Imaging Lithospheric Discontinuities Beneath the Northern East African Rift Using S-to-P Receiver Functions

Aude Lavayssiere, Catherine Ann Rychert, Nicholas Harmon, Derek Keir, James Hammond, J M Kendall, Cecile Doubre, Sylvie Leroy

Research output: Contribution to journalArticle (Academic Journal)

6 Citations (Scopus)
307 Downloads (Pure)

Abstract

Imaging the lithosphere is key to understand mechanisms of extension as rifting progresses. Continental rifting results in a combination of mechanical stretching and thinning of the lithosphere, decompression upwelling, heating, sometimes partial melting of the asthenosphere and potentially partial melting of the mantle lithosphere. The northern East African Rift System is an ideal locale to study these processes as it exposes the transition from tectonically active continental rifting to incipient seafloor spreading. Here we use S‐to‐P receiver functions to image the lithospheric structure beneath the northernmost East African Rift System where it forms a triple junction between the Main Ethiopian rift, the Red Sea rift and the Gulf of Aden rift. We image the Moho at 31±6 km beneath the Ethiopian plateau. The crust is 28±3 km thick beneath the Main Ethiopian rift and thins to 23±2 km in northern Afar. We identify a negative phase, a velocity decrease with depth, at 67±3 km depth beneath the Ethiopian plateau, likely associated with the lithosphere‐asthenosphere boundary (LAB), and a lack of a LAB phase beneath the rift. Using observations and waveform modelling, we show that the LAB phase beneath the plateau is likely defined by a small amount of partial melt. The lack of a LAB phase beneath the rift suggests melt percolation through the base of the lithosphere beneath the northernmost EARS.
Original languageEnglish
Pages (from-to)4048-4062
Number of pages15
JournalGeochemistry, Geophysics, Geosystems
Volume19
Issue number10
Early online date3 Sep 2018
DOIs
Publication statusPublished - Oct 2018

Keywords

  • East African Rift
  • Lithosphere‐asthenosphere boundary
  • Continental rifting
  • Receiver functions
  • Partial melt

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