Sampling at dual-listed explorer Mkango Resources’ Thambani heavy minerals project, in southern Malawi, supports the notion that Thambani has significant multicommodity potential, says president Alexander Lemon.
He noted in a May statement that the uranium results were highly encouraging, with assay results from 85 rock grab samples returning values of 3.3% triuranium octoxide (U3O8), but equally positive are the tantalum values, at 1.9%, and those of niobium, at 6%.
Thirty-five of the samples graded above 500 parts per million (ppm) U3O8 and 24 graded above 1 000 ppm U3O8.
The programme was aimed at confirming previously identified high-grade mineralisation at the Little Ngona target, ground- truthing new geophysical targets and completing further reconnaissance sampling along the East Ridge and West Ridge.
New areas of high-grade uranium, tantalum and niobium mineralisation were identified at the foot of the West Ridge and on the East Ridge. Most significantly, a radiometric high at the foot of the West Ridge yielded two of the four highest- grade samples of this phase of exploration.
Mkango is now evaluating strategic options for Thambani, including opportunities for a joint venture or spin-off of the project, as well as other potential avenues to create value.
In March, Mkango reported that it had completed preparatory work to further advance Thambani.
This followed the signing of a collaboration agreement with global supply chain manager Noble Resources International and a £450 000 placing in December.
Mkango’s exploration programme at Thambani, in the Mwanza district, started in March, following management site visits earlier in the year. The programme comprises a follow-up of the results of the World Bank’s airborne geophysical survey, which were reported in 2016, as well as the results of previous exploration programmes completed by Mkango.
In July 2016, Mining Weekly reported that a geophysical survey, which formed part of a $25-million World Bank-funded nationwide high-resolution airborne geophysical programme, had confirmed significant radiometric and magnetic anomalies in the Thambani region.
The airborne geophysical component of the project comprised high-resolution airborne geophysics at 250 m spacing; uranium, potassium and thorium radiometric surveys; magnetic and gravity surveys; and raw data production.In March, the company noted that t
he current exploration programme would include, but was not limited to, further mapping of the area, soil and rock chip sampling, trenching and ground truthing of new geophysical anomalies.
While uranium – as well as associated tantalum and niobium – is the primary focus of the exploration programme, Mkango will also evaluate the licence for its lithium potential. The Thambani licence area is host to pegmatite occurrences, which can be a potential host rock for lithium. Historical reports also refer to the presence of a lithium mineral in the licence area; however, these need further geological investigation to determine the significance. Mkango Resources expects all costs associated with the work programme to be covered by existing cash resources.
“The market has clearly seen renewed interest in uranium projects in recent months, following moves by Kazakhstan to cut production together with the increasingly apparent lack of supply for new rectors that will be brought on line over the next five years in countries such as India and China . . . We believe that we will enhance value for our shareholders in the near term by pushing ahead with a clearly defined, low-cost exploration programme,” said Makango CEO William Dawes in February.
The 468 km2 Thambani exploration licence was originally granted by the Malawi Minister of Natural Resources, Energy and Environment in 2010. In 2013 and 2015, the government of Malawi granted further two-year renewals for the licence and, at the second renewal, the company requested a reduction in the licence size to 136.9 km2.
Mkango’s exploration activities, to date, include the acquisition of satellite imagery for the licence area, systematic ground radiometric surveys to confirm and detail previously known airborne anomalies, reconnaissance geological mapping and lithogeochemical sampling programmes. The work has identified several potential uranium and associated niobium and tantalum targets over the Thambani massif deposit, which is mainly composed of nepheline- bearing syenite gneiss, forming two prominent ridges, known as the Thambani East and West ridges.
A systematic ground radiometric survey previously completed by Mkango revealed two distinct uranium anomalies across the Thambani East and West. A strong uranium anomaly, measuring about 3 km × 1.5 km, occurs along the length of the Thambani East ridge, with a north–south trend, and a second uranium anomaly, measuring about 1.5 km × 0.4 km, occurs on the West ridge, along the western contact of the nepheline-bearing syenite body with the biotite- hornblende gneisses.
Mkango completed a trenching 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 trenches, selected on the basis of anomalous ground radiometric results, have been re-examined and geochemically sampled across profiles from soil/overburden into bedrock.
The first set of assay results from 142 soil and rock chip samples returned variably anomalous niobium and tantalum values in most trenches, as well as U3O8.
Preliminary mineralogical studies carried out on six rock samples from the Little Ngona River and Chikoleka targets indicate that pyrochlore group minerals, mainly betafite, are the principal carriers of uranium, niobium and tantalum for these samples.