Authors / CoAuthors
Smithies, R.H. | Champion, D.C. | Van Kranendonk, M.J.
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 MORBsource 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.
Product Type
nonGeographicDataset
eCat Id
68748
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- External PublicationScientific Journal Paper
- ( Theme )
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- geochemistry
- ( Theme )
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- isotopes
- ( Theme )
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- geodynamics
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- AU-WA
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2009-01-01T00:00:00
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geoscientificInformation
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[-22.5, -20.0, 116.0, 121.0]
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