The Ore and Gangue Mineralogy of the Newly-Discovered Federation Deposit, Central NSW, Australia

The newly-discovered Federation deposit with a resource estimate of 2.6Mt @ 7.7% Pb, 13.5% Zn, 0.8g/t Au and 9g/t Ag lies 10km south of the Hera deposit within the Cobar Basin of the Lachlan Orogen. Located just north of the Erimeran Granite contact and between the Lower Amphitheatre Group and underlying shallow marine Mouramba Group Roset Sandstone, the host siltstones and sandstones have been brecciated, intensely silicified and chloritized close to mineralisation. Orientated in an overall east-northeast strike and with a steep south-southeast dip, the siltstones mainly comprise quartz, clinochlore, biotite and muscovite. Federation also has highly fragmented zones with breccia and vein-fill of calcite. Main ore mineralisation includes sphalerite and galena with lesser chalcopyrite, pyrrhotite, pyrite and very rare boulangerite. Mineralisation occurs within silicified veins and breccias of Zn-Pb sulfides which generally grade to moderate veining of sulfides with Pb and Cu dominant sulfides as well as minor veining of base metals associated with visible gold. Mineralisation throughout the deposit is fairly simple with a low diversity of minerals. Iron concentration varies throughout the deposit, decreasing towards the centre. Observations of massive sphalerite with gradations of red to honey-comb yellow indicate the transition from high Fe (7-10%) to low Fe (2-5%) within the coarse sulfide assemblages. Within the main mineralised corridor, fibrous amphibole inclusions within galena/sphalerite assemblages are observed at 251m as well as epidote associated with sulfides at 573m. Other ore associated gangue minerals include siderite, scheelite, magnetite, apatite and rutile.