Wonarah Phosphate Mine (Wonarah Phosphate Deposit), Wunara, Barkly Region, Northern Territory, Australia

Latitude & Longitude (WGS84):	19° 59' 40'' South , 136° 34' 0'' East
Latitude & Longitude (decimal):	-19.9947175878, 136.566897919

One of the largest phosphate deposits in Australia. Located 150 kilometres west of Camooweal, and 75 kilometres east of the Barkly Homestead Road House. The semi permanent small Wunara indigenous community is 10 kilometres to the east. Wonarah is divided into two deposits called Main, 5 kilometres south of the Barkly Highway, and Arruwarra, a further 5 kilometres to the south south-west.

Measured and Indicated Resource 300 Mt at 18.2% P2O5 (10% cut-off). Inferred Resource 542 Mt at 18% P2O5.

The deposit was discovered in 1967 by geologist P. Howard for the IMC Development Corporation, who explored it until 1970. CRA Exploration Pty Ltd explored further country to the south during the mid 1980's. The leases were acquired by Rare Earths and Minerals Pty Ltd, and Pilbara Chemical Corporation NL, then Indo Mines Ltd and Rio Tinto held a joint venture over the deposits from 1997-2002. Minemakers Australia Pty Ltd purchased the leases in 2006.

Should the world be willing to pay more for fertilizer, the site could warrant a large scale, multi decade phosphate mine. The plan is for 19 shallow pits in the Main Zone, and 4 at Arruwarra, with two crushing and screening plants, the material then transported by road to Tennant Creek. A stage 2 IHP plant has been looked at for the site. This involves the material being heated in a kiln to release the P4O10 gas, passing to a hydrator where it is combined with water to form phosphoric acid at 70% P2O5.

The deposit is located in the Lower Cambrian Georgina Basin, where most of Australia's potentially economic phosphate deposits are found. The country rock in the Wonarah area contains crystalline vuggy dolomite, strongly phosphorous grey dolomite/limestone, with an upper zone of coarse coquinite limestone, and fossilferous algal limestone, siltstone, chert and phosphorite of various colours including tan, off-white, brown, grey, khaki, chocolate, red and mauve.

The Main Zone contains a basement of the Peaker Piker Volcanics, the upper parts extremely weathered, with a ferriginous and manganese duricrust. Overlying this is the Upper Gum Ridge Formation sub-divided into four units: 1) basal undifferentiated sedimentary transitional unit 2) chert breccia phosphorite 3) mudstone phosphorite 4) convolute phosphorite. The transitional phosphorite is 4-8 metres thick, containing clay rich mudstone, siltstone, minor phosphorite, dolomite, sandstone, and basal epiclasts. The chert breccia phosphorite is up to 70% dark grey angular chert, in a high grade phosphorite matrix, friable to strongly indurated, 2-6 metres thick. This is in sharp contact with the overlying main economic unit of mudstone phosphorite of yellow to pink, friable to strongly indurated mudstone phosphorite, 1-10 metres thick. Over this the convolute mudstone, is weakly phosphatic clay rich mudstone.

The Arruwarra deposit shows a basement of the Peaker Piker volcanics. Above this is the Thorntonia Limestone of karst dolomites and dolostones at the south-east and southern margins of the deposit. The transitional phosphorite zone is the main economic unit at the deposit, being strongly indurated phosphorite mudstone averaging 2 metres thick. Overlying this is 1 to 3 metre mudstone, siltstone and phosphorite. The chert breccia phosphorite is absent, with instead mudstone phosphorite 1-6 metres thick, with the convolute phosphorite also absent.

Mineral List

4 valid minerals.

Rock Types Recorded

Entries shown in red are rocks recorded for this region.

References

External Links