Toward a Characterization of Coals from the Upper Part of the Section of the Baydaevskoye Deposit in the Kuzbass

A. A. Kurbatova

The Baydaevskoye deposit in the Kuzbass is a large brachysynclinal structure filled with coal-bearing deposits of the Erunakovo suite, whose thickness is 1300 m [3].

The section of the deposit contains up to 45 coal seams, of which 35 are workable; the latter have been numbered, their ordinal numbers increasing from bottom to top.

The coal seams of the Erunakovo suite are, as a rule, complex. Usually they are of small thickness (1.5–2 m), and only some of them, belonging to the stratigraphically upper horizons of the section, reach a thickness of 3–5 meters (thus seam 29a has a thickness of 3.5 m; seam 32—3.24 m; seam 37—5.41 m; seam 38—4.13 m).

The coals of the Baydaevskoye deposit have been studied by a number of persons (O. F. Gracheva and Z. V. Ergolskaya [2], A. A. Larishchev [5], L. I. Bogolyubova, V. S. Yablokov, and L. P. Nefed’eva [7]), but the upper coal seams have until now remained unstudied.

Interest in studying the coals of the upper part of the section was prompted not only by the fact that it contains the thickest seams, but also by the fact that these upper seams behave unusually with respect to the yield of volatile matter ($V^{\mathrm{g}}_{\mathrm{cp}}$). The yield of volatiles regularly increases from bottom to top only up to seam 30, reaching 40.6%. Beginning with seam 31 and above, however, the yield of volatiles does not increase, as one would expect according to Hilt’s law, but gradually decreases, reaching in seam 38 (the uppermost) 36.6%.

In the course of studying the material collected by us (1954–1956), the very same types and varieties of coal were found that had earlier been distinguished and described by V. S. Yablokov and L. I. Bogolyubova (1951) (see Table I). But for the stratigraphically upper part of the section it proved necessary to distinguish two new varieties, transitional in character between the semibright and semidull types. They are characteristic of coal seams only in the upper part of the section and have not been encountered in the underlying strata. A characterization of these new varieties is given below.

Variety 9. Semidull striated, transitional to semibright.

The variety is represented by banded coal consisting of dull and bright bands. The dull bands consist of dense, slightly striated durain coal. The bright bands are represented by vitrain-clarain. Dull interlayers predominate.

Microscopically, this variety consists of typical spore durain containing thin interlayers of vitrain.

Table 1

The durain bands are enriched with bright-yellow microspores; megaspores are encountered less often. These bands consist mainly of areas of opaque groundmass. There is so much of the latter that the transparent groundmass plays a subordinate role: its thin, capriciously curved, sometimes threadlike, sometimes broader bands seem to adapt themselves to the predominant opaque areas. Lenses of fusain and xylain are present in noticeable quantity, often with well-preserved cells.

Mineral impurities are not numerous and are represented by small grains of quartz, less often by grains of feldspar and occasionally by carbonates. The admixture of clayey matter is also insignificant. Very thin bright bands consist more often of structural vitrain, less often are represented by clarain.

The quantitative content of microcomponents in the coal of this variety is as follows:

vitrainized matter — 50.0%
opaque matter — 33.6%
cutinized elements — 3.0%
fusain — 5.5%
xylain — 3.0%
mineral impurities — 5.0%

On the basis of this composition, this variety may be termed semidull durain coal. This coal occurs in seams Nos. 36, 38 (Fig. 1).

Variety 10: transitional from semibright to semidull mineralized.

This variety of coal is rather distinctive; it has been encountered only in seam No. 29a (Baidaevskaya mine). The coal is very strong, dense, mineralized, containing small lenses of vitrainized matter.

In polished sections, a strongly kneaded mineralized coal of the type of highly ash-bearing durain-clarain is observed. The kneading of the coal is expressed in the crushing of individual areas of coal and the displacement of their fragments relative to one another. The crushed coal mass is cemented by siliceous-carbonate material.

The durain-clarain areas contain a noticeable quantity of micro-

spores, lenses and bands of opaque matter, as well as lenses of fusain and xylain. These lenses may be mineralized, and the amount of mineralized fusain regularly increases in the direction from the floor of the seam to the roof. Among the mineral impurities in the coal mass there occur quartz grains and small flakes of mica.

[Figure]

Fig. 1. Petrographic sections of coal seams of the Baydaevskoye deposit. Varieties of coal: 1—bright, indistinctly banded; 2—bright, banded; 3—semibright, banded; 4—semibright, indistinctly banded; 5—from semibright to semidull, mineralized; 6—semidull, streaky; 7—semidull, streaky, grading into semibright. Rocks: 8—interbedding of argillite with coal; 9—argillite; 10—fusain.

Visible labels in the figure: seam No. 29, thickness 4.5 m; seam No. 30, thickness 2.0 m; seam No. 32, thickness 3.0 m; seam No. 33, thickness 2.0 m; seam No. 34, thickness 0.35 m; seam No. 35, thickness 1.0 m; seam No. 36, thickness 1.5 m; seam No. 37, thickness 1.25 m; seam No. 38, thickness 4.5 m. Scale: 20, 0, 20, 40, 60 cm.

The quantitative ratios of the microcomponents in this variety are as follows:

The above contents of microcomponents make it possible to call this variety a coal transitional from semibright to semidull, ash-rich coal of the durain–clarain type.

In studying the coal seams, quantitative counts were made on briquette polished sections prepared from middle-seam samples that had been crushed and cemented with shellac. The briquette polished sections were studied at high magnifications (×630–×840), using oil immersion. Counts were made of vitrain-like matter, fusa-

Table 2

Percentage content of varieties in seams 29–38 of the Baidaevskoye deposit
(southwestern limb)

fuseno-xylenic components, cutinized elements, areas of opaque matter, and mineral impurities. A continuous section was studied along both limbs of the deposit from seam 14 to seam 38. From the lower part of the section, only seams No. 1 and 2 were studied. The results of this study are as follows.

The group of lower seams (seams 1, 2) contains varieties of bright homogeneous and semibright homogeneous coal. Nowhere higher in the section were these varieties encountered. The content of vitrinite-like matter in these seams reaches 95%, whereas the content of fusain-like matter in them does not exceed 1.8%.

The group of middle seams of the section (seams 14–26) is characterized by a lower content of vitrinite-like matter (mainly within the range of 80–85%, rarely 90%); however, the quantitative content of fusain-like matter gradually increases from bottom to top, reaching up to-

5–7%. These seams contain approximately equal amounts of bright and semibright varieties.

In the group of upper seams, along with the predominance of semibright varieties, semidull varieties also appear in appreciable amounts. In Fig. 1 petrographic sections of these seams are given for the southwestern limb. Table 1 gives the percentage content of the varieties for this group of seams.

The content of vitrain-like material in these seams decreases to 66–70%, whereas the amount of fusain-like material increases considerably and reaches 20.0%.

To illustrate the above, we give the following figures for the percentage content of fusain-like material in several seams.

All that has been said above makes it possible to note: a) enrichment of the seams from bottom to top with semibright and semidull types; b) a gradual quantitative increase in them (from bottom to top) of fusain-like material; c) a quantitative increase of fusain-like material in the seams in the direction from SW to NE of the deposit.

The accumulation of plant material at this deposit took place under lake–swamp conditions. During the formation of the lower part of the Erunakovskaya suite, more stable and quiet conditions for the formation of peat deposits existed than later. Bright and semibright homogeneous coals indicate considerable flooding of the swamps and more or less uniform conditions of peat accumulation. The coals of the deposit are autochthonous in origin.

The upper horizons of the suite differ substantially in the composition of the coal seams from the lower horizons. The predominance of semibright types and the presence of semidull types enriched in fusain-like material indicate less waterlogged swamps, in which repeated drying (and consequently oxidation) of the decomposition products was observed.

Within the homogeneous main mass of coal there is a very noticeable number of areas of opaque material, as well as an increase, from bottom to top in the section, in fusain lenses and interbeds. The coals become dureno-clarain and clarain-durene, and are enriched with dull interbeds. The latter indicate the intrusion of flowing waters into the area of the peat bog and the contamination of the latter with clastic material. Thus, if facies of strongly waterlogged swamps are characteristic of the lower parts of the section, then facies of “dry” swamps are more probable for the upper parts of the section [6].

In order to obtain additional material for judging the nature of the coals, we carried out a partial palynological analysis of several seams of the section. It turned out that the predominant role in the spore-pollen complexes belongs to spores of ferns with a trilete aperture. In all the studied seams of the upper

in the section, cordaite pollen is present, the maximum amount of which is observed in seam 33. Higher up (from seam 33 to seam 38) the amount of cordaite pollen drops sharply, and in seam 38 it is represented by isolated grains.

Spores of horsetails and lycopods are present in small quantities. Ginkgo and cycad pollen is fairly common in the assemblages; its amount increases upward through the section. Worth noting is the almost complete absence of conifer pollen, which, as is known, is common in Permian deposits of various countries and regions, including the Kuzbass in particular [1]. But in the upper coal seams of the Baidaevskoe deposit, conifer pollen is present literally as isolated grains, and even then not in all samples.

The latter is an interesting feature of the coal-bearing deposits characterized at this deposit and points to certain special conditions that were unfavorable for conifers, but favored the wide development of cordaites and ferns.

The important role of cordaites in the formation of the coal seams of the deposit is evidenced by their microcomposition: whole interlayers of woody durain occur in the coals; for example, in seam 33 such interlayers consist of excellently preserved wood formed by tracheids with bordered pores of the araucarioid type. This wood is very similar to the cordaite wood of the Kuzbass described by M. D. Zalesskii. Many tissues of the same type also occur in the maceration products of these coals; the latter was noted earlier by A. A. Larishev [5].

The coals of the Baidaevskoe deposit are formed chiefly from tissues of higher plants and by their nature are humic; no sapropelic material has been found in them by us.

Microspores occur in all varieties; upward through the section there appear macrospores and whole accumulations of microspores—fragments of sporangia. Cuticles are comparatively few (if compared, for example, with the Leninsk deposit). Resin bodies occur, the number of which increases slightly upward through the section (in seam 38 there are more of them than in the others).

In summary, on the basis of the observations set out above, the following conclusions may be drawn.

The coals of the Baidaevskoe deposit, humic in their nature and autochthonous in terms of accumulation conditions, form seams whose thickness increases upward through the section and decreases from west to east and northeast. In the same directions there is a noticeable increase in the content of semi-dull and semi-bright types of coal, as well as in the content of fusain-like substance in them (and, consequently, a decrease in the content of vitrain-like substance).

Such a change in the petrographic composition of the coals upward through the section is apparently also the reason for the decrease in the yield of volatile matter in seams 31 to 38.

The increase in the content of fusain-like substance in the coals studied to as much as 20% is undoubtedly very high (in the Leninsk coals it is 4–5%, rarely up to 10%), but not exceptional for the coals of the Erunakovskaya suite. An increase in the content of semi-bright types of coal and of fusain-like substance in them was noted by us for the coals of the Chertinsk deposit [4]; an increase in the content of semi-bright and semi-dull durain varieties was noted by Z. V. Ergolskaya and G. N. Radchenko in the coals of the Erunakovskoe deposit.

The coals of the lower and middle parts of the section formed under conditions of strongly waterlogged bogs, and the coals of the upper part under conditions of “dry” bogs, where intensified oxidation of the original material was observed. An abundance

in the latter, woody material at the stage of fusenization gives these coals a semi-lustrous or semi-dull appearance and reduces the yield of volatiles.

CITED LITERATURE

1. Andreeva E. M. Spore-and-pollen characterization of the Balakhonka and Erunakovskaya suites of the Kuzbass. Atlas of index forms of Permian deposits of the Kuzbass. Gosgeoltekhizdat. 1956.

2. Gracheva O. F. and Ergolskaya Z. V. Petrographic characterization of the coals of the Baidaevskoye deposit of the Kuzbass. Manuscript. Archives of the Kuzbassuglegeologiya Trust. 1938.

3. Kostamanov G. M. and coauthors. The Baidaevskie Eastern 1–2–3 sectors of the Baidaevsky district of the Kuzbass. Archives of the Kuzbassuglegeologiya Trust. 1950.

4. Kurbatova A. A. Petrographic composition and nature of the coals of the Chertinsky and Belovo-Babanakovsky deposits of the Kuzbass. Proceedings of Tomsk State University, vol. 132. 1954.

5. Larishchev A. A. Petrographic characterization of coals from the lower part of the Baidaevskaya brachysyncline of the Novo-Osinovskoye deposit of the Kuzbass. Proceedings of Tomsk State University, vol. 93. 1938.

6. Nefed’eva L. P. Application of facies analysis in the study of coal seams. Proceedings of the Laboratory of Coal Geology, issue VI. 1956.

7. Yablokov V. S., Bogolyubova L. I., Nefed’eva L. P. Structure of coal seams and types of coals of the Erunakovskaya suite of the Kuzbass. Proceedings of the Institute of Geological Sciences, issue 136, coal series, No. 3, 1951.

Tomsk Polytechnic Institute
named after S. M. Kirov