Unusual Sector Zoning in Lewisian Zircons

J. F. Hoffman and J. V. P. Long
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge

Abstract: An unusual form of sector zoning has been recorded in some Lewisian zircons. The sectors lie in a plane cut perpendicular to the c-axis and are observed as variations in the intensity of cathodoluminescence, and in trace-element concentrations. Sectors radiating from the centre of growth out to the {100} faces exhibit low-intensity cathodoluminescence and are enriched in Y and depleted in Hf and Zr. Those radiating to the {110} faces are brightly luminescent, slightly enriched in Hf and depleted in Y. X-ray diffraction data, and comparison with previous studies of zircons, suggest that the sectors vary slightly in crystallographic orientation, such that the boundaries between sectors form discontinuities in the structure.

Mineralogical Magazine; December 1984 v. 48; no. 349; p. 513-517; DOI: 10.1180/minmag.1984.048.349.05
© 1984, The Mineralogical Society
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