摘要
大兴安岭中生代火山岩的成因和构造背景一直存在争议。内蒙古西乌旗地区发育大面积的晚中生代火山岩,是中国东部巨型火山岩带的重要组成部分。本文对西乌旗罕乌拉地区白音高老组火山岩开展了野外地质、岩石学、锆石U-Pb同位素年代学、地球化学研究,以便对其岩石成因和构造背景给予制约。白音高老组火山岩主要由流纹岩及流纹质火山碎屑岩等一套中酸性火山岩组成。采集其中的球粒流纹岩和英安斑岩进行LA-ICP-MS锆石UPb测年,测年锆石的CL图和Th/U值(0.34~1.25)指示其为岩浆成因锆石,测年结果分别为(140±0.8)Ma和(133±0.7)Ma,表明这套火山岩的形成时代为早白垩世早期。岩石地球化学研究表明,白音高老组火山岩属高钾钙碱性系列,具高硅、富碱、贫镁、钙,高FeOT/MgO比值,低Mg#值、Nb/Ta比值的特征;相对富集轻稀土元素,亏损重稀土元素;大部分样品富集LILE,而亏损Ba、Sr和HFSE,具A型花岗岩地球化学特征,形成于伸展构造背景,为地壳部分熔融的结果。结合区域中生代火山岩的空间展布特征,认为该火山岩形成应与蒙古—鄂霍茨克洋闭合碰撞后伸展和古太平洋板块的俯冲作用有关。
There exist different opinions concerning the petrogenesis and tectonic background of Mesozoic volcanic rocks developed in the Da Hinggan Mountains.The Late Mesozoic volcanic rocks in the Xi Ujimqin Banner of Inner Mongoliais a very important part of the huge volcanic rock belt in eastern China.The authors studied the volcanic rocks of Baiyingaolao Formation in Hanwula of Xi Ujimqin Banner in such aspects as field occurrence,petrology,zircon U-Pb isotopic geochronology and geochemisty in order to constrain their petrogenesis and tectonic background.The volcanic rocks of Baiyingaolao Formation are composed of rhyolite and volcanic clastic,which are a set of felsic volcanic rocks.The cathodoluminescence(CL)images of analyzed zircons of the pyromeride and dacite porphyry from Baiyingaolao Formation and their Th/U ratios(0.34-1.25)imply the igneous origin.LA−ICP−MS U−Pb dating shows that their ages are about(140±0.8)Ma and(133±0.7)Ma respectively,suggesting the early period of Early Cretaceous.Petrological and geochemical data reveal that the rocks belong to the high potassium calc-alkaline rock series characterized by rich Si and alkali,poor magnesium and calcium,high FeOT/MgO ratio and low Mg#,Nb/Ta ratio.LREE are richer than HREE.The trace element geochemistry is characterized evidently by enrichment of LILE,depletion of Ba,Sr and HFSE.All these geochemical characteristics of rocks show an affinity with the A-type granites,which were most probably formed in an extensional setting and originated from the partial melting of the crust.Combined with spacial distribution of the Mesozoic volcanic rocks,the authors hold that they were probably related to the post-orogenic extension following the closure of the Mongol−Okhotsk orogen,and were also affected by the subduction of the Paleo−Pacific plate.
作者
张晓飞
陈国超
周毅
李沅柏
滕超
王必任
庞振山
曹侃
魏均启
ZHANG Xiaofei;CHEN Guochao;ZHOU Yi;LI Yuanbai;TENG Chao;WANG Biren;PANG Zhenshan;CAO Kan;WEI Junqi(Development and Research Centre,China Geological Survey,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing,100083,China;Mineral Exploration Technical Guidance Center,Ministry of Natural Resources,Beijing 100083,China;Cores and Samples center of Natural Resources,China Geological Survey,Yanjiao 065201,Hebei,China;Nanyang Institutte of Technology,Nanyang 47300,Henan,China;Inner Mongolia geological prospecting Co.,Ltd.Hohot 010010,InnerMongolia,China;Key Laboratory of Rare Mineral,Ministry of Land and Resources,Wuhan 430034,China)
出处
《中国地质》
CAS
CSCD
北大核心
2019年第6期1410-1432,共23页
Geology in China
基金
国家自然科学基金（41802222）
中国地质调查局项目“内蒙古1:5万呼格吉勒图、巴彦华、巴彦布拉格、彦吉嘎庙幅区域地质调查”（1212011220453）和“矿集区矿产调查及深部找矿预测”（DD20190570）
自然资源部稀土稀有稀散矿产重点实验室开放基金项目（KLRM-KF201902）联合资助~~
关键词
大兴安岭
西乌旗
白音高老组
早白垩世
A型花岗岩
伸展构造环境
地质调查工程
Da Hinggan Mountains
Xi Ujimqin Banner
Baiyingaolao Formation
Early Cretaceous
A-type granite
extensional environment
geological survey engineering
