Porphyry and Hydrothermal Cu-Au Deposits: A Global Perspective

The Bor metallogenic district contains the three major producers Majdanpek, Bor and Veliki Krivelji, which have a combined production of more than 90 000 tonnes of copper and 4 tonnes of gold per annum. Total metal content for deposits discovered in the district exceeds 20 million tonnes of copper metal. In the Bor District the deposits are all of interpreted Upper Cretaceous age, related to calc-alkaline igneous activity, but they are highly variable in morphology and association. At Bor itself, andesitic sub-volcanics and extrusive rocks host deeper porphyry copper mineralisation, which passes into a stockwork through to high sulphidation enargite massive sulphides developed close to the palaeo-surface with 3 to 6% Cu. The whole mineralised system is exposed over 1500 m of depth extent in mine workings and exploration drilling, with both lateral and vertical zonation of alteration. The deposit contains significant gold. Veliki Krivelji, is only 5 km from Bor, but is a gold poor system. Here porphyry copper mineralisation relates to high level dyke swarms and skarns. Majdanpek is a world class porphyry deposit with around 1 billion tonnes (Gt) @ 0.6% Cu, 0.3 g/t Au, but is hosted in fractured basement gneisses intruded by narrow andesitic dykes which may relate to larger buried igneous bodies. Minor skarns and replacement massive sulphide bodies are hosted in marginal Jurassic limestones. The main deposit forms a long narrow linear zone (4 km by 300 m) exploited in an open pit. Other porphyry prospects in the belt include the Crni Vrh region where several large low grade porphyries have been located by drilling.