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Progressive mixing of meteoritic veneer into the early Earth’s deep mantle


Komatiites are ancient volcanic rocks, mostly over 2.7 billion years old (from the Archaean era), that formed through high degrees of partial melting of the mantle and therefore provide reliable information on bulk mantle compositions1. In particular, the platinum group element (PGE) contents of komatiites provide a unique source of information on core formation, mantle differentiation and possibly core–mantle interaction2,3,4,5,6,7,8. Most of the available PGE data on komatiites are from late Archaean (2.7–2.9 Gyr old) or early Proterozoic (2.0–2.5 Gyr old) samples. Here we show that most early Archaean (3.5–3.2 Gyr old) komatiites from the Barberton greenstone belt of South Africa and the Pilbara craton of Western Australia are depleted in PGE relative to late Archaean and younger komatiites. Early Archaean komatiites record a signal of PGE depletion in the lower mantle, resulting from core formation. This signal diminishes with time owing to progressive mixing-in to the deep mantle of PGE-enriched cosmic material that the Earth accreted as the ‘late veneer’ during the Early Archaean (4.5–3.8 Gyr ago) meteorite bombardment.

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Figure 1: PGE contents in Pilbara and Barberton komatiites.
Figure 2: Diagram of Pt and Ru versus age of komatiites.

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  1. Campbell, I. H. & Griffiths, R. W. The changing nature of mantle hotspots through time: implications for the chemical evolution of the mantle. J. Geol. 92, 497–523 (1992)

    Article  ADS  Google Scholar 

  2. Barnes, S.-J., Naldrett, A. J. & Gorton, M. P. The origin of the fractionation of the platinum-group elements in terrestrial magmas. Chem. Geol. 53, 303–325 (1985)

    Article  CAS  ADS  Google Scholar 

  3. Brügmann, G. E., Arndt, N. T. & Hofmann, A. W. Platinum-group element abundances in komatiitic basalts and komatiites. Terra Cognita 5, 288–289 (1985)

    Google Scholar 

  4. Rehkamper, M. et al. Ir, Ru, Pt, and Pd in basalts and komatiites: new constraints for the geochemical behavior of the platinum-group elements in the mantle. Geochim. Cosmochim. Acta 63, 3915–3934 (1999)

    Article  CAS  ADS  Google Scholar 

  5. Puchtel, I. S., Brandon, A. D. & Humayun, M. Precise Pt-Re-Os isotope systematics of the mantle from 2.7-Ga komatiites. Earth Planet. Sci. Lett. 224, 157–174 (2004)

    Article  CAS  ADS  Google Scholar 

  6. Puchtel, I. S., Walker, R. J., Anhaeusser, C. R. & Gruau, G. Re-Os systematics and HSE abundances of the 3.5 Ga Schapenburg komatiites, South Africa: hydrous melting or prolonged survival of primordial heterogeneities in the mantle? Chem. Geol. 10.1016/j.chemgeo.2009.02.006 (2009)

  7. Hanski, E., Huhma, H., Rastas, P. & Kamenetsky, V. S. The Palaeoproterozoic komatiite-picrite association of Finnish Lapland. J. Petrol. 42, 855–876 (2001)

    Article  CAS  ADS  Google Scholar 

  8. Barnes, S. J. & Fiorentini, M. L. Iridium, ruthenium and rhodium in komatiites: Evidence for iridium alloy saturation. Chem. Geol. 257, 44–58 (2008)

    Article  CAS  ADS  Google Scholar 

  9. Arndt, N. T., Lesher, C. M. & Barnes, S. J. Komatiite (Cambridge Univ. Press, 2008)

    Book  Google Scholar 

  10. Becker, H. et al. Highly siderophile element composition of the Earth’s primitive mantle: constraints from new data on peridotite massifs and xenoliths. Geochim. Cosmochim. Acta 70, 4528–4550 (2006)

    Article  CAS  ADS  Google Scholar 

  11. Keays, R. R. in Gold '82—The Geology, Geochemistry and Genesis of Gold Deposits (ed. Foster, R. P.) 17–51 (Balkema, 1983)

    Google Scholar 

  12. Maier, W. D., Roelofse, F. & Barnes, S.-J. The concentration of the platinum-group elements in South African komatiites; implications for mantle sources, melting regime and PGE fractionation during crystallization. J. Petrol. 44, 1787–1804 (2003)

    Article  CAS  ADS  Google Scholar 

  13. Bennett, V. C., Nutman, A. P. & Esat, T. M. Constraints on mantle evolution from Os-187/Os-188 isotopic compositions of Archean ultramafic rocks from southern West Greenland (3.8 Ga) and Western Australia (3.46 Ga). Geochim. Cosmochim. Acta 66, 2615–2630 (2002)

    Article  CAS  ADS  Google Scholar 

  14. Lowe, D. R. in Geologic Evolution of the Barberton Greenstone Belt, South Africa (eds Lowe, D. R. & Byerly, G. R.) 287–312 (Geological Society of America Special Paper 329, 1999)

    Google Scholar 

  15. Van Kranendonk, M. J., Kröner, A., Hegner, E. & Connelly, J. Age, lithology and structural evolution of the c. 3.53 Ga Theespruit Formation in the Tjakastad area, southwestern Barberton Greenstone Belt, South Africa, with implications for Archean tectonics. Chem. Geol. 261, 115–139 (2009)

    Article  ADS  Google Scholar 

  16. Van Kranendonk, M. J., Smithies, R. H., Hickman, A. H. & Champion, D. C. in Earth’s Oldest Rocks: Developments in Precambrian Geology (eds Van Kranendonk, M. J., Smithies, R. H. & Bennett, V.C.) 303–357 (Elsevier, 2007)

    Google Scholar 

  17. Lesher, C. M., Burnham, O. M., Keays, R. R., Barnes, S. J. & Hulbert, L. Geochemical discrimination of barren and mineralized komatiites asssociated with magmatic Ni-Cu-(PGE) sulphide deposits. Can. Mineral. 39, 673–696 (2001)

    Article  CAS  Google Scholar 

  18. Mavrogenes, J. A. & O'Neill, H. S. C. The relative effects of pressure, temperature and oxygen fugacity on the solubility of sulfide in mafic magmas. Geochim. Cosmochim. Acta 63, 1173–1180 (1999)

    Article  CAS  ADS  Google Scholar 

  19. Sobolev, A. V. et al. The amount of recycled crust in sources of mantle-derived melts. Science 316, 412–417 (2007)

    Article  CAS  ADS  Google Scholar 

  20. Blichert-Toft, J. & Arndt, N. T. Hf isotope compositions of komatiites. Earth Planet. Sci. Lett. 171, 439–451 (1999)

    Article  CAS  ADS  Google Scholar 

  21. McDonald, L. & Viljoen, K. S. Platinum group element geochemistry of mantle eclogites; a reconnaissance study of xenoliths from the Orapa Kimberlite, Botswana. Trans. Inst. Mining Metallurgy 115, 81–93 (2006)

    CAS  Google Scholar 

  22. Grove, T. L., de Wit, M. J. & Dann, J. in Greenstone Belts (eds de Wit, M. J. & Ashwal, L. D.) 422–437 (Oxford Science Publications, 1997)

    Google Scholar 

  23. McCulloch, M. T. & Bennett, V. C. Progressive growth of the Earth's continental crust and depleted mantle: geochemical constraints. Geochim. Cosmochim. Acta 58, 4717–4738 (1994)

    Article  CAS  ADS  Google Scholar 

  24. Chase, C. G. & Patchett, P. J. Stored mafic/ultramafic crust and early Archaean mantle depletion. Earth Planet. Sci. Lett. 91, 66–72 (1988)

    Article  CAS  ADS  Google Scholar 

  25. Campbell, I. H. & Allen, C. M. Formation of supercontinents linked to increases in atmospheric oxygen. Nature Geosci. 1, 554–558 (2008)

    Article  CAS  ADS  Google Scholar 

  26. Chou, C. L. Fractionation of siderophile elements in the Earth’s upper mantle. Proc. 9th Lunar Planet. Sci. Conf. 9, 219–230 (1978)

    ADS  Google Scholar 

  27. O'Neill, H. S. C. et al. Experimental petrochemistry of some highly siderophile elements at high temperatures, and some implications for core formation and the mantle's early history. Chem. Geol. 120, 255–273 (1995)

    Article  CAS  ADS  Google Scholar 

  28. Puchtel, I. S. et al. Platinum group element geochemistry of komatiites from the Alexo and Pyke Hill areas, Ontario, Canada. Geochim. Cosmochim. Acta 68, 1361–1383 (2004)

    Article  CAS  ADS  Google Scholar 

  29. Smithies, R. H. & Champion, D. C. The Archaean high-Mg diorite suite: links to tonalite-trondhjemite-granodiorite magmatism and implications for early Archaean crustal growth. J. Petrol. 41, 1653–1671 (2000)

    Article  CAS  ADS  Google Scholar 

  30. Richardson, T. & Burnham, O. M. Summary of Field Work and Other Activities 2002. Precious Metal Analysis at the Geoscience Laboratories: Results from the New Low-Level Analytical Facility. Open File Report 35–1-35–535 (Ontario Geological Survey, 2002)

    Google Scholar 

  31. Lorand, J.-P. et al. Abundance and distribution of platinum-group elements in orogenic lherzolites; a case study in a Fontete Rouge lherzolite (French Pyrénées). Chem. Geol. 248, 174–194 (2008)

    Article  CAS  ADS  Google Scholar 

  32. Frimpong, A. et al. Recovery of precious metals using nickel fire assay collection—problems at nanogram per gram concentrations. Analyst 120, 1675–1680 (1995)

    Article  CAS  ADS  Google Scholar 

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We thank D. Savard for the PGE analysis, and E. Hanski for comments. We also thank N. Arndt and H. Becker for reviews. This study was partly funded by the ARC (to M.L.F.), the University of Western Australia (to W.D.M.), CSIRO (to S.J.B.) and NSERC (to S.-J.B.). P.P. acknowledges support from the Geological Survey of Finland (GTK).

Author Contributions W.D.M., S.J.B., M.L.F., P.P. and R.H.S. provided samples and data, S.-J.B. analysed the South African and Pilbara samples, the first four authors provided the interpretation, and all co-authors contributed in the form of discussion and critical comment.

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Correspondence to Wolfgang D. Maier.

Supplementary information

Supplementary Information

This file contains Supplementary Methods, Supplementary Figures 3 - 4 with Legends and Supplementary References. (PDF 2187 kb)

Supplementary Table 1

This file contains the whole rock data of the Barberton samples. (XLS 59 kb)

Supplementary Table 2

This file contains the whole rock data of the Pilbara samples. (XLS 27 kb)

Supplementary Table 3

This file contains the analytical accuracy and precision. (XLS 16 kb)

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Maier, W., Barnes, S., Campbell, I. et al. Progressive mixing of meteoritic veneer into the early Earth’s deep mantle. Nature 460, 620–623 (2009).

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