Plate tectonics

Geology

Transition zone

Lithosphere

Mantle wedge

Oceanography

Hotspot (geology)

Upwelling

Asthenosphere

Geochemistry

Mantle plume

Seismology

Earth science

Subduction

Volcanism

Tectonics

Intraplate earthquake

Mantle (geology)

Geophysics

Nature

Most magmatism occurring on Earth is conventionally attributed to passive mantle upwelling at mid-ocean ridges, to slab devolatilization at subduction zones, or to mantle plumes. However, the widespread Cenozoic intraplate volcanism in northeast China1–3 and the young petit-spot volcanoes4–7 offshore of the Japan Trench cannot readily be associated with any of these mechanisms. In addition, the mantle beneath these types of volcanism is characterized by zones of anomalously low seismic velocity above and below the transition zone8–12 (a mantle level located at depths between 410 and 660 kilometres). A comprehensive interpretation of these phenomena is lacking. Here we show that most (or possibly all) of the intraplate and petit-spot volcanism and low-velocity zones around the Japanese subduction zone can be explained by the Cenozoic interaction of the subducting Pacific slab with a hydrous mantle&nbsp;transition zone. Numerical modelling indicates that 0.2 to 0.3 weight per cent of water dissolved in mantle minerals that are driven out from the transition zone in response to subduction and retreat of a tectonic plate is sufficient to reproduce the observations. This suggests that a critical amount of water may have accumulated in the transition zone around this subduction zone, as well as in others of the Tethyan tectonic belt13 that are characterized by intraplate or petit-spot volcanism and low-velocity zones in the underlying mantle. The widespread intraplate volcanism in northeast China and the unusual ‘petit-spot’ volcanoes offshore Japan could have resulted from the interaction of the subducting Pacific slab with a hydrous mantle&nbsp;transition zone.

Intraplate volcanism originating from upwelling hydrous mantle transition zone