Mkango Resources recently announce that the Malawi government has renewed the Thambani uranium, tantalum and niobium exploration licence and issued four retention licences granted for five years from 20 October 2021 to 19 October 2026 – covering a total of 98.4 square km.
With the recent significant increase in international uranium prices, Mkango is currently reviewing strategic exploration and development options, including opportunities for joint ventures and other potential avenues to create additional project value.
The Thambani retention licences are located in the Southern Region of Malawi, within the Mwanza District in the northern part of the licence and the Chikwawa District in the south.
The licences are approximately 120km west of Blantyre (capital of finance and commerce) which is served by Chileka International Airport, and about 30km from the large town of Mwanza, the administrative headquarters of Mwanza District, which is located on the main road from Blantyre to Tete in Mozambique. Thambani is the main trading centre within the licence. Secondary gravel roads provide vehicle access from Mwanza town to the project area. The Thambani trading centre is connected to the national high voltage electricity grid and is approximately 30km from the new US$4 billion Tete–Nacala railway which transverses southern Malawi, passing through the southern part of the retention licences.
Mkango’s exploration activities to date have focussed on the Thambani Massif, a large body of nepheline syenite gneiss which is expressed in two prominent ridges, the East and West Ridges, respectively. Activities include acquisition of Landsat7 and ASTER satellite imagery for the licence area, systematic ground radiometric surveys to confirm and detail known airborne anomalies, reconnaissance geological mapping, trenching, and litho-geochemical sampling programmes. The work has identified a number of potential uranium and associated niobium-tantalum targets over the Thambani Massif, and in nearby areas such as the Little Ngona river between the ridges and near Chikoleka village in the far north of the licence areas.
Airborne radiometric and magnetic surveys
In 1984 and 1985 Malawi’s Geological Survey Department (GSDM) compiled and published total field aeromagnetic survey data at 1:250,000, 1:100,000 and 1:50,000 scales covering the whole of Malawi. The data were acquired by Hunting Geology and Geophysics under contract to the United Nations (Project MLW/ 80/030) and were obtained from fixed wing and helicopter aeromagnetic surveys.
Country-wide radiometric data was also acquired by Hunting in 1984 and published by the GSDM as a series of 1:250,000, 1:100,000 and 1:50,000 scaled maps. The maps show total counts, uranium, potassium and thorium counts and ternary colour plots, available at 1:100,000 and 1:250,000 scales.
The Thambani area was one of six key areas subject to subsequent geological ground investigations and considered to have potential for economic uranium mineralisation.
An airborne magnetic survey revealed a strong, thin anomaly along the crest of the East Ridge. A wider magnetic anomaly occurs along the West Ridge. It appears that the radiometric uranium highs and the magnetic highs occupy mutually exclusive zones.
Ground radiometric survey
A systematic ground radiometric survey completed by Mkango confirmed and detailed two distinct uranium anomalies, occurring along the East Ridge and at the western foot of the West Ridge. A strong uranium anomaly, measuring approximately 3 km by 1.5 km, occurs along the length of the Thambani East ridge. A second uranium anomaly, measuring approximately 1.5 km by 0.4 km, occurs at the foot of the West Ridge.
In 2013, Mkango completed a sampling programme across the Thambani Massif primarily focused on two sites of historical uranium exploration, known as the Chikoleka and Little Ngona targets. An initial set of nine historical trenches, selected on the basis of anomalous ground radiometric results, were cleaned, re-examined and sampled across profiles from soil/overburden into bedrock. Some outcrop was also sampled on the East Ridge.
In 2017, Mkango revisited the trenches at Little Ngona and Chikoleka and carried out new work on the East Ridge and at the foot of the West Ridge. The main objectives of the programme were: to confirm the grades of previously identified high grade mineralisation at the Little Ngona target; to ground-truth new geophysical targets; and to complete further reconnaissance sampling along the East and West Ridges.
In 2019/2020, Mkango carried out a lithogeochemical sampling program on outcrops within radiometric anomalies on the East Ridge. The aims of the sampling were to better delineate the mineralised zones and to localise future drill sites to test the downdip extension of surface mineralisation. Field observations and assay results suggest that mineralisation occurs in zones that are conformable with the gneissic banding; this indicates potential for U-Ta-Nb mineralisation along a strike length of >3km.
Ten new trenches were excavated in 2019, including a location at the foot of the West Ridge where a small pit excavated in 2017 yielded the two highest-grading samples. The median values in the table below show that grades in the fresh rock tend to be higher than in the weathered rock in the trenches, suggesting extensive secondary remobilisation of the elements of interest. The scatterplot of uranium versus niobium below, limited to 5,000 ppm U and 9,000 ppm Nb for clarity, confirms the association between U and Nb-Ta and displays two trends; the steeper trend represents rock samples while the other trend represents trench samples.
Mkango is currently evaluating strategic options including opportunities for joint ventures and other potential avenues to add shareholder value to these prospects. The down-dip extension of surface Uranium-Tantalum-Niobium mineralisation on the East Ridge is currently being investigated further to locate targets that could potentially be drilled and tested from a series of collars sited downslope of the mineralised surface zones.
Zircon is abundantly visible in the nepheline syenite gneiss and in weathered veins in the trenches. Large crystals of zircon commonly occur as float in the soils. Corundum and columbite occur in pegmatite dykes in the north of the licence and also occur as float in the soils. Industrial corundum was commercially mined in the area during the 1930/1940’s.