Metasomatism and metallogeny of A-type granites of the Mt Painter–Mt Babbage Inliers, South Australia

The Mount Painter and Mount Babbage Inliers (South Australia) are largely composed of Mesoproterozoic A-type granitoids that intruded marginally older metasediments. Metasomatic activity has had a pronounced influence on the granites in the southerly Mt Painter Inlier. U–Pb dating and Hf isotope ratios of zircons from granites and hyperaluminous rocks show the latter to be heavily metasomatised equivalents of the granitoids. Similar metasomatic processes are likely to have been responsible for the formation of Fe-oxide–U–REE ores. These ores formed more than 1100 Ma after intrusion of the Mesoproterozoic A-type granites, and elemental remobilisation may have been associated with a new phase of granitoid magmatism around 455 Ma. The ferroan and incompatible element-rich nature of A-type granites makes them a suitable source for ores that can be tapped whenever thermal and fluid conditions are favourable.

► A-type granites are prospective sources for mineralisation, even a billion years after emplacement.
► Metasomatism can obscure the identity of igneous rocks beyond recognition.
► Highly resistant minerals like zircons can be used to establish the protolith of metasomatised rocks.