The experimental incorporation of Fe into talc: a study using X-ray diffraction, Fourier transform infrared spectroscopy, and Mössbauer spectroscopy

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Web End = Contrib Mineral Petrol (2015) 170:29

DOI 10.1007/s00410-015-1180-1

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Web End = The experimental incorporation of Fe into talc: a study using Xray diffraction, Fourier transform infrared spectroscopy, and Mssbauer spectroscopy

Juan Carlos Corona1 David M. Jenkins1 M. Darby Dyar2,3

Abstract Talc is a common Mg-rich trioctahedral layer silicate that occurs both as a primary and as a secondary mineral in a wide range of rock types. Substitution of Fe2+

for Mg is fairly extensive in certain rock types, particularly banded iron formations, yet there is relatively limited fundamental crystal-chemical information on this substitution. This study is an experimental investigation of Fe2+ substitution for Mg using X-ray diffraction, infrared spectroscopy, and Mssbauer spectroscopy. Talc was synthesized in 0.5 Fe cation [0.17 XFe, XFe = Fe/(Fe + Mg)] increments

along the join Mg3Si4O10(OH)2Fe3Si4O10(OH)2 over the range of 350700 C, oxygen fugacities (fO2) from ~Ni

NiO to 3.3 log(fO2) units below NiNiO, and at a pressure of 0.2 GPa. High yields of talc without any coexisting Fe-bearing phases were obtained up to 0.33 XFe, beyond which talc coexisted with fayalitic olivine, magnetite, or both, indicating saturation in Fe for syntheses along the talc join. Infrared spectroscopy was used to determine independently the XFe of talc, showing a deviation from the observed and expected composition starting at XFe of 0.37 0.03.

Minor additional solid solution occurred beyond this to a maximum XFe solubility of 0.50. Mssbauer spectroscopy indicated the dominance of octahedral Fe2+ in talc with

Communicated by Othmar Mntener.

* Juan Carlos Corona [email protected]

1 Department of Geological Sciences and Environmental Studies, State University of New York at Binghamton, Binghamton, NY 13902-6000, USA

2 Department of Earth and Environment, Mount Holyoke College, South Hadley, MA 01075-1429, USA

3 Department of Astronomy, Mount Holyoke College, South Hadley, MA 01075-1429, USA

Received: 22 May 2015 / Accepted: 30 July 2015 / Published online: 1 September 2015 Springer-Verlag Berlin Heidelberg 2015

octahedral Fe3+ ranging from 2.9 to 21.5 at.%, depending on the ambient fO2. X-ray diffraction analysis did not conrm the strong dependence of the interplanar spacing...