The Mchinji licence covers 870 km2 and is adjacent to areas with known mineral potential, some of which are licenced including the Mkango’s Chimimbe Hill nickel-cobalt licence to the south. The Mchinji licence has been granted for the exploration of nickel, cobalt, gold, base metals, graphite, platinum group metals, ilmenite, vanadium, chromium, uranium and rare earth metals.
The licence is initially awarded for a 3-year term, after which it can be renewed twice for further two-year periods with a 50% reduction in the licence size required with each renewal.
The licence is located in the Mchinji District, with its western border just east of the town of Mchinji. The southeastern corner of the licence falls within Lilongwe District. The small town of Nkotakata at the centre of the licence is 90km along the M12 highway from Malawi’s administrative capital, Lilongwe. The M18 highway runs north from a junction with the M12 at Nkotakata. A railway traverses the licence alongside the M12 road and runs to the sea port of Nacala in Mozambique. There are many dirt roads and tracks in good condition offering access to most parts of the licence, and any remaining distance is easily covered by motorbike, bicycle or on foot. Elevation is approximately 1,050-1,150m, the more elevated parts being mainly in the west, and a number of hills stand above the broad plain.
The earliest known work was carried out in 1908 by T.E.G. Bailey of the Imperial Institute Mineral Survey of British Central Africa. He identified the main metasupracrustal and igneous rock types, remarking that “what little evidence we now have points to a uniform granite basement” and pointed out that the gold-bearing reefs then being worked at Missale and Chifumbazi in Mozambique were in metasupracrustal rocks close to their contact with the granite.
The Anglo-American Company prospected the area in 1937, and New Consolidated Goldfields Ltd in 1957-58. Later investigations associated with the siting of water supply boreholes were confined to very small areas.
Geological mapping was carried out concurrently with geochemical drainage reconnaissance by the Geological Survey of Malawi in 1964. This work included the collection of alluvial samples at half-mile intervals at all streams and dambo (broad, grass-covered, swampy valleys) together with alluvial samples from watershed areas far from active drainage patterns. The samples were analysed for copper, lead, nickel, chromium, tin, silver, beryllium, and arsenic. Bulletin 24 of the Geological Survey Department, Malawi Ministry of Natural Resources (Thatcher, E.C. and Wilderspin, K.E., 1968) contains a geological map and a summary of the geochemical reconnaissance, and remarks that graphite deposits are particularly noteworthy in the area.
Geology and Geophysics
Virtually all geological knowledge of the licence is reported in Thatcher E.C. and Wilderspin K.E. (1968), ‘The Geology of the Mchinji-Upper Bua Plain’, Bulletin 24 of the Geological Survey Department, Malawi Ministry of Natural Resources. This publication covers Mkango’s Mchinji and Chimimbe Hill licences but extends north and east.
The surficial geology of the area is characterized by a plain of residual soils, colluvium and alluvium, punctuated by hills of granitic gneisses and quartzite, with sporadic exposures of various gneisses and schists interpreted to be of supracrustal origin. All of these rocks are believed to belong to the Proterozoic Mozambique Mobile Belt.
A dendritic pattern of watercourses and dambo, not generally controlled by the underlying geology, drains into the Ludzi and Bua rivers which run east before turning north just outside the northeast corner of the licence.
The magnetic pattern of the licence reveals a number of major geological structures or features in the basement rocks. Some are related to a northwest-southeast trending interpreted shear belt that dominates the southern part of the licence. There is also a large east-west trending fault in the north of the licence, and a north-south trending probable dyke of regional extent (hundreds of km, beyond the limits of the countrywide geophysical survey) that enters and exits the northwest of the licence.
The ternary radiometric image of the licence shows domains that coincide with the interpreted major geological structures, particularly in the south. This suggests that the extensive soil cover is largely residual, offering reasonable confidence that soil geochemistry will be the best initial exploration method.