小秦岭熊耳群火山岩锆石U-Pb年龄及其地球化学特征  

Zircon U-Pb Age and Geochemical Characteristics of Xiong′er Group Volcanic Rocks from Xiaoqinling Area

作　　者：呼延钰莹 路玉[1,2,3,4] Huyan Yuying Lu Yu(Department of Geology State Key Laboratory of Continental Dynamics, Northwest University, Xi＇an,710069, China China University of Petroleum, Beijing 102249, China China University of Geosciences,Beijing 100083, China)

机构地区：[1]西北大学地质系,西安710069 [2]西北大学大陆动力学国家重点实验室,西安710069 [3]中国石油大学(北京),北京102249 [4]中国地质大学(北京),北京100083

出　　处：《地质科技情报》2016年第5期1-8,共8页Geological Science and Technology Information

基　　金：国家基础科学人才培养基金地质学科学研究培训项目(XDCX2013-14);2013年国家大学生创新与训练计划(201310697022)

摘　　要：熊耳群火山岩是华北陆块结晶基底形成后规模最大、涉及范围最广的火山活动产物,其时代归属一直存在争议。研究获得小秦岭地区熊耳群火山岩LA-ICP-MS锆石207Pb/206Pb年龄加权平均值为（1 810±41）Ma（MSWD=0.16）。综合河南和山西等地熊耳群火山岩测年结果,笔者认为熊耳群火山岩的时限很可能为1.81~1.75Ga,属于哥伦比亚超大陆碰撞作用晚期。该套火山岩主要由玄武安山岩和安山岩组成,具有较高的K_2O、FeO和低的A1_2O_3、MgO、CaO含量,反映岩石具有高钾弱碱性的特点;岩石的稀土元素总量高,REE分配曲线呈右倾型,具轻微Eu负异常;富集大离子亲石元素（K、Rb、Ba）,亏损高场强元素（Nb、Ta、Ti）。火山岩具有与＂岛弧型＂相似的稀土和微量元素特征,为典型的俯冲成因类型。Xiong＇er Group volcanic rocks are the largest magmatism in scale after the formation of the crystalline basement of the North China Craton.Controversy has long existed over its age.We have obtained for the first time the U-Pb age（1 810±41Ma）of zircon from volcanic rocks of the Xiong＇er Group.In combination with ages of other Xiong＇er Group volcanic rocks distributed in Henan and Shanxi,we suggest that the age of the Xiong＇er Group is most likely in the range of 1.81-1.75 Ga,showing an era of Late Columbia.The lithology consists mainly of black basaltic andesites and andesites without the characteristics of continental rift environment.Additionally,petrochemical and geochemical analyses reflect that the volcanic rocks of high potassium alkaline,higher K_2O and FeO with lower Al_2O_3,MgO,CaO.TheΣREE patterns show right-oblique feature and comparatively negative Eu anomaliy.Trace elements illustrate enrichment of LILE（large ion lithophile elements）such as K,Rb,Ba and depletion of HFSE（high field strength elements）such as Nb,Ta and Ti.The REE distribution patterns and trace elements characteristics of volcanic rocks in Xiong′er Group are similar to those formed in subduction-related,continental margin volcanic arcs.

关 键 词：熊耳群火山岩 U-Pb锆石 华北克拉通 哥伦比亚超大陆 

分 类 号：P588.14[天文地球—岩石学]