浙东中生代火山岩岩石系列及大地构造环境判别

应用Q—型聚类分析、对应因子分析及某些微量元素图解等方法,判别出本区火山岩属高钾钙碱性系列,它与东太平洋沿岸火山岩及花岗岩相似,而与日本、台湾等岛弧火山岩相差较大,可能属于活动大陆边缘构造环境的产物。

MESOZOIC VOLCANIC ROCK SERIES AND DISCRIMINATION OF TECTONIC ENVIRONMENTS IN EAST ZHEJIANG

East Zhejiang is the area of the Southeastern China where Mesozoic volcanic rocks are well developed. Volcanism may be divided into four eruption cycles.Regional tectonic environment of volcanism in this district has always been the debated problem. In this paper, a comparison of volcanic rocks of east Zhejiang with volcanic and granitoid rocks of the the typical areas in the world in terms of geochemical feature, correspondence factor analysis, Q-type cluster analysis and discrimination diagram of trace elements of the volcanic rocks has been made in order to judge the tectonic environment of formation of volcanic rocks. The volcanic rocks of this area belong to high-K calc-alkalic series, which are predominated by potassium and common type. The main rock-forming elements of volcanic rocks are similar to that in active continental margin of the East Pacific Coast, but greatly differ from volcanic rocks in the Western Pacific Island Arc.Trace elements such as Nb, Y, Yb, Rb etc. show the features of Volcanic Arc granitoids,the correlation charts of SiO2 v.s Nb,Y, Yb are situated in the field of Volcanic Arcs; some trace elements and rare earth elements pattern show the features of the active continental margin granitoids,particularly are very similar to Chile granitoida out of ordinary, the volcanic rocks of this area are characterized by slight higher content of K2O, Rb, Ta, Th, Ba etc. According to above - mentioned comparison and analysis, it is infered that the Mesozoic volcanism took place in the active continental margin.