摘要
采用LA-ICP-MS技术对内蒙古道伦达坝铜多金属矿区花岗岩中的锆石进行了U-Pb同位素测定,获得^(206)Pb/^(238)U年龄加权平均值为289.6±0.7Ma,表明岩体侵位于海西晚期。地球化学特征显示,该花岗岩具有强过铝质的特征,并与锡林浩特岩群片麻岩具有亲缘性,推测该期岩浆活动代表了碰撞高峰期后的岩石圈伸展事件。在这个过程中,岩石圈发生拆沉及随后的软流圈上涌或玄武岩浆的底侵,使下地壳的杂砂岩及黑云斜长片麻岩的温度迅速升高(大于875℃)而发生部分熔融形成强过铝质岩浆,同时该花岗岩又兼具火山弧的地球化学特征,推测可能与岩浆活动的滞后性有关,即俯冲板片的成分参与了岩浆的形成。结合区域内其他海西期岩体及海相地层的年代学和地球化学特征认为,该地区洋壳开始俯冲的时间应该在早石炭世末期,碰撞发生在早二叠世。
The granite in the Daolundaba Cu polymetallic ore district was studied with ICP-MS zircon U-Pb isotope dating and geochemical method. A late Hercynian emplacement age of 289.6±0.7Ma was obtained, and the geochemical characteristics suggest a strongly peraluminous granite which has the affinity with the Xilinhaote rock group gneiss. The magmatic activity represents the litho-spheric extension after the peak of the collision event. During the process the lithosphere began delamination and was followed by the asthenosphere upwelling or basaltic magma underplating which led to the rapid increase of the temperature of the graywacke and bio-tite plagioclase gneiss in lower crust （〉875℃）, which caused the formation of strongly peraluminous magma through partial melting. At the same time, the granite always had the geochemical features of volcanic arc and the granite had a relationship with the lag of magmatic activity, which means the composition of the subducting plate was involved in the formation of magma. Combined with the chronologic and geochemical features of Hercynian rocks and the marine strata in the nearby area, it is thought that the ocean crust in the area began to subduct during the late stage of Early Carboniferous and experienced collision during the Early Permian.
出处
《地质通报》
CAS
CSCD
北大核心
2016年第7期1207-1216,共10页
Geological Bulletin of China
基金
中国地质调查局项目(编号:12120113057100)
