The most complete results of the study of hydrothermal ore-forming solutions geochemistry in the Russian and international expeditions to deep-sea hydrothermal fields of the world ocean are analyzed. Solutions of both high and low salinity with respect to seawater are formed in the discharge zone of fluids. Positive correlation of ore components with the chloride ion and negative one with the pH value may indicate the migration of components in acidic hydrothermal solutions in the form of chloride complexes. Hydrogen sulfide is associated with the significant positive correlation with metals, which indicates reducing conditions forming in ore-bearing hydrothermal solutions. This is confirmed by the close relationship of ore components with hydrogen. The transfer of metals mainly in the form of chloride complexes at high temperatures of the solution is confirmed by the results of our thermodynamic modeling. Methane is characterized by negative dependence on temperature and concentration of ore components, associated with positive dependence on pH and negative one on hydrogen sulfide. Each of the observed dependencies can testify against abiotic theory of income of methane in hydrothermal solutions. The following geochemical indicators are the most promising for the discovery of new ore deposits and the organization of geochemical monitoring during the development of already discovered fields: Eh, pH, Cl, Fe, Mn, H 2 S, CO 2 , H 2 and possibly CH 4 .
The article deals with hydrogeochemical processes in the productive strata in the course of oil field development. The impact of flooding on the change of the chemical composition of reservoir water and the possibility of salification are analyzed. Computer thermodynamic modelling of physico-chemical processes is used for prediction of salification in oil fields.
The article deals with the role of groundwater in methane formation in coal fields of North-East Vietnam using the example of Maohe deposit. Main geochemical processes during groundwater filtration in a coal bed are determined.
The results of Russian and international expeditions for investigation of hydrothermal plumes and solutions in the Atlantic tropic zone on deep Mid-Atlantic Ridge hydrothermal fields connected with ultrabasic rocks are considered. Visual observations and sampling using submersibles and tow vehicles show the unsteady character of hydrothermal discharge, phase separation of high-temperature (~350 °C) solutions with high content of hydrogen and methan, iron and manganese, low pH and changeable on time and fields area mineralization. High content of H2 and CH4 could be connected with interaction of ultramafics with seawater on high-temperatures and pressures and serpentinization processes.
Features of submarine hydrothermal discharge and geochemical anomalies in bottom waters of Mid-Atlantic Ridge are observed. In the typical section of hydrothermal halos two major zones could be distinguished: forming by the rising stream gravitationally non-stable structures and more stable formations on the horizon of lateral flow. Discrete structure of hydrothermal plumes and matter differentiation are discussed. Different types of fluid discharge are revealed on the Logatchev field. As a result three kinds of hydrothermal plumes are forming: of positive, neutral and negative buoyancy.
The main geological and thermodynamic conditions of hydrothermal vents formation and activity. Calculation of hydrothermal field vents flow have been made after E.S.Romm model. A comparison of model data with data obtained in the Russian-French expedition «SERPENTINE».
A genesis of hydrothermal solutions of the explored area is observed. A short characteristic of main settings determining the ore-forming features of hydrothermal solutions is given. The groups of elements connected with the hydrothermal solutions-seawater mixing are marked out as well as those coming directly from the magmatic chamber and contacting rocks.
Geological and tectonic settings and thermobaric characteristics of hydrothermal activity are confronted with those of gas hydrate formation. Hydrocarbon concentrations and isotopic composition in hydrothermal fluids of mid-ocean ridges with different thickness of sediment cover and marginal oceanic basins are compared. The possible influence of rising thermal fluids on gas hydrate accumulations was analyzed and examples of hydrate formation linked with hydrothermal process are given.
The paper reviews the main methods and analyzes modeling results for geochemical processes in the submarine discharge zone of hydrothermal solutions of mid-ocean ridges. Initial data for modeling have been obtained during several marine expeditions, including Russian-French expedition SERPENTINE on the research vessel «Pourquoi Рas?» (2007). Results of field observations, laboratory experiments and theoretical developments are supported by the analysis of regression model of mixing between hydrothermal solutions and sea water. Verification of the model has been carried out and the quality of chemical analysis has been assessed; degree and character of participation of solution components in the hydrothermal process have been defined; the content of end members has been calculated basing on reverse forecasting of element concentration, depending on regression character; data for thermodynamic modeling have been prepared. Regression model of acid-base properties and chloridity of mineralizing thermal springs confirms adequacy of the model of double-diffusive convection for forming the composition of hydrothermal solutions. Differentiation of solutions according to concentrations of chloride-ion, depending on temperature and pH indicator within this model, is associated with phase conversions and mixing of fluids from two convection cells, one of which is a zone of brine circulation. In order to carry out computer thermodynamic modeling, hydro-geochemical and physicochemical models of hydrothermal discharge zone have been created. Verification of the model has been carried out basing on changes of Mn concentration in the hydrothermal plume. Prevailing forms of Mn migration in the plume are Mn 2+ , MnCl + , MnCl 2 . Two zones have been identified in the geochemical structure of the plume: 1) high-temperature zone (350-100 °С) with prevalence of chloride complexes – ascending plume; 2) low-temperature zone (100-2 °С), where predominant form of transfer is a free divalent ion – lateral plume. Sulfate complex in insignificant quantities (1.5 %) is detected in the lateral plume, whereas hydroxide complex is stable at temperatures 325-125 °С and can only be found in the ascending plume. Results of modeling almost fully correspond to field observations. Verification of thermodynamic model proves its adequacy and allows to make a transition to the next stage of research – examination of geochemical dissipation for key ore components of hydrothermal solutions – Fe, Cu, Zn etc.
The conditions for the occurrence of near bottom minerals presented in the form of sulphides (the Logachev deposit) and ferro-manganese nodules (The conditions for the occurrence of benthic minerals presented in the form of sulphides (the Logachev deposit) and ferro-manganese nodules (FMN) are considered. An analysis of the structures and parameters of various means of collecting and transporting sulphides and iron ore from the bottom to the surface is given, and the possibility of effectively using vessel lifting on a cable-rope is indicated. Structural schemes for collecting FMN and sulphides in the form of containers on a cable, equipped with manipulators with gripping devices of a disc, drum or clamshell type, are proposed. In them, the capture of rock pieces or FMN is carried out by creating a vacuum in the collectors of the executive bodies and attracting to them pieces of rock or FMN by a pressure drop of water inside and outside the reservoir. It was given the approximate parameters of the mining system. So, for a cable-rope made of kevlar with a diameter of 50 mm, the capacity can be 200-400 thousand tons per year for one installation with different specific mass concentration of FMN per 1 m 2 ) are considered.