四川冕宁牦牛坪稀土矿床地质特征

四川牦牛平矿床是世界上最大的稀土矿床之一，该矿床位于攀西裂谷西缘，同位素年龄表明稀土化发育于裂谷期后阶段。矿区内碳酸岩、碱性基性伟晶岩、花岗斑岩、煌斑岩以及辉绿岩岩墙（脉）构成了与矿化有关的碳酸岩杂岩。围绕碳酸岩杂岩广泛发育着霓长岩化，蚀变作用形成的霓长岩具有显显的分带特征，由内向外可分为：钠铁闪石黑云母带、霓石霓辉石带、碎裂带。该矿床具有三种矿石类型：碱性基性伟晶岩型、岩酸岩型和细网脉裂。氟碳铈

GELOGICAL FEATURES OF MAONIUPING REE DEPOSIT, SICHUAN, CHINA

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.