四川广元上寺上二叠统硅质岩地球化学特征及成因分析

发布时间：2018-04-12 08:30

本文选题：硅质岩 + 地球化学　；参考：《矿物岩石》2017年01期

【摘要】：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。
[Abstract]:Sichuan Guangyuan Temple section widely banded, laminated, lumpy, nodular siliceous rocks. Through the sampling of the temple on the two Permian siliceous rocks, field observation, observation and analysis of indoor hand specimens of 8 element geochemistry of siliceous rocks samples among them, studied the petrological and geochemical characteristics of two a total of 8 blocks stacked Si chert samples, analysis of the causes of the focus. The results show that the chemical composition of siliceous rocks dominated by SiO2, mass fraction of 73.05%~94.47% (average 87.1%), Fe, Mn were lower, Al/ (Al+Fe+Mn) value is between 0.54~0.70, the average value is 0.63, in the Al-Fe-Mn triangle diagram, sample all on the biological and non hydrothermal sedimentary area, the MnO/TiO2 value of most of the trace elements most less than 0.5. of the siliceous rocks is far less than the Clark values of crust, V/ (V+Ni) values were less than 0.83, reflecting the sedimentary environment is enriched; the total REE is low, LREE/HREE The average value is 5.84, Ce values range 0.20~1.30, negative anomaly and great difference. The Eu values of 1.01~4.10 ranges, weak positive anomalies, REE NASC normalized curve is relatively flat, slightly rightist trend. Comprehensive analysis shows that the silica source is complex, biological sources is the main source of the deep. Hot water and volcano is the second source of the heat injection and began in the Middle Permian volcano, formed by bio chemical sedimentary siliceous rocks, hydrothermal sedimentary siliceous sedimentary environment is enriched by the basin phase.

【作者单位】：中国石油大学(华东)地球科学与技术学院;山东省第八地质矿产勘查院;
【基金】：国家自然科学基金项目(编号:41272123)
【分类号】：P588.244

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