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Growth of early continental crust by partial melting of eclogite


The tectonic setting in which the first continental crust formed, and the extent to which modern processes of arc magmatism at convergent plate margins were operative on the early Earth, are matters of debate1,2. Geochemical studies have shown that felsic rocks in both Archaean high-grade metamorphic (‘grey gneiss’) and low-grade granite-greenstone terranes are comprised dominantly of sodium-rich granitoids of the tonalite-trondhjemite-granodiorite (TTG) suite of rocks3,4,5,6,7. Here we present direct experimental evidence showing that partial melting of hydrous basalt in the eclogite facies produces granitoid liquids with major- and trace-element compositions equivalent to Archaean TTG, including the low Nb/Ta and high Zr/Sm ratios of ‘average’ Archaean TTG8, but from a source with initially subchondritic Nb/Ta. In modern environments, basalts with low Nb/Ta form by partial melting of subduction-modified depleted mantle9,10, notably in intraoceanic arc settings in the forearc11,12 and back-arc13,14 regimes. These observations suggest that TTG magmatism may have taken place beneath granite-greenstone complexes developing along Archaean intraoceanic island arcs by imbricate thrust-stacking15 and tectonic accretion16 of a diversity of subduction-related terranes. Partial melting accompanying dehydration of these generally basaltic source materials at the base of thickened, ‘arc-like’ crust would produce compositionally appropriate TTG granitoids in equilibrium with eclogite residues.

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Figure 1: Selected trace-element ratios in early–mid-Archaean TTG and late Archaean sanukitoids1–7 match those of experimental liquids in equilibrium with eclogite.
Figure 2: Variations of Th/U versus U in Archaean TTG are also consistent with their equilibration with eclogitic residues.
Figure 3: Niobium/tantalum versus zirconium/samarium ratios suggest a compositionally variable oceanic basaltic source for early–late-Archaean TTG magmas.


  1. 1

    Martin, H. Adakitic magmas: modern analogues of Archean granitoids. Lithos 46, 411–429 (1999)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Smithies, R. H. The Archean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite. Earth Planet. Sci. Lett. 182, 115–125 (2001)

    ADS  Article  Google Scholar 

  3. 3

    Hunter, D. R., Smith, D. G. & Sleigh, D. W. W. Geochemical studies of Archean granitoid rocks in the Southeastern Kaapvaal Province: implications for crustal development. J. Afr. Earth Sci. 15, 127–151 (1992)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Feng, R. & Kerrich, R. Geochemical evolution of granitoids from the Archean Abitibi southern volcanic zone and the Pontiac subprovince, Superior Province, Canada: implications for the tectonic history and source regions. Chem. Geol. 98, 23–70 (1992)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Luais, B. & Hawkesworth, C. J. The generation of continental crust: an integrated study of crust-forming processes in the Archean of Zimbabwe. J. Petrol. 35, 43–93 (1994)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Nutman, A. P., Bennett, V. C., Friend, C. R. L. & Norman, M. D. Meta-igneous (non-gneissic) tonalites and quartz-diorites from an extensive ca. 3800 Ma terrain south of the Isua supracrustal belt, southern West Greenland: constraints on early crust formation. Contrib. Mineral. Petrol. 137, 364–388 (1999)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Kreissig, K., Nagler, T. F., Kramers, J. D., van Reenen, D. D. & Smit, C. A. An isotopic and geochemical study of the northern Kaapvaal Craton and the Southern Marginal Zone of the Limpopo Belt: are they juxtaposed terranes? Lithos 50, 1–25 (2000)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Foley, S., Tiepolo, M. & Vannucci, R. Growth of early continental crust controlled by melting of amphibolite in subduction zones. Nature 417, 637–640 (2002)

    Article  Google Scholar 

  9. 9

    Niu, Y. & Batiza, R. Trace element evidence from seamounts for recycled oceanic crust in the Eastern Pacific mantle. Earth Planet. Sci. Lett. 148, 471–483 (1997)

    ADS  CAS  Article  Google Scholar 

  10. 10

    Weyer, S., Munker, C. & Mezger, K. Nb/Ta Zr/Hf and REEs in the depleted mantle: implications for the differentiation history of the crust-mantle system. Earth Planet. Sci. Lett. 205, 309–324 (2003)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Bedard, J. H. Petrogenesis of boninites from the Betts Cove Ophiolite Newfoundland, Canada: identification of subducted source components. J. Petrol. 40, 1853–1889 (1999)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Cluzel, D., Aitchison, J. C. & Picard, C. Tectonic accretion and underplating of mafic terranes in the Late Eocene intraoceanic forearc of New Caledonia (Southwest Pacific): geodynamic implications. Tectonophysics 340, 23–59 (2001)

    ADS  Article  Google Scholar 

  13. 13

    Munker, C. Nb/Ta fractionation in a Cambrian arc/back arc system. New Zealand: source constraints and application of refined ICPMS techniques. Chem. Geol. 144, 23–45 (1998)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Nicholson, K. N., Picard, C. & Black, P. M. A comparative study of Late Cretaceous ophiolitic basalts from New Zealand and New Caledonia: implications for the tectonic evolution of the SW Pacific. Tectonophysics 327, 157–171 (2000)

    ADS  CAS  Article  Google Scholar 

  15. 15

    de Wit, M. J. On Archean granites, greenstones, cratons, and tectonics: does the evidence demand a verdict? Precambr. Res. 91, 181–226 (1998)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Kusky, T. M. & Polat, A. Growth of granite-greenstone terranes at convergent margins, and stabilization of Archean cratons. Tectonophysics 305, 43–73 (1999)

    ADS  Article  Google Scholar 

  17. 17

    Sen, C. & Dunn, T. Dehydration melting of a basaltic composition amphibolite at 1.5 and 2.0 GPa: implications for the origin of adakites. Contrib. Mineral. Petrol. 117, 394–409 (1994)

    ADS  CAS  Article  Google Scholar 

  18. 18

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

    ADS  CAS  Article  Google Scholar 

  19. 19

    Rapp, R. P., Shimizu, N., Norman, M. D. & Applegate, G. S. Reaction between slab-derived melts and peridotite in the mantle wedge: experimental constraints at 3.8 GPa. Chem. Geol. 160, 335–356 (1999)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Rapp, R. P. Amphibole-out phase boundary in partially melted metabasalt, its control over liquid fraction and composition, and source permeability. J. Geophys. Res. 100, 15601–15610 (1995)

    ADS  CAS  Article  Google Scholar 

  21. 21

    Barth, M. G., Foley, S. F. & Horn, I. Partial melting in Archean subduction zones: constraints from experimentally determined trace element partition coefficients between eclogitic minerals and tonalitic melts under upper mantle conditions. Precambr. Res. 113, 323–340 (2002)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Klein, M., Stosch, H.-G., Seck, H. A. & Shimizu, N. Experimental partitioning of high field strength and rare earth elements between clinopyroxene and garnet in andesitic to tonalitic systems. Geochim. Cosmochim. Acta 64, 99–115 (2000)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Klemme, S., Blundy, J. D. & Wood, B. J. Experimental constraints on major and trace element partitioning during partial melting of eclogite. Geochim. Cosmochim. Acta 66, 3109–3123 (2002)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Boily, M. & Dion, C. Geochemistry of boninite-type volcanic rocks in the Frotet-Evans greenstone belt. Opatica subprovince, Quebec: implications for the evolution of Archean greenstone belts. Precambr. Res. 115, 349–371 (2002)

    ADS  CAS  Article  Google Scholar 

  25. 25

    Green, T. H. Significance of Nb/Ta as an indicator of geochemical processes in the crust-mantle system. Chem. Geol. 120, 347–359 (1995)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Jacob, D. E. & Foley, S. F. Evidence for Archean ocean crust with low high field strength element signature from diamondiferous eclogite xenoliths. Lithos 48, 317–336 (1999)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Barth, M. G. et al. Geochemistry of xenolithic eclogites from West Africa. Part I: A link between low MgO eclogites and Archean crust formation. Geochim. Cosmochim. Acta 65, 1499–1527 (2001)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Rudnick, R. L., Barth, M., Horn, I. & McDonough, W. F. Rutile-bearing refractory eclogites: missing link between continents and depleted mantle. Science 287, 278–281 (2000)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Rollinson, H. Eclogite xenoliths in west African kimberlites as residues from Archean granitoid crust formation. Nature 389, 173–176 (1997)

    ADS  CAS  Article  Google Scholar 

  30. 30

    Horng, W-S. & Hess, P. C. Partition coefficients of Nb and Ta between rutile and anhydrous haplogranite melts. Contrib. Mineral. Petrol. 138, 176–185 (2000)

    ADS  CAS  Article  Google Scholar 

  31. 31

    Polat, A., Hofmann, A. W. & Rosing, M. T. Boninite-like volcanic rocks in the 3.7–3.8 Ga Isua greenstone belt, West Greenland: geochemical evidence for intra-oceanic subduction zone processes in the early Earth. Chem. Geol. 184, 231–254 (2002)

    ADS  CAS  Article  Google Scholar 

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This research was supported by National Science Foundation grants to R.P.R. and the Mineral Physics Institute at Stony Brook. We thank M. Defant for critical comments. Discussions with H. Martin, A. Polat, H. Rollinson, M. Rosing, H. Smithies and M. de Wit helped to improve the manuscript.

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Correspondence to Robert P. Rapp.

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Rapp, R., Shimizu, N. & Norman, M. Growth of early continental crust by partial melting of eclogite. Nature 425, 605–609 (2003).

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