An area centred ~90 km south-east of Tarcoola and adjacent to the western shore of Lake Gairdner is being explored for possible economic buried Carrapateena or Prominent Hill style IOCG and polymetallic skarn style mineralisation which may be...
An area centred ~90 km south-east of Tarcoola and adjacent to the western shore of Lake Gairdner is being explored for possible economic buried Carrapateena or Prominent Hill style IOCG and polymetallic skarn style mineralisation which may be associated with zones of elevated relief seen in existing gravity and aeromagnetic data, and also for possible buried epithermal vein style mineralisation that may be associated with igneous bedrock known to be anomalous in silver. Prospective rocks comprise the Mesoproterozoic Gawler Range Volcanics succession and co-magmatic Hiltaba Suite intrusions. Potential may also exist for finding komatiite-hosted magmatic nickel occurrences within undiscovered south-eastward extensions to the Lake Harris Greenstone Belt. Initial work conducted on the licence involved desktop studies of available geoscientific data, followed by the collection of 717 reconnaissance soil geochemical samples on a 300 m x 300 m grid spacing, the collection of a further 222 infill soil geochemical samples on a 50 m x 50 m grid, and the taking of 2 grab rock chip samples, all to undergo multi-element assaying, the acquisition during March 2012 of 23 line km of ground magnetic readings along 19 traverses running north-south 100 m apart across the Border prospect, the acquisition during July 2012 of a ground gravity survey over two 200 m x 200 m grids, with 447 new stations read, and lastly, exploratory drilling during November-December 2012 of 4 inclined RC holes with a total penetration of 444 m. Difficulty was experienced in obtaining reproducible surface geochemical anomalies via infill sampling, which was attributed to probable finely particulate silver in the soil samples. Assaying of the two selected rock chip samples did not return anomalous silver. Holes 12RGDRC01 to 03 located in the north of the tenement near Lake Harris tested an historic shallow lead anomaly defined by RAB drilling at the Peninsula prospect. Those drillholes' sample assay results did not confirm this anomaly, but did detect an elevated Ag and Au geochemical response at the weathering contact with the underlying rhyolite. Hole 12RGDRC04 formed part of a planned two-hole inclined RC drill programme to test the coincident magnetic/gravity anomaly at the Border prospect in the south of the licence. No significant Cu-Au mineralisation was encountered in the thick basaltic sequence penetrated. However, in this hole cuttings recovered from the downhole interval 144-146 m were interpreted to represent a metamorphosed ultramafic rock unit, with the reported sample assay values of 1680 ppm Cr, located in relicts of primary magnetite, and 680 ppm Ni (possibly held within silicates) being consistent with the composition of a basaltic komatiite or Mg-rich basalt. Both drillholes put in at this prospect, 12RGDRC04, intersected magnetite bearing mafic volcanic rocks (metabasalts and diorites) over their entire drilled lengths, that carry minor visible signs of sulphides. Petrological descriptions for samples from the hole interval 122 m to 148 m in 12RGDRC04 provided to Renaissance by consultant Pontifex confirmed that the chrome and nickel-bearing geochemical zone is reflecting “amphibole-rich and metamorphosed probable ultramafic rock with accessory disseminated opaque oxide grains and veinlets”. This early drilling result suggests the likely presence of a thick sequence of probable Archaean age, magnetite-bearing mafic and ultramafic greenstone rocks within the Border prospect area, which may be responsive to detailed electromagnetic surveying aimed at defining possible nickel sulphide targets. From licence Year 2 onwards, no further field work was done on the subject tenement before a decision was made during year 7 to allow its tenure to lapse.
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