Structural controls on the Cowarra gold deposit near Bredbo, southeastern New South Wales

Abstract

The Cowarra gold deposit is an epigenetic, structurally controlled, gold‐bearing sulfide vein system in a regional shear zone developed within isoclinally folded Ordovician turbidites. Gold occurs mainly in sulfide‐rich veins parallel to the axial cleavage or shears on fold limbs. There are seven sets of quartz veins, but they contain only minor gold. The mineralised shears lie within a zone of strong fold‐plunge variation, in the chlorite zone of a regional metamorphic complex, and to the west of the Bega Batholith. However, gold is not related to metamorphic outflushing, but more likely to sulfide‐rich fluids derived from depth during intrusion of I‐type granites of the Michelago Igneous Complex. The local control for sulfide veining was decompressional dilation of axial planar structures shortly after folding and shearing; this is unlike the structural control described for most deposits from this and similar terrains. Subsequent normal, strike‐slip and reverse fault movements in the shear zone develop...