Sandstone-type Uranium Deposit
Chemical Process (Solution-Rock interaction) - Ground Surface (Meteoric)
Required Geological Setting
Neogene and Quaternary sediments
Occurrence
Uranium deposits in fluvial sedimentary rocks such as sandstones and conglomerates, especially arkose sandstones. Formation of this type deposits is recognized from Devonian period (400 Ma) in Paleozoic Era to the present time. Most of deposits exhibit bedded form, and associated with organic matters and pyrite. The formation process is considered as follows: Dissolved uranium in the groundwater is reduced to be deposited at the reductive condition supplied by organic matters originated from plant fossils in the host rocks. Japanese uranium deposits are observed in high permeable sediments at the channel basements of old rivers, and associated with plant fossils such as lignites.
Mineral Assemblages
Ningyoite, Uraninite (Pitchbelnde), Coffinite, Pyrite
Localities
- Ningyotoge mine
- Togo mine
- Tono mine