TH, U, REE MINERALS IN THE GARA ADJEMAMAYE PERALKALINE GRANITE (CENTRAL HOGGAR, ALGERIA)

Tlemcen (Algeria)

The Gara Adjemamaye peralkaline granite outcrops in the Egere-Aleksod terrane (central Hoggar). The main facies is a grey to cream heterogranular rock composed of quartz, mesoperthite, sodi-calcic amphibole, sodic pyroxene, annitic biotite, opaques, Fe-Ti oxides, zircon and abundant (Th, U, REE) bearing minerals. The latter are often finely dispersed in veins crossing the rock, suggesting crystallization due to extensive late-stage remobilization. This work represents a contribution to the crystal-chemistry of these rare minerals and the metasomatic mobility of incompatible elements such as Ti, Zr and REE in igneous environments.