Mount Gibson Iron Ore Mine (Extension Hill D50), Mount Gibson Conservation Reserve, Retaliation Goldfield, Yalgoo Shire, Western Australia, Australiai

Regional Level Types
Mount Gibson Iron Ore Mine (Extension Hill D50)	Mine
Mount Gibson Conservation Reserve	Mountain
Retaliation Goldfield	Ore Field
Yalgoo Shire	Shire
Western Australia	State
Australia	Country

Mining commenced here in 2011 by the Mount Gibson Iron Company. It is located 30 kilometres south-west of Paynes find, and can be seen to the east of the Great Northern Highway on the western slopes of Mt Gibson. In fact the highway had to be diverted to accommodate the mine. The deposit has a strike length of 8 kilometres.

The banded iron formation has alternating bands of magnetite and microcrystalline quartz (chert), with far lesser carbonaceous and iron silicate rich shale partings/layers, and thin fine grained tuff bands. The thickness of the banded iron formation is 100 metres, but this can increase to up to 450 metres due to slumping, faulting and isoclinal folding. The banding shows variable thickness and is generally parrallel except where the above processes have taken place. Bands range from a few microns to several cms thick. Rare iron rich carbonaceous black shale bands can be up to 30 cms thick. Chert bands are dark grey to black due to the fine grained inclusion of magnetite.

The deposit shows an unweathered magnetite oxide-facies banded iron formation zone, and an upper up to 100 metre thick oxidised weathered zone outcopping at the surface as a steep sided ridge along the Mt Gibson ranges.

In the unweathered zone magnetite mesobands range from under 1cm to over 10cms. Coarse grained magnetite is fringed with dusty fine grained magnetite near contact with the chert. Hydrous iron silicates greenalite, minnesotaite, grunnerite, stilpnomelane and rarely chlorite fill the spaces between the magnetite grains.

In the weathered zone above this, is found high grade hematite deposits striking for 1 kilometre within the banded iron formation. This was formed by either supergene leaching of cherty banded iron formation, or by hypogene replacement of chert by carbonates, with subsequent supergene leaching of the carbonates and accessory minerals, and oxidation of the magnetite to hematite. Carbonate banded iron formation in this zone forms a magnetite-goethite ore.

Other Regions, Features and Areas containing this locality

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