四川冕宁木洛稀土矿床地质特征

Geological Features of Muluo REE Deposit in Mianning,Sichuan Province

木洛稀土矿床是攀西地区新发现的中型稀土矿床,位于攀西裂谷带北段西界,冕西稀土成矿带西部亚带。该矿床的控矿构造是南北向棉纱湾断裂,控矿岩体为喜马拉雅期的英碱正长岩,地质背景和牦牛坪稀土矿极为相似。矿脉受断层、裂隙、接触面控制,有两种大类型和5种基本类型。矿石由于矿物组合及赋存形式不同而具有6种类型。氟碳铈矿是最主要的稀土矿物,以其富铈的强选择配分型为特征。围岩蚀变较弱,和稀土矿化有关的有霓石(霓辉石)化、方解石化、萤石化、重晶石化和钠长石化。通过和牦牛坪矿床地质特征类比研究表明木洛矿床形成与地幔流体部分熔融、分异结晶形成的富集挥发分和轻稀土元素热液的充填-交代作用有关。

The Muluo REE deposit of Mianning is a middle-scale new deposit found in Panxi region. It is located in north part and west flank of the Panxi rift and belongs to the western sub-belt of REE mineralization in the west of Mianning region. The Mianshawan fracture directly controls the location of Muluo REE deposit. The alkaline syenite which intruded in Himalayan era directly connects with the REE deposit. These features show that the Muluo REE deposit is very similar to the Maoniuping REE deposit. The ore veins controlled by fractures, cracks and touching faces of different rocks, are divided into two classes and five sub-classes. Six types of ores were classified on the basis of the mineral composition, textures and structures. Bastinaesite is the predominant commercial rare earth mineral, which is characterized by strong Ce-selection pattern. The waU-rock alterations are weak and connect with REE mineralization, which including aegirinization, calcitization, fluosparzation, baritization and albitization. Compared with geological features of the Maoniuping REE deposit, the Muluo REE deposit derived from fill-function and metasomatism of fluids, being highly enriched in volatiles and REE, which came from earth＇s mantle and underwent the partial-melting and fractional crystaUization.