W-Nb-Ta oxides as markers of the magmatic to hydrothermal transition condition in rare-metal granites

In several occurrences of RMG from north Africa (Hoggar & Morocco) and from the French Massif Central, wolframo-ixiolites appear to have crystallised at the magmatic-hydrothermal transition environment. Their composition yield evidence for the selective extraction of W by the Li-F–rich magmatic fluids unmixed from the Li-F-rich melts.