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Book Chapter

Gondwana margin evolution from zircon REE, O and Hf signatures of Western Province gneisses, Zealandia

By
Joe Hiess
Joe Hiess
1
Division of Earth and Environmental Sciences, Korea Basic Science Institute, South Korea
2
School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand
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Keewook Yi
Keewook Yi
1
Division of Earth and Environmental Sciences, Korea Basic Science Institute, South Korea
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Jon Woodhead
Jon Woodhead
3
School of Earth Sciences, University of Melbourne, Australia
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Trevor Ireland
Trevor Ireland
4
Research School of Earth Sciences, The Australian National University, Australia
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Mark Rattenbury
Mark Rattenbury
5
GNS Science, Lower Hutt, New Zealand
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Published:
January 01, 2015

Abstract

U–Th–Pb dated zircons from Western Province paragneisses and orthogneisses were analysed for rare earth element (REE) concentrations, as well as oxygen and hafnium isotopic compositions. Experiments performed in situ using a sensitive high-resolution ion microprobe (SHRIMP) and laser ablation multicollection inductively coupled plasma mass spectrometer (LA-MC-ICPMS) allow better understanding of crustal growth on the Zealandia margin of Gondwana from the micron scale. Paragneiss zircons were probably derived from similar sources to those that supplied the regional Ordovician Greenland Group and correlative southern Australian and Antarctic meta-sedimentary rocks. Detrital zircon grains record variable REE patterns relating to magmatic and metamorphic crystallization processes operating prior to and following Ordovician deposition. δ18O and ɛHf(T) values trace major phases of juvenile crust formation and subsequent reworking in provenance sources, signifying an increase in the recycling of compositionally diverse, evolved crustal materials through time. Orthogneiss zircons relate to two episodes of magmatism that record similar REE concentration patterns. Devonian zircons have elevated δ18O and un-radiogenic ɛHf(T); Cretaceous zircons record more primitive δ18O and radiogenic ɛHf(T). Both orthogneiss suites require thorough mixing of mantle-derived magmas with a component of Greenland Group rocks. The relative proportion of this crustal contamination is c. 20–50% for the Devonian orthogneisses and c. 10–40% for the Cretaceous orthogneisses. Orthogneiss protolith materials were largely hybridized prior to and during zircon crystallization, suggesting that plutonic assembly occurred over restricted structural levels. These results demonstrate the ability of zircon to retain detailed petrogenetic information through amphibolite-facies metamorphism with excellent fidelity.

Supplementary material:

Analytical methods and data are available at www.geolsoc.org.uk/SUP18755

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Contents

Geological Society, London, Special Publications

Continent Formation Through Time

N. M. W. Roberts
N. M. W. Roberts
NERC Isotope Geosciences Laboratory, UK
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M. Van Kranendonk
M. Van Kranendonk
University of New South Wales, Australia
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S. Parman
S. Parman
Brown University, USA
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S. Shirey
S. Shirey
Carnegie Institution of Washington, USA
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P. D. Clift
P. D. Clift
Louisiana State University, USA
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Geological Society of London
Volume
389
ISBN electronic:
9781862396654
Publication date:
January 01, 2015

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