挪威中部双峰态火山岩系地质,地球化学特征及其成因

挪威中部Ｇｊｅｒｓｖｉｋ地区加里东造山带由一系列地体组成。Ｇｊｅｒｓｖｉｋ地体内的火山岩系具有明显的双峰态特征，主要由深色和浅色拉斑玄武质绿岩以及石英角斑质火山碎屑岩组成。火山活动分为三个阶段，各阶段火山活动特征与裂谷构造演化息息相关。地质和地球化学证据表明，裂谷演化早期形成来源于亏损地幔未分异型拉斑玄武岩，中期形成由玄武岩或辉长岩局部重熔产生的长英质火山岩，晚期则形成来源于更深部的富集地幔分异型拉斑玄武岩。Ｇｊｅｒｓｖｉｋ地体内已发现一系列的与火山活动有关、空间上与长英质火山碎屑岩紧密共生的块状硫化物矿床。

Geology,Geochemistry and Genesis of the Bimodal Volcanic series in Central Norway

The Caledonian orogenic belt in Gjersvik area of Central Norway is composed of a series of terranes,and the volcanic rocks in the Gjersvik terrane consisting mainly of dark and light-colored tholeiitic greenstone and quartz keratophyric pyroclastic rocks exhibit an obvious bimodal pattern.Volcanic activities can be divided into three stages which were closely asso-ciated with the evolution of rift structure.Undifferentiated tholeiite derived from the depleted mantle was formed at the early stage of rift evolution,felsic volcanic rocks from partial melting of basalt or gabbro were produced at the middle stage,and differential tholeiite derived from the deeper enri-ched mantle came into being at the late stage.A series of massive sulfide deposits have been found within the Gjersvik terrane,which were related to volcanic activities and are spatially in close association with felsic pyroclastic rocks.Studies show that the formation of these deposits was related to the submarine hydrothermal system accompanying the volcanic activity.