Geology of part of basement inlier north-east of Mt. Compass

Abstract

Basement gneisses, including ‘Houghton Diorite’ type rocks, show evidence of having been subjected to three deformations, the last of which affects the Adelaide Supergroup rocks. Relict sillimanite and sapphirine indicate initial metamorphism to upper amphibolite – granulite facies grade. In an attempt to ascertain the original nature of the ‘Houghton Diorite’ type rocks 12 samples were analysed for major oxides and also V, Cr, Co, Ni, Cu, Nb, Sr, La, Ce and Ba. Comparison of these with those of pertinent known igneous and sedimentary rocks, utilizing multi variant discriminant function analyses, point to a sedimentary origin with a dolomitic shale as parent. Two samples, having both igneous and sedimentary characteristics, are probably the result of local mobilisation of ‘Houghton Diorite’ type rocks.