A Dissertation Submitted to the Faculty of Science; University of the Witwatersrand, Johannesburg; for the Degree of Doctor of Philosophy / A volcanological study of the Onverwacht Group in the southwestern part of the Archaean (-3.5 - 3.2 Ga) Barberton greenstone belt (BGB), South Africa, shows that volcanic extrusion rates of the Komati and Hooggenoeg Formations must have been high to have maintained the degree of submarine sheet flooding that is evident. It is concluded that the volcanic attributes of the Komati and Hooggenoeg Formations are not typical of MOR crust, as has been claimed, but rather closely resemble those of modern oceanic plateaus. The shear-zone-bound basal contact of the Komati Formation suggests that the top of the ancient oceanic plateau was allochthonously emplaced and delaminated from its basal (intrusive) part. (Abbreviation abstract) / AC2017