Isotope geochemistry of fluid inclusions in Permian halite with implications for the isotopic history of ocean water and the origin of saline formation waters

L. Paul Knauth, Mark A. Beeunas

Research output: Contribution to journalArticlepeer-review

196 Scopus citations

Abstract

δD and δ18O values have been determined for fluid inclusions in 45 samples of Permian halite. The inclusions are enriched in 18O relative to the meteoric water line but are depleted in D relative to ocean water. Inclusions with the more positive δ-values coincide with the isotopic composition expected for evaporating sea water which follows a hooked trajectory on a δD-δ18O diagram. Inclusions with more negative δ-values may represent more highly evaporated sea water but probably reflect synsedimentary or diagenetic mixing of meteoric water with evaporite brines. The isotope systematics in these inclusions are sufficiently similar to those of a modern evaporite pan to indicate that Permian sea water was isotopically similar to modern sea water. Connate evaporite brines can have negative δ-values because of the probable hooked isotope trajectory of evaporating sea water and/or synsedimentary mixing of evaporite brines with meteoric waters. Subsurface formation waters composed of mixtures of remnant primary evaporite brines and later meteoric waters may be more common than previous isotopic evidence has suggested.

Original languageEnglish (US)
Pages (from-to)419-433
Number of pages15
JournalGeochimica et Cosmochimica Acta
Volume50
Issue number3
DOIs
StatePublished - Mar 1986

ASJC Scopus subject areas

  • Geochemistry and Petrology

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