DEVELOPMENT OF HYDROGEOCHEMICAL RESEARCH AT TPI

P. A. UDODOV, N. M. RASSKAZOV, S. L. SHVARTSEV

The development of science in recent times shows that some questions in geology require serious corrections. This is especially acutely felt with regard to natural waters, toward which attitudes had become very simplified. Many propositions of scientists concerning groundwater were speculative in character. Meanwhile, the role of groundwater in many geological processes is decisive. This is what Academician V. I. Vernadsky wrote about it: “Water, forming as a whole one of the Earth’s geospheres—the hydrosphere—determines the entire chemistry of the Earth’s crust in the area accessible to our direct study. Chemical reactions proceed chiefly in aqueous solutions, liquid or vaporous, and the properties of solutions determine to a great extent the genesis of vadose and phreatic minerals. They also determine the environment of life.”

No less great is the role of groundwater in the formation of mineral deposits. In the works of Academicians V. I. Vernadsky and A. E. Fersman, the fundamental possibility was shown of using groundwater for prospecting purposes. However, the development of this question was hindered by the absence of reliable and sufficiently sensitive methods for analyzing groundwater. Therefore, in 1951, at TPI, the Department of Hydrogeology was given the task of developing a method for determining microcomponents in natural waters applicable to field conditions. The Department of Analytical Chemistry was brought into this work, which made it possible already in 1952 for I. I. Onufrienok and P. A. Udodov to propose a fundamentally new method of analysis based on the coprecipitation of microcomponents with aluminum hydroxide. Testing of the method under field conditions showed its reliability and sufficient sensitivity. Somewhat later, the technique of spectral analysis of the obtained aqueous concentrates was also improved, which made it possible simultaneously to determine in one sample, under field conditions, more than 40 chemical elements. The developed method of analysis, under the name “TPI method,” became widely disseminated in the USSR and abroad and gave impetus to the development of other analogous methods. At present, there are several such methods of analysis in the Union.

The development of a method for studying the chemical composition of groundwater enabled TPI staff to begin systematic investigations of the conditions governing the formation of aqueous dispersion flows in zones of mineralization. At approximately the same time, similar work was begun at the All-Union

at the Research Geological Institute, Leningrad University, the All-Union Research Institute of Hydrogeology and Engineering Geology, the Geological Institute of the Academy of Sciences of the Armenian SSR, and a number of scientific organizations of the Academy of Sciences of the USSR.

At TPI during this period, studies were carried out to determine the conditions for applying the hydrogeochemical prospecting method in various landscape zones and geological settings. Particular attention was paid to such hard-to-reach areas as high-mountain regions, areas with the development of permafrost rocks, swampy areas, and others. At the same time, ever new types of mineral deposits were included in the study. If, at the first stage, the study of aqueous dispersion streams was carried out only around sulfide deposits, as those most susceptible to destruction under conditions of the hypergene zone, then, beginning in 1957, deposits of rare and dispersed elements were included in the research.

The study of the conditions of formation of aqueous dispersion streams is unthinkable without clarifying the role of individual factors in the migration of chemical elements in groundwater. Therefore, at TPI this work was begun already at the first stage of the research. As a result of these studies, the important role of the activity of rocks in the migration of chemical elements was demonstrated and a method for determining it was developed, which received wide recognition in the Union; individual aspects of the influence of the sorption capacity of rocks on the migration of chemical elements in waters were clarified; a methodology was developed for regime observations in hydrogeochemical prospecting and for using the results in interpreting the data obtained; a coefficient was proposed for determining the migrational capacity of chemical elements; and several other questions were resolved.

As a result of hydrogeochemical studies it became clear that the enrichment of groundwater with heavy metals also occurs under conditions of a reducing geochemical environment, where oxidation reactions are impossible, which required clarification of the nature of the processes taking place there. As a result of experimental work by N. M. Rasskazov, it was shown that, at arsenic deposits, in the enrichment of groundwater with heavy metals under conditions of a reducing geochemical environment, the decisive role is played by processes of electrochemical dissolution, previously known for sulfide deposits. At the same time, for this same purpose, the study of the isotopic composition of groundwater was begun.

The broad scope of research on the development of the hydrogeochemical prospecting method made it possible, already in 1960, to hold at TPI the first All-Union conference on this question, and in 1962 to publish the proceedings of this conference and the first monograph, Experience of Hydrogeochemical Studies in Siberia. The authors of this monograph—P. A. Udodov, I. P. Onufrienok, and Yu. S. Parilov—were the first in the Union to summarize the results of the development of the hydrogeochemical prospecting method and the results of its introduction into production. This monograph played an important role in the broad introduction of the method into the practice of geological prospecting work, which was reflected in the corresponding resolutions of the Ministry of Geology of the USSR and in the “Instructions on Geochemical Dissolution, Previously Known for Sulfide Deposits” in 1965.

The broad introduction of the method into production required an expansion of work on developing searches for so-called “blind” ore bodies, which is one of the most important modern tasks of geology as a whole. Therefore, beginning in 1963, the Problem Geological Laboratory was completely switched over to the development of these questions.

The object selected for study was the Kolyvan–Tomsk buried folded zone. This region, located in the center of the industrial part of Western Siberia, remained very poorly studied because visual research methods did not yield positive results owing to the thick cover of loose deposits. Hydrogeochemical investigations in this region demonstrated its potential for polymetallic and other mineral resources and made it possible to clarify a number of interesting points that help in detecting concealed ore bodies. In particular, P. A. Udodov and V. M. Magusevich developed a method for tracing zones of tectonic disturbances from hydrogeochemical data, which is important in mapping covered territories. The results of these works have now been transferred to geological organizations and summarized in the form of two monographs, one of which was published in 1965 and the second in 1971.

Thus, within the limits of a large region, the great penetration depth of this prospecting method was confirmed, which makes it the most effective in comparison with other geochemical methods.

The development of a methodology for prospecting for “blind” ore bodies required a more in-depth study of the migration of chemical elements not only in underground waters, but also in soils and plants, which play an exceptional role in the redistribution of chemical elements in the biosphere. This work in the problem geological laboratory was begun as early as 1962. The results of these studies were partly transferred to the Tomsk state farm, since they help in evaluating soil fertility. In connection with these works, the need arose for a detailed study of the role of soil organic matter, in particular humates, in the migration of chemical elements under specific conditions. The idea that organic matter plays an exceptionally large role in the behavior of many metals had been expressed earlier by some scholars; however, up to now this question remains unstudied. In the problem laboratory, R. S. Solodovnikova and others developed a method for isolating humates from various natural objects, provided their electron-microscopic description, and compiled an atlas of these photographs.

Humates of various metals have diverse forms; however, in neutral, slightly alkaline, and alkaline media they possess a common structural feature—a leaf-like form, which changes from humate to humate depending on the metal (Fig. 1). These figures show electron-microscopic photographs of natural humates isolated from natural waters, peat, soils, and rocks.

The results of these studies confirm:

1. The presence of compounds of metal humates under natural conditions.

2. Electron-microscopic photographs give some idea of the arrangement of particles of metal humates and make it possible to judge them as compounds with a definite particle form characteristic only of this type of compound.

3. They make it possible to suppose which of the metal ions under natural conditions are in combination with natural organic matter, which is of great importance in interpreting the results of field hydrogeochemical investigations.

Thus, as a result of many years of research at TPI, a methodology of hydrogeochemical prospecting has been developed, including field studies, methods for analyzing underground waters, interpretation of the results of work, and evaluation of the anomalies detected, with broad use of methods of mathematical statistics. This methodology, in the form of a separate work, has been transferred to the Ministry of Geology of the USSR for introduction into production. The results of hydrogeochemical investigations at TPI

in the form of separate monographs, maps, diagrams, and models, were demonstrated at VDNKh in 1965 and at Soviet exhibitions abroad.

It should be noted that the development of the hydrogeochemical method of prospecting at TPI has been carried out from the very first days in close cooperation with production organizations. This makes it possible to introduce the results of research directly into production and increases the effectiveness of geological-prospecting work.

It is precisely because of this that, as a result of hydrogeochemical work and verification of the anomalies identified by the scientific staff of the problem laboratory, the Department of Hydrogeology, and their students, the following ore deposits and ore occurrences have been discovered: copper-nickel in the area of the city of Norilsk, polymetallic in Rudny Altai and the Kolyvan-Tomsk folded zone, molybdenum in the Kuznetsk Alatau, and others.

Fig. 1. Electron-microscopic photographs:
a — dry residue of the initial manganese salt solution MnCl₂; b — synthesized manganese humate; c — natural manganese humate, isolated from zircon-ilmenite sand; d — natural manganese humate, isolated from travertine with microcomponent composition Ba—0.03%; Mn—0.5%; C—1.25%

In parallel with the development of the hydrogeochemical prospecting method, TPI was the first in the Union to begin training specialists in this field, who are currently working in various production and scientific organizations of the country. This, in turn, required the creation of specialized courses in hydrogeochemistry.

Almost all the issues discussed above relate chiefly to prospecting hydrogeochemistry. Meanwhile, work experience shows that the hydrogeochemical method can produce a very great production effect not only in geological-prospecting investigations, but also in the exploration and exploitation of mineral deposits. We distinguish the stage of hydrogeochemical investigations during exploration work as exploration hydrogeochemistry. Using the results of hydrogeochemical investigations, it is possible to considerably reduce the volume of costly exploration and mining work, shorten the time required to develop a deposit, and greatly ease labor during exploitation. However, the methodology of field and laboratory work, as well as the interpretation of the data obtained, are still very poorly developed.

Research in this direction has not yet gone beyond the stage of methodological development. It is being carried out by various organizations of the Ministry of Geology, institutes of the Academy of Sciences of the USSR, and higher educational institutions.

The staff of the problem geological laboratory of the Tomsk Polytechnic Institute are successfully carrying out similar work at the Baranovsk polymetallic ore occurrence. This ore occurrence still remains the most interesting within the Kolyvan-Tomsk folded zone. The decisive role in its discovery was played by prospecting hydrogeochemical investigations performed by TPI staff.

Drilling and exploration work carried out within the area of the identified hydrogeochemical anomaly revealed lead-zinc mineralization. However, a full assessment of the scale of mineralization was not obtained by these works. Naturally, the further direction of exploration work should be based on taking into account all geological and geochemical features of the area. Hydrogeochemical investigations, which at this stage of assessing the area are regarded as detailed, should occupy a leading position. This is due to the fact that the area of the ore occurrence is characterized by the development of a thick cover of loose deposits, and the methods usually employed in exploration practice here either do not justify themselves or are costly.

For the purpose of expanding the prospects of the Baranovsk ore occurrence and determining the sites for drilling boreholes that would give the greatest effect in its exploration, detailed hydrogeochemical work was carried out. In the course of the latter, the zonality of aqueous dispersion flows and their spatial relationship to ore mineralization were studied, and their extent relative to the ore zone was also determined.

Along with this, the role of the processes of chemical oxidation and electrochemical dissolution in the vertical and horizontal zonality of the mineralization zone was established.

Considerable attention was given to the formation of salt halos in soils and in the weathering crust, as well as to the study of pore solutions. At the same time, the influence of microbiological processes on the enrichment of waters with microcomponents was clarified.

In the course of processing the materials, correlation relationships were established between the principal ore-forming elements and indicator elements in aqueous dispersion flows, in the mineralization zone, in the primary halo, and in loose formations.

To clarify the regularities in the formation and development of aqueous dispersion flows within the Baranovsk ore occurrence, in addition to the extensive use of hydrogeochemical methods in combination with others (lithochemical, biogeochemical, etc.), the following special studies were carried out: study of secondary formations of the oxidation zone and newly formed minerals at groundwater discharge points; sampling of core, sludge, drilling fluid, and groundwater in boreholes; regime observations at springs; study of transitional forms of sulfur in natural waters; determination of Eh and pH, the gas and isotopic composition of waters, organic matter and microflora, and specific elements in natural waters.

Based on the results of investigations in the Baranovsk area, hydrogeochemical maps, profiles, and graphs were compiled, taking into account the modulus of groundwater runoff, chemical removal of microcomponents, the migration coefficient, the regime correction coefficient, spectral analyses of rocks, groundwater, sludge, and other geochemical data. The results obtained made it possible to refine the projected mineralization zone and to design, on a geologically substantiated basis, the scope of exploration work. Research in the field of exploration hydrogeochemistry undoubtedly deserves further development.

At present, the further development of hydrogeochemical investigations is being outlined, with the goal of exploiting ore deposits by the hydrobiochemical method. Academician A. A. Imshenetskii writes: “Scientists believed that geological processes caused by microbes proceed extremely slowly and that it is unrealistic to subordinate them to the will and reason of man. However, research in recent years has refuted this notion.” In connection with this new direction

...research, a microbiological laboratory was organized at TPI in 1962.

A turning point in the introduction of geological microbiology into the practice of hydrogeochemical research in our country may be considered the publication of the work by S. I. Kuznetsov, M. V. Ivanov, and N. N. Lyalikova, Introduction to Geological Microbiology. This book, as the authors quite rightly note, sets itself the task of determining the role of microorganisms in geological processes and establishing the principal ways of controlling their geological activity.

The experience of our studies within the area of the Kolyvan–Tomsk folded zone has shown that microorganisms must be studied both in soils and rocks and in various types of natural waters. Only with such a comprehensive approach does it appear possible to study the different environments of microorganism life activity.

The line of research we have adopted corresponds to B. B. Polynov’s observation that “...the composition of natural river waters is determined not by simple abiotic reactions of water acting on minerals of igneous rocks, i.e., by hydrolysis and dissolution, as is devised in textbooks, but by a more complex, although more rapidly proceeding, process of extraction of elements from minerals by organisms and dissolution in water of the ash fraction of organisms during their mineralization.”

In regional hydrogeochemical investigations within the area of the Kolyvan–Tomsk zone, we sampled a large number of different types of waters. However, our attention was concentrated mainly on the study of microorganisms in groundwater associated with rocks of the weathering crust of sandy-argillaceous shales. These rocks are characterized by a bluish-gray color, caused by the presence of organic matter, finely disseminated iron sulfides, and chlorite in the cement. The presence, according to our analyses, of siderite and pyrite in them indicates the predominantly reducing environment that existed in the silt waters. Subsequent geological processes were expressed in folding and hydrothermal activity, which led to mineralization of the rocks and the washing out from them of marine sedimentation waters and, apparently, the burial of waters of infiltration type.

In studying groundwater in individual areas, we encountered specific types of waters characterized by a low pH value (1.4–1.5), high mineralization (152–166 g/l), and, in chemical composition, sulfate-ferruginous. The content of ferrous iron reaches 12.8 g/l and ferric iron 35.9 g/l, sulfate ion 117.6 g/l, chlorine 0.039 g/l, and organic matter, \(C_{\text{total}}\), 0.573 g/l. The organic matter was studied in the TPI laboratory by R. S. Solodovnikova from electron-microscopic photographs. The water under study, according to V. G. Ivanov, is characterized by an increased deuterium content (\(+1.9\gamma\)). Such a content is usually characteristic of groundwater of sedimentation origin or capillary condensation. Further study of these waters, with the formulation of experimental work, will make it possible to clarify this question. Analysis of the microcomponent composition of the waters described showed thousandths of a percent of Mn, Zn, Ni, Cr, Ba, Co, Cu.

These waters, moreover, were studied by V. A. Shamolin in the microbiological laboratory of TPI with respect to the composition of the microflora and its influence on the enrichment of waters with heavy metals. The microbiological composition of the waters under study has so far been studied extremely little. However, in our opinion, the microflora of this type of water may provide the most important and complete picture of the participation of bacteria in geochemical processes.

Studies of the bacteria of these waters may make it possible to assess in a new way the role of the biological factor in geochemical changes of rocks in the hypergenesis zone, and also help in the discovery of new species of microorganisms participating in these processes. If these assumptions are confirmed, it will apparently become possible to speak specifically of the predominantly biogenic character of the formation of the microcomponent composition of groundwater according to the following scheme: bacteria of the waters under study, acting upon the rock, transfer various compounds into the pore solution, from which the latter then enter the free filtration water.

When the culture of the waters characterized above is examined microscopically, according to V. A. Shamolin, short immobile rods about \(2 \times 0.7\ \mu\) in size are observed, sometimes of irregular form, often joined into groups and surrounded by a mucilaginous formation. Morphologically, this microorganism differs from most of the described species of thionic bacteria. All this, as well as their confinement to a poorly studied habitat, makes it possible to suppose that this culture may be either a new species of bacteria or an as yet unknown modification of already described microorganisms of the thionic group, greatly altered under specific habitat conditions.

Of course, these assumptions still require the most careful verification through further isolation and study of a pure culture. This culture was used in experiments with sulfide ores of zinc, mercury, copper, and lead. Laboratory experiments were carried out with these ores in which the ores were flooded with a nutrient medium without the addition of iron. Thus, the bacteria were forced to use this element directly from the mineral. The results of one of the experiments are presented in Table 1.

The bacterial emulsion was introduced only after 40 days. During all this time the process of metal leaching proceeded only by chemical means. After 35 days of bacterial action on the ores, 2–3 orders of magnitude more metal passed into solution than during oxidation without microbes.

As can be seen from Table 1, almost all the principal components of the ores pass into solution. The exception is mercury. Apparently, the concentration of mercury compounds taken has a toxic effect on the bacteria.

The promise of the hydrobiochemical method lies chiefly in the fact that, as studies abroad and in the USSR have shown, it can be applied to the extraction of many metals and rare elements and to the beneficiation of various concentrates. Its high economic efficiency is beyond doubt.

All the questions discussed above are being used in the development of a whole series of theoretical propositions of hydrogeochemistry, which has been developing rapidly in recent years. This development is to a significant degree due to the introduction of hydrogeochemical investigations into the practice of geological work by various organizations, including Tomsk Polytechnic Institute.

On the other hand, the enormous role of natural waters in all geological processes is becoming ever more deeply understood. At the same time, much attention is being paid not only to their composition, but also to their structural features.

Thus, in the opinion of A. M. Blokh, “one should expect that the model of liquid water of M. Eigen and the conclusions arising from it can be successfully used for solving many geological problems.”

There is no doubt that the further development of work in the field of hydrogeochemistry will contribute to a more complete disclosure of the principal geological regularities and to their use in solving practical problems.

Table 1

Oxidation of sulfide ores depending on the presence of bacteria