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酸性火山岩是构成白银厂火山穹隆的主体核心 ,也是黑矿型白银厂式矿床的容矿岩石。本文从酸性火山岩的岩相学特征、主要元素、微量元素、稀土元素地球化学研究入手 ,对酸性火山岩的分类及系列划分、微量元素和稀土元素地球化学及其形成的构造环境进行了深入的探讨。认为该区酸性火山岩主要由流纹岩和英安岩组成 ,属低钾系列和钙碱性系列。地球化学特征表明 ,它的形成是由板块俯冲至深处脱水 ,致使先存下地壳含水辉长质岩石部分熔融而成。其成岩环境为火山弧环境。
Acidic volcanic rocks constitute the main core of the Baiyinchang volcano dome and are also the ore-bearing rocks of the black-ore type silver deposit. This paper starts with the petrography, major elements, trace elements and REE geochemistry of acidic volcanic rocks. The classification and series division of acidic volcanic rocks, the geochemistry of trace elements and rare earth elements and the tectonic setting of them are discussed in depth. . It is considered that the acidic volcanic rocks in this area are mainly composed of rhyolite and dacite, belonging to the series of low-potassium and calcium-alkaline. Geochemical characteristics indicate that its formation is caused by subduction of the plate to the depth of dehydration, resulting in partial melting of pre-existing water-bearing gabbros in the crust. Its diagenetic environment is a volcanic arc environment.