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Juvenile CO 2 in enderbites of Tromøy near Arendal, southern Norway: a fluid inclusion and stable isotope study
Author(s) -
KERKHOF A. M. VAN DEN,
TOURET J. L. R.,
KREULEN R.
Publication year - 1994
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1994.tb00024.x
Subject(s) - geology , inclusion (mineral) , stable isotope ratio , isotope , geochemistry , earth science , mineralogy , physics , quantum mechanics
The enderbites from Tromøy in the central, granulite facies part of the Proterozoic Bamble sector of southern Norway contain dominantly CO 2 and N 2 fluid inclusions. CO 2 from fluid inclusions in quartz segregations in enderbites was extracted by mechanical (crushing) and thermal decrepitation and the δ 13 C measured. Measurement was also made on samples washed in 10% HCl, oxidized with CuO at high temperatures, and step‐wise extracted with progressive heating. Results between the different techniques are systematic. The main results show δ 13 C of ‐4.5±1.5% for crushing and ‐7±2% for thermal decrepitation. δ 13 C is about constant for CO 2 extracted at different temperatures and points to a homogeneous isotopic composition. Due to the presence of carbonate particles and/or induced contaminations for the extraction by thermal decrepitation, the results for the crushing experiments are assumed the most reliable for fluid‐inclusion CO 2 . Very low values of δ 13 C have not been found in enderbite samples and δ 13 C combined with δ 18 O of the host quartzes (8‐11%) indicates juvenile values. In addition, the fluid inclusions were examined by microthermometry and Raman analysis and host quartz by acoustic emission and cathodoluminescence. CO 2 fluid inclusions have varying densities with a frequency maximum of 0.92 g cm ‐3 and generally do not concur with trapping densities at granulite conditions. Textures show that CO 2 must have been trapped in fluid inclusions in one early event, but transformed to different extents during late isothermal uplift without important fractionation of isotope compositions. The present data support a model of intrusion and crystallization of a CO 2 ‐rich enderbitic magma at granuiite conditions.