Nyimba Area - Zambian Copperbelt (sitios de interés)
Descripción del sitio
Area
Chipirinyuma Resource base:
2Mt at 4% Zn
Prospects: Chipirinyuma, Mpongo and Umba River
A number of companies and government agencies, including Zamanglo, the Geological Survey of Zambia, Mindeco, a Zambian parastatal exploration company, and most recently, RTZ, have carried out exploration in the Nyimba area and several prospects have been identified.
The Chipirinyuma Prospect was discovered by a combination of stream sediment geochemical survey and aeromagnetics undertaken by Mindeco between 1975 and 1979. Trenching revealed massive,possibly stratabound, sulphide bands between 3 and 12m thick occurring within gneisses. The major sulphide is pyrrhotite, with lesser amounts of pyrite, chalcopyrite and sphalerite. The bands outcrop as gossans forming prominent ridges in the area that can be traced along strike for approximately 6 km. Results from four of six diamond drill holes completed to test the gossans at depth include up to 4m at 5.3% Zn and 0.9 % Cu. During the mid 1990s, RTZ drilled 5 RC holes targeting a geophysical anomaly at the extreme western end of the prospect, away from areas of known gossan outcrop. One hole intersected grades of up to 4% Zn and all of the other holes intersected mineralisation of some form.
The gossans of the Mpongo Prospect were initially discovered in the 1930s, but first explored in detail in 1963, when Chartered Exploration re-sampled old trenches and completed 11 diamond drill holes over a 1,500m strike length to investigate a carbonate-rich haematite-magnetite ironstone sequence. One of the holes returned an intersection of 2.5% Cu, 4.3% Zn and 0.8% lead (Pb) over 3.4m from a depth of 61m. The area was further explored in 1995 by RTZ, who undertook a ground magnetic survey and a five hole diamond drilling programme, of which only one hole was completed. Three mineralised horizons were defined by mapping and an exhalative horizon traced for 40 km along strike. The completed hole intersected 24.5m at 0.53% Cu, 3.73% Zn, 1.2% Pb and 52.8 g/t silver (Ag).
The Umba River Prospect was investigated for gold mineralisation prior to 1930. More recently, in 1973, an aeromagnetic survey defined a series of anomalies, and geological and regional geochemical surveys revealed the presence of Cu-Pb-Zn mineralisation. The Chinkombe shear,related to the MDZ, was traced for over 6 km along strike and high gold values were obtained from grab sampling. The high gold grades, however, cannot be verified as there were problems with the laboratory used for this work, and six RC holes drilled by RTZ produced no significant results.
-14° 34' 4.50", +30° 51' 2.35" (Niymba)