内蒙古北山地区白云山一带早泥盆世火山岩地球化学特征及地质意义OACHSSCD

The Hongliuhe-Niujuanzi-Xichangjing serpentinite-greenstone complex is developed in the Baiyun Mountain area of the northern mountainous region of Inner Mongolia,where a set of middle and basic volcanic rocks are developed on its southern side,with rock types including basalt,basaltic andesite,and andesite.The LA-ICP-MS zircon U-Pb age of the basalt is 403.6±2.0 Ma,corresponding to the early Devonian.The main components SiO2 is 49.62％～62.74％;K2O is 0.2％～3.59％;NaO2+K2O is 2.09％～7.45％,and the whole has the characteristics of-calcium alkaline rocks.The total amount of rare earth elements ∑REE is between 57.03×10-6 and 184.06× 10-6,and the obvious fractionation of light and heavy rare earth elements(La/Yb)N is between 3.94～12.61,with a relatively weak negative Eu anomaly(δEu=0.71～1.05).Rb,Th,U,La,Ce,Zr,Hf and other rare earth elements are enriched,and high-field strength elements Ba,Nb,Ta,P,Ti areicient.The average value of Rb/Sr is 0.23,the average value of Nb/Ta is 16.19,the average of Zr/Hf is 37.09;δEu average is 0.88,and it has the characteristics of mixed source of crust andle.Discrimination of volcanic rock construction environment indicates that the volcanic rock suite formed in an island arc environment.Comprehensive geochronological and rock chemical characteristics indicate that study area was in a collision mountain building environment in the Early Devonian.