|Title||A common mantle plume source beneath the entire East African Rift System revealed by coupled helium-neon systematics|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Halldórsson SA, Hilton DR, Scarsi P, Abebe T, Hopp J|
|Journal||Geophysical Research Letters|
|Keywords||1025 Composition of the mantle; 1033 Intra-plate processes; 1038 Mantle processes; 8137 Hotspots, large igneous provinces, and flood basalt volcanism; Composition of the mantle; geochemistry; hotspots; Intra-plate processes; Mantle processes|
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 (3He/4He) ratios (i.e., greater than the depleted MORB mantle (DMM) range of 8 ± 1RA) 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 (21Ne/22Ne)EX values (where (21Ne/22Ne)EX is the air-corrected 21Ne/22Ne ratio extrapolated to Ne-B) as low as 0.034, close to that of solar Ne-B (0.031). Coupling (21Ne/22Ne)EX with 4He/3He 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 3He/22NeS 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.