The subject three contiguous exploration licences occupy the southern onshore part of the Fowler Domain, a tectonised magnetic domain located in the western Gawler Craton which has many geological similarities with the Thompson Nickel Belt of the...
The subject three contiguous exploration licences occupy the southern onshore part of the Fowler Domain, a tectonised magnetic domain located in the western Gawler Craton which has many geological similarities with the Thompson Nickel Belt of the central Canadian Shield. The ground was taken up primarily to explore for magmatic nickel sulphide mineralisation that may be hosted by the buried Yalata Ultramafic Complex, a 25 km x 70 km extent layered igneous intrusion which is one of the largest of its type within Australia, yet to date has been little explored. Other mineral exploration objectives recognised in this area may include Stillwater or Bushvelt style magmatic chromium plus platinoid precious metals, Olympic Dam style IOCG_U mineralisation, possible diamondiferous kimberlites and accumulations of heavy mineral sands in fossil marine strandlines within the cover. The dominant structures in this part of the Fowler Domain are a series of north-east trending, sinuous, shear zones cross-cut by younger north-west trending faults and shears. The area is covered by a sequence of Tertiary and Palaeozoic sediments of the Officer Basin, thickening to the west. For the Yalata layered intrusion, a clearly defined prospective basal margin has been mapped by a consultant's interpretation of previously acquired gravity, aeromagnetic and drillhole data. Along it several anomalous magnetic targets warranting immediate ground investigation have also been identified. The layered intrusion appears to have been emplaced on an unconformable contact between Archaean rocks of the Mulgathing Complex and Proterozoic rocks of the Ifould Complex. The Mulgathing Complex includes sequences of metasediments, metavolcanics and ultramafic sills. It was thought that such rocks could provide a suitable sulphur source that might contaminate any later intrusion and thus be favourable for the formation of magmatic nickel sulphide deposits. In 1995 BHP Minerals had drilled a 2500 nT magnetic anomaly (the Landing Ground prospect) lying adjacent to the Yalata layered igneous complex. The single RC drillhole encountered a locally brecciated, sericitised Hiltaba Suite type granite containing chlorite and partly flooded by haematite, at 130 m depth below the surface. The source of the intense magnetic anomaly was not explained, and this feature is believed to have untested IOCG mineralisation potential. Commencement of field work on the latest project by the licence grantee joint venture partners was delayed for two years until 2/8/2007, when the South Australian State Governor made a proclamation authorising rights of entry for EL holders onto the Yalata Aboriginal Reserve. On 27/11/2007 the Pathfinder joint venture agreement was signed with Newport Mining, whereby it could earn up to 60% of the licence interests by spending $1.5 million over four years on exploring ELs 3268, 3281 and 3282. After the completion of lengthy negotiations made with the Yalata Community to arrange land access, the only work actually undertaken by the new joint venturers occurred during mid-October 2009, when a gravity survey was carried out over selected locations along the interpreted basal margin of the Yalata intrusive complex. 214 gravity stations were read at 200 m and/or 1 km station spacing along five road traverses. However, interpretation of the survey results did not define the basal zone with sufficient precision to site a cored drillhole. In early October 2010 Newport Mining asked to withdraw from its Pathfinder JV agreement with the other licensees, and this action was eventually formalised during February 2011. A subsequently planned forward work programme, to involve: - fences of aircore or RC drilling as appropriate at locations on the Yalata intrusion basal margin defined by interpretation of the gravity data, to investigate the geology and the prospectivity for sulphide nickel occurrences - minimum total penetration 2000 m; - aircore or RC drilling as appropriate to test the Landing Ground prospect magnetic anomaly defined by earlier explorers; and - investigation of the heavy mineral sands potential; did not eventuate before the original licensees elected in March 2011 to surrender all of the tenements.
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