The amphibolites belong to the quartz-albite-epidote-almandine subfacies of the greenschist facies. Some are massive and show relict igneous textures, while others are schistose. Twenty-seven new analyses indicate trends of variation of chemical composition sirnilar to those of the Karroo dolerites, from which it is concluded that the arnphibolites are of igneous origin. The oxidation state of the schistose amphibolites is significantly higher than that of the massive amphibolites. If this difference was included during metarnorphism, it was probably due to differences in the dynarnic element of metarnorphism; if it be inherited, then it is most probable that the schistose arnphibolites were once mainly basic lavas and that the massive amphibolites were largely basic intrusives.