内蒙古温都尔庙-集宁地区花岗斑岩年代学、地球化学、Hf同位素特征及其地质意义  

Chronology,Geochemistry and Hf Isotope of Granite Porphyry in Wenduermiao-Jining Area,Inner Mongolia and Its Geological Significance

作　　者：冯帆 徐仲元[1] 董晓杰[1] 石强[1] 王师捷 李长海 Feng Fan;Xu Zhongyuan;Dong Xiaojie;Shi Qiang;Wang Shijie;Li Changhai(College of Earth Sciences,Jilin University,Changchun 130061,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061

出　　处：《地球科学》2021年第6期1973-1992,共20页Earth Science

基　　金：国家自然科学基金项目(Nos.41872203,41872194);吉林省科技厅优秀青年人才基金项目(No.20180520089JH).

摘　　要：为了探讨在温都尔庙-集宁地区古亚洲洋的闭合时限以及演化过程,对该地区花岗斑岩进行了岩相学、地球化学、锆石年代学以及Hf同位素组成分析.锆石U-Pb定年显示,夸子梁花岗斑岩形成于中二叠世(270±3 Ma);乌兰淖尔花岗斑岩形成于中三叠世(241±2 Ma),为区域上首次发现的三叠世花岗岩.两者均有较高的SiO_(2)、Al_(2)O_(3)含量及极低的Mg^(#);轻稀土元素相对富集,重稀土元素相对亏损,存在明显的Eu负异常;富集大离子亲石元素,亏损高场强元素.夸子梁花岗斑岩的锆石ε_(Hf)(t)呈负值(0.25~-12.33),并具有较为古老的Hf二阶段模式年龄(1278~2071 Ma);乌兰淖尔花岗斑岩的锆石ε_(Hf)(t)呈正值(2.03~5.94),并具有较为年轻的Hf二阶段模式年龄(892~1144 Ma).综合分析认为:在中二叠世之前,古亚洲在温都尔庙集宁地区已经闭合;中二叠世期间,区域上处于后碰撞阶段,并产生夸子梁花岗斑岩;晚二叠世-早三叠世,区域上继续碰撞造山;中三叠世期间,处于造山后伸展阶段,并产生乌兰淖尔花岗斑岩.In order to explore the closure time and evolution process of the Paleo Asian ocean in Wenduermiao-Jining area,it analyzes the petrology,geochemistry,geochronology and zircon Hf isotope composition.Zircon U-Pb dating shows that,Kuaziliang granite porphyry formed in the Middle Permian(270±3 Ma),while Wulannaoer granite porphyry formed in the Middle Triassic(241±2 Ma)that is the first Triassic granite discovered in the region.These rocks characterize with high contents of SiO_(2),Al_(2)O_(3),very low Mg^(#)values.They also display enrichment in LREEs and LILEs,depletion in HREEs and HFSEs,with obviously negative Eu anomalies.Kuaziliang granite porphyry exhibits negativeε_(Hf)(t)values(0.25 to-12.33),old Hf isotopic tDM2 from 1278 Ma to 2071 Ma,indicating that it was derived from partial melting of ancient crustal material,while Wulannaoer granite porphyry exhibits positiveε_(Hf)(t)values(2.03-5.94),relatively new Hf isotopic tDM2 from 892 Ma to 1144 Ma,indicating that it was derived from partial melting of juvenile crustal material.Analyzed by synthesis,it speculates that before the Middle Permian,the Paleo-Asian ocean was closed in the Wenduertemple-Jining area;during the Middle Permian,the region is in the post-collision stage,forming the Kuaziliang granite porphyry.During Late Permian through Early Triassic,continuous collision orogeny in the region;the Middle Triassic,the region is in the post-orogenic extension stage,forming the Wulannaoer granite porphyry.

关 键 词：华北克拉通北缘 兴蒙造山带东南缘 古亚洲洋 花岗斑岩 中二叠世 中三叠世 岩石学 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]