桂东南燕山期花岗岩地球化学特征及其对稀土成矿的指示

Geochemical characteristics and rare earth metallogenic indication of Yanshanian granite in Southeast Guangxi

为探讨桂东南地区离子吸附型稀土矿的成矿条件,本文对桂东南岑溪一带分布的花岗岩进行了详细的年代学、地球化学及稀土矿物学研究。锆石U-Pb年代学研究显示,花岗岩的形成时代为155±0.85 Ma,为燕山期岩浆活动的产物;花岗岩具有高硅富碱的特征,表现出与A型花岗岩相似的地球化学属性,样品的Sr、P、Ti、Eu负异常明显,显示出高分异演化特征。岩石富含独居石、氟碳钙铈矿、锆石、磷灰石等稀土矿物,其中,独居石和氟碳钙铈矿的稀土氧化物总量分别达58.07%~67.66%和64.25%~64.59%;结合该区域高温高湿、降雨充沛、风化作用强烈等外生条件,推测该地区具有离子吸附型稀土矿的成矿潜力。

In order to explore the metallogenic conditions of ion‑adsorbed rare earth deposits in southeastern Guangxi,this paper presents detailed chronology,geochemistry and rare earth mineralogy studies on granites distributed in Cenxi area,southeastern Guangxi.Zircon U‑Pb geochronology study shows that the formation age of granite is 155±0.85 Ma,suggesting the granite is the product of Yanshanian magmatic activity.The granite is characterized by high silicon and alkali,showing the similar geochemical properties with A‑type granites.The samples have obvious negative anomalies of Sr,P,Ti and Eu,showing high differentiation evolution characteristics.The rock is rich in monazite,bastnasite,zircon,apatite and other rare earth minerals.Thereinto,the total rare earth oxides of monazite and bastnasite take up 58.07%~67.66%and 64.25%~64.59%of the granite,respectively.Combined with the exogenous conditions of high temperature and humidity,abundant rainfall and strong weathering in the region,it is suggested that the region has the metallogenic potential for ion adsorption rare earth minerallization.