On the Relationship of the Vredefort Granite to the Witwatersrand System

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Abstract
Introduction. The Vredefort Granite has always been considered as a member of that ‘old granite’ group which throughout the Transvaal and the Orange Free State is found emerging from beneath the Witwatersrand Beds. Although mineralogical differences could be observed from area to area, this grouping together was a matter of convenience, dictated by their stratigraphical position. The first attempt to indicate the extent of the granite outcrop with any pretence of accuracy was made by Dr. F. H. Hatch in his Geological Map of the Southern Transvaal, published in 1897. With regard to the encircling sedimentary rocks, it is clear from the stratigraphical and lithological evidence that they are of Witwatersrand age—the southern rim of the basin of Witwatersrand rocks, the northern rim of which crops out along the Rand. Several geologists who have visited the Vredefort area appear to have been struck by indications pointing to the intrusive nature of the granite into the Witwatersrand Beds. Thus Dr. Molengraaff in 1903, arguing from the steep dip and overtilting of the surrounding strata, the occurrence in them of small enclosures of granite at some distance from the main outcrop, and the evidence of contact-metamorphism in the adjacent beds—particularly the production of corundum—proved it conclusively to his own satisfaction. But, in the following year, he was led to retract his views, on considering evidence collected in the meantime from other parts of the Transvaal as to the non-intrusive relationship of this ‘old granite’ group to the Witwatersrand System. To argue, however,

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