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SUMMARY:Geodynamic constraints on early Earth crust formation and tectonic
 s - Brad Foley -- Penn State University
DTSTART:20240605T130000Z
DTEND:20240605T140000Z
UID:TALK216454@talks.cam.ac.uk
CONTACT:Adriano Gualandi
DESCRIPTION:A unique feature of the Earth compared to the other rocky plan
 ets 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 i
 s unclear. Key to deciphering Earth’s long-term tectonic evolution is th
 e growth of the first continents\, as these represent the oldest extant ro
 ck record providing our best window into the geodynamic processes of the v
 ery early Earth. Early continental crust has been proposed to form by a va
 riety of mechanisms\, some involving plate tectonics and some not. End-mem
 ber models of early continental crust formation include melting hydrated m
 afic rocks at the base of a thick\, volcanically active oceanic crustal pl
 ateau\, a process not requiring plate tectonics\, and melting of mafic cru
 st during subduction\, a process compatible with plate tectonics. I use nu
 merical models of early Earth mantle convection and crust formation\, comb
 ined with key geochemical observations\, to provide new constraints on the
 se models. I show that continental crust formation by slab melting during 
 subduction can only occur when subduction is sluggish and present a new me
 chanism for such subduction on the early Earth. I further show how contine
 nt formation by ocean plateau melting and by slab melting can combine to e
 xplain observations from the Archean geologic record\, with implications f
 or Earth's long-term tectonic evolution. 
LOCATION:Wolfson Lecture Theatre
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