Oxygen isotope systematics indicating large-scale circulation of fluid in granitic rocks from southwest Sweden

Niels Munksgaard, Hubert Peter Zeck

Research output: Contribution to journalArticle

Abstract

In the Precambrian basement of SW Sweden two formations of granitic rocks have been strongly recrystallized but have preserved their granitic texture. Most magmatic crystals have been replaced by green-schist-facies mineral assemblages. δ18O whole-rock values for the granitic rocks vary from +1.7‰ to +8.2‰ (relative to SMOW) and extend below the normal range for granitic rocks (+6 to +10‰). Quartz-K-feldspar pairs show 18O16O fractionations of +5.4‰ and +7.8‰, indicating disturbance of magmatic equilibrium fractionations. It is concluded that the O-isotope redistribution took place during the pervasive recrystallization of the rocks, under the influence of a large-scale flux of water (partly) of meteoric origin, probably in a convective hydrothermal system set up by the intrusion of the granites themselves. Estimation of pre-alteration δ18O whole-rock values for one of the granitic units suggests a partly S-type origin.
Original languageEnglish
Pages (from-to)239-246
Number of pages8
JournalChemical Geology
Volume51
Issue number3-4
DOIs
Publication statusPublished - Oct 1985
Externally publishedYes

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