The Cambro-Ordovician basement underlying Murray Basin sediments in the Cooke Plains and Coomandook areas was sampled by a reverse circulation drilling programme as part of the South Australian Exploration Initiative. Greenschist to low amphibolite grade metasediments and underlying mafic metavolcanic rocks were intersected, and anomalous levels of zinc, copper, lead and gold were found in many drillholes. Visible zinc and copper mineralisation occurred within adjacent meta-limestone and para-amphibolite units in drillhole MOO 24. The metavolcanics are part of the mafic igneous rock suites of the western Tasman Foldbelt System, and are probably equivalent to the Truro Volcanics. The metasediments are likely to belong to the early Cambrian Normanville Group. The sampled meta-igneous rock types range in composition from basalt to andesite, and have either within-plate or mid ocean ridge type basalt geochemistry. Locating such extensive base metal anomalies, mineralisation and host basic to intermediate volcanic rocks within ?Cambrian metasediments has considerably enhanced the prospectivity of the basement to the Murray Basin in this region.