| Keywords |
heat transfer, hydrothermal convection cell, magmatic convective cell, hydrothermal-magmatic system, sodium, potassium, volatile component, superheated steam, heat content |
| Abstract |
To increase the efficiency of heat extraction for industrial purposes the researchers are looking for a supercritical heat transfer medium (Fridleifsson et al., 2011). The deep well in Kakkonda H-MS made a transition from the hydrothermal convection cell to the hot igneous intrusion (Tamanyu, Fujimoto, 2005). Dunn and Hardee (1981) proposed the concept of the existence heat transfer with thermal parameters above critical in the hydrothermal-magmatic system zone with vigorous convection. However, such heat transfer medium was never obtained in the hydrothermal-magmatic system, where the drilling of geothermal wells was made. The maximum temperatures in those wells only reach critical values. Nevertheless, in the stationary columns of magma (extrusion) powerful jets of gas and steam (fumaroles) in the central volcanoes exist for a long time (tens - hundreds of years) indicating a powerful convective heat flow in the magmatic convective cell (on Kamchatka volcanoes Avachinsky – 60 000 kcal/s; Mutnovsky - ~400 000 kcal/s respectively). These and other data suggest that the problem of transporting large quantities of thermal energy in hydrothermal-magmatic system, which are observed in nature, is still not resolved. However, there is no doubt that the significant heat flows in magma act as a link between magmatic and hydrothermal cells. Thermophysical properties of sodium and potassium are typical for the magmatic-hydrothermal process. Sodium and potassium can be transported from the upper mantle to the Earth's surface at a significant rate due to the temperature difference these elements. These assumptions are confirmed by the composition of gases containing large amounts of metals, and sublimates around outputs of the superheated steam-gas jets. The evacuation of the volatile components creates conditions for their mobilization from magmatic chambers and along the entire length of the hot dyke characterized by large heat losses, resulting in the huge temperature gradient. Since alkali metals are characterized by large heat content and significant concentrations in the melt, they can play an important role in heat-and-mass transfer. Volatile components can create elevated concentrations in the head of the magmatic column and heat the sections of the host rocks, preparing the way for advancing successive portions of a magmatic melt. Undoubtedly, the magmatic gases participate in the processes of convective heat and mass transfer. According to the data obtained in the study of physical chemistry of pyrometallurgical processes, these gases are in a balance with a multi-component melt. According to the studies of the natural and artificial systems, when gases included in the composition of the melt pass through the complex processes of the chain reactions, they are converted to water vapor, HS-legislate and other gases. Alkali metals have a great influence on the chain reactions of gases. They affect the decrease in the temperature of the gaseous elements ionization and the increase in the internal energy of the volatile phase in magmatic melts. As mentioned earlier, the movement of the magmatic volatile phase of the melt is determined by the temperature pressure in the magma conducting structure. Heat losses in its upper part may control the flow of the heat transfer medium, in particular, alkali metals, and the heat flow from the upper mantle. Thus, the intensive extraction of the geothermal fluid of the hydrothermal convective cell of H-MS can be stimulated, but it should be controlled to prevent excessive heating of the magmatic convective cell which can cause a volcanic eruption. |