摘要
大兴安岭位于中亚造山带东段,为蒙古—鄂霍茨克洋、古亚洲洋、环太平洋三大构造域的复合部位,构造-岩浆活动强烈,是研究东北地区中生代构造-岩浆演化的最佳窗口。为了厘清大兴安岭中段岩体成因和构造意义,以大兴安岭中段金江沟岩体侏罗纪花岗岩为研究对象,开展了系统的锆石U-Pb同位素测年和岩石地球化学研究。锆石U-Pb年代学研究结果显示:中细粒花岗闪长岩成岩年龄为(165±1)Ma,成岩时代为中侏罗世;中细粒正长花岗岩成岩年龄为(152±1)和(147±1)Ma,中粗粒二长花岗岩成岩年龄为(148±1)Ma,成岩时代均为晚侏罗世。岩石地球化学研究结果显示:花岗闪长岩和二长花岗岩样品具有低硅、贫镁铁钛,低TFeO/MgO、Zr/Hf值,相对富集Th、Rb、U、Ce、La、Hf等元素,亏损Sr、Nb、Ba、Ti、P等元素特征,具有I型花岗岩地球化学特征,岩浆来源于下地壳火成岩物质部分熔融源区。正长花岗岩具有富硅、高钾、贫镁铁钛,低TFeO/MgO、Zr/Hf值,分异指数相对偏高,较强铕负异常,相对富集Th、Rb、U、Hf、 Ce、La、Nd元素,亏损Sr、Nb、Ba、Ti、P等元素特征,具有属于高分异I型花岗岩地球化学特征,岩浆来源于下地壳火成岩物质部分熔融源区。结合年代学和地球化学特征,中细粒花岗闪长岩形成于同碰撞构造环境,中细粒正长花岗岩和中粗粒二长花岗岩形成于造山后伸展构造环境,与蒙古—鄂霍茨克洋自西向东剪刀式闭合作用相关,并限定了蒙古—鄂霍茨克缝合带西段最终闭合时间为中侏罗世晚期。
Great Xing’an Range is located in the eastern part of the Central Asian orogenic belt.It is a composite part of the Paleo Asian Ocean,circum Pacific Ocean and Mongolia Okhotsk Ocean.Having strong tectonic magmatic activity,it is the best window to study the Mesozoic tectonic magmatic evolution in Northeast China.The authors studied the Jurassic granitoids in the Jinjianggou of Central Great Xing’an Range,and performed systematic analyses of zircon U Pb chronology and whole-rock elemental geochemistry.The zircon U-Pb age data indicate that petrogenic ages of medium-fine grained granodiorite is(165±1)Ma,the diagenetic ages belong to Middle Jurassic,the petrogenic ages of medium-fine grained syenogranite and medium-coarse grained monzogranite are(152±1)Ma,(147±1)Ma and(148±1)Ma,with their diagenetic ages belong to Late Jurassic.Geochemical data show that the granodiorite and monzogranite samples have low silicon,and are poor in magnesium,iron and titanium,TFeO/MgO ratio and Zr/Hf ratio;They are enriched in Th,Rb,U,Ce,La,Hf and poor in Sr、Nb、Ba、Ti、P,and have geochemical characteristics of type I granite.The magma was originated from the source area of partial melting of igneous material in the lower crust.The syenogranite samples are enriched in silicon,high in potassium,poor in magnesium,iron and titanium,low in TFeO/MgO ratio and Zr/Hf ratio,relatively high in differentiation index,strong europium negative anomaly,relatively rich in Th,Rb,U,Hf,Ce,La,Nd elements,and deficient in Sr,Nb,Ba,Ti,P and other elements,and has geochemical characteristics belonging to highly differentiated type I granite.The magma was originated from the source area of partial melting of igneous material in the lower crust.Combined with the chronology and geochemical characteristics,the medium-fine grained granodiorite was formed in the syn-collision tectonic setting,and medium-fine grained syenogranite and medium-coarse grained monzogranite were formed in post-orogenic extensional tectonic environment,which were related to the scissor closure of the Mongol-Okhotsk Ocean from west to east.We believe that the final closing time of the western section of the Mongol-Okhotz suture zone is the Late Middle Jurassic.
作者
张国宾
冯玥
赵忠海
宋学权
何云龙
孔金贵
Zhang Guobin;Feng Yue;Zhao Zhonghai;Song Xuequan;He Yunlong;Kong Jingui(Department of Earth Science and Engineering,Shanxi Institute of Technology,Yangquan 045000,Shanxi,China;College of Mining,Liaoning Technical University,Fuxin 123000,Liaoning,China;Liaoning Chemical Geological Exploration Institute Co.,Ltd.,Jinzhou 121007,Liaoning,China)
出处
《吉林大学学报(地球科学版)》
北大核心
2025年第5期1564-1585,共22页
Journal of Jilin University:Earth Science Edition
基金
国家自然科学基金项目(42372108)
辽宁省教育厅面上基金项目(LJ2019JL027)
山西工程技术学院科研启动基金项目(2024QD-15)。
