Paraburdoo 4, Paraburdoo Iron ore mine, Paraburdoo, Ashburton Shire, Western Australia, Australiai

Regional Level Types
Paraburdoo 4	- not defined -
Paraburdoo Iron ore mine	Mine
Paraburdoo	Town
Ashburton Shire	Shire
Western Australia	State
Australia	Country

The source relates to a very specific part of this mine, which is west of the main hub, on a ridge surrounded on three sides by the loop of an ephemeral stream.

200 Mt at 63.5%Fe.

The deposit occurs as a south dipping sheet within banded iron formation of the Dales Gorge and Joffre Members. The reactivation of the 18E Fault, and development of south-west striking, steep south-west dipping 4E and 4EE normal faults, resulted in the preservation of the 4EE orebody below the 4E deposit, 400 metres below the surface.

There are three hypogene alteration zones being (1) distal magnetite-quartz-dolomite-stilpnomelane-hematite-pyrite (2) intermediate magnetite-dolomite-hematite-chlorite-quartz-stilpnomelane (3) proximal hematite-dolomite-chlorite-pyrite-magnetite.

North-west trending dolomite dykes intrude the 4E and 4EE faults, prior to the hypogene alteration. The hypogene fluid flow was focussed into north-west striking, steep south-west dipping 4E and 4EE normal faults, and reacted with the banded iron formation of the Dales Gorge and Joffre Members.

Ca rich 160-225 degree temperature brine interacted with magnetite-chert layers, transforming them to magnetite-quartz-dolomite-stiplomelane-hematite-pyrite banded iron formation, and producing the alteration assemblage.

Microplaty and anhedral hematite replaced magnetite in the intermediate zone, and formed the proximal assemblages. The intermediate and proximal zone had higher fluid temperatures at 250-400 degrees C, higher salinity, Ca-Sr rich brine, heated during its decent into the upper crust. The trapping of the fluid at various stages resulted in a wide range of temperatures up to 200 degrees C. The iron rich brine originally from evaporated seawater lost Mg and Na, gained Li and Ca through fluid interactions with volcaniclastic rocks and carbonate within the Wittenoom Formation.

The low salinity heated water lost some Na through wall rock interaction with plagioclase, possibly with the interaction with dolerite of the Weeli Wolli Formation overlying the Dales Gorge and Joffre Members.

After the hypogene alteration, low temperature (under 110 degrees C), low salinity water interacted with the banded iron formation leaving porous high grade hematite ore. Supergene alteration effected the orebody subsequently producing hematite-goethite alteration assemblages, with hypogene zones only remaining below the zone of weathering.

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References