Fingerprinting secondary mantle plumes

Many vertical seismic velocity anomalies observed below different parts of the Eurasian plate are rooted in transition zone between upper and lower mantle (410–660 km), forming so-called secondary plumes. These interpreted as result thermal effects large-scale upwelling (primary plume) or deep dehydration fluid-rich subducting oceanic plates. We present results thermo-mechanical numerical modelling to investigate dynamics such small-scale chemical (hydrous) rising from part Earth's mantle. Our objective is determine conditions that allow thermo-chemical plumes moderate size (initial radius 50 km) penetrate continental lithosphere, often detected seismo-tomographic studies. To this end, we examine effect following parameters: (1) compositional deficit plume density due presence water hydrous silicate melts, (2) width weak overlying lithosphere formed because plume-induced magmatic weakening and/or previous tectonic events, (3) a regime varied neutral extensional. In our models, purely origin do not plate, but flatten at its base, “mushroom”-shaped structures level lithosphere-asthenosphere boundary. On contrary, with enhanced contrast component shown be able pass upwards through lithospheric shallow depths near Moho when ? 100 kg m?3 weakness above km. An extensional facilitates penetration into mandatory. findings can explain observations have long remained enigmatic, “arrow”-shaped low velocities Tengchong volcano south-western China columnar (“finger”-shaped) anomaly within discovered more than two decades ago beneath Eifel volcanic fields north-western Germany. It appears characteristic feature only conventional located over presently downgoing slabs, also other settings.