Gold deposits in Greece: Hypogene ore mineralogy as a guide for exploration

Abstract

A common feature of precious metal mineralization in Greece is the close relationship between gold and silver with other trace minerals incorporating bismuth, tellurium and selenium in their structure. These minerals can be considered as pathfinders for gold as they may guide exploration to discover distinct types of gold-bearing ores. Primary gold mineralization in Greece can be subdivided in three groups regarding the mineral associations with gold: (A1) mineralization where native gold and Au-Ag tellurides accompany either Bi-sulfosalts, native Bi and reduced-type Bi-sulfotellurides (joseite-A, joseite-B, pilsenite) at Koronouda, Laodikino/Kilkis area, Stanos, Olympias-Stratoni and Fissoka at Chalkidiki area and Angistron Mt/W. Rhodope), or (A2) accompany Bi-sulfosalts with oxidized-type Bi-sulfotellurides (e.g. tetradymite and tellurobismuthite) typical for Aberdeen, Palea Kavala, Thasos island, as well as for the calc-alkaline and alkaline-hosted porphyry and epithermal deposits/prospects in western Thrace, Limnos island and Skouries; (B) deposits which lack tellurides but include Bi-sulfosalts and native gold (e.g. the carbonate replacement deposit of Lavrion, the porphyry-Cu-Mo-Au deposits of Maronia and Stypsi, Lesvos Island, and the intrusion-related Kimmeria Cu-Mo-Au deposit); and (C) deposits/prospects where native gold and Au-Ag-tellurides and other base metal tellurides are abundant and Bi-tellurides and Bi-sulfosalts are missing (the metamorphic rock-hosted quartz veins at Panormos/Tinos and Kallianou/Evia Islands, and the epithermal shallow submarine mineralization at Milos). Bismuth and tellurium are considered to be derived from magma and recognition of bismuth sulfosalts and bismuth tellurides, as well as of various types of base (and precious) metal tellurides in the mineralization, is a strong evidence of magmatic-hydrothermal contribution and of adjacent concealed intrusives (e.g. Perama Hill and Pefka deposits are cases where no granitoids are exposed). The absence of bismuth minerals and the presence of precious and base metal tellurides (as is the case for Milos, Tinos and Evia islands) may still suggest magmatic contributions but in more distal setting from a buried granitoids at depth. Selenium (and/or bismuth) bearing galena and Se-bearing bismuth chalcogenides present at Kimmeria intrusion-hosted veins, at Lavrion, as well as in several porphyry-epithermal deposits in northern Greece (e.g. Kassiteres-Sapes, Pagoni Rachi, Perama Hill, Pefka and Skouries) are indicative of high-temperature, initial stages of ore deposition from magmatic-hydrothermal fluids, and proximity to porphyry mineralized centers. When recognized in a mineralization as an accessory mineral, Se-bearing galena could guide exploration towards unexposed granitoids. Bornite and molybdenite are present in the potassic and sericitic alteration zones of Skouries and Pagoni Rachi porphyry deposits, where they are intimately associated with native gold and gold-silver tellurides. However bornite may also occur in intermediate-sulfidation epithermal veins at Kassiteres-Sapes and Pagoni Rachi areas and molybdenite at Stanos and Syros Island without any obvious relationship to a granitoid. Both minerals can be applied for discovery of high temperature mineralized zones in the system.