Iron redox reactions in the tourmaline structure: High-temperature treatment of Fe3+-rich schorl
| Autor: | Henrik Skogby, Jiří Tuček, Jan Filip, J. Čuda, Manfred Wildner, Milan Novák, Ferdinando Bosi |
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| Rok vydání: | 2012 |
| Předmět: |
010504 meteorology & atmospheric sciences
Tourmaline Hydrogen Chemistry Analytical chemistry Mineralogy chemistry.chemical_element Protonation 010502 geochemistry & geophysics 01 natural sciences Peralkaline rock Redox Cancrinite Geochemistry and Petrology Mössbauer spectroscopy Chemical composition 0105 earth and related environmental sciences |
| Zdroj: | Geochimica et Cosmochimica Acta. 86:239-256 |
| ISSN: | 0016-7037 |
| Popis: | 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 Mossbauer 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. |
| Databáze: | OpenAIRE |
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