PERAMA HILL (GREECE)

Perama Hill is a high sulfidation epithermal gold deposit hosted within sandstone, conglomerate and andesite of the Petrota graben in NE Greece. The deposit is bounded by the Eastern Graben Fault, a major structure that separates the Oligocene age sedimentary and volcanic rocks to the west from Mesozoic metamorphic basement rocks to the east. Almost 80% of the gold is hosted within the sandstone and the remaining 20% occurs in the underlying andesitic rocks. In the central portion of the deposit the ore is oxidized to at least 100m whereas on the margins the oxidation thins out to 15 to 20m. The epithermal system evolved from an early stage of silica-pyrite and argillic alteration to later deposition of quartz-barite veins and stockworks. Silicification was developed mainly in the sandstones and the alteration is composed of microcrystalline quartz, kaolinite, pyrite, and barite. In the andesite, silicification is controlled by potential feeder-structures to the overlying mineralization, and the alteration is characterized by kaolinite-illite altered andesite breccia clasts surrounded by a pervasive silicified matrix.