【摘要】 古亚洲洋贺根山洋盆闭合时间一直存在较大分歧,位于内蒙古中北部查干敖包—东乌珠穆沁旗构造岩浆岩带中部的锡林郭勒盟阿巴嘎旗格勒敖包正长花岗岩体和二长花岗岩体对揭示贺根山洋闭合时限具有重要启示,以格勒敖包岩体为研究对象,开展了锆石U-Pb年龄、岩石地球化学和Hf同位素研究,探讨了其形成时代、岩石成因和构造环境。研究表明,格勒敖包正长花岗岩、二长花岗岩分别于321.3±2.8Ma、306.7±2.4Ma侵位,岩石总体富SiO₂,贫CaO、MgO、P₂O₅、TiO₂,K₂O+Na₂O、Al₂O₃、Fe₂O₃^T含量中等,属于高钾钙碱性系列岩石。富集轻稀土和Rb、Th、U、Zr、Hf等微量元素,亏损重稀土和Ba、Sr、Nb等微量元素,具负Eu异常。两类岩石的锆石ε_Hf（t）值变化于7.6～13.1,对应的二阶段模式年龄为511～928Ma。综合分析认为,格勒敖包正长花岗岩、二长花岗岩侵位于晚石炭世,属分异的Ⅰ型花岗岩,其岩浆源于新生地壳的部分熔融,岩石形成于俯冲带岛弧环境,为贺根山洋俯冲作用的产物。格勒敖包晚石炭世弧岩浆岩的识别与确定,表明古亚洲洋贺根山洋盆在晚石炭世并未关闭,而是处于大洋北向俯冲消减过程中。更多还原

【Abstract】 There has been a great deal of disagreement about the closure time of the Hegenshan Paleo-ocean Basin in the Paleo-Asian Ocean.The Geleaobao syenogranite and monzogranite in Abaga Banner,Xilin Gol League,the middle of the Chaganaobao-East Ujimqin Banner tectonic magmatic belt,north and central Inner Mongolia,have important implications for revealing the closure time of the Hegenshan Paleo-ocean.Taking the Geleaobao granite as the research object,zircon U-Pb age,rock geochemistry and Hf isotope research were carried out to explore its formation age,rock genesis and tectonic environment.The study shows that the syenogranite and monzogranite were emplaced at 321.3±2.8 Ma and 306.7±2.4 Ma respectively.The rock is generally rich in SiO₂,poor in CaO,MgO,P₂O₅,TiO₂,moderate in K₂O+Na₂O,Al₂O₃ and Fe₂O₃^T.It belongs to the highpotassium calc-alkaline series of rocks;enriched in light rare earths and trace elements such as Rb,Th,U,Zr,Hf,etc.,deficient in heavy rare earths and trace elements such as Ba,Sr,Nb,etc.,and have negative Eu anomalies;The zircon ε_Hf（t） values of the two types of rocks vary from+7.6 to+13.1,corresponding to the twostage model age of 511～928 Ma.Comprehensive analysis shows that the Geleaobao syenogranite and monzogranite were intruded in Late Carboniferous and belong to differentiated Ⅰ-type granites.The rocks were formed in the island arc environment of the subduction zone and are the product of the subduction of the Hegenshan Paleo-ocean.The identification and determination of the Geleaobao Late Carboniferous arc magmatic rocks indicate that the Hegenshan Paleo-ocean Basin of the Paleo-Asian Ocean was not closed in the Late Carboniferous,but was in the process of northward subduction of the ocean.更多还原