Prediction of the mineral components spatial distribution in tailings ferruginous quartzite enrichments

In Ukraine, a significant mass of potential man-made deposits is represented by waste from ferruginous quartzite enrichment. The mineral mass of such deposits is mixture of iron-containing minerals (magnetite, ilmenite) and quartz. The M.S. Poliakov Institute of Geotechnical Mechanics has developed a new methodology for the mineral components spatial distribution predicting in tailings of ferruginous quartzite enrichment. It includes the fractional and mineralogical composition of the samples study by optical method, and spatial useful components distribution of prognostication in waste and predictive plans construction for the useful components spatial placement. A previously unknown pattern of changes in mineral composition of wastes from mining ore production was revealed which caused by the turbulent transportation mode and waste deposition on the tailing (potential man-made deposit) area. This regularity arises from the fact that with decrease in the size of the mineral components particles with size of 0-200 microns, the share of the magnetic mineral magnetite increases linearly and, accordingly, the share of the non-magnetic mineral quartz decreases. The obtained new properties of man-made deposits from the waste (tailings) can be used in creation of resource-saving technology for the iron ore man-made raw materials processing and to determine their suitability for mining.


Introduction
The bulk of the mineral components that make up man-made deposits are of a mixed type.They are waste from quarries enrichment and mines of mining enterprises.Waste in the form of pulp enters the sludge pipelines to storage sites tailing, where, after draining the liquid phase (water), they create layerlike deposits, that is, potential man-made deposits.These deposits usually consist of finely dispersed particles, the size of which ranges from 2 to 400 microns.
Accumulation of waste from enrichment factories of the mining industry is accompanied by a number of problems.These are the limitations of the accumulative capacity of tailings, the complexity of calculating mineral losses, the determination of the of associated useful components presence, the manmade deposit boundaries definition and the features of the man-made raw materials processing and the geomechanical stability of existing structures, etc.
According to the classification [1], there are several types of man-made placers in Ukraine that can be mining, namely: iron ore tailings (500 million tons) for processing into iron and gold (up to 4 gram/tones); manganese ore waste (150 million tons); alumina red slime (1.2-1.3 million tons) containing grains of gold, zircon and rutile; tailings of titanium ores for processing into gold (5-6 gram/tons); kaolin waste that can be processed into monazite concentrate.In the world, a lot of attention is paid to the issue of determining the tailings accumulative capacity, their residual capacity and recovery options.The author [2] investigated the interaction of disturbed and man-made massifs with the natural geological environment and proved that this leads to the development of negative processes in the structures of tailings storage facilities.As a result, it is concluded that it is better to mine storage tanks instead of building dams.In work [3], technical solutions for re-excavation of man-made mass or clearing are proposed, and technological schemes are developed.The authors made a justified decision to reduce the man-made load by reducing the area of the territories under the sedimentation tanks.The authors [4] proposed the technology of infusing pre-lightening pulp in alluvial maps with subsequent thickening and storage in the form of highly concentrated pulp at the bottom of the pond.But these works do not reveal the contents and value of the tailings deposit as a technological deposit.
Many works concern options for the processing of man-made raw materials.The work [5] presents the results of research on the technological parameters of man-made deposit mining, namely the determination of the optimal value of the ore mass movement step.The development of the equipment of the technological complex in the conditions of a dynamic environment is disclosed in the following work of the authors [6].Parameters of enrichment waste hydraulic transport and features of handling particles in a turbulent state are given in [7].The paper [3] substantiates the possibility of processing water man-made raw materials.When processing man-made raw materials, the main problem is the processing of the fine fraction.The author [8] proposed a new way of processing a wide range of grain sizes, when it is necessary to separate fine classes (usually substandard product) and to degrade the finished product as much as possible.Paper [9] provides physic-chemical methods of processing manmade raw materials, while paper [10] suggests using traditional magnetic hydro separation instead of deslamation.
The process of developing a man-made object, extracting lost useful components and using waste to restore the meso-relief is disclosed in [11].Similar studies were carried out by the authors [12,13].Manmade raw materials after processing can be used as building material, including for backfilling the produced space of quarries.
The article [14] emphasizes that tailings are suitable for obtaining iron ore concentrate, and some fractions enriched with rare earth and biogenic elements can be used as additives to increase the fertility of podzolic soils.
The analysis of existing tailings storage technologies allowed the authors [15] to substantiate the layered structure of accumulation of man-made raw materials.It has been proven that man-made deposits are formed by layers of hydro basket of the same thickness, displaced relative to each other in the horizontal plane by the same amount.It should also be noted [16] that, depending on the depth of the layer, the content of waste varies in a wide range from 10 to 64 %.
Thus, the main mass of potential man-made deposits is waste from the enrichment of ferrous quartzites, so the mineral mass of these deposits is a mixture of iron-containing minerals (magnetite, ilmenite) and quartz [17].A small amount of pyrite, marcasite, minerals of the carbonate group and mica are present.Currently, geological exploration organizations use spectral and chemical analyzes to determine the content of iron-containing minerals, quartz and other secondary mineral components.The specified methods of mineral composition research require the use of expensive laboratory equipment for chemical analysis, as well as a spectrograph with quartz optics, an optical quant meter, etc.Although spectral and chemical analyzes make it possible to determine the quantitative values of the content of iron, silicon dioxide (quartz), aluminosilicates and other elements in the studied samples with fairly high accuracy, using these expensive methods it is impossible to perform an overall assessment of the fractional and mineralogical composition of the man-made deposit.It should be noted that it is the mineral particles granulometric characteristics (quartile and average sizes, sorting coefficients and asymmetry) contained in the pulp that significantly affect the process of its transportation from the lower end of the slurry pipeline and a certain distribution of useful components (iron-containing minerals and quartz) in space and as a result, on the formation of a potential man-made deposit over time.
Regardless of the large amount of work performed within the scope of the research, the issue of determining the man-made deposit, spatial distribution of useful components and determining their concentration limits, etc., remains relevant.Therefore, the purpose of the work is to develop a methodology for predicting the distribution of mineral components within the limits of the tailings storage facility for the preservation of iron ore industry enrichment waste.

Methodology for studying the fractional and mineralogical composition of mixed type mad-mane deposits
In the M.S. Poliakov Institute of Geotechnical Mechanics of the National Academy of Sciences of Ukraine has developed a new technique for optically determining the granulometric and mineralogical composition and content of useful mineral components that accumulate in tailings during the arrival of the pulp with enrichment waste at their storage sites.
It includes the selection of the studied sample on the area of a potential man-made deposit according to a certain scheme, the separation of the prepared and dried sample into fractions on laboratory sieves, separation of the magnetic component of the sample using a powerful magnet, study of the finely dispersed mineral particles content in the field with a polarizing microscope in transmitted light.
Samples weighing from 1 to 5 kg were used as material for the study of the granulometric and mineralogical composition of finely dispersed particles (fractions from 0 to 400 microns), followed by the determination of the mineral content, taken from the site of the discovered man-made deposit.
The distance between sampling points was specified based on the results of magnetic exploration, which was used with a ferrosonde magnetometer.

Processing of the studying results the granulometric composition of the selected samples based on the results of weighing
The results of weighing the fractions of finely dispersed particles with a size from 0 to 400 microns, separated by scattering on laboratory sieves, were used to calculate the Ni particles in the skin and the fraction determined by the formulas.
where Mithe mass of the fraction, gram; density of rock in a solid body, gram/cm 3 ; Vifraction volume, cm 3 ; Nithe number of particles in the fraction, pieces.
The obtained data were further used to determine the granulometric characteristics of the analyzed samples, in particular, dav (average size of particles in the analyzed sample) and tg (degree of particle sorting), which was set according to the cumulative curve.The value of tg also shows the degree of particle sorting.The larger the value of tg, the more particles of the same size are contained in the sample.

Determination of fine particles mineralogical composition
The belonging of the investigated particle to one or another class of rock-forming minerals was determined visually using a polarizing microscope based on their characteristic optical and morphological features: relief, color in direct and polarized light, the shape of the fragments, etc.The percentage content of minerals in the analyzed sample was determined by the linear method, using special counting drums on the integrator (total of 6 pcs.: 3 main and 3 auxiliary) and the screw of the idle speed of the integrator.
The percentage content of the mineral Mt (magnetite) in the studied fraction of a potential technogenic deposit consisting of several mineral components is determined by the formula CMt = Mt/(Mt, Q, Bt, Pr...) (2) where CMt is the magnetite content, in unit fractions; Mtmagnetite, Qquartz, Btbiotite, Prpyrite; (Mt, Q, Bt, Pr...)sum of all values.The data shown in table 1 indicate the following.The average particle size of iron quartzite beneficiation waste is almost independent of the distance to the lower end of the slurry pipeline -the source of production waste supply to the potential man-made deposit area.The values of the particle sorting coefficient tg have a significant value and also have little dependence on the distance to the slurry pipeline.Although at a distance of 200 meters, its value is maximum, that is, the particles are well sorted (the greater tg, the more particles of the same size are contained in the sample, as already mentioned above).But this, in our opinion, is more of a case than a trend.
The most interesting results of the research on the fractional and mineralogical composition of the tailings deposit of the Poltava Mining and Processing Plant were obtained during the study of the magnetic minerals content in the fractions that were isolated during the scattering of dried samples on laboratory sieves with cells from 0 to 400 microns.The results of the research are shown in figure 1.

Size of particles, microns
In each pair, the left column (red) is Fe magnetic + quartz.
Right column (green) is non-magnetic Fe + quartz Similar results on the ratio of magnetic and non-magnetic material in samples of sludge from iron quartzite beneficiation waste were obtained for all 30 samples taken at different distances from the lower end of the sludge pipeline.
For all sludge samples over the entire area of the studied areas, a trend towards an increase in the content of magnetic material (magnetite) in small fractions, i.e. 100-160, 50-100 and 0-50 microns (linear dependence) can be clearly observed.
These results the fractional and mineralogical composition determining of finely dispersed particles, i.e. sludge, to a certain extent give an idea of the nature of the mineral components spatial distribution in wastes from the ferruginous quartzites enrichment within the investigated section of the tailings repository (directly near the lower end of the sludge pipeline, at the most distant point of sampling and in the middle part of the studied area).

Prediction of the magnetic minerals spatial distribution on the area of the discovered man-made deposit.
The study of the fractional and mineralogical composition of iron quartzite beneficiation waste on the tailings storage area of the Poltava mining and beneficiation plant made it possible to establish the following.The percentage content of total iron (Femagnetic+Fenonmagnetic) has significant fluctuations.If the total iron content is 13.7 % at the sampling points near the lower end of the slurry pipeline, then at a distance of 100 m it decreases to almost 11.5 %, and at a distance of 200 m from the slurry pipeline, the total iron content reaches 14.8 %.
Thus, there is no certain regularity of the change in the total iron content with increasing distance from the slurry pipeline -the source of supply of iron quartzite enrichment waste to the place of its accumulation.That is, there is no definite relationship between the percentage content of iron in enrichment waste and the location of sludge sampling points on the area of the experimental site and the source of this waste wearthe sludge pipeline.
It is possible to state the fact that the spatial distribution of iron in the wastes of ferruginous quartzite enrichment has a random nature.Evaluating the overall structure of the deposits from the waste of ferruginous quartzite enrichment in the tailings repository, that is, the potential deposit of man-made raw materials, it is worth noting the following.On the one hand, the spatial distribution of valuable components, namely iron, in the tailings repository is chaotic, i.e., random, and on the other hand, there is a steady pattern of increasing the percentage of the magnetic component -magnetite in the finedispersed fraction with a mineral particle size of 1 μm and even less up to 100-160 microns.
Such a characteristic feature of the spatial distribution of small particles of iron-containing minerals is caused, in our opinion, by the turbulent mode of transportation of iron quartzite enrichment waste to the place of its accumulation.In the sludge pipeline, it is so for technical reasons [7], namely to prevent silting of the pipe with heavy minerals, if there is a laminar mode of sludge transportation from the enrichment factory to the tailings.
And already at the stage of moving waste across the tailings storage area, the turbulent regime is maintained at a certain distance from the lower end of the sludge pipeline.In this mode, small particles in the liquid transport agent (water) behave like dust that floats in the air and does not settle on the soil for a long time.That is, the turbulence of the sludge flow during the transportation of iron ore beneficiation solid waste in this environment has a more significant effect on the process of solid particles settling (the rate of their deposition and the distance of transport) than gravitational forces.As for the phenomenon of finely dispersed sludge fractions (0-160 microns) enrichment with magnetic material, namely, magnetite, in this case, in our opinion, the domain character of this mineral is indicated here.Without going into details, we note only the fact that its magnetization increases with decreasing particle size.It is possible that the process of their over-enrichment is affected by an additional magnetic field generated by small magnetite particles during the transportation of sludge to the place of its deposition within the tailings storage facility.
Since the valuable components -iron-containing minerals and quartz (potential construction raw materials) -are randomly distributed over the tailings area, therefore, when drawing up predictive plans (maps, schemes) of the spatial distribution of iron-containing minerals in enrichment waste, it is necessary to use mathematically based methods from the point of view of the theory of probabilities.
Schemes and forecast plans of the spatial distribution of the studied characteristics of the deposit (average grain size, content of mineral components, grain sorting coefficient, etc.) are known to most clearly characterize the structure of a mixed type a potential man-made deposit.They are the basis for the development of rational technologies and operating parameters of man-made deposits over time.
When constructing predictive plans for the distribution of mineral components in space, it should be borne in mind that the method of isolines (for example, the percentage of magnetite) has a significant drawback, namely, uncertainty when interpolating the value of the content of the mineral component under study in the center of the square (minimum/maximum) formed by four adjacent sampling points.Therefore, in order to avoid this uncertainty, when building predictive plans for the distribution of valuable components (iron) within the studied areas of the Poltava Mining and Processing Plant, we used probabilistic methods that exclude the introduction of elements of subjectivity of the executor into this process.In particular, the equation [18] was used to determine the characteristic zones of accumulation of iron-containing minerals in which N is the maximum amount of the useful mineral component of the sample (100 %, while one unit equals 1 %); miparameter of the number of observations; t is the value of the normalized deviation, which was assumed equal to 1.96 ~ 2 and 3.As a result of solving equation ( 3), the following categories of spatial distribution of the studied mineral component were identified.I. Scattering zone, i.e. fields to which the studied mineral component practically does not enter; in these areas ni <nmin, t=3.
II.The zone of transition from scattering areas to isotropic zones, in which the distribution of the mineral component does not differ from uniform and the given object under investigation appears very rarely.For this zone ni > nmin, t=3 , ni < nmax, t=2.
III. Isotropic zone.In it, the distribution of the mineral component on the selected area does not differ from a uniform one by the amount of no more than a random error, i.e. ni > nmin, t=2, ni < nmax, t=2.
IV. Zone of beginning concentration of the mineral component.In this zone, an increase in the concentration of a mineral component usually indicates the mandatory presence of the cause of its concentration ni > nmax, t=2 , ni < nmax, t=3.
V. Zone of concentration of the studied mineral component.It is characterized by the fact that ni, which corresponds to it, reaches the corresponding values almost exclusively in the presence of the reason for their concentration ni > nmax, t=3 In figure 2 shows a forecast plan for the distribution of iron in the samples taken at the investigated site 316 of the tailings depository of the Poltava Mining and Processing Plant).

Conclusions
A previously unknown regularity of changes in the mineral composition of beneficiation wastes from mining ore production was established experimentally.This is caused by the turbulent mode of transport and deposition of iron quartzite beneficiation waste in the tailings, which may be a potential man-made mixed type deposit.This regularity consists in the fact that with a decrease in the particle size of mineral components (finely dispersed fractions of iron-containing minerals and quartz with a size of 0-200 microns), the share of the magnetic mineral magnetite increases linearly and, accordingly, the share of the non-magnetic mineral quartz decreases.
Predictive plans for the iron distribution based on maps of leachate in the tailings storage facility of the Poltava Mining and Processing Plant have been built.

Figure 1 .
Figure 1.The ratio of magnetic and non-magnetic material in different fraction of slime (district 14, point 14, map 316, 2 profile, Poltava mining plant, tailings dump).

Figure 2 .
Figure 2. Probable distribution of magnetic iron on site 316 of the Poltava mining tailings repository: II -Transition to the dispersion zone; III -Isotropic zone; IV -Transition to concentration zone; V -Zone of concentration.P.1…P.15numbers of sampling points with iron content

Table 1 .
The results of the of the fractional and mineralogical composition study of the Poltava Mining and Processing Plant tailings repositoryAs research has established, the fractional and mineralogical composition of the samples taken at this potential man-made deposit is almost identical, that is, the determined values of individual parameters do not differ much from each other.Below are the most characteristic results of the study of some samples (table1).Fractional and mineralogical composition of sludge samples from the tailings pond of the Poltava Mining and Processing Plant at different distances from the lower end of the sludge pipeline.