Geochemical Processes in Volcanic Systems of Central Africa

Central African volcanic systems, particularly those aligned along the Cameroon Volcanic Line, record a complex interplay between mantle sources and continental lithospheric architecture. Geochemical studies reveal that melts originate from heterogeneous regions within the subcontinental lithospheric mantle and the underlying asthenosphere. Multi-isotope signatures (Sr–Nd–Hf–Pb) indicate contributions from refertilized lithospheric domains and recycled mantle components. Melting is driven by small-scale convection, lithospheric delamination and thermal erosion of ancient shear-zone fabrics. Once generated, magmas ascend through multi-level plumbing systems, with deep storage at the Moho and transient shallow pockets in the lower crust, where fractional crystallization, magma mixing and minor crustal assimilation further modify melt chemistry. These processes underlie the diversity of Central African basalts, dolerites and intermediate magmas, informing assessments of volcanic hazard and subsurface resources.

Research from Nature Portfolio

Recent studies have demonstrated that diverse intraplate basalts along the West African margin can form without a mantle plume, instead deriving from two fusible regions within the refertilized subcontinental lithospheric mantle and the sub-lithospheric mantle. Isotopic analyses have linked variations in basalt chemistry to rift architecture and small-scale mantle convection at the base of the lithosphere.

Another investigation using mineral–melt equilibrium thermobarometry on products of the 1999 and 2000 eruptions of Mount Cameroon has revealed a multi-part magma plumbing system. Primary storage occurs at Moho depths (20–39 km), while shallow magma pockets (3–12 km) become active during repose intervals, highlighting episodic magma recharge, storage and ascent beneath the volcanic line.

Geochemical Processes in Volcanic Systems of Central Africa publication trend

The graph below shows the total number of articles in geochemical processes in volcanic systems of central africa across all publications each year (not limited to Nature Index journals).

Technical terms

Subcontinental lithospheric mantle: the chemically heterogeneous upper mantle beneath continental crust that sources intraplate magmas.

Asthenosphere: the ductile, convecting layer of the upper mantle beneath the lithosphere where melt generation occurs.

Fractional crystallization: the sequential crystallisation of minerals from a cooling magma, altering the composition of residual melt.

Thermobarometry: techniques that use mineral compositions to estimate the temperature and pressure conditions of magma storage and crystallisation.

Isotopic systems (Sr–Nd–Hf–Pb): radiogenic isotope ratios employed to trace mantle versus crustal contributions in magmas.

Dyke: a tabular igneous intrusion cutting across pre-existing rock strata, serving as a conduit for magma ascent.

References

1. Origin of ocean island basalts in the West African passive margin without mantle plume involvement. Nature Communications (2019).
2. Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon. Scientific Reports (2016).
3. Petrography and Geochemical Characterization of Dolerites from Figuil (Northern Cameroon) and Léré (Southwestern Chad). International Journal of Geosciences (2020).
4. Petrochemical constrains on the origin and tectonic setting of mafic to intermediate dykes from Tikar plain, Central Cameroon Shear Zone. Discover Applied Sciences (2021).