High-precision oxygen isotope analysis of picogram samples reveals 2 µm gradients and slow diffusion in zircon

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doi: 10.2138/am.2007.2697
Authors:Page, F. Zeb; Ushikubo, T.; Kita, N. T.; Riciputi, L. R.; Valley, J. W.
Author Affiliations:Primary:
University of Wisconsin-Madison, Department of Geology and Geophysics, Madison, WI, United States
Other:
Oak Ridge National Laboratory, United States
Volume Title:American Mineralogist
Source:American Mineralogist, 92(10), p.1772-1775. Publisher: Mineralogical Society of America, Washington, DC, United States. ISSN: 0003-004X
Publication Date:2007
Note:In English. 32 refs.; illus.
Summary:Ion microprobe analysis with a sub-micrometer diameter spot reveals a sharp, 2 µm gradient in oxygen isotope ratio proving that oxygen diffusion in zircon is slow even under prolonged high-grade metamorphism. The data are consistent with an oxygen diffusion coefficient of 10-23.5±1 cm2/s. Furthermore, this gradient is found in a zircon that contains clear textural evidence of recrystallization in nearby regions. This finding shows that through careful textural and chemical analysis, primary information can be extracted from a zircon that has also undergone partial recrystallization. The oxygen isotope ratios found in zircon have been used to infer magmatic and pre-magmatic histories, including the presence of liquid water on the surface of earliest Earth. Recently, these interpretations have been questioned with the assertion that zircon may not retain its primary oxygen isotope signature through metamorphism. The slow diffusion confirmed by these results supports interpretations that assume preservation of magmatic compositions. [R.A.H.]
Sections:Apparatus and techniques; Geochemistry; Mineral data
Mineral Groups:Ortho-and ring silicates
Subjects:Diffusion; Facies; Granulite facies; Granulites; Ion probe data; Isotope ratios; Isotopes; Mass spectra; Metamorphic rocks; Migmatites; Nesosilicates; O-18/O-16; Orthosilicates; Oxygen; Silicates; Spectra; Stable isotopes; Zircon; Zircon group; Adirondack Mountains; New York; Saratoga County New York; United States
Coordinates:N424700 N432300 W0733500 W0741200
Abstract Numbers:07M/4172
Record ID:2007117242
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, copyright, Mineralogical Society of America, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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