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Excellent New Gold and Silver Discoveries at Rannes Gold Project |
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High Silver in Gold Discoveries at Rannes Gold Project |
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Gold Discovery in First Rannes Drillhole |
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As announced on 4th December it is proposed to sell Central Minerals to Solomon Gold Plc to create a South West Pacific iintegrated gold exploration company. For full details click here to view the announcement.
In 2007 gold exploration tenements located at Rannes north of Cracow, QLD were transferred to the new purely gold focussed subsidiary Central Minerals Pty Ltd, and subsequently new areas were applied for at Clermont and extending north and south of the original Rannes tenements.
One of the most exciting highlights of the year was the excellent new gold and silver discoveries on three of the first four targets within the Rannes Project Area. As announced to the ASX in releases on 14 and 21 December 2007, excellent widths and gold and silver grades were returned from first pass drilling at Rannes. Sixteen (16) reverse circulation drill holes (total 1,302 metres) were drilled on the first four (4) prospects defined by soil sampling.
Recent geological work and the drilling results to date indicate that the deposits are in the form of shallow pitching shoots that are preferentially developed in altered and gently dipping limestone horizons, as opposed to the volcanic rocks. A shallow pitch implies that most of the recorded gold intercepts are close to true thickness (about 75% of the intersections).
High silver contents are considered to provide considerable value to augment the gold grades. Highlights include 38m @ 2.22g/t Au eq at Kauffmans, and 32m @ 2.56g/t Au eq and 40m @ 2.5g/t Au eq at the Crunchie deposits (see Footnote 2 of 2008 Annual Report).
Much interest has been expressed in the exploration model the Company has developed at Rannes – described as a “Carlin Type” sedimentary hosted gold system – after the Carlin Trend gold system in Nevada, USA that first started to be understood in the 1970’s. The distinguishing characteristic of this type of epithermal system is that the gold is deposited in fairly flat lying deposits developed within altered calcareous and dolomitised sediments.
In Figure 3 below, the difference between this mode of deposition and that (say) at the underground Cracow Gold Mine* 140km south of Rannes is well illustrated. The Cracow system is regarded as an epithermal vein hosted system (near vertical) and is a low sulphidation deposit in older rocks than Rannes.
Rannes on the other hand is a medium sulphidation gold occurrence (there is sulphurous material in the Bowen Basin sediments) that is sediment hosted in younger rocks. This greatly helps to explain why the step out drilling of earlier explorers was not successful. D’Aguilar considers that many of the previous drill holes did not test the shallow dipping mineralised zones.
At Rannes, several characteristics further complicate the model. As at Carlin, there appears to be folding and thrust faulting which brings the mineralisation back to the surface and the sequence repeats. In Figure 4 below, the prospects already drilled are shown with red stars, with other targets indicated by the soil line grids. There is a strong suggestion (to be proven by drilling over coming months) that by folding or faulting the sequence is repeating, bringing the mineralisation back to near surface.
At the Crunchie prospect, D’Aguilar noted the presence of high levels of silver with gold which is also a characteristic of sections of the Carlin Trend. The Rannes Project area, as demonstrated in Figure 2 below, covers an area twice the size of that of the Carlin Trend in Nevada, USA. D’Aguilar believes that relatively little Carlin style exploration has been conducted in Australia to date and considers the Rannes Project to offer the potential for the same size and style as evident on the Carlin Trend.
While heavy rain and floods prevented further field work at Rannes until April 2008, subsequent investigation has led to the application for much more ground north and south of Rannes over recent months. Delays in availability of suitable drilling rigs meant that further drilling at Rannes did not commence until late August 2008.
Further thick gold – silver intersections from Crunchie Prospect, Kauffmans Prospect and Homestead Prospect were announced on 24th November 2008. Highlights included:
Sufficient field work was also completed on granted Clermont area tenements to allow first pass reconnaissance drilling to commence on initially identified target areas.
Click on images to enlarge
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Figure 1: Project location |
Figure 2: Rannes compared to the Carlin Trend, Nevada, USA at the same scale |
Figure 3: Rannes Project Schematic Cross-section – |
Figure 4: Rannes Soil Lines and Geochemical Trends |
Figure 5:
Crunchie prospect drilling plan |
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