Critical metals in tin deposits

Simplified geological map of southeastern Australia, showing locations of granitoid intrusions (from Hong et al. 2017 Gondwana Research 46; 124-140)

Cassiterite is the main ore mineral for tin (Sn) and is associated with many granitoid intrusions in eastern Australia, often providing economic Sn deposits. As well as containing Sn as the essential major element, cassiterite frequently contains wt% levels of the critical metals niobium (Nb) and tantalum (Ta), and these are generally not recovered during metallurgical refinement of tin-ore to tin metal. Nb is an important additive to some types of steel and heat resistant “super-alloys", and is currently mostly recovered from carbonatites. Ta is used in steel for surgical and dental instruments and in some electronic components.

This project will compile geological, geochronological, petrological, and geochemical data from granites and from key cassiterite occurrences in the Paleozoic eastern Australian granitic intrusions. The minor and trace element abundances in cassiterite will be precisely determined using the electronprobe microanalysis and LA-ICPMS techniques and combined with the geological, geochronological and other data to establish patterns in, and controls on, the abundances of Nb and Ta in different granitoid occurrences. A further key aspect will be to examine current methods for the metalurgical extraction of Sn from cassiterite ore, and to use experimental petrology to explore possible new approaches to the extraction of Nb and Ta (and other critical metals) from the cassiterite, using carbonate-fluoride fluxes to partition these metals into the melt and leach them from the cassiterite.