An ⁵⁷Fe Mo ¨ssbauer spectral study of vermiculitization in the Palabora Complex, Republic of South Africa

Author： Badreddine R. Grandjean F. Vandormael D. Fransolet A.-M. Long G. J.

ISSN： 1471-8030

Source： Clay Minerals, Vol.35, Iss.4, 2000-09, pp. : 653-663

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

Two phlogopite, two mixed-layer phlogopite-vermiculite, and two vermiculite samples collected from the Palabora Complex of South Africa have been investigated at 295 K by X-ray diffraction, chemical analysis, and Mössbauer spectroscopy. In addition the temperature dependence of the Mössbauer spectra has been measured between 95 and 295 K for one phlogopite and one mixed-layer sample. The results of the chemical analyses and the Mo ¨ssbauer spectra improve our knowledge of the vermiculitization process in the Palabora Complex. Both techniques indicate oxidation of the Fe ions during the sequence: phlogopite → mixed-layer → vermiculite. Further, the Mössbauer spectra indicate that Fe oxidation occurs mainly in the octahedral sites and suggest that migration and oxidation of the Fe²⁺ ions from the octahedral sites to the tetrahedral sites may occur during the transformation of phlogopite into a mixed-layer phase. Finally, the vermiculitization process involves both Fe oxidation and loss of K with a concomitant increase in the Mg content.