Letter | Published:

Earth’s first stable continents did not form by subduction

Nature volume 543, pages 239242 (09 March 2017) | Download Citation

  • A Corrigendum to this article was published on 10 May 2017


The geodynamic environment in which Earth’s first continents formed and were stabilized remains controversial1. Most exposed continental crust that can be dated back to the Archaean eon (4 billion to 2.5 billion years ago) comprises tonalite–trondhjemite–granodiorite rocks (TTGs) that were formed through partial melting of hydrated low-magnesium basaltic rocks2; notably, these TTGs have ‘arc-like’ signatures of trace elements and thus resemble the continental crust produced in modern subduction settings3. In the East Pilbara Terrane, Western Australia, low-magnesium basalts of the Coucal Formation at the base of the Pilbara Supergroup have trace-element compositions that are consistent with these being source rocks for TTGs. These basalts may be the remnants of a thick (more than 35 kilometres thick), ancient (more than 3.5 billion years old) basaltic crust4,5 that is predicted to have existed if Archaean mantle temperatures were much hotter than today’s6,7,8. Here, using phase equilibria modelling of the Coucal basalts, we confirm their suitability as TTG ‘parents’, and suggest that TTGs were produced by around 20 per cent to 30 per cent melting of the Coucal basalts along high geothermal gradients (of more than 700 degrees Celsius per gigapascal). We also analyse the trace-element composition of the Coucal basalts, and propose that these rocks were themselves derived from an earlier generation of high-magnesium basaltic rocks, suggesting that the arc-like signature in Archaean TTGs was inherited from an ancestral source lineage. This protracted, multistage process for the production and stabilization of the first continents—coupled with the high geothermal gradients—is incompatible with modern-style plate tectonics, and favours instead the formation of TTGs near the base of thick, plateau-like basaltic crust9. Thus subduction was not required to produce TTGs in the early Archaean eon.

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  1. 1.

    & When Did Plate Tectonics Begin On Planet Earth? 7th edn (Geol. Soc. Am., 2008)

  2. 2.

    , , & Delamination and recycling of Archaean crust caused by gravitational instabilities. Nat. Geosci. 7, 47–52 (2013)

  3. 3.

    , & Growth of early continental crust by partial melting of eclogite. Nature 425, 605–609 (2003)

  4. 4.

    , & Formation of Paleoarchean continental crust through infracrustal melting of enriched basalt. Earth Planet. Sci. Lett. 281, 298–306 (2009)

  5. 5.

    & Middle Archean continent formation by crustal delamination. Geology 29, 1083–1086 (2001)

  6. 6.

    , & Thermal history of the Earth and its petrological expression. Earth Planet. Sci. Lett. 292, 79–88 (2010)

  7. 7.

    & Formation of cratonic lithosphere: an integrated thermal and petrological model. Lithos 149, 4–15 (2012)

  8. 8.

    Urey ratio and the structure and evolution of Earth’s mantle. Rev. Geophys. 46, RG2007 (2008)

  9. 9.

    , , & Generation of felsic crust in the Archean: a geodynamic modeling perspective. Precambr. Res. 271, 198–224 (2015)

  10. 10.

    The composite Archaean grey gneisses: petrological significance, and evidence for a non-unique tectonic setting for Archaean crustal growth. Lithos 123, 21–36 (2011)

  11. 11.

    & Dehydration melting of metabasalt at 8–32 kbar: implications for continental growth and crust-mantle recycling. J. Petrol. 36, 891–931 (1995)

  12. 12.

    , & Growth of early continental crust controlled by melting of amphibolite in subduction zones. Nature 417, 837–840 (2002)

  13. 13.

    The Archean grey gneisses and the genesis of continental crust. Dev. Precamb. Geol. 11, 205–259 (1994)

  14. 14.

    The Archaean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite. Earth Planet. Sci. Lett. 182, 115–125 (2000)

  15. 15.

    A catalytic delamination-driven model for coupled genesis of Archaean crust and sub-continental lithospheric mantle. Geochim. Cosmochim. Acta 70, 1188–1214 (2006)

  16. 16.

    , , & Continental geochemical signatures in dacites from Iceland and implications for models of early Archaean crust formation. Earth Planet. Sci. Lett. 279, 44–52 (2009)

  17. 17.

    & in Archean Geodynamics and Environments (eds , & ) 149–175 (Am. Geophys. Union, 2006)

  18. 18.

    & Secular changes in tonalite-trondhjemite-granodiorite composition as markers of the progressive cooling of Earth. Geology 30, 319–322 (2002)

  19. 19.

    et al. Activity-composition relations for the calculation of partial melting equilibria in metabasic rocks. J. Metamorph. Geol. 34, 845–869 (2016)

  20. 20.

    , , & Geology and tectonic evolution of the Archean North Pilbara Terrain, Pilbara Craton, Western Australia. Econ. Geol. 97, 695–732 (2002)

  21. 21.

    et al. Making it thick: a volcanic plateau origin of Palaeoarchean continental lithosphere of the Pilbara and Kaapvaal cratons. Geol. Soc. Spec. Publ. 389, 83–111 (2015)

  22. 22.

    , , & Trace element systematics of Mg-, to Fe-tholeiitic basalt suites of the Superior Province: implications for Archean mantle reservoirs and greenstone belt genesis. Lithos 46, 163–187 (1999)

  23. 23.

    Incompatible element ratios in oceanic basalts and komatiites: tracking deep mantle sources and continental growth rates with time. Geochem. Geophys. Geosyst. 4, 1–28 (2003)

  24. 24.

    et al. Oxidation state of iron in komatiitic melt inclusions indicates hot Archaean mantle. Nature 455, 960–963 (2008)

  25. 25.

    The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics. Geosci. Frontiers 5, 553–569 (2014)

  26. 26.

    et al. Partitioning of Nb and Ta between rutile and felsic melt and the fractionation of Nb/Ta during partial melting of hydrous metabasalt. Geochim. Cosmochim. Acta 75, 1673–1692 (2011)

  27. 27.

    & Partial melt distributions from inversion of rare earth element concentrations. J. Petrol. 32, 1021–1091 (1991)

  28. 28.

    & Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. Geol. Soc. Spec. Publ. 42, 313–345 (1989)

  29. 29.

    & An internally consistent dataset with uncertainties and correlations: 3. Applications to geobarometry, worked examples and a computer program. J. Metamorph. Geol. 6, 173–204 (1988)

  30. 30.

    & An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids. J. Metamorph. Geol. 29, 333–383 (2011)

  31. 31.

    , , , & New mineral activity-composition relations for thermodynamic calculations in metapelitic systems. J. Metamorph. Geol. 32, 261–286 (2014)

  32. 32.

    , & The interpretation of reaction textures in Fe-rich metapelitic granulites of the Musgrave Block, Central Australia: constraints from mineral equilibria calculations in the system. J. Metamorph. Geol. 20, 41–55 (2002)

  33. 33.

    , , & The effect of TiO2 and Fe2O3 on metapelitic assemblages at greenschist and amphibolite facies conditions: mineral equilibria calculations in the system K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3. J. Metamorph. Geol. 18, 497–511 (2000)

  34. 34.

    & Activity–composition relations for phases in petrological calculations: an asymmetric multicomponent formulation. Contrib. Mineral. Petrol. 145, 492–501 (2003)

  35. 35.

    , , , & Zircon saturation re-revisited. Chem. Geol. 351, 324–334 (2013)

  36. 36.

    & Trace-element partition coefficients for ilmenite, orthopyroxene and pyrrhotite in rhyolite determined by micro-PIXE analysis. Chem. Geol. 117, 313–330 (1994)

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We acknowledge financial support from The Institute of Geoscience Research (TIGeR) at Curtin University. R.H.S. publishes with the permission of the Executive Director, Geological Survey of Western Australia.

Author information


  1. Department of Applied Geology, The Institute for Geoscience Research (TIGeR), Centre for Exploration Targeting – Curtin node, Australian Research Council Centre of Excellence for Core to Crust Fluid Systems, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia

    • Tim E. Johnson
    • , Nicholas J. Gardiner
    •  & Christopher L. Kirkland
  2. Laboratory for Crustal Petrology, Department of Geology, University of Maryland, College Park, Maryland 20742-4211, USA

    • Michael Brown
  3. Geological Survey of Western Australia, 100 Plain Street, East Perth, Western Australia 6004, Australia

    • R. Hugh Smithies


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T.E.J. conceived the project and performed the phase equilibria calculations. N.J.G. undertook the trace-element modelling. All authors analysed the data and contributed to writing the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Tim E. Johnson.

Reviewer Information Nature thanks J. Bédard, R. Rapp and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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