摘要
内蒙古苏尼特右旗哈达恩格尔A型花岗岩位于索伦—林西缝合带内,岩性为正长花岗岩和二长花岗岩,侵位于下二叠统大石寨组中。LA-ICP-MS锆石U-Pb测年结果显示哈达恩格尔A型花岗岩侵位年龄为151.9±0.7 Ma,形成时代为晚侏罗世。地球化学特征研究显示,该岩体富硅(SiO2=71.36%~74.81%)、富碱(Na_(2)O+K_(2)O=8.12%~10.05%),贫钙(CaO=0.71%~0.96%)和镁(MgO=0.18%~0.28%);负Eu异常显著(δEu=0.12~0.15),Rb、Th、U、K、Ga元素较富集,而Ba、Sr、P、Ti元素相对亏损,且10000 Ga/Al(2.43~3.37)、K_(2)O/MgO(16.07~33.17)、(Na_(2)O+K_(2)O)/CaO(8.45~12.56)值较高,显示出A型花岗岩特征。在地球化学图解分类判别图解上,哈达恩格尔花岗岩显示A2型花岗岩特征,反映其形成于后造山伸展环境。同时联系岩浆起源温压条件,表明岩体可能为后造山阶段浅部低压环境下先前俯冲板块板片断离引发幔源玄武质岩浆底侵作用导致壳源含斜长石的角闪石质岩石在脱水条件下部分熔融成因。哈达恩格尔A型花岗岩为晚侏罗世蒙古—鄂霍茨克构造域造山后伸展作用的产物,和中亚造山带东段散布的其他A型花岗岩共同指示中晚侏罗世中下地壳伸展活动。
Lying along the Solonker-Linxi collisional orogenic suture zone in Sonid Youqi of Inner Mongolia,the Hadaengeer A-type granite intruded into the Lower Permian Dashizhai Formation.LA-ICP-MS zircon U-Pb dating yielded a weighted average age of 151.9±0.7 Ma.The age suggests that the granite was emplaced in the Late Jurassic.The granite is geochemically characterized by high SiO2(71.36%~74.81%)and alkali(Na_(2)O+K_(2)O=8.12%~10.05%),but low CaO(0.71%~0.96%)and MgO(0.18%~0.28%).The obvious negative Eu anomaly(δEu=0.12~0.15),relative enrichment of Rb,Th,U,K and Ga,depletion of Ba,Sr,P and Ti,as well as high 10000 Ga/Al(2.43~3.37),K_(2)O/MgO(16.07~33.17),(Na_(2)O+K_(2)O)/CaO(8.45~12.56)values show the characteristics of A-type granite.According to the chemical subdivision diagrams of the A-type granitoids,the Hadaengeer A-type granite belongs to A2-type granitoid,which was formed and emplaced in a post-collisional extension setting.At the same time,in connection with the temperature and pressure conditions of magma origin,it shows that the pluton may be caused by the partial melting of hornblende rocks containing plagioclase in the crust under the condition of dehydration caused by the underplating of mantle derived basaltic magma caused by the separation of previously subducted plate fragments in the shallow low-pressure environment in the post orogenic stage.Furthermore,together with other A-type granites scattered in the eastern block of the Central Asian Orogenic Belt,the Hadaengeer A-type granite is recognized as the product of the post-orogenic extension of the Mongolian-Okhotsk tectonic domain in the Late Jurassic,which indicates the extensive middle-lower crust extension in the Middle-Late Jurassic.
作者
谢燕
张夏炜
闫姝敏
许展
刘志斌
郭菁华
李英杰
XIE Yan;ZHANG Xia-wei;YAN Shu-min;XU Zhan;LIU Zhi-bin;GUO Jing-hua;LI Ying-jie(Hohhot General Survey of Natural Resources Center,China Geological Survey,Hohhot 010010,Hohhot,China;Hebei GEO University,Shijiazhuang 050031,China;Inner Mongolia Nonferrous Geological Mining(Group)Co.Ltd,Hohhot 010050,China;Geological Survey and Research of Inner Mongolia Autonomous Region,Hohhot 010020,China)
出处
《河北地质大学学报》
2024年第2期10-20,共11页
Journal of Hebei Geo University
基金
科技基础资源调查专项(2022FY101700)
中国地质调查局项目(12120114083201)。
关键词
A型花岗岩
晚侏罗世
后造山伸展
内蒙古苏尼特右旗
A-type granite
Late Jurassic
post orogenic extension
Sonid Youqi of Inner Mongolia
