A small area centred approximately 70 km north of Orroroo is being explored for possible buried economic Neoproterozoic stratiform or stratabound epithermal/hydrothermal copper and gold deposits, and for placer gold or magnetite deposits, as well...
A small area centred approximately 70 km north of Orroroo is being explored for possible buried economic Neoproterozoic stratiform or stratabound epithermal/hydrothermal copper and gold deposits, and for placer gold or magnetite deposits, as well as for possible diamondiferous kimberlites. Much of the initial field work was concentrated in the vicinity of the known historic sub-economically copper mineralised Prince Alfred mine, and included ground-based evaluation of magnetic and IP anomalies and prospect scale stream sediment sampling (15 samples) and rock chip sampling (5 samples). It was concluded that the possibility exists for finding sulphide-bearing lode extensions at depth in Neoproterozoic Wilyerpa Formation metasedimentary turbidite gravels buried under alluvial cover to the east and south of the old mine workings. An attempt was made during 2008 to attract Eromanga Uranium as a joint venture partner to help with funding exploratory drilling and ground EM surveying near the Prince Alfred mine, but negotiations proved unsuccessful. Further geological mapping of prospective Burra Group metasediments conducted along strike to the north of the Prince Alfred mine found a previously unreported thin zone of quartz-calcite-chalcopyrite veining within the Tindelpina Shale that runs for ~5 km north-eastwards from the mine lode position, outcropping discontinuously over a 3 to 30 cm width. This horizon lies on the western limb of the Yednalue Anticline, where a number of north-east trending fault/shears disrupt the bedding and appear to be related to minor occurrences of diapiric carbonate breccia. During June 2003, a small, 3 line km ground gravity survey was conducted along two traverses across magnetic anomalies located in the northern part of EL 2847, with readings taken at 100 m station intervals. Following the interpretation of the gravity data, a potential iron oxide - associated copper-gold (IOCG) target was identified in the Hardy's Corner area at the core of the anticline (a ?blind regional thrust fold), where earlier shallow bedrock drilling done by Utah Corp. and BHP Minerals had found anomalous copper levels of up to 500 ppm Cu. After a deal of study and geophysical modelling by the licensee, this target was put forward to PIRSA during 2006 as a greenfields mineral project suitable to drill with the assistance of PACE Initiative Year 3 funds, but the subsidy application was not granted. Late in 2004, geological mapping and petrographic studies of outcrops sampled in the vicinity of magnetic anomaly 293644, which is located ~5 km north-east of Wilcowie Homestead, disclosed the presence of a talc and garnet-rich alteration mineral assemblage within phyllarenites and rudites, which it was surmised could possibly be due to contact metamorphism around a buried ultrabasic intrusion. The highly micaceous texture of some schist clasts seen within the rudites outcropping in the south-western part of the licence area, coupled with the occurrence of talcose and magnesite-bearing sediments, suggested that there could be possible diamondiferous kimberlitic intrusions in the vicinity of the shear system developed on the Yednalue Anticline. Some petrographic, mineralogical and heavy mineral analyses were undertaken to try to detect indications of kimberlite or lamprophyres, but nothing conclusive was found. During 2007, existing geochemical data for the tenement area were reviewed, and as a result of information gaps which were then perceived, stored downhole samples from 19 drillholes were submitted for modern chemical analysis of trace elements, including additional ones to those assayed for by previous explorers, such as gold and rare earth elements. 36 samples were analysed. The magnetic lineament crossing the north-eastern portion of the subject tenement (renewed on 13/2/2007 over the same 75 square km area, as EL 3701) was explored with a detailed airborne helimag survey flown during January 2008, to try to detect subtle magnetic anomalies originating below the Cainozoic cover, that might be associated with historic near-surface copper geochemical anomalies. 892 line km were flown along 100 m spaced east-west lines, with a nominal sensor height of 30 m above the ground. The resulting aeromagnetic data were microlevelled and viewed in various image modes designed to highlight magnetic linears and point anomalies, and three magnetic features were selected for follow-up ground magnetic survey delineation, which was performed late in 2009. Another company's newly drilled hole located 100 m outside the northern boundary of EL 3701 (Copper Range HWSRC01 completed to an inclined TD of 70 m in July 2007), data for which were made open file in 2009, was inspected at the PIRSA Core Library, and magnetic susceptibility measurements were made on the drill cuttings to help calibrate models of the Matt Whim magnetic lineament on which this drillhole was sited. Rock chip samples of BIF and magnetite-rich lithologies in the Holowilena Ironstone outcrop mapped on the eastern side of the licence area were analysed for iron, returning up to 40% Fe2O3 along with traces of gold and PGE. During 2010, preparations were made to drill targets of base metal interest. Two of these were magnetic anomalies related to the aforesaid Utah Corp. bedrock drillhole copper anomalies, while a third target would test a copper-zinc anomaly found by SADME drilling in 1993 over the central part of the Yednalue Anticline. A fourth target was chosen at the old Brady Dam copper workings, which appeared to overlie a prospective fault zone of some length. During April 2011, the licensee drilled 6 RAB/aircore holes for a total penetration of 374 m at the first three of these locations, but the contracted rig could not drive through Brady Creek to the last site due to not being able to cope with the steep creek banks. No significant mineralisation was detected at the former Utah anomaly sites, and only one drillhole, which twinned the earlier anomalous PIRSA hole CTN12, intersected low grade copper (average 0.25% Cu) and zinc (average 0.35% Zn).
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