Geochemical Characteristics of Carboniferous-Permian Volcanic Rocks in Zhongguai Area in Northwestern Margin of Junggar Basin

The analyses of the whole-rock elements of 25 samples from Carboniferous-Permian volcanic rocks in Zhongguai area in northwestern margin of Junggar basin reveal that the volcanic rocks are mainly composed of intermediate-acid andesite,dacite,rhyolite,volcanic breccia and tuff,of which SiO2 content averages 66.840%,and they are dominated by calcic series and calc-alkalic series(calcic series accounts for 64% and calc-alkalic series for 36%).According to the geochemical characteristics of the volcanic rocks in this area,the volcanic eruption should occur in the continental inner side of island arc system and undergo melting process of continental crust.