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Contributions to Mineralogy and Petrology

, Volume 149, Issue 1, pp 57–84 | Cite as

An integrated microtextural and chemical approach to zircon geochronology: refining the Archaean history of the Napier Complex, east Antarctica

  • Nigel M. KellyEmail author
  • Simon L. Harley
Original Paper

Abstract

Integrated textural and chemical characterisation of zircon is used to refine the U–Pb geochronology of the Archaean, ultra-high temperature Napier Complex, east Antarctica. Scanning electron microscope characterisation of zircon and the rare earth element compositions of zircon, garnet and orthopyroxene are integrated to place zircon growth in an assemblage context, thereby providing tighter constraints on the timing of magmatic and metamorphic events. Data indicate that magmatism occurred in the central and northern Napier Complex at ca. 2,990 Ma. A regional, relatively low-pressure metamorphic event occurred at ca. 2,850–2,840 Ma. Mineral REE data from garnet-bearing orthogneiss indicate that ca. 2,490–2,485 Ma U–Pb zircon ages provide an absolute minimum age for the ultrahigh temperature (UHT) foliation preserved in this rock. Internal zircon zoning relationships and estimated zircon-garnet DREE values from paragneiss suggest that an absolute minimum age of ultra-high temperature metamorphism is ca. 2,510 Ma, but that it is more likely to be older than ca. 2,545 Ma. We suggest that the high proportion of published zircon U–Pb data with ages between ca. 2,490–2,450 Ma reflects late, post-peak zircon growth and does not date the timing of peak UHT metamorphism.

Keywords

Zircon Metamorphic Event Metamorphic Zircon Zircon Growth Igneous Zircon 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgements

The authors would like to acknowledge Lance Black (Geoscience Australia) for providing the grain mounts and samples and permission to re-use previously collected data. Access to SIMS was provided through NSS support at the National Environment Research Council Ion Microprobe facility, University of Edinburgh. Other analytical costs were supported through a Royal Society grant to SLH. The authors would also like to thank Nicola Cayzer (SEM), Peter Hill (EMP), Richard Hinton and John Craven (SIMS) for analytical assistance at the School of GeoSciences, University of Edinburgh, and Mark Fanning, Research School of Earth Sciences, ANU, for assistance with SHRIMP II. NMK would like to acknowledge salary and additional support through a Royal Society of Edinburgh/SEELLD Research Fellowship. The authors would like to thank E. Grew and M. Whitehouse for careful and constructive reviews of this manuscript.

Supplementary material

SupTab1-ZrcREE.pdf

SupTab1-ZrcREE.pdf (82 kb)
(pdf 841 KB)

SupTab2-OpxREE.pdf

SupTab2-OpxREE.pdf (11 kb)
(pdf 117 KB)

SupTab3-GrtREE.pdf

SupTab3-GrtREE.pdf (10 kb)
(pdf 101 KB)

SupTab4-RepOpxGrt.pdf

SupTab4-RepOpxGrt.pdf (8 kb)
(pdf 86 KB)

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© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Grant Institute of Earth Science, School of GeosciencesUniversity of EdinburghEdinburghUK

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