gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1991.055.379.09 Mineralogy and Geochemistry Sulphur Isotope Evidence for the Origin of Cave Evaporites in Ogof y Daren Cilau, South Wales Bottrell Simon H. Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, U.K. 6 1991 55 379 209 210 14 3 1990 30 7 1990 Copyright © 1991, The Mineralogical Society 1991 Abstract

Gypsum evaporites are forming under desiccating conditions in relict cave passages in Mynydd Llangattwg, south Wales. Sulphur isotope compositions of these sulphates indicate that oxidation of diagenetic pyrite in the overlying Millstone Grit is the source of sulphate solutions, rather than dissolution of evaporitic sulphate in the limestones.

 Keywords gypsum evaporites sulphur isotopes caves Wales