西藏墨竹工卡县邦铺钼(铜)矿床辉钼矿稀土—微量元素特征及对成矿流体性质的指示

摘要

文章以西藏墨竹工卡县邦铺钼(铜)矿床辉钼矿为研究对象,采用高精度电感耦合等离子质谱( ICPMS)对辉钼矿进行了稀土和微量元素测试.测试结果显示辉钼矿具有轻稀土富集的右倾配分模式,轻重稀土内部分馏明显.辉钼矿稀土元素不同程度地出现铕负异常和铈负异常现象,分析得出其铕负异常可能是继承了成矿流体自身铕亏损的特征,而铈负异常反映出成矿流体该阶段具有较强氧化性的特征.辉钼矿微量元素中Cu、Pb、Zn、W等元素含量较高,表明成矿流体自身富集成矿元素的特征；而高场强元素亏损、Hf/Sm、Nb/La、Th/La比值小于1的特征,反映出成矿流体为富Cl型流体；辉钼矿的Y/Ho、Zr/Hf、Nb/Ta比值变化范围较小,表明主成矿期成矿流体来源相对稳定,基本无外来流体混入.%Rare earth element and trace element of molybdenite in the Bangpu Mo ( Cu ) deposit, Maizhokunggar, Xizang (Tibet) , were analyzed by high sensitive inductively Coupled Plasma Mass Spectrometry in this paper. The testing results indicated that rare earth element in molybdenite had the distribution pattern of LREE enrichment and the fractionation in both light rare earth element and heavy rare earth element were obvious, Eu and Ce negative anomalies exist in different degree in the molybdenite. The Eu negative anomaly in molybdenite maybe inherit the characteristics of Eu negative anomaly of the ore-forming fluid itself and the Ce negative anomaly reflected that the ore-forming fluid were of stronger oxidization property. The high contents of Cu, Pb, Zn and W in the molybdenite revealed that the ore-forming fluid was riched in ore-forming elements itself. Depletion of high strong field element and the Hf/Sm, Nb/La, Th/La ratios less than 1 suggested that the ore-formign fluid was a Cl-riched type fluid. Ratios of Y/Ho and Zr/Hf varied in a narrow range indicated that source of the ore-forming fluid in the main metallogenic stage was single and stable and had no other fluid injecting.