The Wilga base‐precious metals deposit, Benambra, Victoria, Australia

Abstract

ABSTRACTWilga is one of several Au‐bearing volcanogenic massive sulphide deposits localized within Silurian felsic volcanics of the Lachlan Fold Belt of NE Victoria. Exploration has delineated a resource of 3.7 Mt averaging 3.4% Cu, 5.5% Zn, 0.4% Pb, 31 g/t Ag and 0.5 g/t Au within a lensoid‐shaped sulphide body which strikes NE, dips NW and occurs at a depth of 50–160 m below surface. This body has maximum dimensions of 470 m strike, 350 m down‐dip and 37 m true width delineated by 59 surface diamond drill holes and an exploration adit with 40 underground diamond drill holes.There are two main types of mineralization: Stratiform massive sulphides, (mainly pyrite, low‐Fe sphalerite, variable chalcopyrite and minor galena with very minor silica/dolomite gangue) and Stratiform chloritic sulphides (mainly chalcopyrite, with subordinate pyrite and sphalerite, in a gangue of chlorite and minor dolomite).The deposit is layered with at least 6 distinct stratigraphic horizons/cycles of mineralization each characterized by a Cu‐rich base and Pb‐(Zn)‐Au‐As‐rich top. Facies variations are locally rapid.Economically the deposit consists of 3 sub‐lenses of roughly equal tonnage: a Cu‐rich central lens of Chloritic Sulphides (av. 5.9% Cu, 3.6% Zn, 0.3% Pb, 32 g/t Ag and 0.2 g/t Au) between upper and lower lenses of Zn‐rich Massive Sulphides (av. 1.8% Cu, 6.7% Zn, 0.5% Pb, 31 g/t Ag and 0.7 g/t Au).Gold mineralization, locally up to 7 g/t over 6 m, shows a strong spatial association with Pb, (Zn) and As in pyritic massive sulphides.