The evolution of lithium isotope signatures in fluids draining actively weathering hillslopes

The stable isotopes of lithium (Li) serve as a robust proxy silicate weathering. fate and transport these in the dissolved load major rivers have been characterized to infer changes both contemporary weathering regimes paleo-conditions. In this contribution, we deconvolve integrated signal into individual processes that fractionate Li at inception by directly measuring isotope ratios waters (δ7Li) transiting through rapidly eroding first-order hillslope. We use data develop multicomponent reactive framework, which shows net dissolution weathered material generates light δ7Li signatures (as low −9.2‰) shallow portion vadose zone. An increase deeper zone much +18‰) reflects an increasing contribution secondary mineral formation. Below water table, congruent occurs imparts elevated cation concentrations bedrock δ7Li. Silicate continues within saturated groundwater travels downslope (δ7Li = +13 + 24‰) stream. stream +28 +29‰) reflect terminus network reactions relative magnitude each contributing process (e.g., transitions formation, material). show fluid progressing profile hillslope is distinguished sequence characteristic signatures, can be reproduced forward, process-based model framework. This development offers improved quantitative basis for metal(loid) disentangling catchment-scale chemical fluxes.