Vol 50, No 2 (2016)

The comparative tectonic characterization of transregional linear structures (zones of concentrated deformations) is given for the Pieniny Klippen Belt, the Main Mongolian Lineament, and the transregional Alpine Fault Zone. They represent significant geodynamic elements of the Earth’s crust, which separate large crustal segments and reflect their interaction in time and space. The main features of the structure, evolution, and geodynamics inherent to zones of concentrated deformations are described. It is shown that the similarity of their outlines, morphology, internal structure, and kinematic features is combined with a clearly distinct structural position, set of rock associations, formation mechanism, and their role in the origin of mobile belts.

Heat generation due to decay of long-lived radioactive isotopes is considered in the Earth’s crust of the Archean–Proterozoic and Paleozoic provinces of Eurasia and North America. The heat flow that forms in the mantle is calculated as the difference between the heat flow observed at the boundary of the solid Earth and radiogenic heat flow produced in the crust. The heat regime in regions with anomalously high radiogenic heat generation is discussed. The relationship between various heat flow components in the Precambrian and Phanerozoic provinces has been comparatively analyzed, and the role of erosion of the surfaceheat- generating layer has been estimated.

The relative plume thermal power Ka = N/N₁ is used (N is the thermal power transferred from the plume base to its conduit and N₁ is the thermal power transferred from the plume conduit into the surrounding mantle in the steady-state heat conduction regime). Thermochemical mantle plumes with small (Ka < 1.15) and intermediate (1.15 < Ka < 1.9) thermal powers are formed at the core–mantle boundary beneath cratons in the absence of horizontal free-convection mantle flows beneath them, or in the presence of weak horizontal mantle flows. Thermochemical plumes reach the Earth’s surface when their relative thermal power is Ka > 1.15. The thermal and hydrodynamical structure of the plume conduit ascending from the core–mantle interface to the level from which the magmatic melt erupts on the Earth’s surface is presented. The model of two-stage eruption of the melt from the plume conduit to the surface is considered. The critical height of the massif above the plume roof, at which the eruption conduit supplying magmatic melt to the surface forms, is determined. The volume of melt erupting through the eruption conduit to the surface is estimated. The dependence of depth Δx from which the melt is transported to the surface on the plume diameter for a kinematic viscosity of ν = 0.5–2 m²/s is presented. In the case when the value Δx is larger than the depth starting from which diamond is stable (150 km), the melt from the plume conduit can transport diamonds to the Earth’s surface. The melt flow in the eruption conduit is considered as a turbulent flow in a cylindrical duct. The velocity of the melt flow in the eruption conduit and the time for the melt to be transported to the surface from a depth of Δx = 150 km for a kinematic viscosity of the melt in the eruption conduit ν_v = 0.01–1 m²/s are determined. Tangential stress on the eruption conduit sidewall is estimated in cases of melt flow both in smooth and rough conduits.