The Cameroon Volcanic Line and the intraplate volcanism enigma
The Cameroon Volcanic Line (CVL) extends SE from Cameroon towards the mid-Atlantic ridge (Fig. 1). Sustained magmatism occurred along the CVL for tens of millions of years, and volcanic volumes are significant (e.g. Mt. Cameroon is >4000 m tall).
Why does this volcanic chain exist? A linear chain of volcanoes can be related to a deep thermal mantle plume (e.g., Hawaii-Emperor chain hotspot and the Walvis Ridge, lying further south of the Cameroon Line; Gassmoeller et al., (2016)). However, the CVL lacks a clear age progression, meaning that more complex processes need to be invoked (e.g. lithospheric delamination, Ballmer et al., 2011). Non-plume mechanisms have been proposed, but are typically discipline-specific, with geophysical, geochemical, and geodynamical models each designed in isolation to match only their respective observations. For example, edge-driven convection, locally elevated mantle volatile contents, the breakup of Pangea, or small-scale convection have all been dynamically proposed (Kaislaniemi & van Hunen, 2014, Figure 2). A geodynamical model that reconciles independent constraints from seismology, petrology and geochemistry is lacking. The key objective of this project is to find such unifying model.
The relevance of this project goes beyond understanding the origin of the CVL: the outcome directly affects our knowledge of lithosphere development, evolution and stability, and sheds new light on processes shaping our continents such as craton destruction, continental breakup, and lithosphere-asthenosphere interaction.
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Map of NE part of the Cameroon Line, with intraplate volcanism exhibiting a NE-SW line across the continent-ocean boundary,Numerical modelling of edge-driven convection with application to the Atlas mountains volcanism. Mantle shearing triggers linear convection rolls (green sheets showing downwellings, and arrows showing velocity patterns), with decompression melting (red regions) occurring in the upwelling convective limbs (Kaislaniemi and van Hunen, 2014).