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白银厂矿田玄武岩主要由玄武岩和碱性玄武岩组成 ,其中玄武岩属于钙碱性系列和拉斑系列 ,碱性玄武岩属于钾质碱性玄武岩系列和钠质碱性玄武岩系列。相对于N -MORB ,本区钙碱性系列和拉斑系列玄武岩明显富集Ba、Rb、Th、U ,而亏损Ti;碱性系列玄武岩高度富集K、Ba、Rb、Th、U ,而Ti、Zr、Ce相对亏损 ,表明该区玄武岩的形成与板块俯冲作用有关。钙碱性玄武岩系列和拉斑玄武岩系列玄武岩具有低的REE含量和亏损的LREE配分型式 ,表明它是由LREE亏损和HREE略有富集的地幔部分熔融形成 ;碱性系列玄武岩的REE含量和 (La/Yb) N 比值高 ,LREE和HREE的分馏程度较高 ,表明其形成于演化的岩浆 ,可能来自于富集LREE的地幔源区或地幔橄榄岩较低程度的熔融。痕量元素地球化学特征表明 ,本区玄武岩应是与板块俯冲作用有关的地幔部分熔融形成 ,成岩环境为火山弧环境 ,是岛弧向成熟岛弧转化过程中的产物。
The basalt in the Baiyinchang ore field is mainly composed of basalt and alkaline basalt. Basalt belongs to the series of calcium and alkaline and the series of spots, and alkaline basalt belongs to the series of potassic alkaline basalt and sodium basic basalt. Relative to N-MORB, the basalts of calc-alkaline series and basalt series are significantly enriched in Ba, Rb, Th and U, and depleted in Ti. Basal series of basalts are highly enriched in K, Ba, Rb, Th and U The relative loss of Ti, Zr and Ce indicates that the formation of basalts in this area is related to plate subduction. The basalts of calcareous basalts and tholeiite basalts have a low REE content and a depleted LREE composition pattern, indicating that they are partially melted by LREE depletion and slightly enriched mantle of the HREE. The REE content of alkaline basalts and ( La / Yb) N ratios are high and LREE and HREE are highly fractionated, indicating that they formed in the evolved magma probably from a lower degree of melting of the mantle-derived regions rich in LREEs or mantle peridotites. The geochemical characteristics of trace elements indicate that basalts in this area should be partially melted by the mantle associated with plate subduction. The diagenetic environment is a volcanic arc environment and is the product of the island arc transition to mature island arc.