Exploration for possible basement-hosted iron ore within an area centred approximately 45 km east-northeast of Lock has consisted only of the acquisition of semi-detailed gravity data. The licence ground lies just to the north of the interpreted block-faulted northern edge of the Polda Basin, a large trough structure (failed continental rift zone) which has remained tectonically active from the Cambrian until the mid-Tertiary. A ground gravity survey was performed for Centrex during August 2009 in four separate areas where access was permitted, with a total of 1599 stations read at 40 m intervals along 23 east-west lines spaced 200 m apart. Examination of the resulting data did not reveal any anomalies deemed worthy of drill testing.