Lithium and potassium isotope fractionation during silicate rock dissolution: An experimental approach

This study experimentally investigates the isotopic behaviors of Li and K during dissolution silicate rocks (i.e., basalt granite). Proton-driven (in 0.8 M HNO3) ligand-driven 5 mM critic acid or oxalic acid) experiments were performed in batch-closed systems over 15 days. We provide a time-series interpretation isotope fractionation ultra-acidic (unidirectional) near-natural (biologically affected) environments. As reaction progressed, we measured large between liquid (l) phase pristine (s) phase, ranging from −10.3 to 0.1‰ (Δ7Lil-s) −1.01 −0.11‰ (Δ41Kl-s) through early stage (<24 h). The enrichment lighter isotopes solutions rapidly diminished as rock continued gradually approached equilibrium end experiments. In contrast, resorption pre-leached isotopically on residuals produced compared initial by up 2.8‰. Despite preferential specific minerals, patterns do not vary with lithology, indicating limited inter-mineral differences. During experiments, pattern could be divided into two-to-three stages. light liquids can ascribed kinetic effect, confounded diffusion ion solvation. A later transition towards no may explained (i) masking effect dissolution, (ii) an imprint destruction 7Li/41K-enriched surface layers. Lateral solute after ~100 h facilitated electrostatic attraction increasing negative charges active hydroxyls pH (pH ~ 4) relative proton-driven 0.2). Therefore, presence organic ligands impacts stoichiometry, potentially modifies natural weathering comparison, driven stops immediately (within days) starting research helps understand mechanisms chemical trace long-term climate change using geological records.