Geochemistry of Woranso–Mille Pliocene basalts from west-central Afar, Ethiopia: Implications for mantle source characteristics and rift evolution

Mulugeta Alene, William K. Hart, Beverly Z. Saylor, Alan Deino, Stanley Mertzman, Yohannes Haile-Selassie, Luis B. Gibert

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The Woranso–Mille (WORMIL) area in the west-central Afar, Ethiopia, contains several Pliocene basalt flows, tuffs, and fossiliferous volcaniclastic beds. We present whole-rock major- and trace-element data including REE, and Sr–Nd–Pb isotope ratios from these basalts to characterize the geochemistry, constrain petrogenetic processes, and infer mantle sources. Six basalt groups are distinguished stratigraphically and geochemically within the interval from ~ 3.8 to ~ 3 Ma. The elemental and isotopic data show intra- and inter-group variations derived primarily from source heterogeneity and polybaric crystallization ± crustal inputs. The combined Sr–Nd–Pb isotope data indicate the involvement of three main reservoirs: the Afar plume, depleted mantle, and enriched continental lithosphere (mantle ± crust). Trace element patterns and ratios further indicate the basalts were generated from spinel-dominated shallow melting, consistent with significantly thinned Pliocene lithosphere in western Afar. The on-land continuation of the Aden rift into western Afar during the Pliocene is reexamined in the context of the new geochemistry and age constraints of the WORMIL basalts. The new data reinforce previous interpretations that progressive rifting and transformation of the continental lithosphere to oceanic lithosphere allows for increasing asthenospheric inputs through time as the continental lithosphere is thinned.

Original languageEnglish (US)
Pages (from-to)187-200
Number of pages14
JournalLITHOS
Volume282-283
DOIs
StatePublished - Jun 1 2017
Externally publishedYes

Keywords

  • Afar rift
  • Basalt
  • Geochemistry
  • Lithosphere
  • Mantle Plume

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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