Manganese deposits in Turkey are divided into four main groups on the basis of their age, host rocks and processes of formation. The first is hydrothermal-hydrogenetic and rarely diagenetic-type manganese deposits which are chiefly associated with radiolarian chert series. These deposits occur as lenses and small ore beds within ophiolitic melanges zones of Paleo-Tethyan, Karakaya and Neo-Tethyan (North Anatolian and South Anatolian) suture belts. The second is black shale-hosted manganese deposits that is found in black shale, calcareous shale and calciturbiditic limestone horizons of the passive margin sediments of Late Cretaceous age in the western Taurides. These deposits generally are metamorphosed to greenschist facies and include Mn carbonate-silicate and oxide minerals. The third is volcanic are-hosted ores along the Black Sea margin which occur in different types of metasomatic, hydrothermal and stratabound settings. Rock associations include Upper Cretaceous dacitic tuff, reddish limestone, marl and hemipelagic claystone. The fourth is Oligocene-hosted ores in the Thrace Basin. These deposits are similar to those of the Paratethyan Oligocene belt which occur on the eastern and northern margin of Black Sea and includes the Chiatura (Georgia), Nikopol (Ukraine) and Varna (Bulgaria), respectively. The Oligocene Mn deposits of the Thrace Basin were formed by diagenetic replacement processes during a marine regression. (C) 1997 Elsevier Science B.V.