大兴安岭中北段大金山地区早侏罗世埃达克质花岗闪长岩的成因及构造环境  

The Origin and Tectonic Environment of the Early Jurassic Adakitic Granodiorite in the Dajinshan Area of the Central and Northern Da Hinggan Range

作　　者：尹志刚[1] 李敏[1] 李文龙 张海 张圣听 宫兆民 李海娜[1] 郝科 庞学昌 YIN Zhi-gang;LI Min;LI Wen-long;ZHANG Hai;ZHANG Sheng-ting;GONG Zhao-min;LI Hai-na;HAO Ke;PANG Xue-chang(School of Mines,Liaoning Technical University,Fuxin Liaoning 123000,China;Qiqihar Branch,Heilongjiang Institute of Geological Survey,Harbin 150000,China)

机构地区：[1]辽宁工程技术大学矿业学院,辽宁阜新123000 [2]黑龙江省地质调查研究总院齐齐哈尔分院,哈尔滨150000

出　　处：《矿物岩石地球化学通报》2019年第1期69-79,共11页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局项目(1212011120671)

摘　　要：对大兴安岭中北段大金山地区的花岗闪长岩进行了锆石LA-ICP-MS U-Pb年代学和岩石地球化学研究,以便了解其形成时代、成因及构造背景。结果表明,花岗闪长岩为早侏罗世(183. 2±1. 0 Ma)岩浆事件的产物,具有较高的SiO_2(>56%)、Al_2O_3(>15%)和较低的MgO(<3%),较高的Na_2O/K_2O值(1. 12～2. 04),为高钾钙碱性岩浆系列;具有较高的Sr含量(>400×10^(-6)),不明显的Eu异常,轻重稀土分异明显,强烈亏损Yb和Y;富集轻稀土元素,具有埃达克岩的地球化学特征。大金山岩体表现为富钾、低镁(Mg~#为38. 70)特征,属于C型埃达克质岩,推测其形成于加厚的玄武质下地壳的部分熔融。早侏罗世埃达克岩的发现表明大兴安岭中北段大金山地区有陆壳加厚的过程,大陆发生过垂向增生;大金山岩体可能形成于蒙古-鄂霍茨克洋俯冲作用下的活动大陆边缘环境。In this paper,the zircon LA-ICP-MS U-Pb geochronology and petrogeochemistry of the granodiorite intrusive body in the Dajinshan area in the central and northern parts of Da Hinggan range have been studied in order to understand its formation age,genesis and tectonic setting. The results show that the granodiorite is the product of the early Jurassic(183. 2±1. 0 Ma) magmatic event with high contents of SiO2(>56%),Al2O3(>15%) and low content of MgO(<3%),and high ratios of Na2O/K2O(1. 12-2. 04),which belong to high potassium calcium alkaline magma series;It is characterized with high Sr contents(>400×10^-6),unobvious Eu anomaly,significant differentiation between LREE and HREE,strong depletion of Yb and Y,and enrichment of LREE,similar to geochemical characteristics of adakite. In addition,it has characters of high potassium and low-magnesium(Mg#38. 70). It belongs to the C-type adakitic rock and is presumed to be derived from the partial melting of the thickened basaltic lower crust. The discovery of early Jurassic adakite shows that a vertical thickening event occurred in the continental crust in the Dajinshan area of the Great Khingan Range at that time. the Dajinshan intrusive body could be formed in the environment of active continental margin resulted from the subduction of the Mongolian-Okhotsk ocean.

关 键 词：早侏罗世 花岗闪长岩 地球化学 埃达克岩 大兴安岭地区 

分 类 号：P588.122[天文地球—岩石学]