Post-magmatic processes in carbonatitic systems

We are investigating the mineralisation and fluid processes that occur in carbonatitic magmas in the Chilwa Alkaline Province of Malawi and the potential for extracting precious elements.

Carbonatites are economically important as they often have high concentrations of:

• light rare earth elements (LREE)
• niobium (Nb)

Most of the world's production of LREE and Nb minerals are extracted from carbonatite-related complexes.

Magmatic processes

When a carbonatite magma rises up and intrudes into Earth's crust, a number of reactions take place. During and after emplacement, fluids pass from the magma into the surrounding rocks, creating an aureole of altered rocks known as fenites. 

Fenitised zones are expected to have low concentrations of LREE and Nb because these elements are considered to be poorly mobile. 

Current research

We are comparing two contrasting carbonatites in the Chilwa Alkaline Province of Malawi.

Study of the fenitised zones has revealed:

• LREE present at concentrations of up to 1,700ppm
• Nb enrichment

This suggests that these elements can be mobile in carbonatitic fluids, and that fenite aureoles could be future exploration targets for low grade, large tonnage LREE mining.