Geochemistry and Distribution of Recycled Domains in the Mantle Inferred From Nd and Pb Isotopes in Oceanic Hot Spots: Implications for Storage in the Large Low Shear Wave Velocity Provinces

• Published in: Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2018-09, Vol.19 (9), p.3496-3519
• Main Authors: Jackson, M. G., Becker, T. W., Konter, J. G.
• Format: Article
• Language: English
• Subjects: Basalt; Earth; Earth mantle; Geochemistry; geodynamics; Geographical distribution; Hot spots; Isotopes; Latitude; LLSVP; Magma; mantle plumes; Ocean circulation; Oceanic crust; Plumes; Seismic velocities; seismology; Shear wave velocities; Spatial distribution; Storage; Subduction; Tropical climate; Upwelling; Velocity; Wave velocity; Zonation
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2018GC007552

Subduction of continental and oceanic crust is thought to give rise to geochemically distinct reservoirs in the mantle called EM (enriched mantle) and HIMU (high μ = 238U/204Pb), respectively. However, the locations of EM and HIMU domains in the Earth's interior are poorly constrained. We explore the geographic distribution of extreme EM (143Nd/144Nd ≤ 0.512630) and HIMU (206Pb/204Pb ≥ 20) geochemical signatures in ocean island basalts erupted at hot spots, highlighting three observations. First, hot spots geographically associated with the two large low shear wave velocity provinces (LLSVPs) have a similar range of EM compositions. If these hot spots are sourced by the LLSVPs via upwelling plumes, this observation is consistent with the hypothesis that the LLSVPs formed by similar processes and have similar geodynamic histories. Second, the EM and HIMU domains exhibit different latitudinal zonation: oceanic hot spots with the most extreme EM compositions (143Nd/144Nd  0.512630) compositions. In contrast, the HIMU domains do not show a clear geographic association with the LLSVPs. Therefore, EM and HIMU domains in the Earth's mantle exhibit different spatial distributions. This may reflect differences in subduction inputs of these two components, or differences in how they segregate or accumulate in the deep Earth. Key Points Heavy radiogenic isotopic data for 42 oceanic hot spots are evaluated as a function of hot spot location, including position over the LLSVPs Geochemically enriched (EM) hot spots are concentrated in the Southern Hemisphere, and HIMU hot spots are found near the tropical latitudes The two LLSVPs have remarkably similar EM compositions; EM hot spots are geographically associated with the LLSVPs, but HIMU hot spots are not