电感耦合等离子体质谱法对白钨矿中稀土元素的准确测定——以云南麻栗坡南秧田白钨矿床的成因探讨为例
Accurate Determination of Rare Earth Elements in Scheelite Using High Resolution-Inductively Coupled Plasma-Mass Spectrometry——An Instance of Nanyangtian Scheelite Mining, Malipo, Yunnan
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摘要: 通过建立的高分辨电感耦合等离子体质谱测定稀土元素(REEs)的分析方法,准确测定出麻栗坡南秧田白钨矿床两类不同矿体的围岩和矿石中稀土元素的含量,方法的灵敏度高,检出限低,精密度和准确度均非常满意。通过对稀土元素地球化学特征的研究,表明存在两种不同成因的白钨矿,一为与围岩同时沉积形成的白钨矿,在变质作用条件下形成了矽卡岩型白钨矿; 二为后期热液携带来的具有较高稀土含量的石英脉型白钨矿。前者具有轻稀土元素富集、重稀土亏损、中等程度的Eu、Ce负异常等特征,与沉积环境关系密切,推测是海底火山喷发(喷流)沉积变质作用的产物; 后者具有较低的稀土总量∑REEs以及显著的Eu正异常特征,表现出较高的稀土分馏特性,为后期热液作用形成,并对先期矿体有叠加改造作用,使矿化更加富集。
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关键词:
- 南秧田白钨矿床 /
- 稀土元素 /
- 高分辨电感耦合等离子体质谱法 /
- 地球化学 /
- 示踪
Abstract: The rare earth elements (REEs) in two different types of ores and wall rocks in Nanyangtian scheelite mining, Malipo, Yunnan, were accurately determined by High Resolution-Inductively Coupled Plasma-Mass Spectrometry (HR-ICP-MS). The method of REEs determination is reliable and of high sensitivity, with a low detection limit and satisfactory precision and accuracy. The geochemical characteristics of REEs show the existence of two different types of scheelite ore. The first one is skarn scheelite which is derived from sedimentary scheelite deposits by late metamorphism. The second is quartz-vein scheelite with high REEs content by late stage hydrothermal fluid. The former has rich LREEs and depleted HREEs, a medium degree of negative Eu and Ce anomaly, which are closely related to the sedimentary environment, supposedly the diagenism product around submarine volcano eruption. The latter has low amounts of ∑REEs and an outstanding positive Eu anomaly, reflecting the strong fractionation of REEs, probably formed by later stage hydrothermal activities. The superimposition-reformation for early ore bodies by late stage hydrothermal fluid improved the mineralization enrichment.-
Key words:
- Nanyangtian /
- scheelite /
- mining /
- rare /
- earth
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