赤峰哈拉道口早石炭世花岗闪长岩年代学、地球化学及其地质意义  

GEOCHRONOLOGY AND GEOCHEMISTRY OF THE EARLY CARBONIFEROUS GRANODIORITES IN HALADAOKOU AREA OF CHIFENG CITY:Geological Implication

作　　者：李崴崴 陈井胜[2] 高忠晖 刘淼[2] 李斌[2] 杨帆[2] LI Wei-wei;CHEN Jing-sheng;GAO Zhong-hui;LIU Miao;LI Bin;YANG Fan(Liaoning Institute of Geology and Mineral Resources Co.,Ltd.,Shenyang 110029,China;Shenyang Center of China Geological Survey,Shenyang 110034,China)

机构地区：[1]辽宁省地质矿产研究院有限责任公司,辽宁沈阳110029 [2]中国地质调查局沈阳地质调查中心,辽宁沈阳110034

出　　处：《地质与资源》2020年第3期212-223,共12页Geology and Resources

基　　金：中国地质调查局项目“辽东-吉中地区区域地质调查”(DD20190042);“内蒙古1∶5万敖汉旗、捣格朗营子、新地、铁匠营子幅区域地质矿产调查”(12120113053400).

摘　　要：以内蒙古赤峰哈拉道口地区花岗闪长岩为研究对象,利用锆石LA-ICP-MS U-Pb测年技术进行年代学研究,测试结果为352.4~355.9Ma,显示其形成时代为早石炭世早期,为华北板块北缘早石炭世岩浆岩活动研究提供了新的资料.地球化学特征显示,花岗闪长岩总体上贫Si、Al,总碱量偏高,Eu仅有轻微的亏损,属铝未饱和、高钾钙碱性系列岩石.同时花岗闪长岩具有较高Sr含量,较低的MgO、Y、Yb含量,富集LREEs,亏损HREEs和HFSEs,Sr/Y比值介于34.62~48.43之间,(La/Yb)N比值为15.31~17.14,显示“C型埃达克岩”特征.较高的K2O、Cr、Ni含量和较低的Mg#值说明其不可能是由拆沉下地壳物质的熔融形成,而是形成于增厚下地壳镁铁质岩的部分熔融.微量元素特征显示花岗闪长岩形成于活动大陆边缘弧环境.所以,早石炭世早期,本区处于古亚洲洋板块向南俯冲的大地构造背景.The geochronology of the granodiorites in Haladaokou area of Chifeng City,Inner Mongolia,is studied by zircon LA-ICP-MS U-Pb dating.The test result of 352.4-355.9 Ma indicates that the rocks were formed in the early stage of Early Carboniferous,which provides new data for the research of Early Carboniferous magmatic activity on the northern margin of North China Plate.Geochemically,the granodiorites are generally poor in Si and Al,with high total alkali content and slight Eu depletion,belonging to the Al-unsaturated,high-K calc-alkaline series.Moreover,the granodiorites have high Sr content and low MgO,Y and Yb contents,enrichment of LREEs and depletion of HREEs and HFSEs,with the Sr/Y ratio of 34.62-48.43 and(La/Yb)N ratio of 15.31-17.14,showing the characteristics of C-type adakite.The high K2O,Cr and Ni contents and low Mg#value reveal they cannot be formed by the melting of delamination of lower crust materials,but by the partial melting of thickened lower crust mafic rocks.The characteristics of trace elements indicate that the granodiorites were formed in the active continental margin arc environment.Therefore,the study area was in the geotectonic setting of southward subduction of Paleo-Asian Ocean plate during the early stage of Early Carboniferous.

关 键 词：早石炭世早期 花岗闪长岩 年代学 地球化学 内蒙古 

分 类 号：P588.12[天文地球—岩石学] P597[天文地球—地质学]