赤峰四家子盆地张家口组火山岩成因研究  

Study on Genesis of Volcanic Rocks from Zhangjiakou Formation in Sijiazi Basin of Chifeng

作　　者：彭艳东[1] 邢德和[2] 卞雄飞[2] 宋维民[2] 

机构地区：[1]东北大学秦皇岛分校,河北秦皇岛066004 [2]沈阳地质矿产研究所,辽宁沈阳110033

出　　处：《东北大学学报（自然科学版）》2011年第8期1190-1194,共5页Journal of Northeastern University(Natural Science)

基　　金：国土资源大调查项目(1212010610510);国家自然科学基金资助项目(40872045)

摘　　要：根据最近几年开展的1∶5万区域地质调查获得的新资料,确认了内蒙古四家子盆地晚侏罗世张家口组的存在,并将张家口旋回火山岩划分为三个亚旋回.火山岩岩性为流纹岩类、粗面岩类和粗安岩类.对该地区火山岩的主量元素和微量元素进行了高精度分析测试,结果显示：火山岩具有高SiO2,Al2O3,K2O,Na2O含量和低MgO,TiO2含量的特征;里特曼指数σ（1.19~4.87）均值为2.47,属高钾钙碱性岩石系列.火山岩富集大离子亲石元素K,Rb,Sr,Zr,Ba,Pb,Li等,相容元素Ti,Co,Ni,Cr,V亏损.火山岩稀土总量较高,稀土配分模式呈右倾型,轻稀土分馏作用高于重稀土的分馏作用,总体显示弱负铕异常和弱的负铈异常.稀土元素具有陆内火山岩的基本特征.火山岩成因及其构造环境的综合研究表明,张家口组火山岩成岩物质主要来源于地壳,火山岩形成于板内环境,其成因以部分熔融为主.According to the data obtained from 1∶50 000 regional geological survey carried out during recent years,the authors confirm the existence of the Zhangjiakou formation of Late Jurassic in the Sijiazi basin,Inner Mongolia.The Zhangjiakou formation can be divided into three subcycles,i.e.,rhyolites,trachyte and trachyandesites.High-precise analysis of the major and trace elements shows that the volcanic rocks are characterized by relatively high SiO2,Al2O3,K2O and Na2O,and comparatively low MgO and TiO2 components.Rittmann index σ（in the range of 1.19 to 4.87） has the average value of 2.47,indicating that the rocks belong to high potassium calcium alkaline rock series.The volcanic rocks are obviously enriched in incompatible elements（K,Rb,Sr,Zr,Ba,Pb and Li）,and depleted in compatible elements（Ti,Co,Ni,Cr and V）.The REE content in the volcanic rocks is high.The distribution pattern is the right-incline.There is a slight low Eu and Ce negative abnormality.The REE characteristics show that the volcanic rocks were generated in the intraplate orogenic belt.The results of the comprehensive study on genesis and tectonic environment indicate that the volcanic rocks were mainly formed by the crust materials in a continental intraplate setting due to partial melting.

关 键 词：四家子盆地 张家口组 地球化学 地壳重熔 板内造山带 

分 类 号：P591[天文地球—地球化学]