D.S.Korzhinsky and present-day petrology
(dedicated to the birthday centenary)
V.A.Zharikov

Dmitry Sergeevich Korzhinsky, fellow of the USSR Academy of Sciences, is an outstanding intellectual figure of the XX century. His brilliant discoveries and penetrating analysis have to a greatest extent predetermined the state of the art and prospects of the Earth's sciences (primarily geochemistry, petrology, and mineralogy which we shall, for brevity sake, call petrology).

We have no way, within the limits of time assigned to the report, of completely characterizing the creative heritage of D.S.Korzhinsky, we, therefore shall concentrate on his major discoveries and their current status (the gist of the report is reflected in tables I-VI.)

It should be mentioned that the fortune of the discoveries turned out different. Some gained a gradual evolution, the others gave rise to a drastic break-through with a change in the research methods and accents to follow, and still the others experienced a surprising regressive revision.

We shall consider the most important achievements of D.S.Korzhinsky following, mainly, the chronologic order and, of course, in brief.

1. In the thirties D.S.Korzhinsky developed the concept of mineral facies both in the general form and illustrated by the examples of Precambrian of Siberia and Paleozoic of Urals (Table I). Note, that the ideas of faciality of metamorphism were wandering in the minds of geologists at that time. But, according to the judgement of a leading "metamorphist" of the West P.Escola, D.S.Korzhinsky had developed those ideas so far on that none were capable of following him as yet. He was largely concerned with deep-seated mineral facies and temperature stages of metamorphism, water and carbon regimes of metamorphism, compositions of co-existing minerals-solid solutions as the base for facial analysis; finally, he wrote a number of brilliant monographies that would later find their way to each petrologist.

The mineral facies concept was generally recognized and extended in contemporary researches. The two new lines of research were of special importance: a) experimental studies of mineral equilibria and compositions of coexisting minerals in a broad T-P-range that laid the foundation of modern geothermobarofluidometry and b) development of local microprobe elemental and isotopic analysis. The results found their reflection in numerous P-T trend path diagrams of various metamorphic formations. In this respect this subject is nearly exhausted (at least methodically) and the researches' attention is now being focused on the intricate problems of the relationship between metamorphism and geodynamics with the aim of constructing quantitative models of metamorphic facies genetic series. Geochronometry of metamorphism (i.e. duration of metamorphic cycles) and metamorphic reactions kinetics are still burning problems.

2. Of all discoveries of D.S.Korzhinsky the most prominent is, undoubtedly, the recognition of the thermodynamic essence of natural systems as a new (for thermodynamics) type of systems with perfectly mobile components, cmc (Table II). The fundamental elaboration of the theory of equilibrium systems with cmc laid the foundation for the new line, namely, physical geochemistry concerned with physico-chemical regularities of origin of minerals, rocks, and ores, physicochemical processes of Earth's geospheres formation.

D.S.Korzhinsky had elaborated the thermodynamics of the systems with cmc so profoundly that only a few scientists were able to subsequently make their contributions to some of its domains (e.g. partial values in the systems with cmc).

The two lines of research have been pioneered: a) the development of the foundations of thermodynamics of natural irreversible processes and b) quantitative (numerical) calculations of individual models of equilibrium mineral systems.

Now a significant progress is dawning in the field of thermodynamics of natural systems. Great potentialities of computer techniques make it possible to solve particular problems including equilibrium states and irreversible changes in systems. It has become possible, in principle, to create universal dynamic models of natural processes with different-order steady states, even to the point of non-linear problems. But, numerical solution of particular geologic problems is of predominant importance.

3. Following attempts to graphically display the relationship between the chemical and mineral composition of metamorphic rocks (Tilli, Escola), D.S.Korzhinsky creates physico-chemical analysis of mineral paragenesis based on thermodynamics of natural systems with cmc (Table III). He paid special attention to composition-paragenesis diagrams and to diagrams plotted in co-ordinates of chemical potentials of completely mobile components. In this respect "the Korzhinsky's phases rule" expressing the dependence between the number of components and the number of phases in systems with cmc has become the practice. And the diagrams in chemical potentials co-ordinates has long been termed as"Korzhinsky's diagrams".

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Presently, a physico-chemical analysis of parageneses is a routine method employed in petrologic studies. The created theoretical foundation is sufficient for solving current problems, therefore the further elaboration of the theory and topology of diagrams, these invariably being exclusive studies of only a few specialists, has been slowed down. Meanwhile, the necessity of elaborating the universal theory and methodology for constructing general phase diagrams of multicomponetal systems from the data on individual concrete joins is absolutely clear. This necessitates studies concerned with higher--order diagram topology. Another serious problem is a numerical calculation of multicomponent diagrams in the co-ordinates of intensive parameters.

4. In the field of classic petrology problems solution, involving the understanding of processes of magmatism, D.S.Korzhinsky has introduced the principally new idea of magma as a system with completely mobile regime of alkalis, table IV. He has shown that parageneses and, consequently the order of crystallization of granitoid rocks are governed by chemical potential values of completely mobile potassium and sodium. The well-known Korzhinsky's diagram encompasses the largest number of paragenetic species of granitoid (in a broad sense-silica-rich) rocks to show, also, that the crystallization sequence, distinguished by N.Bowen (Bowen's crystallization series) is one of the particular cases of possible (depending on _K2O and _Na2O) paragenetic sequences. D.S.Korzhinsky has suggested the idea of transmagmatic solutions as solutions free to circulate in magmatic chambers which determine the character of the magma interaction with country rocks (infilting, diffusion-assisted substitution, acid-basic regime in magmatic chambers, etc).

Interestingly, that despite an active investigation of various problems of magmatism, concrete dynamic model of infiltration magmatic solutions has still some way to go. Among the principal present-day lines of research in the field of magmatism the following ones are to be mentioned.

Advances in a study of particular magmatic formations and their geodynamic position.

An experimental study of dry and hydrous magmatic systems, properties of magmatic melts and influence of redox conditions.

An investigation of the componental partitioning between melts and fluids.

An investigation of various problems related to the composition, structure, and melting of the upper mantle. The relationship between the mantle processes and crust magmatism.

Note - as the genius paradox - that never in his studies D.S.Korzhinsky was concerned with the problems of the mantle, this being despite the rush about the "mantle problem" in the sixties. I once asked Dmitry Sergeevich about it. He answered me in the parable. Once, in the Middle Ages, disciples of a great scientist (I guess he called him Gallileo but I am not sure) came running to him to say that a wonder horse of two heads has been brought to the local zoo. The wise man kept silent. "Aren't you excited indeed?!" the disciples cried in amazement. "Not at all. It does not interest me because just now it is incomprehensible" he answered.

Some principle directions have already surfaced. The problem of transmagmatic solutions is giving way to the general direction in theoretic and experimental study of the magmatism dynamics.

Magmas as the systems with cmc (experiment, numerical solutions) are one more problem.

Concrete (numerical) genetic models of magmatic formations are gaining particular importance. I should like to emphasize this fact because the situation is, roughly speaking, as follows: we know in the general form the physico-chemical conditions of formation of granites as a model abstract scheme, but we are not yet able to construct a complete numerical model of formation of particular multi-phase intrusive massif by solving all the problems of heat-mass transport and phase transitions in time and space. Although, the encouraging attempts are available.

5. In the year 1956 D.S.Korzhinsky suggested the concept of acidobasic evolution of magmatogenic solution is an alteration of their acidity (table V). A regular change in the acid-basic regime manifested in an increase of acidity of solutions, its inversion and an acidity decrease to follow was identified as the "acidity wave". Acidity increase is caused by the accumulation of acidic components in residual magmatogenic solutions and the "leading acidity wave" is due to the filtration effect manifesting itself in a more rapid filtration of acid components of the solution as compared with basic ones. Perhaps, none of the discoveries of D.S.Korzhinsky caused such an instantaneous response as the concept of acido-basic evolution of hydrothermal solutions. Many works appeared illustrating its validity by the example of concrete deposits. Experiments were run which confirmed the existence of the filtration effect and revealed its complicated nature or, to be more exact, its complicated multi-factor mechanism. This has given rise to a new domain, i.e. physico-chemical thermo- and hydrodynamics in fine-porous media but has done ill turn to the concept of filtration effect. Rather than experimentally determine the values of the filtration effect and, on this base, quantitatively estimate the scales of the acidobasic differentiation and the scales of the related mineralization in different hydrothermal deposits, the researchers turned their interests to the elucidation of the role of individual components of the filtration effect mechanism and, in general, to the complicated problems of thermodynamics and dynamics of solution in fine-porous media. Undoubtedly, many results were gained therefrom but characterizing of the geological role of the filtration effect was a long way to go.

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The problem of the filtration effect is therefore quite burning for investigators. It should be useful herewith to fill in the gap and to carry out researches in two lines: by continuing refined studies of physics and chemistry of solutions in fine-porous media and, concurrently, attempting on concrete models to estimate the geochemical role of the filtration effect.

It should also be mentioned that recently the attempts have been revived to divorce wall-rock metasomatism from mineralization and attribute the ore formation to influence of concentrated saline ore-bearing solutions. It is hardly possible here to compare and analyze these different concepts. The unbiased solution of this problem consists, in our opinion, in constructing alternative numerical models for the same particular ore objects.

6. The creation by D.S.Korzhinsky of the theory of metasomatic zoning is of paramount importance for physical geochemistry and geology as a whole (Table VI). Being incapable of even briefly listing here the numerous achievements of this theory, I shall mention only two most important statements. First- the theory of metasomatic zoning has given rise to the principally new understanding of the metasomatic processes radically differing from the existing ideas. Second- the creation of the theory is a brilliant example of abstract physico-chemical modeling. In creating the theory, D.S.Korzhinsky elaborated and clearly showed the methodology of this most universal method of physical geochemistry.

D.S.Korzhinsky's theory of metasomatic zoning has gained a brilliant versatile development. Petrologic and geochemical studies have been performed for all principal types of metasomatic formations. The new line - experimental modeling of metasomatism has been created. The principal types of ore metasomatites have been experimentally reproduced. The physico-chemcial parameters of their formation (T,P, fluid composition) numerical values, boundary conditions as well as the kinetic and dynamic parameters of some metasomatic processes have been experimentally determined. Finally, methods of numerical (computer) calculation of mineral-water solutions equilibria in the metasomatic columns zones have been worked out.

Experimental and computer modeling of metasomatism is a new qualitatively higher level in the development of the theory of metasomatic processes leading to their complete quantitative description. The development of the universal theory of metasomatism including joint solution of dynamic and equilibrium problems and numerical solution of genetic models of concrete objects will be the main avenue of investigations of metasomatism in the nearest future.

In conclusion I should like once again to express my deepest gratitude and admiration to the great scientist of our time Dmitry Sergeevich Korzhinsky.

Table I.

Table II.

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Table III.

Table IV.

Table V.

Table VI

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