A north-northwest trending basement high or horst-like structure mapped in the subsurface at Yadlamalka, located about 50 km north of Port Augusta, which was indicated by magnetic and gravity data to lie at a depth of about 200 m to 600 m close to the eastern edge of the Torrens Hinge Zone, has been explored for possible Mount Gunson type sediment-hosted copper mineralisation in Adelaidean successions, as well as for possible Carrapateena / Punt Hill style IOCGU mineralisation in Palaeoproterozoic basement. To this end, a company proposal for a PACE Initiative funds subsidy, to aid in drill testing an interpreted westward-directed thrust that has uplifted the target Adelaidean and Palaeoproterozoic rocks, was accepted by PIRSA as project DPY5-43 late in 2007. In preparation for the drilling work, Lincoln Minerals acquired detailed ground gravity and magnetic surveys late in 2007 to gain better resolution of the horst block structure formed on the eastern side of the thrust fault. Three ground magnetic traverses were laid out across the structure, yielding data that confirmed its outline in greater detail, while 1664 gravity stations were read at 100 m intervals along lines spaced 800 m apart, and clearly showed a negative, linear minus 0.7 to minus 1.5 mGal residual Bouguer anomaly that virtually coincides with a positive residual magnetic anomaly about 1000 nT above regional background, and 130-150 nT above local background. However, modelling of this new potential field geophysical data was unable to distinguish between two separate best-fit scenarios, in one of which the basement had been involved in thrusting, or alternatively, one where the Adelaidean succession had become detached from the basement during such thrust uplift. During June 2008, in unrelated work, Geoscience Australia (GA) acquired regional deep crustal seismic reflection data spanning the southern Arrowie Basin along a transect that crossed EL 3563. When the processed data for Line 08GA-A1 was released, Lincoln Minerals was able to use it as a window giving information on the thickness of lithologic units and geological structures that might be producing its Yadlamalka magnetic and gravity anomalies. GA's interpretation of the seismic data concluded that the Yadlamalka Thrust had developed on a basal Adelaidean surface, meaning that no crystalline basement was involved in thrusting (cf. Carr et al., 2010). For Lincoln Minerals this conceptual outcome excluded any chance of doing effective exploration of pre-Adelaidean rocks in the vicinity of the thrust, as it meant that they would be at depths exceeding 3 km. In order to test the exploration model and the mineral potential of the interpreted subcropping thrust structure, three diamond drillholes were planned: 1. A 1000 m deep hole into the apex of the thrust, to test for the presence of sediment-hosted copper in the Adelaidean succession and to try to reach any unknown uplifted portions of the Palaeoproterozoic basement, which potentially might host IOCGU mineralisation; 2. A 500 m deep hole within the hanging wall of the inferred thrust-fold, to further test for sediment-hosted copper mineralisation; and 3. A 500 m deep hole penetrating into the footwall west of the target geophysical anomalies, to test for mineralisation which may have been primarily controlled by the thrust itself. Lincoln Minerals was granted $100,000 from the Year 5 budget of PIRSA's Plan for Accelerating Exploration (PACE) to assist with the cost of the drilling. In the end, only one hole was drilled, the one that was planned to test the first objective described above, the programme being truncated owing to the slow rate of drilling and the costs incurred thereby. After delays in obtaining a suitable drilling rig, rotary mud precollared vertical diamond drillhole TKDH1 was spudded on 12/9/2008 by contractor Downer EDI Mining Pty Ltd, and then abandoned at 129 m depth due to the bit becoming bogged in loose sand, before a twinned hole TKDH1a was then drilled 10 m away to the south, successfully reaching TD 1002.3 m and being completed on 13/11/2008. This hole encountered 197.8 m of Paleogene-Quaternary clays and sands and 804.1 m of Adelaidean metasediments. All diamond coring was done at NQ diameter, commencing at a depth of 197.8 m. The drillhole location lies about 1.5 km south of the GA Arrowie Basin seismic transect. The cored Adelaidean succession began at 213.3 m depth with red-brown sandstones of the Backy Point Formation, that are interlayered with weathered basalts. The Beda Volcanics proper were penetrated at 354.5 m depth. The Backy Point Formation and Beda Volcanics are thrust over younger Adelaidean units at 633.9 m depth, the fault plane being marked by a cataclasite about 3 m thick. Immediately below the thrust there is a cored interval of about 38 m thickness of Brachina Formation overlying Elatina Formation, in which the hole finished. The alpha-angles of bedding are generally around 40°-50° above the thrust, and increase to 75°-90° from about 20 m below the thrust. The top of the thrust has an alpha-angle of 30°. The hanging wall block contains hydrothermal breccias, moderate to intense veining, and stockworks of quartz-carbonate-chlorite ± epidote ± hematite ± chalcopyrite in basalts. Veins are generally a few millimetres wide, but swell up to 10 cm wide in places. Chalcopyrite also occurs as blebs in the basalt. The foot-wall block is generally less altered, containing veinlets of quartz and/or carbonate ± sericite. Silica and carbonate alteration are common in the top 50 m of the hanging wall block. The orientation of veins with respect to core is variable, but alpha-angles are commonly around 40° in the hanging wall basalts. Despite abundant visual signs of fluid flow, alteration, and anomalous copper content, no significant mineralisation was encountered by TKDH1a, so no core samples were taken for assaying. The drilling showed, however, that the coincident gravity and magnetic anomalies are sourced in the hanging wall block of the westwards-directed thrust. It is possible that the drillhole was placed too close to the toe of the thrust as, from this single drillhole, it was not possible to determine whether the thrusting involved basement or not. Therefore, neither variant of the Yadlamalka Horst exploration model could be excluded. No further field work was undertaken during the last 20 months of licence tenure, before a decision was made to allow it to lapse at the end of Year 4. Although the region of the Yadlamalka Horst is still regarded as holding potential for finding Adelaidean sediment-hosted copper mineralisation, it is thought that the prospectivity for economic IOCG mineralisation is now negligible owing to the great depth there of the pre-Adelaidean basement.