The Northern Territory contains Australia’s largest undeveloped phosphate resources, with very large sedimentary phosphorite deposits defined in the Georgina Basin. This includes the deposits at Wonarah (on the Barkly Highway) and Ammaroo (east of Barrow Creek), which together contain resources of around 2 billion tonnes of phosphate rock. These large deposits in the central Georgina Basin are middle Cambrian in age (510 Ma) and form part of a regional phosphate-rich stratigraphic interval that extends over 500 000 km2 in the NT and into western Queensland. Avenira Ltd’s Wonarah phosphate deposit, which occurs in the Cambrian upper Gum Ridge Formation or basal Wonarah Formation, contains Indicated and Inferred resources (at 10% P2O5 cut-off) of 842 Mt at 18% P2O5. Rum Jungle Resources Ltd’s Ammaroo project, 80 km east from the Alice Springs–Darwin railway. contains total Indicated and Inferred resources of 1.145 Bt at 14.6% P2O5 (at a 10% P2O5 cut-off). A third significant phosphate resource is located at the Highland Plains deposit (Phosphate Australia Ltd) near the Queensland border.
Sedimentary phosphorite mineralisation has also been recorded in the McArthur Basin (Karns Dolomite), Amadeus Basin (Stairway Sandstone) and Money Shoal Basin (Moonkinu Formation).
Phosphate-rich tectonic-related breccias are present in the vicinity of Batchelor (eg Geolsec deposit) within the Pine Creek Orogen. Prosphate is also an important component of the Nolans Bore apatite-hosted rare earth elements deposit in the Arunta Region near Aileron.
Significant potential for potash resources occurs within brines in aquifers associated with salt lakes in central Australia as well as in evaporitic deposits within the Neoproterozoic to Palaeozoic Amadeus Basin. The Karinga Lakes potash project, approximately 200–300 km southwest of Alice Springs, contains hundreds of salt lakes that contain brines enriched in salts containing potassium, magnesium and sulfate. These have potential for the production of potassium sulfate (SOP) and potassium magnesium sulfate (schoenite). The current resource at Karinga Lakes comprises 8.4 Mt of SOP which equates to a maximum schoenite resource of 19 Mt.