Distribution and Geochemistry of Uranium in the Orcadian Rocks from Northeast Scotland: A Fission Track Study

Fission track study on thin sections of whole rocks and separated minerals from different sedimentary facies of the lacustrine Orcadian basin, northeast Scotland has shown variations in uranium distribution in different facies which can be correlated with the prevailing redox conditions during deposition. Uranium in sandstones is associated exclusively with detrital grains of apatite and zircon but not with any authigenic phase indicating oxidizing environment. In contrast, in shales and dolostones very little uranium is associated with detrital zircon and apatite, and mostly occurs either adsorbed on grain surfaces or incorporated in the crystal structure of the authigenic minerals and organic matter pointing to reducing environment.