Speewah Dome, Kachana Station, Wyndham-East Kimberley Shire, Western Australia, Australiai

Regional Level Types
Speewah Dome	Dome
Kachana Station	Station (farming)
Wyndham-East Kimberley Shire	Shire
Western Australia	State
Australia	Country

The prospects are 110 kilometres south-west of Kununurra, and 30 kilometres west of the Great Northern Highway, centred on the Speewah Dome antiform.

Fluorite was first recorded in the area in 1905, and described by government geologist Blatchford 1912. A long list of companies explored the area for minerals in the second half of the Twentieth Century including Planet Gold NL, Pacific Mines Ltd, Whim Creek Consolidated, Uranium Consolidated, Shane Holdings NL, Gem Exploration and Minerals Ltd, Mining Advisers Pty Ltd, Stafford Holdings, Western Mining Corporation, and Elimina. Most information is about fluorite, although other mineral prospects are also in the area. Great Boulder Mines and North Kalgurli Mines discovered most of the fluorite prospects around 1972. A company called NiPLATS took over the tenements in 2002 under the name Speewah Metals.

Martins Silver-Lead (Durack) Mindat locality for base metals is listed separately on Mindat at the northern extent of the mineralised area.

There is no Speewah prospect as such, the name refering to several named prospects on the Speewah Dome. Fluorite is found associated with the north-south trending Central Fault Zone. Fluorite is also found to the east along the south-west to north-east trending Kings River Fault Zone. Generally described as narrow near vertical fluorite veins of variable width in shear zones, locally flanked by chloritic altered lower grade material in stockworks, and stringer veins. The fluorite is grey or white, or weathered to pale green.

There are four main areas of fluorite mineralisation named Main, West, North-West and Central, which will be listed separately. The veins contain 20-80% fluorite, with quartz, sometimes barite, and silicified country rock fragments. Chalcopyrite is commonly associated with wall rock stringers and stockworks. Fourteen fluorite veins have been discovered in total. These are named as A to G, G Cross, East, South, West, West Extended, North and Central. Most exploration has focussed on the A and B veins, listed on Mindat under 'Main' sub-heading.

Further, vanadium is found both directly west and east of the Central Fault. On the west side, is the northern most Red Hill deposit, then Fig Tree Yard prospect and Junction prospect in the south. East of the Central Fault is Magnetite Valley, Buckmans deposit, and the Central Hill deposit being the southern most on this side of the fault. Individual deposits strike between 5.5 kilometres to 8 kilometres and are up to 2 kilometres wide.

Some base metal (copper, gold, silver and lead) prospects are also found on the Speewah Dome, including Todhunter (Cu, Au) on its western edge, East Dome Cu, then along the Central Fault are Blue (Pb), Willmott (Pb), West Vein/Ridge (which also hosts fluorite), and Yungal (from north to south). Further base metals have been found at G Vein and B Vein along the Kings River Fault.

Fluorite resources are estimated at 6.7 mt at 24.6% CAF2. The fluorite veins associated with the Kings River Fault are part of a structurally controlled epithermal system, with base metals, gold and silver. In 2008-2009 drilling beneath these fluorite veins revealed chalcopyrite associated with hematite altered breccias. Prior exploration revealed gold, copper, lead and silver at Speewah in quartz veins and gossans at the surface, located along faults lines.

There is extensive vanadiferous titano-magnetite bearing gabbro at Speewah. The company states the titanium/vanadium deposit is the largest in Australia at 4.7 billion tonnes at 0.30 V2O5 and 2% Ti. The mineralised layer is flat-lying, 120 metres thick, with extensive outcropping on the surface. Within the vanadium layer is a thin 20cm thick zone of PGE (platinum and palladium). The vanadium is disseminated titano-magnetite amounting to 25% of the rock mass of the gabbro unit, covered by thin soil. The gabbro dips at 4 degrees from the centre of the dome, and the mineralised unit is up to 120 metres thick.

The Speewah Dome is on the western margin of the Halls Creek Mobile Belt, separated from the Kimberley Block by the regional Greenvale Fault Zone. This zone at Speewah hosts fluorite and barite deposits, basalt feeder vents and carbonatites. The Speewah Dome is elongated north-south, 50 x 30 kilometres with a core of Hart Dolerite. This rock is a composite intrusion of dolerite, gabbro, magnetite bearing olivine gabbro and more felsic units. The Hart Dolorite is one of the largest mafic complexes in the world. Carbonate dykes and plugs are associated with fluorite mineralisation.

Specimens from the area have not been seen, and with only drilling taking place, is un-explored. The Western Australian Museum recently collected material from the area, but the specimens are locked away in their warehouse in Perth. A few photographs on the company website show the usual secondary copper suspects of azurite, malachite and chrysocolla, and massive fluorite.

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References