An area located on the far south-western side of the Frome Embayment, in the vicinity of Martins Well, was initially secured mainly to investigate its prospectivity for sediment hosted uranium deposits within the local Tertiary strata. However,...
An area located on the far south-western side of the Frome Embayment, in the vicinity of Martins Well, was initially secured mainly to investigate its prospectivity for sediment hosted uranium deposits within the local Tertiary strata. However, potential for possible buried Cu-Au(-U) hydrothermal type mineralisation to have formed within the “basement” Proterozoic metasedimentary sequence was subsequently identified. During the first licence year, work comprised the office-based compilation of open file data followed by data reviews, interpretation and conceptual targeting, plus the conduct of a preliminary field reconnaissance visit to assess the identified targets and to determine the logistical aspects of doing more detailed ongoing work. It was realised that the potential of any paleochannel type uranium targets, while regarded as fairly good, would be tempered by an apparent lack of radiogenic source rocks in the hinterland to the local palaeodrainage area. A higher priority target appeared to be an unexplained magnetic high anomaly ~1 km long that was evident within, and cutting across, the core of the Willipa Anticline. Its apparent discordant nature and size suggested to Strategic Minerals that it might represent a large magnetite constructive hydrothermal alteration zone, which could have associated Cu-Au(-U) mineralisation. Another feature that was considered worthy of exploring was a cluster of gossanous horizons mapped in the bedrock sequence immediately north of the anticlinal dome, which previous company reports and old mining records had mentioned as being enriched in copper and precious metals. No field work was done during the second licence year, while the licensee undertook programme design and costing of planned geophysical surveys and drilling. Further rock chip sampling (84 samples) undertaken during 2008 returned a few anomalous supergene copper values of up to 11.3% Cu, but which averaged aroung 4.5%. Geophysical consultants were retained to model the existing AGSO airborne magnetic data over the Willipa Anticline, to estimate a source depth and geometry for the source body and to recommend an optimal drill test location. No additional work occurred on the licence during 2009 while joint venture negotiations were in progress. After JV partner Aldershot Resources assumed the management and technical control of EL 3508, that company retained a separate geophysical consultancy to review the potential of the Willipa Dome prospect in the south-eastern corner of the licence area. Based on doubts about the rigor of the previous magnetic data forward model, it was decided to acquire more suitably aligned and detailed aeromagnetic data on which to re-model the subsurface rock properties. During early May 2010, a low level 537 line km aeromagnetic survey was flown over the target anomaly, with a 50 m north-south flight line spacing and nominal 45 m ground clearance. This survey provided much better input data for source depth inversion modelling and for estimating the dip and thickness of the causative body. The magnetic anomaly was now shown to coincide with the mapped outcrop of the Holowilena Ironstone beds, i.e. it did not have any discordant amount of displacement from this rock unit, as proposed by the earlier consultant's geophysical interpretation that was based on the old AGSO aeromagnetic data that had been acquired along lines flown parallel to the strike of these beds. During September 2010, Aldershot Resources completed a single only inclined, fully NQ cored diamond drillhole to a total depth of 198.4 m, to test the Willippa Dome magnetic anomaly, which the new airborne ternary radiometric data had now also mapped as covering a 2 km x 1.5 km portion of the southern side of the dome. The drillhole encountered the target magnetic horizon at 151.47 m depth, where a ten-fold increase in the magnetic susceptibility of the drill core was measured, although this was insufficient to indicate a substantially magnetite-rich rock (alternatively, could it be ? ilmenite - bearing). No major zone of the expected hydrothermal alteration or of sulphide mineralisation was found, and no significant trace metal values were returned from drill core sample assaying. In consequence of this disappointment, the prospect was severely downgraded : the large magnetic anomaly was re-assessed as having a purely stratigraphic origin, being caused by an average 30.5% Fe content of the 25 m thick horizon of ferruginous siltstone cored from below 151 m depth. No other work was performed on the licence during the next 29 months, before it was decided to allow tenure to lapse.
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