Year: 2025
Type: article
Abstract: The Kenya plume drives rift formation and magmatism along the Kenya Rift, yet its components remain obscured by lithospheric overprinting on mafic volcanics. We present whole-rock geochemical data for mantle-derived silicic rocks from Suswa, sampled at the reworked craton margin of the Kenya Rift where continental lithosphere profoundly influences mafic rock compositions. These rocks exhibit high SiO 2 (54.9–60.4wt.%), total alkalis (Na 2 O + K 2 O = 9.3–13.8wt.%) and lithophile elements (Rb, Th-U, Nb-Ta and rare earth elements (REE); typically 10–100× chondrite and primitive mantle values), alongside low MgO (< 1.3wt.%). Their isotopic signatures show variable 87 Sr/ 86 Sr (0.7036–0.7056), depleted Nd-Hf isotopes ( 143 Nd/ 144 Nd = 0.51282–0.51285, 176 Hf/ 177 Hf = 0.28291–0.28293) and moderately radiogenic Pb isotopic ratios ( 206 Pb/ 204 Pb = 19.99–20.20, 207 Pb/ 204 Pb = 15.73–15.84 and 208 Pb/ 204 Pb = 39.82–39.97). The more depleted Nd isotopes compared to those of mafic rocks ( < ~ 0.51275) in the reworked craton margin and the northern Tanzania Craton, indicate minimal lithospheric incorporation. Low MgO contents, positive correlations of MgO with Al 2 O 3 , CaO, TiO 2 , P 2 O 5 , Ba, Sr and Eu, and characteristic REE and trace-element patterns support fractionation involving olivine, pyroxene, plagioclase, Ti oxide and apatite. Low Ba/Nb ratios, constant Rb/Nb and La/Nb ratios, and a negative 87 Sr/ 86 Sr–SiO 2 correlation preclude significant crustal contamination in most samples. Integrated Sr-Nd-Pb-Hf isotopic and trace-element systematics, combined with regional data, reveal a multi-component mantle source: plume-derived HIMU and depleted common mantle ( C ) components, plus a lithosphere-derived EMII component. Quantitative two-component mixing models, using the plume end-member ( C modified by HIMU -derived melt) and the lithospheric mantle end-member ( EMII modified by HIMU -derived melt), indicate 10–20% lithospheric contribution to the Suswa source. Critically, the identification of the C component within these depleted rocks, supported by literature data, confirms its presence within the Kenya plume. This underscores the imperative of targeting volcanic sequences with minimal lithosphere contamination to resolve the primary plume components beneath continents.
Source: Scientific Reports
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,690
Awards: G1042001938, G1281315562, G723508268
OpenAlex ID: W4416073614