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'Water' in quartz from various rhyolitic pyroclastic horizons: A new correlation tool?

Biró, Tamás and Kovács, István János and Király, Edit and Falus, György and Karátson, Dávid and Bendő, Zsolt and Fancsik, Tamás and Sándorné Kovács, Judit (2015) 'Water' in quartz from various rhyolitic pyroclastic horizons: A new correlation tool? In: Goldschmidt Conference, 2015. augusztus 15-21., Prága, Csehország.

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Abstract

Structural hydroxyl contents of quartz grains from various rhyolitic pyroclastic density current (PDC) deposits from the Bükk Foreland Volcanic Area, Hungary, were determined by using micro-FTIR spectrometry. Additional trace element analysis and SEM cathodoluminescence imaging were also performed. Structural hydroxyl content (expressed in water equivalent) of volcanic quartz ranges from ~2,0 to ~4,1 ppm, which is lower than those in quartz of igneous, metamorphic and hydrothermal origin. The incorporation of structural hydroxyl is mainly due to coupled H+ + Al3+ substitutions into Si-tetrahedral vacancies of quartz. In addition, the presence of molecular water is also obvious in (nano-)inclusions. The water fugacity (ƒH2O) just prior to the eruption seems to be the main factor controlling the concentration of structural hydroxyl as manifested in its almost homogeneous distribution regardless to the zonation of Al- or Ti-content. Quartz grains from the studied volcanic units are characterized by diagnostic absorption features between 3000 and 3550 cm-1, structural hydroxyl, molecular water, Al- and Ti-contents. This suggests the potential application of water content, the way of hydrogen incorporation and trace element chemistry of volcanic quartz as potential correlation tools. Moreover, a reasonable linear correlation is observed between the integrated area of Si-O bonds-related IR absorption features (between 2110 and 1440 cm-1) and sample thickness up to ~300 μm by studying unoriented quartz crystals. This may enable the analysis of separated quartz crystals without the need for preparing oriented thin sections.

Item Type: Conference or Workshop Item (Poster)
Additional Information: Az Európai Ásványtani Unió legjobb fiatal kutatói poszter díját kapta.
Subjects: Q Science / természettudomány > QD Chemistry / kémia > QD05 Crystallography / kristálytan
Q Science / természettudomány > QD Chemistry / kémia > QD06 Mineralogy / ásványtan
Q Science / természettudomány > QE Geology / földtudományok
Q Science / természettudomány > QE Geology / földtudományok > QE02 Geochemistry / geokémia
Q Science / természettudomány > QE Geology / földtudományok > QE06 Petrology. Petrography / kőzettan, petrográfia
Depositing User: Dr. István János Kovács
Date Deposited: 02 Oct 2015 12:20
Last Modified: 02 Oct 2015 12:20
URI: http://real.mtak.hu/id/eprint/29461

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