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Legends of geochemical maps
Journal of Geochemical Exploration, 21 (1984) 481--486
481
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
LEGENDS OF GEOCHEMICAL MAPS
Yu.G. SHCHERBAKOV
Institute of Geology and Geophysics, Siberian Branch of Academy of Sciences of the U.S.S.R. Novosibirsk (U.S.S.R.) (Received January 9, 1984)
ABSTRACT Shcherbakov, Yu.G., 1984. Legends of geochemical maps. J. Geochem. Explor., 21: 481--486. Analysis of geochemical maps and their legends permits the proposal of several ways of improving their information content. Firstly, coherent and comparable classification of the objects to be presented must be developed. This classification should be based on strictly defined quantitative geochemical features of the objects; natural associations, anomalous elements, rocks, ore deposits and ore-bearing areas. Secondly, the most informative features of objects must be selected and uniquely displayed with a standard set of symbols. These symbols must be clear, readily understood and logically connected. The third requirement is that maps must be prepared in accordance with the tasks they are intended to deal with, must be optimally scaled, and display only appropriate information. One possible way of meeting the above-mentioned requirements, is proposed in a system of geochemical discrimination and related map presentation methods. The latter involves black hachures for the geological base, and directed colour lines and other features of colour hachures to characterize geochemical associations. Ore deposits may be characterized on the basis of eight most meaningful features encoded in one complex hieroglyph-like symbol constructed from easily understood and memorable components. This type of construction facilitates the computerized analysis of maps and makes them far more useful for prognosis, genetic reconstruction and resource evaluation.
INTRODUCTION
Geochemical maps reflecting the composition of geological entities are used for genetic reconstructions and for the prognosis, discovery and evaluation of ore deposits. The complexity of the information to be analyzed by geochemical mapping makes it essential to precisely define the task to be undertaken and to select an appropriate map scale at which the information can be best presented. Fersman (1953) c o m m e n t e d on the unsatisfactory dualism and lack of clarity of some geochemical maps because of the use of u n c o m m o n and uncoordinated principles in their construction that lead to the deformation of spatial patterns and their interrelationships. The analysis of maps at different scales, the different principles 0375-6742/84/$03.00
© 1984 Elsevier Science Publishers B.V.
482 underlying their construction and different symbols used reveals shortcomings that reduce the effectiveness of mineral resources evaluation. Firstly, the scale is often n o t in accordance with the tasks the maps are intended to deal with. On small-scale maps many minor details which cannot be compared with the basic information are often shown, and one cannot use these, but one can be misled by them. On the other hand, many maps are lacking basic geological information essential for anomaly interpretation. As a whole, these shortcomings m a y be recognized as incoherence of information. Another c o m m o n weak point is an over-complexity of symbols, the huge number of which makes them hard to remember and even harder to use for understanding the really essential interrelationships. One of the main, and commonest, weak points of n o t only geochemical, but also of metallogenic, prognostic, mineral resources, and other maps is incomparability of parameters presented, which decreases the value of data on ore deposits and host rocks. Ore deposits and host rocks are distinguished using different and unrelated principles and symbols. For example, the granulometric classification of sedimentary host rocks is often used as the only background for differentiation among ore-mineral associations, but, the most valuable details on the chemical composition of host rocks and ores are n o t compared, even if all the necessary information is available. This shortcoming results from incompatability in the underlying principles of classification of ore deposits, rocks, geological formations and chemical elements. For example, the geochemically similar chalcophile elements Pb, Zn, Cu, and Mo which are concentrated in c o m m o n sulphide minerals, differ on their contents in various rocks; Cu and Zn are concentrated more in basic rocks, and Pb and Mo more in acid ones. Accordingly, resources of the above-mentioned elements occur in deposits situated predominantly in basic and acid provinces, respectively. It is, however, impossible to get this information from the metallogenic and ore deposits maps because they do n o t reflect the quantitative distribution of these elements in rocks. Such incoherencies also occur in the legends of geochemical maps where they create difficulties in understanding the essential features of ore genesis and distribution and in the selection of areas for prospecting. The serious weakness of legends in all geological maps, including geochemical ones, is a lack of symbol uniformity for every definite quality of object. The colour code on one single map may be used for tectonic cycle designation, age of a set of rocks, composition of other sets and, most importantly, for some types o f ore deposits despite their relationship to different tectonic cycles or host-rock compositions. Such mixtures of meaning of even similar colours can only mask the possible relation among different patterns. Hachuring is widely used on maps, but the direction, thickness, and patterns of hachures often have no logic other than to try and make the map graphically pleasing. Named features are used randomly, making it difficult to remember them, and the possibility of the systematic
483
analysis of really meaningful qualities is completely lost. As the result the informativity decreases and interpretation becomes primitive. Geochemical maps do n o t achieve their possible potential as a tool for analysis and are an imperfect tool for geochemical data storage. The main challenge t o d a y is n o t in looking for new anomalies but in correctly interpreting the many thousands n o w known. Multimillion costs for discovering new mineral resources make improvements in the effectiveness of map presentation a very important international problem. We believe that improvements in the principles and methods of geochemical mapping and map analysis may play an important role in solving this problem. PROPOSAL
Taking into account the above-mentioned shortcomings o f geochemical maps some improvements are proposed. Initially, it is essential for many geochemical questions, from micro-scale regional surveys and prognosis to deposit depth and anomaly evaluation (Table I), to define the optimal scale of maps and their geological background. Table I demonstrates the main idea with relation to map scales and objectives. The relations between scale and legend size on one hand and scale and task (prognosis, search or evaluation) on the other, must be strictly defined in an optimal manner. To achieve that, the principles of object classification must be consistent with the manner of presentation of particulary meaningful features of ore deposits, anomalies, host rocks, underlying complexes of ore-bearing structure-formation zones if possible, etc. It is important to define the comparable features, of the objects, for instance, age, composition of associations, degree of spatial relation between the deposit and the sources of the ore elements, and mobility and other features of elements creating conditions for their c o m m o n concentration in deposits of different types. The objective is to develop and bring into accordance c o m m o n geochemical principles of classification of elements, minerals, rocks, ore deposits, geological formations, and areas of geochemical concentration, based on global features of elements distribution. These features may be defined quantitatively by the distribution coefficient among the main derivatives and initial systems, in particular the solar composition (0), carbon chondrites C1 (u), basaltoids (v) and clay shales (c). 0/u is the coefficient of volatility, v/~ is the oxyphility, and c/v is the siality. The high concentration of sialic elements (c/v > 1) in rocks, ores, and provinces leads us to assign them as sialic, and associate them with one colour in the legend, for instance, red, despite of the level of their complexity. The intensity of a colour may serve as an indicator of the degree of concentration for the sialic elements, being most intense in ores. Bringing consistency to every quality of object presented relative to the type of its manifestation will simplify legends and map analysis. This is a fundamental principle; legends must be simple
Whole Earth or continent
Ore province or belt
Ore cluster or zone
Ore and anomaly field
Ore deposit or anomaly
Observing 1:10,000,000
Forecasting 1:1,000,000
Prospecting 1 : 100,000
Follow-up 1 : 10,000
Mining 1 : 1000
Local forecasting to depth
Evaluation o f reserves (stocks)
Determination of ore fields and deposits resources
Selection of prospecting areas
Recognition o f global metallogenic patterns
Purpose of mapping
Main variations of ores and near-ore alterations
Ore deposits, occurrences, zones of alterations
Ore fields and deposits, their morphology, facies, age, etc.
Main ore province, belts, knots, zones, age of these
Features of ore deposits
Local peculiar- Morphology ity of rocks and composiand structures tion of orebodies
Lithology and petrography of rocks and their alterations
Suites, horizons, plutons, etc.
Geological formations o f 1--3 structure levels
Main tectonic structure and epoch
Geological background
Local distribution o f elements in ores and host rocks
Data of geochemical sampling, parameters of element distribution, including CC
Trends o f element distribution in all map units, aureoles
Geochemical types o f geological formations, aureoles ~ 5 km ~
Geochemical types o f main structure, complexes and provinces according to their femicity-siality
Geochemical data
CC (coefficient of concentration) is the average of anomalous contents/background.
Areas of geochemical mapping
Scales of maps
Recommendations for contents of geochemical maps of various scales
TABLE !
0v
485
and clear and the system used must be evident. As the simplest way to achieve this objective we propose a legend system which one need n o t refer back to repeatedly when analyzing a map. To illustrate the proposals let us turn to examples of application given in Table II. The geological background legend is omitted from further discussion because the use of black hachures in order to designate lithological and petrographical features of rocks satisfies our needs. The main geochemical compositional features of geological complexes, rocks, ores, and anomalies are coded in colour. Let the shift from the violet to the red part of spectrum reflect the increase of an object's siality, that is from ultrafemic--violet to ultrasialic-orange; femic is green and an intermediate composition is brown. It is convenient to use orientation of symbols, even of broad colour hachures, to indicate the age of all geological entities including ore deposits on the small- and medium-scale maps. The clockwise turn of orientation of symbols TABLE II Examples of recommended legends for geochemical maps Properties of objects to be mapped
Means of representation
Examples
Geochemical type~ : f= femic; s=sialic; o--oxyphile, oxygen; h=heterophyle, heterogen; v=volatile
Colour
f=green; s=red; fs-brown; h--blue; o=yellow; fh=violet; so=orange sh=crimson; v=azure; vs=deep red; vf=aquamarine
Coefficient of concentration
Intensity of colouring
minimum=clark background middle coloured=positive halos maximum=ore concentration
Coefficient of variation
Interruption of hachure
I I = low D [Z3 [Z] = high D [] [] DD = extremely high
Morphology of orebodies
F o r m of symbol
I
Distance from sources and facies of ore deposits; r=base, re=middle, a=apex
Place of shade in symbol; (blank; telescoping type = t)
Age
Direction of coloured hachures and symbols
)
= stratiform vein = complex =
~ ~ ~ ~
= = = =
small (r) middle (m) large (a) telescoping (t)
c\ b ~ \
hd \
~ f
a I
Shcherbakov, 1976, 1979, 1982). a = Precambrian; b = Proterozoic; c = Caledonian; d = Variscan; e = Mesozoic; f = Cenozoic.
486
indicates a decreasing age. The use of 3-mm-wide hachures with 3-mm intervals permits the coding of up to three geochemical structural phases. This way of presenting information creates a useful range of geochemical spatial patterns with potential for describing many features. The interruptions on hachure lines are useful for indicating the magnitude of variability in element distributions. The system significantly improves the characterization of geochemical anomalies on large-scale maps. The following features of ore deposits seem to be most important for systematic analysis, and hence must be well represented on geochemical maps: orebody morphology, genesis, geochemical type, association of the most concentrated elements, degree of spatial separation from the source (low, medium, high, variable), age, dimensions, and summary characteristics of the formation type (Shachov, 1966; Kuznetsov, 1972). All eight features are easily coded by one symbol (hieroglyph constructed of simple components), which indicates the morphology of ore bodies; width of contouring line shows genesis, colour codes show geochemical type of deposit or group of most concentrated elements, and location of shade in the symbol indicates the deposits position relative to the source of the elements (Table II). The orientation of the symbol always indicates age and the size will reflect the industrial significance of the deposit. Chemical indexes of predominant elements in ores may underline their oreformational characteristic. The main advantage of such combined, or "hieroglyphic", representation of ore-related objects is that it opens the possibility for composition, structure, age and position analysis. Especially, it allows the relation of the same and similarily expressed features of host and sometimes underlying rocks, such as their composition, genesis, age and so on to be easily displayed. The future development of the proposed legend system is possible only by the concerted efforts of many specialists concerned with the improvement of geochemical maps and their interpretation. REFERENCES Fersman, A.E., 1953. Geochimicheskoe kartirovanie. Izbrannye trudy, t II. Izdatel'stvo Academii Nauk SSSR, Moskwa, pp. 556--559 (in Russian). Kuznetsov, V.A., 1972. Rudnye formatsii. Geol. Geofis., 6 : 3 - - 1 4 (in Russian). Shachov, F.N., 1966. Princip formatsii v sistematike mestoroz - denii, sozdannych goryachimi rastvorami. In: V.A. Kuznetsov (Editor), Endogennye rudnye formatsii Sibiri i Dal'nego Vostoka. Nauka, Moscow, pp. 41--46. (in Russian). Shcherbakov, Yu.G., 1976. Geochimicheskaya evolutsiya veshchestva Zemli i endogennoe rudoobrazovanie. In: Yu.G. Shcherbakov (Editor), Zoloto i redkie elementy v geochimicheskich processacb. Nauka, Novosibirsk, pp. 14--33 (in Russian). Shcherbakov, Yu.G., 1979. The Distribution of Elements in the Geochemical Provinces and Ore Deposits. In: L.H. Ahrens (Editor), Origin and Distribution of the Elements. Pergamon Press, Oxford and New York, pp. 689--695. Shcherbakov, Yu.G., 1982. Komplexirovanie i uglublenie klassifikatsii pri analize dannych. In: Yu.A. Voronin (Editor), Teoriya klassifikatsii i analiz dannych. Vychislitel' nyi zentr Sibirskogo otdeleniya Akademii Nauk SSSR, N•vosibirsk, pp. 43--50.
481
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
LEGENDS OF GEOCHEMICAL MAPS
Yu.G. SHCHERBAKOV
Institute of Geology and Geophysics, Siberian Branch of Academy of Sciences of the U.S.S.R. Novosibirsk (U.S.S.R.) (Received January 9, 1984)
ABSTRACT Shcherbakov, Yu.G., 1984. Legends of geochemical maps. J. Geochem. Explor., 21: 481--486. Analysis of geochemical maps and their legends permits the proposal of several ways of improving their information content. Firstly, coherent and comparable classification of the objects to be presented must be developed. This classification should be based on strictly defined quantitative geochemical features of the objects; natural associations, anomalous elements, rocks, ore deposits and ore-bearing areas. Secondly, the most informative features of objects must be selected and uniquely displayed with a standard set of symbols. These symbols must be clear, readily understood and logically connected. The third requirement is that maps must be prepared in accordance with the tasks they are intended to deal with, must be optimally scaled, and display only appropriate information. One possible way of meeting the above-mentioned requirements, is proposed in a system of geochemical discrimination and related map presentation methods. The latter involves black hachures for the geological base, and directed colour lines and other features of colour hachures to characterize geochemical associations. Ore deposits may be characterized on the basis of eight most meaningful features encoded in one complex hieroglyph-like symbol constructed from easily understood and memorable components. This type of construction facilitates the computerized analysis of maps and makes them far more useful for prognosis, genetic reconstruction and resource evaluation.
INTRODUCTION
Geochemical maps reflecting the composition of geological entities are used for genetic reconstructions and for the prognosis, discovery and evaluation of ore deposits. The complexity of the information to be analyzed by geochemical mapping makes it essential to precisely define the task to be undertaken and to select an appropriate map scale at which the information can be best presented. Fersman (1953) c o m m e n t e d on the unsatisfactory dualism and lack of clarity of some geochemical maps because of the use of u n c o m m o n and uncoordinated principles in their construction that lead to the deformation of spatial patterns and their interrelationships. The analysis of maps at different scales, the different principles 0375-6742/84/$03.00
© 1984 Elsevier Science Publishers B.V.
482 underlying their construction and different symbols used reveals shortcomings that reduce the effectiveness of mineral resources evaluation. Firstly, the scale is often n o t in accordance with the tasks the maps are intended to deal with. On small-scale maps many minor details which cannot be compared with the basic information are often shown, and one cannot use these, but one can be misled by them. On the other hand, many maps are lacking basic geological information essential for anomaly interpretation. As a whole, these shortcomings m a y be recognized as incoherence of information. Another c o m m o n weak point is an over-complexity of symbols, the huge number of which makes them hard to remember and even harder to use for understanding the really essential interrelationships. One of the main, and commonest, weak points of n o t only geochemical, but also of metallogenic, prognostic, mineral resources, and other maps is incomparability of parameters presented, which decreases the value of data on ore deposits and host rocks. Ore deposits and host rocks are distinguished using different and unrelated principles and symbols. For example, the granulometric classification of sedimentary host rocks is often used as the only background for differentiation among ore-mineral associations, but, the most valuable details on the chemical composition of host rocks and ores are n o t compared, even if all the necessary information is available. This shortcoming results from incompatability in the underlying principles of classification of ore deposits, rocks, geological formations and chemical elements. For example, the geochemically similar chalcophile elements Pb, Zn, Cu, and Mo which are concentrated in c o m m o n sulphide minerals, differ on their contents in various rocks; Cu and Zn are concentrated more in basic rocks, and Pb and Mo more in acid ones. Accordingly, resources of the above-mentioned elements occur in deposits situated predominantly in basic and acid provinces, respectively. It is, however, impossible to get this information from the metallogenic and ore deposits maps because they do n o t reflect the quantitative distribution of these elements in rocks. Such incoherencies also occur in the legends of geochemical maps where they create difficulties in understanding the essential features of ore genesis and distribution and in the selection of areas for prospecting. The serious weakness of legends in all geological maps, including geochemical ones, is a lack of symbol uniformity for every definite quality of object. The colour code on one single map may be used for tectonic cycle designation, age of a set of rocks, composition of other sets and, most importantly, for some types o f ore deposits despite their relationship to different tectonic cycles or host-rock compositions. Such mixtures of meaning of even similar colours can only mask the possible relation among different patterns. Hachuring is widely used on maps, but the direction, thickness, and patterns of hachures often have no logic other than to try and make the map graphically pleasing. Named features are used randomly, making it difficult to remember them, and the possibility of the systematic
483
analysis of really meaningful qualities is completely lost. As the result the informativity decreases and interpretation becomes primitive. Geochemical maps do n o t achieve their possible potential as a tool for analysis and are an imperfect tool for geochemical data storage. The main challenge t o d a y is n o t in looking for new anomalies but in correctly interpreting the many thousands n o w known. Multimillion costs for discovering new mineral resources make improvements in the effectiveness of map presentation a very important international problem. We believe that improvements in the principles and methods of geochemical mapping and map analysis may play an important role in solving this problem. PROPOSAL
Taking into account the above-mentioned shortcomings o f geochemical maps some improvements are proposed. Initially, it is essential for many geochemical questions, from micro-scale regional surveys and prognosis to deposit depth and anomaly evaluation (Table I), to define the optimal scale of maps and their geological background. Table I demonstrates the main idea with relation to map scales and objectives. The relations between scale and legend size on one hand and scale and task (prognosis, search or evaluation) on the other, must be strictly defined in an optimal manner. To achieve that, the principles of object classification must be consistent with the manner of presentation of particulary meaningful features of ore deposits, anomalies, host rocks, underlying complexes of ore-bearing structure-formation zones if possible, etc. It is important to define the comparable features, of the objects, for instance, age, composition of associations, degree of spatial relation between the deposit and the sources of the ore elements, and mobility and other features of elements creating conditions for their c o m m o n concentration in deposits of different types. The objective is to develop and bring into accordance c o m m o n geochemical principles of classification of elements, minerals, rocks, ore deposits, geological formations, and areas of geochemical concentration, based on global features of elements distribution. These features may be defined quantitatively by the distribution coefficient among the main derivatives and initial systems, in particular the solar composition (0), carbon chondrites C1 (u), basaltoids (v) and clay shales (c). 0/u is the coefficient of volatility, v/~ is the oxyphility, and c/v is the siality. The high concentration of sialic elements (c/v > 1) in rocks, ores, and provinces leads us to assign them as sialic, and associate them with one colour in the legend, for instance, red, despite of the level of their complexity. The intensity of a colour may serve as an indicator of the degree of concentration for the sialic elements, being most intense in ores. Bringing consistency to every quality of object presented relative to the type of its manifestation will simplify legends and map analysis. This is a fundamental principle; legends must be simple
Whole Earth or continent
Ore province or belt
Ore cluster or zone
Ore and anomaly field
Ore deposit or anomaly
Observing 1:10,000,000
Forecasting 1:1,000,000
Prospecting 1 : 100,000
Follow-up 1 : 10,000
Mining 1 : 1000
Local forecasting to depth
Evaluation o f reserves (stocks)
Determination of ore fields and deposits resources
Selection of prospecting areas
Recognition o f global metallogenic patterns
Purpose of mapping
Main variations of ores and near-ore alterations
Ore deposits, occurrences, zones of alterations
Ore fields and deposits, their morphology, facies, age, etc.
Main ore province, belts, knots, zones, age of these
Features of ore deposits
Local peculiar- Morphology ity of rocks and composiand structures tion of orebodies
Lithology and petrography of rocks and their alterations
Suites, horizons, plutons, etc.
Geological formations o f 1--3 structure levels
Main tectonic structure and epoch
Geological background
Local distribution o f elements in ores and host rocks
Data of geochemical sampling, parameters of element distribution, including CC
Trends o f element distribution in all map units, aureoles
Geochemical types o f geological formations, aureoles ~ 5 km ~
Geochemical types o f main structure, complexes and provinces according to their femicity-siality
Geochemical data
CC (coefficient of concentration) is the average of anomalous contents/background.
Areas of geochemical mapping
Scales of maps
Recommendations for contents of geochemical maps of various scales
TABLE !
0v
485
and clear and the system used must be evident. As the simplest way to achieve this objective we propose a legend system which one need n o t refer back to repeatedly when analyzing a map. To illustrate the proposals let us turn to examples of application given in Table II. The geological background legend is omitted from further discussion because the use of black hachures in order to designate lithological and petrographical features of rocks satisfies our needs. The main geochemical compositional features of geological complexes, rocks, ores, and anomalies are coded in colour. Let the shift from the violet to the red part of spectrum reflect the increase of an object's siality, that is from ultrafemic--violet to ultrasialic-orange; femic is green and an intermediate composition is brown. It is convenient to use orientation of symbols, even of broad colour hachures, to indicate the age of all geological entities including ore deposits on the small- and medium-scale maps. The clockwise turn of orientation of symbols TABLE II Examples of recommended legends for geochemical maps Properties of objects to be mapped
Means of representation
Examples
Geochemical type~ : f= femic; s=sialic; o--oxyphile, oxygen; h=heterophyle, heterogen; v=volatile
Colour
f=green; s=red; fs-brown; h--blue; o=yellow; fh=violet; so=orange sh=crimson; v=azure; vs=deep red; vf=aquamarine
Coefficient of concentration
Intensity of colouring
minimum=clark background middle coloured=positive halos maximum=ore concentration
Coefficient of variation
Interruption of hachure
I I = low D [Z3 [Z] = high D [] [] DD = extremely high
Morphology of orebodies
F o r m of symbol
I
Distance from sources and facies of ore deposits; r=base, re=middle, a=apex
Place of shade in symbol; (blank; telescoping type = t)
Age
Direction of coloured hachures and symbols
)
= stratiform vein = complex =
~ ~ ~ ~
= = = =
small (r) middle (m) large (a) telescoping (t)
c\ b ~ \
hd \
~ f
a I
Shcherbakov, 1976, 1979, 1982). a = Precambrian; b = Proterozoic; c = Caledonian; d = Variscan; e = Mesozoic; f = Cenozoic.
486
indicates a decreasing age. The use of 3-mm-wide hachures with 3-mm intervals permits the coding of up to three geochemical structural phases. This way of presenting information creates a useful range of geochemical spatial patterns with potential for describing many features. The interruptions on hachure lines are useful for indicating the magnitude of variability in element distributions. The system significantly improves the characterization of geochemical anomalies on large-scale maps. The following features of ore deposits seem to be most important for systematic analysis, and hence must be well represented on geochemical maps: orebody morphology, genesis, geochemical type, association of the most concentrated elements, degree of spatial separation from the source (low, medium, high, variable), age, dimensions, and summary characteristics of the formation type (Shachov, 1966; Kuznetsov, 1972). All eight features are easily coded by one symbol (hieroglyph constructed of simple components), which indicates the morphology of ore bodies; width of contouring line shows genesis, colour codes show geochemical type of deposit or group of most concentrated elements, and location of shade in the symbol indicates the deposits position relative to the source of the elements (Table II). The orientation of the symbol always indicates age and the size will reflect the industrial significance of the deposit. Chemical indexes of predominant elements in ores may underline their oreformational characteristic. The main advantage of such combined, or "hieroglyphic", representation of ore-related objects is that it opens the possibility for composition, structure, age and position analysis. Especially, it allows the relation of the same and similarily expressed features of host and sometimes underlying rocks, such as their composition, genesis, age and so on to be easily displayed. The future development of the proposed legend system is possible only by the concerted efforts of many specialists concerned with the improvement of geochemical maps and their interpretation. REFERENCES Fersman, A.E., 1953. Geochimicheskoe kartirovanie. Izbrannye trudy, t II. Izdatel'stvo Academii Nauk SSSR, Moskwa, pp. 556--559 (in Russian). Kuznetsov, V.A., 1972. Rudnye formatsii. Geol. Geofis., 6 : 3 - - 1 4 (in Russian). Shachov, F.N., 1966. Princip formatsii v sistematike mestoroz - denii, sozdannych goryachimi rastvorami. In: V.A. Kuznetsov (Editor), Endogennye rudnye formatsii Sibiri i Dal'nego Vostoka. Nauka, Moscow, pp. 41--46. (in Russian). Shcherbakov, Yu.G., 1976. Geochimicheskaya evolutsiya veshchestva Zemli i endogennoe rudoobrazovanie. In: Yu.G. Shcherbakov (Editor), Zoloto i redkie elementy v geochimicheskich processacb. Nauka, Novosibirsk, pp. 14--33 (in Russian). Shcherbakov, Yu.G., 1979. The Distribution of Elements in the Geochemical Provinces and Ore Deposits. In: L.H. Ahrens (Editor), Origin and Distribution of the Elements. Pergamon Press, Oxford and New York, pp. 689--695. Shcherbakov, Yu.G., 1982. Komplexirovanie i uglublenie klassifikatsii pri analize dannych. In: Yu.A. Voronin (Editor), Teoriya klassifikatsii i analiz dannych. Vychislitel' nyi zentr Sibirskogo otdeleniya Akademii Nauk SSSR, N•vosibirsk, pp. 43--50.