THE ALBERA ZONED PEGMATITE FIELD, EASTERN PYRENEES, FRANCE

Four types of pegmatites comprise the zoned pegmatite field in the eas tern sector of the Albera Massif. Type I is represented by barren pegm atites with graphic textures; type II comprises transitional varieties with Li-Fe-Mn phosphates, Be (chrysoberyl) and scarce Nb-Ta and U oxi de minerals; type III consists of pegmatites with significant zones of replacement containing Li-Fe-Mn phosphates, beryl and more abundant N b-Ta oxide minerals; and type IV, muscovite-quartz-albite pegmatites a re highly mineralized with Be, Nb-Ta and HREE. REE mineralization is s trongly related to abundance of graphite in the late pegmatite units a nd in the host-rock. The individual pegmatite types are distributed wi thin four subparallel zones concentric around anatectic muscovite-biot ite leucogranites, with type I within the granites or close to the con tact, and type IV pegmatites in the outermost areas. The zoning from t ype I to type IV could relate to fractionation processes which generat ed the pegmatites and is characterized by an enrichment of Mn, Ta, Na, Li, P, Be and REE. According to the pegmatite distribution and their fractionation trends, we propose an origin by differentiation of a gra nitic melt.