Hf isotopic evidence for a cogenetic magma source for the Bushveld Complex and associated felsic magmas

Here, we test the hypothesis that the rhyolitic lavas of the Rooiberg Group and granophyres associated with the roof of the Bushveld Complex are differentiation products of Bushveld-age mafic liquids. We present Lu-Hf isotopic compositions in zircons from roof rocks that have been interpreted to represent thermally metamorphosed and remelted Rooiberg Group lavas and from granophyres interpreted to be differentiation products of the cumulate rocks that make up the Bushveld Complex. All of these rocks were found to possess εHf (2.06 Ga) statistically indistinguishable from the intrusion-wide average εHf (2.06 Ga) value of − 8.6 ± 1.2 of the Bushveld Complex. Our results, combined with chronologic and field relations, suggest that the felsic rocks were generated by fractional crystallization of Bushveld mafic liquids, including those that gave rise to the cumulate rocks of the Bushveld Complex.