Major Oligocene lead-zinc mineralization in the Central Rhodopes occurs in four ore fields: Madan, Laki, Davidkovo (South Bulgaria) and Thermes (Greece).
Madan ore field is situated in southwest part of the Central Rhodope Dome. Thirty-nine lead–zinc deposits were mined within the Madan field. Madan ore field occurs as an area of the most considerable deposition of Pb-Zn ores in the Rhodope massif and represents one of the most significant manifestations of vein type Pb-Zn mineralization in the world. The larger deposits are related to six fault zones with lengths up to 15 km and more. The ore bodies are of three types – veins, carbonate replacement bodies and stockworks. Veins are the most widespread with typical lengths between 500 m and to 2 to 2.5 km and vein widths up to 10 m (more commonly 1–2 m). The main minerals of all deposits are quartz, galena and sphalerite with additional johannsenite becoming important in the peripheral parts of the replacement ore bodies. In decreasing order of abundance, additional ore minerals are pyrite, chalcopyrite and arsenopyrite, and as gangue minerals calcite, manganocalcite, rhodochrosite, dolomite and rhodonite, the last occurring in the metasomatic ore bodies only. One of the most important faults for ore-localization is the Karaaliev dol-Petrovitsa fault on which the Osikovo, Mogilata, Karaaliev dol, Petrovitsa, Yuzhna Petrovitsa and Erma reka deposits (which samples we mainly present here) are located.