Exploratory drilling carried out by BHP Billiton (BHPB) during the 2009-10 project reporting year took place at six prospects thought to have good IOCG mineralisation potential, based in part on earlier drilling results and also on refined target models generated by the ongoing interpretation of aeromagnetic and gravity data, in particular data from the company's 2006 Falcon airborne gravity gradiometer survey. Recent advances in geophysical data processing techniques such as the use of constrained inversions and solid earth modelling had enabled a more confident recognition of deeper targets, supported by inputs from improved electromagnetic survey methods such as MIMDAS and AMT. During the period January to November 2010, 10 vertical or predominantly steeply inclined, RC precollared diamond drillholes were completed on EL 3713 only for a total penetration of 8493.4 m, including 2203 m of HQ coring and 4216 m of NQ coring. All of the holes successfully reached or exceeded their programmed depths. The work yielded promising results from the Wirrda Well prospect, with mineralisation intersected in all three holes (WRD31, 34 and 35) put in there, and BHPB decided to carry out further drilling at this prospect in 2011. But drilling results obtained from the other five prospects were disappointing, and their perceived IOCG mineral potential was therefore downgraded. The south-westwards inclined diamond drillhole WRD34, completed to TD 1180.67 m at the centre of the northern gravity high at Wirrda Well on 1/10/2010, produced the best mineralised intercepts that had been seen to date on this prospect. It encountered a complex sequence of variably haematised megacrystic granite and brecciated granite that had been intruded in the mid-section by finer grained variably chloritised and haematised felsic intrusives. Mineralisation seen in the drill core was described as follows: • Trace to very weak chalcocite in granite (in massive haematite zones) from ~496 to ~573 m • a thin rich bornite (5+%) zone in massive haematite at 602.8 to 606.3 m • significant chalcopyrite intersections from ~606 m to 816 m, varying from trace to ½% chalcopyrite in much of the granites and felsic volcanics, to higher concentrations of at least several % and sometimes 5-15% chalcopyrite in most of the massive haematite or magnetite intervals • Trace chalcopyrite and pyrite from 816-1020 m, increasing to an estimated 0.3% Cu in small localised intervals of sulphides • Chalcopyrite and pyrite grading from 3-5% Cu between 1020-1024 m • Strong bornite mineralisation in a thin massive haematite interval from 1039-1042 m. The Wirda Well drill core assay values returned from holes 33 and 34 suggested to BHPB that not all of the copper mineralisation corresponds to the gravity high footprint, but may extend beyond it; also, from the observed distribution of bornite, it appeared that some of the better grade copper mineralisation occurs quite deeply, at >1000 m. The exploratory drilling campaign at Wirrda Well prospect was continued by BHPB during 2010-2011, when another 8 steeply inclined holes (WRD32, 33 plus WRD36 through 44 and 4 extra hole re-drills) were completed for a total penetration of 11,916 m, which included 9547.47 m of diamond coring. To reduce costs, all attempted drillholes initially had a rotary percussion precollar taken to as deep as possible – generally to the depth at which excessive groundwater influx limited the hammer bit’s effectiveness. Significant progress was made in the reporting period in improving the depth penetration of the rotary hammer (extra booster, different hammer): by the end of the reporting period the drilling contractors were successful in drilling rotary percussion precollars to ~400 m depth. The rotary hammer drilling method was followed by HQ diamond coring through the remainder of the cover sequence and generally about 10-15 m into crystalline basement (considerably more where the basement was weathered or fractured), followed in turn by NQ2 diamond coring to the end of hole. In other work, 26 of WMC's 28 vertical diamond cored holes drilled at Wirrda Well between 1980 and 1990 were relogged and resampled by BHPB to match the requirements of their corporate geoscientific database; the drill cores were also re-photographed and had petrophysical measurements made on them at 1 m intervals. Most of the prospect area drill collar locations were professionally surveyed by contractors in March 2011, using an RTK system for maximum positional accuracy. Likewise, 3 Minotaur Exploration vertical or inclined diamond cored holes completed at Wirrda Well in 2007-2008 (WRD28 - WRD30) were relogged and surveyed. BHPB is mindful that aboriginal heritage surveys, and probably archaeological surveys, will continue to be a significant element of the Stuart Shelf Project work program – in particular in the area of recent focus around Coorlay Claypan. Consequently it is seen as imperative that BHPB continue to negotiate with the local indigenous peoples' groups to gain drill site clearances at the Wirrda Well prospect, and/or to seek to gain heritage clearance over the broader target area. The encouraging drilling results already obtained at Wirrda Well were followed up during the 2011-2012 project year, when an additional 12 steeply inclined diamond holes for 11,008.58 m were completed on EL 3713/4904 only (including 2877.45 m of RC percussion precollar drilling). Specific drill targets were generated by interpretation of aeromagnetic and gravity data (in particular the new 250 m x 500 m grid ground gravity survey completed in December 2011), and through preliminary and ongoing interpretation of drilling data. Two infill ground gravity surveys were undertaken for BHBP by Daishsat during December 2011 and January 2012, at the Wirrda Well and Oak Dam prospects respectively. For the former, 242 stations were read at 250 m intervals along N-S grid lines spaced 500 m apart. For the latter, 354 stations were read at 250 m intervals along N-S grid lines spaced 250 and 500 m apart. The Oak Dam gravity coverage was curtailed by BHBP for logistical reasons, but will probably be continued at a later date. In February 2012, geophysical consultant Jim Hanneson provided BHBP with a revised set of images for the gravity anomaly at Bolton Ridge prospect, after he had re-levelled and reprocessed the original 1979 gravity survey data using modern GPS rather than barometric-derived station elevations, plus an absolute gravity correction that was based on the new detailed gravity data from Wirrda Well, to produce more coherent gravity maps. Bolton Ridge is a southward bulge in the Horn Ridge gravity high that goes eastwards from BHPB’s Acropolis prospect in SW EL 4904 to just north of Wirrda Well, and then swings northward to Olympic Dam. The results from exploratory holes completed at Wirrda Well over the period October 2010 to April 2012 have been assessed by BHBP as being generally encouraging; accordingly, based on ongoing interpretation of the expanding prospect data set (geological logging, geochemistry, surface and downhole geophysics), the Wirrda Well area will remain an ongoing focus of exploration. Drilling on EL 4904 was halted in April 2012. BHP is in the process of acquiring additional [existing or subject to current third party ELA assessment] tenements in the eastern Gawler Craton, and it is to be hoped that when these tenements have been secured, exploration will be expanded, starting with ground (and airborne?) geophysics, followed by drilling on a broader more regional scale (while still maintaining an emphasis on Wirrda Well appraisal). No new on-ground work was planned or undertaken during the 2012-2013 project year. A review of existing targets and data was undertaken and Wirrda Well, located in EL 4904, was still deemed to be the priority target – although it was thought that targets with known mineralisation such as Island Dam warrant further exploration and evaluation. During the 2013-2014 project year, a preliminary 3D seismic derisking study was conducted at Wirrda Well in May 2014. Average seismic velocity and density were measured on representative lithologies seen in drill cores recovered from five holes there, to use in algorithms to calculate the rocks' acoustic impedance values and to compute the theoretical seismic response of a conceptual geological model (or geological cross section). The type of response found will determine whether making a 3D seismic survey of the prospect would be effective in defining key aspects of the subsurface geology. Stored downhole samples from four Acropolis prospect drillholes with >1% Cu values in historic assay results were chosen for re-assay with the modern day assay suite, the aim being to try to determine the direction towards any higher grade mineralised zone, and also to identify if any shallower mineralised zone(s) exist. During the 2014-2015 project year, as part of the 3D seismic derisking study at Wirrda Well, some advance theoretical seismic modelling was performed. Computer 3D density models were created for two different geological scenarios, with shells of constant density at intervals of 0.1 gm/cc. The models were run in two directions, E-W and N-S, to predict a more realistic outcome for the planned seismic survey. They confirmed that doing reflection seismic acquisition will map the distribution of density, which will be primarily related to the distribution of iron oxides, including faulted offsets thereto. The modelling also informed the design of a seismic reflection survey source and detector array which should give the most successful results in the field. Re-assaying of the Acropolis prospect stored historic drill cores was completed. Cores from 15 holes were given metric markings before being photographed, cut and assayed (5059 samples taken). Concentrations of 63 elements including REE were determined using 4 acid digest ICP/MS and ICP/OES methods. Magnetic susceptibility and SG measurements were also made of the various formations and lithologies present. Using the new petrophysical dataset, forward modelling for Acropolis was undertaken in June 2015 by Jim Hanneson to try to determine the most prospective area for hosting a haematite body. It was planned to conduct a 3D seismic survey at North Wirrda Well, but due to cost pressures this work was postponed for a year. During the 2015-2016 project year, a 3D IP and magnetotelluric (MIMDAS) survey was conducted at Phillip’s Ridge and Snake Gully in November-December 2015. The survey was conducted in blocks, with each block having a centre line with alternating transmitters and receiver electrodes 100 m apart and a receiver line either side with receivers 200 m apart. Each block had a line in common with the neighboring block, with lines 200 m apart. There was a remote station 30 km away, and a remote pit 4 km away for magnetotellurics and telluric cancellation. The IP survey array had a 200 m pole dipole setup, which is equivalent to the maximum depth to which this method can successfully penetrate. There were no issues with aquifers or extremely chargeable layers in the cover sequence, and good quality data were generated. The combined system signals penetrated to 1200 m depth, but no anomalies were identified in the data collected at either prospect, and the geophysical consultants were confident they would have been identified if present. Elsewhere, in May 2016, another 3D IP and magnetotelluric MIMDAS survey was conducted at Tea Tree Dam along lines 400 m apart, but no anomalies were detected. At the large Acropolis prospect located within the WPA orange zone, where restrictions on available work time applied, a 38 line km 2D IP and magnetotelluric MIMDAS survey was conducted along lines 400 m apart, but nothing of interest was revealed here either. Continuation for a sixth year of the denial of land access onto the southern half of the Wirrda Well target (because of a listed aboriginal heritage protection site that covers Wirrda Well Claypan and surrounds, extending in a broad swathe SW to Coorlay Lagoon) remains a major hurdle for exploration, since this prospect is the highest value one within the project. During November 2015, potential field data were used by Archimedes Consulting to map the top of basement topography at Wirrda Well. Energy spectral analysis was applied to a combination of gridded gravity gradiometry and magnetic data. A plot of the logarithm of the radial (spatial) average of the energy spectrum against the radial frequency typically produced a number of linear segments. The slopes of the linear segments correspond to separate depth ensembles, and provided information about the depth of the magnetic or density interfaces (boundaries) present. Separately, a moving window spectrum calculation procedure was used to define and map geological horizons by deriving magnetic or density interface depth estimates that were weighted according to window size. Lastly, automatic curve matching was used on the magnetic data to detect faults and anomaly source bodies with a high magnetic susceptibility. The derived depth to basement model correlated well with logged information from previous drillholes, and the inferred faults also aligned to some interpreted from drillhole data. However, the expectation of being able to confidently identify a breccia pipe at depth at Wirrda Well using magnetic susceptibility filtering did not materialise. Petrophysical and geochemical property measurements were made afresh on 26 more stored drill cores of the company's and Western Mining's former diamond drillholes, to bring these data up to present-day standards. The cores were also slabbed, re-marked and photographed. The new data were then used to update prospect models and also to improve the regional basement interpretation for the Stuart Shelf. After doing this, the main prospects identified over the past 35 years of exploration were re-ranked using the BHPB Copper Exploration Prospectivity Analysis template, a multivariate weights-of-evidence technique which assigns the prospectivity of a particular terrane for containing a deposit of a certain size. Two targets at Acropolis prospect were given a higher ranking than previously, and now require drilling to test their IOCG potential. During the 2016-2017 project year, 2 angled diamond holes (ACD22 – 23) for 1926.2 m were completed at Acropolis South and East, areas that were defined as high potential targets from a regional Copper Exploration target ranking process. To constrain the potential field inversions and interpretations generated for both the regional and prospect scale, a 3D solid earth geological model was created using regional geological datasets, this work was completed by Mira Geoscience. The outcome was a fully integrated approach to interpretation and targeting where gravity and magnetic highs are understood from either a lithological or alteration/mineralisation perspective. Hole ACD22 intersected deeper cover than anticipated, with the Pandurra being thicker than predicted, Gawler Range Volcanics were intersected at 627 m, with brecciated volcanics and weak hematite alteration from 670 m, brecciated granite was intersected at 710 m, with heavy hematite alteration occurring from 743 – 760 m. Brecciated granite with weak hematite alteration and mafic dyke continued until 886 m with Donington Granite until EOH. No anomalous copper mineralisation was recorded, with the hematite alteration being significant as to explain the gravity anomaly target. Hole ACD23 tested a density anomaly and intersected Pandurra to 635 m, where it intersected basement and dolerite dyke interpreted as Gairdner Dyke, bedded clastic facies were intersected between 735 – 767 m with moderate hematite alteration with Gawler Range Volcanics down to 843 m with dolerite to EOH. Neither brecciation nor mineralisation was intersected. A detailed review into the ZTEM system was undertaken to determine the suitability of the system as an exploration targeting tool. The system collects the z-component tipper electromagnetics with frequencies between 30-7020 Hz providing a greater depth of investigation to 1 km. However the conductive Tregolana shale and the depth of cover being too great, it is unlikely that the ZTEM system will be effective tool for exploration on the Stuart Shelf. During the 2017-2018 project year the company undertook a large exploration campaign over the project area. Heritage surveys were completed over five prospect areas; Bills Lookout, Two Yard DAM, Burgoyne Dam, Regional MT, and Oak Dam. Exploration included diamond drilling and geophysical surveys along with the continued work on the 3D solid earth geological model. A ground gravity survey was completed across 5 prospects (Bills Lookout, Oak Dam, Two Yard Dam, Burgoyne Dam and Acropolis), with a total of 6940 stations were collected by Daishsat Geodetic Surveyors between February to April 2018. The survey stations were collected on a 250 x 250 m grid spacing, with a few stations missed due to being within sensitive areas that could not be accessed. Further geophysical surveys were completed, with a regional Magnetotellurics Survey (MT) undertaken across a majority of the Stuart Shelf Project area (606 soundings), and 46 line-km of Induced Polarisation and Magnetotellurics (IP-MT) survey data collected across the Bills Lookout, Two Yard Dam and Burgoyne Dam prospects. The IP-MT 2D surveys were conducted by Geophysocal Resources Services between March to May 2018. The regional MT Survey was completed by Zonge Engineering and Research Organisation between November 2017 to March 2018 and was completed in 2 stages; stage 1 utilised broad band MT, while stage 2 used Audio MT. Drilling was undertaken at Oak Dam, with 2 diamond holes drilled for 2630 m targeting a large gravity anomaly. The drillholes were targeted primarily on the results of the ground gravity survey completed during the reporting period looking for hematite breccia. Hole AD22 (1154 m) intersected a hematite granite breccia interlayered with a strongly sericite altered granite at 920 m. The top 30 m is interpreted as a leached zone that continues into low grade chalcopyrite zone. AD23 (1477 m) intersected basement at 702 m in red hematite breccia with sedimentary layering similar to the hematite core at Olympic Dam, drilling of the hole was reported as on going at the end of the reporting period.