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Description
Currently, there is little evidence concerning the extent or composition of the Earth’s crust from the time of
formation ca. 4.56 billion years ago (Ga) to the end of the meteoritic Late Heavy Bombardment that affected all
rocky planets at ca. 3.8 Ga on Earth from 4.5 to 4.0 Ga (the Hadean), where no rock record remains, rare
crystals of zircon provide minute time capsules of what our planet’s crust was like. Between 4.0 and 3.6 Ga, a
partial rock record is preserved in just a few terranes on Earth, and geochemical and isotopic relationships
between these rocks and their zircon endowment allow us to extrapolate back to the composition and extent of
the earliest crust. However, the full picture of zircon-host rock relationships in the early Earth is incomplete.
This is because most of these terranes remain under-investigated, especially those in the polar and subpolar
regions of Canada and Antarctica, where there is the greatest potential for discoveries of new areas of
Eoarchean crust. Through a combination of expedition work together with geochemical and geochronological
investigations, the PAAN project will deliver breakthrough science by unlocking significant new information
about Earth’s early history, especially with respect to the formation and evolution of continental crust. To
achieve this goal zircon in samples from polar and sub-polar regions (namely Antarctica, Greenland and
Labrador) will be used in combination with geochemistry and field work. Integration of these avenues of
investigation will be used to compare the geological histories of these regions in order to find ‘missing links’
between them. The overarching goal will be to test the hypothesis that by 3.6 Ga these disparate relics of
Eoarchean crust were part of the same ‘first supercontinent’.