Published online by Cambridge University Press: 01 May 2009
The contents of CaO and Al2O3 in pelites from areas subjected to amphibolite facies metamorphism have been plotted in order to discover the compositional limit of the stability field of the aluminium silicate minerals. Rocks containing kyanite or sillimanite fall within a well-defined field, while rocks plotting outside this field are devoid of aluminium silicate minerals, irrespective of metamorphic grade. With the trace of the curve bounding this field known, the position of the kyanite isograd may be more easily plotted in areas where kyanite or sillimanite are rare.