Research of geospatial variability of quality indicators of Zlobychi alluvial ilmenite deposit

The paper assesses the geospatial variability of quality indicators of the Zlobychi alluvial ilmenite deposit of the Irsha group of deposits. The variability of quality indicators was also studied. Based on the use of statistical methods, the dependencies between individual quality indicators were established. A close correlation between the ilmenite content and the thickness of the formation, the thickness of the sole and the thickness of the peat, and an average correlation between the thickness of the formation and the thickness of the sole were found. The main result of the research is the construction of complex placer models, which are used to clarify the structure and conditions of the deposit formation, and to identify conditioned and unproductive areas. The correlation between the distribution of ilmenite and the value of the thickness of the ventilation crust was established. The data for determining the optimal development directions are presented and the zones of mineralization are identified.


Introduction.
Titanium is one of the strategic metals for Ukraine.It is widely used in the aerospace, shipbuilding, automotive, chemical, and other industries.According to the U.S. Geological Survey, Ukraine has about 1% of the world's ilmenite reserves and accounts for 5% of the world's production.The State Balance of Mineral Reserves of Ukraine includes 26 deposits of titanium ore, of which 14 are being developed.2 deposits are unique in terms of reserves, and 12 are large.According to expert estimates, confirmed reserves of titanium raw materials in Ukraine, given current production and consumption volumes, will meet the needs of consumers for almost 200 years, and explored reserves -for 430 years.In other words, in terms of its reserves, Ukraine is among the countries with the largest deposits of ilmenite, and our country is second only to Norway in terms of ilmenite reserves.Ilmenite deposits of the Irshansk group of deposits, which is part of the Volyn placer district, are the largest in Ukraine and are characterized by significant variability in quality and localization in a relatively small area.Prospects for the development of a large titanium industry based on Volyn's ilmenite raw materials are quite favorable and economically extremely profitable.These facts determine the relevance of the research.

Methods.
The Zlobytske alluvial ilmenite deposit was the object of study.To establish the patterns of distribution of ilmenite at the Zlobytske placer deposit, we modeled the Poltava series sediments.The modeling was carried out in the Serfer 15 program, the interpolation method was kriging.Statistical processing was performed in Microsoft Office Excel.

Results and discussion
Zlobychi alluvial ilmenite deposit is located in the northwestern part of the Ukrainian Shield, within the Irshansky placer field of the Volyn placer area (figure 1).
Formationally, the deposit includes two strata: sedimentary, mainly psammite composition ("Poltava series" of Neogene, i.e. in one or another volume Novopetrivska Formation, as well as overlying Quaternary and underlying Buchak formation of Paleogene, Apt-Albian deposits of Lower Cretaceous), and weathering mantle of crystalline rocks basement (kaolin profile).The mineralization of the sedimentary sequence has a through character, but its predominant part is localized in the Poltava series.Smaller concentrations of ilmenite are noted in the Quaternary sediments overlapping the placer.In the sediments of the Buchak Formation (1% of the volume of the strata), the concentrations of ilmenite are also elevated and reach 170 kg/m 3 .The average content of ilmenite in the contour of the balance reserves of the alluvial part of the placer is 56.2 kg/m 3 ; in the weathering crust -66.6 kg/m 3 [1,2].Previous studies have created digital structural and lithologic models (DLSM).For the procedure of development of DLSM [11] as a means of structuring in the sandy strata were allocated according to the traditional lithological features 19 lithofacies: quartz fine-grained, clayey sands; dark gray quartz multigrained sands; quartz fine-grained, clayey sands with flint fragments; sandy siltstones; carbonaceous clays; quartz sands multigrained with gravel and pebbles, clay; quartz sands multigrained carbonate, clay; quartz fine-grained kaolinite sands with pebbles; quartz fine-grained carbonate sands sandy loams; fine-grained quartz sands with a small admixture (up to 10%) of weathered feldspars, kaolinite; dark gray sandy loams; kaolinite gravel deposits; sandy limestone; secondary kaolin; sandy limestone with flint fragments; quartz sandstones on kaolinite cement; fine-grained sands, kaolinite; fine sands.Data on the distribution of lithological rock types are important for the development of rational mining schemes, including the selection of optimal mining equipment [4,5].
Genetic interpretation of the isolated lithofacial types made it possible to establish 10 microfacies: outer flood plain; inner flood plain; flood plain (lake-bog microfacies); flood plain with temporary flows; flood plain with lake microfacies; flood plain close to the sources of weathering corrosion drift; riverbed near the source of drift; riverbed with deluvium; lakebed.The distribution of ilmenite within separate lithofacial types is subject to the regularities of hydrodynamic flow in the paleovalley and has a complex character.In order to develop the optimal mining scheme of the deposit, it is necessary to study the regularities of the profiles, the relationship between the parameters of the sedimentary basin and the content of ilmenite in it.
The placer-formations are gabbro-anorthosites of the Korosten pluton, in particular, the Graby-Meleni gabbroid bodies, with which the main mass of ilmenite may be associated, as well as granite massifs located west of the deposit, and vein formations of the Zlobychi fault for zircon [1,4].The mantle of weathering is an intermediate reservoir for the formation of alluvial placers.
The weathering mantle of crystalline rocks of kaolin profile is developed on the parent rocks of the crystalline basement almost everywhere, overlapping 90% of the area.It is absent in floodplains of streams of deep erosional incision, where sometimes bedrock is exposed.The mantle of weathering is distributed area-wide, but there are fragments of linear mantle of weathering confined to tectonic faults of the same northwestern strike (profile 52, well 015).Linear weathering mantles are characterized by higher thickness (up to 22.5 m) and better preservation of the lower parts of the section (weathered and fissured rocks).The average thickness of the weathering crust is 4.7 m, with variations from the first tens of centimeters to 5-15 m.The weathering mantle have the following profile (from bottom to top): 1) a zone of partial kaolinization (kaolinized gruss) 2) full kaolinization (primary kaolin), i.e. prevails incomplete profile of the weathering crust, typical for many objects of the Volyn placer area.
Changes in the lithological features and parameters of the mantle of weathering layer occur discontinuously, depending on the manifestations of tectonic movements, as well as depending on the paleorelief.In general, the structural and tectonic factor creates a certain mosaicism of the paleorelief and mosaicism of the mantle of weathering.The dependence of ilmenite on the thickness of the mantle of weathering is also mosaic in nature.
The development of the structural and lithological model ensured the solution of the following tasks: displaying the rock composition, facies composition, structural indicators -roof and basement relief, sediment thickness; establishing the spatial distribution of mineralization in the volume of the geological body; establishing correlations between mineralization and the above structural and lithological characteristics of the object.For the weathering crust, structural and lithological reflections show that mineralization is confined to depression areas of the crustal footwall and faults in the crystalline basement, and in the sectionmainly to the zone of complete kaolinization (figure 3).Blue tones show the areas of erosion (correlation coefficient is negative).Gradations of ilmenite content (kg/m 3 ) were established: 0-10, 10-25, 25-50, 50-75, 75-100 і > 100.According to these gradations, a map of the distribution of ilmenite content was constructed (figure 4).The map contrasts the areas of high content, which are confined to the central part of the deposit.Some of the lithological parameters can be used to determine technological properties.It is important to note that these maps (in two modifications: for the Poltava series and the weathering crust) are the basis for developing a selective mining scheme [3,[6][7][8][9][10][11][12][13][14][15].
It should be noted that for the available results for the entire deposit, no unambiguous correlation was found (figure 5).After conducting a study on individual blocks, it was found that there is a close correlation for a part of the reservoir (figure 7).
Figure 6 shows a summary plan of the reservoir thickness based on the data of exploration lines in the Zlobytske field.According to the data of the isolines, we can state the change in the thickness of the mineral from west to east, the variability of the thickness is characterized by a lower frequency of power drops with a sample size of up to 20 m.
The generalization of the patterns of change in the thickness of the productive ilmenite seam suggests that the variability of this indicator is characterized by significant unevenness, which does not allow establishing a relationship between the variability of thickness indicators for the entire deposit.For further geometrization of spatial variability, a table of correlation between individual quality indicators was created (table 1).The following indicators were selected for analysis: reservoir thickness, ilmenite content, floodplain alluvium with poor mineralization (alluvium depleted in minerals) and bedding thickness (here is the thickness of the rocks of gabbroids massif enriched by ilmenite and involved to the weathering).As a result, a close correlation between the ilmenite content and the formation thickness, the bedding thickness and the thickness of floodplain alluvium with poor mineralization, and an average correlation between the formation thickness and the bedding thickness was established.This made it possible to establish the dependence of the ilmenite content on the formation thickness (figure 8) in the form of a second-order polynomial: y = 0,69x 2 − 3,92x + 55,48 R² = 0,68 The dependence of the bedding thickness on the floodplain alluvium with poor mineralization thickness was established (figure 9):

Figure 4 .
Figure 4. Visualization of the digital model of the Zlobychi ilmenite placer.Distribution of contents and calculation of ilmenite reserves in the weathering crust.Scale 1:25000

5Figure 6 .
Figure 6.Variability of reservoir thickness according to the data of exploration lines in the Zlobytske deposit, m

Figure 8 .
Figure 8. Dependence of ilmenite content on reservoir thickness

Figure 9 .
Figure 9. Dependence of bedding thickness on floodplain alluvium with poor mineralization thickness

Table 1 .
Table of correlation between individual quality indicators Problems of the study of ilmenite deposits of the northwestern part of the Ukrainian shield Collection of scientific works of the National Mining University 23 22-7 6. Kuzmanenko H O, Okholina T V, Ganzha O A and Yaremenko O V 2023 Rore bearing of the Poromivske ilmenite deposit Mineral resources of Ukraine 3 3-7 7. Remezova O, Vasylenko S, Okholina T and Yaremenko O 2019 Elaboration of geological and technological models for rational development of titanium deposits Modernization and engineering development of resource-saving technologies in mineral mining and processing Multi-authored monograph UNIVERSITAS Publishing 431-44 8. Komliev O, Bortnyk S, Remezova O, Spytsia R, Vasylenko S and Zhylkin S The use of data on the material composition of sediments during forecasting works of titanium root and placer deposits European Association of Geoscientists & Engineers Conference Proceedings, Geoinformatics 1-6.DOI: https://doi.org/10.3997/2214-4609.202155211639. Remezova O O, Khrushchov D P, Vasylenko S P and Yaremenko O V 2021 Innovative approaches to information modeling of placer deposits European Association of Geoscientists & Engineers Geoinformatics 1-6 DOI: https://doi.org/10.3997/2214-4609.2021552110010.Vasylenko S P, Оkholina T V, Remezova O O and Yaremenko О V 2016.The analysis of ilmenite distributing in titaniumdeposits by GIS-modeling (on the example of Torchyn apatite-ilmenite deposit) Teoretychni ta prykladni aspekty gheoinformatyky 13 4-13 11.Khrushchov D P, Kovalchuk M S, Remezova E A, Lalomov A V, Cymbal S N, Bosevskaja L P, Lobasov A P, Ganzha E A, Dudchenko Yu V and Kroshko Yu V 2017 Structural and lithological modeling of sedimentary formations Institute of Geological Sciences of the National Academy of Sciences of Ukraine Interservis p. 352