金平龙脖河铜矿区变钠质火山岩系地球化学研究:Ⅰ.主微量元素特征和形成环境探讨

GEOCHEMICAL STUDIES ON SODIUM ENRICHED VOLCANIC ROCKS IN THE AREA OF LONGBOHE COPPER DEPOSIT,YUNNAN PROVINCE, SW CHINA: I. CHARACTERISTICS OF MAJOR AND TRACE ELEMENT AND IMPLICATION FOR GENETIC ENVIRONMENT

云南龙脖河铜矿区浅变质火山岩、辉绿岩与火山碎屑岩均具明显富钠贫钾特征；从各种岩石化学分类图解可得到互相不同的判别结果。轻稀上从略富集到略亏损的分配模式及低的RB、Sr含量表明具从洋中脊至岛弧拉斑玄武岩过渡的特征。各种火山岩TiO2与Nb、Th、Y、重稀土元素之间存在好的正相关关系，稀土模式具平移的特征均表明存在强的钠交代细碧岩化作用。钠交代作用与铁矿化同时发生。上述地球化学特征和大红山群变钠质火山岩系相一致。

The volcanic rocks associated with Cu mineralizahon in Longbohe area Yunnan,are mainly composed of meta-basalts, andesites, volcanic breccias and diabases, which show sodium enriched and potassium depleted features. The petrochemical category of various diagram gave contradict results between alkaline and tholeiitic series. The rare earth elements show patterns from slight depletion to slight edrichment of ligh REE,showing the transitional features of MoRB and IAT, which is consistent with lower Sr and Rb concentration of these rocks. The medium incompatible element such as Nb,Th, Y, HREE and V are also enriched and there are good posihve correlations with Ti, which indicates there existed influence of metasomatism. The geochemical characteristics of the sodium enriched volcanic rocks in Longbohe area are consistent with those of the volcanic rocks of Dehongshan Group.