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| Titel |
A Raman model for determining the chemical composition of silicate glasses |
| VerfasserIn |
Danilo Di Genova, Daniele Morgavi, Kai-Uwe Hess, Daniel R. Neuville, Diego Perugini, Donald B. Dingwell |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106849
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| Publikation (Nr.) |
 EGU/EGU2015-6527.pdf |
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| Zusammenfassung |
| Raman spectroscopy is a spectroscopic technique based on inelastic scattering of
monochromatic light which provides information about molecular vibrations of the
investigated sample. Since the discovery of the Raman Effect (1928) in scattered
light from liquids, the Raman investigation has been extended to a large number of
substances at different pressure-temperature conditions. Recently, the Raman instrument
setup has rapidly grown thanks to the progress in development of lasers, charge
coupled devices and confocal systems (see Neuville et al. 2014 for a review). Here we
present the first Raman model able to determine the chemical composition of silicate
glasses.
In this study we combine chemical analysis from magma mixing experiments between
remelted basaltic and rhyolitic melts, with a high spatial resolution Raman spectroscopy
investigation; we focus on tracking the evolution of the Raman spectrum with chemical
composition of silicate glasses.
The mixing process is driven by a recently-developed apparatus that generates chaotic
streamlines in the melts (Morgavi et al., 2013), mimicking the development of magma
mixing in nature. From these experiments we obtained a glassy filament with a
chemical composition ranging from a basalt to a rhyolite. Raman and microprobe
measurements have been performed on a filament of ~1000 μm diameter, every 2.5-20
μm.
The evolution of the acquired Raman spectra with the measured chemical composition
has been parametrized by combining both the Raman spectra of the basaltic and rhyolitic
end-members.
Using the developed Raman model we have been able to determine the chemical
composition (mol% of SiO2, Al2O3, FeO, CaO, MgO, Na2O and K2O) of the investigated
filament. Additionally, the proposed Raman model has been successfully tested using external
remelted natural samples; reference glasses (Jochum et al., 2000), a remelted basalt, andesite
from Etna and Montserrat respectively.
Finally, as the Raman spectrum depends on the silicate structure yielding information
about network-forming structural units (Qn species, where n indicates the number of bridging
oxygen), we combined the deconvoluted Raman spectra, in the rhyolitic field, with the
chemical analyses and abundance of Qn species. This demonstrate how the evolution of
silicate structure might control the bimodal eruptive style (explosive vs effusive) as shown by
silica-rich volcanic systems.
References:
D. Morgavi et al., 2013. Morphochemistry of patterns produced by mixing of rhyolitic
and basaltic melts. JVGR, 253, 87-96.
D. R. Neuville, et al. 2014. Advances in Raman Spectroscopy Applied to Earth and
Material Sciences. Rev. Min. Geochem., 78, 509-541. |
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