Bynoe project – Northern Territory
In April 2016, Lithium Australia NL (‘LIT’) announced the grant of Mineral Exploration Licence 30897, located in the historic Bynoe pegmatite field in the Northern Territory, Australia.
The Bynoe project is located 50 kilometres (‘km’) south-southwest of Darwin, capital of the Northern Territory, and is close to infrastructure (see Figure 1). Despite the favourable location, exploration in the area has until recently been restricted and of narrow focus, with little work undertaken on lithium. The latest exploration has targeted spodumene (a lithium silicate) and lithium micas, and activity levels rival those of similar pegmatite fields such as Pilgangoora in Western Australia.
Geology and mineralisation
LIT’s Bynoe project lies within the Bynoe Pegmatite Field, part of the larger Litchfield Pegmatite Belt. Located along the western margin of the Palaeoproterozoic Pine Creek Orogen, the Litchfield Pegmatite Belt is almost 200 km long and has been intruded by a suite of highly differentiated granites. Known as S-type granites that originated from the partial melting of metasedimentary rocks, they are thought to be the source of the pegmatites.
Tin was discovered in 1886 at Leviathan Creek. Operations within the Bynoe Pegmatite Field exploited mainly surface tin deposits created by the weathering and erosion of the pegmatites. Higher grades were localised in the shallow regolith, leading to over 100 pegmatites being worked in the Bynoe field during that period. However, tin recoveries were disadvantaged through losses in the sluicing process as a result of the lodes being kaolinized. Production of small, varying quantities of tin continued from the Bynoe area through until 1908.
In 1979, exploration for tantalum and tin in the Bynoe district increased with the formation of a joint venture between Greenbushes Tin Ltd and Bayer AG of Germany. The partners established a trial concentration plant in 1983, but tin-tantalum prices prevailing at the time rendered the project uneconomic.
Only very recently has the possibility of significant lithium mineralisation at Bynoe been considered.
Proposed exploration, testing and development
Initially, LIT will undertake a desktop study of the Bynoe project, with a view to identifying and evaluating lithium mineralisation. Fieldwork will commence during the northern dry season, once surface water has dissipated and access is easier.