Chemical interactions in carbonate rock–seawater, silty sand–seawater, clay rock–seawater, basalt–seawater, and granite–seawater systems, where the term “seawater” denotes the compositions of halite, epsomite, and sylvinite stages of seawater densification, were simulated at 25, 100, 200, and 300°С and various pressures in order to assess the ability of rocks to generate hydrocarbons. Based on the efficiency of hydrocarbon generation, the rocks are arranged in the following series: clay > silty sandstone > carbonate > mafic rocks; felsic rocks are unproductive. It is shown that with an increase in the weight rock/water ratio (R/W), which may be taken as the conditional time (degree) of metamorphism, the reduction potential (lgfH2) of rocks, i.e., their ability to generate hydrocarbons, increases. At R/W → 1, the reduction potentials (lgfH2) for carbonate, clay, and silty sandstone are –2.74, –2.45, –2.57 at 100°С, –1.2, –1.1, –1.0 at 200°С, and –0.5, +0.3, –1.2 at 300°С, respectively, which shows a clear advantage of clay at high temperatures (pressures) in terms of its ability to reduce chemical elements and generate hydrocarbons. Thermodynamic modeling of interactions in a closed water–mineral precipitate–natural organic matter system at the T–P parameters of diagenesis was performed. A mature type of kerogen and associated substances (water-dissolved hydrocarbons, nitrogen compounds) are formed in the system in the course of the reactions. It is shown that the removal of CO2 (g) and N2 (g) from the system promotes hydrocarbon and kerogen formation reactions. It was found that the water phase changes insignificantly during kerogen formation. In general, the effect of desalination and changes in pH and Eh, as well as the increase in the content of CO2 dissolved in the water, is significant.

The paper briefly describes some of the problems solved at the Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, to illustrate the possibilities and limitations of the promoted physicochemical computer simulation method. The computer simulation results on the formation of hydrocarbons in the Earth’s crust, acid drainage estimates, and other results of the method, obtained by researchers of the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, and colleagues of Tomsk Scientific Polytechnic University, are reported in separate papers.

Thermodynamic modeling with the HCh software complex was applied to analyze the probability of acid drainage formation during the evolution of a copper–ore deposit in low-temperature conditions (5°C) with various water levels. During the modeling, three main factors were taken into account: the percentage of pyrite in rocks, the availability of oxygen in the air, and the water content of the rocks (the relative rate of water exchange). It was found that the increase in the content of pyrite sulfur in the rock and an increase in the ratio of the rock–water mass (decrease in water exchange) lead to an increase in mineralization and a decrease in the pH of the drainage solution. The openness of the system to atmospheric gases (in particular, to O2) increases the acidification effect. The most environmentally unfavorable rocks at the deposit are mudstones, siltstones, and silt-sandstones.

Гидрогеологические исследования в России ведутся по многим направлениям, начиная от оценки ресурсной базы подземных вод, заканчивая изучением механизмов геологической эволюции системы вода-порода-газ-органическое вещество. Эту широту исследований показало Всероссийское совещание по подземным водам Востока России (XXII совещание по подземным водам Сибири и Дальнего Востока) состоявшееся 18-22 июня 2018 года в г. Новосибирске в Институте нефтегазовой геологии и геофизики им. А.А. Трофимука СО РАН. В работе совещания приняли участие 138 ученых из 79 научных, образовательных и производственных организаций.

Thermodynamic simulation of the system “Rocks of Pavlovskoe polymetallic deposit – water – atmosphere gases” predicts aqueous concentrations from mineral solubilities and speciation with the HCh geochemical code. It is shown the model solutions are alkaline and rich in some microelements (As, Cd, Se, Co, Cr, Cu, Ni, Pb, Ga, Ge, Sr, In); their concentrations are overcome MPC, especially on the ore storage site.

Hydrogeological studies in Russia are conducted in many areas, ranging from the assessment of the groundwater resource base to the study of water-rock-gas-organic matter system geological evolution. This breadth of research was shown by the All-Russian Conference on Groundwaters of Eastern Russia (XXII Conference on groundwater of Siberia and Russian Far East with international participation) held on June 18-22, 2018 in Novosibirsk at the Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch of Russian Academy of Sciences (IPGG SB RAS). The meeting was attended by 138 scientists from 79 scientific, educational and industrial organizations.

Analysis of chemical equilibria among iron and manganese aqueous species at various Eh-pH conditions and aqueous CO2 concentration is done. Thermodynamic and equilibrium-kinetic simulation of iron and manganese aqueous species oxidations is developed for groundwater demanganation and deironing. Numerical simulation of chemical interactions in the system groundwater-aqueous oxygen-rock minerals-aqueous carbon dioxide is shown that deironing is effective enough but aqueous manganese(II) concentration is increased. It occurs because (Fe,Mn)CO3 solubility rate is too slow and (Fe,Mn)CO3 dissolution and removal of aqueous iron species results in secondary MnCO3 formation. Using published experimental data on carbonate dissolution kinetics, iron and manganese oxidation kinetics and the critical values of rate constants of iron and manganese homogenous oxidation, iron and manganese carbonates solubility, manganese homogenous catalytical oxidation on iron hydroxide suspension are chosen. The kinetics-thermodynamics model of underground oxidation of iron and manganese by dissolved oxygen have been developed. By numerical simulation of chemical interactions in the system groundwater saturated by oxygen-stratal water-intake rock minerals shows that deironing occurs effective enough but aqueous manganese concentration increased. It happens due to aqueous manganese slow oxidation and dissolution of (Fe,Mn)CO3. Also secondary MnCO3 formation is possible due to removal of aqueous iron specis. So underground demanganation is possible if there is no (Fe,Mn)CO3 among intake rock minerals or inconvenience of water contact with it.

Выполнено термодинамическое компьютерное моделирование системы «породы месторождения Павловское–вода–газы атмосферы». Показано, что модельные дренажные воды имеют слабощелочной рН, а также оценена их опасность в отношении концентраций ряда нормируемых микроэлементов (As, Cd, Se, Co, Cr, Cu, Ni, Pb, Ga, Ge, Sr, In), существенно превышающих предельно допустимые концентрации (ПДК), особенно на участках складирования руды.

Thermodynamic modelling of the system of “Pavlovskoe rocks-water-atmoshere gases” is done. The modelling aqeous solutions are alkaline. The concentrations of normalized elements (As, Cd, Se, Co, Cr, Cu, Ni, Pb, Ga, Ge, Sr, In) are much higher their mcl standards, especially on the ore storehous sites.

Выполнен анализ химических равновесий между соединениями железа и марганца в зависимости от окислительно-восстановительных и кислотно-основных условий среды (Eh-pH) и содержания углекислоты. Проведено термодинамическое и равновесно-кинетическое моделирование окисления железа и марганца при различных содержаниях углекислоты в растворе применительно к задаче подземного обезжелезивания и деманганации воды водозабора. Выбраны наиболее достоверные величины констант скоростей конгруэнтного растворения карбонатов железа и марганца, констант гомогенного окисления железа и поверхностно-каталитического окисления марганца на взвеси гидроксида железа в водном растворе. Разработана кинетико-термодинамическая модель подземного окисления железа и марганца растворенным в воде кислородом. Моделированием установлено, что обезжелезивание воды происходит достаточно эффективно, в то время как содержание марганца (II) в воде возрастает. Это происходит по причине более медленного окисления марганца и растворения Mn-содержащего сидерита. Эффективная подземная деманганация воды возможна при отсутствии Mn-содержащего сидерита в породах.

The paper presents data on the average analyzed concentrations of volatile components (CO2, CH4 and other hydrocarbons, N2, and H2S) in natural fluids producing hydrothermal Au, Sn, W, Mo, Cu, Pb, and Zn mineral deposits. Characteristics of the gas regime at these deposits are determined. Thermodynamic simulations are carried out to model how compounds with volatile components are formed when water interacts with silicic and mafic rocks within wide P–T ranges. The speciation of volatile components determined by direct analysis is in good agreement with numerical simulations of water–rock systems (for silicic and mafic rocks). More reduced species with volatile components are formed in mafic rocks.

КОМПЬЮТЕРНОЕ МОДЕЛИРОВАНИЕ КАК МЕТОД ДЛЯ ГЕОХИМИЧЕСКОЙ ОЦЕНКИ ЭКОЛОГИЧЕСКОГО

The relevance of the research is caused by the necessity to evaluate the changes in groundwater chemical composition due to water-rock interaction. Usually the source of water, the H2O molecules namely, and the source of dissolved components are considered separately. In the study the atmosphere precipitates is the source of H2O. As water is used for different purposes (potable water supply, industrial water supply), it must correspond to the specified water use standards. Water quality depends on it quality and composition. Water chemical composition depends, on its turn, on the structure of rock at interaction, interaction time and contact with atmosphere. The main aim of the study is to determine granite alteration and age of potable water chemical composition formation due to granite -meteoritic water interaction. Methods of research: thermodynamic simulation of water-rock interaction using HCh code developed by Yu.V. Shvarov. The equilibrium state algorithm is based on Gibbs free energy minimization and on chemical reactions system solution. The results. It is shown that in the «water-granite» system, open in respect to O2 and CO2, the Na-HCO3 composition of potable water forms during 3000 years. The aqueous solution pH value, which resulted from water-rock interaction, increases up to 7,8 but aqueous solution Eh value decreases from 0,79 to 0,62 V. The aqueous calcium concentration is limited by secondary minerals formation and deposition: dolomite and apatite.

Membrane filtration technique was applied to study the distribution of iodine and some other chemical elements (iron, manganese, aluminum, and silicon) in natural waters between different sized fractions (>0.45, 0.45–0.22, 0.22–0.1, and <0.1 μm). The paper presents analysis of factors able to modify the proportions of the adsorbed and dissolved species of the elements in waters. It is proved that up to 90% of the total amount of the iodine ion occurs in aquatic environments in the form of dissolved species (according to the current standard, in the fraction < 0.45 μm), with approximately 49% of the total concentration corresponding to the fraction of <0.10 μm. An increase in the acidity of the waters and their enrichment in finely divided organic and mineral material, and also an increase in Fe and Mn concentrations, may increase in the concentrations of the trace element in the particulate matter (up to 26% of the total iodide concentration). The greatest variations in iodine distribution between different fractions are found in the surface waters.

Formation of hydrocarbons in the seawater - mineral substance - living matter system is modeled. Some systems of various living matter compositions and stoichiometry and also at several sets of T,P parameters are simulated. During diagenesis kerogens and hydrocarbons are formed. The equilibrium constant of the reaction between oily kerogen and oxidized one, methane and CO2 is evaluated: Φ1C292H288O12(kerogen, H/C 0.99, O/C 0.041) → Φ2C128H68O7(kerogen, H/C 0.53, O/C 0.055)+xСH4+yCO2+zH2O, where Φ1 and Φ2 moles of kerogens; x, y, z – stoichiometry coefficients. In thermodynamically closed system the aqueous natural hydrocarbons are stable up to 300оС (at pressure above water saturated vapor) due to reductive environment formation (lg f H2 ≈ 10-4 бар). Equilibrium mineral assemblages of the system include quartz, kaolinite, muscovite, ankerite, siderite, pyrite, (Ca,Mg)CO3, (Ca,Sr)CO3 and paragonite. High salinity Cl-HCO3-Na aqueous solution also contains CO2 of tens g/l and ammonium nitrogen.