Formation of Paleoarchean continental crust through infracrustal melting of enriched basalt

R. H. Smithies, D. C. Champion, M. J. Van Kranendonk

Research output: Contribution to journalArticle

150 Citations (Scopus)

Abstract

Paleoarchean rocks of the tonalite-trondhjemite-granodiorite (TTG) series require a basaltic source region more enriched in K, LILE, Th and LREE than the low-K tholeiites typical of Archean supracrustal sequences. Most TTG of the Pilbara Craton, in northwestern Australia, formed between 3.5 and 3.42 Ga through infracrustal melting of a source older than 3.5 Ga. Basaltic to andesitic rocks of the 3.51 Ga Coucal Formation, at the base of the Pilbara Supergroup, are amongst the only well-preserved remnants of pre-3.5 Ga supracrustal material on Earth, and may have formed a large proportion of pre-3.5 Ga Pilbara crust. These rocks are significantly enriched in K, LILE, Th and LREE compared to post-3.5 Ga Paleoarchean basalts and andesites, and form a compositionally suitable source for TTG. Enrichment in these basalts was not the result of crustal assimilation but was inherited from a mantle source that was less depleted than modern MORB-source and was enriched in recycled crustal components. We suggest that the formation of Paleoarchean TTG and of their voluminous mafic source regions reflects both a primitive stage in the thermal and compositional evolution of the mantle and a significant prehistory of crustal recycling. Crown

Original languageEnglish
Pages (from-to)298-306
Number of pages9
JournalEarth and Planetary Science Letters
Volume281
Issue number3-4
DOIs
Publication statusPublished - May 15 2009
Externally publishedYes

Keywords

  • Paleoarchean
  • crustal evolution
  • enriched basalt
  • infracrustal melting
  • source regions
  • tonalite-trondhjemite-granodiorite (TTG)

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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