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Geodynamic constraints on early Earth crust formation and tectonics

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If you have a question about this talk, please contact Adriano Gualandi.

A unique feature of the Earth compared to the other rocky planets of our solar system is the operation of plate tectonics at the present day. However, how and when Earth developed into this present-day state is unclear. Key to deciphering Earth’s long-term tectonic evolution is the growth of the first continents, as these represent the oldest extant rock record providing our best window into the geodynamic processes of the very early Earth. Early continental crust has been proposed to form by a variety of mechanisms, some involving plate tectonics and some not. End-member models of early continental crust formation include melting hydrated mafic rocks at the base of a thick, volcanically active oceanic crustal plateau, a process not requiring plate tectonics, and melting of mafic crust during subduction, a process compatible with plate tectonics. I use numerical models of early Earth mantle convection and crust formation, combined with key geochemical observations, to provide new constraints on these models. I show that continental crust formation by slab melting during subduction can only occur when subduction is sluggish and present a new mechanism for such subduction on the early Earth. I further show how continent formation by ocean plateau melting and by slab melting can combine to explain observations from the Archean geologic record, with implications for Earth’s long-term tectonic evolution.

This talk is part of the Bullard Laboratories Wednesday Seminars series.

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