The control of weathering processes on riverine and seawater hafnium isotope ratios
- Germain Bayon1,
- Nathalie Vigier2,
- Kevin W. Burton3,
- Agnès Brenot, Jean Carignan4,
- Joël Etoubleau5 and
- Nan-Chin Chu6
- 1Département des Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, 29280 Plouzané, France
- 2Centre de Recherches Pétrographiques et Géochimiques, 15 rue Notre-Dame des Pauvres, 54501 Vandoeuvre-lès-Nancy, France
- 3Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK
- 4 Centre de Recherches Pétrographiques et Géochimiques, 15 rue Notre-Dame des Pauvres, 54501 Vandoeuvre-lès-Nancy, France
- 5Département des Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, 29280 Plouzané, France
- 6Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
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.
Footnotes
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↵GSA Data Repository item 2006085, material and methods, Tables DR1–3, and details on calculations, is available online at www.geosociety.org/pubs/ft2006.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Accepted 17 January 2006.
- Received 16 August 2005.
- Revision received 13 January 2006.
- The Geological Society of America, Inc.
