Studying deep sources of volcanism using multiscale seismic tomography

• An overview of multi-scale seismic models in different volcanic areas is presented.
• Mantle sources of intraplate and collisional volcanism are considered.
• Multi-level tomographic models reveal the feeding paths of subduction-related volcanoes.

This paper presents an overview of several examples of multiscale studies of different volcanic systems including intracontinental, collisional and subduction-related volcanic areas. Regional tomographic models of the upper mantle are presented for three regions with the Cenozoic intracontinental volcanism in Eurasia, namely Europe, Southern Siberia and Eastern Arctic. In all cases, recent volcanic fields correlate with low-velocity anomalies in the mantle. The modeling results show that these volcanic manifestations are related to large hot areas in the mantle and not to thin column-shaped contrasted plumes, as presumed by many. Collisional-type volcanism is discussed with an example of the Caucasus and the surrounding areas. The regional tomographic model for this region reveals a lack of mantle lithosphere beneath the collision zone. Volcanism in this area is most likely due to the direct heating of the thick crust by the hot asthenosphere. A dominantly felsic composition of the crust facilitates upward transport of the fluids and melts that leads to volcanic eruption. Subduction-related volcanic systems are discussed for three different scale levels. An example of a regional model of the mantle beneath the Sunda arc reveals the general configuration of the slab. Middle-scale tomographic models in areas of the Toba Caldera, Central Java and Central Andes display feeding paths of the arc volcanoes from the slab. The feeding paths are apparent in all of the considered cases but have different shapes depending on the unique features of the subduction regimes. An example of a detailed local-scale study of magmatic sources in the crust is discussed for the Kluchevskoy volcano group. It is found that the main volcano, Kluchevskoy, is fed through a complex three-layered system of magma sources. Another volcano of the same group, Bezymianny, seems to be connected with the mantle through a direct short-lived channel, which appears only during the eruption periods. A time-dependent tomography study performed for this group over a period of ten years clearly reveals the correlation between the changes in the seismic structures and the stages of the volcanic process, namely, preparation, activation and relaxation.