Magmatic anomalies in oceanic domains: from laboratory experiments to natural laboratories

The style and amount of magmatism can significantly vary from one context to another. Seismic reflection imaging revealed plume-ridge interaction in the Bay of Bengal (Kerguelen hotspot), which we interpret as intra-oceanic rifting (Shang et al., 2025). In addition, the lithospheric mantle at the base of oceanic plates can reveal electrical conductivity anomalies, with values ≥ 10^-1 S m^-1 when average peridotites exhibit values as low as 10^-2 S m^-1, which can be due to connected networks of garnet pyroxenites according to recent experiments (Ferrand & Chin, 2023). Conductive anomalies can be anisotropic, fossilizing magma underplating in the spreading direction at the LAB (Ferrand, 2020b). Furthermore, very recent development allows study conductivity during deformation at deep lithospheric conditions (Ferrand et al., 2025), which may contribute to understanding the seismo-volcanic crisis in Mayotte.