新疆巴里坤县老爷庙、额仁山一带晚古生代火山岩

LATE PALAEOZOIC VOLCANIC ROCKS IN LAO-YE MIAO (TEMPLE) AND ER-REN SHAN(MOUNTAIN),BALIKUN COUNTY,XINJIANG

老爷庙—额仁山一带发育3套性质不同的火山岩,通过对其岩石组合、岩相、古火山机构特征的详细观察及岩石学、岩石化学、地球化学的研究,晚泥盆世老爷庙组火山岩为玄武岩-安山岩组合,发育盾状和层状火山,属海相环境,为板块消减带岛弧型高铝玄武岩;晚石炭世—早二叠世哈尔加乌组火山岩为陆相火山岩,岩石组合为安山岩-英安岩-流纹岩,以爆发相为主,常形成破火山及锥状火山机构,为陆-陆碰撞造山期火山岩;早二叠世中晚期卡拉岗组火山岩为一套以酸性为主的陆相火山岩,喷溢相发育,常形成穹状古火山机构,岩石组合为英安岩-流纹岩,为造山期弛张期火山岩,3套火山岩为板块不同阶段的火山岩,从老爷庙组火山岩→哈尔加乌组火山岩→卡拉岗组火山岩,岩石向酸性演化,地壳成熟度愈来愈高,由混合壳转化为陆壳.

Three types of volcanic rock are found in Lao-ye-miao and Er-ren-shan areas, based on petrographic composition, petrographical facies, characteristics of ancient volcanic edifices, and by studying petrology, petrochemistry and geochemistry. The first type volcanic rock is the Late Devonian Lao-ye-mian group which is a mixture of basalt and andesite that formed as basaltic domes and stratified volcanoes in marine facies environment. They are island arc type basalt rich in aluminum. The second type of volcanic rocks in the Ha-er-jia-wu group formed in Late Carboniferous Period and Early Permian are continental types that are domininantly eruptive. The composition of the rock is andesite-dacite-rhyolite. Caldera and cone shape of volcanoes were formed during continent collision and orogeny. The third type of volcanic rocks in the Ka-la-gang group formed in Early Permian and is mainly acid type with continental facies, and extrusive facies. The ancient volcanic mechanism is always formed by this type of volcanic rock, and the composition of the rock is dacite-rhyolite, which formed during the late orogeny period. These three types of rocks are plate types and formed in different stages of time. From the Lao-ye-miao group, Ha-er-jia-we group to Ka-la-gang group, the rocks become more acidic; and crust of the earth is more mature, and changes to continental crust from mixed crust.