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The ongoing search for Hadean crust on Earth
A progress report on collaborative research ongoing between Tony Kemp (UWA ARC Future Fellow), GSWA, Simon Wilde (Curtin University), Vickie Bennett (ANU), Jeff Vervoort (Washington State University) and Martin Whitehouse (Stockholm University).
The familiar concentric layer cake structure of the Earth depicted in textbooks formed within a few hundred million years of the accretion of the planet. This is when the metallic core segregated, the oceans condensed, the atmosphere outgassed and the first rocky crust formed. Remarkably, the isotope legacy of this initial crustal separation still endures in the continents today. Attempts at a more complete understanding of how and exactly when these planetary differentiation processes occurred, are, however, confounded by the apparent absence of a rock record of the earliest part of Earth evolution. This mysterious geological dark age, extending from the established age of the Earth's formation at ~ 4.5 Ga to the oldest preserved rocks known at ~ 4.0 Ga (the Acasta Gneisses in northwestern Canada), is commonly referred to as the Hadean Eon. A host of questions about this critical formative period remain unanswered. How much crustal material existed on the Hadean Earth? What was its composition and under what geodynamic conditions did it form? Further progress on these fundamental issues would be greatly expedited by the discovery of actual Hadean rocks.