『Abstract
Hafnium 176Hf/177Hf isotope ratio variations
in marine records are thought to reflect changes in continental
weathering through time, but the behavior of Hf in rivers, and
during weathering, is not well understood. Here, we present 176Hf/177Hf
data for rivers, bedrock, soils, and leaching experiments for
the Moselle basin, Vosges, France. These data strongly suggest
that the 176Hf/177Hf composition of river
waters is controlled by preferential dissolution of accessory
phases (i.e., apatite, sphene) versus more resistant minerals
(e.g., K-feldspar) and linked to the intensity of silicate weathering.
Estimates for the global isotopic composition of riverine Hf suggest
that the ocean Hf budget may be dominated by river input, and
variations seen in marine records can be directly related to changes
in silicate weathering intensity.
Keywords: hafnium isotopes; rivers; silicate weathering; ocean
chemistry』
Introduction
Materials and methods
Results
Linking Hf isotopes to silicate weathering processes
Evidence from partition coefficient ratios
Evidence from granite leaching experiments
Evidence from river chemistry
Implications for the ocean Hf budget and the evolution of seawater
εHf through time
Acknowledgments
References cited