Italian researchers have created a theoretical model of volcanism in the area North-East of China and the Japanese trench. According to the calculations, the volcanoes emerged as a result of loss of water by the edge of the Pacific lithospheric plate in the transition zone between the upper and lower mantle. The results of a study published in the journal Nature.
The principal mechanisms of nucleation, growth and solidification of magma on the Earth’s surface associated with either the passive rise of magma in the Central parts of the oceans (mid-ocean ridges), release of volatile compounds in the zones of lithospheric plates dive into the mantle (subduction) or by movement to the surface of the mantle plumes. However, the Cenozoic intraplate volcanism in northeast China and the formation of young volcanoes of the Japanese trough these processes can not be explained. Models of seismic tomography showthat these areas of the Pacific plate “stuck” in the transition zone of the mantle that separates the upper and lower mantle and extends almost 1000 km deep under the North-Eastern part of China.
It is assumedthat Cenozoic intraplate magmatism is associated with the release water of the Pacific slab in the transition zone. According to the studies of electrical conductivity, the transition zone of the mantle on average, contains about a tenth of a percent water by weight. Under the territory of North-Eastern China and Japan this part of the magma is more humid, it is estimated between 0.5 and one weight percent water. The transition zone is composed mainly of minerals that can be linked from one to three mass percent of water, which is almost two orders of magnitude higher solubility of water (hydrogen) in minerals of the upper and lower mantles. This difference suggests that, when plates sink into the mantle, they cause a vertical flow of matter from the more humid transition zone to the upper layers, allowing magma to form and be released on the Earth’s surface.
To test this hypothesis Jianfeng Yang (Yang Jianfeng) and Manuela Faccenda (Manuele Faccenda) from the University of Padova have developed a theoretical model of immersion of the plate in the humid transition zone of the mantle and subsequent processes.