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东秦岭地区早古生代的二郎坪群海相火山沉积建造中广泛发育有硅质岩建造,这些硅质岩形成于同一时代但因后期成岩演化而产生了结晶程度和有序度的差异。鉴于此,选择西峡、嵩县、南召三地的二郎坪群硅质岩进行了常量元素地球化学特征及有序度的研究。研究结果表明,该硅质岩的SiO2含量为84.75%~94.12%、平均89.09%,SiO2/(K2O+Na2O)值26.69~114.78、平均65.67,SiO2/Al2O3值10.48~61.52、平均30.58,它们极好的吻合大陆边缘环境的热水沉积硅质岩特征;Raman分析结果表明,硅质岩在该研究中的特征Raman位移有394,464,465和467cm-1,石英的特征峰经高斯拟合后的FWHM值按照“嵩县→南召→西峡”逐渐降低,这反映了嵩县、南召、西峡的硅质岩有序度和结晶程度依次逐渐升高。然而,硅质岩中SiO2含量分别为嵩县地区87.36%最低,南召地区硅质岩89.57%其次,西峡地区硅质岩90.35%最高。据此,常量元素中SiO2的含量与有序度之间存在同步递增的趋势,这反映硅质岩内石英的SiO2含量和有序度在成岩过程中增大的同时还可能存在对杂质元素的“剔除作用”。然而,这种成岩演化中的杂质剔除作用应该并不是导致硅质岩全岩常量元素含量差异的决定性因素。在研究中,Raman光谱分析极好的揭示了二氧化硅的有序度,这可能是探究硅质岩后期成岩演化的重要手段。
The Early Paleozoic Elain Paleoehysol volcanic sediments in the eastern Qinling area were mainly composed of chert. These cherts were formed in the same era but resulted in differences in crystallinity and degree of order due to late diagenetic evolution. In view of this, the study on the elemental geochemical characteristics and orderliness of the Erlangping group chert in Xixia, Songxian and Nanzhao was conducted. The results show that the SiO2 content of the cherts is 84.75% -94.12% with an average of 89.09% and the values of SiO2 / (K2O + Na2O) are 26.69-114.78 with an average of 65.67 and SiO2 / Al2O3 values are 10.48-61.52 with an average of 30.58. The results of Raman analysis show that the characteristic Raman shifts of the cherts in this study are 394, 464, 465 and 467 cm-1, respectively. The characteristic peaks of quartz are characterized by Gaussian fitting FWHM According to “Song County → Nanzhao → Xixia” gradually decreased, which reflects the Songxian, Nanzhao, Xixia degree and degree of orderly degree of crystallization of the siliceous gradually increased. However, the content of SiO2 in cherts is the lowest in 87.36% of Songxian area, the 89.57% in Nanzhao area, and the highest in Xixia area. Accordingly, there is a trend of increasing the content of SiO2 in the elemental order with the degree of order, which reflects that the SiO2 content and degree of quartz in the siliceous rocks increase during diagenesis, “Culling effect”. However, the removal of this type of diagenetic evolution should not be the decisive factor in the differences in the contents of the total rock elements in the cherts. In the study, Raman spectroscopy revealed the excellent degree of ordering of silica, which may be an important means to explore the late diagenetic evolution of cherts.