摘要
在野外地质调查的基础上,选取滹沱群豆村亚群底部四集庄组玄武岩、顶部青石村组玄武岩和东冶亚群中下部河边村组玄武岩,进行岩石学和地球化学研究。分析结果表明:玄武岩主量元素高TiO2、TFeO,低MgO,具有演化的基性岩浆的特征。稀土元素含量相对较高,具有弱—中等程度的轻稀土元素富集,中等程度的轻重稀土元素分异,轻微的Eu异常;玄武岩中Cr、Ni含量变化较大,但与Mg#具有很好的正相关性。微量元素配分图解中具有明显的Sr负异常,部分样品具有Nb、Ta和Ti负异常,无Zr、Hf负异常,与岛弧火山岩不同;同时Nb、Ta无分异,Zr/Hf值较高,具有板内玄武岩浆的特征。综合分析认为,滹沱群玄武岩可能形成于板内裂谷环境。在岩浆上升过程中发生橄榄石与尖晶石的分离结晶作用,同时不同程度地受到地壳的混染。
Based on the field work, this paper focuses on petrology and geochemistry of the metabasalts from Sijizhuang, Qingshicun and Hebiancun formations in Hutuo group. The results show that the basalts are rich in TiO2,TFeO, and poor in MgO, suggesting the features of evolved basic magma. With high concentration of total REE contents, the LREE is moderately enriched, but the Eu anomaly is weak （or slight）. The contents of Cr,Ni in the basalts change greatly and are positively corrrelated with Mg^#. In spidergrams to normalized in NMORB, the basalts in Hutuo group are different from IAB in strongly negative Sr anomaly, Nb, Ta and Ti anomaly in some samples, but the Zr,Hf anomaly is absent. In addition, Nb and Ta in the basalts are not differentiated. The Zr/Hf ratio is higher than that of the MORB, being consistent with that of the intraplate basalt. The basalts of the Hutuo group might erupt in rift environment. In the ascending process of the basic magma, the fractional crystallization of olivine and spinel occurred and the basalts suffered the assimilation of crust materials to varying degree.
出处
《地质通报》
CAS
CSCD
北大核心
2009年第7期867-876,共10页
Geological Bulletin of China
基金
中国地质调查局项目<中国和亚洲早前寒武纪地层划分和对比>(编号:1212010611801)
中国地质科学院地质研究所基本科研业务费项目<华北克拉通中部滹沱群玄武岩时代及形成环境研究>(编号:J0721)
<华北克拉通基底变质作用对哥伦比亚超大陆的制约>(编号:J0907)
全国地层委员会中国主要断代地层建阶研究项目<古元古界滹沱群底界及内部划分框架研究>资助
关键词
五台山区
滹沱群
玄武岩
地球化学
裂谷环境
Wutai Mountains
Hutuo Group
metabasalts
geochemistry
rift environment
