内蒙古中部额布图铜镍硫化物矿床形成时代与岩石成因  

Formation Age and Petrogenesis of Ebutu Cu-Ni Sulfide Deposit in Central Inner Mongolia,China

作　　者：焦建刚[1,2,3] 郭天牧 闫馨云 马云飞[1,5] 高栋 JIAO Jian-gang;GUO Tian-mu;YAN Xin-yun;MA Yun-fei;GAO Dong(School of Earth Science and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Key Laboratory of Western China's Mineral Resources and Geological Engineering of Ministry of Education,Chang'an University,Xi'an 710054,Shaanxi,China;Xi'an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Chang'an University,Xi'an 710054,Shaanxi,China;Research Institute of Exploration and Development,Yumen Oilfield Company,PetroChina,Jiuquan 735000,Gansu,China;Inner Mongolia Branch of China National Geological Exploration Center of Building Materials Industry,Hohhot 010010,Inner Mongolia,China;School of Geographical Sciences,Lingnan Normal University,Zhanjiang 524048,Guangdong,China)

机构地区：[1]长安大学地球科与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]长安大学西安市关键金属成矿与高效利用重点实验室,陕西西安710054 [4]中国石油玉门油田分公司勘探开发研究院,甘肃酒泉735000 [5]中国建筑材料工业地质勘查中心内蒙古总队,内蒙古呼和浩特010010 [6]岭南师范学院地理科学学院,广东湛江524048

出　　处：《地球科学与环境学报》2023年第5期1063-1079,共17页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(92162213);内蒙古自治区地质勘查基金项目(2020-KY05);岭南师范学院人才引进专项项目(ZL22039);西安市关键金属成矿与高效利用重点实验室开放基金项目(300102273502)。

摘　　要：内蒙古中部地区横跨中亚造山带与华北陆块北缘,区内广泛分布岩浆铜镍硫化物矿床(点)。额布图铜镍硫化物矿床是区域规模较大、品位较高的岩浆铜镍硫化物矿床之一。以额布图铜镍硫化物矿床中含长橄榄辉石岩为主要研究对象,开展了系统的矿物学、岩相学、矿相学、锆石U-Pb年代学、岩石地球化学和Sr-Nd同位素等方面的研究,探讨了额布图镁铁—超镁铁质岩体的成岩成矿时代及岩石成因;在此基础上,综合区域地质资料简要分析了矿床找矿潜力,为实现进一步铜镍找矿突破提供指导。结果表明:额布图镁铁—超镁铁质岩体中含长橄榄辉石岩LA-ICP-MS锆石U-Pb年龄为(326.0±2.1)Ma,属早石炭世,形成于古亚洲洋向华北陆块俯冲的岛弧环境。含长橄榄辉石岩SiO_(2)含量(质量分数,下同)为44.62%~55.81%(平均含量为51.60%),MgO含量为27.45%~33.10%(平均含量为30.32%),CaO含量为1.15%~2.22%(平均含量为1.61%);具有轻稀土元素富集、重稀土元素亏损的右倾型球粒陨石标准化稀土元素配分模式以及Eu弱负异常;Sr-Nd同位素地球化学研究结果表明,额布图镁铁—超镁铁质岩体(^(87)Sr/^(86)Sr)_(i)值为0.7085~0.7123(平均值为0.7106),(^(143)Nd/^(144)Nd)_(i)值为0.5117~0.5118(平均值为0.5118),ε_(Nd)(t)值为-10.57~-8.07(平均值为-8.91)。综合上述研究,额布图镁铁—超镁铁质岩体的原始岩浆为经历了俯冲板片流体交代的富集岩石圈地幔部分熔融的产物,原生岩浆主要为高镁玄武质岩浆,同时在上升侵位过程中经历了较强的地壳物质混染。由于地壳硫的加入以及富硅地壳混染,促进了硫化物熔离成矿。结合区域地质资料及最新探矿工程控制情况,额布图镁铁—超镁铁质岩体深边部有较好的找矿潜力,应将理清岩浆流动方向、寻找隐伏岩体及深部岩浆通道作为下一步找矿重点。The central region of Inner Mongolia that straddles across the Central Asian Orogenic Belt(CAOB)and the northern margin of the North China Block,widely develops magmatic Cu-Ni sulfide deposits(or occurrences).The Ebutu Cu-Ni sulfide deposit is one of the large scales and high-grade magmatic Cu-Ni sulfide deposits within this region.The plagioclase-bearing olivine pyroxenite of Ebutu Cu-Ni sulfide deposit was selected as the main research object by systematic mineralogy,petrography,mineralography,zircon U-Pb geochronology,petrogeochemistry and Sr-Nd isotopes to discuss the diagenetic and metallogenic age and petrogenesis of Ebutu mafic-ultramafic intrusions;based on the integration of regional geological data,the metallogenic potential of Ebutu Cu-Ni sulfide deposit was also briefly discussed,in order to provide suggestions for further breakthrough in Cu-Ni prospecting.The results show that the plagioclase-bearing olivine pyroxenite of Ebutu mafic-ultramafic intrusions yields a LA-ICP-MS zircon U-Pb weighted mean age of(326.0±2.1)Ma,belonging to the Early Carboniferous,indicating that it forms in an island arc setting during the Paleo-Asian ocean subducted to the North China Block.The plagioclase-bearing olivine pyroxenite showes SiO 2 contents of 44.62%-55.81%with the average of 51.60%,MgO contents of 27.45%-33.10%with the average of 30.32%,and CaO contents of 1.15%-2.22%with the average of 1.61%.They are enrichment in light rare earth elements(LREE),depletion in heavy rare earth elements(HREE)and slightly negative Eu anomalies on the right-leaning chondrite-normalized REE pattern.(^(87)Sr/^(86Sr)i,(^(143)Nd/^(144)Nd)i andεNd(t)values vary from 0.7085 to 0.7123 with the average of 0.7106,from 0.5117 to 0.5118 with the average of 0.5118 and from-10.57 to-8.07 with the average of-8.91,respectively.Based on the above studies,it is concluded that the parent magma of Ebutu mafic-ultramafic intrusion probably derives from the partial melting for the enriched lithospheric mantle interacted by the subducted slab-derive

关 键 词：地质年代学 地球化学 岩石成因 铜镍硫化物矿床 镁铁—超镁铁质岩体 内蒙古 中亚造山带 

分 类 号：P611.11[天文地球—矿床学]