Gold-bearing quartz veins occur in two zones along a NW-SE trend with an 8 km strike length. The veins are steeply dipping, vary in thickness from 0.30 to 2 metres, and can extend for 100’s meters along strike. The vein systems consist of bifurcating and anastamosing quartz veins, and are invariably associated with strong shearing in the host gabbros.
Underground mapping at Ginduša demonstrates that the quartz veining is controlled by two shear orientations – 315º to 330º and 260º to 280º, with the latter being associated with the highest gold grades and cross-cutting the regional NW-SE trend. In the H-10 stope the controlling structure strikes approximately E-W for about 100 metres and dips steeply to the north. The high grades occur in lenses – probably controlled by dilation zones on the controlling structure. Shoots of high-grade gold-in-quartz mineralization occur in dilation zones on the controlling planar structure, and it is expected that these structure will plunge to depths beyond that already mined (approximately 90 metres below surface).
Talc-carbonate alteration of the gabbro is common, Fe-carbonates are locally developed in the altered gabbro, and sericitisation restricted to the immediate contact with the quartz.
The vein quartz is generally milky and cryptocrystalline, and contains disseminated fine-grained pyrite. Coarse pyrite and chalcopyrite heal fractures in brecciated vein quartz. Telluride, stibnite and arsenoyprite are also reported in the literature. Calcite occurs in some of the quartz veins, as well as a late stage of calcite veins.
Quartz-vein hosted gold mineralization in altered (talc-carbonate) gabbro host rock associated with multiphase deformation along a regional shear structure is comparable to the Mother Lode and other gold deposits in the Sierra Nevada, California.