Data on the component composition and acid-base properties of cooling fluid in the systems H2O-CO2, H2O-NaCl, and H2O-rock-forming minerals, which were derived by minimizing the Gibbs free energy, and the evaluated contributions of major fluid components to its acid-base properties suggest that the main reason for the inversion of acid-base properties of magmatic fluids in the fluid-granite system is the opposite tendencies in the changes of the dissociation constants of acidic and basic fluid components in the course of fluid cooling.

The basicity-acidity of minerals and rocks is estimated by the Gibbs free energy minimization technique with the use of modern thermodynamic data (Selector-C program package). A provisional scale of acid-base properties of minerals and rocks is constructed based on the properties of pure water in equilibrium with them. The composition of solution under standard conditions and base-acid parameters (pH25) are calculated for reactions of pure water with various rock-forming minerals that dissolve congruently or incongruently. A method is suggested for evaluating the base-acid parameters of rocks on the basis of solving the inverse problems of convex programming of the composition and properties of solution (supercritical fluid) in equilibrium with a real mineral association.

The geological position, composition of mineral assemblages, and typomorphism of major minerals from garnet-bearing rocks at the Berezitovoe gold-base-metal deposit in the Upper Amur Region have been studied in detail. These are ore-bearing metasomatic rocks and metamorphosed porphyritic dikes. The garnet-bearing metasomatic rocks reveal zoning, which is caused by various degrees of metasomatic transformation of the Paleozoic porphyritic granodiorite that hosts the ore zone. The metasomatic replacement of granodiorite was accompanied by loss of Na, Ca, Ba, Sr and gain of K, Mn, and Rb. Garnet-bearing metamorphosed intermediate dikes occur within the metasomatic zone. The PT conditions of metamorphism and metasomatism are similar and estimated at 3.9 kbar and 500°C from various mineral equilibria. The results of physicochemical simulation of garnet-bearing mineral assemblages carried out by minimizing the Gibbs free energy and the geological data show that garnet-bearing mineral assemblages arose at the Berezitovoe deposit as a result of local high-temperature thermal metamorphism of previously formed low-temperature metasomatic rocks close in composition to classic beresite. In this connection, we propose considering garnet-bearing metasomatic rocks as high-temperature metamorphosed beresites.

Детально изучена геологическая позиция, состав минеральных ассоциаций и типоморфные особенности основных минералов гранатсодержащих пород Березитового золото-полиметаллического месторождения Верхнего Приамурья, которые представлены рудоносными метасоматитами и дайками метапорфиритов. Установлено, что рудоносные гранатсодержащие метасоматиты месторождения имеют зональное строение, что обусловлено различной степенью метасоматических преобразований палеозойских порфировидных гранодиоритов, вмещающих рудоносную зону месторождения. Формирование метасоматитов по гранодиоритам сопровождалось выносом Na, Ca, Ba, Sr и привносом K, Mn, Rb. Гранатсодержащие метапорфириты, развитые в пределах метасоматической зоны, представляют собой продукты локального метаморфизма дайковых пород среднего состава. Установлены однотипные РТ-условия формирования метапорфиритов и метасоматитов, которые по различным минеральным равновесиям оцениваются примерно в 3.9 кбар и 500°С. Результаты физико-химического моделирования гранатсодержащих минеральных ассоциаций месторождения, проведенного методом минимизации свободной энергии Гиббса, и геологические данные показывают, что гранатсодержащие минеральные ассоциации Березитового месторождения были образованы в результате высокотемпературного локального термального метаморфизма ранее сформированных низкотемпературных метасоматитов, близких по составу к классическим березитам. В связи с этим предлагается выделить гранатсодержащие метасоматиты месторождения в самостоятельную формацию высокотемпературных метаморфизованных березитов.

The generation of single chaotic microwave pulses in a self-oscillating ring system with ferromagnetic film under the action of external narrow-band noise microwave signal occurring outside the band of frequencies of the chaotic microwave signal was observed. Chaotic generation emerged due to the parametric instability of the magnetostatic surface wave in the ferromagnetic film, whereas formation of single chaotic microwave pulses was caused by the absence of complete suppression of chaos under the action of narrowband noise.

Описаны термодинамические модели минеральных твердых растворов, с использованием которых производится физико-химическое моделирование на программном комплексе (ПК) “Селектор-С” и решаются проблемы метаморфогенного минералообразования. Показано, что в модельных образцах расчетное распределение FeO и MgO между минералами гранат-биотит, гранат-ортопироксен, ортопироксен-биотит, ортопироксен-оливин, гранат-кордиерит, гранат-клинопироксен, клинопироксен-ортопироксен в первом приближении соответствует экспериментальным и эмпирическим данным. На примерах моделирования реальных минеральных ассоциаций продемонстрированы возможности новой версии ПК “Селектор-С” в изучении эволюции минеральных парагенезисов при изменении Р-Т условий и флюидного режима; установлено “вполне подвижное” и “инертное” поведение компонентов флюида при образовании минеральных ассоциаций; с помощью метода “псевдосекций” в широкой области Р-Т показано изменение составов минеральных ассоциаций в метабазитах и метапелитах гранулитовой фации; оценен верхний предел устойчивости плагиоклаза в этих породах по давлению величиной в 11-12 кбар. Установлена резко различная реакция обогащенных и обедненных трехвалентным железом пород на инфильтрацию в них метаморфогенного восстановленного флюида. Это выражается в том, что первые породы поддерживают свой “внутренний” окислительный потенциал на определенном уровне с помощью буферных реакций, тогда как вторые быстро теряют буферную способность и приобретают окислительный потенциал втекающего “внешнего” флюида. Это позволяет оценить величину lgfO2метаморфогенного флюида - не выше -17 (при Т = 700°С, Р = 6.8 кбар). Моделирование на конкретных образцах горных пород дает основание полагать, что реальные минеральные ассоциации могут быть образованы при небольшом весовом отношении флюид/порода - не более 0.01-0.06.

The paper presents thermodynamic models for mineral solid solutions used in physicochemical simulations with the SELECTOR-C program package (PP) in application to metamorphic mineral-forming processes. It is demonstrated that the simulated FeO and MgO distribution in the mineral pairs garnetbiotite, garnet-orthopyroxene, orthopyroxene-biotite, orthopyroxene-olivine, garnet-cordierite, garnetclinopyroxene, and clinopyroxene-orthopyroxene in the model samples satisfactorily corresponds to available experimental and empirical data. Simulations of naturally occurring mineral associations are employed to demonstrate the capabilities of the new version of the SELECTOR-C PP as a tool for studying the evolution of mineral assemblages at varying P-T conditions and fluid regime, the perfectly mobile and inert behaviors of certain fluid components during the origin of mineral associations are demonstrated, the pseudosection method applied over a broad P-T range is used to trace systematic variations in the composition of mineral associations in granulite-facies metabasites and metapelites, and the upper limit of plagioclase stability is estimated for these rocks at pressures of 11–12 kbar. Principal differences are elucidated in the effect of rocks rich and poor in Fe 3+ on the percolation of metamorphic fluid through them: Fe 3+ -rich rocks retain their own redox potential at a certain level by buffering reactions, whereas Fe 3+ -poor rocks rapidly exhaust their buffer capacity and acquire the redox potential of the inflowing external fluid. This allowed us to evaluate the log f O 2 at no higher than −17 (at T = 700°C and P = 6.8 kbar). Our simulation of the equilibrium of natural rock samples provides good reasons to believe that natural mineral assemblages can be formed at low fluid/rock ratios of no higher than 0.01–0.06.

Using a new version of the Selektor-C program package for the minimization of Gibbs free energy, physicochemical modeling was conducted for real mineral assemblages from the rocks of the Okhotsk and Chogar complexes and the Larba block, which crystallized under granulite-facies conditions. Considering a two-reservoir fluid-rock system, model assemblages of metapelites and metabasites adequate to natural assemblages were reconstructed by the method of Gibbs potential minimization. The P-T parameters of crystallization, oxygen potential, and the composition of the deep fluid that produced the assemblages were estimated. It was shown that the character of oxygen behavior can be dual under granulite-facies metamorphic conditions: inert behavior in rocks enriched in magnetite and (or) hemoilmenite and perfectly mobile behavior (after D.S. Korzhinskii) in rocks devoid of these minerals. It was shown that the oxygen regime is controlled by the degree of complete or partial leveling of oxygen potential between the deep reduced fluid and the rock in agreement with their oxygen capacities.

Chromatographic and electrochemical measurements, combined with computer simulation of the natural mineral parageneses and estimation of the stability field of muscovite-bearing assemblages, yielded a consistent model of the fluid regime for the amphibolite-facies metamorphism of the Dzhugdzhur-Stanovoy fold area (DSFA).

Using the Selektor-C software program package, oxidation potential and the composition of metamorphogenic fluid were determined for mineral assemblages from nine samples of granulite-grade metamorphic rocks by solving the inverse problems of convex programming. The calculated and real mineral assemblages are in good agreement with respect to the composition and association of minerals, which is compelling evidence for the attainment of chemical equilibrium (minimum of Gibbs free energy) under given P-T conditions. Based on the dual solution of the inverse problem, a new approach was proposed for the estimation of the oxidation potential of fluid and mineral assemblages, which can be used to determine oxygen potential for almost any mineral association, independent of the presence of magnetite, ilmenite, or graphite. It was found that magnetite-free mineral associations are characterized by highly reducing conditions corresponding to oxygen potentials close to the CCO buffer. The external metamorphic fluid that was present during granulite-facies metamorphism was probably formed in the graphite stability field. The results of calculations for the model aqueous electrolyte solution-mineral assemblage suggest high SiO2 solubility in the metamorphogenic fluid. Therefore, the process of granulite metamorphism may be a potent geochemical factor of the redistribution and transportation of silica from lower to upper crustal levels.

This paper reports the results of a comparison of the qualitative physicochemical simulations (by the Winsel program complex) of the composition of the reacting fluid with experimental data on the water-electrolyte (NaCl, HCl, NaOH, and KOH)-mineral (quartz, corundum, microcline, and plagioclase) system and the water-electrolyte-rock (granite and pelite) system at 400–800°C and 1–10 kbar. Constraints are proposed for the temperature, pressure, and the composition of the electrolyte at which the simulation results are consistent with the experimental data.

Discussed in this paper are the reasons of a significant discrepancy between the degrees of fluid, reduction in minerals of metamorphic rocks estimated by physical methods (gas chromatography and high-temperature electrochemistry) and phase correspondence analysis. A comparative analysis was used to elucidate the nature of the similarity of the redox state estimates for minerals (and fluids) obtained by instrumental methods and their deviation from those derived from the phase correspondence principle. A new reversible mechanism is supposed for the oxidation of ferrous iron in the structure of hydrous minerals and simultaneous formation of anomalously reduced fluids in the process of their thermal degassing. It was shown that hydrous minerals cannot be used for the estimation of oxygen fugacity by means of gas chromatography and high-temperature electrochemistry methods. It is suggested that the redox state of anhydrous minerals determined by these methods provides evidence on the condition of rock evolution rather than on the parameters of its crystallization.