Kihabe-Nxuu Base Metals Project - Botswana
Location: West Ngamiland, Botswana
Owner: Mount Burgess Mining NL 100%
The Kihabe – Nxuu Base Metals Project is located in Western Ngamiland, Botswana, on the border with Namibia, about 700km north west of the capital Gaborone. The project is 350km by road from Maun, Botswana.
The Company has developed Zn/Pb/Ag JORC 2004 compliant Indicated and Inferred Resources at the Kihabe and Nxuu deposits on PL 043/2016, in Western Ngamiland, Botswana. PL 043/2016 covers that portion of a Neo-Proterozoic belt of metasedimentary rocks, hosting what is believed to be SEDEX style mineralisation, situated on the Botswana side of the border.
To date MTB has developed resources at two deposits on the Botswana side of the project. The Kihabe and Nxuu deposits, 7 kms apart, contain indicated and inferred 2004 JORC compliant resources of 33 million tonnes of mineralization. From this resource base 25 million tonnes @ 3% Zn/Pb are the subject of a scoping study to be revised to a pre-feasibility study for a proposed 10 year mine life @ 2.5 million tpa. The Kihabe resource also contains 3.5 million ozs of Ag, together with Cu and V credits.
The in-ground Zn/Pb/Ag metal content of the resource base consists of some 750,000 tonnes of Zn equivalent metal.
The Kihabe deposit covers a strike length of 2.4 km, with two proposed open-cut pits covering a total strike length of 1.8 km, containing 14.4 million tonnes of resources. Within the 1.8 km of strike, the average width of the deposit is 27m from 5m below surface to 175m depth, the extent of the resource drill depth to date. Many sections of the resource are between 35m to 60m wide. With confirmatory geotechnical drilling, it is estimated that the two proposed Kihabe pits will have strip ratios in the order of 4.5 : 1.
Refer to Kihabe and Nxuu Drill Sections at the bottom of this page.
The Nxuu deposit covers an area of 550m by 250m with a total estimated depth of only 60m, containing 10.9 million tonnes of resources. Whilst further drilling has yet to be conducted to enable a pit to be designed, it is estimated that an open cut on this basin shaped deposit will have a strip ratio in the order of 3 : 1.
With both deposits being shallow (under 5m to 15m Kalahari sand cover) with potential low strip ratios, they represent potential low cost open-cut mining operations.
Style of Mineralisation
Mineralisation at both the Kihabe and Nxuu deposits has been described as being of late stage SEDEX style. Most SEDEX style deposits are found in dolomites. In this region however, the mineralisation occurred only after quartzite deposits formed over the dolomites through weathering and deposition from regional elevated or mountainous areas. Whilst the mineralisation is right at the contact with the regional dolomite, it was formed within what at the time was an overlying quartz wacke. With subsequent thrusting, folding and shearing, these deposits now range from being anything from horizontal to vertical as well as being in synclinal or anticlinal fold structures.
Mineralisation at the Kihabe deposit occurs within an almost vertical synclinal fold structure. Mineralisation at the Nxuu deposit occurs in a flat lying basin shaped structure.
The whole of the Nxuu deposit consists of oxide mineralisation as is the top 25% of the Kihabe deposit. The remaining underlying 75% of the Kihabe deposit contains sulphide mineralisation.
Proposed Methods of Treatment
THE NXUU DEPOSIT - All oxide mineralization
Zinc mineralisation in the Nxuu deposit is found in the Zn oxide mineral smithsonite. Metallurgical test work conducted on the smithsonite has shown that it is amenable to tank acid leaching, using 35 kg/t of acid, yielding 93% recovery in 12 hours at 25 deg C, the ambient Botswana temperature. This will enable Zn metal to be produced on site through tank acid leaching and electro-winning, thereby eliminating significant concentrate transport and smelter costs.
Lead mineralisation in the Nxuu deposit is found in the Pb carbonate cerussite. Metallurgical test work conducted on the cerussite has shown that recoveries of 93% can be achieved in 12 hours in the form of a Pb compound, which can be transported from site.
THE KIHABE DEPOSIT - Oxide zone
Zinc mineralisation in the oxidised zone of the Kihabe deposit is found in the Zn oxide minerals smithsonite and baileychlore. Metallurgical test work conducted on this mineralisation has shown that it is amenable to tank acid leaching, using 35 kg/t acid, yielding 92% recovery in 24 hours at 40 deg C. This will enable Zn metal to be produced on site through tank acid leaching and electro-winning, thereby eliminating significant concentrate transport and smelter costs.
Lead mineralisation in the oxidised zone of the Kihabe deposit occurs predominantly as galena (sulphide) together with minor oxide minerals. Metallurgical test work has shown that 92% Pb recoveries are achieved through flotation and concentration. A Pb concentrate will be produced on site for shipment to a smelter.
Acid consumption in the region of 35 kg/t to recover Zn metal on site from both the Nxuu deposit and the Kihabe deposit oxide zone, is considered to be low and economical because the mineralisation occurs in quartz wackes, low in carbonates. (Were the mineralisation to be in dolomites, which are high in carbonates which consume high volumes of acid, this process would likely be uneconomic.) Further test work needs to be conducted to achieve concentration of smithsonite and bailychlore, prior to acid leaching, in order to reduce tonnages treated and thereby further reduce acid consumption. It is envisaged that a process of heavy media separation can be successfully applied because of the high SG’s of both smithsonite and baileychlore.
THE KIHABE DEPOSIT - Sulphide zone
Zinc mineralisation in the sulphide zone of the Kihabe deposit occurs as sphalerite and lead mineralisation occurs as galena. Metallurgical test work has shown that at a 75 micron grind size, 94% Zn recoveries and 88% Pb recoveries are achieved within 15 minutes through flotation and concentration. Zn and Pb concentrate will be produced on site for shipment to a smelter.
This same metallurgical test work has also shown that 96% of silver (Ag) can also be recovered within 15 minutes. The Company is investigating the process for recovering Ag on site.
The Kihabe deposit contains copper and supergene vanadium credits which could be potential revenue contributors. Separate drill programmes will be required to delineate potential Cu and V resources to determine any such contributions. Only a shallow 40m depth drill programme will be required to delineate any V resource. Metallurgical test work will also have to be conducted to determine possible metal recoveries.
Ore Process Route (Simplified)
Provision for Oxidised and Sulphide Ore
Potential to Increase Resources
Potential to increase the Kihabe resource beyond the current 175m depth is very high as drilling to date has intersected wide mineralised zones around the depth of 175m. As a synclinal structure, this further supports the potential for finding deeper mineralisation and the repeat of other parallel mineralised zones.
Potential to increase the Kihabe resource grade by delineating a resource based entirely on diamond core (DD) drilling is high. To date the Kihabe resource base has been delineated based on 112 reverse circulation (RC) drill holes and 32 diamond drill (DD) holes. A comparison of grades from DD holes that were drilled to twin RC holes has shown an increment in grade in the region of 40%. A further exercise was conducted by calculating the average DD grades from only the DD drilling conducted within the 0.5% low-cut resource envelope and comparing them with those grades from ALL drilling, RC and DD, conducted within the 0.5% low cut resource envelope. A similar 40% increment was arrived at. The cost of conducting sufficient DD drilling within the Kihabe resource in order to delineate a resource based entirely on this drilling method will be in the region of US$2 million.
Potential to increase the project's resource base on a regional basis is high. Within this portion of this Neo-Proterozoic belt, considered to host SEDEX style mineralisation, most of which is covered by Kalahari sands of some 5m to 30m depth, there will likely be further quartz wackes which host mineralisation in this region. Since the delineation of the Kihabe and Nxuu resources, Six new quartz wackes have been discovered through drilling, one of which shows elevated Cu mineralisation and five of which show elevated Zn/Pb mineralisation. Further soil geochemical sampling is currently being conducted on these discoveries in order to search for the higher grade zones, which will hopefully reflect the point of contact with the regional dolomite, the zone which, in this region, has previously proven to be of likely commercial grade.