Regional Geology

The Project covers most of the Gum Creek Greenstone Belt, situated within the Southern Cross Province of the Youanmi Terrane, a part of the Archaean Yilgarn craton in Western Australia. The Gum Creek Greenstone Belt forms a lensoid, broadly sinusoidal structure about 110km long and 24km wide, dominated by volcanic and sedimentary sequences and surrounded by intrusive granitoids which contain rafts of greenstones.  The margins of the belt are typically dominated by contact-metamorphosed basalts and banded iron formations.

The greenstone sequence is relatively simple, with three broadly continuous major geological units occupying a large north-south synclinorium.  The lowest unit consists of a sequence of interbedded banded iron formation and mafic and ultramafic volcanics overlain by ferruginous shales, shales and thin cherts.  The central unit consists of a sequence of basalts and felsic volcanics, contemporaneous dolerites, and lesser ultramafic volcanics and interflow sediments.  The central unit has been intruded by differentiated gabbroic sills which range in composition from ultrabasic through to pyroxenite to gabbro.  The uppermost unit consists of shales, black shales, siltstones and minor cherts, with rare conglomerates and dolostones.  Late stage, generally massive granitoids intrude along the length of the belt.

Several early phases of tight to isoclinal folding have affected rocks of the lower domain.  Most fold axes now exhibit a general north-south trend.  The whole belt has been folded about tight north-north-west axes, producing two synclines separated by a narrow anticline in the central domain.  The western syncline appears to be doubly plunging suggesting late open folding under an east-west stress regime.

Complex faulting is present throughout the Gum Creek Greenstone Belt, with many lithological units being fault bounded.  Prominent deformation also occurs as regional-scale north-northwest trending ductile shear zones.  These zones occur in close proximity to gold occurrences at Bolger Well, Gidgee, Victory Well, Tokay and Wilsons.

geology-map

Five main styles of mineralisation are recognised in the area:

 

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