Correlations of octahedral cations with OH–, O2–, Cl–, and F– in biotite from volcanic rocks and xenoliths
-
Kevin Righter
,
M. Darby Dyar
Abstract
To understand compositional variation in igneous biotite, full analyses of a suite of biotites of variable composition from volcanic and xenolith parageneses have been completed. Major and minor elements were determined by electron microprobe analysis, water was determined by manometry and SIMS analysis, and Fe3+/Fe2+ was determined by microXANES and Mössbauer spectroscopy. Our new data, together with previous biotite analyses (total of 52 analyses), reveal correlations between O2-(2-F-Cl-OH) and the sum of the octahedral cations Al + Ti + Fe3+ + Cr. This correlation allows estimation of either OH- or Fe3+/Fe2+ as long as one or the other has been determined. The hydroxyl site in most mantle micas contains at least 1.0 O2- atoms per formula unit (apfu), indicating that the oxy-component cannot be ignored. The large oxy-component in melt inclusion micas from the martian meteorite Chassigny does not necessarily indicate oxidized or hydrous magmatic conditions because dehydrogenation may have occurred and/or because the oxy-component may be stable at low oxygen fugacity. The large variation in Ti, Al, and Fe3+ in natural igneous micas is most likely dependent upon bulk compositional differences in each specific system such as variation of aTiO₂ and aAl₂O₃ in silicate melts.
© 2015 by Walter de Gruyter Berlin/Boston
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Artikel in diesem Heft
- Study on adsorption of submicrometer gold on kaolinite by quantum chemistry calculations
- Image distortion in scanning probe microscopy
- Multiple length scale growth spirals on metamorphic graphite {001} surfaces studied by atomic force microscopy
- 29Si MAS NMR study of diopside–Ca-Tschermak clinopyroxenes: Detecting both tetrahedral and octahedral Al substitution
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part I. Local structural environment and substitution mechanism of Gd3+ at the Ca2 site
- Electron paramagnetic resonance spectroscopic study of synthetic fluorapatite: Part II. Gd3+ at the Ca1 site, with a neighboring Ca2 vacancy
- Determination of the H3BO3 concentration in fluid and melt inclusions in granite pegmatites by laser Raman microprobe spectroscopy
- Analysis of natural H2O + CO2 + NaCl fluid inclusions in the hydrothermal diamond anvil cell
- Thermodynamics of the amphiboles: Ca-Mg-Fe2+ quadrilateral
- Phase boundary between rutile-type and CaCl2-type germanium dioxide determined by in situ X-ray observations
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