The metamictization of zircon: Radiation dose-dependent structural characteristics
Abstract
A suite of gem zircon samples from Sri Lanka has been studied using infrared (IR) spectroscopy, X-ray diffraction, and chemical analysis. The degree of metamictization of the zircon, as indicated by unit-cell parameters, increases systematically with U-Th content up to the point of total metamictization. The appearance of IR spectra also varies as a function of metamictization; band widths increase and intensities decrease with increasing U-Th contents. Persistence of bands related to Si-O bonds and disappearance of bands related to Zr-O bonds indicates that the structure of metamict zircon consists of distorted and disoriented isolated silica tetrahedra with few if any undisplaced Zr cations. All spectroscopic indicators of crystalline order show that total metamictization is reached at an accumulated radiation dosage of ~4.5 x 10^(15) alpha decay events per mg. Hydrous components enter the structure only after total metamictization, but the amounts are not correlated with U-Th content. In all cases OH was the only hydrous species detected.
Additional Information
© 1991 Mineralogical Society of America. Manuscript received May 21, 1990. Manuscript accepted November 14, 1990. This research was funded in part by National Science Foundation grants EAR-7919987, 8618200, and 8916064. We thank David Gottfried, Heinrich Holland, and Frank Senftle (USGS, Reston, Virginia) for samples included in this work. We thank Rodney Ewing, Franois Farges, and John Hughes for their helpful comments on the manuscript. This study is Caltech contribution no. 4606.Additional details
- Eprint ID
- 38487
- Resolver ID
- CaltechAUTHORS:20130514-103113195
- EAR-7919987
- NSF
- EAR-8618200
- NSF
- EAR-8916064
- NSF
- Created
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2013-05-14Created from EPrint's datestamp field
- Updated
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2019-10-03Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences
- Other Numbering System Name
- Caltech Division of Geological and Planetary Sciences
- Other Numbering System Identifier
- 4606