Metasomatism in the Kamiskotia Mafic Complex

Abstract

Metasomatism was taken by Goldschmidt (1922) as being metamorphism involving introduction and removal of certain substances, with a corresponding change in the chemistry and mineralogy of the rock concerned. Using this definition, there is strong evidence of metasomatism having played an important role in the transformation of part of the Kamiskotia mafic intrusion from a norite to a greenschist facies rock. The importance of metasomatism has generally proved difficult to evaluate because of disagreement on a quantitative approach to the problem. Two of the approaches suggested in the literature have been employed to characterize the chemical changes accompanying metamorphism of the Kamiskotia complex; one assuming constant volume, the other assuming constant alumina. The latter approach, supported by most recent work in this area (Carmichael, 1970; Korzhinsky, 1964) is favoured. It defines a mobility series that agrees quite well with Korzhinsky's for all elements except iron. It is concluded that metamorphism, of the Kamiskotia norite has been accompanied by significant removal of potash, soda, iron and silica besides the addition of water and carbon dioxide. Reactions, constructed on the basis of mineral relationships observed in thin section combined with the calculated chemical changes are proposed. The source of the metasomatic fluids and the site of deposition of removed material is speculated upon.