Geologic environment, mineralogy, and fluid inclusions of the Bois Noirs-Limouzat uranium vein, Forez, France

The genesis of the Bois Noirs-Limouzat uranium deposit involves a very complex history. The Bois Noirs granite resulted from the anatexis of uranium-rich sediments near granulite facies conditions. The temperature is estimated to have been at least 800;degree;C accompanied by a low H;sub 2;O partial pressure (possibly resulting from the presence of carbon dioxide). This magma was syntectonically emplaced along the east-west structures in a nonmetamorphic environment. When all the magma had crystallized, the fluid phase migrated outward to precipitate uraninite, with an associated quartz-muscovite alteration. This critical step produced an easily leachable uranium source in the granite in the form of uraninite. 96 refs