稀土元素地球化学在成矿系统厘定及矿床成因分析中的应用——以印度尼西亚塔里亚布岛铁多金属矿田为例

以印度尼西亚塔里亚布岛铁多金属矿田为典型实例,探讨了稀土元素地球化学在厘定成矿系统中的作用及相同成矿系统的稀土元素地球化学叠加与演化规律。研究表明:除辉绿岩外,花岗岩、大理岩、变质砂岩及矽卡岩都是铁多金属成矿系统的组成部分,矿浆型和矽卡岩型磁铁矿矿石及铜锌硫化物矿石均属相同系统的成矿作用产物。矿浆型磁铁矿矿石为该系统的一个相对独立的子系统,即印支期花岗岩结晶分异成矿系统;矽卡岩型磁铁矿矿石和热液充填交代型铜锌硫化物矿石同属一个子系统,即接触交代成矿系统;两个子系统是一个从岩浆阶段至热液阶段的完整成矿演化系列。从矿浆型矿石至接触交代型再到热液充填交代型负铕异常逐渐减弱,分馏程度逐渐增强,由重稀土富集型转变为轻稀土富集型。因此,稀土元素地球化学研究是厘定复杂成矿系统、分析矿床成因的有效手段。

REE geochemistry application in discrimination of metallogenic system and ore genesis: An example from iron polymetallic orefield in Taliabu Island, Indonesia

Taking the iron polymetallic orefield in Taliabu Island,Indonesia as an example,the application of REE geochemistry in discrimination of metallogenic system and the regularities of REE superposition and evolution in the same mineralization system were investigated.The results show that in Taliabu Island,granite,marble,metamorphic sandstone and skarn are the composition parts of the iron polymetallic metallogenic system except for diabase.Ore magma and skarn magnetite ores as well as Cu-Zn sulfide ores are originated from the same metallogenic system.In this system,ore magma type is a relatively independent subsystem,that is,a crystal fractionation system of Indosinian granites;skarn type and hydrothermal filling type belong to another subsystem,that is,a contact metasomatic metallogenic system.Two subsystems belong to a complete mineralization system from magma stage to hydrothermal stage.From ore magma type to skarn type to hydrothermal filling type,negative Eu anomaly decreases,REE fractionation degree increases,and HREE enrichment converts to LREE enrichment gradually.Therefore,REE geochemistry is an effective method in discriminating mineralization system and ore genesis.