山东西部中生代青山群火山岩的地球化学特征及其岩石成因

发布时间：2018-04-11 22:36

本文选题：山东西部 + 中生代　；参考：《地质学报》2017年12期

【摘要】：以山东西部西董地区中生代青山群火山岩为研究对象,在进行系统的元素-同位素分析的基础上,探讨其岩浆源区和岩石成因,同时丰富该区域岩石地层的地球化学特征。西董青山群火山岩Si O2含量变化于52.8%~59.8%之间,主要为钙碱性系列岩石,岩石组合为玄武质粗面安山岩-玄武质安山岩-粗面安山岩,Mg O、TFe2O3、Mn O、Ti O2、Ca O与Si O2具有明显的负相关关系,Al2O3和Na2O与Si O2具有正相关关系;微量元素富集Rb、Ba、Th、U和K等大离子亲石元素,亏损Nb、Ta和Ti等高场强元素,稀土元素总量∑REE变化范围为100×10-6~187×10-6,(La/Yb)N比值范围为8.2~11.1,无明显的Eu异常(δEu=0.9~1.02);显示富集且均一的Sr-Nd同位素组成((87Sr/86Sr)t=0.7047~0.7050,εNd(t)=-16.5~-14.2)。西董青山群火山岩的Nd、Sr同位素组成与Si O2缺乏明显负相关关系,Nb/Ta与La/Nb之间不具有负相关关系以及Nb与Th之间具有正相关关系,指示岩浆在上升和演化过程中地壳混染作用对青山群火山岩岩浆化学组成的影响并不显著;火山岩Mg O含量明显高于玄武岩部分熔融形成的熔体,说明青山群中基性火山岩岩浆的形成过程可能与大陆地壳和地幔岩系之间的相互作用有关。综合分析表明,西董中生代青山群火山岩是大陆下地壳物质经拆沉作用于地幔环境中发生部分熔融,与上地幔岩石发生交代作用后进入地表形成。
[Abstract]:To the west of Shandong Xi Dong area of Mesozoic volcano rock of Qingshan group as the research object, based on systematic elemental and isotopic analysis, explore its magma source and petrogenesis, and enrich the regional geochemical characteristics of rocks and strata. Xi Dong Qingshan group volcano rock Si O2 content changes between 52.8%~59.8%, mainly for the calc alkaline series of rocks, the rock is basaltic trachyandesite and trachyte andesite basaltic andesite - Mg, O, TFe2O3, Mn O, Ti O2, Ca O and Si O2 has a significantly negative correlation between Al2O3 and Na2O, Si and O2 have a positive correlation; Rb, enrichment of trace elements Ba, Th, U K and other large ion lithophile elements, Nb, Ta and Ti loss, high field strength elements, the variation range of total rare earth elements Sigma REE 100 * 10-6~187 * 10-6 (La/Yb) N ratio in the range of 8.2~11.1, no obvious Eu anomaly (delta Eu=0.9~1.02); Sr-Nd isotope enrichment and uniform Composition ((87Sr/86Sr) t=0.7047~0.7050, epsilon Nd (T) =-16.5~-14.2). The West Dong Qingshan group volcanic rocks of Nd, Sr and Si isotopic composition of O2 lack of obvious negative correlation between Nb/Ta and La/Nb does not have a strong positive correlation between Nb and negative correlation with Th, indicating the influence on the rise and evolution of magma in the crust contamination of Qingshan group volcano magma chemistry is not significant; volcano rock Mg O were significantly higher than that of partial melts of basalt formation, the interaction between the formation process and continental crust and the upper mantle rocks of Qingshan group mafic lava volcano. Comprehensive analysis shows that the Mesozoic Qingshan group Xi Dong volcano rock is the crust, the mantle delamination in the environment of partial melting, occur metasomatism and upper mantle rocks into the surface form.

【作者单位】：中国地质调查局天津地质矿产研究所;中国地质大学地球科学学院;中国地质调查局武汉地质矿产研究所;
【基金】：国家自然科学基金委员会创新研究群体科学基金项目(编号40521001)资助的成果
【分类号】：P588.14

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