Ammaroo Phosphate Deposit, Ammaroo Station (Amaroo Station), Sandover, Barkly Region, Northern Territory, Australiai

Regional Level Types
Ammaroo Phosphate Deposit	Deposit
Ammaroo Station (Amaroo Station)	- not defined -
Sandover	- not defined -
Barkly Region	Region
Northern Territory	Territory
Australia	Country

Largest phosphate resource in Australia. Occupying a portion of the southern Georgina Basin. (See also Wonarah Mindat locality for the northern Georgina Basin). The Ammaroo deposit covers an area 40 kilometres long, with a further smaller deposit called Ammaroo South. Discovered in the year 2000.

The JORC estimated resource is 1.135 billion tonnes P2O5 averaging 14% P2O5 (with a 10% cut-off). The $300 million first stage of the project is expected to produce one million tonnes a year.

The phosphate is found in the Middle Cambrian Arthur Creek Formation, consisting of fossiliferous organic rich calcareous and dolomitic siltstone, silty limestone, and silty dolostone. The phosphate deposits are at a shallow depth, flat lying, deeply weathered and leached, leaving a whitish to yellow-brown siltstone and claystone, with some chert near the surface. In several areas are thin coquinites (limestone made from shell fragments), biosparite (limestone from biocasts or shells in sparry calcite cement), and various limestone varieties of the above.

The phosphate material has two distinct units. An anaerobic deeper dark grey-black finely pyritic calcareous and dolomitic siltstone, and calcareous mudstone, with an organic content up to 14%, increasing towards the base. The second and higher grade phosphate is an aerobic zone which is sub-tidal, fossiliferous, bioturbated, with a lower organic content. It is dark grey to black thinly laminated to wavy bedded calcilutite (limestone containing more than 50% transported carbonate grains-also known as cement stone), dolomite, and fine grained calarenite.

The leases were controlled by Nupower 2012, who became Central Australian Phosphate Ltd, then in 2013 Rum Jungle Resources took over the company. The company further changed its name to Verdant Minerals in 2016.

The company is inching towards opening a mine. The resource is large, at a shallow depth, needing little processing, requiring trucking to the railway 100 kilometres away, then by rail half a continent for export from Darwin. Demand for fertiliser is expected to increase. There has been plenty of promising prospects which have never got off the ground, although the chances for a multi decade mine here are better than most.

From a purely scientific, and curiosity view, is the copious marine fossils in the Arthur Creek Formation, including abundant faunal trilobites, brachiopods, hyoliths, sponge spicules, and shell material. The mine would be a blessing and curse. It opens the fossil beds for inspection, then gets taken away to be ground into fertilizer. It is hoped some arrangement can be made for a study, without making the mine uneconomic.

Mindat map is somewhat problematic considering the large area the deposit covers. The location 'Limestone Bore' has been chosen, as drilling has been noted as taking place near here.

Other Regions, Features and Areas containing this locality

References