白银厂矿田酸性火山岩岩石学及微量元素地球化学特征

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。

PETROLOGY AND TRACE ELEMENT GEOCHEMISTRY OF THE ACIDVOLCANIC ROCKS OF BAIYINCHANG ORE FIELD

The studied acid volcanic rocks make up the main core part of the Baiyinchang volcanic dome structure,and is the ore-bearing rocks of Kuroko Baiyinchang-style ore deposit as well.Based on the study on petrography,REE,major and trace element geochemistry of the acid volcanic rocks,discussions on the rocks are put on the following aspects:rock classification,rock series division, trace and REE geochemical characteristics and the tectonic setting for forming the rocks. The rocks are mainly composed of rhyolite and dacite,belonging to low-K and calc-alkaline series.Geochemical characteristics shows that the formation of the rocks typical of volcanic arc is related to the partial melting of the mantle wedge associated with plate subduction.