The Wonaminta Block is bounded on its eastern and western margins by Lower Cambrian or upper Vendian intrusive and extrusive igneous rocks. The extrusive rocks include pillow lavas. Low‐grade metamorphism has not influenced the distribution of P2O3, Zr, Y, and Nb, but remobilization of Ti has occurred in rocks containing Ti within the oxide phases rather than in the silicate phases. Immobile trace‐element discrimination techniques indicate that the basalts on the western margin of the Wonaminta Block are alkaline whereas those on the eastern margin are tholeiitic. The possibility that these rocks represent petrological variants across an arc system is discussed.