patrick boyd peter reiners, ph.d. & stuart thomson, ph.d. department of geosciences, university...
TRANSCRIPT
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U-PB GEOCHRONOMETRY AND (U-TH)/HE THERMOCHRONOMETRY OF THE WINDMILL
ISLANDS, EAST ANTARCTICA
Patrick BoydPeter Reiners, Ph.D. & Stuart Thomson, Ph.D.
Department of Geosciences, University of Arizona
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The Windmill Islands
Fretwell et al. (2013)
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Zhang, 2012
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Antarctica.gov
Windmill Islands, Wilkes Land, Antarctica
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What do we want to know?
Timing of metamorphic and magmatic events?
Timing of low temperature heating and cooling?
Can supercontinent formation/breakup be seen in U-Pb or (U-Th)/He ages?
Can Eocene glaciation be seen in (U-Th)/He ages?
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Process
Mineral separation on 8 different samples
17 apatite (U-Th)/He ages (From 4 samples)
19 zircon (U-Th)/He ages (From 4 samples)
5 zircon U-Pb ages
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Methods
Apatite + Zircon (U-Th)/He (Low temperature history, often shows timing of erosion)
-Apatite closure temperature is 60-80° C
-Zircon closure temperature is 160-180° C Zircon U-Pb (Crystallization and
metamorphism timing)-900-1000° C closure temperature
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U-Pb Results
1.167 Billion Years
1.18 Billion Years
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U-Pb Results
1.308 Billion Years
1.379 Billion Years
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U-Pb Results
504 Million Years
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(U-Th)/He Apatite Results
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(U-Th)/He Zircon Results
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(U-Th)/He Thermal Modeling of Zircon and Apatite from sample PRR_27946, Holl Island
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Conclusions
Grenville aged metamorphism
500 Ma Pan-African magmatism
300 Ma Permian cooling similar to ages acquired in SW Australia
75 Ma slight heating event
No trace of Eocene glacial erosion
Varying thermal histories based on sample location
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Acknowledgements
Dr. Peter ReinersDr. Stuart ThomsonArizona Space Grant ConsortiumArizona Radiogenic Helium Dating LaboratoryArizona Laserchron Center