Red micas from basal ignimbrites of Mt. Vulture (Italy): interlayer content appraisal by a multi-methodic approach |
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Authors: | Fernando Scordari Emanuela Schingaro Gennaro Ventruti Maria Lacalamita Luisa Ottolini |
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Institution: | (1) Dipartimento Geomineralogico, Università degli Studi di Bari, Via E. Orabona 4, 70125 Bari, Italy;(2) CNR-Istituto di Geoscienze e Georisorse (IGG), Sezione di Pavia, Via Ferrata, 1, 27100 Pavia, Italy |
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Abstract: | The crystal chemistry of red phlogopites from Mt. Vulture (Italy) ignimbrites has been studied by electron microprobe, secondary
ion mass spectrometry (SIMS), single crystal structural investigation and Fourier transform infrared (FTIR) spectroscopy.
The analysed phlogopite has Fe/(Fe + Mg) ∼ 0.35, TiO2 (wt%): 2.8–5.0 and H2O (wt%): 1.24–3.37. Infrared spectra revealed the presence of bands due to the NH4+ and H2O stretching and bending vibrations. The samples belong to the 1M polytype. The bimodal behaviour of several structural parameters allows red micas to be clustered into two distinct groups:
K+ ↔ NH4+, H2O and M3+-vacancy substitutions dominate in the first group; M3+,4+-oxy, in the second group. It has to be pointed out that quantitative analysis of hydrogen (via SIMS) together with the characterization
of the local environment of the anionic site (via FTIR) are fundamental in assessing the correct structural formula and the
substitution mechanisms in micas.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Red phlogopite FTIR spectroscopy SIMS Crystal chemistry |
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