The Kyanite Isograd in Glen Clova, Angus, Scotland

G. A. Chinner
Department of Mineralogy and Petrology, Cambridge University

Summary: Mineral data from Glen Clova, Angus, suggest that the development of kyanite in graphite-bearing staurolite mica-schists, treated in terms of a Ca-free system, involved decrease of staurolite and a decrease in biotite MgO:FeO ratio. A kyanite isograd may be defined in Glen Clova as the locality where kyanite joins the assemblage staurolite-garnet-biotite-muscovite-plagioclase-quartz-graphite, the biotite having mol. MgO×100MgO+FeO=51·7, although the persistence of this identical assemblage over some 600 metres introduces some uncertainty of interpretation. It is suggested that the reaction staurolite+quartz → garnet+kyanite is unlikely to be a common reaction in nature and that its use to subdivide the am-phibolite facies is unjustified.

Mineralogical Magazine; 1965 v. 34; no. 268; p. 132-143; DOI: 10.1180/minmag.1965.034.268.11
© 1965, The Mineralogical Society
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