Mantle Geochemistry and Oceanic Volcanism

Earth’s mantle is chemically and isotopically diverse, reflecting a complex history of melting, recycling and metasomatic alteration. The convecting upper mantle, or asthenosphere, gives rise to oceanic volcanism at mid-ocean ridges, hotspots and arc systems. Basalts erupted at mid-ocean ridges (MORB) sample convecting depleted mantle characterised by low concentrations of incompatible elements, whereas ocean island basalts (OIB) often tap enriched domains derived from recycled crustal and lithospheric assemblages. Trace elements and radiogenic isotopes such as Sr, Nd, Pb and Hf record signatures of subducted oceanic crust, sediments and carbonates, enabling reconstruction of mantle flow patterns and crust-mantle cycling over geologic time. Recent advances in high-precision microanalysis and multi-component geochemical modelling have revealed metre-scale heterogeneities, challenging earlier paradigms of a homogenised mantle. This synthesis of mantle geochemistry and oceanic volcanism has profound implications for understanding plate tectonics, volcanic hazards and the long-term carbon cycle.

Research from Nature Portfolio

Recent studies have identified subduction-modified signatures in mid-ocean ridge basalts from regions outside typical back-arc settings. Analyses of Arctic Gakkel Ridge samples reveal enrichments in Ba, Rb and Pb coupled with Nb depletions, indicating a pervasive slab-derived flux incorporated into mantle flow beneath the ridge. Novel modelling suggests that a hemispheric “subduction shield” influences the transport and distribution of this component. High-resolution isotopic analyses of clinopyroxene crystals from Samoan hotspot lavas demonstrate extreme 87Sr/86Sr variability, confirming the presence of sediment-infiltrated mantle domains. These micro-analyses constrain the proportions of magma mixing between enriched and depleted melts and illuminate the fate of ancient sediments in the plume source. Foundational work on the role of recycled marine carbonates in generating HIMU-type basalts has also resolved longstanding Pb isotope paradoxes by showing that carbonate subduction can account for both high μ and low κ features in oceanic basalts.

Mantle Geochemistry and Oceanic Volcanism publication trend

The graph below shows the total number of articles in mantle geochemistry and oceanic volcanism across all publications each year (not limited to Nature Index journals).

Technical terms

Mid-ocean ridge basalt (MORB): Basaltic rock produced at divergent plate boundaries, typically depleted in incompatible elements.

Ocean island basalt (OIB): Volcanic basalt derived from mantle plumes or hotspots, often enriched in trace elements and radiogenic isotopes.

Asthenosphere: The mechanically weak, convecting layer of the upper mantle beneath the lithosphere.

Subduction-modified mantle: Mantle source regions chemically altered by fluids and melts from subducted oceanic crust and sediments.

HIMU (high-μ): A mantle component characterised by high 238U/204Pb ratios producing distinctive Pb isotopic compositions.

Isotopic affinity: The grouping of volcanic rocks based on similar radiogenic isotope ratios indicating common mantle sources.

References

1. A subduction influence on ocean ridge basalts outside the Pacific subduction shield. Nature Communications (2021).
2. Extreme isotopic heterogeneity in Samoan clinopyroxenes constrains sediment recycling. Nature Communications (2021).
3. Marine Carbonates in the Mantle Source of Oceanic Basalts: Pb Isotopic Constraints. Scientific Reports (2018).
4. Chemical Geodynamics Insights From a Machine Learning Approach. Geochemistry Geophysics Geosystems (2022).
5. Petrogenesis of Lava from Christmas Island, Northeast Indian Ocean: Implications for the Nature of Recycled Components in Non-Plume Intraplate Settings. Geosciences (2022).
6. Basalts of a Seamount on the Eastern Flank of the Charlie Gibbs Transform Fracture Zone, North Atlantic: Petrochemical and Isotopic Evidence of a Microplume-Affected Formation in the Axial Zone of the Mid-Atlantic Ridge. Doklady Earth Sciences (2023).