.................................................................................................................................... iv Uittreksel ................................................................................................................................... vi List of Figures ............................................................................................................................ x List of tables ........................................................................................................................... xiii Chapter 1: Introduction .......................................................................................................... 1 Chapter 2: Geological setting and locality............................................................................. 4 2.1. Stratigraphy of the Barberton Granite Greenstone Belt (BGGT) ............................... 4 2.2. Development of the BGGT ......................................................................................... 7 2.3. TTGs from the BGGT ................................................................................................. 8 2.4. Geochemistry and petrogenesis of ~3.45 TTGs from the BGGT ............................... 9 2.5. Previous work on the Felsic volcanic rocks of the H6 .............................................. 11 Chapter 3: Analytical Methods ............................................................................................ 19 3.1. Sample preparation and X-ray fluorescence (XRF) methods ................................... 19 3.2. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis of trace elements techniques used .................................................................................................................... 22 3.3. X-Ray Diffraction (XRD) analysis ........................................................................... 23 3.4. Scanning electron Microscope (SEM) techniques used ............................................ 23 Chapter 4: Field descriptions of the H6 member ................................................................. 24 Chapter 5: Petrography ........................................................................................................ 29 5.1. General statements .................................................................................................... 29 5.2. Preserved magmatic textures ..................................................................................... 29 5.3. Metamorphic textures ................................................................................................ 30 5.4. Textural features produced by Alteration.................................................................. 32 Chapter 6: Mineralogy of the felsic igneous rocks .............................................................. 34 6.1. Relict K-spar in altered grains ................................................................................... 34 6.2. XRD analyses of whole rock powders ...................................................................... 36 Chapter 7: Geochemistry ..................................................................................................... 38 7.1. Major-element chemistry .......................................................................................... 38 7.1.1. Trace element chemistry .................................................................................... 38 7.2. Geochemical variation as a function of depth beneath the BRC ............................... 45 Chapter 8: Discussion .......................................................................................................... 47 Stellenbosch University http://scholar.sun.ac.za