A component with ~6% mantle helium (3He/4He=5--9¿10-7) has been identified in borewaters from the Great Artesian Basin, Australia that is isotopically distinct from previously identified in situ production (3He/4He=1.6¿10-8) and a crustal degassing flux (3He/4He=6.75¿10-8). The occurrence of this component is limited to three identified localities (~20.5 ¿S 144 ¿E; ~25.5 ¿S 146 ¿E; ~27 ¿S 144.5 ¿E) all within the region of high reduced heat flow in eastern Australia. No evidence for a mantle component was apparent in central Australia. This component is most probably the result of continued intrusive volcanism (<1 m.y.) associated with the Cainozoic lava flow fields in the region. Although the volcanic activity has no present-day surface manifestation, its mantle helium was probably carried to the near-surface by large-scale fluid transport processes in the crust. ¿ American Geophysical Union 1987