A group of exploration licences located on the northern margin of the Eucla Basin, and situated north of the Trans Australian Railway, which cover ground extending into the Eocene to Miocene marginal marine depositional hinterland behind the Barton and Ooldea palaeocoastal sand ranges, are being or have recently been explored for economic Tertiary heavy mineral sands (HM) marine placer deposits by Iluka Resources. Historically, the entire so-called Group 4 tenement area has been little explored for minerals. As part of Iluka's HM exploration strategy, all interpreted major stratigraphic / palaeogeomorphic target zones lying therein have been investigated by regional reconnaissance exploratory drilling.The most promising exploration result obtained so far in the Group 4 tenement area was the discovery of the Thar prospect in 2010 in the central northern part of the area, where the present-day Barton scarp veers southwards towards the continental margin. Thar lies exactly above a significant ridge of Gawler Craton bedrock which pierces the thick pre-Tertiary Officer Basin sediments and has formed a HM trap. A drill campaign conducted by Iluka late in 2011 confirmed that the northern and eastern extremities of this prospect have limited development of HM strandings, and in view of that result, Thar has been interpreted as having been deposited within a lacustrine environment, and accordingly does not present strong potential for discovering significant HM accumulations. Since the Group 4 north area’s remote location and distance from any transport infrastructure mean that any mineral sands which may exist there will carry a significant transport penalty, further discovery of a significant grade/size of deposit is required to absorb the extra production cost. The subject tenement major portion now being relinquished has been deemed unsuitable terrain for finding a mineable HM deposit: no exploratory drilling was done within it, because most of its surface is covered by a large lake. To date, 83 vertical aircore holes for a total of 3120 m have been drilled in the retained portion of EL 4334, with 196 drill cuttings samples sent for HM assay. The best mineralised intercept was made in hole TH0192 (3 m @ 4.6% HM from 43 m depth). This drillhole is interpreted to have intersected part of the eastern flank of the Thar deposit.