GELOGICAL FEATURES OF MAONIUPING REE DEPOSIT, SICHUAN,CHINA

Abstract

The Maoniuping REE deposit of Mianning, Si chuan, China, is one of the largest deposits in the world. It is located in the west fl ank of the Panxi rift, but the REE mineralization was developed in the postrift stage based on the isotopic ages and the geological environment. Fenitization is well developed around the carbonatite complex which is composed of various size s of carbonatite, alkali basic pegmatite, lamprophyre, granite porphyry, and dia base dikes. The fenite is characterized by a zonation pattern in the sequence of shattered zone, aegirine and aegirine-augite zone, and arfvedsonite zone from o utside to the center. The deposit is a vein system and three types of REE ore, alkali basic pegmatite, calcite carbonatite, and networked stringers, have been classified on the basis of the mineralized veins. Bastnaesite is the predominant commercial rare earth mineral, which is characterized by coarse to megacrystals and by strong Ce-sel ection pattern. The geological features suggested that the deposit could be deri ved from metasomatism of fluids which are highly enriched in volatiles and REEs.