/MINERAL EXPLORATION
Successful Field Trials for RoXplorer® Coiled Tubing Drill Rig RoXplorer® coiled tubing drill rig successfully drills consolidated and unconsolidated cover rocks and basement and delivers representative samples DET CRC’s RoXplorer® coiled tubing (CT) drill rig has completed very successful field trials in the consolidated cover rocks of the Gawler Craton (near Port Augusta, South Australia, February –March 2017) and the unconsolidated cover rocks of the Murray Basin (near Horsham, Victoria, May – June 2017). The team has also received the results of assays of samples of the coiled tubing drilling cuttings from the Port Augusta trial and their match to assays of diamond drill core from an adjacent hole is remarkable. It is highly likely that this new technology has opened the Gawler Craton, Murray Basin and similar areas of extensive cover to ‘prospecting drilling’ which will enable progressive vectoring towards concealed mineral deposits using multiple, cheap holes in a single drilling campaign, thereby opening the covered mineral exploration search space.
The Port Augusta Trial site The Port Augusta trial site provided an example of typical, consolidated and lithified Adelaidean cover of the Gawler Craton, including sandstones trending to quartzites 26
and underlying volcanics. The RoXplorer® rig is a hybrid rig, designed for coiled tubing drilling but also capable of drilling with a top drive and conventional drill rods. In the Port Augusta trial the team first drilled in conventional top-drive mode to ~30 m, cased with steel pipe and cemented in the casing. The main hole was then drilled into open formation with a downhole hammer and percussion bit powered by a downhole motor in CT drilling mode. The rig drilled 367 m in four successive 12-hour shifts, for an average of ~92 meters per shift and at an average penetration rate when drilling of ~15 meters per hour. This compares with around 25 meters per shift at an average penetration rate when drilling of ~3 meters per hour diamond drilling in the adjacent hole. The hole was terminated at just over 400 meters depth having intersected the target basalt. According to DET CRC, the results of assays of samples of cuttings from the RoXplorer® Port Augusta trial compare favourably with assays of half-core samples taken at 50 cm intervals from the adjacent diamond hole.
In addition, concentrations of major and trace elements closely match those obtained from the half-core sampling, giving no indication of sample bias or contamination as per the Figure published in the official press release (see: www.detcrc.com.au). Samples from over 400 m depth can be assigned to a depth interval with decimetre accuracy. It is particularly positive that a narrow (~1 m) interval of low grade copper enrichment at the top of the Beda Basalt with visible chalcopyrite in coiled tubing cuttings samples and diamond core is faithfully represented in the assay data from the coiled tubing cuttings. An immediately overlying ~1 m bleached zone of iron depletion at the base of the Tapley Hill Formation is also faithfully represented in the assay data from the cuttings.
The Horsham Trial Site The Horsham trial site provided an example of the even greater challenge presented by unconsolidated Cenozoic cover overlying prospective basement. The cover sequence included a lateral equivalent of the LoxtonParilla sands (~25–40 m) and a basal Coring Magazine #5