Comparison of Fluorescence Spectroscopy and Plasma-Mass Spectrometry Results of the Meso/Cenozoic Basic Rocks in SE China and Its Geo-Implication

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.