Geodynamic regimes of thermochemical mantle plumes

Abstract

Laboratory and numerical experiments simulating the heat transfer and flow structure of thermochemical mantle plumes provide insights into the mechanisms of plume eruption onto the surface depending on the relative thermal power of plumes Ka=N/N1, where N and N1 are the heat transferred from the plume base to the plume conduit and the heat transferred from the plume conduit to the surrounding mantle, respectively, under steady thermal conduction. There are three main types of plumes according to the Ka criterion: (i) plumes with low thermal power (Ka<1.15), which fail to reach the surface, (ii) plumes with intermediate thermal power (1.15<Ka<1.9), which occur beneath cratons and transport melts from depths below 150km, where diamond is stable (diamondiferous plumes), and (iii) plumes with a mushroom-shaped head (1.9<Ka<10), which are responsible for large intrusive bodies, including batholiths. The volume of erupted melt and the depth from which the melt is transported to the surface are estimated for plumes of types (ii) and (iii). The relationship between the plume head area (along with the plume head diameter) and the relative thermal power is obtained. The relationship between the thickness of the block above the plume head and the relative thermal power is derived. On the basis of the results obtained, the geodynamic-regime diagram of thermochemical mantle plumes, including the plumes with Ka>10, has been constructed.