内蒙古半沟地区紫苏碱长花岗岩的年代学、同位素地球化学及构造意义  

The chronology,isotope geochemistry and tectonic significance of alkalic feldspar charnockite in Bangou area,Inner Mongolia

作　　者：杜润康 常青松[3,4,5] 王惠初 初航 李小伟 田辉 王兆进[6] 刘永江 DU RunKang;CHANG QingSong;WANG HuiChu;CHU Hang;LI XiaoWei;TIAN Hui;WANG ZhaoJin;LIU YongJiang(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,MOE and College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Qingdao Marine Science and Technology Center,Qingdao 266237,China;China University of Geosciences(Beijing),Beijing 100083,China;Tianjin Centre,China Geological Survey,Tianjin 300170,China;Precambrain Geological Research Centre,China Geological Survey,Tianjin 300170,China;Beijing Institute of Mineral Geology,Beijing 101500,China)

机构地区：[1]深海圈层与地球系统前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,青岛266100 [2]海洋矿产资源实验室,青岛海洋科技中心,青岛266237 [3]中国地质大学(北京),北京100083 [4]中国地质调查局天津地质调查中心,天津300170 [5]中国地质调查局前寒武纪地质研究中心,天津300170 [6]北京市矿产地质研究所,北京101500

出　　处：《岩石学报》2024年第11期3536-3551,共16页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42372238);天津市自然科学基金项目(23JCYBJC00550)联合资助.

摘　　要：为进一步探讨华北克拉通古-中元古代构造演化过程,本文对位于华北克拉通北缘孔兹岩系与怀安片麻岩接触界限附近、侵入TTG片麻岩的紫苏碱长花岗岩进行了地质年代学及地球化学研究。锆石U-Pb测年结果表明,该紫苏碱长花岗岩的结晶年龄为1792±19Ma;此外,分析样品的主量元素显示高硅、贫镁铁、准过铝质-弱过铝质特征,属高钾钙碱性I型花岗岩;同时,微量元素具有右倾式稀土配分模式、Eu呈正异常、富集大离子亲石元素、亏损高场强元素的特征。锆石εHf(t)呈负值(-12.1~-6.2),εNd(t)=-4.5~-9.4,具有相对富集的同位素组成。锆石Hf和Nd同位素单阶段模式年龄分别为2.41~2.62Ga、2.40~2.61Ga,与年龄为~2.5Ga的TTG片麻岩对应值一致。岩石地球化学及Nd-Hf同位素证据指示紫苏碱长花岗岩源自碰撞后伸展抬升阶段TTG片麻岩的重熔,标志着华北克拉通古元古代造山运动结束。The Bangou area is located in the contact position between the Trans-North China Orogen(TNCO)and the Khondalite Belt,and as a result,it is an important area for studying the tectonic evolution of the North China Craton(NCC).To enhance our understanding of the tectonic evolution of the NCC during the Paleo-Mesoproterozoic,this study investigates the geochronology and geochemistry of the alkalic feldspar charnockite that intrudes the tonalite-trondhjemite-granodiorite(TTG)near the contact boundary between the khondalite belt and TTG gneiss on the northern margin of NCC.Zircon U-Pb isotopic dating results indicate that the alkalic feldspar charnockite was formed around 1.79Ga.Major element analysis reveals the granite is high in silicon,low in magnesium and iron,and ranges from metaluminous to slightly peraluminous with characteristics of high-potassium calc-alkaline I-type granite.Trace element analysis shows that it has a right-leaning rare earth element(REE)distribution pattern with a positive Eu anomaly,enrichment in large ion lithophile elements,and depletion in high field strength elements.ZirconεHf(t)andεNd(t)values for the analyzed samples of the alkalic feldspar charnockite are-12.1~-6.2 and-4.5~-9.4 respectively,suggesting a relative enrichment of these isotopic compositions.The Hf and Nd isotope single-stage model ages of the analyzed zircons are 2.41~2.62Ga and 2.40~2.61Ga,which are consistent with those of the~2.5Ga TTG gneiss.Geochemical and Nd-Hf isotope evidence indicate that the alkalic feldspar charnockite was originated from remelting of the TTG gneiss.During this time,the Western Block and Eastern Block of the NCC had collided around 1.85Ga,leading to an overall uplifting at 1.82~1.80Ga which was followed by a post-collisional extension between 1.80~1.78Ga.The alkalic feldspar charnockite is an I-type granite formed in a post-collisional environment.Such a granite activity has not been reported so far in this region,and thus,the study of the alkalic feldspar charnockite in this paper provides n

关 键 词：华北克拉通 紫苏碱长花岗岩 锆石U-PB年代学 Nd-Hf同位素 地球化学 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]