A small licence area centred approximately 70 km north-northwest of Oodnadatta is being explored for possible economic buried IOCG type mineralisation that may have formed in the wholly concealed, almost unknown basement rocks there. Interest is focussed on the Mount Sarah regional gravity high, an oval-shaped eight milligal magnitude gravity anomaly of unusually large, 5.5 km x 3.5 km extent. The nearest previous drilling in the Mount Sarah region took place many kilometres away, and did not reach depths sufficient to encounter the inferred Proterozoic age top-of-basement rocks. In the licensee's exploration model, the Mount Sarah prospect sits proximal to the western edge of a zone of interpreted crustal attenuation that now separates the Gawler Craton from the Mount Isa Province. It is thought that the older Proterozoic basement in this area has possibly been subjected to granite emplacement and high heat flows. A combination of the prospect's location on the G2 Lineament structural corridor, the probable existence of many geological factors conducive to the formation of large hydrothermal mineralised systems, and the presence of a large gravity and magnetic anomaly, in the licensee's view all point to a compelling frontier terrane drill target. Late in 2015, the licensee commissioned consultant geophysicist Graham Jenke from Southern Geoscience to make a detailed review of previous exploration work done in the broader Oodnadatta region, which was found to have included several phases of regional and local geophysical surveying, including magnetic, radiometric and gravity surveys. Data from these surveys was procured and examined to try to estimate the drilling depth required to reach basement at Mount Sarah. Indications were that it could be around 500 m, which in the context of the setting of recent IOCG finds like the Carrapateena deposit represented a valid and achievable target. In November 2015, operator of the subject EL 5634 the Macallum Group Limited (MGL) acquired an infill gravity survey on the Mount Sarah anomaly to complement Caldera Resources' semi-detailed partial gravity coverage of November-December 2007 (for that earlier survey, see EL 3924 reports held in Env 11662). The new survey's aim was to better determine an appropriate value of Bouguer density for applying in raw gravity data corrections, and thereby to more accurately define the location of the peak gravity response, which MGL hoped could represent haematite alteration and associated base and precious metals. The Mount Sarah infill survey consisted of 509 stations read along 14 east-west grid lines and 2 traverses along tracks, with a 400 m grid line spacing and station intervals of 100 or 200 m. Following completion of this survey, Graham Jenke was engaged by MGL to interpret the new gravity data. Two gravity peaks were defined, within the anomaly footprint that now covered ~26 square km. Plans were made to drill two exploratory holes to test both peaks, MS003 targeting the westernmost one and MS004 the easternmost. But due to financial constraints imposed on the licensee at this time, he decided that only one hole could be drilled to test the Mount Sarah gravity high. The MS004 location was selected as the first to be drilled, mainly due to ease of access. The hole construction plan involved drilling an approximately 500 m deep vertical rotary mud precollar through the Great Artesian Basin (GAB) cover sediments, and switching to drilling a 300 m long HQ diamond cored tail once within dry Proterozoic basement rocks. To assist with funding this undertaking, MGL completed a PACE Discovery Drilling Programme 2016 Project Proposal Form and lodged it with the Department of State Development (DSD) for appraisal, during April 2016. In August 2016 DSD wrote back to the company, approving the proposal as Year 9 collaborative drilling Project DPY9-05, which would receive subsidy funding to the level of $75,000. Issues then arose in obtaining an acceptable drilling cost quote from an experienced drilling contractor who would be able to commit to completing drilling within the original timeframe specified for availability of PACE Discovery Drilling Program 2016 subsidy funds. This meant that the drilling program had to be placed on hold. Follow-up correspondence with DSD representatives led to a variation agreement being drafted, executed and returned to MGL on 5/5/2017, allowing for the combined drilling and reporting execution deadline to be extended to the end of September 2017. Vertical drillhole MS004 spudded on 5/7/2017 and was completed to a total depth of 811.3 m on 20/7/2017. Watson Drilling were the chosen drilling contractor, utilising their rig WDR06, a Bourne Drill 1000 machine, which had already been doing other work in the Far North. The hole was drilled on a double shift, starting as a rotary mud precollar carried down to a depth of 318.4 m. HQ diamond core drilling commenced at this depth and was continued down to 719.6 m. Because the drill rig had been struggling to pull the HQ core equipment from below ~650 m depth, the decision was made at this point to case off the hole and diamond drill NQ core from there onwards. This lesser sized hole was then drilled on to TD. The original drilling plan was to drill through the entire GAB sedimentary sequence with a rotary mud PCD bit. Based on data from the nearest seismic survey line that had been shot 6 km away to the south-west in 1962 by the SA Mines Department, the GAB sedimentary sequence at Mount Sarah had been interpreted to be 500 m thick. However, extensive zones of generally hard and broken ground were encountered from approximately 270 m depth, and contributed to very slow drilling advance rates, with the last rotary mud drilling 12-hour shift only achieving 17 m of advance. In an effort to increase drilling advance rates and to be able to penetrate the hard units (quartzite), the decision was made when at 318.4 m depth to change over to diamond drilling methods. Thereafter the drilling advance rates did improve, but persistent zones of broken ground and water loss continued to present drilling challenges until the end of the hole was reached. Over 1 million litres of water had to be carted to the drill site to maintain sufficient downhole circulation so that the diamond drilling could be completed. Intervals of laminated, fine grained sediments such as siltstone tended to be very broken, slowing down diamond drilling progress. Upon commencing the hole completion stage, MS004 had sacrificial HWT casing left in it down to a depth of 318.22 m. The hole was pressure grouted to surface before the drill rig moved off site. Hole MS004 is interpreted by MGL geologists to have intersected the GAB sediments' basal unconformable contact with Neoproterozoic basement at a depth of 461 m. The (later zircon LA-ICPMS dated) Neoproterozoic units penetrated below 461 m as far as the hole's total depth consist of a thick sedimentary sequence of variably polymict brecciated, pervasively haematite / chlorite / silica / carbonate / sericite - altered metasediments. The amount of alteration present suggests that it is of hydrothermal origin. The location of the igneous rocks which presumably generated the metasomatic fluids responsible for the alteration is currently unknown. All of the basement drill core is variably vughy, pitted and porous. The combination of the strong gravity high and the alteration, brecciation and vughy nature of the metasedimentary drill core suggests that hole MS004 may have intersected a diatreme. The extent of development of haematite alteration likely to exist at Mount Sarah may be enough to explain the targeted gravity high, but there remains the possibility that the gravity anomaly's source has yet to be encountered at greater depth. Rock magnetic susceptibility, electrical conductivity and K/Th/U radiation spectrometric hand-held instrumental scans were made on all of the drill core to save on the significant cost that would be associated with mobilising specialist downhole wireline logging equipment to the drill site. Besides the detailed lithological / mineralogical / rock textural log, plus photographs which were taken of all the trayed core pieces, a basic geotechnical log was completed for all of the drill core. The information collected consists of recovery per core run, fractures per core run, and rock strength per core run assessed by scratching the core with a tungsten tipped scribe. Should further drilling and prospect evaluation work be undertaken in the future, MGL considers that these data will prove useful. For geochemical reconnaissance purposes, one 120 second duration spot assay reading was taken at the approximate mid-point of each metre of trayed drill core using a Niton XL3t Ultra hand held XRF spectrochemical analyser (however, it must be noted that in some of the breccia units seen in the core, some of the XRF readings may have been taken on a clast, with the results obtained being more representative of the clast composition as opposed to the general rock composition within the metre range). Elements which recorded anomalous values >=10 x average Earth crustal abundance were plotted individually versus hole depth to try to determine variation trends. To help save on project costs, and given that preliminary Niton XRF drill core geochemical scan results were seen to be generally low to weakly anomalous, besides which no visible base or precious metal sulphides were observed (and otherwise generally low levels of sulphides exist in the drill core), only 20 core samples were taken for laboratory assaying of 64 elements, including fluorine, plus rock specific gravity determination. In these samples, certain pathfinder elements mentioned below returned weakly anomalous values that may be indicative of rocks located on the margins of a hydrothermal alteration system. Eighteen basement drill core samples were sent to consultant Ian Pontifex for petrographic examination and classification. He concluded that besides them having epithermal system properties which could denote a diatreme-related genesis, they also exhibited similarities to rocks affected by diapirism as found in the Mount Painter Province, where examples include masses of reconstituted carbonate and sedimentary rock units and local blocks of granitoid. Thirteen approximately match box size samples of the MS004 basement drill core were selected for zircon picking and age dating, which was contracted to CODES at the University of Tasmania. The LA-ICPMS U/Pb dating method was used on five samples containing enough zircon grains to permit attempting statistically meaningful age dating. The stratigraphically youngest sample came from 457.2 m depth, i.e. from above the interpreted basement / cover unconformity. The youngest detrital zircon age derived from this sample is 423 Ma, however, this analysis result is discordant and its geological significance is uncertain. It is possible that this particular sedimentary rock unit may have formed at a later time, i.e. post - middle Ordovician. The other four samples were taken from between 491.8 m and 794.36 m depth, and yielded youngest zircon ages in the range 601 Ma to 896 Ma, thus falling within the Neoproterozoic age bracket (~1 billion years ago to 541 Ma). Five-metre composite drill cuttings samples of the rotary mud precollared section of MS004 are presently being retained by the licensee, along with the drill core, in storage at Mount Sarah Station. In due course, according to the provisions of the SA Minerals Regulatory Guidelines, these samples will be furnished to the South Australia Drill Core Reference Library for public access. Before hole MS004 was drilled, the interpreted most likely source of the Mount Sarah gravity high was a palaeotopographic high. But afterwards, awareness of the nature of the bedrock alteration and of the presence of anomalous concentrations of pathfinder elements such as As, Bi, Ca, F, In, K, Li, Mg, Mn, S, Sb, Se, Te and U (above 10 x normal crustal abundance) has meant that these could account for the large gravity high and serve to suggest that a hydrothermal mineral system could be present. However, it is also plausible that the gravity high is yet to be accounted for, with further work required to resolve this. It is also possible that the altered and brecciated Neoproterozoic sediments intersected below 461 m are signs that a Mesoproterozoic IOCG system is present, but at great depth.