陆相页岩非晶态二氧化硅半定量分析新方法——以鄂尔多斯盆地延长组样品为例

通过扫描电镜观察和全岩矿物X-射线衍射实验图谱分析发现，鄂尔多斯盆地延长组页岩中含有一定量的非晶态二氧化硅。现有的3种计算非晶态二氧化硅含量的方法都有一定的缺陷：化学溶蚀方法分析周期长、且对其他矿物有一定程度的溶解，影响了定量分析的精度；X-射线衍射定量分析法需要计算非晶态二氧化硅衍射图谱上圆丘散射曲线的积分强度，人为误差较高；增量法需要配制标样，但有些种类纯矿物难以获得，标样难以配制，而且误差较高。在总结前人研究的基础上，提出了全岩矿物X-射线衍射与微区矿物定量分析相结合的方法来计算多相体系中非晶态二氧化硅含量这一问题。该方法避开了前人所提出方法的缺点，分别计算得到了结晶态石英含量与二氧化硅含量，从而间接计算出非晶态二氧化硅含量，利用该方法求得鄂尔多斯盆地延长组2个样品非晶态二氧化硅含量分别为3.4%和14.02%。

A New Method for Semi-quantitative Analysis of Amorphous SiO2 in Terrestrial Shale:A Case Study about Yanchang Formation Shale,Ordos Basin

Yanchang Formation shale of Ordos Basin contains a certain amount of amorphous SiO₂,which has been proved by SEM observation and X-ray diffraction analysis of bulk rock.The three methods proposed by now to calculate the quantity of amorphousSiO₂ have their own flaws.The disadvantages of chemical denudation are experimental period and unconvinced accuracy because of dissolving other minerals.Quantitative analysis of amorphous silica by X-ray diffraction possesses high personal error on the integrated intensity of dome-shaped scattering curve in XRD spectrum of amorphousSiO₂.The doping method has high deviation and needs to compound standard sample,while some kinds of pure minerals are hard to obtain.On the basis of summarizing previous researches,a new method that combines QEMSCAN and XRD is proposed for the issue of amorphousSiO₂ calculation in multiphase system.The new method avoids the flaws in approaches which have been proposed,and calculates the amount of amorphousSiO₂ indirectly according to the quantities of quartz andSiO₂ measured respectively.