CLASSIFICATION OF PALEOZOIC COAL-ACCUMULATION AREAS OF KUZBASS BY STRUCTURAL-TECTONIC FEATURES AND SOME ISSUES OF THEIR EXPLORATION

V. Ya. Koudelny, Yu. N. Popov, P. I. Sherin

(Presented by the seminar of the Department of Geology and Exploration of Mineral Deposits)

The role of tectonics in solving many problems of exploration and exploitation of coal deposits is well known. It increases substantially in connection with the expanded use of mechanized methods for driving mine workings, and with the comprehensive mechanization and automation of mining operations. The increase in the volume of the principal type of coal-exploration work—mechanical core drilling—has led neither to a substantial increase in reserves of high categories, nor to an improvement in the technical and economic indices of construction and operation of mines and open pits at deposits being developed by the coal industry [6].

The revealed incompleteness in the study of the tectonics of coal deposits makes it necessary to introduce certain changes into the methodology of its investigation. Such changes can be made more correctly and with better justification on the basis of studying and generalizing materials of mine geological services and materials on large coal areas characterized by a common origin and development of various structural forms. A number of organizations of the USSR Ministry of Geology are carrying out thematic work in this direction as applied to various basins.

In Kuzbass, where tectonics is characterized by particular complexity and diversity, much attention has been given to questions of tectonic study since the classic investigations of M. A. Usov. In recent years, special thematic studies on the tectonics of mine fields have been carried out. Some results of these studies are given below, and possible ways of using them in conducting exploration are indicated.

One of the important but still unresolved questions in the exploration of coal deposits is the question of classifying them, for uniform exploration methods, according to structural-tectonic features. In all generalized groupings recommended at various times by the instructions of the VKZ and GKZ, three groups have been distinguished according to tectonic complexity. Practice has shown that these groupings are too schematic and cannot encompass the entire diversity of coal deposits.

In Kuzbass a more detailed classification of deposits has been created [7]. Unfortunately, here the type of deposit has been unsuccessfully adopted as the classification unit, while the classification criteria make it possible only to characterize morphological features—

structures. For these reasons, in practice it is difficult to assign a given exploration area to one of the subtypes in the classification of E. M. Pakha and E. M. Senderzon, especially if one takes into account that the complexity of the structure of different areas of one and the same deposit often also proves to be different.

The practice of conducting geological exploration work urgently requires the creation of a new classification with the broadest possible use of materials on the tectonics of mine fields obtained during mining operations and exploration of new areas of the basin.

The Kuznetsk Basin is characterized by a very great diversity of genetic and morphological types of folded and fault structures. This is due mainly to its geotectonic position. The latter has not yet been definitively clarified and gives rise to different points of view. The reasons for this are also certain features of the tectonics of the basin.

First of all, one should note the distinctive arrangement of the outcrops at the surface of the deposits of the suites in ascending stratigraphic order, in the form of concentric belts from the periphery toward the center of the basin, which resulted from the considerable uplift of the ancient structures surrounding it. The boundaries of the basin, with the possible exception of the boundary with the Kuznetsk Alatau, depended on these uplifts and denudation processes. The strike of the suites is generally parallel to the outlines of the basin.

A second feature of the tectonics of the basin is that the intense structures observed in immediate proximity to the Salair and to the Kolyvan–Tomsk folded arc become simpler toward the center of the basin, being replaced by gentle brachysynclines and, finally, by monoclinal zones near the southeastern and eastern margins of Kuzbass. Structural asymmetry is accompanied by asymmetry in the lithological and facies composition of the rocks, coal-bearing capacity, and metamorphism.

A further feature of the tectonics of the basin is that the tectonic structures of its different parts formed as a result of movements that differed in the mobility and degree of consolidation of the adjacent, more ancient mountain structures. The influence of the latter on the formation of the structures of Kuzbass is varied. The time of consolidation of these structures and folded systems has not been definitively established, and this creates major difficulties in determining the paleotectonic nature of Kuzbass and its geotectonic position.

Recognizing the manifestation of various phases of tectogenesis in Kuzbass, it should be noted that, all other conditions being equal, tectonic complexity increases with increasing age of the rocks. This feature of the basin’s tectonics is expressed in the fact that at present, for the coal-bearing deposits, only two structural stages are distinguished, determined by the manifestation of the pre-Cimmerian and Neo-Cimmerian phases of tectogenesis. The possibility is not excluded that other phases also had a considerable influence on the formation of tectonic structures, in particular the Saalian, Pfalzian, and younger phases. In any case, within the western and northwestern structures of Kuzbass the Jurassic deposits proved to be more dislocated than had previously been assumed.

A very important feature of the tectonics of Kuzbass is the block structure of its basement. The blocks differed from one another in their mobility both during the formation of the coal-bearing deposits and during subsequent tectonic reorganizations. Moreover, a detailed analysis of sediment thicknesses, coal-bearing capacity, and the degree of diagenetic transformations of coal and enclosing rocks shows that the mobility of individual parts of the blocks was far from identical. This indi-

...exerted an influence both on the complexity of the structures within individual blocks and on the coal content and coal quality.

All these features, taken into account to varying degrees, have been reflected in schemes for the regionalization of Kuzbass [1, 5, 8]. It seems to us that they should also form the basis for a classification of Kuzbass areas according to structural-tectonic criteria for unified methods of exploration. The difficulty of using them for these purposes follows from differing views on the tectonic nature of Kuzbass.

In accordance with one or another interpretation of the tectonic position of the basin, views also change regarding the causes of its distinctive features. Researchers’ ideas about the tectonics of Kuzbass largely coincide, and this makes it possible to create a classification of coal-accumulation areas on fundamentally new foundations. This is all the more possible if one takes into account that schemes of tectonic regionalization generally correctly reflect the presence of various large tectonic forms and their distribution.

Before proceeding to set out the new classification, it is necessary to agree on the main classification unit and on the features laid at the basis of the classification.

Experience shows that neither a deposit nor a mine field can be accepted as the classification unit. Analysis of the variability of structural settings in the deposits and mine fields of Kuzbass shows that the classification unit may be an area with a combination of basic structural elements characterized by definite morphological and genetic features that influence the density of the exploration network and the choice of development systems. In individual cases this combination of elements may occur within the limits of an entire deposit. In other cases, even within a field, it may be sharply different. The proposed classification unit makes it possible to take into account the consistency and closeness of the connection between various structural elements in areas of different size.

The main classification criteria, in our opinion, should be the genetic and morphological features of the structures, as well as their influence on the conduct of exploration and mining operations. It is precisely the combination of structures that creates the diversity of structural settings and often the extremely complex conditions for exploration and exploitation.

In existing classifications, the genesis of structures is either completely ignored or taken into account insufficiently fully and consistently. In the process of exploration, the forms of tectonostructures are usually established and characterized in their present form. At the same time, chiefly their external features are analyzed and evaluated. Meanwhile, knowledge of the regularities in the development of tectonic structures makes it possible to determine their morphological types more correctly, which in itself is extremely important. In addition, connected with the development of structures are also regularities in the variation of the thicknesses of deposits and coal seams, the number and persistence of the latter, the distances between seams, metamorphism, and coal quality. It is not difficult to see that all these are factors influencing the methodology of geological exploration work and should be studied more fully when it is carried out.

It must be acknowledged that the genesis of the structures of Kuzbass has not been fully clarified. All the structures have a multiphase development. The role and significance of individual phases—moreover, phases that have not been sufficiently clearly distinguished—in the formation of structures are far from identical; but what is presently known about the genesis of the structures should be fully used in ...

in solving exploration problems. Only taking account of the genetic features of structures will make it possible, on a scientific basis, to approach the prediction of the complexity of the structure of the coal-bearing areas being evaluated. This is possible only through a thorough paleotectonic analysis using all materials on variability in thicknesses and facies of coal-bearing deposits, total and workable coal content, and coal metamorphism.

Another classification criterion should be the morphological features of structures. In Kuzbass they are characterized by very great diversity, which is a reflection of the different conditions of their formation. Each tectonic zone has its own set of distinctive morphological types of structures. In this respect the set of types of plicative structures is especially rich. Here one may encounter any of them, with all possible transitions and deviations.

The fault structures of the basin are also highly diverse, which has been reflected in the classifications of M. A. Usov, I. A. Molchanov, A. A. Belitsky, and A. S. Zabrodin. Within the various tectonic zones almost all types of faults are encountered. Analysis of materials from exploration and mining operations, however, has shown that within individual zones only certain forms of faults are predominantly developed, and this, undoubtedly, should be reflected in the new classification.

Together with genetic features, the morphology of structural forms makes it possible to distinguish with sufficient precision the structures of different zones and, what is very important, to outline methodological techniques for their study. True, certain difficulties arise in realizing this possibility. The chief ones are connected with the fact that structures are of different ages in their formation, or that their formation was almost completed at different stages, which at present are difficult to establish because of the fragmentary nature of the factual material. Nevertheless, the available geological observations on this question must be used to the fullest extent.

The new classification should also take into account the influence of different structures on the conduct of exploration and mining operations. First of all, this concerns the dimensions of structures. Especially great diversity is observed here, while the role of structural dimensions in exploration and mining is far from uniform. Table 1 gives a classification of the structures of the coal-bearing deposits of Kuzbass by size, their significance in laying out mine fields and in carrying out mining operations, and also indicates the principal stage at which structures of different orders are discovered and studied. This classification takes into account the recommendations for studying the geological structure of mine fields during underground mining of coal deposits [3], and thus a certain continuity is maintained between the materials of geological exploration work and mining operations.

The folds of Kuzbass are characterized by highly varied dips of the limbs. According to statistical data [4], in 1955 the following distribution of coal production by the character of dip of the coal seams took place: seams with gentle dip accounted for 36.6% of production, those with inclined dip for 19.3%, and those with steep dip for 44.7% of annual coal production. In recent years, in connection with the commissioning of new coal-mining enterprises in the Tom-Usinsk, Kemerovo, Leninsk, Anzhero, Belovo, and other districts, the role of seams with gentle and inclined dip in the basin’s total coal production has increased somewhat and their significance has become more balanced. This indicates that, in the process of exploration, preference should not be given to any one of these groups, but at the same time areas with different angles of di—

Table 1

* Height is indicated for folds whose limbs have inclined (25–45°) and steep (45–90°) attitudes.

...deposits. Often this factor exerts a decisive influence when choosing a mining system.

Finally, one must also take into account such a factor as the jointing of the coal and enclosing rocks. The inclusion of this factor in the new classification is connected with its great importance in solving a whole range of questions—for example, in refining the phases of tectogenesis or the conditions under which tectonic structures formed, the degree of their dislocation, etc.

Taking all these considerations into account, the following classification of areas is proposed for unified exploration methods.

Type I. Near-Platform Zone of “Discontinuous Folding”

This type of structure is distributed along the eastern and southern margins of Kuzbass and corresponds fully to the “monocline zone.” Considering that the main features of the structures of this and other types have already been described in print [2], we shall describe the smaller units of the classification.

Two subtypes are distinguished within Type I.

1. The Near-Kuznetsk Alatau subtype. The chief genetic feature of the structures of this subtype is the weak mobility of the basement. The structures formed mainly under the influence of tangential forces from the Kolyvan–Tomsk folded arc and did not undergo substantial rearrangements. This was also reflected in the jointing of the rocks. Here “endogenous” (normal-cutting) joints are developed. Joints of “exogenous” (oblique-cutting) systems appear only in areas of tectonic complications.

Within this subtype, only one group—group “a”—is distinguished by structural-tectonic criteria.

Group “a” is characterized by monocline occurrence of the seams, dipping to the northwest. Dip angles range from 5–10° to 30–40°, with a comparatively persistent strike. Additional folds of simple configuration are encountered rarely; as a rule, they are associated with fault disturbances. Complications in the occurrence of coal seams in the form of waviness and flexures occur somewhat more often.

Fault disturbances are few in number. They are predominantly medium- and small-amplitude diagonal conformable reverse faults with a southwestern strike of the displacers. Sometimes they occur singly, but more often they form groups, especially in places where the strike and dip of coal seams change sharply. In such places, faults with amplitudes of tens of meters are accompanied by small faults of the type of diagonal conformable and nonconformable reverse faults.

An example of the structures of group “a” is the Biryulinsky monocline.

1. The Gornaya Shoria subtype. The formation of the structures of this subtype was influenced primarily both by vertical movements and by tangential compressions from the Kuznetsk Alatau (Gornaya Shoria), with which manifestations of magmatism and the morphology and orientation of folds and faults are connected. The plicatogenic character of some faults, the folding of seams, interruptions in sediment accumulation, and the angular unconformity between Paleozoic and Jurassic deposits emphasize the multiphase nature of structural formation. The influence of movements from the Salair side is also not excluded, but apparently it was insignificant.

The more complex conditions of structural formation found reflec-

is manifested in a complication of the character of fracturing. Along with the two systems of orthogonal fractures that are widespread everywhere, up to six systems of diagonal fractures are developed here. At the same time, their genesis, morphology, and intensity depend on the degree of general dislocation of the area.

Within this subtype two groups are distinguished—“b” and “c.” Group “b” comprises areas with monoclinal bedding of coal-bearing deposits. The dip angles of the latter gradually increase toward the northeast from 10–15° to 40–50°. The monoclinal bedding is complicated by weak undulation (everywhere) and by distinct gentle asymmetric additional folds, the sizes and frequency of which increase somewhat toward the southwest. The fold axes are diagonal to the general strike of the monocline and plunge at an angle of 3–5° along azimuth 0–30°. The morphology of the folds is inconsistent. The degree of plicative disturbance of adjacent seams often proves to be different.

Within areas of group “b,” small- and, more rarely, medium-amplitude faults are widespread, mainly of three types: most numerous are diagonal, discordant, submeridional, gently dipping reverse faults (“overthrusts”); less common are steeply dipping transverse strike-slip faults and sublatitudinal reverse–strike-slip faults, predominantly with southern dips of the fault planes. In areas with steep dips of the seams, direct thrusts are observed. Faults are usually concentrated in groups and tend toward folds and other complications, although isolated fault disturbances also occur. As an example of structures of group “b,” one may cite the Main (Western) monocline.

Group “c” includes areas with shallow, predominantly broad, en echelon-arranged large and medium-sized folds with frequent bends of the axes and the formation of a number of brachystructures. The western limbs of the anticlines are steeper than the eastern ones, and in places are overturned. Near large faults, small folds are observed.

Fault disturbances are represented by a series of large gentle faults with fault planes dipping to the northeast. Some of them are possibly plicatogenic. Here, too, prospecting work and coastal outcrops have established a large number of varied small faults. The Chulzhan zone of gentle folds may serve as an example of the structures of this group.

Type II. Central zone of folding of transitional type

This type of structures encompasses an area corresponding to the Central zone of gentle folds and dome-like uplifts [2]. By morphogenetic features, two subtypes are likewise distinguished here.

1. South Kuzbass subtype. The formation of structures of the subtype took place mainly under the influence of movements from the side of the Salair. This is emphasized by the asymmetry of the folds and by the direction of dip of the fault planes of large faults. It was multiphase, which found expression in the formation of plicatogenic fault disturbances. There are no grounds to deny the influence of pressures from the southwest, as well as the existence of long-developing uplifts in the form of the Abashevo dome and the Chernokaltan anticline, especially on the formation of structures of the first group of this subtype.

Fracturing here is characterized by the predominance of orthogonal fractures, longitudinal and transverse to the axes of large folds. Diagonal fractures are represented by two pairs of conjugate pro-

longitudinal and transverse to the axes of folds—systems of local deformation plans, which are far from ubiquitous.

In the subtype under consideration we distinguish two groups. Group “a” comprises areas with gentle (5–30°) monoclinal bedding of rocks. The main limbs of very large synclines seem to envelop the corresponding uplifts from the north, which causes a smooth change in the strike of the seams. These limbs are complicated by undulation and by additional folds, the degree of manifestation and the dimensions of the latter varying with distance from the axial part of the main fold. The additional folds are medium and small in size, usually asymmetrical, with axes changing direction both in plan and in section, and with the axial surfaces dipping to the northwest and southeast.

Fault disturbances are comparatively few. Large-amplitude faults are usually conformable reverse faults. In the flanks of such faults and in places of plicative complications of the seams, predominantly small and medium conformable and nonconformable reverse faults and upthrusts are encountered. In places there are isolated faults, as a rule not traceable in adjacent seams. This group includes the eastern limbs of the Baidaevskaya and Shelkan synclines.

Group “b”. Steep to overturned bedding of seams with a dip to the southeast and a relatively persistent strike, with insignificant complications in the form of undulation and additional folds. The latter are often associated with large-amplitude faults. With distance from the axial parts of the principal structures, additional folds appear and increase to large size, with comparatively gentle angles of dip of the limbs; they are arranged en echelon, with curved and undulating axes, and with a western or northwestern dip of the axial surfaces.

Faults of various forms and amplitudes are numerous. Where the seams have steep bedding, overthrusts and overthrust faults are predominantly widespread; where bedding is gentle and inclined, conformable and nonconformable reverse faults occur. Large faults not infrequently have a plicatogenic character, changing the dip angles of the dislocators from 0° to 90°. Small- and medium-amplitude faults are usually diagonal and longitudinal, more rarely transverse. Their dislocators have a northeastern or northwestern dip. The maximum number of faults is observed in the flanks of large faults and in the closures of folds, especially in places where they bend sharply.

Examples: the western limbs of the Shelkan (Elban) and Baidaevskaya synclines.

2. Central subtype. The character of the structures of the subtype is largely determined by their distance from the mountain structures surrounding the basin, which exerted a great influence on the formation of other structures of the basin. Connected with this are, first, a relatively simple structure, and, second, the contradictory nature of the structural features. Thus, the axial surfaces of many folds dip southward, while the dislocators of faults have a northern dip. The structures were undoubtedly formed under the influence of differently directed, multiphase, but weakened tectonic movements.

Apparently, the principal type of fracturing here will prove to be exogenous. By analogy with the subtype considered above, one may assume the appearance also of obliquely cutting fractures in areas of local complication of structures.

For the present, within the subtype it appears possible to distinguish only one group.

Group “v”. Broad, diffuse forms of very large and large folds. The orientation of their axes changes from submeridional—

…to nearly latitudinal, while remaining predominantly close to the latter. Asymmetry of the folds is characteristic: the limbs dipping south are usually gentler (10–30°) than those dipping north (50–60°). The fold axes undulate, branch, and have bends in the vertical plane. In plan, in the southern part they are convex to the north, and in the northern part—to the south. Undulation of the axes often leads to the formation of brachyfolds and structural noses. Additional folds are rare, but waviness is observed almost everywhere.

Fault disturbances, from small to large, most often occur at the sites of anticlinal bends of coal seams, although they are also observed on the limbs of folds. These are mainly gently dipping reverse faults and thrusts, with fault planes dipping to the northeast and northwest at angles of 10–40° and with crushing zones up to 100 m. The regularities in the occurrence of small faults have not been established because of the absence of mining operations, but their presence in some exploratory boreholes is beyond doubt.

Examples: the Antonovo, Kusheyakovo, Erunakovskaya, and Kyrgai-Ostashkino synclines, and the Markino-Nikolskaya and Naryk anticlines.

Type III. Zone of “comb-like folding”

The areas over which structures of this type are distributed correspond to the eastern halves of the Prisalair and Prikolыvan-Tomsk zones of linear folding and faults [2]. As in the previous cases, two subtypes are distinguished within this type.

1. Belovo-Gramoteino subtype. The tectonic structures of the subtype owe their formation mainly to influence from the direction of Salair. Initially this was expressed in uneven radial movements of blocks, subsequently replaced by tangential movements attenuated toward the center of the basin. The western blocks were the most mobile; there the maximum thicknesses of sediments and the greatest metamorphism are observed. With increasing distance from Salair the structures become simpler, although the zones of influence of the bounding slices of very large faults remain just as complex. Block movements along regional faults protected the inner parts of the folds within individual slices from further complication.

Normally intersecting jointing predominates. With respect to the orientation of the axes of large folds, transverse and longitudinal systems are distinguished. Obliquely intersecting joints are characteristic mainly of areas where structures are complicated by small folds and disjunctives, and of zones affected by major faults. Systems of longitudinal and diagonal joints have undergone predominant development.

Within this subtype, two groups of structures are distinguished. Group “a”. Very large folds represented by broad, northwest-elongated trough-like, or nearly trough-like, brachysynclines with gentle bottom parts and rather steep (up to 60°) limbs. Closer to the center of the basin the intensity of the folds decreases; they become symmetrical and more rounded. Undulation of the axes and their bends in plan are characteristic, especially in centriclines that formed both at the initial and at the final stages of folding. The main folds are complicated by gentle transverse waves and additional folds, especially in the centriclines and at the margins of faults.

The fault tectonics of the group is largely determined by a series of subparallel, very large faults that delimit individual slices and are one of the principal elements of the next group.

The large folds indicated above are affected by large- and medium-amplitude faults, parallel to the former, dipping to the southwest at angles of up to 40–50°. In form these are predominantly conformable and unconformable reverse faults, on the flanks of which small transverse and diagonal faults are developed. The second group of small faults is confined to the anticlinal bends of the axes of brachysynclines, where various faults are observed, but they lead mainly to duplication of the seams.

Examples: the Belovskaya, Leninskaya, Egozovo-Krasnoyarskaya, Tarsminskaya, and Dunaevskaya synclines.

Group “b”. Large and very large narrow, elongated anticlines with steep (up to 70°) limbs. Their closures are usually affected by very large longitudinal faults, accompanied by medium- and small-amplitude faults and additional folds. Undulation of the axes of the principal anticlines has led to the creation of chains of brachystructures, the deciphering of which is greatly hampered by the high degree of disturbance. Small folds on the flanks of faults prove to be predominant.

The fault disturbances are represented by very large regional faults with a southwestward dip of the fault planes at angles from 30 to 50°, accompanied by zones of smaller faults with brecciated and mylonitized rocks up to 0.3–0.5 km wide in plan. The principal faults are accompanied by a series of parallel reverse faults or direct thrusts. With increasing distance from the main fault plane, the morphology of faults in the zones of influence changes. Faults appear whose orientation is controlled by the bedding, as well as diagonal and transverse faults, but their number gradually decreases.

Examples: the Novorossiyskaya, Mokhovo-Pesterevskaya, Vinogradovskaya, Kamyslinskaya, and Uropskaya anticlines.

2. Anzhero-Kemerovo subtype. The formation of the subtype structures at the early stages proceeded through uneven oscillatory movements of the basement and the formation of gentle uplifts and troughs that inherited the structural plan of the Caledonides of the northwestern margin of the Kuznetsk Alatau. Subsequently, the fold-forming processes in the Kolyvan-Tomsk zone became dominant, leading to the creation of enormous tangential stresses and to a prolonged process of predominantly horizontal displacement of masses, with formation of the Tomsk thrust and other fault disturbances and with strong deformation of the rocks of the coal-bearing complex. In the concluding stages of tangential pressure, some fault disturbances acquired a plicatogenic character. New faults also appeared, especially on the flanks of large faults and in areas of further complication of plicative structures.

Almost everywhere four systems of normal-secant fractures are developed. Their clear geometric relation to fold axes is in most cases disrupted. Oblique-secant fractures also play an important role here. Among the latter, as many as eight systems are distinguished.

Within the subtype, at least three groups of structures should be distinguished.

Group “v”. Very large brachyfolds, broad and with gently dipping limbs, arranged en echelon relative to one another. The axes of the folds have a variable trend (mainly convex eastward) and undulate in longitudinal section. Asymmetry is characteristic: limbs dipping eastward are steeper (25–80°) than those dipping westward (5–30°). The eastern limbs of the brachysynclines gradually pass into group “a” of the first type. Various …

...additional fold-like structures, especially on the flanks of fault disturbances and in areas where the axes of the principal folds bend. Flexure-like bends and undulation of coal seams are also frequent.

Fault disturbances are represented by a dense network of faults of various forms and amplitudes. On the limbs of folds with a western dip, conformable upthrows are predominantly developed; with an eastern dip, nonconformable upthrows and especially straight thrusts. The displacers of some faults bend in the crests of folds, creating different geometric forms on opposite limbs. Large faults are often accompanied by zones of small faults.

Example: the Andreevskaya, Glushinskaya, and Kedrovsko-Krokhalevskaya brachysynclines.

Group “g”. Complex knots of additional folds of medium and small size, confined to areas of anticlinal bends of the axes of the principal plicative structures. The folds are distinguished by instability of form and orientation, with coal seams lying comparatively gently. Numerous diverse small complications: undulation, flexures, pinches, swellings, and bedding-plane displacements.

Numerous medium- and especially small-amplitude faults are associated, as a rule, with the formation of folds and their complications. The faults are diverse in form; they often change the attitude elements of the displacers, frequently repeat changes in the forms of folds, and, possibly, some of them are plicatogenic. The prevailing forms of faults are established with great difficulty.

Examples: the Klyuchevskoye uplift, and the closures of the Andreevskaya and Kedrovsko-Krokhalevskaya brachysynclines.

Group “d”. The structure is a clearly expressed zone of complex structure of the Tomsk thrust. The surface of the thrust displacer, in its orientation, is close to the general strike of the large folds and faults of the Kolyvan–Tomsk arc. The displacer is undulating and rather precisely repeats the configuration of the Anzherskaya syncline. Directly in the zone there occur tectonic breccias up to 15 m thick. The coal-bearing deposits located in the footwall of the thrust have a complex structure. Here, in a zone from 50 m to 200 m thick, the seams are crumpled into small folds and affected by a dense network of faults diverse in form and amplitude. With increasing distance from the thrust, the tectonic intensity decreases and the structures acquire a transitional character. An attempt to mine the coal seams in the thrust zone in the field of mine 9/15 was not successful.

Type IV. Near-synclinal zone of “complete folding”

This type includes the areas that are most complex tectonically, located within the subzones of intense linear folding of the Prisalaïr and Near-Kolyvan–Tomsk zones [2]. Taking into account the different conditions and times of formation of the tectonic structures, two subtypes are also distinguished within this type, combining five groups.

1. Prisalaïr subtype. The structures of the subtype are characterized by a very close connection between their formation and repeated tectonic movements from the direction of the Salaïr. In the first stages these were predominantly tangential compressions together with block movements, while subsequently the latter began to predominate, shaping the modern structural plan. Apparently, considerable significance was also attached to...

transverse anticlinal bends of the basin and, in particular, the Krasnobrodsko-Kyrgaisky and Aralichevo-Abashevsky, which led to the closure of the main synclinal structure of the Prokopyevsk-Kiselevsk area and its separation from the structures of the Bunguro-Chumysh and Bachaty areas. Block movements in the final stages along steep, very large faults created zones of influence of the latter, but preserved the plicative structures within individual slices from further complication. This also accounts for the comparatively small number of plicatogenic faults.

Systems of normal cross-cutting fractures are widely developed; at the same time, the dependence of their orientation on the axes of folds has been preserved. The normal cross-cutting fractures are to a considerable degree obscured by the intensely developed fractures of numerous obliquely cutting systems.

The great diversity of structural settings made it necessary to distinguish four groups in this subtype.

Group “a”. Steep limbs of very large and large folds with persistent or regularly varying bedding elements. Additional folds or waviness occur rarely.

Fault disturbances are of medium and small amplitude, often associated with intra- and interbed movements. They are usually concentrated in a definite part of a coal seam (at the floor, roof, more rarely in the middle part), transforming the coal into a structureless mass and creating false pinches and splits.

Examples: the western limbs of the Golubevskaya and Malaya anticlines in the field of the Koksovaya 1 mine; the western limb of the Promezhutochnaya anticline in the fields of mines No. 13 and Dalnie Gory, outside the zone of influence of fault \(R—R\).

Group “b”. Usually steep limbs of very large and large folds with relatively persistent bedding elements and a wide development of seam pinches and splits. Additional folds are comparatively rare and are more often associated with the formation of the main structures or with fault disturbances, forming seam deflections. The axes of the main folds undergo plunging or rising, as a result of which the folds locally acquire the character of brachyfolds.

Fault disturbances, from small to large, are very numerous and diverse. They are predominantly reverse and thrust faults; strike-slip faults are rarer, and upthrusts still rarer. The main group of faults is associated with the formation of plicative structures or is the result of repeated displacements along large faults, adjoining the zones of crushing formed along the flanks of the latter.

Examples: the western limb of Syncline 1 in the field of the Ziminka 3–4 mine; the Krasnogorskaya anticline in the fields of the Krasnogorskaya, No. 5–6, and Dzerzhinsky mines, outside the zones of influence of faults \(E—E\), \(P—P\), and \(S—S\).

Group “v”. Complex folded-faulted structures of medium and small size with steep, often variable dip angles. Numerous additional folds are present, mainly confined to the closure areas of large synclines and characterized by inconsistency of morphological forms and directions of their axes.

Fault disturbances, especially small ones, are very numerous. They are varied in form and are often associated with the formation of additional folds; they usually affect only individual seams, not being traced into adjacent ones, where other faults occur; in exploration work they are established with great difficulty and are often taken for additional folds.

Examples: the I and II Karaulnye synclines in the field of the Sever-

Mamayak,” the northern closure of syncline III in the field of the Vakhrushev Mine in the Prokopyevsk–Kiselevsk district, and the structures of the Bachat Deep and Central areas—in the Bachat district.

Group “g”. Plicative structures are rather indefinite. Only an analysis of materials from adjacent areas makes it possible to interpret them more unambiguously. Usually these are the closures of large anticlinal folds, less often their limbs, and still more rarely the closures of synclines. Often the principal structure is complicated by additional folds and by bends of beds on the flanks of numerous secondary faults. Under any reasonable tightening of the exploration grid, the elements of multivariance in the correlation of plicative and fault structures do not disappear.

Fault disturbances here are very large, of the type of longitudinal conformable and nonconformable reverse faults, accompanied by numerous faults of higher orders. Predominantly among the latter, diagonal faults are developed, producing gaps in the beds. The width of the zone of influence of the main fault depends on its amplitude, form, on various kinds of bends in the beds, and on the number and mutual arrangement of very large faults. Among the principal faults, ancient plicatogenic ones and more numerous, relatively young ones are distinguished. The latter, with the exception of the fault \(M—M\), dip to the southwest at steep angles, cutting out narrow imbricate slices.

Examples: zones of faults \(E—E\), \(P—P\), \(K—K\), \(K_1—K_1\) of the Tyrgan, \(M—M\), \(B—B\), \(R—R\), Afonino–Kiselevsk (\(S—S\)), \(G—G\), \(I—I\)—in the Prokopyevsk–Kiselevsk district, and fault \(A—A\)—in the Bachat district.

2. Prikolyvan–Tomsk subtype. The formation of structures of this subtype took place mainly under the influence of repeated tectonic compressions from the Kolyvan–Tomsk folded region, as evidenced by the overturning of folds to the east, their narrow elongated closures, and also the orientation and direction of dip of the principal faults.

According to the available fragmentary data, systems of normal-cutting and oblique-cutting fractures are developed here in equal measure; among the latter, diagonal conformable- and nonconformable-dipping fractures predominate.

The subtype has still been insufficiently studied, and for the present it appears possible to distinguish only one group.

Group “d”. Medium and large, very tight linear folds with inclined axes and sharp closures. Limbs with an easterly dip have steeper angles and are more often complicated by additional folds of high orders. Additional folds are not infrequently also encountered in the near-closure parts of large structures. Pinches and washouts of coal beds are widely developed.

Faults are represented by medium- and large-amplitude longitudinal reverse faults dipping steeply to the west—northwest and creating an imbricate structure. The near-closure parts and closures of anticlines are often affected by them. Small faults, varied in form and amplitude, are widely developed. Often the faults of adjacent, even closely spaced, beds are not correlated with one another. The greatest number of them occurs on the flanks of large faults and in places where additional folds are developed.

Examples: structures of the fields of the Yagunovskaya, Pioneer, and Mazurovskaya mines in the Kemerovo district; the Osinovogrivsk–Tykhtinsk and Pavlinovsk–Kornilovsk anticlines in the Titovo district.

From the description given above it is evident that in this classification four types of structures have been distinguished. Each type is divided into two subtypes, within which separate groups have been distinguished. In the first two types

allocated to three groups, and in two other, more complex ones, to five groups each. In all, sixteen groups are proposed for distinction.

Of course, it is difficult to imagine that the entire diversity of structural settings in the mine fields of Kuzbass is covered by these groups. There are various transitions between them. The allocation of transitional structures into independent groups would hardly be justified. The classification would become substantially more complicated, but would not become more flexible.

In most cases the character of the structural setting under transitional conditions can be established only by generalizing materials from the exploitation of deposits. At the stage of detailed exploration it can only be assumed on the basis of predictive constructions. On the other hand, knowing the morphological features of structures of the distinguished subtypes and groups, any structural setting can also be evaluated from the standpoint of the proposed grouping.

The possibility of distinguishing new groups is not rejected completely. It may prove necessary as new geological materials are obtained in poorly studied areas. This applies first of all to the Central and Prikolban-Tomsk subtypes.

The proposed grouping resulted from a generalization of materials on the tectonics of mine fields in various regions of Kuzbass, established by exploration and, chiefly, by mining operations. Simultaneously with the generalization of extensive materials on tectonics, an analysis was made of the exploration methods used for coal deposits of various types. The principal method of this analysis was taken to be comparison of exploration materials with data from mining operations.

Analysis has shown that the possibilities for exploring structures of different groups are far from identical. This is clearly seen from Table 2, which gives the principal features of their exploration. The reliability of structural constructions for structures of different types, subtypes, and groups also differs, both at the exploration stages and in the final version.

In the general case, the reliability of structural constructions based on exploration data decreases from the first type to the fourth. It is especially low for areas of the third (groups “b” and “d”) and fourth (groups “v” and “g”) types.

The causes of discrepancies in structural constructions based on exploration and mining data are also different. Analysis of them leads to the conclusion that they may be either systematic or random in character. There are causes that may appear both as systematic and as random. Below they are assigned to the group in which they occur more often.

The following causes mainly appear as systematic:

1. Insufficient use, in conducting exploration work, of operating materials from adjacent areas. Most often this is connected with the imperfection of geological servicing at operating mining enterprises and, consequently, with the incompleteness of geological materials from the mine-geology service.

2. The absence of fundamental studies on the tectonics of the basin; many theoretical questions remain unresolved, and this seriously complicates the solution of practical problems.

3. “Standardization” of exploration methods, leading to the absence of

Table 2

an individual approach to the exploration of areas of different types. Quite often the exploration of one area differs from the exploration of another area, situated under different conditions, only in the density of the exploration grid.

1. The insufficient accuracy of existing technical means of exploration, and in some cases their inept use. In most cases there are no precise coordinates for the points at which coal seams are intersected by boreholes, and this leads to distortion of the structures in sections along exploration lines.

2. Simplification of structures in sections along exploration lines because of insufficient factual data. Often further densification of the exploration grid proves inexpedient, since in complex structures the elements of multivariant interpretation do not thereby disappear.

3. The absence of a reliable geological basis for planning geological-exploration work. Paradoxical as it may seem, large-scale geological mapping in Kuzbass has begun to be carried out only in recent years.

4. The presence of numerous small-amplitude fault disturbances and small folds, flexures, and undulations that cannot be detected by boreholes even at the maximum density of the exploration grid. In individual cases such disturbances substantially alter ideas about the tectonics of the areas being explored.

The random causes of discrepancies between the morphology of structures established by exploration work and their actual morphology may include:

1. Insufficient tracing of coal-seam outcrops beneath drift deposits, which is especially dangerous in the absence of large-scale geological maps.

2. In individual cases, the low qualification of personnel engaged in the primary geological documentation of exploration workings and boreholes. The absence of such a course as “Geotectonics” in the curricula of geological-exploration specialties in higher educational institutions is also puzzling.

3. An unjustified density of the exploration grid, not corresponding to the character of the structures of the mine field being explored.

4. An incorrectly identified seam or group of seams in an exploration borehole.

5. Errors in determining the dip angles of the bedding and the unsuccessful application of the bisector method in constructing geological sections along exploration lines, especially in zones influenced by major fault disturbances.

6. In some cases, fault disturbances are interpreted as small folds. In other cases, faults are shown on sections instead of folds.

7. When multivariant interpretation is possible, usually only one variant is selected, which often proves to be entirely accidental.

8. Violation of the staging of geological-exploration work and, as a consequence, failure to take account of the peculiarity of structural settings—these are also causes of random discrepancies in structural constructions.

These are the main causes which in individual cases lead to serious errors in determining the morphogenetic features of structures. It seems to us that the results obtained from the study of the tectonics of mine fields, reflected in the proposed classification, and the analysis of exploration methodology, its features and the degree of reliability of structural constructions, may prove fruitful for the further improvement of ways of solving exploration problems.

References

1. A. A. Belitsky, E. M. Pakh. Regularities in the tectonic structure of the Kuznetsk Basin. — In: The Basic Ideas of M. A. Usov in Geology. Alma-Ata, 1960.

2. Geology of Coal and Oil-Shale Deposits of the USSR. Vol. 7. Nedra, Moscow, 1969.

3. A. S. Zabrodin, I. S. Garber, Z. D. Nizguretsky. Manual on the Geological Documentation of Underground Workings at Kuzbass Mines. VNIMI Publishing House, Leningrad, 1959.

4. The Kuznetsk Coal Basin. Statistical Handbook. Ugletekhizdat, 1959.

5. V. S. Muromtsev. The Kuznetsk Depression. Transactions of VNIGRI, issue 96. Essays on the Geology of the USSR. Vol. 1, 1956.

6. V. E. Nekipelov. On certain shortcomings in the assessment of coal-deposit reserves. Razvedka i okhrana nedr, No. 9, 1969.

7. E. M. Pakh, E. M. Senderzon. Density of the network of detailed exploration and testing of coal deposits in Kuzbass. Problems of the Geology of Kuzbass, vol. 11, 1959.

8. E. M. Senderzon, G. M. Kostamanov. Elements of tectonics and age relationships of disjunctive disturbances in the Kuznetsk Basin. Proceedings of the Second Coal Geological Conference. Moscow, 1956.