Variscan belt tectonothermal evolution and the genesis of the Limousin vein type uranium deposits

Variscan belt vein type U-mineralisation as illustrated by the Northern Limousin Province results from a succession of four major thermal and tectonic events during the Neovariscan period: (i) emplacement of peraluminous leucogranite and formation of magmatic U preconcentrations at 325±5 Ma during synconvergence extension; (ii) slow exhumation rate episode from 320 to 305 Ma with emplacement of small U-enriched pluton in a lineament, (iii) fast exhumation rate episode at 305±1 Ma with episyenitic trap formation; (iv) 305-270 Ma period, with renewed extension towards the end of this period, which led to the formation of Permian basins, infiltration of oxidised meteoric fluids and reducing formation waters which mixing was responsible for intragranitic U-deposit genesis. (author)