Initiation of plate tectonics from post-magma ocean thermochemical convection

Bradford J. Foley, David Bercovici, Linda Elkins-Tanton

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Leading theories for the presence of plate tectonics on Earth typically appeal to the role of present day conditions in promoting rheological weakening of the lithosphere. However, it is unknown whether the conditions of the early Earth were favorable for plate tectonics, or any form of subduction, and thus, how subduction begins is unclear. Using physical models based on grain-damage, a grainsize-feedback mechanism capable of producing plate-like mantle convection, we demonstrate that subduction was possible on the Hadean Earth (hereafter referred to as proto-subduction or proto-plate tectonics), that proto-subduction differed from modern day plate tectonics, and that it could initiate rapidly. Scaling laws for convection with grain-damage show that though either higher mantle temperatures or higher surface temperatures lead to slower plates, proto-subduction, with plate speeds of ≈1.75 cm/yr, can still be maintained in the Hadean, even with a CO2 rich primordial atmosphere. Furthermore, when the mantle potential temperature is high (e.g., above ≈2000 K), the mode of subduction switches to a "sluggish subduction" style, where downwellings are drip like and plate boundaries are diffuse. Finally, numerical models of post-magma ocean mantle convection demonstrate that proto-plate tectonics likely initiates within ∼100 Myr of magma ocean solidification, consistent with evidence from Hadean zircons. After the initiation of proto-subduction, non-plate-tectonic "sluggish subduction" prevails, giving way to modern style plate tectonics as both the mantle interior and climate cool. Hadean proto-subduction may hasten the onset of modern plate tectonics by drawing excess CO2 out of the atmosphere and cooling the climate.

Original languageEnglish (US)
Pages (from-to)8538-8561
Number of pages24
JournalJournal of Geophysical Research B: Solid Earth
Volume119
Issue number11
DOIs
StatePublished - 2014

Fingerprint

plates (tectonics)
Tectonics
plate tectonics
magma
oceans
convection
subduction
ocean
Hadean
Earth mantle
Earth (planet)
mantle convection
mantle
climate
Convection
Scaling laws
damage
atmospheres
Temperature
early Earth

Keywords

  • damage theory
  • Hadean tectonics
  • magma ocean
  • mantle convection
  • plate tectonics

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Initiation of plate tectonics from post-magma ocean thermochemical convection. / Foley, Bradford J.; Bercovici, David; Elkins-Tanton, Linda.

In: Journal of Geophysical Research B: Solid Earth, Vol. 119, No. 11, 2014, p. 8538-8561.

Research output: Contribution to journalArticle

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abstract = "Leading theories for the presence of plate tectonics on Earth typically appeal to the role of present day conditions in promoting rheological weakening of the lithosphere. However, it is unknown whether the conditions of the early Earth were favorable for plate tectonics, or any form of subduction, and thus, how subduction begins is unclear. Using physical models based on grain-damage, a grainsize-feedback mechanism capable of producing plate-like mantle convection, we demonstrate that subduction was possible on the Hadean Earth (hereafter referred to as proto-subduction or proto-plate tectonics), that proto-subduction differed from modern day plate tectonics, and that it could initiate rapidly. Scaling laws for convection with grain-damage show that though either higher mantle temperatures or higher surface temperatures lead to slower plates, proto-subduction, with plate speeds of ≈1.75 cm/yr, can still be maintained in the Hadean, even with a CO2 rich primordial atmosphere. Furthermore, when the mantle potential temperature is high (e.g., above ≈2000 K), the mode of subduction switches to a {"}sluggish subduction{"} style, where downwellings are drip like and plate boundaries are diffuse. Finally, numerical models of post-magma ocean mantle convection demonstrate that proto-plate tectonics likely initiates within ∼100 Myr of magma ocean solidification, consistent with evidence from Hadean zircons. After the initiation of proto-subduction, non-plate-tectonic {"}sluggish subduction{"} prevails, giving way to modern style plate tectonics as both the mantle interior and climate cool. Hadean proto-subduction may hasten the onset of modern plate tectonics by drawing excess CO2 out of the atmosphere and cooling the climate.",
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