gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1987.051.363.03 Petrology and Geochemistry Stability of Chlorite-Quartz Assemblages in Rocks South and West of Keswick, Cumbria Strens R. G. J. Formerly of School of Physics, University of Newcastle, Newcastle upon Tyne, NE1 7RU Freer R. Department of Metallurgy and Materials Science, University of Manchester/UMIST, Grosvenor Street, Manchester M1 7HS Firman R. J. Department of Geology, University of Nottingham, University Park, Nottingham NG7 2RD 12 1987 51 363 649 654 7 8 1986 9 2 1987 Copyright © 1987, The Mineralogical Society 1987 Abstract

Chlorite minerals from six distinctive chlorite-quartz parageneses in central Borrowdale have been studied. All specimens were 14Å (IIb) chlorites. Cell parameters and β refractive index exhibit an approximate linear dependence on composition for the range Fe/(Fe + Mg) = 0.46 to 0.84. The data indicate an apparent trend that chlorite iron content increases with temperature. This is in conflict with experimental studies (Flemming and Fawcett, 1976), and it is inferred that the observed compositional variations reflect the availability of iron in the veins rather than a dependence on temperature.

 Keywords chlorite chlorite-quartz parageneses Keswick Cumbria