ZONING AND FORMATION OF GROUNDWATER IN THE BELOVSKY DISTRICT OF KUZBASS

G. M. ROGOV

(Submitted by the Department of Hydrogeology and Engineering Geology)

In considering the exceptionally interesting and complex question of the zoning and formation of groundwater, the author has relied on the ideas of V. I. Vernadsky, F. P. Savarensky, G. N. Kamensky, A. M. Ovchinnikov, N. K. Ignatovich, N. I. Tolstikhin, and others.

In numerous works by these authors, the questions of the geographic, geological, and hydrogeochemical zoning of groundwater have been elucidated, and questions of its formation have been treated.

The study of the chemical and gas composition, temperature, regime of groundwater, and other characteristics, and the correlation of these features with the zonal influence of terrestrial factors, make it possible to establish a clear picture of the spatially regular changes in groundwater, to construct hydrogeological forecasts more definitely, and to resolve questions of the genesis of individual types of water.

Approaching from these positions the zoning and formation of groundwater in the Belovsky geological-economic district of Kuzbass, it appears possible to note the following regularities.

Within the district there is a clearly expressed vertical zoning of groundwater. In vertical section, three hydrogeochemical zones are developed, and the thickness of the zones and their hydrogeochemical characteristics are distinctive within the principal geostructural and geomorphological elements (the Salair Ridge, the Tyrgan Upland, and the Prisalair Depression).

The upper zone of hydrocarbonate-calcium waters, more rarely hydrocarbonate-sulfate-calcium waters, embraces the Quaternary formations and the upper, most weathered and water-saturated part of the Paleozoic deposits (marine, lagoonal-continental, and continental). The thickness of the zone varies. In the area of development of effusive-sedimentary formations of the Middle Cambrian, the thickness does not exceed 50 m; within the limestones of the Lower Cambrian, Devonian, and Lower Carboniferous it increases to 100–150 m. In the territory where coal-bearing deposits of the Carboniferous and Permian are developed, the thickness of the zone decreases to 50 and even 30 m.

The zone embraces the region of active water exchange and circulation and is characterized by the development predominantly of hydrocarbonate-calcium waters with mineralization of 0.2–0.7 g/l. The pH values of the groundwater are greater ...

mostly low (pH = 5.5–6.5), except in limestones, where they vary from 6.5 to 7.4, with an average value of 7.0.

For the majority of the springs, wells, and boreholes tested, the groundwater of this zone has been uncovered and characterized. Hydrogeochemical data for the upper zone for different geostructural and geomorphological areas are given in Table 1. In the easterly direction, as one passes from the Salair Ridge to the Cis-Salair depression, the mineralization of the water increases (from 0.27 to 0.7 g/l), the water type becomes noticeably more complex (Table 1), and the thickness of the zone decreases considerably.

In the groundwater of the upper zone, oxygen–nitrogen and oxygen–carbon-dioxide–nitrogen gases of atmospheric origin are dissolved.

Table 1

The second zone, of hydrocarbonate-sodium and sulfate-hydrocarbonate-sodium waters, encompasses the Paleozoic deposits. The thickness of the zone varies. In the Cis-Salair depression, in the area where coal-bearing deposits are developed, it is 150–200 m (boreholes 164, 319); on the Tyrgan Upland and within the Salair Ridge the thickness of the zone has not been established. However, the existence of this zone is confirmed by abundant factual material. In the territory where carbonate deposits are developed there are boreholes, wells, and springs in whose groundwater the sodium content reaches 43% equiv. (251, 64, 207, 98, 178, 161, 153, etc.).

In the area of development of lagoonal-continental deposits of the Balakhon series, groundwater of the second zone has been encountered at a depth of 40–60 m and is developed down to a depth of 200–250 m (boreholes 1240, 1–55, 1463, 1523, etc.). The chemical composition of groundwater from borehole 1523 is as follows:

\[ M_{1.0}\ \frac{\mathrm{HCO}_{3}^{?}\,\mathrm{SO}_{4}\,\mathrm{Cl}_{4}}{(\mathrm{Na}+\mathrm{K})_{33}\,\mathrm{Ca}_{35}\,\mathrm{Mg}_{22}} . \]

The second zone is most clearly distinguished in the Cis-Salair depression. There is a large number of boreholes, wells, and mine workings that have penetrated and established the zone of development of hydrocarbonate-sodium waters. In boreholes 86, 145, 148, 93, 312, 319, wells 162, 89, 194, and in min—

workings, sharply expressed waters of the second zone have been uncovered. The composition of the waters may be illustrated by the following Kurlov formulas:

borehole 319, tested interval 45–100 m,

\[ M_{0.98}\ \frac{\mathrm{HCO}_3^{\,3}{}_{73}\mathrm{Cl}_{16}\mathrm{SO}_4^{\,4}{}_{11}} {(\mathrm{Na}+\mathrm{K})_{93}\mathrm{Ca}_{4}\mathrm{Mg}_{3}} ; \]

borehole 164, interval 86–108 m,

\[ M_{1.2}\ \frac{\mathrm{HCO}_3^{\,3}{}_{69}\mathrm{Cl}_{30}\mathrm{SO}_4^{\,4}{}_{1}} {(\mathrm{Na}+\mathrm{K})_{79}\mathrm{Ca}_{13}\mathrm{Mg}_{8}} ; \]

the Chertinskaya Yuzhnaya mine, depth 100 m,

\[ M_{0.9}\ \frac{\mathrm{HCO}_3^{\,3}{}_{5}\mathrm{SO}_4^{\,6}\mathrm{CO}_3^{\,3}{}_{5}\mathrm{Cl}_{1}} {(\mathrm{Na}+\mathrm{K})_{91}\mathrm{Mg}_{8}\mathrm{Ca}_{1}}\ \mathrm{pH}\,8.3; \]

the Babanakovskaya mine, depth 150 m,

\[ M_{0.82}\ \frac{\mathrm{HCO}_3^{\,3}{}_{81}\mathrm{Cl}_{8}\mathrm{SO}_4^{\,6}\mathrm{CO}_3^{\,3}{}_{5}} {(\mathrm{Na}+\mathrm{K})_{78}\mathrm{Ca}_{14}\mathrm{Mg}_{8}}\ \mathrm{pH}\,7.0. \]

The mineralization of groundwater of the second zone varies from 0.5 to 3.0 g/l; pH values range from 6 to 8.5. The lower boundary of the second zone is established by the replacement of bicarbonate-sodium waters by chloride-sodium waters. A noticeable increase in chlorine content with depth is observed at all tested points that uncovered groundwater of the second zone. Thus, in borehole 164 at the Chertinskoye deposit, the lower boundary of the second zone was noted at a depth of 108–120 m.

The third hydrogeochemical zone of chloride-sodium waters has been poorly studied. There is almost no information on the degree of water abundance of Paleozoic rocks and on the chemical composition of groundwater at deep horizons. However, individual data indicate the existence of brackish sulfate and chloride waters.

In borehole 164 at the Chertinskoye deposit, in the interval 108–230 m, chloride-sodium waters of the following composition were encountered:

\[ M_{1.4}\ \frac{\mathrm{Cl}_{57}\mathrm{HCO}_3^{\,3}{}_{43}} {(\mathrm{Na}+\mathrm{K})_{93}\mathrm{Mg}_{4}\mathrm{Ca}_{3}} . \]

Within the Belovo deposit (Ivanovsky sector), the methane content in this zone is 18 m³ per ton of coal (Erofeev, report at a meeting of the Siberian Branch of the USSR Academy of Sciences, April 1959).

In borehole 116-K (Barzas district) [1], in Devonian deposits at great depth (834–906 m), chloride-sodium waters were also encountered, nitrogenous with methane and heavy hydrocarbons. Water composition:

\[ \mathrm{N}_{2}\,83\ \mathrm{CH}_{4}\,15\ \mathrm{C}_{n}\mathrm{H}_{2n+2}\,1.3\ \mathrm{He}\,0.097\quad M_{3.0}\ \frac{\mathrm{Cl}\,90\,\mathrm{HCO}_3^{\,3}{}_{7}} {\mathrm{Na}\,96\,\mathrm{Ca}\,3}. \]

In the area of development of lagoonal-continental deposits, groundwater of the third zone is characterized by an increased sulfate content (up to 43% equiv., boreholes 1463, 1500, 1510).

Thus, within the district three hydrogeochemical zones are developed. The first (upper) zone consists of fresh bicarbonate-calcium waters; the second zone, of bicarbonate-sodium waters; and the third zone, of weakly mineralized waters of chloride-sodium and sulfate-chloride-calcium-sodium composition.

The present zonal distribution of groundwater of different composition was determined as the result of the long history of paleohydrogeological development of the district. At the present time, as a result of a prolonged and intensive process of weathering, leaching of rocks, water exchange, and mixing of groundwaters of different sedimentary complexes, the groundwater has undergone considerable metamorphism and is due pri—

predominantly infiltration processes. Although, as the research materials show, geological complexes and even individual strata (formations) within complexes have to a considerable extent preserved specific hydrogeochemical features and create distinctive conditions for the formation of groundwater [4].

The available materials show that only the upper zone of bicarbonate-calcium waters, formed through the infiltration of atmospheric precipitation and circulating in the zone of active water exchange, in the area of leached rocks, has a “homogeneous” genesis. The groundwater of the second and third zones has a complex genesis, due to the fact that the geological complexes at these depths have proved to be less leached, are in a later stage of development, and more strongly reflect the primary salt composition of the rocks. The degree of leaching of the rocks and the conditions of groundwater formation differ within the main geostructural and geomorphological areas (the Salair Ridge, the Tyrgan Upland, and the Cis-Salair Depression). Whereas on the territory of the Salair Ridge and the Tyrgan Upland (recharge areas) there are favorable conditions for the infiltration of atmospheric precipitation and the formation of leaching groundwater, over a considerable part of the Cis-Salair Depression (areas of development and partial discharge of groundwater) conditions of a stagnant regime and the formation of groundwater of continental salinization are observed.

In the formation of groundwater on the Salair Ridge and the Tyrgan Upland, the leading factors are: infiltration of atmospheric precipitation and leaching of rocks. The small thickness of loose deposits, increased fracturing, and locally karstified rocks, as well as the high degree of leaching of the rocks, favor the formation of infiltration waters with low mineralization. Within these geomorphological elements, the mineralization of groundwater in the zone of intensive water exchange does not exceed 0.3–0.6 g/l; the groundwater contains oxygen-nitrogen and oxygen-carbon dioxide-nitrogen gases of atmospheric origin. For the area of development of carbonate rocks, bicarbonate-calcium waters are characteristic in the upper zone, passing at deeper horizons into bicarbonate-sodium waters. In this territory, readily soluble chlorides and other compounds in the upper zone have been completely removed, and at present slow leaching of sparingly soluble carbonate compounds is taking place. As a result, bicarbonate waters with low mineralization are formed.

Within the area of development of effusive-sedimentary formations, bicarbonate, sulfate, and chloride waters occur, caused by complex processes of leaching of marine deposits with sulfides of iron, copper, zinc, lead, etc. (the Salair sulfide-ore deposits). In the oxidation zone of the sulfide deposits of Salair, sulfate waters with a high content of heavy metals in the waters are formed. In exposed and barren areas, bicarbonate waters with low mineralization are formed. In separate depressions, owing to the poor leaching of effusive-sedimentary formations, chloride waters with increased mineralization (up to 1.5 g/l) occur, resulting from leaching of the chloride salt complex of the rocks.

On the territory of the Bachatsk and Krasnobrodsk deposits, the sulfate waters of individual areas are associated with oxidation and leaching of coal-bearing deposits with inclusions of pyrite. The groundwater of these areas is characterized by increased metal content.

Thus, the slope of the Salair Ridge and the Tyrgan Upland are an area of distribution of groundwater of leaching and constitute a belt of intensive chemical removal occurring in the process of weathering and leaching of rocks.

Groundwater of continental salinization is characteristic of individual parts of the Prisalair Depression. Under conditions of a considerable thickness of loose deposits, weak natural drainage, and comparatively high evaporation, an environment is created that is not very favorable for underground runoff. In such areas [2], as the concentration of salts dissolved in the water increases and the less soluble salts gradually precipitate out of the solution—first calcium and magnesium carbonates, then calcium sulfates—a favorable setting is created for the accumulation of chloride salts, which, being the most soluble, remain in solution, increasing their concentration. The groundwater gradually becomes chloride water as salinization proceeds.

The hydrogeochemical process of formation of chloride waters is well illustrated in the transition from the Tyrgan Upland to the Prisalair Depression, especially in the northern part of the district. The bicarbonate waters of the Tyrgan Upland, with mineralization of 0.3–0.6 g/l, are replaced in the Prisalair Depression by chloride waters with mineralization up to 3.0 g/l. It should be noted that the setting for the formation of groundwater of continental salinization in the Quaternary period apparently changed greatly. It may be assumed that the most favorable conditions existed during the period of formation of loess-like loams, and it is quite possible that in individual areas we encounter conditions that were determined at that time.

In the Prisalair Depression, drained areas with a sharply different composition of groundwater are observed along river valleys. In these areas, surface and underground runoff increases, and the processes of infiltration and leaching intensify. As a result, the mineralization of groundwater decreases to 0.5–0.9 g/l, and the composition of the waters changes to bicarbonate or sulfate.

In the formation of the chemical composition of groundwater in deeper horizons, the leading factor is cation exchange. In the process of physicochemical interaction of infiltration waters with rocks, additional dissolution of salts and cation exchange with the colloidal part of the rocks take place.

Calcium ions in the infiltration water, in the process of exchange adsorption, are replaced by sodium ions absorbed by the rocks, and the released sodium ions pass into solution. As a result, bicarbonate–sodium waters of the second zone are formed, with mineralization of 1.0–3.0 g/l.

In deeper horizons, chloride–sodium waters are formed, likewise caused by processes of salt dissolution and cation exchange of groundwater with the colloidal part of the rocks. A clear example of the change in the composition of groundwater with depth—in particular, the increase in sodium chloride content—is provided by interval sampling data from borehole 164, located at the Chertinskoe deposit. Thus, in borehole 164, at a depth down to 80 m, the mineralization of groundwater was 0.88 g/l, with a chloride-ion content of 48 mg/l and sodium ion of 178 mg/l; in the interval 110–231 m it increased to 1.7 g/l, while the chloride-ion content rose to 616 mg/l and the sodium ion to 680 mg/l. A rapid increase in groundwater mineralization with depth, and an increase in chlorine and sodium content, is traced in all deep boreholes.

The noted features of the zonality and formation of groundwater are of great not only scientific but also practical significance. אויס

Elucidation of the regularities of recharge, formation of the salt composition, movement, and discharge of groundwater makes it possible to plan correctly and solve problems of water supply for industrial facilities, and to make fuller use of local groundwater resources.

REFERENCES

1. Belyakova E. E. Materials on the hydrogeology and gas-bearing capacity of the northeastern part of Kuzbass. Materials on the geology, hydrogeology, and oil-and-gas-bearing capacity of Western Siberia. Proceedings of VSEGEI, 1954.

2. Kamensky G. N. Problems of the formation of groundwater. Proceedings of the Laboratory of Hydrogeological Problems, vol. XVI, 1958.

3. Ovchinnikov A. M. Fundamentals of the doctrine of the processes of groundwater formation. News of Higher Educational Institutions, 1, 1958.

4. Rogov G. M. Some problems of the hydrochemistry of groundwater in the Belovsky district of Kuzbass. Bulletin of the West Siberian and Novosibirsk Geological Administrations, No. 3, 1959.