REAL
MagyarClear Cookie - decide language by browser settings

Water concentrations and hydrogen isotope compositions of alkaline basalt hosted clinopyroxene megacrysts and amphibole clinopyroxenites: the role of structural hydroxyl groups and molecular water

Kovács, István János and Demény, Attila and Czuppon, György and Lécuyer, Christophe and Fourel, Francois and Xia, Qunke and Liu, Jia and Pintér, Zsanett and Király, Edit and Török, Kálmán and Szabó, Ábel and Deloule, Etienne and Falus, György and Fancsik, Tamás and Zajacz, Zoltán and Sándorné Kovács, Judit (2015) Water concentrations and hydrogen isotope compositions of alkaline basalt hosted clinopyroxene megacrysts and amphibole clinopyroxenites: the role of structural hydroxyl groups and molecular water. Contributions to Mineralogy and Petrology. ISSN 1432-0967 (Submitted)

WarningThere is a more recent version of this item available.
[img] Text
CTMP-S-15-00213.pdf - Submitted Version
Restricted to Repository staff only
Download (3MB)

Abstract

The aim of this study was to determine both 'water' contents (as OH- and H2O) and δD values of several clinopyroxene samples from alkaline basalts. These parameters were first obtained from five clinopyroxene samples using both the classical 'off-line' vacuum extraction technique and the 'on-line' high-temperature pyrolysis technique. Blanks measured with the 'on-line' gas extraction techniques were low enough to prevent any contamination by atmospheric water vapour. The comparison of data has revealed that the 'on-line' procedure is more effective for the extraction of 'water' from clinopyroxenes and, consequently, this 'on-line' technique was applied to ten additional clinopyroxene samples. Sample δD values cover a similar range from -95‰ to -45‰ (VSMOW) regardless the studied locations, whereas the total 'water' content varies from 1150 to 2570 ppm. The structural hydroxyl content of clinopyroxene samples measured by micro-FTIR spectrometry varies from ~0 to 476 ppm expressed in molecular water equivalent. There is a weak negative correlation between the total water concentrations determined by mass spectrometry and FTIR, thus indicating that considerable proportion of the 'water' may be present in (nano)-inclusions. It is observed, however, that the structural hydroxyl concentration - apart from linopyroxenes separated from amphibole clinopyroxenite xenoliths - correlates positively with the δD values of clinopyroxene megacrysts for each locality, indicating that structurally bond hydrogen in clinopyroxenes may have δD values higher than molecular water in inclusions. This implies that that there may be a significant hydrogen isotope fractionation for structural hydroxyl during crystallization of clinopyroxene while for molecular water there may be no or only negligible isotope fractionation.

Item Type: Article
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 > QE06 Petrology. Petrography / kőzettan, petrográfia
Depositing User: Dr. István János Kovács
Date Deposited: 03 Oct 2015 03:32
Last Modified: 03 Oct 2015 03:32
URI: http://real.mtak.hu/id/eprint/29457

Available Versions of this Item

Actions (login required)

Edit Item Edit Item
EPrints Logo
Repository of the Academy's Library is powered by EPrints 3 which is developed by the School of Electronics and Computer Science at the University of Southampton. More information and software credits.