Generally speaking, the establishment of geochemical prospecting model describes the regularity of geochemical field system and its influencing factors as multi-level and multi-correlation. Specifically, it is to study and expound the regularity of geochemical fields of ore-forming objects (ore bodies, ore deposits, ore fields, ore nodules, ore-forming areas or ore-forming zones) at different levels, so as to achieve the purpose of guiding prospecting and geological research.
(1) geochemical prospecting models with different orders and their basic ideas.
1. Theoretical basis for establishing geochemical prospecting models of different levels.
In the early 1990s, Russian scholar вмпитулько (1990) clearly pointed out that the real scientific basis of geochemical survey is the systematic concept of natural classification in metallogenic system, which is the basis of geochemical survey. The geochemical field shows an orderly and regular multilevel structure in space and statistics. Specifically, there are similarities in geological geometry and geochemical characteristics of deposits of the same genetic type and different scales (Figure 4- 14).
Fig. 4- 14 Geometric characteristics of different levels of metallogenic objects and their relationships (quoted from апсоловов,1985; Quoted from аакременецкий, 2009, the volume ratio (A: B: C) of ore-forming objects is 65438+. (b) s = 4。 64，V = 10； (c) s = 2 1。 5，V = 100
According to this principle, the geological-geochemical model can be used to predict the potential of mineral resources, which can quantitatively predict the resources in different stages of geological exploration. Because the metallogenic systems of different orders of objects have corresponding concepts of three-dimensional abnormal geochemical fields. Under this condition, the regularity observed from the geochemical field structure should be related to the geological-structural location characteristics of unknown objects, the banded (non-banded) distribution of ore-forming materials, and the performance and composition characteristics of regional and near-ore metasomatic rocks. In these models, the abnormal field of a certain order object should be regarded as a complete system with characteristic internal structure, but with spatial differentiation. Conversely, this system is a part of the abnormal geochemical field of a larger object, and it also contains the abnormal geochemical field of a smaller object. Different levels of ore-induced geochemical anomalies have similar characteristics and spatial causes. This relationship is also reflected in its internal structure and composition, and depends on the unified mineral distribution mechanism in different metallogenic stages (Figure 4- 15).
In recent years, the Russian Institute of Mineralogy, Geochemistry and Crystallization of Rare Elements (имгрэ) has developed a set of techniques and criteria for screening abnormal geochemical fields of different metallogenic objects based on different geological-geochemical prospecting models, and obtained.
2. Characteristics of geochemical prospecting models with different orders
Based on the above analysis, geochemical research must follow the principle of regional to local interpretation, attach importance to revealing ore-controlling geological factors from regional geochemical background, and attach importance to studying different levels of geochemical prospecting models from regional perspective.
According to Wu Chuanbi (199 1), in the 1980s, the former Soviet Union summarized the geochemical model characteristics of three different levels of ore fields, deposits and orebodies for five types of 17 gold deposits in its territory (Table 3-7). аакременецкий (2009) discussed the characteristics, scale and marks of geochemical anomalies of different levels in a wider scope (Table 3-).
1) geochemical field of metallogenic area (geochemical area): the scale can reach hundreds to thousands of square kilometers. Their distribution range includes geological structures or large blocks that are beneficial to mineralization. It is characterized by block structure and relatively low contrast. It is necessary to divide this geochemical field and have a special method to study its composition and enhance the weak geochemical signal.
Fig. 4- 15 sequence of systematic identification and evaluation of geochemical field prediction resources by different geological-geochemical prospecting models (quoted from аакременецки)
2) Geochemical field of ore deposit (ore field): The scale ranges from 1km2 to 10 ~ 70 km2, occupying some blocks and marginal parts of large-scale metallogenic system. Their structure depends on the combination of abnormal blocks with different scales, different chemical compositions and different contrasts, which reflects the structural-geochemical framework characteristics of the metallogenic system. In this magnitude geochemical field, real ore-forming blocks appear alternately with a large number of scattered mineralization zones and weak reformed geochemical fields.
3) Geochemical field of ore body (ore belt): It is a relatively local section in the geochemical field (1 × 104m2 to (10 ~ 50 )× 104m2), with extremely uneven structural differentiation, high contrast and good continuity in dense areas, usually.
The Russian Institute of Rare Element Mineralogy, Geochemistry and Crystallization Chemistry has fully studied pyrite-type, porphyry copper-type and gold-silver-type metallogenic objects at all levels, which can be used as an example to screen abnormal geochemical fields. For example, according to the geochemical standards shown in Table 3-3, all geochemical fields of the porphyry copper system can be delineated conveniently and reasonably.
3. Research tasks of geochemical models with different orders
Aiming at establishing different geological and geochemical prospecting models, аакременецкий (2009) includes ore bodies, primary halos, secondary halos and dispersed flows.
1) In the geochemical survey of ore bodies based on primary halo, the elements and parameters of prospecting model are the main indicators, and the following problems need further study: near-ore alteration and alteration zoning related to endogenous mineralization; Geochemical zoning of different ore-bearing sediments, magma and metamorphic rock series; Comprehensive mineralogy-petrology-geochemistry method is used to identify and explain petrochemical anomalies (including rocks, soils and river sediments).
2) To study the geological and geochemical prospecting model of ore deposits in the system of ore body+primary halo to secondary halo, the problems that need further study are: the division method of abnormal geochemical field of ore field and ore body (the lower limit value of different minerals and its changes with different landscapes and methods); Methods for dividing mining areas and ore nodules by abnormal geochemical fields (including methods for determining abnormal values of geochemical fields and criteria for evaluating ore-induced anomalies); Radial-concentric geochemical zoning and other types of sources, as well as signs to identify the zoning of covered metallogenic objects; A reliable method to study and evaluate the contents of chemical elements in residual halo and upper halo (during sampling and sample preparation); The transformation model of ore-forming materials in the ore body-erosion surface-secondary halo system and the method to determine the quantitative relationship of these changes.
3) To study the geological and geochemical prospecting model of the deposit from ore body+primary halo+secondary halo to dispersed flow system, the following problems need to be further studied: screening and evaluation criteria of geochemical anomalies in dispersed flow; Optimal grid for decentralized flow sampling: Methods that can reliably evaluate and improve the geochemical signal level of dispersed flow (in sampling and sample processing); Mechanism of geochemical signal conversion in bedrock+secondary halo system and its conversion to dispersed flow.
To reveal the essence of geochemical fields of different orders, it is obviously not enough to study only the combination and content level of elements. The occurrence form, correlation and variation characteristics of elements are the essential characteristics of geochemical field, and their performance characteristics are different at different orders, so we should pay enough attention to the establishment of geochemical field models of different orders.
(2) Regional geochemical prospecting model and mineral resources potential prediction.
Regional geochemical data is one of the reliable basis for predicting regional mineral resources. In 1970s, the famous geochemist апсолововов put forward a mathematical method to estimate the amount of metal resources in the region by using geochemical data of soil and river sediments, and later developed and perfected the term "geochemical model for general survey and evaluation of metal minerals". Its basic principle is that the area productivity (P') of river sediments (dispersed flow), the corresponding coefficient (K 1) of dispersed flow and secondary halo (soil measurement result) and the corresponding coefficient (K2) of secondary halo and primary halo (rock measurement result) can be obtained according to the measurement data. A certain depth (h, depending on the type of deposit to be predicted) in the investigation area can be determined by
Q = P' / ( K 1K2 40) h
After obtaining the Q value, the proportion of the number (n) of large, medium and small deposits that can be found in this area can be further demonstrated according to the calculation; That is, n is large: n is medium: n is small = 1: 7: 49. According to the scale and quantity of discovered deposits, the number of projects that can still appear in this area is calculated in advance. Later, апсоловов put forward the scale (volume) relationship diagram of different shapes (vein, plate, lenticular, reticulated vein, equiaxed, etc.). ) and orebody extension (Figure 4) It is said that the correctness of this explanation has been confirmed by the satisfactory agreement between the calculated predicted resources and the calculated industrial reserve.
Although this method proposed by апсоловов has been widely used in the former Soviet Union, and was included in the "Standard for Geochemical Exploration of Solid Minerals in the Soviet Union" promulgated by 1982, it has been supplemented and revised in recent years, and named as "Model". According to the formula, it is based on the data (area productivity) higher than the background value, so it is impossible to describe a meaningful model in the background field. It deals with the data of a single element, ignoring the distribution patterns of various elements and their relationships, so it will not fully reflect the reflection of mineralization in geochemical fields. However, the role of this calculation model in regional metallogenic prediction can not be ignored.
Figure 4- 16 Relationship diagram of ore bodies with different scales and approximate shapes (quoted from апсоловов, 1987)
A comprehensive analysis of the elemental characteristics of ore bodies, primary halos, secondary halos and dispersed flows can usually reveal the formation law of these objects, develop geological and geochemical models of ore deposits, determine the order and methods of interpreting geochemical data, determine the criteria for evaluating and screening anomalies at different scales, and determine the resources. In this paper, the work in polar Urals and near polar Urals (вюскрябин, etc.) is taken. , 2009) as an example to further illustrate this research idea.
According to the landscape environment of polar Urals and near polar Urals and the task of searching for chromium ore in alpine ultrabasic rocks, it is found that there is a negative correlation between Cr and Ni in chromium ore (correlation coefficient r =-0.56；; Confidence p = 0. 99), but in their primary halo, these two elements have a weak positive correlation (r =0. 33，p =0。 95) and form a combination of Cr-Ni-Ti-Cu. In the ore field where the two ore blocks are located, the combination of Cr, Ni, Co, Mn and Zn is stable and highly positively correlated (r = 0. 3-0.6，p = 0。 95-0.99) is observed in loose sediments and dispersed flows above the ore belt. During the transformation from primary halo to secondary halo, the originally separated Ni and Cr converged into the same combination, perhaps due to the supergene activity of particles in the loose layer.
On the basis of the above geochemical model, the resources of chromium ore are calculated by using the results of dispersed flow and secondary halo investigation in different stages of geochemical exploration, and compared with the resources calculated according to the sampling data of exposed ore bodies. The resource prospect of this area is predicted (Table 4- 1).
The calculation results (Table 4- 1) prove that it is difficult to compare the predicted resources based on geochemical anomaly results with the real resources when implementing "1∶ 200,000 geochemical work plan" (O г XP-200). They may not only lead to high resources (western section), because the area involved in the calculation exceeds the area of the catchment directly flowing through the deposit, but also reduce the resources due to the dilution of riverbed sediments brought by distant materials.
According to the secondary halo of1∶ 50,000 work, the predicted chromium ore resources are also on the high side (Table 4- 1), but the high level is obviously reduced. In this case, the reason for the high ratio may be that not only the anomalies caused by ore, but also the rock anomalies and mineralization anomalies of poor chromite which have no industrial significance are included in the calculation. The reduction factor calculated according to the actual resource quantity of the studied ore section is between 1.6 ~ 2.6. When the working degree is increased to the scale of 65,438+0 ∶ 65,438+0,000, the resources calculated based on geochemical data can be completely compared with those obtained by sampling exposed ore bodies (Table 4-65,438+0).
Table 4- 1 Evaluation of Chromium Ore Resources
Source: вюскрябин et al., 2009.
Note: the analysis is approximate quantitative spectral analysis; S- abnormal area; C Ф, Cmax, CCP-background content, maximum content and average content of chromium; P = (Ccp- Cф) × S, which is the abnormal area productivity; H—— evaluation depth; α -mineral coefficient in the table (parts); K —— Residual metal coefficient of secondary halo minus primary halo; K'-residual metal content coefficient of secondary halo reduction by dispersed flow; The calculation of the predicted resources obtained by г XP-200: qcr = p× h×1/29× α×1/k×1/k'; Calculation of predicted resources obtained by дзр-50 and дзр- 10: qcr = p× h×1/29× α×1/k.o г xp. дзр-50—1∶ 50,000 geochemical work; дзр-10-1:1ten thousand geochemical work. P 1 and P2 are forecast resources.
Regional geochemical data is one of the main bases for dividing regional metallogenic prospects. The relationship between ore-forming provinces and geochemical provinces can be summarized into three situations: ① the geochemical provinces and the ore-forming provinces overlap and couple, and most of the known deposits are located in the geochemical provinces at this time; ② There is no metallogenic province in geochemical province. Although there are large areas and high contents of ore-forming elements, they are characterized by dispersed mineralization, and no deposits are formed or only a few deposits are produced. (3) Where there is no geochemical province, metallogenic areas have been formed and some smaller deposits have appeared. The relationship between metallogenic areas and geochemical provinces is very complicated, which is not a simple one-to-one correspondence, but also more complicated due to the limitation of geological work and exploration degree. Therefore, in the study of regional geochemical prospecting, we should attach great importance to the study of geochemical provinces. Shi Junfa et al. (2004b) summarized the related problems in the study of geochemical province, and the main points are summarized as follows:
1) The concept of geochemical province has different understandings, but it is basically the same. Zhao et al. (1988) summed up the views of Russian scholars, and thought that "the tectonic units with the same geological and geochemical evolution characteristics show the same geological body combination, and the mineral deposits formed by endogenous and exogenous processes and the enriched element combination are also the same"; Or the geochemical province defines it as "a large-scale crustal unit has the same geological and geochemical evolution characteristics, which is characterized by the same chemical composition of geological bodies and the same enrichment of endogenous and exogenous metal elements and nonmetallic elements". Geochemical province exists objectively, and it is the geochemical manifestation of geological units of the same origin and a certain scale that occurred during the evolution of regional lithosphere.
2) The relationship between geochemical provinces and metallogenic provinces is very complicated, not a simple one-to-one correspondence. A large number of foreign data show that hydrothermal deposits with crustal abundance higher than 10-6 (such as Cu, Pb, Zn and Ba) do not need to be pre-enriched, that is, they do not need to form geochemical provinces. For "rare" elements whose crustal abundance is lower than 10-9, such as Sn, Ag, Hg, etc., it is necessary to pre-enrich them before extraction to form ore deposits, that is, to form geochemical provinces.
3) Geochemical provinces and their boundaries are closely related to geological tectonic units. In essence, the geochemical province should not be determined by the anomaly range delineated by a certain anomaly lower limit, but should be determined by combining the tectonic-geological boundary; Geochemistry should be analyzed from the combination-distribution relationship of several groups of elements with the same properties, rather than defined by the distribution of one element. The boundary of geochemical province can be divided according to its * * * biological element combination-distribution area. Without the concept of combination-distribution, geological processes may be ignored and geochemical data cannot be combined with geological evolution. Zhu Bingquan (200 1) thinks that geochemical anomalies can't be used to delimit geochemical provinces. In fact, he has considered the thickness of geochemical provinces (blocks) and the changes in their three-dimensional space. The understanding and interpretation of geochemical provinces (fields) should actively reveal the essence of geological processes and revise and deepen geological understanding.
4) Geochemical province exists objectively and should not be affected by the delineation method. For a region, the degree of exploration should not affect the objective existence of ore-forming provinces and geochemical provinces, but the degree of regional mineral exploration greatly affects the understanding of a regional ore-forming province, so the existence of ore-forming provinces can only be determined after finding a series of deposits. At present, geochemical provinces (or regions) are usually delineated by regional geochemical survey results of river sediments at home and abroad. In an area, if the deposit is deeply buried, the surface geochemical anomaly may not be obvious, even the geochemical province is not obvious, but the existence of geochemical province can never be denied. For example, in some thick coverage areas, traditional geochemical exploration methods can not delineate geochemical blocks, but deep penetration geochemical methods are used to delineate large-scale geochemical blocks. Just because geochemical blocks are not delineated by traditional geochemical methods, the existence of geochemical provinces in this area cannot be denied. Similarly, if the ore-forming materials come from the deep upper mantle rich in ore-forming elements, rather than from the surrounding rocks, it is difficult for traditional regional geochemical exploration methods to delineate geochemical provinces.
(3) Geochemical prospecting model and local investigation and exploration.
The local geochemical prospecting model is basically based on the primary geochemical zoning sequence model (or "primary halo" model for short), and it is constantly expanding and developing. Compared with the regional geochemical model, the geochemical prospecting model of local survey exploration has a higher degree of research, wider application scope and better effect.
In 1960s, Xie et al. (196 1) put forward the three-dimensional geometric model and chemical model of primary halo in Qingchengzi lead-zinc deposit. Shao Yue et al. (196 1) began to study the primary halo zoning model in 1960s, and summarized the vertical zoning sequence model of hydrothermal deposits based on temperature in 1975. With the development, perfection and application of a series of deposit research, Li Hui et al. (1998) systematically summarized the primary halo superposition model for blind ore prediction of large and super-large polymetallic deposits, put forward five prospecting indicators (4- 1 column), and achieved practical results in deep prospecting of several crisis mines.
Almost at the same time, the famous Russian geochemist C.B. григорян (1992) systematically studied a large number of geochemical zoning models of primary halos in hydrothermal deposits, and put forward the horizontal and axial zoning sequence of elements in hydrothermal deposits, which was studied by geochemical prospecting models. There are several reasons: first, the research method of combined halo, namely, cumulative halo and the compilation method of cumulative halo, has been developed and established, which not only suppressed noise interference, highlighted the main law, but also integrated different elements to meet the requirements of modeling methods; Secondly, the axial, longitudinal and transverse zoning of the primary halo of the deposit are found out, and their different genetic mechanisms and different application characteristics are explained. The approximate zoning order of the three zoning is discharged by statistical method. Thirdly, a set of standardized methods for sorting out the element zoning sequence of a specific deposit, calculating the zoning coefficient and compiling the corresponding chart are put forward, and a computer program is compiled, so that the data obtained from different regions and the processing results can be compared and analyzed; Fourthly, a set of criteria for determining the depth of erosion profile, eliminating dispersed mineralization zones and distinguishing multi-structural halos has been established, which has been proved to be feasible by a large number of practices, making the primary halo model of ore bodies and deposits a widely used and effective basis for prospecting, especially for finding concealed ore.
In particular, the primary halo model of the deposit is not a simple element zoning model, but contains profound connotations of the genesis, mineralization and mineral geochemistry of the deposit. The laws revealed by the model and the corresponding methodology established are not only applicable to the interpretation of primary anomalies and the study of a certain type of single deposit (body), but also to the interpretation of various secondary geochemical anomalies and the study of various deposit types and metallogenic objects related to hydrothermal fluids in a wider range. According to the literature in recent 20 years, the establishment and perfection of most local investigation models of ore deposits are based on the primary halo model, at least it is one of the important bases for establishing models (including geological models).
Column 4-1 Five criteria for finding large and super-large gold deposits by using superimposed halo model
According to the decomposition and synthesis characteristics of superimposed halos in large and super-large gold deposits under different conditions, five criteria for finding blind ore and judging the degree of gold erosion by using superimposed halos are summarized:
(1) When the anomalous intensity of Au is low, if there are strong anomalies of characteristic leading edge halos such As Hg, As, Sb, B, I, F and Ba in the inclusions, or abnormal leading edge halos and ion halos such as CH4, CO2, F- and Cl-, it indicates that blind ore exists in the deep.
(2) When the content of Au is very low (less than a few grams per ton), if there are strong anomalies of characteristic tail halo elements such as Mo, Bi, Mn, Co, Ni and Sn, or anomalies of characteristic tail halo ions such as Ca2+ and Mg2+ in inclusions, it indicates that there is no ore in the deep.
(3) Anti-zonation criterion: When calculating the vertical zoning sequence of primary halo of gold deposits, there is an "anti-zonation" or abnormal phenomenon, that is, typical halo elements such As Hg, As, Sb, F, I, B and Ba appear in the lower part of zoning sequence, or F-, Cl-, CO2 and CH4 in the axial zoning sequence of inclusion geochemistry appear in the lower part, indicating that there is blind ore in the deep or sub-enriched middle part. If the ore body itself is not pointed out, it shows that the downward extension of the ore body is still very large.
(4) *** Survival criterion: there are strong anomalies of lead halo elements such As Hg, As, Sb, F and B in the ore body and its primary halo, and there are strong anomalies of trailing halo elements such as Bi, Mo, Mn, Co and Ni or lead halo, ion halo and Ca2+ and Mg2+ in the inclusions.
(5) Inversion criterion: When calculating the geochemical parameters (ratio or cumulative ratio) of ore bodies or halos, if several elevations continuously rise or fall, they suddenly reverse, that is, from falling to rising, or from rising to falling, indicating that the ore bodies extend deeply downward or there are blind ore bodies in the depth.
The above five standards can be used alone or in combination. Primary superimposed halo, inclusion gas halo and ion halo can be used separately or simultaneously, and several marks or criteria are more accurate.
Quoted from Li Hui et al. (1998)
In the study of primary halo, it is possible to objectively and quantitatively evaluate the parameters of abnormal structure of geochemical field only by adopting strict and standardized expression methods for its geometric shape. Because there are various methods to solve this problem, the results obtained by different authors will be incomparable, so a unified method must be formulated according to some standardized indicators. In this respect, the study of вгварошилов hydrothermal gold deposit (2009) can be taken as an example.
In the evaluation of deposit scale, he adopted the index and method of metallogenic energy. He believes that the zoning of abnormal geochemical field of hydrothermal gold deposits is firstly characterized by the polarization of rich elements and divergent elements. These two groups of elements are related to the formation conditions of the deposit and can be determined by the classification of abnormal structures. Theoretically, the rank correlation coefficient куп between elements is infinite, but in fact, for the middle part of the ore body of the studied large-scale deposit, its value does not exceed15 ~ 20; And with the pinch-out of the ore body, the value will drop to an insignificant level. The author uses these two groups of related elements within the scope of the deposit to estimate the scale of the deposit. They found that the scale of mineralization to be discovered is a function of the total ore rate (total metal content) of hydrothermal process, which can be expressed quantitatively by the metallogenic energy index (H.H. сарооов, 1978):
е=σKKi ln(KKi)
Where KKi is the concentration coefficient of each element. According to the investigation, this coefficient is equivalent to the concentration Clarkki in the original literature of H.H. саронов, and the meaning of this index reflects the total material balance of each sampling point. Therefore, it is best to calculate concentrated elements and divergent elements separately. For each of these two indicators, the background value, the lowest abnormal value and the amount of metal in the abnormal structure of geochemical field (in this example, the area productivity is used) should be calculated. When estimating the scale of mineralization, the quantity of е concentrated metal and е dispersed metal should be regarded as two independent indexes, because they reflect different aspects of the same process. According to experience, the difference between the concentration and divergence of E is 1 ~ 2 orders of magnitude, which is directly proportional to the amount of gold resources in the abnormal structure of geochemical field of corresponding orders of magnitude. Drawing on the logarithmic scale, this relationship can be well expressed as a straight line, so the scale of mineralization to be identified can be estimated (Figure 4- 17). As can be seen from the figure, for the enriched elements, the fitting lines of geochemical fields of different orders are convergent, which reflects the high degree of mineralization enrichment of large and super-large deposits. The metal content of dispersed elements depends largely on the order (area) of geochemical field, which indicates that these elements are taken from surrounding rocks. The correlation between the redistribution scale of dispersed elements and the composition of ore-bearing rocks can also prove this point, especially in the abnormal geochemical field at the ore field level.
Fig. 4- 17 Relationship between gold mineralization scale and metallogenic energy index: (a) Enriching (metallogenic) elements; (b) Different elements (quoted from вгворошилов, 2009)
The officially recognized method (C.B. гржжов) A. is adopted to estimate the grade of mineralization alteration profile. However, it is more complicated to use this method in gold mines, because the three-dimensional zoning of ore pillars often has the characteristics of centripetal, so the zoning coefficient also shows the characteristics of changing with depth stratification. Figure 4- 18 takes a gold-bearing skarn-magnetite deposit in Kazakhstan as an example, showing the typical situation that the quantitative characteristics of abnormal structure of geochemical field change with depth (expressed by the area productivity of corresponding parameters in each horizontal middle section). It can be seen from the figure that the maximum values of metallogenic energy, grade correlation coefficient, accumulated halo of enriched elements and accumulated halo of divergent elements appear in the middle section where the ore body is located; At the same time, the maximum value of Co/Ni ratio is located in the middle and lower part of the mine, while the maximum values of Pb/Zn ratio and Ba+Mn accumulated halo appear in the middle and upper part of the mine. For the dispersed mineralization zone, the variation of metal content of each geochemical index with depth is not obvious and irregular, as shown in Figure 4- 19. At the same time, the total enrichment level of dispersed elements is equivalent to that of industrial ore bodies, indicating that the hydrothermal system has high enough energy potential. However, in the unfavorable tectonic environment, the fluid is not concentrated, and the ore-forming (enriched) elements and divergent elements are uniformly dispersed in a large volume, forming an abnormal geochemical field with high concentration and zoning. Therefore, the rank correlation coefficient will not exceed the limit of statistical significance level in any part of the structure.
Figure 4- 18 Variation of abnormal structural parameters of geochemical field with depth in a gold mine in Kazakhstan (quoted from вгворошилов, 2009).
Fig. 4- 19 Variation of abnormal structural parameters with depth in dispersed mineralization zone of a mining area in Kazakhstan (quoted from вгворошилов, 2009).
The estimation of erosion profile at ore field level is an independent subject. Only when the zoning direction is close to the horizontal, it is possible to study the axial zoning of this section on the standard object. However, this situation is rarely encountered, and in most cases it is the cross section of hydrothermal system. To restore the vertical zoning of ore field, we must rely on its fragments or adopt the principle of analogy. The research shows that the underground profile and the upper profile of the ore field are similar to a series of parameters of the abnormal structure of geochemical field (rank, metallogenic energy, spectrum of enriched elements and abnormal structure shape), but there are also some differences. Under the condition that the whole set of concentrated elements is still stable, their ratios will change regularly during fluid infiltration. Therefore, for the front area of the ore field, the Pb∶ Zn ratio is characterized by positive anomaly, while in the root area, the anomaly development is weak. On the contrary, there are usually Co∶ Ni anomalies in the root zone, but not in the front zone. Another characteristic of the root zone is that the concentrations of Co, Ni, Cr and V in metasomatic rocks and sulfides are relatively high.