Kihabe Base Metals Project - Botswana
Location: Ngamiland, Botswana and Tsumkwe, Namibia
Owner: Mount Burgess Mining NL 100%
Project Location
The Kihabe Base Metals Project is located on the border of Botswana and Namibia about 700km north-west of the capital, Gaborone, in Ngamiland. The Project is 350km by road from Maun and 50km from Tsumkwe, Namibia.
Exploration Licences
The Company has exploration licences covering 100% of the known prospective Proterozoic Belt of metasedimentary rocks, with around one third of the prospective geology occurring in Botswana (PL 69/2003) and two thirds in Namibia (EPL’s 2818 and 3022)
The Kihabe Project was held in the early 1980’s by Billiton Botswana (Pty) Limited, which carried out extensive soil geochemical sampling programmes and drilled three anomalous prospects: Kihabe, Nxuu and the Gossan Prospect.
The Kihabe and Nxuu Zinc-Lead-Silver Resources
To date 13,400m of reverse circulation drilling and close to 7,300 metres of diamond core drilling has defined combined JORC Resources at Kihabe and Nxuu of 29.9 million tonnes grading 2.62% zinc equivalent, applying a 0.5% low cut. 55% of the Resource conforms to an Indicated Category and 45% to the Inferred Category.
For the purpose of the project scoping study a combination of resources from both the Khabe and Nxuu deposits, in the region of 25 million tonnes @3% Zn/Pb, would likely be selected to provide for a 2.5 million tonne p.a. mining rate over 10 years.
About 30% of the Kihabe resource is oxidised – the remainder being sulphidic and all of the Nxuu resource is oxidised.
The Kihabe Resource is a sedex style deposit located along a contact between the dolomite footwall and a sequence of rhythmically bedded sandstones, which have been folded and metamorphosed to, respectively, dolomitic marble and chloritic quartz wacke. The local geology of the deposit is known to be a west-plunging syncline.
Zinc, lead and silver mineralisation which is developed within the host quartz wacke occurs right at the contact with the dolomite. Mineralisation forms a series of overlapping stacked horizons controlled by the beds within the quartz wacke, over a strike length of 2.4 km.
Within this 2.4km mineralised strike length, 1.8kms falls within two currently proposed open cut pits. Within the two proposed pits, applying a 0.5% low cut, the deposits have an average width of 26m down to 175m, the depth extent to which the resource has been calculated to date. In parts the deposits are up to 60m wide, with many sections containing average widths of between 35m – 45m.
Drilling conducted to date shows that this Sedex style deposit extends below 175m depth, indicating a high probability of increasing the resource base with further deeper drilling. With pit wall slopes conservatively designed at 40 deg, the average waste to ore ratio for the two proposed open cut pits currently stands at 5.5 – 1. It is believed that this ratio will be reduced with geotechnical drilling confirming the known competency of the footwall dolomite and hanging wall quartz wacke, thereby allowing for the design of pit wall slopes greater than 40 deg.
The Nxuu resource, also a sedex style deposit, is located approximately 5.5 km east south-east of Kihabe. Zinc and Lead mineralisation at Nxuu is developed within a shallow, flat lying sedimentary quartz wacke host rock, situated in a synclinal structure or basin, bounded by barren dolomite.
A pit for the recently updated Nxuu resource has yet to be designed. As a basinal shaped deposit, some 550m long, 250m wide and reaching a maximum depth of only 60m, it is anticipated that it will have a low waste to ore ratio.
Potential for the Discovery of Further Deposits/Resources
Zinc/Lead/Silver mineralisation in this region has to date been found at both Kihabe and Nxuu, to be hosted within quartz wackes at the point of contact with the regional dolomite. Two new quartz wackes have recently been found in regional drilling programmes, one 3kms and another 9kms SE of the Nxuu resource. Ground geochemical sampling programmes are being conducted to more precisely delineate areas for drill testing.
Development Progress
Recent mineralogical test work has shown that within the oxidised resource zones, zinc is tied up in Smithsonite and Baileychlore. Both the Smithsonite and Baileychlore are amenable to acid leaching, yielding zinc recoveries of 93% over 12 hours at 25 degrees celsius. The zinc within the acid solution can then be recovered on site as zinc metal by way of electrowinning. Lead recoveries from galena have also been tested to the 93% level.
Half of the Company’s current combined resource base at both Kihabe and Nxuu, representing some 12.5 million tonnes or 5 years of the projects estimated mine life will be amenable to acid leaching, allowing for the production of zinc metal on site. This should have a significant positive impact on project margins.
The project scoping study compiled in May 2009 will be updated to incorporate the following:
- The significant increase in zinc and lead prices from US$1,200/t in May 2009
- The 43% increase in metal recoveries from around 65% recovered to 93% recovered
- The revision of the process flow sheet to incorporate acid leaching and electro-winning of zinc metal on site and to reduce the size of the flotation circuit as now required for only half of the project resource base.
Gossan Prospect
The Gossan anomaly is a two kilometre long, by half kilometre wide soil anomaly with +1,000ppm zinc and +500ppm lead in soil, hosted within a valley bounded by dolomite, situated 15 km south of the Kihabe resource.
The Company has identified an in-situ gossan outcrop with peak values in rock sampling of 21.95% zinc, 7% Pb and 30 ounces per tonne of silver, which is a likely source for the extensive soil anomalism.
End Uses of Zinc, Lead and Silver
Zinc End Use
50% Galvanising
17% Zinc Alloying
17% Brass and Bronze
6% Zinc Semi-Manufacturers
6% Chemicals
4% Miscellaneous
Source: International Lead and Zinc Study Group
Lead End Use
80% Batteries
6% Rolled and Extruded Products
5% Pigments and other Compounds
3% Shot/Ammunition
3% Miscellaneous
2% Alloys
1% Cable Sheathing
Source: International Lead and Zinc Study Group
Silver End Use
54% Industrial Applications: Dental Alloys, Solder, Electrical Contacts, High Capacity Batteries, Paints, Mirrors and Polyesters
19% Jewellery
12% Photography
8% Coins and Medals
7% Silverware
Source: The Silver Institute
