A prefeasibility study for the Woodlawn Underground Project was undertaken during the March quarter 2007. A feasibility study was commenced, targeting an initial mine life of eight years and an ore production rate of 300,000 to 400,000 tonnes per annum for ~80,000 tonnes per year of zinc, copper and lead concentrates.
Metallurgical test work to determine plant design criteria has been undertaken but further work is required to assess the performance of underground ore combined with retreatment material.
Work to date has shown that the historic workings are dry to a depth of 300 metres below the surface.
On 26 October 2006, the Company announced a resource estimate for the Woodlawn Underground Project of 10.1 Mt @ 1.8% Cu, 4.0% Pb, 10.2% Zn, 0.55 g/t Au and 85 g/t Ag.
At the time of estimation, the overall resource grade equated to 16.9% zinc equivalent (Zn-Eq), or the equivalent of 1.6 million tonnes of zinc metal from an in situ total contained metal perspective. Individual relative metal recoveries were not considered in this Zn equivalent estimate as the resource estimate preceded metallurgical test work.
The resource (Table 1) was independently estimated by SMG Consultants at a cut-off grade of 7% Zn-Eq,
Table 1
| Resource Category | Tonnes | Tonnes (%) | Cu (%) | Pb (%) | Zn (%) | Au (g/t) | Ag (g/t) |
| Measured | 3,600,000 | 36 | 1.8 | 4.0 | 10.4 | 0.53 | 85 |
| Indicated | 4,980,000 | 49 | 1.8 | 4.0 | 10.2 | 0.55 | 84 |
| Inferred | 1,520,000 | 15 | 1.7 | 4.1 | 9.6 | 0.61 | 87 |
| Total | 10,100,000 | 100 | 1.8 | 4.0 | 10.2 | 0.55 | 85 |
As part of the feasibility study for the WUP, two further diamond holes were drilled in order to gain samples for metallurgical test work. Both holes targeted remnant mineralisation in pillars associated with old workings in the underground mine. The previously reported hole WLTD004 was designed to intersect part of C Lens, while hole WLTD005 was designed to intersect A and B1 Lenses. Drill Hole WLTD004 and 4B The drilling of hole WLTD004 and a wedge hole (WLTD004B) has validated the accuracy and confidence of the underground resource model input data in the area drilled as well as provided samples for confirmatory metallurgical test work. Drill hole WLTD004 successfully intersected mineralization associated with the C2 and C lenses. These lenses have been partly mined by previous operators. The C2 Lens is a subsidiary copper rich lens located approximately 25 m into the hanging wall of the much larger C Lens. Two samples of the C2 Lens and one sample of the C Lens were obtained from this hole. Mineralisation associated with the C Lens was intersected from 438.9 m to 446.2 m. This zone is associated with a large remnant pillar and is located approximately 400 m below surface. Mineralisation in this zone is dominated by massive sulphides containing pyrite, sphalerite, galena and chalcopyrite. Assays indicate lower grade base metal mineralisation followed by 4.2 m of high grade Zn rich mineralization. Gold and silver values for the intercept are quite elevated compared to average resource grades. Unfortunately the hole intersected the edge of a stope and had to be abandoned at 446.2 m. However, based on the resource model, high grade zinc mineralisation is confidently predicted for a further 12 m to 15 m beyond the end of this hole. The C Lens was the largest individual lens mined at Woodlawn and constitutes approximately 35% of the current underground Resource. Significant intersections returned included: Drill Hole WLTD005Additional samples for metallurgical test work were obtained by drilling hole WLTD005 through remnant pillars in the A and B1 Lenses (Table 1). The hole intersected relatively high grade zinc rich mineralisation associated with A Lens from 353 m to 371 m. Average core recovery through this interval was about 40% Similar mineralisation was intersected from 417 m to 427 m which represents B1 Lens. Core recovery through this interval averaged about 45%. Core recoveries have not been factored into the assays or associated intercept calculations, however, the widths and grades of mineralisation reported are consistent with adjacent holes drilled by previous operators. A 5 m wide zone (427 m to 432 m) of copper mineralisation was intersected in the immediate footwall of B1 Lens. Additional copper rich mineralisation was also intersected deeper in the footwall of B1 Lens from 441 m to 446 m. Significant intersections included: Click on image for an enlarged version
Hole From (m) To (m) Interval (m) Cu (%) Pb (%) Zn (%) Ag (ppm) Au (ppm) WLTD004 383.0 389.8 6.8 2.79 0.10 0.85 12 0.16 WLTD004B 398.5 406.6 8.1 2.92 0.07 0.38 13 0.22 WLTD004B 438.9 446.2 7.3 1.66 4.87 12.34 171 2.32
*Footwall of B1 Lens Hole Lens From (m) To (m) Interval (m) Cu (%) Pb (%) Zn (%) Ag (g/t) Au (g/t) WLTD005 A 353.0 371.0 18.0 0.70 4.66 11.48 88 0.56 WLTD005 B1 417.0 427.0 10.0 0.57 5.13 10.74 124 0.32 WLTD005 B1* 427.0 432.0 5.0 4.01 0.14 1.34 19 0.09 WLTD005 B1* 441.0 446.0 5.0 2.14 0.09 0.25 9 0.07
