A very small area located ~25 km south-east of Mount Gambier was taken up to try to identify in outcrop or in the near surface a glass grade dolomite resource which would be suitable to mine as a replacement for Unimin’s Tantanoola dolomite...
A very small area located ~25 km south-east of Mount Gambier was taken up to try to identify in outcrop or in the near surface a glass grade dolomite resource which would be suitable to mine as a replacement for Unimin’s Tantanoola dolomite deposit. Dolomite in the Mount Gambier region forms the basal horizon of the Oligocene to Miocene Gambier Limestone. The dolomite which is the target of exploration on EL 3734 outcrops on a 3 km long, ESE trending belt of this formation, which may be related to a fault trending 120 degrees True. The licence area lies adjacent to and east of the Unimin-operated Caroline limestone mine. During the first licence year, exploration activities comprised: - reviewing data contained in Geological Survey of SA reports, and in Unimin's in-house records; - performing rock chip sampling and geochemical whole rock analyses (136 samples); - doing prospect scale geological mapping; - drilling 25 shallow vertical RAB holes for a total penetration of 208 m, and analysing 186 drill cuttings samples; and - conducting aerial photography, and making a topographic survey. Only 9 holes for 111 m were drilled on the dolomite target. The other 16 holes for 97 m were drilled within the subject licence on a limestone prospect to the south of the Caroline mine site, but failed to disclose the presence of a limestone resource suitable for use by Unimin. The mapping and the limited drilling for dolomite revealed the presence of a gently SE plunging syncline, with the dolomite overlain by up to 8 m thickness of limestone. The drill sample analysis results indicated that a glass grade dolomite unit subcrops continuously over 200 m strike length with a thickness of ~14 m. During licence Year 2, work occurred on two main prospect areas located on either side of the Mount Gambier - to - Nelson Road. 37 rock chip samples were collected for assaying, and in May 2008, 83 vertical RC holes were drilled for 1306 m at hole spacings of 50 m to 100 m. Significant intervals of dolomite were intersected downhole in both locations, and 1112 drill cuttings samples of it were sent for assaying. All samples were submitted to the Unimin Technical Services Division laboratory in Braeside, Victoria, to undergo XRF analysis. During licence Year 3, 1086 drilled dolomite samples were analysed, and a preliminary tonnage estimate was made. The XRF results disclosed the presence of two discrete zones of glass grade dolomite. The NW (Hills) zone was estimated to contain 1.57 Mt, and the SE (Earls) zone 1.16 Mt. During licence Year 4, no work was done. Further modelling of the resource, involving inputs from planned additional drilling, was dependant on satisfactorily concluding discussions with private landowners for gaining access. During licence Year 5, negotiations with local landholders continued with a view to applying for a mining lease and later commencing mining operations when this had been granted. An application was also made to extend the exploration licence into a second term, to secure what was now regarded as a strategic extractive resource of dolomite. During licence Year 6, on renewed EL 4929, negotiations with local landholders were continued. No work was able to be done by Sibelco for increasing confidence about the deposit's geology. During licence Year 7, mineral claims were pegged over the two dolomite zones in preparation for making a mining lease application should the ongoing negotiations with landholders prove fruitful. No work was done on the rest of the licence area, and its tenure was allowed to lapse at expiry. [The two mineral claims were subsequently issued to Sibelco in August 2014.]
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