新疆包尔图铜矿稀土元素地球化学特征及其地质意义

REE geochemical Character of the Baoertu copper deposit in Xinjiang and its geological significance

包尔图铜矿床位于南天山库米什洋盆俯冲变质带的边缘,矿体受断裂构造控制。矿区围岩为一套中深变质岩,其稀土元素组成具有如下特征:∑REE较高,LREE/HREE=2.46～16.86,轻重稀土元素明显分异,且轻稀土相对富集,负铕异常,配分模式曲线向右倾斜。矿石的∑REE相对较低,LREE/HREE=0.06～0.97,轻重稀土元素明显分异,重稀土相对富集,配分曲线向左倾斜,与混合岩脉体的稀土元素配分模式相近。稀土元素组成特征指示矿床的成矿过程可能与混合岩化作用有关。结合矿床地质特征,认为包尔图铜矿床为变质热液型铜矿床。

Located on the edge of the metamorphic belt formed by paleo-Kumishi ocean subduction,the Baoertu copper deposit is controlled by fault structures.The wall rocks are composed of a set of medium-deep grade metamorphic rocks,and REE geochemistry shows that their ΣREE content is high,with LREE/HREE being 2.46～16.86,and there exists obvious differentiation between LREE and HREE,with the enrichment of LREE relative to HREE and the existence of negative Eu anomaly.The REE patterns assume right inclination.By comparison,the ores have relatively low ΣREE content,with LREE/HREE being 0.06～0.97,and show significant differentiation between LREE and HREE characterized by relative enrichment of HREE.The REE patterns show left inclination,similar to things of the leucosome of migmatite.These REE characteristics suggest that the ore-forming process of the Baoertu copper deposit was related to hybirdization.Combined with the characteristics of the ore field geology,this paper holds that the Baoertu copper deposit is genetically of the metamorphic hydrothermal type.