The distribution and main geologic features of discordant bodies of iron-rich ultramafic pegmatite in the Bushveld complex.

Discordant bodies of Fe-rich ultramafic pegmatite are widespread in the complex and are an integral component of the layered sequence. They are postcumulus rocks of true pegmatitic texture, and are divided into silicate (hortonolite and clinopyroxene) and Fe-Ti oxide varieties. Their mineralogy is stratigraphically dependent so that silicate varieties give way upwards through mixed bodies to oxide varieties, and there is a preferential association with anorthosite. They are most abundant in faulted and fractured regions of the complex. The pegmatitic fluids were derived from the crystallizing cumulate pile. Emplacement was by intrusion and replacement. Platinum-group elements occur only by inheritance from replaced layer-suite rocks.-G.J.N.