Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 41, Issue 7, Pages 2304-2311Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2014GL059424
Keywords
Geochemistry; Intra-plate processes; Mantle processes; Composition of the mantle; Hotspots
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Funding
- Petrology and Geochemistry program of NSF [EAR-1019489]
- Division Of Earth Sciences
- Directorate For Geosciences [1019489] Funding Source: National Science Foundation
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We report combined He-Ne-Ar isotope data of mantle-derived xenoliths and/or lavas from all segments of the East Africa Rift System (EARS). Plume-like helium isotope (He-3/He-4) ratios (i.e., greater than the depleted MORB mantle (DMM) range of 81R(A)) are restricted to the Ethiopia Rift and Rungwe, the southernmost volcanic province of the Western Rift. In contrast, neon isotope trends reveal the presence of an ubiquitous solar (plume-like) Ne component throughout the EARS, with (Ne-21/Ne-22)(EX) values (where (Ne-21/Ne-22)(EX) is the air-corrected Ne-21/Ne-22 ratio extrapolated to Ne-B) as low as 0.034, close to that of solar Ne-B (0.031). Coupling (Ne-21/Ne-22)(EX) with He-4/He-3 ratios indicates that all samples can be explained by admixture between a single mantle plume source, common to the entire rift, and either a DMM or subcontinental lithospheric mantle source. Additionally, we show that the entire sample suite is characterized by low He-3/Ne-22(S) ratios (mostly < 0.2)a feature characteristic of oceanic hot spots such as Iceland. We propose that the origin of these unique noble gas signatures is the deeply rooted African Superplume which influences magmatism throughout eastern Africa. We argue that the Ethiopia and Kenya domes represent two different heads of this common mantle plume source.
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