Of plates, plumes and professors

Abstract

The 100 year history of the Department of Geology at the University of Pretoria involves 7 heads, comprising a cyclical succession of scientists devoted to either “plume geology” or “plate geology”. “Plumes”, large bodies of molten mantle material, impinge upon Earth’s brittle crust, forming surficial flood basalt provinces or large mafic intrusive complexes, like the world-famous Bushveld Igneous Complex. The latter is one of the world’s greatest mineral sources, and has been a research focus of this Department since the 1940’s. “Plates” are the relatively rigid basaltic ocean plates and the thicker and more brittle granitic-gneissic nucleic cratons and larger continents, together forming the upper part of Earth’s lithosphere. The creation of continents occurs through complex processes involving basaltic ocean floor, water and some form of “plate” tectonics. Basalt is thus effectively “the bread of life” of planet Earth and basaltic volcanism is an expression of the inter-relationships between plumes and plates; volcanism is also the source of all water on Earth and water makes possible modern-style plate tectonism, without which the planet and its ecosystems would die (cf. the “Gaia hypothesis”). Such early events formed the Kaapvaal craton upon which Pretoria lies, and on which sedimentary basins developed, accumulating chemical and detrital sediments, particularly those of the Transvaal Supergroup and the Waterberg Group. These were characterized by epeiric seas, fed by braided river complexes which swept episodically across highly weathered and vegetation-free continental landscapes, in concourse with a reducing palaeo-atmosphere. The Department of Geology focuses research into: (1) the geology of the Bushveld Complex and other plume occurrences, within a holistic framework of associated sedimentary basins and crustal evolutionary history (cf. “plates”); (2) applied geology: Engineering, Environmental and Hydrogeology, related to the developmental needs of the country, accentuating the economic core within Gauteng, and natural hazards research; (3) Mineralogy and Applied Mineralogy, with an emphasis on Bushveld mineralogy and precious metal “fingerprinting