Abstract

Geochemical investigations of a series of boreholes drilled perpendicular to the plunge of two mineralized pipes has revealed the presence of well-developed halos of tracer elements. This is important for underground exploration as efforts to date have failed to identify any obvious structural features which could assist with the localization of such mineralized pipes.It is suggested that the mineralized aqueous fluids that gave rise to the mineralization separated from the interstitial liquid very late in the crystallization history of a compositionally zoned granite pluton. The fluids percolated upward through the unconsolidated granite and caused metasomatic alteration of the Bobbejaankop and Lease Granites. As pores of the crystallizing rocks gradually diminished because of cooling, differential upward streaming of fluids set in which was dictated largely by lateral variations in the pore spaces and incipient fracturing of the rock. This developed into a system of well-defined, but irregularly shaped, conduits where the original components of the granite were extensively altered and replaced, and where crystallization of tourmaline, cassiterite, fluorite, and other typical pipe minerals took place.

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