Granite production in the Delamerian Orogen, South Australia

Abstract

In the South Australian sector of the Cambro-Ordovician Ross-Delamerian Orogen, granites range in age from Mid-Cambrian to Early Ordovician. Their occurrence is largely confined to deep, Early Cambrian, sediment-filled basins where they are associated with mafic rocks. The syntectonic suites have compositions forming a continuum between I- and S-type granites. After the cessation of convergent deformation at c. 490 Ma an abrupt transition to a bimodal magmatic association of mafic intrusions and felsic granites and volcanic rocks of S- and A-type affinities occured. As exposed on the south coast of Kangaroo Island, S-type granite originated as in situ partial melts of the Early Cambrian sedi..