High field strength element ratios in Archean basalts

A window to evolving sources of mantle plumes?

Kent C. Condie*

*Corresponding author for this work

Research output: Contribution to journalArticle

403 Citations (Scopus)

Abstract

In terms of high field strength element ratios Nb/Th, Zr/Nb, Nb/Y and Zr/Y, most basalts from non-arc type Archean greenstones are similar to oceanic plateau basalts, suggestive of mantle plume sources. A large number of these basalts have ratios similar to primitive mantle composition. Perhaps the Archean mantle was less fractionated than at present and "primitive mantle" comprised much of the deep mantle and made a significant contribution to mantle plumes. The near absence of Archean greenstone basalts similar to NMORB in composition is also consistent with a relatively unfractionated mantle in which a shallow depleted source (DM) was volumetrically insignificant. The element ratios in basalts also indicate the existence of recycled components (HIMU, EM1, EM2) in the mantle by the Late Archean. This suggests that oceanic lithosphere was recycled into the deep mantle and became incorporated in some mantle plumes by the Late Archean. High field strength element ratios also indicate an important contribution of continental crust or/and subcontinental lithosphere to some non-arc Archean greenstone basalts. This implies that at least thin continental lithosphere was relatively widespread in the Archean.

Original languageEnglish
Pages (from-to)491-504
Number of pages14
JournalLithos
Volume79
Issue number3-4 SPEC. ISS.
DOIs
Publication statusPublished - Feb 2005
Externally publishedYes

Keywords

  • Archean basalts
  • High field strength element ratios
  • Mantle plumes

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