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Stable isotope and chemical compositions of carbonate ocelli and veins in Mesozoic lamprophyres of Hungary

Attila Demeny, Istvan Forizs and Ferenc Molnar
Stable isotope and chemical compositions of carbonate ocelli and veins in Mesozoic lamprophyres of Hungary
European Journal of Mineralogy (October 1994) 6 (5): 679-690

Abstract

Late Cretaceous lamprophyres and carbonatites occurring in Palaeozoic to Mesozoic granites and sedimentary rocks contain carbonate ocelli and veins which show alteration resulting in the formation of disseminated carbonate and clay minerals. Those bodies which intrude granite contain calcite and dolomite whose carbon isotopic compositions (Delta (super 13) C approximately -4.50/00) are within the primary mantle range, whereas the oxygen isotope compositions (Delta ^>18O approximately 140/00) are well outside the range of primary carbonatites. Carbonate ocelli of the lamprophyres were formed by interactions of igneous fluids with xenoliths of sedimentary origin. Interactions with the magma have also changed the composition of limestone xenoliths enclosed in the lamprophyre. Carbon isotopic compositions and calcite-dolomite solvus T measured on calcite ocelli with dolomite rims point to both chemical and isotopic disequilibrium between calcite and dolomite despite apparent complete recrystallization of the original sedimentary material. The isotopic compositions of calcite veins may be attributed to the effects of igneous fluids, exchange of fluids with sedimentary host rocks, oxidation of organic matter or possible degassing of magma and/or magmatic fluids. The former two processes produce calcites with sedimentary Delta ^>13C values and Delta ^>18O values down to 15.00/00, whereas the latter three factors may be responsible for a trend of Delta ^>13C shifts down to -9.0, and Delta ^>18O values up to 24.20/00.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 6
Serial Issue: 5
Title: Stable isotope and chemical compositions of carbonate ocelli and veins in Mesozoic lamprophyres of Hungary
Affiliation: Hungarian Academy of Sciences, Laboratory for Geochemical Research, Budapest, Hungary
Pages: 679-690
Published: 199410
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 45
Accession Number: 1994-054186
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, sketch map
N45°45'00" - N48°30'00", E16°10'00" - E23°00'00"
Secondary Affiliation: Eotvos Lorand University, HUN, Hungary
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199424
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