Accompanied by intensive CO2 emission, submarine volcanic activity at equatorial latitudes of the globe creates the necessary conditions for the formation of coral reefs. In the process of its evolution, the coral head is getting compacted and turns into a water impermeable thickness (cap-rock), which plays a role of heat insulator. The big thickness of the cap rock (up to 2km) leads to the rise in temperature in the depths of hydrothermal-magmatic systems. Rocks with high content of silica can melt partially and form the chambers of acid magmatic melts in the Earth's crust as well as the secondary flows of volatile components. H2O and CO2 are the main volatile components. The migration of CO2 in the hydrothermal-magmatic system occurs in the form of diffusion and jet streams and is due to its weak chemical reaction activity in water and silicate melts. The migration of the gas phase of CO2 in the water-bearing complex is controlled by the upper relative water impermeable horizont, the formation of which is conditioned by the processes of acid and propylite metamorphism. The bubbles of CO2 rise along the border of the gas impermeable barrier which is usually tilted from the top of the volcanic edifice to its periphery. They combine into jets and stimulate the boil in a vertical column located above the apical part of the rock body at a depth of about 2km. Such uprising carbonated hydrothermal column acts as a gas lift pump. As a result of pumping of hydrothermal fluids, a hydraulic depression contacting with the igneous convective system appears in the water-bearing complex. Water vapor, which has high heat capacity, experiences tremendous heat losses in the magmatic convective column, immersed in the area of the thermal energy generation in the lower crust and upper mantle. The balance in favor of strengthening of the diffusion flux of CO2 is caused by the increase of the thickness and decrease of the permeability of the upper water impermeable cover, which evolution is connected with the activities of the condensate water of the surface formation. Rise in temperature of the water, caused by the evolution of the insulating properties of the cover, is accompanied by its vaporization, degassing, phreatic and phreatic-magmatic explosions. The connection between volcanic structures and limestone organic formations, including coral structures, is not random, but genetically determined. Such hydrothermal-magmatic systems are characterized by great heat capacity, which manifests itself in the surface thermal manifestations, in the places of exploitation of geothermal resources, and in the areas of the high intensity of minerals and ore deposits. The skarn type hydrothermal deposits are found in the depths of such systems. This model describes, in particular, geological and hydrogeothermal situation which existed in the areas of Apennine Peninsula (Larderello Monte Amiata geothermal region) and California Cordillera (Geysers-Clear Lake geothermal field).

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