and 900\u202f\u00b0C. The second experimental strategy utilized the three-isotope method; the starting materials consisted of natural zircon and isotopically-labelled SiO2. Three sets of hydrothermal time-series experiments were conducted at the same pressure and temperatures as the direct synthesis experiments. For all experiments, quartz and zircon were separated and 30Si/28Si and 29Si/28Si ratios were measured by solution multi-collector inductively coupled plasma mass spectrometry. The three-isotope method, which provides the best indicator of equilibrium fractionations, yields the following relationship:        \u0394   30   S  i   (  q  t  z  -  z  r  c  )   =   (  0.53  \u00b1  0.14  )   \u00d7    10   6   /    T   2       where \u039430Si(qtz-zrc) is the relative difference in 30Si/28Si between quartz and zircon in permil, T is temperature in K, and the error is 2\u202fs.e. This relationship can be used to calculate the fractionation between zircon and other phases, and to estimate the Si isotope composition of the melt from which a zircon crystallized. The results may be used to assess equilibrium-disequilibrium isotope fractionations between quartz and zircon and co-existing phases in igneous rocks. These data can also be applied to out-of-context zircon (and quartz) to estimate the isotope composition of the host rock. Zircons crystallizing from a melt derived from purely igneous sources \u2013 i.e., without the involvement of \u201cweathered\u201d material \u2013 are expected to display a \u03b430SiNBS-28 (permil deviation of the 30Si/28Si from the NBS-28 standard) range from \u22120.7 to \u22120.35\u2030. Deviations from this range indicate assimilation of non-igneous (i.e., sedimentary) material in the melt source.", "keywords": ["Zircon", "GE", "550", "NDAS", "Quartz", "Si isotopes", "7. Clean energy", "01 natural sciences", "Three-istope", "[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry", "13. Climate action", "Igneous", "Three-isotope", "[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry", "Fractionation", "GE Environmental Sciences", "0105 earth and related environmental sciences"]}, "links": [{"href": "https://doi.org/10.1016/j.gca.2019.06.035"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Geochimica%20et%20Cosmochimica%20Acta", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1016/j.gca.2019.06.035", "name": "item", "description": "10.1016/j.gca.2019.06.035", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1016/j.gca.2019.06.035"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2019-09-01T00:00:00Z"}}, {"id": "2078.1/246033", "type": "Feature", "geometry": null, "properties": {"updated": "2026-05-31T07:06:03Z", "type": "Journal Article", "created": "2021-04-27", "title": "Imprint of chemical weathering and hydrothermalism on the Ge/Si ratio and Si isotope composition of rivers in a volcanic tropical island, Basse-Terre, Guadeloupe (French West Indies)", "description": "Abstract   A significant portion of the disproportionally high chemical weathering flux in volcanic island arcs may originate from hydrothermal fluid-rock interaction, thereby compromising the accurate estimate of atmospheric CO2 consumption rates. The objective of this study is to evaluate how the riverine Ge/Si ratio and Si isotopes, two well-established tracers of weathering, respond to hydrothermal inputs. The work took place in Basse-Terre, Guadeloupe, a tropical volcanic island with a dense river network, high chemical weathering fluxes and various hydrothermal surface manifestations. We characterized the Ge/Si ratio and \u03b430Si of 15 thermal springs, nine non-impacted (NI) rivers and 13 hydrothermally-impacted (HI) rivers. The soil solution from a highly weathered soil profile (Ferralsol) and a clayey-rock corresponding to the material exposed in an extinct hydrothermal system were also measured. A new purification method was successfully developed in order to allow the reliable measurement of Si isotopes in SO42\u2212- and Cl\u2212-rich thermal spring and HI river waters by mass spectrometry. Basse-Terre's thermal springs have variable Ge/Si ratios (0.05\u201321.03\u00a0\u03bcmol.mol\u22121) and \u03b430Si (0.71\u20131.50\u2030), but with no apparent relationship to the water compositional type. The Ge/Si ratio (0.15\u20132.57\u00a0\u03bcmol.mol\u22121) and Si isotope composition (0.26\u20131.21\u2030) values of the NI rivers reveal differences in the watersheds' weathering degree. Dissolution of Ge- and 28Si-rich secondary minerals explains the high Ge/Si and isotopically light composition of the northern NI rivers draining strongly weathered terranes. The Ge/Si ratio and \u03b430Si values measured for the NI and HI rivers overlap, implying that they cannot be used to diagnose hydrothermal contributions to river basins unambiguously. However, when combined with the Cl\u2212 and SO42\u2212 concentrations, the analysis of Ge and Si in the HI rivers suggests that water seeping through an extinct hydrothermal system produces SO4-rich drainages with distinctively lower Ge/Si ratios than those inferred for watersheds receiving thermal spring discharges associated with an active hydrothermal system. Overall, our results provide new constraints for applying and interpreting Ge/Si and Si isotope measurements to study weathering in volcanic environments.", "keywords": ["[SDE] Environmental Sciences", "Volcanic hydrothermal system", "Chemical weathering", "River geochemistry", "Si isotope", "Ge/Si ratio", "13. Climate action", "[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry", "Guadeloupe", "01 natural sciences", "6. 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