Talaxis, a subsidiary of Noble, will acquire up 75% of Lancaster Exploration, which holds the licence, and up to 49% of Maginito, a downstream rare earths business.
Rare earths such as neodymium alloy powders are used in magnets expected to be used extensively in electric vehicles.
Talaxis already has a 20% stake in Lancaster following an investment of £5mln in January.
That money will fund a drilling programme with a resource estimate scheduled by the end of the year.
At that point, Talaxis can increase its stake in Lancaster to 49% through investing a further £7mln with an option to go up to 75% once a feasibility study is complete.
The feasibility study is expected to be completed by end 2019.
If Talaxis exercises its option, Mkango will retain a 25% interest, free carried to production.
Maginito will also receive a further £1mln once a second phase of R&D work is completed, which will takes Talaxis’ stake to 49%.
Daniel Mamadou, an executive director of Talaxis said: "As the market for permanent magnet technology continues to grow rapidly, access to reliable sources of neodymium becomes key.”