Following the acquisition and interpretation of 435 line km of ground magnetic surveys over selected aeromagnetic anomalies within regions of high magnetic relief on the northern Gawler Craton, 121 reverse circulation holes totalling 8609.25 m were drilled by MESA as part of a regional programme designed to explore for potential iron ore deposits, which was begun in January 1995. 92 of the holes penetrated basement rocks, at depths ranging from 7 m to 127.5 m, revealing a predominantly metasedimentary terrain which has undergone amphibolite facies to granulite facies - grade metamorphism, with occasional felsic igneous intrusions. Magnetite is relatively abundant within the metasedimentary sequence, representing altered former banded iron formations. Several zones of low grade iron ores were outlined within the Coober Pedy Ridge (in holes PHN5, 25 and 67) and Mount Woods Inlier (in holes ENG3, 9, 10, 11 and 12), and potential for high grade iron deposits exists in other areas including Hawks Nest, Sequoia and Peculiar Knob, as well as within a number of aeromagnetic targets not yet drilled. Bedrock sample geochemical analyses recorded a number of slightly anomalous base metal intersections. MESA's regional bedrock drilling on the northern Gawler Craton has provided valuable information on the basement geology which will assist exploration companies to formulate viable exploration models for the area.