Disequilibrium partitioning of oxygen isotopes associated with sector zoning in quartz

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doi: 10.1130/0091-7613(1995)023<1103:DPOOIA>2.3.CO;2
Authors:Onasch, Charles M.; Vennemann, Torsten W.
Author Affiliations:Primary:
Bowling Green State University, Department of Geology, Bowling Green, OH, United States
University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Volume Title:Geology (Boulder)
Source:Geology (Boulder), 23(12), p.1103-1106. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613
Publication Date:1995
Note:In English. 32 refs.; illus.
Summary:Fractionation of oxygen isotopes during crystal growth is commonly assumed to be an equilibrium process. We present evidence here that large variations in δ18O values in a zoned vein quartz crystal are the result of disequilibrium partitioning between fluid and crystal. Within a single crystal with well-developed concentric and sector zoning, δ18O values determined with laser extraction techniques on milligram- to submilligram-sized samples range from 4.7 per mil to 7.3 per mil. Core to rim variations within single growth sectors fluctuate by 2.6 per mil, whereas differences between adjacent sectors along the same growth zone can exceed 2.0 per mil. In contrast, fluid-inclusion homogenization temperatures and salinities are relatively constant and show no effect of growth or sector zoning. Differences in δ18O values between sectors along the same growth zone cannot result from variations in the oxygen isotope composition of the fluid and strongly suggest disequilibrium partitioning of oxygen isotopes between fluid and the growing crystal. The cause of this disequilibrium is believed to be due to differences in surface structure and/or growth mechanisms between nonequivalent faces.
Subjects:Cathodoluminescence; Crystal growth; Experimental studies; Fluid inclusions; Fluid phase; Framework silicates; Inclusions; Isotope ratios; Isotopes; O-18/O-16; Oxygen; Partitioning; Phase equilibria; Quartz; Quartz veins; Silica minerals; Silicates; Solid phase; Stable isotopes; Veins; Zoning; Fractionation
Abstract Numbers:96M/4254
Record ID:1996005068
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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