Publication details

Iron redox reactions in the tourmaline structure: High-temperature treatment of Fe3+-rich schorl

Investor logo

FILIP Jan BOSI Ferdinando NOVÁK Milan SKOGBY Henrik TUČEK Jiří ČUDA Jan WILDNER Manfred

Year of publication 2012
Type Article in Periodical
Magazine / Source Geochimica et Cosmochimica Acta
MU Faculty or unit

Faculty of Science

Field Geochemistry
Keywords crystal-structure; heat-treatment; ferric-iron; chemical-composition; site occupancies; dravite series; Mn-tourmaline; chemistry; Mössbauer; Fe
Description We present a detailed study of thermally-driven oxidation and reduction of Fe in the structure of schorl (as the most widespread tourmaline), Fe2+-bearing olenite and fluor-schorl. The principal Fe3+-rich tourmaline investigated in this study is a natural schorl sample from a unique occurrence in peralkaline rocks near Cancrinite Hill, east of Bancroft, southern Ontario. Tourmaline samples were thermally-treated in air and hydrogen at temperatures of 700, 800 and 900 C to oxidize or reduce the structural Fe. High-temperature changes were continuously monitored using 57Fe Mössbauer and infrared spectroscopy. Proportions of Fe2+ and Fe3+ vary as a function of the heat treatment. An increase in Fe3+ up to 100% after heating in air at 700 C was observed, whereas only small changes in the Fe3+/Fetot ratio after heating under hydrogen at 700 C was revealed. Partial deprotonation/protonation represents charge compensation for the oxidation/reduction of Fe at the Y and Z sites.
Related projects:

You are running an old browser version. We recommend updating your browser to its latest version.

More info