The Groote Eylandt manganese mine has been in operation since 1965, and has produced more than 115 million tonnes of manganese ore and concentrate to June 2018. The mine is operated by the Groote Eylandt Mining Company Pty Ltd (GEMCO), which is majority owned by South 32 Ltd.
The ore is mined by shallow open-cut mining methods and is transported by road to a nearby port. Production in 2017/18 totalled 5.66 Mt of manganese ore. The deposit comprises oolitic and pisolitic sedimentary manganese within the Cretaceous Carpentaria Basin.
The Bootu Creek mine is 110km north of Tennant Creek and commenced operation in 2005. The mine is operated by OM Manganese Ltd, a subsidiary of Singapore-based OM Holdings. In 2018, production of manganese concentrate (lumps and fines) totalled 814,040 t at 35.77% Mn.
A Tailings Retreatment Plant at Bootu Creek is expected to be commissioned in 2019 and will produce ~250,000 tonnes of manganese fines per annum for eight years. The deposit is a hydrothermally modified sedimentary deposit hosted in Palaeoproterozoic rocks of the Tomkinson Province.
In January 2019, an exploration licence covering part of Winchelsea Island, off the northwest coast of Groote Eylandt, was granted to the Winchelsea Mining Pty Ltd, which is a joint venture between the Anindilyakwa Advancement Aboriginal Corporation (AAAC) and AUS China International Mining.
Further potential for sedimentary hosted manganese occurs in relatively unexplored regions of eastern Arnhem Land, along the western margin of the Carpentaria Basin, where manganese was precipitated during a Cretaceous marine regression on coastal terraces and troughs.
Sedimentary or secondary manganese deposits are also present in the Amadeus Basin (for example, Wangatinya), McArthur Basin (for example, South Rosie Creek), Georgina Basin and South Nicholson Basin.