Abstract:

The Yanchang Formation shale of Ordos Basin contains a certain amount of amorphous SiO2, which is proved by SEM observations and X-ray diffraction analyses of bulk rocks. Three methods proposed to calculate the quantity of amorphous SiO2 have their own flaws. The disadvantages of chemical denudation are experimental period and dissolution of other minerals. XRD quantitative analysis possesses high personal errors in the integrated intensity of dome-shaped scattering curves in XRD spectrum of amorphous SiO2. The doping method has high deviation and needs to compound standard sample. On the basis of summarizing previous researches, a new method that combines QEMSCAN and XRD is proposed for calculating the amorphous SiO2 in a multiphase system. The new method avoids the flaws in the three approaches, and calculates the amount of amorphous SiO2 indirectly according to the quantities of quartz and SiO2 measured, respectively. However, super high experimental cost is the main factor to limit the method for wide use.

Key words: SEM, QEMSCAN, amorphous SiO2, XRD, Ordos Basin