塔里木-中朝板块北缘的志留纪岛弧公婆泉群火山岩地质地球化学及构造意义

公婆泉群位于北山中部，可分为：北、南两带。南带为弧后盆地玄武岩-安山岩组合，北带为岛弧火山岩组合，西段窑洞努如为火山角砾岩和熔火山角砾岩组合，中段公婆泉一带为玄武岩-安山岩-流纹岩-粗面岩组合，东段东七一山地区为玄武岩-安山岩-流纹岩组合。岩石组合，地球化学综合分析认为，公婆泉群是中-晚志留世哈萨克斯坦板块俯冲与塔里木-中朝板块的产物。岛弧西段窑洞努如位于近大陆或者在水下陆壳。公婆泉位于近海沟陆壳，而东七一山则远离海沟，是在洋壳的基础上发育的。说明塔里木-中朝板块是一个统一的板块，同时在早古生代存在哈萨克斯坦板块向塔里木-中朝板块的俯冲。

Island arc north of the Tarim-SK plate: the geology and geochemistry of Gongpoquan Group

The Gongpoquan Group is located at the east of most of the conjunction between the Kazakstan plate and Tarim SK (sino korea) plate.It is exposed at direction of NWW EW and classified into two belts,Gongpoquan Dongqiyishan (north) and Niujuanzi (south) belt.The north belt is 190 km in length and 220 km in width and can be divided farther into 3 sects from west to east.It is volcano sedimentary formation resulted from Kazakstan plate subducted beneath Tarim SK plate at mid late Silurian.The rock association in north belt,which is an island arc formation,consists of basalt andesite rhyolite quartz trachyte trachyandesite trachybasalt at the middle sect (Gongpoquan),volcanic lava and lava breccia at the western sect (Yaodongnuru) and basalt andesite rhyolite at the eastern sect(Dongqiyishan).The south belt is 100 km long and 27.5 km wide and its rock association which is a formation of back arc basin comprised by basalt and andesite.Their petrochemistry show they are calc alkline,rich in sodium and poor in potassium except the quartz trachyte.The volcanic rocks are rich in big particle lithophile and inertial elements,poor in TEE and tansitional elements.The difference in the geochemistry of rocks in Gongpoquan,Niujuanzi and Dongqiyishan shows that the crust in the west(Yaodongnuru) is thicker than that in the east(Dongqiyishan),and also the Yaodongnuru is developed on the continent (or under water),Gongpoquan in the continent crust near the trench but Dongqiyishan in the ocean crust apart from the trench.This indicates that the Tarim and Sino korea plate are not separate units but parts of the Tarim Sk plate,and suggests that the Kazakstan plate subducted to the Tarim SK plate in the mid late Silurian.