Parameters of hot spots and thermochemical plumes

To estimate conditions of heat and mass transfer through plume channel, three kinds of plumes have been recognized: ( a) plumes located in oceanic and continental regions far from spreading zones; (b) plumes at the axis of a mid-ceanic ridge, and ( c) plumes situated near the ridge axis. Given geologic and geophysical data, the flow rates of the effused magma have been estimated. The flow rate values permitted us to estimate the thermal power of the source of the plumes formed at the core-mantle boundary. The source powers for the Bouvet, Hawaiian, and Iceland plumes are 1.57(.)10(7), 3.02(.)10(8), and 3.78(.)10(8) kW, respectively. We have analyzed the heat and mass transfer of a thermochemical plume rising from the core-mantle boundary. The most probable values of melt viscosity in the plume channel and Lewis numbers for a chemical additive which lowers the melting point at the core-mantle boundary have been obtained for plumes with N = (3.0-3.8)(.)10(8) kW, rising for 1-5 Myr. For these Lewis numbers, typical temperature drops. Delta T-II between the melting point of the massif and the temperature of plume sole have been found. For the given. Delta T-II at Le = 100-1000, such parameters as additive concentration, temperature drop, power, and time and velocity of rise are calculated for the plume source diameters at the core-mantle boundary, d(s), of 70 and 100 km.