TY - JOUR
T1 - Oxygen isotopes in Pilbara Craton zircons support a global increase in crustal recycling at 3.2Ga
AU - Van Kranendonk, Martin J.
AU - Kirkland, Christopher L.
AU - Cliff, John
N1 - Funding Information:
This contribution is published with permission of the Executive Director of the Geological Survey of Western Australia, and is Australian Research Council Centre of Excellence in Core to Crust Fluid Systems publication number 380. The authors acknowledge the facilities, and the scientific and technical assistance of the Australian Microscopy & Microanalysis Research Facility at the Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, a facility funded by the University, State and Commonwealth Governments. The Penglai zircon standard was kindly supplied by Xian-Hua Li. MVK acknowledges support from the University of New South Wales Australia . Elena Belousova, Aaron Cavosie and other anonymous reviewers are thanked for constructive comments which improved this contribution.
Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/7/1
Y1 - 2015/7/1
N2 - Oxygen isotopes were measured in zircon crystals from a suite of Paleo- to Mesoarchean igneous and sedimentary rocks from the Pilbara Craton in order to test prevailing models of early Earth tectonic evolution. Our results indicate that igneous zircon crystals older than 3.2Ga in the Pilbara Craton have mantle-like oxygen isotope signatures, whereas zircon grains younger than c. 3.2Ga show, on average, isotopically heavier δ18O values. Stringent tests on the validity of the isotopically heavy oxygen values - in terms of whether they reflect primary properties of the zircon crystals acquired under magmatic genesis, or the result of later alteration - were conducted in some cases by simultaneous measurement of 16O1H/16O, in conjunction with evaluating more traditional indicators of metamictisation. These data demonstrate that whereas some of the heaviest values are anomalous and due to post-crystallisation alteration via incorporation of water into the zircon structure, others record primary values.The data presented here are used to support a previously documented change in tectonic style in the Pilbara Craton at 3.2. Ga, from early crustal growth through magmatic accretion above upwelling, hot mantle, to crustal growth that involved significant amounts of crustal recycling arising from the onset of modern-style plate tectonics (steep subduction of old cold oceanic lithosphere). These results align with global datasets of oxygen isotopes, and point to a more general change in the geodynamics of Earth associated with the secular decrease in heat output of our planet.
AB - Oxygen isotopes were measured in zircon crystals from a suite of Paleo- to Mesoarchean igneous and sedimentary rocks from the Pilbara Craton in order to test prevailing models of early Earth tectonic evolution. Our results indicate that igneous zircon crystals older than 3.2Ga in the Pilbara Craton have mantle-like oxygen isotope signatures, whereas zircon grains younger than c. 3.2Ga show, on average, isotopically heavier δ18O values. Stringent tests on the validity of the isotopically heavy oxygen values - in terms of whether they reflect primary properties of the zircon crystals acquired under magmatic genesis, or the result of later alteration - were conducted in some cases by simultaneous measurement of 16O1H/16O, in conjunction with evaluating more traditional indicators of metamictisation. These data demonstrate that whereas some of the heaviest values are anomalous and due to post-crystallisation alteration via incorporation of water into the zircon structure, others record primary values.The data presented here are used to support a previously documented change in tectonic style in the Pilbara Craton at 3.2. Ga, from early crustal growth through magmatic accretion above upwelling, hot mantle, to crustal growth that involved significant amounts of crustal recycling arising from the onset of modern-style plate tectonics (steep subduction of old cold oceanic lithosphere). These results align with global datasets of oxygen isotopes, and point to a more general change in the geodynamics of Earth associated with the secular decrease in heat output of our planet.
KW - Archean
KW - Oxygen isotopes
KW - Pilbara Craton
KW - Subduction
KW - Tectonics
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U2 - 10.1016/j.lithos.2015.04.011
DO - 10.1016/j.lithos.2015.04.011
M3 - Article
AN - SCOPUS:84930227084
SN - 0024-4937
VL - 228-229
SP - 90
EP - 98
JO - Lithos
JF - Lithos
ER -