On the Grouping of Structures of Coal Deposits in Kuzbass for Unified Exploration Methods
Abstract Generated abstract
This paper addresses the need for unified exploration methods for Kuzbass coal deposits after newer reserve-classification instructions ceased to group deposits by natural factors relevant to exploration. On the basis of structural and tectonic analysis of mine fields across the basin, the authors argue that two related classifications are needed: a geological-prospecting classification reflecting genetic, morphological, and structural features, and an exploration classification grouping deposits by common technical and methodological requirements. They propose a structural-tectonic scheme for Paleozoic coal-accumulation areas and a practical exploration grouping based on the morphology of large structures and the associated regularities of medium and small folds and faults. The paper concludes that using both classifications at different exploration stages can improve forecasting, guide exploration grids and methods, and reduce overly stereotyped approaches.
Full Text
On the Grouping of Structures of Coal Deposits in Kuzbass for Unified Exploration Methods
V. Ya. Koudelny, P. I. Shirin
(Presented by the seminar of the Department of Geology and Exploration of Mineral Deposits)
Unlike the previously valid instructions on applying reserve classifications to coal deposits [2, 3], the latest instruction [4] does not provide a grouping of deposits according to the natural factors that determine the methodology of exploration work. Production and scientific organizations have been asked to develop guidelines on exploration methodology in the principal coal basins of the USSR, including the Kuznetsk Basin.
We have been engaged in grouping the areas of Paleozoic coal accumulation in Kuzbass according to structural-tectonic characteristics. On the basis of an analysis of the tectonics of mine fields in various districts of the basin, as well as of the methods used and the reliability of its study, an attempt was made to provide a classification of structures for unified exploration methods. The study of structures was accompanied by an analysis of the methodology and particular features of their exploration. In doing so, it was confirmed that at different stages of prospecting and exploration the possibilities and reliability of studying structures are far from identical.
It is known that the delimitation of exploration stages is based on geological tasks, the solution of which must be obtained as a result of the work carried out. These tasks determine both the choice of technical means and the methodological techniques of exploration. It is also known that the decisive role of the geological features of a deposit in the choice of technical means and methodological techniques of exploration served as the basis for creating groupings of deposits for unified exploration methods. A general shortcoming of such groupings is their universalism. In them an attempt is made to combine and take into account, on the one hand, the geological features of deposits and, on the other, the technique and methodology of exploration, in particular the density of exploratory workings for the corresponding groups of deposits.
The geological features of deposits remain constant and do not depend on the technique and methodology of exploration. At the same time, as indicated above, the technique and methodology of exploration depend not only on the features of deposits, but also on the geological tasks solved at one or another stage of their study. Hence follows the necessity of having at least two classifications.
One of them (geological-prospecting) must fully reflect the geological features of deposits. It must take into account genetic, morphological, structural, and other characteristics.
The other classification (exploration) must be a classification of deposits for unified exploration methods. It is intended to combine individual morphogenetic types of the first classification according to the commonality of technical and methodological techniques of exploration.
The role and significance of these classifications at different stages of the study of mine fields differ sharply. The latter is determined both by the completeness of information on the structure of the field by the start of work at one or another stage and by the geological tasks being solved at that stage.
At the stages of prospecting and preliminary exploration, the geological-prospecting classification should be of primary importance. Taking into account the location of the work area, and applying the method of analogy, it is possible in advance to predict the character of the manifestation of geotectonic regimes and the general regional variability of structural settings, which ultimately predetermines the possible morphogenetic types of structures in the work area. This, in turn, will help correctly determine the direction of prospecting and exploration work, outline the appropriate set of investigations, and correctly assess the prospects of the area under study. Morphogenetic concepts of structures can be used to establish the character and the spacing of the exploration grid adopted at these stages. As such a classification, we have proposed a classification of fields according to structural-tectonic features (Table 1).
Table 1
| Type | Subtype | Group |
|---|---|---|
| I Periplatform zone of “discontinuous” folding | 1 Prikuznetsk-Alatau | *a |
| I Periplatform zone of “discontinuous” folding | 2 Prigornoshorskii | v, b |
| II Central zone of “transitional” type folding | 1 South Kuzbass | a, b |
| II Central zone of “transitional” type folding | 2 Central | v |
| III Zone of “ridge-like” folding | 1 Belovo-Gramoteino | a, b |
| III Zone of “ridge-like” folding | 2 Anzhero-Kemerovo | v, g, d |
| IV Prisalaire synclinal zone of “complete” folding | 1 Prisalaire | a, b, v, g |
| IV Prisalaire synclinal zone of “complete” folding | 2 Prikolyvan-Tomsk | d |
* The characterization of the groups is not given here.
In order for it to be fully geological-prospecting and able to fulfill its purpose, other geological features must also be reflected in it (coal content, seam stability, coal quality, and so forth).
At the stage of detailed exploration, coal-exploration geologists have to solve a different, more specific range of questions connected with the tectonics of the deposit. At this stage of work, mainly medium-sized and small folds are detected and studied, as well as medium- and small-amplitude disjunctive disturbances. Analysis of the structures of mine fields and clarification of the mechanism of their formation make it possible to conclude that these medium-sized and small folds and faults have certain features that should be taken into account in their study.
Their distinctive feature is a close genetic connection with larger structures. This is evidenced both by their joint occurrence and by the confinement of small structures to definite parts of large ones. It has been established that the formation of these small structures is not simultaneous and is connected with the formation of the principal structures.
The second feature of medium and small disturbances is their comparative uniformity across all geotectonic zones or types of structures. Regardless of the zone in which these disturbances are encountered, although they vary in form, they remain of the same type. This circumstance made it possible for A. A. Belitskii, I. I. Molchanov, E. M. Pakh, and A. V. Tyzhnov to distinguish three groups of supplementary folds and three groups of disjunctive disturbances encountered in Kuzbass in all geotectonic zones [1].
From the two features indicated above there follows yet another feature, namely that, in the formation of the group of disturbances under consideration, the decisive factor is not the genetic type of the major structures, but their morphological features. The presence of morphologically similar structures in different geotectonic zones was the result of the comparative uniformity of medium-sized and small disturbances. It follows from this that, if the formation of large structures was chiefly influenced by the geotectonic regime of the area in which they occur, then the formation and character of medium-sized and small disturbances were influenced mainly by the local conditions of deformation of the rocks, reflected in the morphology of the principal folds and faults.
Analyzing the geological-prospecting classification of areas of Paleozoic coal accumulation according to structural-tectonic features, it is not difficult to see that individual subtypes and groups are characterized by a set of large structures with very similar morphological features. Thus, monoclinal occurrence with persistent or smoothly and regularly changing strike and dip of coal seams, without significant manifestation of flexures and additional folds, may be encountered in any structural zone of Kuzbass. Broad large asymmetric folds with inclined and steeply dipping limbs, complicated by waviness and by single additional folds, are characteristic of the Central, South Kuzbass, and Anzhero-Kemerovo subtypes. Steep large folds with moderate development of additional folds and very numerous and diverse tectonic faults are most highly developed within the zone of “comb-like” folding. In these same zones (the Anzhero-Kemerovo and Salair subtypes), complex fold-fault structures of medium and small size, with inconsistent forms and orientations, are not uncommon, with a great variety of additional folds and a dense network of fault disturbances. On the basis of the similarity of the morphological features of the large structures, taking into account the character and regularities of manifestation of medium-sized and small folds and faults, a new classification can be created, which will serve as the exploration classification of areas for similar exploration methods.
Table 2 gives a possible version of such a classification.
Table 2
| Varieties | Principal morphological features of structures | Examples (groups of structures of the geological-prospecting classification) |
|---|---|---|
| A | Monoclines with persistent or smoothly and regularly changing elements of occurrence of coal seams, without significant manifestation of flexures and additional folds. Fault disturbances are few in number. | I—1-a, I—1-b, II—1-a, III—1-a, IV—1-a |
| B | Broad large asymmetric folds with inclined and steep occurrence of the limbs, complicated by waviness and single additional folds. Gently dipping, often plicatogenic large fault disturbances are developed. Small faults are relatively numerous. | I—2-v, II—2-v, III—2-v |
| V | Steep limbs of large folds with moderate development of additional folds and very numerous and diverse tectonic faults. | II—1-b, III—1-b, IV—1-b, IV—2-d |
| G | Complex fold-fault structures of medium and small size, of inconsistent forms and orientation, with a great variety of numerous additional folds and a dense network of fault disturbances. | III—2-g, IV—1-v |
| D | Zones of influence of large-amplitude fault disturbances, with largely indeterminate plicative structures and diverse faults of higher orders. | III—2-d, IV—1-g |
It appears to us to be quite acceptable. On the one hand, this classification reflects the morphological types of large structures fairly fully, and all the groups distinguished in the geological-prospecting classification have found expression in it. On the other hand, it is multitype, which is of no small importance in its practical application. At the same time, each variety is characterized by fairly clear-cut exploration features.
At the stage of detailed exploration, concrete data on the morphological features in the conditions of occurrence of coal seams acquire decisive importance. The use of broad analogy here is of lesser significance, although the correct assignment of the structures under study to one or another morphological type considerably facilitates the solution of exploration problems, since in this case the general plan of deformation of the coal-bearing deposits is taken into account.
At the same time, the object of detailed exploration is highly specific, which is due, along with the general plan of deformation, also to the local plan of deformation. For this reason, the role of concrete forecasting increases, based on the regularities of the manifestation of tectonics within the area being explored and in the areas nearest to it.
Both classifications should be used at all stages of the study of deposits, although their role and significance will change from stage to stage. Separate consideration of the tectonic (geological) and exploration features of the structures under study will help to reveal their individuality more fully and, while maintaining similarity in the methodological techniques of exploration, to achieve a more effective study of them. If the exploration classification, as it were, unifies the techniques and methods of exploration, then the geological-prospecting classification emphasizes the need to take full account of geological conditions and cautions against stereotyped methods of solving exploration problems.
REFERENCES
-
Geology of Coal and Oil-Shale Deposits of the USSR. Moscow, Nedra, vol. 7, 1969.
-
Instructions for Applying the Classification of Reserves of Solid Mineral Resources. Moscow, Gosgeoltekhizdat, issue 2, 1947.
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Instructions for Applying the Classification of Reserves to Coal Deposits. Moscow, Gosgeoltekhizdat, 1954.
-
Instructions for Applying the Classification of Reserves to Coal and Oil-Shale Deposits. Moscow, Nedra, 1968.