Chapter 4 - Geosystems model of uranium deposits

Abstract

The formation and origin of uranium deposits is of interest for uranium exploration necessary for the sustainability of nuclear energy production. The proper organization of this knowledge is the most important. Prior models or classifications of uranium deposit types do not emphasize the geological relationships between deposit types illustrated by the uranium geochemical cycle. The proposed Geosystems Model/Classification of uranium deposit types starts at rift shoulders where thermal upwelling promotes anatexis, mafic intrusions, A-type granitic batholiths, uraniferous calderas, and voluminous ash-flow tuffs. Numerous deposit types are in this igneous portion of the uranium geochemical cycle. Intra-cratonic sedimentary basins over geological time have provided multiple depositional opportunities. Several deposit types are outliers. The proposed Geosystems Model accommodates IAEA classes into the tectonic-uranium geochemical cycle–based interrelationships. New perspectives are the initiation of magmatism at rift shoulders, diversity of caldera environments, intra-cratonic basin template applicable over time, and surface uranium deposit types with accessibility to voluminous uraniferous air fall tuffs. The uranium to thorium ratio is a useful property for uniquely identifying different uranium sources, processes, and deposit types.