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'Water' content of quartz from various rhyolitic ignimbrite horizons: results from unpolarized micro-FTIR analyses on unoriented grains

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Tartalom: http://real.mtak.hu/41027/
Archívum: MTA Könyvtár
Gyűjtemény: Status = Submitted





Type = Article
Cím:
'Water' content of quartz from various rhyolitic ignimbrite horizons: results from unpolarized micro-FTIR analyses on unoriented grains
Létrehozó:
Biró, Tamás
Kovács, István János
Király, Edit
Falus, György
Karátson, Dávid
Bendő, Zsolt
Fancsik, Tamás
Sándorné Kovács, Judit
Kiadó:
Schweizerbart und Borntraeger
Dátum:
2015
Téma:
QD05 Crystallography / kristálytan
QD06 Mineralogy / ásványtan
QE Geology / földtudományok
QE02 Geochemistry / geokémia
QE06 Petrology. Petrography / kőzettan, petrográfia
Tartalmi leírás:
Structural hydroxyl contents of quartz grains from various rhyolitic pyroclastic density
current (PDC) deposits from the BĂĽkk 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 plutonic (granitic), 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 post-eruptive out diffusion of
H+ during cooling seems to be the main factor causing the very low concentration of
structural hydroxyl. This may be also manifested in the almost homogeneous
distribution of structural hydroxyl regardless the considerable zonation in Al- and Ticontent.
Although complete disappearance of structural hydroxyl was possibly
hindered by the cooling effect of phreatomagmatism (excess water-magma interaction
during eruption) and deposition in ashallow submarine environment.
Moreover, a reasonable linear correlation is observed between the integrated area of
Si-O bonds (between 2110 and 1440 cm-1) and sample thickness up to ~300 ÎĽm by
studying unoriented quartz crystals. This may enable the analysis of separated quartz
crystals without the need for preparing oriented thin section providing a more practical
tool to determine structural hydroxyl concentrations.
Nyelv:
magyar
Típus:
Article
NonPeerReviewed
info:eu-repo/semantics/article
Formátum:
text
Azonosító:
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' content of quartz from various rhyolitic ignimbrite horizons: results from unpolarized micro-FTIR analyses on unoriented grains. European Journal of Mineralogy. ISSN 0935-1221 (Submitted)
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