Continental crust formation on early Earth controlled by intrusive magmatism

• Published in: Nature (London) Vol. 545; no. 7654; pp. 332 - 335
• Main Authors: Rozel, A. B., Golabek, G. J., Jain, C., Tackley, P. J., Gerya, T.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18-05-2017; Nature Publishing Group
• Subjects: 704/2151/209; 704/2151/210; 704/2151/431; 704/445/210; Asthenosphere; Brittleness; Classification; Continental crust; Continents; Convection; Convection models; Corona; Crust (Geology); Delamination; Earth; Earth mantle; Evolution; Geochemistry; Geodynamics; Geology; Geophysics; Heat; Heat loss; Heat transfer; Humanities and Social Sciences; Hypotheses; Instability; letter; Lithosphere; Magma; Magmatism; Mantle (Geology); Mapping; Mathematical models; Melts; multidisciplinary; Natural history; Numerical models; Numerical simulations; Oceans; Plate tectonics; Pressure; Probes; Radar; Recycling; Robustness (mathematics); Rocks; Science; Tectonics; Temperature effects; Temperature profiles; Three dimensional models; Topography; Two dimensional models; Upwelling
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature22042

Modelling of two modes of continental crust formation suggests that before plate tectonics began operating, the Archean early Earth’s tectonic regime was governed by intrusive magmatism.
Earth's primordial squishy lid
The global geodynamic regime of early Earth, which was in operation before the onset of plate tectonics during the Archaean eon over 2.5 billion years ago, remains contentious. Antoine Rozel
et al.
use numerical models of global thermochemical convection, including magmatic processes, to show that a tectonics regime dominated by intrusive molten rock results in warm crustal geotherms and can reproduce the observed proportions of primordial continental crust. They therefore conclude that the early Archaean Earth operated globally in a 'Plutonic squishy lid' regime in which intrusions of magma solidified into igneous rock deep below Earth's surface, rather than in an ‘Io-like’ regime dominated by extrusive volcanism.
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
1
,
2
and more intense juvenile magmatism than in the present-day Earth
3
,
4
, two crust–mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism
5
,
6
and the “Plutonic squishy lid” tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus
7
,
8
,
9
. Both tectonics regimes are capable of producing primordial tonalite–trondhjemite–granodiorite (TTG) continental crust
5
,
10
but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly
9
,
10
, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data
11
. 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
12
leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data
4
,
11
(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.