The role of metalliferous and mineralised uranium granites in the formation of uranium provinces

Many uranium provinces contain or are spatially associated with late tectonic granites which carry large quantities of radioelements to a high level in the crust. 'Metalliferous' granites, in which uranium remains in primary silicate minerals, provide large volume low level sources for roll-front or other sedimentary uranium deposits but occurrences of hydrothermal uranium mineralisation are related to the crustal setting of the granites - particularly host rock lithology, metamorphic grade, and fracture systems. Occurrences of uranium mineralisation are reviewed in relation to the geochemistry and crustal setting of granites with particular reference to Caledonian and Hercynian intrusions in the UK. Exploration criteria suitable for automated screening of geological and geochemical maps are indicated including some simple element ratios which can be used to distinguish 'metalliferous' from 'mineralised' granites in which uranium occurs in ore minerals. It is suggested that characterisation of such granites can help in the design of exploration programmes by indicating the likely models for uranium concentration in basement and overlying sedimentary cover