Volcanic rocks — herein informally named the Warraweena volcanics — were encountered during drilling by Newcrest Mining Limited about 35 km northeast of Bourke. Petrological and geochemical characteristics of samples from two of the drill holes suggest that the rocks are of calc–alkaline affinity while samples from a third hole have a within-plate affinity. Identification of these calc–alkaline rocks, in conjunction with aeromagnetic and gravity data for the region, indicates that a northeast-trending fragment of a volcanic arc which extends for about 70 km, may be present in the area beneath Mesozoic and Quaternary cover. Although the ages of these rocks are unknown, an Ordovician age is possible by analogy to the nearby Macquarie Arc and the occurrence of reworked andesitic clasts in rocks of possible Siluro-Devonian age intersected in nearby drill holes. Its older age limit is unconstrained and could be potentially as old as Precambrian. Its younger age is ultimately constrained by overlying sedimentary rocks, interpreted to be the basal part of the Eromanga Basin, which is Jurassic. The presence of volcanic rocks of within-plate, possibly rift-related affinity, could indicate that a later extensional phase affected the arc. If the interpretation of a volcanic arc within the area of Bourke is correct, the mineral potential of the area is substantially upgraded — with the possibility that porphyry-, epithermal/mesothermal vein- and skarn-type mineralisation could be present below cover.