The local occurrence of sillimanite in the Cambrian Gula Schist Group of the Trondheim region is discussed. Potash feldspar is common in these sillimanite-bearing rocks but garnet, kyanite and staurolite, quite widespread elsewhere in this region, are significantly absent. Textural features indicate that most of the sillimanite crystallized largely at the expense of biotite during the first of three deformation episodes, with some growth continuing into the immediate post-F1 static period. Reactions are suggested to account for the mineral paragenesis in these rocks which appear to be localized representatives of the highest temperature sub-facies of the almandine-amphibolite facies of regional metamorphism.
On the occurance of sillimanite in the Gula Schist Group, Trondheim Region