The line of research by the Institute of Experimental Mineralogy RAS is 'Physical-chemical problems of the processes of mineral, rock, and ore formation in the Earth's crust and mantle as a basis for forecast and search for the mineral deposits'. This issue is all-embracing covering 6 fundamental an applied and a search problems.
Moreover, the Institute undertakes studies on:
State scientific program 1.7. 'Global changes in the environment and climate' and two projects of the federal target program 'Integration' aimed at the consolidation of higher educational institutions and academic science.
Project N 145. The promotion of the regional branch of Moscow State University in the scientific center of Chernogolovka.
Project N 250. Matter upon high static compression conditions. Experimental mineralogy of highly compressed mantles of the Earth and planets. The investigations are supported by the projects of the Russian foundation for basic researches (35 of them are headed by the Institute), three projects 'INTAS' and other Russian and foreign projects.
Project CR&DF RC1-170. 'Hydrogen bonds in supercritical fluids'.
Project RFBR-DSRS 96-05-00020. 'Experimental and theoretical studies of rhythmic-layered textures in the domes of rare-metal granites'.
The main research goals lie in solving fundamental problems in geology, geochemistry, mineralogy, and physico-chemical petrology in accord with the priority research lines of the Russian Academy of sciences and the geology, geophysics, geochemistry, and mining departments of the RAS.
The theoretical and experimental results of prime significance were obtained on some of the above research directions in 1998 which allowed to gain in the search for rock deposits and contribute to the development of the fundamental Earth's sciences.
The most important results are listed below and considered in more detail in short papers of this issue. See also the list of publications in the end of the issue.
The major results of the scientific research by the Institute of Experimental Mineralogy RAS in 1998.
1. Magmatic genesis of fine-banded granitic bodies of Orlovka and Etyka tantalum deposits was proved experimentally. It was shown that they were formed under high saturation of residual melt in fluorine (up to 3 wt%). Ta solubility in such a melt is 0.1-0.2% which corresponds to maximum Ta concentration in ores and can be an argument in favor of its magmatic origin.
Based on the experimental and petrologic data the physical-chemical parameters and character of formation of specific fine-banded granitoid bodies were determined. This bodies are characteristic of ore-bearing apical part of Ta-bearing Li-F granites of rare-metal East Transbaikalia deposits of Orlovka and Etyka. Their internal structure and composition of 4 major varieties of repeatedly alternating layers of banded bodies (microgranite, albite, K-feldspar , and 'greisen'). The beginning of melting of each layer was experimentally determined in the P-T range 550-800oC and 0.5-3 kbar. The solidus temperature was found to be about the same for all the varieties of the banded bodies: 700-750oC at 0.5 kbar, 650-700oC at 1 kbar, 620-650oC at 2 kbar, 600-630oC at 3 kbar. High saturation of the melt and separated at its crystallization hydrothermal fluid in fluorine is a specific condition of the banded granites formation: up to 3wt% F in the ultimate melt fractions and up to 1.5-2.0 mole HF /kg H2O in the coexisting aqueous fluid.
The columbite-tantalite solubility has been experimentally studied both in the melts of individual layers of stratified rocks and in the melts of massive Li-F granites. The maximum solubility of tantalum in microgranite, albite, K-feldspar, and 'greisen' melts at T=850oC, P=1kbar was found to be 0.18, 0.13, 0.14, and 0.10 wt% which practically corresponds to the maximum tantalum concentrations in ores.
The obtained experimental data give more evidence of the magmatic genesis of banded bodies and tantalum ores in Li-F granites. The origin of both banded bodies and tantalum ores is likely to be tightly related to crystallization peculiarities of the ultimate fractions of magmatic melt of Li-F granites saturated in H2O, F, T, and other rare elements (Prof. G.P.Zaraisky, Dr. A.M.Aksyuk ., Dr. V.Yu.Chevychelov).
2. The theory and graphical methods for the construction of system phase diagrams or their principal schemes by isoconcentration joins has been developed which is of fundamental importance and allows construction of the full phase diagram using scarce experimental data.
Phase diagrams of condensed systems are of prime significance for understanding the genesis of magmatic rocks of various compositions. Since the natural systems are multicomponent and multifactor, the experimental study of individual joins is the only reasonable way which makes it possible the prediction and calculation of the full diagram. The solution of the problem involves: a) experimental study of the join; b) estimation of the obtained thermodynamic parameters; c) topological forecast of the possible versions; d) thermodynamic selection of the possible states; e) numerical calculation and construction of diagrams; f) control experiments and correction of diagrams (according to the above scheme); g) using the diagrams for genetic constructions. The procedure is being matured, its efficiency is first estimated for simple systems. ( Ac.Sci.F. V.A. Zharikov).
3. Diamonds close in their physical properties to the most pure 'nitrogen-free' natural diamonds of IIa type were first synthesized in alkaline carbonate-carbon melts of the system Na2Mg(CO3)2- K2Mg(CO3)2-C at pressures 80-90 kbar. The results obtained contribute to the theory of diamond genesis in the Earth's mantle and development of the new unconventional technology of its synthesis.
The diamonds synthesized by a new method in carbonate-carbon melts of the system Na2Mg(CO3)2-K2Mg(CO3)2-C at 80-90 kbar and 1600-1800oC are close in their physical properties to the most pure 'nitrogen-free' natural diamonds of the IIa type, which was first established by the methods of scanning electron microscopy, color and spectral cathodoluminescence. These diamonds differ on fundamentals from the conventional 'metal-carbon' synthetic diamonds with the characteristic high content of paramagnetic nitrogen (type I b). The results obtained are of prime importance for the physical-chemical theory of diamond genesis in the Earth's mantle, as well as for the development of a new unconventional technology of diamond synthesis in alkaline-carbonate systems in particular of diamond monocrystals of high purity for electronic engineering and jewelry. (Prof. Yu.A. Litvin, Dr. L.T Chudinovskikh).
4. Based on the D.S. Korzhinsky's hypothesis on the transmagmatic sulfurization the model of formation of the giant copper-nickel platinum-bearing deposits of the Norilsk type has been developed. These deposits were formed as a result of the fluid sulfurization of iron-rich ultrabasic magmatic differentiates. The sample drilling at the Norilsk trapp formation contribute much to the development of the model. The drilling results revealed the volcanic analogies of Norilsk ore-bearing intrusives featuring elevated content of the ore metals complex (platinum, palladium, chromium). The determined trend is representative of the magmatic process of ore concentration and corresponds to sulfide-free and sulfide-poor ore horizons of the Bushveld and Norilsk intrusives. In Bushveld this trend corresponds to the iron rich platinum-bearing differentiates (hortonolite dunites).In the Norilsk sulfide ores the established trend of properly magmatic ore concentration is accompanied by the giant concentration in them of copper and chalcophile metals which can not be explained by the magmatic processes. Such a complex polygenic composition of the Norilsk sulfide ores can be only attributed to the transmagmatic sulfurization of iron-rich magmatic differentiates corresponding to the platinum-bearing hortonolite dunites. Direct evidence of such a sulfurization was obtained by the detection of relict chromites in the copper-nickel platinum-bearing sulfide ores. They were close in composition to spinel-chromite mineralization of hortonolite dunites.
The developed original model of sulfurization is important for the solution of the general problem of the origin of rich sulfide ores always containing huge iron masses, which could be explained only by its magmatic concentration. However, the model needs further special experimental investigation. (Academician A.A. Marakushev).
5. Direct long-term measurements of the state parameters of high temperature volcanic gases (v. Kudryavy, South Kurils) were first performed using a sensor apparatus designed in the IEM RAS. State parameters (T, P, pH, aCl2, aO2) of the high temperature fumarole gas were measured in the monitoring regime at two fumaroles at 900 and 760oC. A unique hydrogen discharge with its concentration in the gas increasing by a factor of 8 and reaching 8 mole% was first registered at the volcano at the stage of stationary fumarole activity.
For the first time in the world using the sensor-apparatus complex designed in the IEM RAS and built in home the direct long-term measurements of the state parameters of volcanic gases were performed in an automatic mode at T=900oC at the Kudryavy volcano , South Kurils, is. Iturup, featuring the highest fumarole activity. The most important and unexpected result of the measurements performed was that hydrogen concentration long time maintaining at a level of 1 mole% spontaneously increased on 8 October 1998 and reached the maximum value of 10 mole% on 10 October. The duration of hydrogen discharge was 4-4.5 days. The excessive gas pressure in the volcanic channel at the moment of outburst increased from 80 mm H2O in the still period up to 180 mm, the natural potential measured between hot fumarole and cool zone increased, temperature rose by 20oC. On October 6, 7, and 8 the discharge was preceded by seismic events. These events were registered by the Kurilsk seismic station within the radius of 100-110 km and their intensity was 2 points on the Richter scale. Thus, it could be supposed in the first approximation, that the registered hydrogen discharge is caused by the endogenic processes in the vicinity of the surface magmatic chamber which, in their turn, were provoked by the seismic events.
An increase in hydrogen concentration in fumarole gases of the volcano Kudryavy as compared to other volcanos is not a forerunner of the discharge. These interrelation, however, needs further investigation. (Dr.M.A. Korzhinsky, M.Sci. N.N. Zhdanov).
6. The study on the problem of high level wastes disposal. (The leader ac. V.A. Zharikov). The topological analysis of hydrolysis reactions and computation of the joint solubility of solid phases parageneses with the participation of strontium hydroxide-apatite, goyazite, and strontium hydrophosphate in the boundary system SrO-Al2O3- P2O3-H2O have been performed at T=25-350oC and Psat. The hydrolysis of Na-Al-phosphate glass has been studied at the above parameters. The calculations of the joint solubility of the solid phases ternary parageneses involving Sr-hydroxide-apatite (SAP) , goyazite (GO), and Sr-hydrophosphate (SPH) have been completed in the closed system SrO-Al2O3-P2O3-H2O. The compositions of eutonic solutions corresponding to the boundaries of phase transitions VAR=BER, GO+SPH=BER+SAP, and GO=BER+SAP+DSP on the P-T diagram of the system have been calculated at the phases ratio 1:1:1 at 25, 186, 260, and 300oC and Psat. It was found that SAP has the minimum solubility among Sr-phases (n.10-7 mole/kg H2O) and SPH has the maximum one (n.10-4mole/kg H2O). The topological analysis of this system open for the P2O3 component was done. The qualitative diagram T-lgP2O3 has been constructed. The boundary gain-loss reactions of P2O3 component divide the diagram into three regions: variscite (VAR), berlinite (BER), and diaspore (DSP) ones overlapped by the GO, SAP, and SPH fields. (Prof. I.P. Ivanov, M.Sci. N.P. Kotova).
7. A simple and effective thermodynamic model of the complex water-salt fluid has been developed. The model application was proved using original experimental data on fluid-mineral equilibria.
The relations activity-composition have been first experimentally studied in binary supercritical fluid systems water - sodium chloride, water - potassium chloride, and water - carbon dioxide in the wide range of temperatures (600-1000oC), pressures (2-15 kbar), and component concentrations. It was found that H2O activity in water-salt systems decreases sharply with pressure at P>4 kbar. The mixing effect in the system H2O-CO2 is positive up to the pressure of 15 kbar even at high temperature (1000oC).Based on the experimental data a simple thermodynamic model of the water-salt fluid has been developed wherein component activity is a function of effective degree of the dissociation of a corresponding electrolyte which depends on T, P, and density of the solvent (H2O). Calculations on the proposed model reconstruct the curves of salts' melting in the presence of H2O within experimental accuracy. Component activities in the system H2O-CO2 are described by a simple equation analogous to the van-Laar one with only three empirical coefficients. The expressions obtained are well extrapolated at least up to the pressure of 0.5 kbar and 500oC. The model of a three-component fluid based on the additivity principle well describes the experiments on the layering in the ternary system H2O-CO2-chloride of an alkaline metal. The equations derived allow for the reliable and accurate calculations of fluid-mineral equilibria and more realistically estimate the activity of fluid components in the processes of abyssal petrogenesis. The proposed equations could be also used for the calculation of the volumes of gas-water-salt mixtures at elevated T and P, necessary for a number of technologies. (Prof. L.Ya. Aranovich).
8. For the first time in the world experimental data have been obtained on temperature and concentration dependencies of H2O and H2 solubilities in magmatic melts in the full range of their basicity from the acidic (albite) to ultrabasic (picrite) ones. The effect of H2O and H2 pressures on the rheological properties (viscosity, activation energy of viscous flow) of the melts in the system albite-diopside has been studied at T=1125-1400oC and P H2 and H2O up to 5 kbar.
The viscosity of the melt of Ab75Di25composition was found to decrease with PH2O by 1.5 orders of magnitude at PH2O=4 kbar and T= 1300oC as compared to its viscosity at atmospheric pressure. A slight decrease ( » by a factor of 1.5) in viscosity of Ab75Di25 melt under hydrogen pressure (PH2=4kbar, T= 1400oC) has been discovered which is comparable with the effect of lithostatic pressure on the viscosity of the melt.
By contrast to the temperature dependence of H2o solubility, H2 solubility in an albitic melt was shown to increase with temperature. As it was for the first time established experimentally, H2 solubility increases with increasing basic properties of magmatic melts which is opposite of the concentration dependence of H2O solubility. The development of the amphoteric nature of H2O at its dissolution in magmatic melts was proved: in the acid-basic compositional range, H2O is a base with respect to the melt and its dissolution is accompanied by the growth of basicity (depolymerization degree) of melts and increase in viscosity and activation energy; in ultrabasic melts H2O is an acid and its dissolution is followed by a growth of acidity (polymerization degree) of melts and increase in viscosity and activation energy.
Hydrogen solubility in magmatic melts proceeds by two mechanisms: chemical dissolution of H2O (as OH hydroxide) in the melts containing the elements of variable valence (Fe, Ni etc.) and physical dissolution (H2® Ho+Ho) in the melts lacking the above elements. (Prof.E.S. Persikov, Dr. P.G. Bukhtiyarov).
9. The study has been performed on the platinum and palladium solubility in water-saturated and silicate melts depending on the redox conditions in the range of oxygen fugacity in natural mineral formation. The data obtained elucidate the geochemical behavior of these elements in the evolution processes of magmatic chambers.
Experimental studies have shown that Pt and Pd solubility increases by several orders in silicate melts in the presence of water-hydrogen fluid as compared to the corresponding data obtained for dry conditions. A decrease in oxigen fugacity in equilibrium with water-saturated melt leads to the essential drop of Pt and Pd solubility in it up to MW buffer equilibrium. However, with further decrease in lgfO2 the solubility curves are found to differ sharply: Pd solubility goes on decreasing with the change of the slope whereas Pt solubility on the contrary increases.
The EMR analysis of Pt and Pd valence under different redox conditions showed that palladium in all the studied lgfO2 range and platinum up to the MW buffer did not form paramagnetic ions in a silicate melt. However, under more reducing conditions the signals of paramagnetic Pt ions are observed. Formation of Pt-bearing clusters is one of the possible mechanisms of platinum dissolution under reducing conditions. Pt and Pd complexation in a fluid is usually related to OH-, HS- or Cl- ions in melts, high temperature hydromagmatic fluids being suggested to separate from the magma and migrate through the melt. Upon changing physical-chemical conditions (T, fO2) they may localize in certain zones as layers (rifts). In this case Pt/Pd ratio , according to the obtained data, is much determined by the redox conditions (Prof. N.I. Bezmen).
10. Sulfur solubility in water-bearing basaltic melts has been first studied in the P-T range of 1250-1350oC and 1-25 kbar. Depending on T-P-X conditions, sulfur solubility varies from 0.6 to 2.6 wt% SO3, which is more than order higher than its solubility in 'dry' basaltic melts at the same parameters. Sulfur solubility increases with increasing melt basicity and temperature. Pressure dependence of solubility is of extreme character with a maximum in the region of 11-13 kbar. The conditions of sulfide saturation of water-bearing basaltic magmas at different levels of the Earth's crust and upper mantle have been considered.
Sulfur solubility in water-bearing basaltic melts has been first studied at P=1-25 kbar, T= 1250-13500oC, and quartz-fayalite-magnetite-pyrrhotite O2S2 buffer in order to elucidate the conditions of sulfide-silicate layering in water-bearing magmas and genesis of the related deposits. Depending on T-P-X parameters, sulfur solubility in water-bearing melts varied from 0.6 to 2.6 wt% SO3 which is more than order higher than its solubility in 'dry' melts at the same parameters. Sulfur solubility increases with increasing FeO content, acidity-basicity of the melt, and temperature. Sulfur solubility increases by a factor of 1.9 from 1.37 to 2.58 wt% SO3 with temperature increasing from 1250 to 1350oC at P=15 kbar. Pressure dependence of solubility is of extreme character with the maximum in the range of 11-15 kbar.
Water-bearing magmas compared to the 'dry' ones have a high ore-bearing potential due to their unique ability to dissolve high amounts of sulfur as well as chlorine, noble metals (Pt, Au). As sulfur solubility in water-bearing melts is high, sulfide saturation can be achieved at high sulfur concentrations. That is why the sulfur liquation , particularly an early one, in such melts is hampered. An important factor that favours the achievement of sulfide saturation by water-bearing magmas is the change in their chemical composition, i.e. an increase in sulfur and silicate concentration of the melt, a decrease in its basicity in the process of crystallization differentiation, crust contamination. The upper horizons of the mantle and Earth's crust are the most favorable for the sulfide saturation of the basic magmas. (Dr.Sci. N.S. Gorbachev).
11. Physical-chemical modeling of the Akhchatau W-Mo greisen deposit formation, Central Kazakhstan.
The calculation of the pore-crack paleopermeability of a part of the granite massif of Akhchatau at the stage of greisen- and ore-formation has been completed The results of the experimental study of porosity and permeability of rocks, field observations and theoretical generalizations allowed to reproduce the evolution of temporal and spatial cracks formation process. It was shown that at pre-ore and basic ore stages of aplite and quartz-muscovite greisens formation, permeability could increase by 3-7 times compared to permeability of intact rocks; formation of quartz-tourmaline veins proceeded without notable increase in permeability, only in a few cases it grew by a factor of 1.8. Essentially, permeability of the Akhchatau massif has been determined by the permeability of the matrix and, did not exceed tenths of milliDarcy. (Prof. G.P. Zaraisky, Dr. V.M. Shmonov, Dr. V.M. Vitovtova, M.Sci. S.S. Matveeva, T.G. Pavlova (MSU)).
The book 'Experimental and theoretical modelling of the processes of mineral formation' (553p.) has been published in the edition Nauka in 1998. The book resumes the scientific results by the Institute for the last few years. 69 scientific papers appeared in Russian journals and 35 in foreign ones. A special issue of the journal 'Experiment in Geosciences' V7 N1 1998 presents 60 short reports which resume the work of the Institute in 1997. 59 papers are in press (37- in Russian journals and 22- in the foreign ones). More than 40 abstracts have been submitted to the all-Russian and international conferences, symposia, and congresses. In 1998 2 positive decisions have been received for the RF patents and 1 application for invention, a Philosophy Dr. thesis has been defended.
The work aimed at the development of the Institute and its reorganization.
In 1998 the institute received a high state appraisal for the fundamental and applied investigations in the field of experimental mineralogy and physical-chemical petrology. The reorganization and consolidation of the research directions targeted at the further growth of the efficiency of scientific investigations, using financial sources and staff experience.
There are 5 scientific laboratories and 2 research groups , laboratory of physical investigations the group of scientific information and experimental-technological department in the Institute. The staff of the Institute runs to 225 persons, among them 2 follows of the ac.sci.,17 professors, 43 doctors, and 16 researchers.
The integration with higher educational and ministry science.
The leading scientists of the Institute V.A. Zharikov, A.A. Marakushev, L.L. Perchuk, G.P. Zaraisky, A.R. Kotelnikov, T.V. Gerya, O.G. Safonov gave lectures at the Geological department and department of improvement in skill of the Moscow state University. The students of the geological department of the Moscow state University and other educational Institutes get practical experience at the IEM RAS.
In 1998 the Institute continued the work on projects 145 and 250 of the federal program 'Integration' aimed at the consolidation of educational and academic science. In the framework of the program the steps were taken for the organization of the branch of geological department of the Moscow state University in Chernogolovka . The structure, special educational programs have been approved by the rector of the university and grounding of highly skilled specialists is to be started in 1999.
5 post-graduate students were granted a research work at the Institute in 1998. 1 Philosophy Dr. thesis has been defended. 2 Doctor of Sc. theses have been prepared.
The prizes awarded.
In 1998 the scientists of the IEM RAS were awarded the following prizes:
Director of the IEM RAS,
Ac.Sci.F. V.A. Zharikov,
Scientific secretary Dr. V.V. Fed'kin.of the IEM RAS,
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