内蒙古阿尔山地区新生代玄武岩及其幔源包体微量元素组成特征  

TRACE ELEMENT CHARACTERISTICS OF CENOZOIC BASALTS AND THEIR MANTLE XENOLITHS SELECTED FROM AERSHAN AREA IN INNER MONGOLIA,CHINA

作　　者：于福生[1] 丛立民[2] 

机构地区：[1]中国石油大学石油天然气成藏机理教育部重点实验室,北京102249 [2]内蒙古自治区115地质队,内蒙古乌兰浩特137400

出　　处：《矿物岩石》2006年第1期29-34,共6页Mineralogy and Petrology

基　　金：中国科学院重要发展方向性项目(KJCXN-01)

摘　　要：内蒙古阿尔山地区新生代火山活动频繁，喷发期次可划分为上新世、更新世、全新世，最新喷发时间约为1900aBP，具有再次喷发的可能。为了探讨活火山源区地幔流体的分布特征，利用中子活化分析和同步辐射X射线荧光微探针分析技术，对阿尔山地区全新世玄武岩及其幔源包体的稀土、微量元素组成特征、地幔包体矿物及其熔融包裹体的微量元素组成特征进行了分析。中子活化分析结果表明，不同产地玄武岩具有相同的稀土配分模式，其中，∑8REE=96．93～114．94，Eu／Sm=0．32～0．37，（La／Lu）N=8.89～12.52；不相客元素蛛网曲线整体右倾，Ba，Ta，Sm具正异常，Th，Zr具负异常，没有明显的Sr异常，说明岩浆上升过程中很少演化和分离结晶；不同产地地幔岩包体中不含包裹体的同类矿物的REE组成相近，反映了不同活火山的地幔源区REE组成特征相同；不同产地地幔岩包体同类矿物及其内部包裹体同步辐射X射线荧光微探针分析表明具有相同的微量元素曲线分布形态；这些特征说明阿尔山活火山群分布区地幔流体不存在显著的不均一性。There were three times of Cenozoic volcanic eruptions which could be divided into Pliocene,Pleistocene and Holocene in Aershan area of Inner Mongolia. The nearest eruption activity happened in 1900a. B. P,which implies that it may erupt again in the future. In order to probe into the distribution feature of mantle fluid under the active volcanoes ,rare elements and trace elements of basalts,xenoliths and melt inclusions were analyzed by INAA and Synchrotron Radiation X-ray Fluorescence （SRXF）. Basalt samples from different locations in Aershan area analyzed by instrumental neutron activation analysis （INAA） have the same distribution patterns of REE and trace elements,such as ∑8REE=96.93-114.94,Eu/Sm=0.32-0. 37,LaN/LuN=8. 89-12. 52. The similar Primary mantle-normalized patterns of incompatible elements for Cenozoic volcanic rocks with normal abnormity of element Ba,Ta, Sm and without Sr abnormity, indicate that magma did not differentiate. The similar REE contents of the same minerals without inclu sions from different xenoliths suggest that the mantle source of different active volcanoes have the same REE contents. The REE content differences between same minerals with and without melted inclusions selected from same mantle xenolith sample indicate that the melted inclusions are rich in REE. The same patterns of trace elements of the same inclusions and host minerals from different xenoliths analyzed by SRXF imply that the mantle fluid has no remarkable heterogeneity in Aershan area.

关 键 词：地幔包体 微量元素 中子活化分析 同步辐射 阿尔山玄武岩 

分 类 号：P588.145[天文地球—岩石学]