Kashitu Project - Lusaka, Zambia

Kashitu is situated in the far south-east corner of the Kabwe Large-Scale Prospecting Licence (EPN 6990), 7 km SE from the historical Kabwe Pb-Zn mine area, and immediately adjacent to and South of the town of Kabwe, in Zambia. The prospect occurs just to the west of the Kashitu Dambo.

 

The prospect is underlain by Neo-Proterozoic carbonate units of the Katanga Supergroup which form a WNW plunging synform. NE trending structures within the NW trending stratigraphy are thought to control the development of the Kabwe massive sulphide ore bodies, while disseminated and vein-type mineralisation is found to a lesser or greater degree throughout the entire syncline.

 

All previous explorers on the licence have been looking for a second Kabwe deposit, with various vintages of RAB, RC and Diamond Drilling targeting sulphide lenses, which all found some sulphide and silicate mineralisation, but no Kabwe-style massive sulphides.

 

There are four target types at Kashitu, ordered by increasing depth;

 

  • Surficial accumulations of high-grade Pb-Zn-Ag, found in the upper 1m and containing up to 30% Zn
  • Supergene enrichment associated with the near-surface karst interface, varies between 0-10m depth and in the range 10% Zn
  • Low-grade disseminations of sphalerite and willimite associated with blanket seepage-style algal-mat dolomite, or non-massive dolomite, 2-3% Zn
  • Kabwe-style pipe like massive-sulphide lenses and ore-bodies

 

Limited surface mining in the area exploited a discordant N-S lenticular willemite body roughly 30m x 3m and grading up to 30-50% Zn.  This operation was mostly illegal in nature and progression was likely hindered by the high-water-table.

 

Historical soil sampling by Zamanglo outlined a NW verging area 1.2km long by 0.3km wide with up to 15,000ppm Zn, extending West from the historical mine site and the dambo.

 

Multiple phases of drilling (including rotary air blast RAB, reverse circulation RC and diamond) have all targeted the discovery of deep-seated massive-sulphide Kabwe-style orebodies. While no massive sulphide lenses were discovered the drilling identified large zones of disseminated mineralisation, localised areas of veining and further defined areas of surface enrichment. Highlights include;

 

  • 170 RAB holes were drilled by BHP on a 50x100m grid, assays were taken at refusal. Where surface data is available the drilling defines a 300m x 250m zone of anomalous zinc > 5% which migrates to the west at depth. A 800m x 400m halo of Zinc >1% continues from surface to 2-3m depth. A strong E-W structural trend was delineated by the zinc at refusal.
  • 33 RC holes were followed-up by BHP on a 50x100m grid and confirm the ENE trend of anomalous zinc with widespread disseminated mineralisation (1-2% Zn) and localised vertical pods and veins of mineralisation with up to 5-20% Zn. The zone of anomalism measures 400m long and 100-150m wide and many holes end in mineralisation and remain open to the west, where a resource of 2.4 Mt at 2-3% Zn was defined at Kashitu West. The best RC hole was KRC5, with a whole hole average grade of 2.42% Zn from surface to EOH 60m, including intersections (7m @ 4.3% Zn from surface, 1m @ 10.25% Zn from 39m, 3m @ 12.7% from 49m and 1m @ 5.5% from 57m), ending in mineralisation.
  • 18 diamond holes have been drilled by ZCCM and BHP, the majority by ZCCM were concentrated in a 150m x 50m area and confirmed the presence of shallow, high-grade willimite veins and lenses with up to 53% Zn. BHP drilled four deep diamond holes across the EW extent of Kashitu, the best holes were KDH2 and KDH3, drilled 150m apart near the ZCCM holes to 251m and 227m respectively, and are two of the best holes drilled on the project. KDH3 contained 227.3m @ 2.57% Zn from surface including 7m @ 6.7% Zn from 172m, with further high-grade intersections (1m @ 16% from 71m, 1m @ 12.6% from 145m, 1m @ 28.3% Zn from 196m and 1m @ 9.37% Zn from 223m), ending in mineralisation. KDH2 contained 236m at 1.16% Zn from surface.

The historic drilling has highlighted a roughly 1,000m long by 100m wide ENE trending zone of anomalous zinc in the range 1-5% Zn. The zone consists widespread disseminations of willimite and sphalerite with localised higher-grade lenses and pods of willimite. At its very eastern extent the structure is co-incident with a small open-pit with contained zinc up to 53%. The opportunity exists for an undiscovered, deeper seated, Kabwe-style massive-sulphide source for the mineralisation.

 

Surface sampling by Berkley Mineral Resources BMR during 2016-2017 focused on confirming the high-grade surficial anomalism in the hope of defining a small resource for processing at the Kabwe plant, an aspect overlooked by previous explorers. Three-hundred and seventy-five hand-auger holes were drilled on a 50x100m grid and in-filled on a 50x50m grid, the average depth of refusal was 0.9m, generally restricted by the high water-table. Analysis was by the companies XRF with 36 samples sent to Misenge Laboratory, Kabwe. Eighteen samples assayed greater than 5% Zn, the highest 40.6% Zn in hole BMKS369. The surface sampling defined an area 200X200m with greater than 5% Zn, extending the area of surface anomalism outlined by the RAB drilling 100m south. A halo with >2.5% Zn extends 250x400m with a further narrow high-grade extension to the southeast.

 

BMR followed with a pitting programme of 32 pits on a 50x100m grid, to an average depth of 0.7m. Initially, one sample was taken at the base of each pit, subsequently, a few pits were re-visited and channel sampled. All pits assayed greater than 1% Zn, with seven assaying greater than 10% Zn. The best result of 31.06% Zn and 4.6% Pb correlates with logged Wash Plant Tailings Material WTP.

 

A back of the envelope resource calculation completed by Wardell Armstrong WA, at the request of BMR indicates the potential for a small 250mx150m resource of 17,250 tonnes at 2.5% Zn at surface.

 

Potential remains for a large (+50Mt) low grade (2-5% Zn) open pit-able Zn silicate resource, with further potential for a relatively small (0-5Mt) high-very high grade (>25% Zn + Pb) pods and lenses of Kabwe style mineralisation in the area.

 

Billiton terminated the project due to the closure of the Zambian office in 1999, and not because of technical reasons.

 

Figure 1. Location of Kashitu, with RAB holes in yellow, RC in red and diamond in green

 

Figure 2. Summary of Kashitu Significant Results