内蒙古中北部格勒敖包晚石炭世花岗岩成因及其对贺根山洋闭合时限的约束  

The origin of the Late Carboniferous granite in the Geleaobao area,north and central Inner Mongolia and its constraints on closure time of the Hegenshan Paleo-ocean

作　　者：曹磊 张成 张青 姜春伟 李奥冰 邵永旭 汪兴韦 刘启凡 付乐兵[1] CAO Lei;ZHANG Cheng;ZHANG Qing;JIANG Chunwei;LI Aobing;SHAO Yongxu;WANG Xingwei;LIU Qifan;FU Lebing(China University of Geosciences(Wuhan)College of Resources,Wuhan,430074;Geological Survey and Research Institute of Inner Mongolia,Hohhot,010020;Inner Mongolia Key Laboratory of Magmatic Mineralization and Ore-Prospecting,Hohhot,010020)

机构地区：[1]中国地质大学(武汉)资源学院,武汉430074 [2]内蒙古自治区地质调查研究院,呼和浩特010020 [3]内蒙古自治区岩浆活动成矿与找矿重点实验室,呼和浩特010020

出　　处：《地质论评》2025年第2期452-470,共19页Geological Review

基　　金：内蒙古自治区科学技术厅科技计划项目(内蒙古阿巴嘎旗北部银铅锌多金属矿成矿背景、机制及找矿方向)的成果。

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±2.8 Ma、306.7±2.4 Ma侵位,岩石总体富SiO_(2),贫CaO、MgO、P_(2)O_(5)、TiO_(2),K_(2)O+Na_(2)O、Al_(2)O_(3)、Fe_(2)O_(3)^(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511~928 Ma。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。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 SiO_(2),poor in CaO,MgO,P_(2)O_(5),TiO_(2),moderate in K_(2)O+Na_(2)O,Al_(2)O_(3) and Fe_(2)O_(3)^(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 zirconε_(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.

关 键 词：晚石炭世 I型花岗岩 新生地壳 俯冲 贺根山洋 闭合时限 锡林郭勒盟阿巴嘎旗 

分 类 号：P61[天文地球—矿床学]