Greenbushes, Western Australia

Summary

Lithium Australia NL (‘LIT’) holds 100% equity in the Greenbushes project, located 200 kilometres (‘km’) south of Perth, the capital of Western Australia. It consists of four granted exploration licences, plus an additional five exploration and seven prospecting licence applications (see Figure 1). The tenement holding is adjacent to the world’s largest lithium mine, the Greenbushes operation of Talison Lithium Australia. That mine currently produces about 40% of global lithium supply. The LIT tenure contains some 50 km of the highly prospective Donnybrook-Bridgetown Shear, which controls the pegmatite emplacement at Greenbushes.

Figure 1: Greenbushes project tenure.

Geology

Tin was discovered at Greenbushes in 1886 and by 1890 tantalite was being mined from alluvial ore. Dredges were used to mine placer deposits in the 1960s and ’70s, after which the focus became open-pit mining of weathered pegmatites. With fluctuations in the tantalum markets, currently only lithium minerals are mined from the open pits (see Figure 2).

At Greenbushes, the pegmatite swarm was intruded close to, and aligned with, the north to north-northeasterly-trending Donnybrook-Bridgetown shear zone, a regional lineament about 150 km long in the Archean Balingup Metamorphic Belt. The pegmatites at Greenbushes are uncharacteristically fine-grained and sheared due to the association with the Donnybrook-Bridgetown shear zone. The LIT tenements contain some 50 km of this highly prospective structural lineament, which is characterised by deformed gneiss, orthogneiss and migmatites.

Figure 2: Greenbushes (Cornwall) open pit looking south, with pegmatite exposures in the eastern pit wall.

Exploration

Using a recently acquired open-file geophysical and geological data package prepared for LIT by Southern Geoscience Consultants, LIT is redefining the geological and structural setting of the Greenbushes project area, with a view to generating a series of priority targets for geological reconnaissance and sampling. This work will be low-impact, incorporating real-time lithium assays using laser-induced breakdown spectroscopy and field portable X-ray fluorescence to help delineate more prospective structural trends for further work programmes.