A multi-licence project area centred on the historic abandoned Burra copper mine is being explored for possible economic, buried Burra type copper oxide and copper carbonate mineralisation that may have formed within Neoproterozoic metasedimentary...
A multi-licence project area centred on the historic abandoned Burra copper mine is being explored for possible economic, buried Burra type copper oxide and copper carbonate mineralisation that may have formed within Neoproterozoic metasedimentary country rocks in a former volcanic or porphyry - related mineralising fluid dispersive setting. Phoenix Copper Limited (PXC) has been actively exploring the Burra district since late in 2005, after acquiring prospective parcels of ground from Copper Range and other small explorers. During the 2009-2010 reporting year, continued reconnaissance soil and rock chip grab sampling was undertaken, to the extent that the greater portion of the project area has now been covered with widely spaced (2 km x 20 m) 34-element FPXRF geochemical analyses (25,684 readings in total), and in places detailed 50 m x 20 m infill samples for laboratory analyses (168 sieved soil and 159 rock chip). The geophysical properties of the Adelaide Geosyncline strata and intrusive rocks across the entire tenement package were reviewed, and many drill targets, defined for several commodities, were generated from the licensee's geological, geophysical and geochemical data interpretations, including: Princess Royal for copper and gold; Mongolata and Black Hill for gold; Burra, Burra North, Burra West and Hallet Hill for copper; Redbanks for phosphate; and Redbanks and Mongolata for uranium. As well, in February 2010 much of the historic SAEI survey airborne geophysical data for the region were reprocessed for PXC and an interpretation of them commissioned from consultant Geoforce Pty Ltd, hoping for better anomaly definition, and to allow for the production of an interpretive solid geology map. A very detailed analysis of all past exploration results was performed to try to establish what might be effective mineral systems vectors towards buried primary sources of copper and gold mineralisation within the Burra district. The Mongolata, Black Hill and Princess Royal prospects were drilled, with the following work statistics reported: on Burra North EL 3716, 8 inclined diamond holes for 414 m plus 26 vertical RAB holes for 1990 m were completed at Black Hill, 4 RAB holes for 221 m were drilled at Golden Speck, 6 RAB holes for 566 m were drilled at Feltus Find, and 4 RAB holes for 360 m were drilled at Retriever; on Princess Royal EL 3549, 30 vertical RAB holes for 1139 m plus 15 vertical diamond holes for 514.8 m were completed at Princess Royal, and 7 RAB holes for 300 m were drilled at Utica. Significantly, Phoenix Copper's RAB drilling confirmed anomalous copper-gold zones that had been identified by its surface geochemical sampling, in locations which had never been drilled in the past. Also, the drilling encountered several anomalous zones of low grade gold. At Mongolata, diamond drilling of 3 holes along strike from the historic Mongolata gold mine during March 2009 (the first such drilling in this area) had returned a best gold intercept of 2 m @ 0.052 ppm Au from 139 m in the Cox Sandstone within hole PCD001. Although this result is of low tenor, PXC thought that the structures and the continuity (at least 3.5 km of strike) of rocks that host to the known nugget type coarse-grained gold mineralisation, as observed at surface and in old workings, were encouraging, as is the level of alteration observed in the core. Both the Cox Sandstone main target and lesser gold-bearing quartz - limonite veins were intersected in all three holes, and were shown to be enhanced in gold content compared to the background gold levels in surrounding rocks (2 ppb Au). Therefore this initial drilling was followed up during 2010 by the drilling of 14 vertical RAB holes for 1147 m. Several narrow gold intercepts were made, the highest grade being 1 m @ 1.80 g/t Au from 7 m depth in hole PCRB0031. The RAB drilling done during October 2009 at PXC's Black Hill prospect, located 7 km north-east of the old Mongolata Gold Battery, was more successful. 26 angled holes were drilled for 1999 m, of which 2 holes returned high grade intercepts (the best being 6 m @ 23.35 g/t Au from 66 m downhole in hole PCRB014 - which PXC stated is the best gold result from the Adelaide Geosyncline of recent years) and 6 others, low grade gold intercepts. This drilling has shown that the NW striking, steeply westwards dipping Watervale Sandstone is mineralised for 300 m along the sheared footwall contact of this unit with the underlying Saddleworth Formation siltstones. The later-completed diamond drilling component of the 2009-2010 campaign, undertaken during January-February 2010, comprised 5 angled holes for 414 m designed to test the extent of the two earlier high grade gold RAB intercepts. Continuity of the mineralisation was found, but at much lower grades (0.4% Cu is 0.2 g/t Au. This resource lies entirely within EL 3459, and at present is defined only to depths <40 m below the surface. The company is confident that there is obvious scope to increase the quantity of the stated Princess Royal resource by drilling additional exploration targets close to the Princess Royal prospect to the immediate north, south and west, based on elevated copper assay values reported from historic drillhole sampling and soil geochemical sampling. During the 2012-2013 reporting year, follow-up exploratory drilling of 10 fully cored inclined diamond holes for 1043.2 m (PCD0042 – PCD0051) was undertaken at the Eagle prospect on EL 4226. A best result of 13.3 m @ 1.22% Cu from 69.2 m, including 6 m @ 1.61% Cu from 69.3 m, was obtained in hole PCD0045. The mineralized zone defined by the drilling done to date remains open in all directions. The data from the SADM 1964 IP survey were acquired, reprocessed and imaged for PXC by Riaan Mouton at ASST, utilising modern day modelling software; the results showed several shallow chargeable features of interest that warrant drill testing. It was evident that the Eagle prospect lies in the northern portion of a north-west trending IP high ~600 m long, that also contains subsidiary highs of similar size located both to the north and the south of the historic Burra mine. During the 2013-2014 reporting year, 14 inclined exploratory RC holes for 1024 m were drilled at the Black Hill historic gold workings prospect on EL 4970 Mount Cone, which is located ~10 km north-east of Burra. Anomalous gold up to 1 m @ 0.28 g/t Au, plus elevated copper, lead, nickel and zinc, were encountered within narrow epithermal quartz veins drilled over a 3 km strike length. The mineralisation appears to be structurally controlled by an iron rich brecciated shear zone formed on the brittle/ductile contact between Watervale Sandstone Member sandstone and underlying Saddleworth Formation siltstone, and appears to be concentrated into steeply plunging lodes associated with cross-cutting structures. The mineralised zone as tested remained open in all directions. A further 1469 surface soil geochemical samples on EL 4226 Burra were scanned using an FPXRF analytical instrument. During the 2014-2015, 2015-2016 and 2016-2017 reporting years, no work was done. During the 2017-2018 reporting year a magnetotellurics (MT) survey was undertaken, however at the time of reporting the data was still under review and is due to be submitted in the reporting period. The survey consisted of 11 MT sites on an approximately 10 km spaced grid was undertaken as a trial in collaboration with the University of Adelaide to test its application in areas of “high infrastructure” including powerlines, water pipeline, wind turbines and housing. Early processing by the University of Adelaide indicated that the “noise” associated with the infrastructure was able to be filtered out and that the application of MT should work in the area. The trial MT data will be integrated into a larger survey to investigate a large conductive model that was identified in the national collaborative MT AusLAMP program.