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The geological, geochronological and geochemical architecture of the Speewah Dome

East Kimberley, WA

This study will provide new insights into the geological, geochronological and geochemical architecture of the Speewah Dome, East Kimberley, Western Australia. This area is poorly documented and hosts significant potential for a wide range of mineral systems. 

The Speewah V-Ti-Fe deposits are a series of orthomagmatic, vanadiferous titanomagnetite-bearing gabbro sills within the Speewah Dome, a doubly plunging anticline situated on the eastern margin of the Kimberley Block in northern Western Australia. The sills make up an intrusive complex containing newly identified gabbro units (Spotted Magnetite Gabbro, Disseminated magnetite Gabbro, Pegmatoidal Gabbro) and granophyre units (Coarse Felsic Granophyre, Mafic Granophyre), which may be part of the Hart-Carson Large Igneous Province. Vanadium mineralisation occurs within disseminated titanomagnetite crystals at up to 3.98 wt% V2O3, with greatest titanomagnetite concentration (up to 20%) in the basal 15-25m of the Disseminated Magnetite Gabbro. The deposits also contain sulphide-related Platinum Group Elements (PGE), gold and copper mineralisation similar in style to mineralisation hosted within the Stella layered intrusion in South Africa. Emplacement occurred via the intrusion of lithospheric and aesthenospheric magmas into Speewah Group sediments, preferentially eroding siltstone units during emplacement. High oxygen fugacity within a well-endowed magma allowed for early crystallisation of titanomagnetite and incorporation of V3+ into the crystal structure (substituting for Fe3+). It is thought these deposits formed in a post-collisional or extensional environment, after the Kimberley Block and Sturt Block had joined to form the North Australian Craton. work is in progress to further define  geological, geochronological and geochemical architecture of the area.