Iron Isotopes Reveal Fe Export Driven by Change of Tropical Weathering Regime
Abstract
Abstract Unraveling paleoenvironmental signals recorded in laterites is crucial for quantifying weathering‐driven elemental fluxes at the Earth's surface. New stable iron isotope data (δ 56 Fe), combined with (U‐Th)/He ages in Fe‐oxides from a ferruginous duricrust from French Guiana, reveal the response of Fe hosted in laterite to past changes in weathering intensity. The δ 56 Fe values increase with decreasing age, with a pronounced shift at around 6 Ma reflecting a change from a ferruginous laterization to a bauxitization regime. This shift indicates a transition from a weathering regime characterized by Fe redistribution within the laterite to one featuring significant Fe loss and redox processes. Isotope mass‐balance modeling reveals that intensified weathering during the bauxitization phase led to the loss of 35%–70% of Fe from the duricrust. Our work highlights the importance of lateritic profiles as environmental archives.
// Source
Authors: Zuzana Fekiacova-Castanet, Beatrix Heller, Damien Guinoiseau, Julien Bouchez, Adrien Duvivier, Sophie Cornu, Abel Guihou, Cécile Quantin, Thierry Allard, Silvana Bressan Riffel, Pierre Deschamps, Cécile Gautheron
Institutions: Universidade Federal do Rio Grande do Sul, Université Grenoble Alpes, Université Paris Cité, Sorbonne Université, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement, Centre National de la Recherche Scientifique, Université Paris-Saclay, Institut de Recherche pour le Développement, Aix-Marseille Université, Université Gustave Eiffel, Institut de physique du globe de Paris, Institut des Sciences de la Terre, Université Savoie Mont Blanc, Structure et Instabilité des Génomes, Centre de Recherche et d’Enseignement de Géosciences de l’Environnement, Geosciences Paris-Saclay