How do carbonatites form deposits of niobium?

Crystal of pyrochlor (Wikipedia), the main ore mineral of niobium.

Niobium in carbonatites

Carbonatites are the major source of the critical metal niobium (Nb) which is used to strengthen alloys of iron and other metals. Nb-alloys are used in jet engines, rockets, and in structural components of buildings and other large constructions. It is also has superconducting properties with applications in particle accelerators, MRI scanners and NMR equipment. The main ore-mineral of Nb in carbonatites is pyrochlor [(Na,Ca)2Nb2O6(OH,F)], but little is known about the compostional or pressure and temperature conditions under which it can form during crustal evoution of carbonatite magmas. This project will use techniques of high pressure experimental petrology to investigate the phase relations of pyrochlor in carbonate-melt systems, in order to constrain the optimal conditions to form economic deposits of Nb. The student will perform piston-cylinder and 1 atm experiments at RSES and use electronprobe microanalysis, LA-ICPMS and other microanalytical techniques to characterise experimental products.