| Abstract |
The evolution of hydrothermal process (high-temperature haloid-sulphur-carbon dioxide stage? sulphur-carbondioxide? low-temperature-carbon dioxide stage) reflects the series of reducing heat capacity of fractured and layer-fractured geothermal fields: solfatara thermals as steam (Nizhnekoshelevskiye, Okeanskiye, Geizers) ? solfatara thermals with steam near the surface and fluid at the depth (Mutnovskiye)? chloride geyser thermals (Pauzhetka, the Taupo Zone in New Zealand)? non-chloride geyser thermals (Bolshe-Bannyie). The results from the universal character of the compositional changes in magmatic emanations during the processes of silicate melt cooling and water temperature reduction. When volcanic-plutonic phenomena control the hydrothermal process, the change of haloid-sulphur-carbon dioxide stage with the sulphur-carbon dioxide and later on by the carbon dioxide one proper, lowers the contrasts among the compounds forming volcanic (fumarole) and magmatogene (hypogene) solutions. In such cases, compositions of two types of synchronously originating hydrothermals gradually become more similar, and the general vertical metasomatic zonality reduces to the products of carbon- dioxide (hydrocarbonate) metasomatosis. Taken separately, the zones of the general metasomatic column constitute a single system with no isolated degradation of concrete zones possible. This provides the grounds of the correlation principle for metasomatic zones; according to this principle, availability of certain alteration zones in thermal fields always suggests the presence of concrete alteration zones with characteristic temperatures in the entrails of hydrothermal system. Zeolite and smectite (zeolite-smectite, smectite-zeolite) facies of hydrothermal argillites, making a kind of "basis" for hydrothermal activity, are the exceptions. Proceeding from the correlation principle and detailed study of the mineral compositions of surface metasomatites in active thermal manifestations, one can make rather accurate estimations of hydrothermal reservoir temperatures, acidity and alkalinity of the environment, reveal the changes in dynamics and physical and chemical parameters of hypogene fluids with time, and consequently, to reconstruct the evolution of hydrothermal system. |