gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1998.62A.1.149 Molecular Diffusion as a Source of Noble Gas Fractionation in Groundwaters. Hydrodynamic Implications. A Case Study, the Paris Basin Castro M. C. Schlosser P. Lamont-Doherty Earth Observatory of Columbia University, RT 9W, Palisades 10964, NY, USA Jambon A. Laboratoire MAGIE, Université Paris VI, URA/CNRS 1762, 75252 Paris CEDEX 05, France de Marsily G. Laboratoire de Géologie Appliquée, Université Paris VI, URA/CNRS 1367, 75252 Paris Cedex 05, France 1998 62A 1 282 283 Copyright © 1998, The Mineralogical Society 1998