Characterization of Iron-Rich Phyllosilicates Formed at Different Fe/Si Ratios

The formation of 2:1 and 1:1 phyllosilicates in Fe-Si-O-H systems occurs in various geological and engineering settings; however, the identification and characterization of these minerals is very challenging due to the limited amount that is accessible, the very small particle size, and often the large degree of heterogeneity of these samples. To overcome these drawbacks, the synthesis of iron-rich phyllosilicates was attempted in this study with an initial Fe/Si molar ratio ranging from 0.50 to 2.33. The synthesis was performed at 150 degrees C under hydrothermal conditions over a period of 7 days. Synthesis products were characterized by X-ray diffraction and fluorescence, by infrared, Raman, and Mossbauer spectroscopies, and by transmission electron microscopy. Results revealed that the stability field of the 2:1 clay mineral was wider than that of the 1:1 clay mineral. The 2:1 clay mineral was less sensitive to redox conditions compared to the 1:1 clay mineral. In addition, a heterogeneity of phases formed (iron oxides, nontronite, cronstedtite, or greenalite) was identified.

Automated summary

The synthesis of iron-rich phyllosilicates with different Fe/Si molar ratios was attempted in this study. The results revealed that the stability field of the 2:1 clay mineral was wider and less sensitive to redox conditions compared to the 1:1 clay mineral. Additionally, heterogeneous phases were formed.