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四川广元上寺剖面广泛发育条带状、层状、团块状、结核状硅质岩。通过对上寺上二叠统硅质岩野外观察、取样,室内手标本观察及对其中的8块硅质岩样品进行元素地球化学的分析,对上寺上二叠统共8块硅质岩样品进行岩石学及地球化学特征研究,重点分析其成因。结果表明,硅质岩化学成分以SiO2为主,质量分数为73.05%~94.47%(平均87.1%),Fe,Mn含量较低,Al/(Al+Fe+Mn)值在0.54~0.70之间,平均值为0.63,在Al-Fe-Mn三角图解中,样品全部落在生物及非热液沉积区,MnO/TiO2值大部分小于0.5。硅质岩的大部分微量元素远远小于地壳克拉克值,V/(V+Ni)值均小于0.83,反映沉积环境为富氧;稀土元素总量较低,LREE/HREE平均值为5.84,δCe值变化范围0.20~1.30,为负异常且差异较大,δEu值变化范围1.01~4.10,较弱正异常,稀土元素北美页岩标准化曲线总体较平坦,略有右倾趋势。综合分析认为,硅质来源较复杂,生物来源为其主要来源,深部热水及火山作用为其次要来源,其中热液的注入与始于中二叠世的火山活动有关,硅质岩的形成以生物化学沉积为主,热水沉积为辅,硅质沉积环境为富氧的台盆相。
Sichuan Guangyuan Temple profile widely developed strip, stratified, massive, nodular chert. By observing the Permian siliceous rocks in the upper temple, sampling and observing the hand specimens of the upper part of the temple, and analyzing the elemental geochemistry of eight chevron samples, a total of eight samples of Permian silicic rocks Petrology and geochemistry characteristics of the study, focusing on the analysis of its causes. The results show that the chemical composition of siliceous rocks is mainly SiO2, the mass fraction is 73.05% ~ 94.47% (average 87.1%), the content of Fe and Mn is low and the value of Al / (Fe + Mn) is between 0.54 and 0.70 , With an average of 0.63. In the Al-Fe-Mn triangle plot, the samples all fell in biological and non-hydrothermal sedimentary zones with most of the MnO / TiO2 values less than 0.5. Most of the trace elements in the cherts are much smaller than the crustal value of the crust, and the values of V / (V + Ni) are all less than 0.83, indicating that the sedimentary environment is oxygen-rich. The total amount of rare earth elements is relatively low with an average LREE / HREE of 5.84 and δCe The values range from 0.20 to 1.30, with negative anomalies and large variances. The δEu values range from 1.01 to 4.10, with a weaker positive anomaly. The North American shale normalization curve is generally flat with a slight rightward dip. According to a comprehensive analysis, the source of siliceous rock is more complex, the source of its origin is its main source, and deep hot water and volcanism are its secondary sources. The hydrothermal infilling is related to the volcanic activity from the Middle Permian. The formation of cherts The main biochemical sedimentation, supplemented by hot water, siliceous sedimentary environment for the oxygen-rich basin phase.