Genesis of uranium deposits in Neogene sedimentary rocks overlying the Menderes metamorphic massif, Turkey

Uranium deposits in the Köprübaş? area of western Turkey occur in fluviatile sedimentary rocks which are underlain by high-grade metamorphic rocks of the Menderes massif. These deposits occur in Neogene conglomerate beds that contain a matrix of abundant silt and clay and are in beds of sandstone. Uranium is present as a matrix impregnation in tabular lenses within the conglomerate and sandstone beds. Both oxidized and unoxidized deposits occur. Oxidized deposits can be divided into jarosite-waylandite-rich and ilmenite-rich types, both of which occur near exposures of metamorphic basement rocks. Uranium in the ilmenite-rich type is disseminated uniformly throughout the sandy matrix of the conglomerate. Uranium in unoxidized sandstone is disseminated throughout the clayey matrix and is associated with authigenic pyrite and siderite. Ore-grade uranium concentrations in the unoxidized deposits are confined to pyrite-rich zones, whereas only low-grade mineralization occurs in siderite-rich zones. Authigenic pyrite formed during diagenesis. This pyrite subsequently reduced oxygenic uraniferous groundwater and induced precipitation of the uranium. Oxidized jarosite-waylandite-associated uranium deposits apparently formed by oxidation of reduced uranium deposits. Therefore, all the deposits are epigenetic in origin, formed by precipitation of uranium by groundwater solutions that moved through the host rock. The basement metamorphic rocks are believed to have been the major source of uranium. © 1980.