Ringenbergs, W. H.2024-05-272024-05-271975https://hdl.handle.net/2440/140945This item is only available electronically.The high grade aluminosilicate bearing schists and gneisses are believed to be due to prograde regional metamorphism to T 600-700oC, P 4-6kb under falling potassium activity. This leads to dealkalisation of K-feldspars and immediately precedes or accompanies the F2 deformation. Shearing also seems an important genetic control. The dominant rock types are subdivided: 1. Aldgate Sandstone Equivalent 2. High Grade (sillimanite) zone Sillimanite Quartz Gneiss Kyanite Quartz Gneiss Muscovite Quartz Gneiss Kyanite Muscovite Kaolinite Shear rocks Schists (coarse) Tremolite marker horizon 3. Kyanite Andalusite zone Sandstones, Marbles, Schists, and Calc-silicate rocks The retrogression of the aluminosilicates took place in two distinct steps. Preceding the F3 deformation and associated with initial stages of thrusting, muscovitisation occurred, producing green muscovites (referred to by Alderman as Damourite) and sericite pods in the high grade schists. Introduction of potassium and water was involved. Following the F3 deformation kaolinisation of sillimanite and K-feldspar occurs. This is a low temperature hydrothermal alteration. X-Ray diffraction studies demonstrate the equivalence of the green muscovite and sericite and show the alteration of sillimanite to kaolinite.enHonours; Geology; prograde metamorphism; andalusite; kyanite; sillimanite; muscovite; calc-silicates; deformation; retrograde metamorphism; kaolinisationThesis