中国东南部中、新生代基性岩荧光光谱与等离子质谱测试结果对比及其地质意义分析

摘要

通过对中国东南部中、新生代基性岩类岩石的荧光光谱和等离子体质谱分析结果的对比研究,发现中生代基性岩SiO2平均含量为±50％,新生代基性岩为±43％,前者属典型基性岩类,后者属超基性岩类.两者在微量元素及稀土元素组成上也有显著差异.中生代基性岩的微量元素和稀土元素标准化配分模式与上陆壳的配分模式相同或相似,而新生代基性岩则与OIB型洋岛玄武岩相同或相似.由此得到的认识是:新生代的基性岩与OIB型洋岛玄武岩一样,均为地幔来源,而中生代的基性岩浆则极有可能来自上陆壳底部,与本区中生代壳内重熔岩浆层的演化有关.%With comparison of the fluorescence spectroscopy and plasma-mass spectroscopy analysis results of the Meso/Cenozoic basic rocks of SE China,the authors found that the average SiO2 content of the Mesozoic basic rocks in this area is about 50％,while that of the Cenozoic basic rocks is about 43％.The former belongs to the basic group and the later to the ultrabasic group in igneous rock classification.Cenozoic basalts,accompanied with high magnesium content and low silica-alumina component,are obviously basic or ultrabasic rocks.Distinctive difference in the content of trace elements and of REE is also presented between the Mesozoic and the Cenozoic basic rocks.Distribution models of both trace elements and REE of the Mesozoic basic rocks are similar to those of the upper crust,and the models of the Cenozoic basic rocks are like those of OIB,indicating that basic rocks of the Cenozoic and OIB should originate from the mantle while that of the Mesozoic is from the bottom part of the upper crust with relationship to the evolution of the Mesozoic crustal magma layer of this area.