Archaean to Proterozoic ultramafic igneous intrusions and granite masses associated with the Yarlbrinda Shear Zone, which are interpreted as being potential hosts for gold, nickel, chromium and platinum group elements, were the targets of exploration in two separate areas located 10 km and 25 km south of Tarcoola. Initial regional and detailed calcrete sampling, and reprocessing of SAEI aeromagnetic data, delineated four prospects which were tested by RAB, aircore and open hole percussion drilling (311 holes, total 7705 m). The drillholes intersected a number of mafic/ultramafic lithologies which appear to represent a layered intrusive complex, and include komatiites exhibiting spinifex textures. These lithologies may be equivalents of the Lake Harris Komatiite. However, while their inherent Ni values are of the same order, their Cr and PGE contents are significantly higher.