Thakadu

Technical Report
RSG Global, Thakadu Copper Project, July 24, 2007 (PDF 15.20MB)

The Thakadu deposits are sediment-hosted strataform disseminated sulphide zones in a poly-deformed and metamorphosed sequence of volcanic, volcaniclastic and clasticsedimentary units. The primary sulphide minerals are chalcopyrite (85-90%) and bornite (10-15%) with minor pyrite adjacent to the copper bearing material. The upper approximately 50 m of the deposits are characterized by secondary zones of oxidation, in which the primary sulphides are replaced by chalcocite, malachite and cuprite-tenorite together with traces of native copper and marcasite.

The primary ore-forming minerals at the Thakadu deposit are chalcopyrite (85-90%) and bornite (10-15%), both as fine to medium grained disseminations throughout the host rocks. Minor pyrite occurs adjacent to the copper-bearing zone, but only rarely inside it. A mineralogical zonation is apparent with a chalcopyrite-bornite assemblage in the centre, ranging outward to chalcopyrite, and then pyrite on the outside margins.

Chalcocite and covellite are present in trace quantities. The oxide zone at the Thakadu deposit consists of chalcocite, malachite, cuprite-tenorite, chrysocolla and traces of native copper and marcasite. The Makala deposit exhibits the same general characteristics as the Thakadu deposit in terms of host rock lithologies, primary sulphide mineralogy and sulphide mineral zonation.

Structural mapping in the vicinity of Thakadu and Makala has shown that a major ESE-WNW shear zone exists just to the north of the Makala deposits. Initial drilling has indicated that the degree of shearing and flattening of the ore zones around Makala has been intense. Furthermore, Thakadu has been shown to exist within a parasitic z-fold on the north limb of a regional fold structure. The fold structure closes to the SE, well away from the trace of the northerly shear. No exploration work has ever been focused on the fold closure, or on the southern limb of the fold.

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Regional Exploration

Regional Exploration
Two major extended work programs have been conducted on the Thakadu-Makala deposits; the first by BCL between 1962 and 1976 and the second by Falconbridge from 1977 to 1982. AFC has only recently acquired the mineral rights to these deposits and is in the process of acquiring detailed technical data on the deposits from various sources.

Mortbury began exploration in the Matsitama Belt in 1995. In 1995-96 Mortbury completed an airborne geophysical survey. Historical data compilations were also undertaken to identify possible exploration targets in the geology and past geochemical programs. The studies identified 147 separate, large and locally, high-grade geochemical anomalies. Exploration records showed that of these 147 anomalies, only 16 had ever been drilled by either percussion or diamond core drilling and that, in every case, geochemically anomalous copper assays or copper mineralization was intersected.

In 1998, Mortbury signed a joint venture agreement with Anglo American Prospecting Services (Proprietary) Limited ("Anglo") regarding the exploration and development of the Matsitama Project. Following expenditures of over US$3.5 million, Anglo returned the property in the middle of 2000.

Anglo initially completed a major digital compilation of the historical records, including GIS target-modeling. It then flew two airborne surveys over the entire licence area, a proprietary 128-band, four spectrometer hyperspectral survey and a combined magnetic, electromagnetic and radiometric Spectrem survey. The work on the historical targets largely confirmed or extended the previously known anomalies, while only a few of the holes on geophysical targets intersected any mineralization. Anglo completed 8,900 m of reverse circulation drilling in 94 holes and 2,345 m of diamond drilling in 15 holes.

The work by Mortbury as confirmed by Anglo has resulted in a substantially revised stratigraphic and structural framework for the belt and confirmed the existence and scope of at least three large mineralized targets measured in tens of kilometres of strike extent, as well as the numerous smaller anomalies. From preliminary compilation of the data at hand, three high potential areas (Tholo-Lepashe-Tau, Thakadu-Makala-Dihudi-Mutsuki and Nakalakwana) are attractive targets for further exploration.

Drilling
The drilling campaigns at the Thakadu-Makala deposits were conducted by BCL during 1962 to 1976. A total of 156 boreholes with a combined length of about 39,000 m were completed from surface, including both diamond and percussion drill holes. Another 882 m of underground diamond drilling was completed on the two deposits. The maximum depth to which the mineralization has been tested is approximately 550 vertical metres.

Falconbridge acquired the deposits in June 1977 and subsequently the BCL drill core, records, and analytical results were re-examined. After a series of verification exercises, including 524 check assay determinations for both copper and silver, Falconbridge concluded that the drilling information was accurate and sufficient for grade/tonnage estimates and potential mine planning exercises. Core stored at the former campsite at the Thakadu deposit is no longer useful for definitive work, having been vandalized and dumped.

Underground Exploration
BCL sunk shallow prospect shafts to approximately 70 m below surface on each of the Thakadu deposit and the Makala deposit with a combined 620 m of lateral underground development. These openings were used for a variety of purposes, including geological investigations, channel sampling for grade distribution, sampling for process test work, and for underground diamond drilling. Information from this work was used, together with the surface drilling database, to complete grade/tonnage estimates for both deposits.

Between 1977 and 1979 the Thakadu prospect shaft was rehabilitated and dewatered by Falconbridge. The underground workings were re-mapped in detail on both plan and section to verify and complement the BCL geological, geotechnical and analytical database. The openings were channel sampled for grade distribution purposes, mineralogical investigations and bench-scale metallurgical test work. In addition three tonnes of oxide and sulphide material was taken from underground locations and surface dumps for further process testing. Finally in October/November 1980, a bulk sample of 180 tonnes of sulphide material was taken for pilot plant test work.

Metallurgical Studies
Previous holders of licences covering the Thakadu-Makala deposits conducted extensive metallurgical test work on both the oxide and the underlying primary or sulphide portions of the deposits. Both BCL and Falconbridge conducted a variety of tests that have shown that the main metallic commodities, copper and silver, can be readily recovered as saleable products, using proven conventional technology. The oxide material from the Thakadu deposit is amenable to copper recovery by crushing and heap leaching followed by final processing through SX/EW technology, while the sulphide material can be processed into a saleable copper concentrate with silver credit by conventional crushing, milling and flotation methods.