Upper mantle pollution during Afar plume-continental rift interaction

Tyrone O. Rooney, Barry B. Hanan, David W. Graham, Tanya Furman, Janne Blichert-toft, Jean Guy Schilling

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

New Pb, Sr, Nd, Hf, and He isotope data for Quaternary basalts, erupted from Debre Zeyit, Butajira, and the Wonji Fault Belt of the Main Ethiopian Rift, show systematic mixing relationships involving three distinct mantle sources. The Pb, Sr, Nd, and Hf isotopic arrays converge in a specific region of isotopic multi-space where they define the composition of the Afar mantle plume (centered about 206Pb/ 204Pb = 19·5, 87Sr/ 86Sr = 0·7035, ε Nd = +4·6, ε Hf = +9·3,. 3He/ 4He > 15 R A). This plume end-member has an identical composition to that observed previously in oceanic basalts. The distinct isotopic arrays for the various volcanic areas in the Main Ethiopian Rift vary spatially in a systematic manner, and may be viewed as pseudo-binary mixing arrays. This further suggests that the Afar mantle plume interacts with the local continental lithosphere and upper mantle asthenosphere (mid-ocean ridge basalt-like source) through an ordered sequence of mixing events. Simple mixing models require that the mass proportions of continental lithosphere and upper mantle involved in magma generation must be nearly constant within each volcanic area, but that the proportion of plume material decreases regularly with distance southwestward along the Main Ethiopian Rift, away from the central axis of the plume. This systematic behavior means that continental lithosphere can become detached and mixed into the shallow mantle prior to the flow of upwelling plume material beneath the developing rift system. Detachment and mixing into the asthenosphere during continental rift evolution is an important process for producing the range of ambient upper mantle compositions sampled by mid-ocean ridge volcanism away from island hotspots.

Original languageEnglish (US)
Article numberegr065
Pages (from-to)365-389
Number of pages25
JournalJournal of Petrology
Volume53
Issue number2
DOIs
StatePublished - Feb 1 2012

Fingerprint

pollution
plumes
upper mantle
Earth mantle
Pollution
plume
continental lithosphere
mantle plume
lithosphere
asthenosphere
basalt
interactions
mid-ocean ridges
Chemical analysis
volcanology
proportion
mid-ocean ridge
mid-ocean ridge basalt
mantle source
Isotopes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

Rooney, T. O., Hanan, B. B., Graham, D. W., Furman, T., Blichert-toft, J., & Schilling, J. G. (2012). Upper mantle pollution during Afar plume-continental rift interaction. Journal of Petrology, 53(2), 365-389. [egr065]. https://doi.org/10.1093/petrology/egr065
Rooney, Tyrone O. ; Hanan, Barry B. ; Graham, David W. ; Furman, Tanya ; Blichert-toft, Janne ; Schilling, Jean Guy. / Upper mantle pollution during Afar plume-continental rift interaction. In: Journal of Petrology. 2012 ; Vol. 53, No. 2. pp. 365-389.
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Rooney, TO, Hanan, BB, Graham, DW, Furman, T, Blichert-toft, J & Schilling, JG 2012, 'Upper mantle pollution during Afar plume-continental rift interaction', Journal of Petrology, vol. 53, no. 2, egr065, pp. 365-389. https://doi.org/10.1093/petrology/egr065

Upper mantle pollution during Afar plume-continental rift interaction. / Rooney, Tyrone O.; Hanan, Barry B.; Graham, David W.; Furman, Tanya; Blichert-toft, Janne; Schilling, Jean Guy.

In: Journal of Petrology, Vol. 53, No. 2, egr065, 01.02.2012, p. 365-389.

Research output: Contribution to journalArticle

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Rooney TO, Hanan BB, Graham DW, Furman T, Blichert-toft J, Schilling JG. Upper mantle pollution during Afar plume-continental rift interaction. Journal of Petrology. 2012 Feb 1;53(2):365-389. egr065. https://doi.org/10.1093/petrology/egr065