内蒙古大梁道班地区大石寨组火山岩的地质地球化学特征及其构造环境探讨

DISCUSSION ON THE GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS AND TECTONIC ENVIRONMENT OF THE VOLCANO ROCKS IN INNER MONGOLIA DASHIZHAI GROUP GIRDER GANG AREA

内蒙古锡林浩特大梁道班地区大石寨组火山岩为一套富铝富硅的中酸性钙碱性系列火山岩,岩性组合为安山岩、英安岩、流纹岩等;稀土总量较高且轻重稀土分异明显;Nb、Ta、Ti、P等高场强元素(HFSE)相对亏损,板内元素相对富集。将上述岩石地球化学特征与构造环境判别图解相结合分析,初步确定该地区大石寨组火山岩形成于活动大陆边缘向弧后盆地演化的构造环境中,因此进一步推断大梁道班地区内在早中二叠世处于板块汇聚阶段,西伯利亚板块与华北板块在贺根山一带缝合,这次板块碰撞也标志着本区内古亚洲洋的闭合。

The Dashizhai group volcano rocks in Inner Mongolia Xilinhaote Daliangdaoban area is a set of aluminum and silicon rich acidity calc alkaline series volcano rock,lithologie andesite,dacite,rhyolite;The total content of rare earth elements is relatively high and the differentiation between LREE and HREE is obvious;The high field-strength elements（HFSE） such as Nb, Ta. Ti. P relatively loss and the plate elements enrich.Analyzing the petrological and geochemical characteristics,combined with the tectonic discrimination diagrams,it was preliminarily concluded that the Dashizhai group volcano rocks formed in the tectonic evolution environment which is from the active continental margin to the back-arc basin,thus further inferring that in the Daliangdaoban area,in the early to middle Permian plate convergence stage,the Siberia plate and the North China plate in Hegenshan area sutured.The plate collision also marked the closure of the paleo Asian ocean.