Continental crust formation on early Earth controlled by intrusive magmatism

Abstract

The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the "Plutonic squishy lid" tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

Generation of Earth's Early Continents From a Relatively Cool Archean Mantle

“…The most abundant category is represented by the MP TTGs, 60% of all TTGs analyzed, while the other two represent 20% of the total TTGs analyzed (Moyen, ). The relative amount of these three type of TTGs have been widely used in geodynamical modeling to assess the proper condition of the TTGs generation (Fischer & Gerya, ; Rozel et al, ). Yet the validity of this classification has been recently questioned using thermodynamic modeling (Palin et al, ), which demonstrate that the three types can be generated by prograde metamorphic paths over a much narrower pressure window.…”

Plutonic‐Squishy Lid: A New Global Tectonic Regime Generated by Intrusive Magmatism on Earth‐Like Planets

“…These features lead to high surface heat flux, which is thought to be the case in the Archean (Lenardic, ). The plutonic‐squishy‐lid regime also exhibits the components needed to the formation of continental crust, that is, delamination of the lower eclogitic part of an oceanic protocrust, which would lead to the production of tonalite, trondhjemite, and granodiorite suites (Jain et al, ; Rozel et al, ) as recorded in Archean cratons (Martin, ; Moyen & Martin, ; Johnson et al, ; Zegers & van Keken, ). Due to these reasons, the plutonic‐squishy‐lid regime seems to be a prime candidate to have been active during the Archean Earth, and future work should investigate this possibility further.…”

Lateral Mixing Processes in the Hadean

“…This is a similar result for many subduction models, which showed coherent slab subduction failing under hotter thermal conditions (e.g., Moyen & van Hunen, ; Sizova et al, ; van Thienen et al, ,). However, alternative regimes involving very slow subduction with a damage rheology (Foley & Rizo, ), dominantly heat pipe extrusive volcanism (Moore & Webb, ), or volcanic/magmatic emplacement with limited wholesale tectonism, but some intraplate deformation (plutonic squishy lid, Rozel et al, ) may conceivably give rise to similar mixing timescales, provided limited lid recycling—and mixing alone cannot resolve between these related dynamic possibilities.…”