INFLUENCE OF IRON ON THE KINETICS OF FORMATION OF CHRYSOTILE NANOTUBES OF COMPOSITION (Mg, Fe)3Si2O5 (OH)4 UNDER HYDROTHERMAL CONDITIONS

Abstract

It is known that natural serpentine-group minerals often contain FeO, Fe2O3, Al2O3, and minor amounts of NiO, Cr2O3, MnO, and CoO. Fe3+ and Al3+ may substitute for Mg2+ in the octahedral sites and in part for Si4+ in the tetrahedral sites, and other cations occur in octahedral coordination. These substitutions affect the unit-cell parameters and properties of the minerals. The presence of iron oxides in serpentines is very common: up to 16 wt % were reported in lizardite and up to 21 wt %, in antigorite. The iron analog of antigorite, greenalite, occurs in nature. The maximum content of iron oxides in chrysotile is lower; in particular, the FeO content varies from a few tenths percent to 9 wt % depending on the formation conditions. Of special interest is the determination of the upper limit of iron oxide incorporation in the structure of chrysotile and the influence of iron oxides on the formation of cylindrically wrapped layers in its structure, which leads to the development of tubes.