LIMESTONES OF THE KAMENSKOYE DEPOSIT—VALUABLE RAW MATERIAL FOR THE LIME AND CEMENT INDUSTRY OF THE CITY OF TOMSK

P. G. Usov and S. S. Ilyenok

Carbonate rocks are a valuable mineral resource for the developing industry of Siberia. They are rather rarely occurring rocks within the middle belt of the West Siberian Lowland. Therefore, a characterization of the petrographic and chemical compositions, as well as of the physical properties, of the limestones of the Kamenskoye deposit is undoubtedly of great practical interest.

The limestone deposit is located on the left bank of the small Shcherbak River, near the village of Kamen, Aleksandrovsky Village Soviet, Tugansky District, Tomsk Region.

The deposit area lies in a well-settled district, 46 km east of the city of Tomsk and 27 km from the Mezheninovka railway station.

Limestone outcrops extend from the village of Kamen in northwestern and northern directions for 20 km, with interruptions in the exposures. In the northern part of the district they crop out along the Toshma River near the village of Podlomskoye, which is located on the highway 54 km from the city of Tomsk. Thus, the reserves of the deposit are large, and the deposit itself is situated under favorable economic conditions, which will facilitate its rapid development.

The value of the deposit is further increased by the fact that, together with the limestones, red clays occur in the studied area; together with the limestones, they constitute an excellent material for the synthesis of silicate cement.

Brief Geological Characterization of the Deposit

The limestones form part of a Devonian belt of rocks of northeastern, almost meridional strike (Fig. 1). The abundant fauna of corals and bryozoans in the limestones, processed and studied by the paleontological laboratory of WSGU, determines the Middle Devonian age of these rocks. The apparent thickness of the limestones over the area reaches 300 m, but the true thickness is about 150 m. To the west these rocks are replaced by a widespread, thin, red-colored sequence of sandstones and conglomerates. The age of this sequence has tentatively been assigned to the lower part of the Upper Devonian. The sequence is capped by limestone-marly deposits about 40–50 m thick, having an age of \(D_3—C\). Between the overlying thick deposits of the Permocarboniferous \((C_3—P)\) and the limestone-marly deposits, a small horizon of Ostrog sandstones and conglomerates is observed, consisting of fragments of siliceous rocks.

Schematic geological map of the area of the Kamenskoye limestone deposit.
After M. I. Odin.

Legend:

• Ancient metamorphic complex: Gnt–gα–Gnt (?)
• Erosional–Pliocene formation: T₃²–D₁ (?): loose deposits, siltstones, etc. with diabases and porphyrites. Limestones D₂.
• Multicolored sequence D₃ (?)
• Limestone–marl sequence D₃–C₁
• Sandstones and conglomerates C₁ (Ostrog beds horizon)
• Permo-Carboniferous (C₃–P)
• Meso-Cenozoic (Mz–Pg)
• Elements of bedding
• Lines of tectonic disturbances

Map labels visible include: toward Tomsk; Mankovo; Sinyakovsky; Rozhkovsky; Kolyvansky; Kandevka; Polomskoye; Turuntaevo; Kholdeyevo; Georgievsky; Sergeevsky; Suetilovsky; B. Orlovka; r. M. Ushayka; Blinovsky; Kolbikha; r. Kolbikha; Berezovka; Sukhorechye; Urbei; Kamen; N. Petrovka; N. Rozhdestvenkov; Aleksandrovka; r. Shcherbak; Romanov; r. Kargaza; r. Tashma; Dubovaya; Kondak; Osinovaya; Tashma.

Fig. 1

Plan of the Kamensk limestone deposit.

Legend:

• Outcrop and its number.
• Trench and its number.
• Pit and its number. Numbers of samples taken and designation of serial samples.
• Borehole and its number. Depth of borehole.
• Clay exploration area.
• Place where a clay sample was taken for granulometric and chemical analysis.

Fig. 2

To the west, the Kamenskoye limestones are replaced by the underlying effusive-tuffaceous rocks of the upper Lower Devonian. The Devonian and Permo-Carboniferous rocks are gathered into large folds of north-northeastern strike, overturned to the east. The dips of the fold limbs are steep, reaching 70–90°. Younger zones of bedding-plane slips are also encountered, apparently coeval with the “Tomsk thrust,” with vertical or steeply dipping fractures.

One disturbance of this type occurs along the Shcherbak River, 5 km above the village of Kamen. It has a strike of NE—45° and coincides with the direction of the Osinovaya River. Another disturbance in the northern part of the area, with a NE—50° strike, coincides with the strike of the Berezovaya River. The limestones were studied in greatest detail north of the village of Kamen, on the left side of the Shcherbak River. Here trenching and drilling operations were carried out (see Fig. 2).

Brief Petrographic Characterization of the Limestones

The bulk of the rocks studied in the deposit is represented by pure limestones, more or less recrystallized. The metamorphism of the limestone to the state of a fine-grained, dark-gray rock with uniformly disseminated bituminous matter is connected with the processes of regional folding. Later stress and the development of bedding-plane slips of NE strike led to crushing of the rock and to its more complete recrystallization, with local migration of bituminous matter and lightening of the rock. In addition to limestone, silty calcareous-clayey shales were also discovered. Petrographically, several varieties of limestone occur in the area; they differ in the degree of recrystallization, primary structure, and compositional features.

A sample of crystalline limestone No. 298 from borehole No. 4, from a depth of 4.5 m, is macroscopically a mottled, light-gray, medium-grained rock; it consists of pure calcite stained along thin subparallel fractures by brown ironstone.

The microscope shows a homeoblastic texture. Large grains of calcite, having the character of porphyroblasts, are situated among a silty and fine-grained calcite mass. The rock is cut by numerous thin calcite veinlets. One pseudomorph of limonite after pyrite was encountered. Thin, winding cracks along the boundaries of calcite grains contain limonite formed at the expense of pyrite. A sharply expressed recrystallization of the limestone is characteristic, apparently under unilateral pressure, with replacement by a dense system of subparallel calcite veinlets (Fig. 3).

A sample of bituminous crystalline limestone No. 366 from borehole No. 4, from a depth of 20 m, is macroscopically a gray, medium-crystalline-grained rock, broken by numerous threadlike veinlets intersecting it in different directions and containing black carbonized bituminous matter. Recrystallization of the rock is sharply expressed. The microscope shows an uneven crystalline-granular texture. The bituminous matter migrated, concentrating along the boundaries between calcite grains. A noticeable accumulation of carbonaceous-bituminous matter appears in the form of veinlets having a fantastically sinuous character (Fig. 4).

The rock is cut by a very dense, fine network of calcite veinlets, which are earlier than the veinlets of carbonaceous-bituminous matter, since they are intersected by the latter. A sample of brecciated fragmental crystalline limestone No. 159 from exposure XV. Here we

Fig. 3. Sharply expressed recrystallization of the limestone under one-sided pressure, with replacement of a dense system of subparallel calcite veins. Magn. 10. Nic. X.

Fig. 4. Veinlets of carbonaceous-bituminous matter (black) cut through a dense network of earlier calcite veinlets. Magn. 10. Nic. X.

we have a yellowish-gray crystalline-granular rock with grain sizes from 0.5 to 2 mm, rarely up to 4–5 mm in diameter. It consists of calcite, the aggregate of whose grains is broken by irregular cracks, along which the calcite is impregnated with brown limonite. On the weathered surface the rock is covered with a thin crust of yellow hydrous iron oxides. The microscope reveals the fragmental structure of the rock. The fragments are more often rounded and more rarely subangular (Fig. 5).

Along with isometric fragments, very elongated forms of fragments are encountered. In view of the low hardness of the limestone, this may indicate that they were formed in place or under conditions of insignificant transport.

Fig. 5. Fragments of limestone and of the skeletons of calcareous organisms, surrounded by a rim of silty calcite, deformed and cut by a dense system of veinlets. Magnification 10. Nic. X

Fig. 6. Whole calcite crystals surrounded by a rim of a thin silty gray aggregate of the same mineral

In Fig. 6:
1 — crystalline granular mass of calcite
2 — silty mass of calcite
vein of calcite

All the fragments consist of calcite. More often they are composed of whole calcite crystals, surrounded by a rim of a thin silty gray aggregate of the same mineral (Fig. 6).

The crystals in the inner part of the fragments are strongly deformed, have a parallel, polysynthetically twinned structure and, more often, a parallel dense system of cleavage cracks. The width of the rim of silty calcite varies, and in places the fragments are composed entirely of such a thin silty aggregate. The origin of the latter, which is in general not infrequently encountered in fragmental limestones, is not entirely clear, as is evident from the literature. It seems to us that its association with grain boundaries and the uneven thickness of such rims indicate, rather, their connection with cataclastic processes. The cement between the fragments is disorderly crystalline-granular. Within the cement there are spots of carbonate impregnated with brown iron ore. The presence in these areas of idiomorphic, rhombohedral grains most likely indicates the presence of decomposed ferruginous carbonate. Both the fragments and the cement are cut by numerous calcite veinlets. The appearance of these veinlets is pre-

there was strong crushing of the rock, with bending of calcite crystals.

Samples of organogenic-sludge limestone: No. 212 from trench IV, No. 78 from trench 1, No. 388 from borehole 2, No. 172 from excavation VIII,

Fig. 7. Organogenic-sludge structure of limestone. Magnification 10. Nic. X.

No. 107 from trench III, etc. Macroscopically, the rocks have a gray coloration, are weakly bituminous, and in the main mass are fine- and finely grained. In sample No. 78, among the fine-grained mass, calcite grains up to 1—1.5 mm in diameter are scattered; in other samples, larger

Fig. 8. Character of calcareous organic fragments in sample 212

grains, which are fragments of organogenic limestone, reach 2—3 mm. A concentration of coaly-bituminous matter is observed along cracks. In many samples of the rock we see isolated small spots of brown iron ore, confined to decomposed ferrous carbonate.

Under the microscope an organogenic-sludge structure is observed. The fragments of calcareous skeletons of organisms are highly varied. Most of all, here we have fragments of bryozoans and corals. Interestingly,

that the fragments are recrystallized better than the silty cementing material. Large fragments with an organogenic coral structure are sometimes encountered, occupying almost the entire field of the thin section (Fig. 13).

Fig. 9. Various organic remains, including coral fragments, in limestone.
Magn. 10. Nic. X.

Fig. 10. Character of organic remains in sample 78

Alongside samples in which fragments in contact with one another predominate, rocks with a basal silty cement are encountered (sample No. 388 from borehole No. 2) (Fig. 14).

Fig. 11. Organogenic-silty structure of limestone. Sample No. 5.

Fig. 12. Large fragments of calcareous organisms in calcareous mud. Magn. 10. Nic. X.

Fig. 13. Coral-organogenic structure of limestone. Magn. 12. Nic. X.

Fig. 14. Clastic-organogenic structure of the limestone. Organic remains and limestone fragments are recrystallized into large calcite crystals. A network of secondary calcite veinlets is visible. Magnification 10. Nic. X.

Fig. 15. Rare quartz grains (black) in limestone with abundant organic remains. Magnification 10. Nic. X.

In this case, fragments with an organogenic structure or without one are usually recrystallized into whole large crystals of calcite.

In specimen 411, microlamination is observed; individual laminae are filled with fragments of crystalline limestone. In specimens 66, 107, and 43, quartz occurs among the calcite aggregate in an amount of less than 1% by area. The quartz crystals are idiomorphic and are usually observed in groups of 2–3 grains (Fig. 15).

Inclusions of calcite occur within skeletal quartz grains. The quartz grains show no traces of rounding and undoubtedly formed through collective crystallization of silica during the general recrystallization of the rock.

Specimen 272 shows the presence of clayey limestone among the fragments. The content of clayey admixture is insignificant. In areas of more considerable recrystallization of calcite, the clayey material is concentrated in the form of lumps, chiefly along grain margins and along the cleavage of the mineral.

All the above-described rocks are cut by a dense network of calcite veinlets. In some areas the rock (specimen 428) is, as it were, leafed out, dissected by parallel cracks along which it has recrystallized into a coarse-grained aggregate. Calcite veinlets of two generations, intersecting one another, occur. The veinlets contain an admixture of decomposed brown ferruginous carbonate (specimens 407 and 411). In specimen 411, lens-shaped segregations of the latter are cut by calcite veinlets.

In specimen 411 of fine-grained organogenic-sludge limestone, with weak development of carbonate veinlets, intense cataclasis is observed. Recrystallization of the rock is noticeable along abundant subparallel cracks. There are transitions to areas of limestone with the most complete recrystallization. These are light-gray, medium-grained rocks. Under the microscope, an uneven granular structure is observed (Fig. 16).

The calcite grains that make up the main mass of the rock have uneven boundaries and are characterized by the presence of abundant polysynthetic twins and, in places, by noticeable bending of the grains. The rock is cut by small veinlets of the same mineral.

In one trench, aleuritic calcareous-clayey shales were encountered locally (specimen 253 from trench 32). These macroscopically gray, dense, thinly laminated rocks are cut by abundant calcite veinlets. Rare disseminations of pyrite are observed. The microscope shows a laminated texture. Within the calcareous-clayey brown mass, small angular and rounded quartz fragments and rare flakes of sericite are observed (Fig. 17).

When etched with weak, dilute hydrochloric acid, vigorous effervescence is observed with dissolution of the lime. After etching, a continuous (without windows) clayey mass remains, with a denser distribution of small quartz fragments, which constitute about 15% of the rock composition. Along the bedding of the rock are small cubic crystals of pyrite, almost entirely replaced by brown ironstone.

In conclusion to this brief review of the petrographic composition of the limestone sequence along the Shcherbak River, with the exception of the last rock, which has the composition of an aleuritic calcareous-clayey shale, all the other formations are detrital, organogenic-sludge limestones, recrystallized to a greater or lesser degree. The rocks are characterized by appreciable bituminosity, but owing to recrystallization they become lighter in color as a result of migration of the bituminous material to the boundaries between calcite grains and with the formation of fanciful veinlets. The limestones are pure and contain, in places, an insignificant admix-

an admixture of clayey matter (sample 272), quartz (samples 68, 107, 43), decomposed ferruginous carbonate, and limonite (samples 159, 43, 338, 78, 107, 5, 298).

In addition to the predominant fragments of calcareous organisms, chiefly bryozoans and corals, fragments of “structureless” limestone are observed. All fragments are immersed in a cementing material of fine calcareous mud.

Fig. 16. Crystalline-granular limestone. The most complete form of recrystallization. Magn. 10. Nic. X.

Recrystallization of the rock is manifested in an interesting way. The fragmental material undergoes this process more readily than the mud. Many fragments

Fig. 17. Bedded aleuritic calcareous-clayey shale with calcite veinlets, sample No. 253. Magn. 10. Nic. X.

limestone and organic remains are replaced by large calcite crystals. With the most complete recrystallization, a uniformly and medium-grained crystalline rock is formed, in which organic remains disappear or are only weakly noticeable (specimen 68).

One can trace gradual transitions from weakly metamorphosed limestones to crystalline limestones. In the very process of recrystallization of limestones, at least two stages can be distinguished.

1. A sharp manifestation of unilateral pressure (stress): crushing of the rock and recrystallization with the formation of a network of calcite veinlets.

2. Recrystallization with a noticeable rise in temperature. Owing to this—the migration of bitumen, its carbonization, and the formation of veinlets of carbonaceous-bituminous matter cutting the network of earlier calcite veinlets.

The crushing of the rock and its recrystallization are sometimes very sharply expressed. For example, in specimen 298 about 50% of the rock volume is replaced by a dense system of subparallel calcite veinlets. The material of these veinlets appeared at the expense of the rock itself. This is evident from the fact that recrystallization begins from the walls of the cracks. An admixture of terrigenous material in the aleuritic calcareous-clayey shale, in the form of rounded and angular fragments of quartz, was noted above. The presence of quartz alone among the fragments and the absence of feldspars indicate that the clastic material underwent prolonged mechanical differentiation, or that it is connected with the washing away of a chemical weathering crust.

Finally, it should be noted that organogenic-silty limestones are typical of transitional horizons. Apparently, here they characterize a horizon transitional from the Middle to the Upper Devonian.

Chemical Composition of the Limestones

The high degree of purity of the limestones is confirmed by chemical analyses and by thermal investigation according to Kurnakov. Of the total number of chemically investigated samples taken from the deposit, only six were found to contain MgO at slightly more than one percent (sample No. 375—1.04%; sample No. 378—1.01%; sample No. 281—1.08%; sample No. 417—1.10%; sample No. 440—1.27% and sample No. 441—1.94%).

In 20% of the samples the MgO content lies within the limits of 0.5–1.0%, and in the remaining samples it is less than 0.5%. They have a low percentage of admixtures of clayey substances (insoluble residue). An insoluble-residue content in amounts up to 2% was established in samples comprising 71% of the total number of investigated samples.

In amounts from 2 to 8%—in 26% of the samples, and in amounts above 8%—in 3% of the samples.

The number of samples containing more than 3% insoluble residue is 9% of the total number of samples subjected to chemical investigation; among them, 4% of the samples belong to a small area of the site located at the boundary margin, and 1.5% of the samples are from greater depths in boreholes Nos. 1 and 4.

The chemical composition of the limestones is presented graphically in Fig. 18.

Thus, by chemical composition, in the absolute majority of samples, the limestones of the Kamenskoye deposit belong to class “A” (GOST 5331—50) and are fully suitable for obtaining fat air, hydraulic, and highly hydraulic lime. A small part belongs to class “B”—suitable for obtaining ordinary air lime. Varieties containing admixtures of clayey substances greater than 8% are concentrated at one point of the explored area, and in the production of lime they can quite well be bypassed. With regard to the use of limestones for

... for the synthesis of silicate cement they are, undoubtedly, suitable, and by their MgO content they belong to group “A.”

The thermal investigation according to Kurnakov was carried out on three identified varieties of limestone:

1) light-gray in color,
2) gray in color, and
3) black in color.

The thermal curves are given in Fig. 19.

Fig. 18

In all three varieties the presence of humic substances is detected, but they are contained in considerably larger quantities in the gray and black limestones (samples 256 and 254). In the black limestone (sample 254) a slight kaolin effect is recorded, as well as some unknown effect associated with decomposition at a temperature of 250°C.

Fig. 19

In these same limestones, the endothermic reaction caused by the decomposition of carbonates begins at lower temperatures than in light-gray and gray limestones. The latter indicates the presence in the black limestones of small amounts of magnesium carbonate and admixtures of clayey substances, which lower the decomposition temperature of calcium carbonate.

Red brick clays of the same deposit

As already indicated at the beginning, directly on the explored area of the limestone deposit there occur red brick clays. They cover the limestones in part of the area with a bed up to 13.5 m thick. Laboratory investigations of these clays were carried out mainly in order to establish the possibility of using them as raw material for the synthesis of silicate cement.

Table 1

Grain-size composition of the clays

Table 2

Chemical composition of the clays

Clays have a comparatively fine physical structure and contain absolutely no inclusions of pebbles or coarse-grained sand. In grain-size composition they are suitable for the manufacture of silicate cement.

The chemical composition of all varieties of clays fully meets the requirements for clays for the synthesis of silicate cement. They contain permissible amounts of MgO and contain no minerals at all that would adversely affect the quality of silicate cement. The white clays of samples No. 446 and 447 are suitable for the manufacture of white cement. The chemical compositions of the remaining clays vary within narrow limits, which is very important in cement production.

Limestones as Raw Material for Air Lime

Of decisive importance in assessing limestones for the production of lime is the content in them of impurities of clayey substances \((\mathrm{SiO_2} + \mathrm{R_2O_3})\). In raw material for rich air lime, up to 2% of these is permissible; for ordinary air lime, from 2 to 6%; and for lean air lime, from 6 to 8%. In terms of composition, the most suitable for producing air lime are limestones with a coefficient \(K\) from 1.70 to 1.78, where

\[ K = \frac{100}{\mathrm{CaO} + \mathrm{MgO} + \mathrm{SiO_2} + \mathrm{R_2O_3}} \]

(the oxide content is taken in percent from the limestone analysis).

In testing for lime, limestones of all three identified varieties were studied, with the following characteristics.

Table 3

In terms of mechanical indicators, all three varieties of limestone are quite suitable for processing into lime in shaft kilns. During the study, the firing of limestones into lime was carried out in a gas-fired kiln at a temperature of 1000–1050°C, with a four-hour holding period. In external appearance and in fracture, complete decomposition of the carbonate with the formation of CaO was readily observed.

The chemical composition of the lime obtained is given in Table 4.

Table 4

In chemical composition, the lime from all three limestones is calcic (or non-magnesian) air lime with a high slaking rate (quick-slaking), shown in Table 5.

Table 5

Limestones of all three varieties, when burned, form lime with a good yield of lime paste and with a complete absence of unslaked residue in the gray and light-gray limestones. In terms of the yield of lime paste, the lime from the light-gray limestone belongs to the first grade, and that from the gray and black limestones—to the second. In terms of the amount of unslaked residue, the lime of all three samples is of the first grade.

The content of active CaO + MgO in the lime from black limestones is 82.12%. In the lime from gray and light-gray limestones it is 90.16% and 92.96%. Thus, in terms of the content of active CaO + MgO, the lime from light-gray and gray limestones is of the first grade, and the lime from black limestones—of the second.

As a result of the analysis we arrive at the conclusion: by all the principal indicators, limestones of the gray and light-gray varieties, when burned, produce lime of the first grade, and limestones of the black variety—of the second grade.

Limestones and clays as raw material for silicate cement

Harmful impurities in limestone for the production of silicate cement are: MgO, P₂O₅, SO₃, and alkalis; therefore the content of these oxides in the initial raw material is limited. The content of MgO in limestone is permitted up to 2.5%, and together with the clay component they must make up such a mixture in which MgO would not exceed 4.5%.

“The content of SiO₂, Al₂O₃, and Fe₂O₃ in the limestone and in the clay component must ensure the necessary values of the saturation coefficient (0.80–0.95), the silicate modulus (1.7–3.5), and the alumina modulus (1.0–2.5) of the clinker.” S. S. Vinogradov, Limestones, publ. 1951, p. 51.

The content of R₂O₃ and SO₃ is recommended to be allowed at no more than one percent each.

The chemical composition of samples of limestones and clay from the Kamenskoye deposit, with which technological investigations were conducted in the laboratory, is given in Table 6.

Table 6

In synthesizing experimental compositions of silicate cement with a saturation coefficient \(KH = 0.9\), clinker of the following chemical and mineralogical composition is formed (Table 7).

Table 7

Note: Sₘ is the silica modulus and Aₘ is the alumina modulus.

As can be seen from Table 7, the obtained compositions of cements from all three limestones are in full agreement with the usual compositions of silicate cements. In the laboratory, clinker was prepared from briquetted raw mixes. The preliminarily ground limestones were mixed by weight batching with clay, and the raw mixes were ground in a ball mill until they passed completely through a sieve of 900 openings/cm².

The ground raw mixes were briquetted by plastic molding and, after drying, were burned to clinker.

The binding of lime as a function of the firing temperature is given in Table 8.

Table 8

The clinker from all three raw mixes, after firing at 1500°C with a 30-minute holding period at the high temperature, proved to be completely stable; after four days of aging, no signs of disintegration were detected in it.

The clinkers were ground in a ball mill until they passed completely through a sieve of 4900 openings/cm². The characteristics of the cements obtained are given in Table 9.

We also studied the physicomechanical properties of the limestones of the deposit. The intention was to use them as a building material (rubble stone and road stone, etc.). We believe that it is inadvisable to use these limestones as rubble and road stone. Such chemically pure limestones are not often found in nature, and they should be used in the most rational manner.

Table 9

Conclusions

All varieties of limestone from the Kamenskoye deposit are excellent raw material for the production of air lime. Together with the clays of the same deposit, they are also suitable for the production of silicate cement.

Literature

1. Vinogradov S. S. Limestones, State Geological Publishing House, 1951.
2. Yung V. N. Fundamentals of the Technology of Binding Materials, Promstroiizdat, 1951.
3. Grigoriev P. N. and Kuznetsov A. M. Lime, Its Production and Use, Stroiizdat, 1944.