Alteration of Phlogopite to Corrensite at Sharbot Lake, Ontario1

C. R. De Kimpe2, 5, N. Miles3, H. Kodama3 and J. Dejou4
2 Agriculture Canada Research Station, 2560 Boulevard Hochelaga Sainte-Foy, Quebec G1V 2J3, Canada
3 Land Resource Research Center, Agriculture Canada, Central Experimental Farm Ottawa, Ontario K1A 0C6, Canada
4 INRA, Station d'Agronomie, 12 Ave. de l'Agriculture 63039 Clermont-Ferrand Cedex, France
1 Contribution no. 304 Sainte-Foy Agriculture Canada Research Station and no. 87-25 Land Resource Research Center, Ottawa.
5 Present address: Land Resource Research Center, Agriculture Canada, Central Experimental Farm, Ottawa, Ontario K1A 0C6.

Abstract: A low-charge corrensite, i.e., a regular 1:1 interstratified smectite/chlorite was found in veins and fissures of an extensively fractured dolomite south of Perth, Ontario, Canada. Total chemical analysis indicated that the mineral was trioctahedral, having a structural formula corresponding to: ( Ca 0.17 ) ( Mg 7.36 Al 0.90 Fe 3+ F 0.45 e 2+ ) 0.42 ( Si 6.06 Al 1.94 ) VI IV O 20 (OH) 10 . The coefficient of variation (CV) of the d(00l) spacings calculated for the mineral from X-ray powder diffraction data was 0.42, well below the maximum recommended value for corrensite, 0.75. The corrensite coexists with phlogopite, which is present as small (∼0.5 mm) crystals throughout the rock and locally as large (∼ 5 cm) crystals in pegmatitic veins. Microscopic observations of large phlogopite crystals partially altered to corrensite suggest that corrensite formed at the expense of phlogopite by hydrothermal alteration.

Key Words: Corrensite • Hydrothermal alteration • Interstratification • Phlogopite

Clays and Clay Minerals; April 1987 v. 35; no. 2; p. 150-158; DOI: 10.1346/CCMN.1987.0350207
© 1987, The Clay Minerals Society
Clay Minerals Society (www.clays.org)