OLYMPIAS (GREECE)

Olympias is a gold-rich polymetallic carbonate replacement deposit hosted in an interlayered sequence of feldspar-biotite gneiss and marble within the Paleozoic Kerdylia Formation of the Serbo-Macedonian Massif, NE Greece. It contains multiple lenses which together extend in a NNE direction for over 1.5 km, plunge 30 to 35° SW, and have an average thickness of 12 m. Two main end-member ore types are recognised; a base metal-rich ore type and a high arsenic-silica, high gold ore type. The latter typically occurs in the core of the ore lenses and is dominated by grey arsenian pyrite and arsenopyrite and subordinate galena and sphalerite with quartz-rich gangue. Gold grades are typically >10 to 30 g/t. The base metal-rich ore is characterized by variable pyrite, galena and sphalerite with lesser arsenian pyrite and arsenopyrite, and calcite-rich gangue. Gold grades are commonly in the range of 2 to 10 g/t. Both ore types locally contain spectacular bladed to dendritic arsenian pyrite and arsenopyrite with massive base metal sulphides. The Olympias deposit likely formed during the Late Oligocene to Early Miocene coincident with magmatism in the region.