摘要
通过紫金山岩体的地球化学分析,系统探讨了岩体的物质组成及其岩浆成分演化特征和可能的动力学演化环境,为鄂尔多斯盆地东部深部岩浆活动-热力作用提供重要信息。紫金山岩体的地球化学特征表明:岩体具有全碱含量较高((K2O+Na2O)=8.64%～16.09%),贫SiO2,根据碱度率图解,判别该岩体属于偏碱性-碱性系列;稀土含量较高,轻稀土富集,轻重稀土元素发生了不同程度的分馏,Eu异常现象不明显。富集大离子亲石元素,而亏损Nb,Ta,Ti等高场强元素。在此基础之上,通过主量元素的氧化物变异图解分析,认为紫金山岩体可能来源于深部相近或统一的原始岩浆源区,在其上侵演化过程中形成了高钾-低钙的碱性系列岩石和低钾-高钙的碱性-偏碱性系列岩石。结合相关判别图解表明,其物质来源至少达到了壳-幔过渡带或其更大的深度层次;构造环境属于板内拉张环境。因此,紫金山岩体所代表的鄂尔多斯盆地燕山晚期的构造热事件是在华北克拉通大规模伸展背景下,深部物质在地壳中浅层或地表作用的结果。
Through the analysis of geochemical Characteristics, the material component, magma evolution and dynamic environment of Zijinshan complex are studied in order to provide important information of deep magmatic activity and thermo genesis in the eastern Ordos Basin. Geochemical analysis reveals that alkali （（K2O＋Na2O）=8.64%-16.09%） contents is high,SiO2 contents is poor. According to alkalinity ratio （AR）, the complex belongs to partial alkaline-alkalic series. It is showed that the content of rare earth elements is relatively high,rich in LREE,and of differentiations between LREE and HREE, with no significant Eu anomalies. The Zijinshan complex enriches in LILE,depletes in HFSE （eg Nb,Ta and Ti,etc）. On the basis of analysis on variation diagram of main elements oxide, Zijinshan complex is considered to be derived from primitive magma source area,and alkaline series rock of high potassium-low calcium and alkaline-partial alkalic series rock of low potassium-high calcium were formed during the emplacement of magma. Discrimination diagrams show that the magma source reaches the depth of crust-mantle transitional zone or even deeper level under a structural environment of continental intra-plate extension. Therefore,Zijinshan complex is resulted from the large-scale stretching of North China Craton, and the deep magmatic activity during the Yanshanian Period in the eastern Ordos Basin.
出处
《矿物岩石》
CAS
CSCD
北大核心
2011年第3期74-81,共8页
Mineralogy and Petrology
基金
国家重点基础研究(2003CB214607)
国家留学基金(200721S073)
关键词
地球化学
岩浆演化
构造环境
紫金山岩体
鄂尔多斯盆地
geochemistry
magmatic evolution
structural environment
Zijinshan complex
Ordos Basin
