Seismic visualization of plumes and super-deep fluids in mantle under Ukraine

Abstract

According to the Taylor approximation of the three-dimensional P-velocity model of the mantle under Eurasia, a seismic visualization of the manifestation of mantle plumes and super-deep fluid processes was carried out. As initial data, the times of the first arrival of the P-wave were used according to the ISC bulletins for the period 1964—2006. The research area is defined in the interval (45—50° N)Ч(23—48° E) to the depth of 2500 km, in the interval (51—55° N)Ч(23—48° E) to the depth of 1700 km according to the used observation system and includes a mantle near Sarmatia (including the territory of Ukraine) and its surroundings. The fluid domain is defined as the region of the yields of low-velocity heterogeneities from the lower, middle mantle to the upper one and spreading along the laterals of their central part. The central, low-velocity part of the fluid domain is defined as a plume. Hence, the fluid domain is an area associated with traces of the passage of plumes. The mantle under the territory of Ukraine is under the influence of the North-Azov, Volyn-Orsha and Central-Black Sea fluid domains and regions of their spreading. The upper mantle above the central part of the North-Azov fluid domain (to a depth of 525 km) and above the central part of the Volyn-Orsha fluid domain (to a depth of 300 km) is high-velocity one. In the case under consideration, taking into account the absence of manifestations of the outlet of the central region of the fluid domain from the lower mantle and the presence of a high-velocity upper mantle, it can be expected that both of these central regions associated with the manifestation of plumes are in the decay stage. The central regions of both the North-Azov and Volyn-Orsha fluid domains belong to the areas of articulation of tectonic structures. The North Azov fluid domain is confined to the junction of the Khoper megablock of the Voronezh Massif and the Donbas, the Volyn-Orsha to the Kursk megablock of the Voronezh Massif, the Orsha Depression (Volyn-Orsha aulakogen) and the north-western part of the Dneprovo-Donets Basin. In the area of spreading of both the North-Azov and Volyn-Orsha fluid domains, 12 super-deep fluids are emitted.