On the coherence of the formation of containing and ore containing Precambrian formations Orikhovo-Pavlograd suture zone of the Ukrainian shield

This paper presents the results of detailed geological and structural surveys within the Orikhovo-Pavlograd suture zone of the Ukrainian shield. In the northern part of the Orikhovo-Pavlograd suture zone of the Ukrainian shield, dislocation structures of several generations are identified, which differ from each other in spatial placement and R-T values of material filling. The structures of the first five generations are formed by mineral parageneses from granulite to green shale facies of metamorphism; their age is connected to the time range of 3.6–1.8 billion years. Later dislocation structures are postmetamorphic. At the micro-meso levels of the organization, the selected structures are represented by striation, shale, linearity, cleft, cracks, etc.; at the macro level, they are represented by viscous and brittle faults. Systematized data on the structural and material organization of U-, Th-containing Pivnichno Tersyansk folded shape according to the principle of hierarchy of geological structures. It is shown that this U-, Th-perspective object is a highly ordered propulsion structure. That is, its formation was provoked by Paleoproterozoic displacements and occurred synchronously with the formation of containing geological bodies by turning up existing Precambrian formations with the creation of new structural and material parageneses. An idealized model of forming a single U-, Th-perspective structure is created, this will contribute to the search for uranium-thorium mineralization and the expansion of the mineral resource base of nuclear energy in Ukraine.


Introduction
The Orikhovo-Pavlograd suture zone crosses the Ukrainian shield (US) in a submeridional direction and traces beyond its borders.It has a deep structure in the form of a package of tectonic plates of subvertic fall.Within the US, this suture zone can be traced at a distance of up to 200 km with a width of 40 to 4 km and separates the Serednioprydniprovsky and Pryazovsky Megablocks of the US.The Orikhovo-Pavlograd suture zone differs from adjacent 1254 (2023) 012113 IOP Publishing doi:10.1088/1755-1315/1254/1/012113 2 Megablocks in the nature of the manifestation of the Moho interface surface -within the zone it is fixed in the depth range of 42-46 -53 km, in Megablocks -at the level of ∼ 40 km [1].But the zone is most clearly distinguished relative to Megablocks as a deep linear zone of increased electrical conductivity [1].
According to [2], the depth of the sole of the "Granite" layer of the Earth's crust within the studied part of the gorge is ∼ 10-15 km.
The depth of the sole of the transition layer for the Orikhovo-Pavlograd zone is 25-30 km; the depth of the erosion section is determined at 17-20 km [2].
The Orikhovo-Pavlograd zone is identified [1] with the zone of collision of the Pryazovsky and Prydniprovsky microcontinents at the archaea Proterozoic boundary and is interpreted, together with the adjacent edge parts of Megablocks, as regions of permanent stretching-compression of the crust.In other words, these are areas of more intensive processing of the epiarchean foundation, compared to the central parts of Megablocks.
The western border of the zone is considered to be the Orikhovo-Pavlograd deep fault, which runs far beyond the US (to the Kursk magnetic anomaly area), because it is clearly expressed in physical fields.According to deep seismic sounding data, a ledge of the Moho section with an amplitude of 8 km is recorded in the fault zone (at Chapter 44-46 km).Gabbro-peridotites of the Novopavlivsky section and the Malotersnyansky alkaline massif are associated with this fault.The Orikhovo-Pavlograd fault has an inclined-stepped displacement surface, which is formed from structures of higher orders with an easterly fall.The angles of incidence vary from 70-80°i n the near-surface part of the foundation to 40°in the upper mantle.The eastern boundary of the zone is considered to be the West-Azov (Azov-Pavlograd) fault, it is also well expressed in physical fields and is fixed by the gravitational step.The fall of the fault offset in the upper parts of the crust (0-3 km) is subvertic, and with depth it becomes more inclined with a fall to the West [1].
According to Kruglov et al [4], The Orikhovo-Pavlograd zone, like other suture zones of the gorge, differ sharply in formation content, but usually only in dislocation intensity and other features from one of the adjacent Megablocks, while at the same time they have many common features with the other.That is, according to the authors [4], suture zones are not peer-topeer with Megablocks and independent structural-formation zones.In particular, the Orikhovo-Pavlograd zone (synclinor zone) occupies the westernmost part of the Priazovsky megablock and borders the West Priazovsky anticlinor zone along the Korsatsky and Pavlograd deep faults.
Within the Orikhovo-Pavlograd suture zone, known uranium (thorium-uranium) mineralization is represented by a small number of ore occurrences of uranium (thorium-uranium) hydrothermal in mineralized zones of crushing of crystalline rocks of the ore formation.It mainly tends to its western parts within the Orikhovo-Pavlograd deep fault, these are the Pivnichno Tersyansk, Vasynivsky, Novopavlivsky ore occurrences, etc. [8].

Results and discussion
The authors of the article carried out detailed geological and structural works in the northern part of the Orekhovo-Pavlograd seam zone (River Vovcha Basin , next to the village Vasylkivka), where feldspar quartzites, Garnet-biotite gneisses, tonalites-tonalito-gneisses, and granitoids were studied in quarries.It is established that deformation formations of 7 generations are manifested in all the studied rock varieties.These are banding, slitting structures, shale formation, several generations of mineral linearity, and brittle cracks.The actual material on the placement of metamorphogenic structures was processed using the StereoNett 2.46 program; the Pivnichno Tersyan folded shape was also characterized in accordance with the principle of hierarchy of geological structures.
Generation structures-1 expressed as relict lenticular subtiles among later dissection planes.Such bodies of various sizes -from several see up to the first meters; the ratio of their long axis to the short one (a: C) reaches 7. Axis a obliquely submerged in azimuth 330-0 (1 in figure 1).
For quartzites, these are close to massive bodies of essentially quartzite composition, which are distinguished by shades of colors ranging from dark gray to light gray, almost white (L 1 in

Feldspar quartzites
Garnet gneisses-biotiaceae Tonalites-tonalito-gneisses Amphibolites For geological bodies of Garnet-biotite gneisses, relict formations are poorly diagnosed by shadow linearity in the separation planes, which is expressed as the division of rock into dark and light gray fractions (L 1 in figure 3).In tonalites-tonalites-gneisses, the structures of this generation are represented by elongated massive bodies of the tonalite composition (figure 4 marked -t), enderbites, and amphibolites.
Generation structures-2 they are most clearly expressed in tonalito-gneisses and are represented by striation, which is due to variations in the mineral composition.Banding has a dip azimuth of planes of ∼ 70, < 80-90.The thickness of the strips does not exceed 1 cm (2 in figure 1 A and Y 2 in figure 4).
In Feldspar quartzites, the structures of this generation include one of the shale formations formed by rock-forming minerals and their lenticular aggregates (figure 2); it has elements of occurrence similar to banding in tonalito-gneiss.The structures of this generation also include linearity, which sinks at angles of ∼ 45°in both quartzites and biotite gneisses (L 2 ? in figure 2, figure 3).
Generation structures-3 it is represented by striation and shale with steeply falling mineral linearity.The banding of this generation is most clearly distinguished in geological bodies of the composition of tonalites-tonalites-gneisses and Garnet-biotite gneisses.In tonalito-gneiss, these are Lenses strips with capacities of several cm (3 in figure 1, Y 3 in figure 4) granite composition, which are secant to the structural elements of previous generations in several degrees.In garnet-biotite gneisses, these are leuco-and melanostripes.The first of them are quartz-feldspar composition, the second correspond to gneiss proper (figure 3).The shale content of this generation is well expressed in Feldspar quartzites; it is formed by rock-forming minerals and their aggregates (figure 2).
Mineral linearity of Generation-3 in tonalito-gneisses is weakly expressed; it is most clearly distinguished in geological bodies of the composition of Feldspar quartzites by elongated aggregates formed by feldspar, biotite and garnet; in bodies of the composition of Garnetbiotite gneisses, linearity is relatively moderately expressed by elongated aggregates of biotite and Garnet (3 in figure 1; L 3 in figure 2, figure 3).The size of such units is from several to 8 mm, a: c -5-7, their placement reproduces subvertic chains several tens of centimeters long.
Generation structures-4 for all the studied breed varieties, they are represented by separation.They are expressed by a shale matrix (actually dissociation zones), which contains lenticular bodies subordinate to it with a relatively massive structure.The separation planes are formed by single-system placement of flat grains and aggregates of rock-forming minerals.Dip azimuth of planes shale/slotting planes ∼ 70 at angles of about 40.For quartzites, the dissection structures are expressed as alternating shale feldspar quartzites and close to massive quartzites (figure 2).For Garnet-biotite gneisses, the dissection structures are represented by separate gneiss dissection zones that distinguish the striped gneisses themselves.The capacities of such zones are the first see, the distance between them reaches several tens of centimetersthe first meters.For tonalites-tonalites-gneisses, the shale Matrix corresponds to gneisses of the tonalite composition (tonalite-gneisses).Packages of shale tonalito-gneiss reach capacities from several meters to several tens of meters (figure 4).Such packages contain lenticular bodies of the composition of tonalites and enderbites and striped tonalites, as well as folded-lenticular bodies of the composition of amphibolites with dimensions of tens see -first meters.
In the shale planes, there is a mineral linearity that sinks obliquely to the Southeast (4 in figure 1).In Feldspar quartzites, this linearity is formed by Muscovite aggregates; in garnetbiotite gneisses-Muscovite and biotite (L 4 in figure 2, figure 3); in tonalites -tonalites-gneisses, linearity is represented by hinges of folded bodies of amphibolites and elongated spindle-shaped aggregates of quartzite composition.The dimensions of the latter along the long axis reach 20 cm, a: C exceeds 10 (figure 5).Generation structures-5 they are represented by single planes of separation (5 in figure 1; Y 5 in figure 4), which fall relatively steeply to the West.They are also formed by rock-forming minerals.The distances between such planes are measured in tens of centimeters.They carry a mineral linearity that sinks obliquely to the northwest (L 5 in figure 2,3).In quartzites, it is expressed by sericite scales.
Generation structures-6,7 to varying degrees, they are manifested in all the studied  to 45 in the southern points (figure 6).Geological bodies of granites and amphibolites also have a hybrid structure similar to that of tonalito-gneisses and garnet-biotite gneisses (figure 1, figure 7).The amphibolites are found as very dispersed lenticular-house bodies of various sizes among the shale matrix of the tonalito-gneiss composition (figure 4).We have not recorded geological bodies of granite composition in the form of single manes and their immediate boundaries with formations of a different composition.But these "manes" of granite composition in the transverse (up to the leading shale) cross-section have an inhomogeneous, striped-folded internal structure (figure 7).The latter is expressed by lenticular subtiles with internal drawing folds and resistances that reproduce the right-wing structural pattern.The base of this pattern is formed by white granites, the contours of lenses, folds and feather are formed by red ones.At the same time, the ribbonlike bodies of red granites are not injections, the boundaries between them and white granites are gradual, and the shale of white granites is subordinated to the structural pattern formed by the striation of red granites.
The latter is often divided into quartz and feldspar fractions, and the cores of folded forms contain sickle-shaped clusters of dark-colored minerals.All this indicates that the formation of both types of granites occurred simultaneously due to synshifts structural and material transformations.
From time to time, fairly dispersed shale planes can be traced within the granitoids, falling to the northeast and west -southwest.That is, shale is similar to that of generations 4 and 5 in other types of rock bodies.Therefore, it can be assumed that folding with material transformations in granitoids occurred at the third stage of structural-material transformations of the studied part of the suture zone.
Thus, in all rock varieties of geological bodies within the part of the studied zone, the same structural and material paragenesis was manifested.They are the same in terms of spatial position, the number of generations of structural elements, and R-T implementation conditions.Consequently, all the studied rock varieties of the Orikhovo-Pavlograd zone were formed similarly and gradually, structural and material transformations in their volumes occurred cooperatively/simultaneously, in several stages under significantly shifted tectonic conditions against the background of regressive changes in the R-T parameters of the medium.Moreover, such transformations took place together in the entire volume of the suture zone fragment under study -from the micro -to macro-level of its petro-structural organization.The latter is evidenced by the self-similarity of structural forms at all levels of subordination for all geological bodies studied.That is, the studied volume of crystalline rocks is the only dislocation system that was formed during at least five stages of structural and material transformations of the crystal base.
The formation of the studied dislocation structures occurs in a shift environment [9][10][11], that is, their shape and placement are subordinated to the directions of action of tectonic stresses.At the micro level, these structures are formed using diffusion, filtration and other mechanisms of substance movement.Accordingly, their material filling reflects the conditions of formation of the studied structures.According to [5][6][7], the degree of metamorphism of the substance of dislocation formations reached granulite and amphibolite facies.Therefore, with age ranges 3.6; 3.4-3.3;2.8-2.7,2.0 billion years [5][6][7] and 1.9 [8] billion years we associate the formation of the metamorphogenic dislocation structures described above.According to Goryainov et al [12], we link the structures of generation-3 to the timestamp ∼ 2.8 billion years ago, generation-4 ∼ 2.0, generation-5 ∼ 1.9-8 billion years ago.
Pivnichno Tersyansk folded form of the Orikhovo-Pavlograd suture zone as its around shift component Under tectonically active conditions, which are recorded in variations in the spatial position and P-T values of the creation of the studied structures, the ore substance could not be unused to the above-described transformations of the Precambrian Foundation.And ore bodies within the suture zone could be created only under tectonic conditions, under which both the containing rocks and the entire part of the foundation under study were formed.This is evidenced, for example, by the data systematized for Pivnichno Tersyansk folded shape, based on the materials of works [1,8].They are listed below in paragraphs 1-5, starting from the macro level of the petro-structural organization of the object (point 1), ending with the micro level (point 5).For such systematization, the Pivnichno Tersyansk folded form was chosen because it was relatively well studied by previous researchers due to the fact that this structure contains a deposit of ferruginous quartzites, ore occurrences of uranium and thorium, and manifestations of other mines [1,8].In addition to the above, the Pivnichno Tersyansk folded form is composed of rock associations similar to those that we studied within the Vasylkivska site.
1.The Pivnichno Tersyansk folded form at the macro level is expressed by two componentslinear (plate -shaped) and sub-ring-shaped.The elements of the first of them are subordinated to the following elements of the Orikhovo-Pavlograd suture zone as a whole (figure 8).Namely, the linear component has an dip azimuth to the southeast at an angle (<) of 80-85°with an extension of up to 2 km and a power of ∼ 0.5 km [1,13].It is traced to a depth of ∼ 0.5 km.The sub-ring component (brachisincline according to [13]) reaches a diameter of 1.0 km.Its axis has a near -latitude direction, the fall of the wings in the southern part of the brachisincline is close to vertical, in the northern part-a fall to the south at < 50-60° [13].
Figure 8. Schematized diagram of the placement of planar and linear structural elements for the Pivnichno Tersyansk folded shape, according to data from [1,13] in the projection on the lower hemisphere.a -the pole of a linear (plate -like) macro-component; b-metamorphogenic linearity (tensile axes), respectively, of the above (in figure 1) data; c -projections of rotation axes.Digits -numbers of structure generations.
If we start from the fact that the linear and sub-ring components of the Pivnichno Tersyansk folded form were formed interrelated, in several stages (as well as the contained geological bodies of figure 1-figure 7), then the linear component is the zone of secondary striation and separation of stages 3-4; its pole is the point of application of tectonic compression forces.The placement of the rotation axes of generations-4 and 5, however, is close to vertical (even if the tension axes are placed sub-wide, according to the placement of the axis of the sub-ring component).That is, it follows from these data that the sub-ring component of the Pivnichno Tersyansk folded shape was formed due to the propulsion rotation of metamorphogenic strata.Accordingly, in this component, relative to the linear one, petrostructure formation occurred at lower R-T indicators of the medium.The elongated tail of the sub-ring component indicates a left-hand rotation, which we associate with the fifth stage of structural and material transformations of the studied part of the foundation; this is about 1.9-8 billion years ago.In the tail section, as a marker of relative compaction, there is a granite massif.The model of formation of such structures is recorded in natural models of structure formation (figure 7). 2. At the meso-level, both components, linear and sub-ring, of the Pivnichno Tersyansk folded shape are formed by consistent stratal-lenticular geological bodies with elements of occurrence that are similar to those for macro-composite ones.Mesotil capacities range from a few meters to 70 m with a horizontal length of tens of meters to several kilometers.That is their a: c (the ratio of the long axis to the short axis) reaches 10.Material, within the linear macro-component, geological bodies of the meso-level are represented by amphibolites, modified to varying degrees by ultramafic rocks, chloritized amphibol-magnetite quartzites and quartz-magnetite shales.Within the sub -ring component-biotite, biotite-garnet, biotite-silymanite gneisses, feldspar and glandular quartzites.
According to the studies [10,14], as well as ours, which are given above, the formation of the above-described structure of the Tersyansk folded shape is possible due to the involvement of the primary crystal base in repeated deformations of shear-stretching and scrolling of its individual fragments.That is, it is a secondary stratification -tectonostratification of the geological environment a: c it is an expression of the degrees of elongation of geological bodies under such deformations; the degree of metamorphism is an indicator of the P -T conditions of the dislocation process.In this case, in the linear macro-component of the Tersyansk folded form relative to the sub-ring form, the degree of metamorphism is higher, which is one of the confirmations of increased strain pressures within the linear component at the time of formation of the Tersyansk form as a whole.3. Geological bodies of the meso-level, both in linear and sub-ring components Tersyansk folded shape, striped and slate [1,13].The striping is caused by changes in the mineral composition and dimensions of mineral grains; the capacities of pronounced banding in this way range from a few millimeters to several centimeters.Shale formation is caused by the single-system placement of flat minerals and their aggregates.
As shown above, we have identified several generations of striation, shale, and mineral linearity.All of them are more or less manifested in all varieties of breeds.But the most intense is the shale formation and linearity of generation-4, which actually creates a mutual agreement of all geological bodies.Striation and shale formation and their coherence are expressions of the shear/stretch process at the micro level.At this level it is realized due to syndeformational recrystallization in the direction of relatively reduced strain pressures [15,16].4. Accordingly, [8] uranium-thorium mineralization within the Orichovo-Pavlograd suture zone is localized in layers of schistose and mylonitized chlorite-mica quartzites among micaceous quartzites of the Vovchansk Formation.According to our data, such "layers" in quartzites are the result of at least the fourth stage of structural and material transformations of the studied zone fragment.5.In the mineral composition of the studied geological bodies, there are mineral parageneses from the granulite to green-shale degree of metamorphism [1,7,13].Within the Vasylkivska site, depending on the degree of separation, the chemical composition of minerals changes [7].
So, from all the above data, it follows that all the structural, material and age attributes of the northern part of the Orikhovo-Pavlograd suture zone are highly consistent.This is a consequence of tectonic-metamorphogenic transformations of this fragment of the crystalline basement in several stages.The transformations of the Fourth of the selected stages, which we link to the timestamp of 2.0 billion years ago, were most intensively implemented.

Conclusions
The Orikhovo-Pavlograd suture zone is a complex dislocation formation, because it was formed in several stages of tectonic-metamorphogenic transformations of the crystal base.The first five of them appeared under P-T conditions from granulite to greenschist facies of metamorphism, the next ones -at low temperatures.Despite the multi-stage and multidirectional deformation processes within the zone, its structure is dominated by submeridional anisotropy.This is due to the submeridional linearization of heterogeneous and multi-age Geological objects in the same direction [10].Such a structure as a whole can be defined as a subvertic secondary monoclinal, reinforced with melange.
The Pivnichno Tersyansk folded form is a highly coordinated dislocation structure that was formed under significantly shifted tectonic conditions.It takes the position of a motor roll structure, which was finally created at the 4th and 5th stages of structural and material transformations of the Precambrian basis.This is about 2.0 and 1.9 billion years ago.We have attempted to restore such transformations in the form of a step-by-step model of the evolution of the structural-material pattern of the studied crystal base fragment (figure 9).Based on similar data on the structural and material organization of megablocks adjacent to the Orikhovo-Pavlograd zone [17], we form the basis of the scheme in figure 9 the vision that the Precambrian basis, within the limits of these components, at the initial stages of their formation (I -III in figure 9) had a single structural plan (the same both within the suture zone and within adjacent Megablocks).At the final stages (IV-V in figure 9) development within the suture zone was dominated by significantly shifted geological and dynamic conditions (relative to adjacent megablocks).An idealized model of the formation of a single U-, Th-promising structure has been created, which will contribute to a more targeted search for uranium-thorium mineralization and expand the mineral resource base of the nuclear power industry in Ukraine according to the final result.

Figure 1 .
Figure 1.Stereograms of the poles of the planes of striation and shale formation and immersion of linearity along mineral aggregates and folded axes for conducting petrotypes of the Orikhovo-Pavlograd suture zone.Projection on the lower hemisphere.Gradation of isolines: 1-2-3-4-5-6-7-8-9-10-11-12-13-14-15.Arrows -directions of action of tectonic stresses (for simplification shown by one Arrow): Black straight lines -compression, white lines -stretching; rounded lines -rotation, crosses -their axes.The numbers next to it are the stage index.n -number of measurements.

Figure 2 .Figure 3 .
Figure 2. Multi-stage structure of Feldspar quartzites of the Orikhovo-Pavlograd suture zone.a -general view in the vertical plane -b: c Y 4 (exposure South), visible lens L 1 ; b -in the plane a: b Y 4 , where you can see several generations of linearity (underlined with lines; vertical slice, eastern exposure.Scale -coin 10 kopiyok); c, d -a larger image in the plane b: c Y 4 , where c is a photo, d is a schematized sketch (for the scale -pomegranate seeds with dimensions of 2 -5 mm).The frame highlights the part shown in figures e, f 1 -5-metamorphogenic dislocation structures of the corresponding generations.

Figure 4 .Figure 5 .
Figure 4. Multi-stage structure of tonalito-gneisses of the Orikhovo-Pavlograd suture zone: a -striation of two generations-Y 2 , 3 and shale formation Y 5 .In the center of the outcrop is a lenticular body close to a massive one (L 1 ) composition of tonalite-T (vertical cut in the plane b: c, northern exposition); b -flaking/de-lensing-Y 4 , T-lenticular bodies of tonalite composition (sub-horizontal section, western exposure); c -linearity (L 1 ) along the axes of folded bodies of amphibolites, singranitization striation (Y 2 , 3 ), lensing and building (Y4b-internal lined structure of the amphibolite structure with leucocratic secretions in the form of asymmetric lenses and hooks.This structure indicates the formation of amphibolite bodies by shear transformations (the plane is close to horizontal)).

Figure 6 .
Figure 6.Two generations (L 6 , 7 ) linearities (underlined by lines) in the submeridional planes of the separation of tonalito-gneiss, represented by striations, and sliding strokes.Western exposure a, b, which are framed in figure A.

Figure 7 .
Figure 7. Internal structure of granitoid bodies: a -a photo where the details shown in the lower part of the figure are framed; b -the same thing -a sketch where (for simplicity) only ribbonshaped bodies of red granitoids are displayed.Arrows -restored directions of displacements during the formation of reflected granitoids.The cut is vertical, the exposure is northern.

Figure 9 .
Figure 9. Schematized step by step (I-V) model of formation of the structural and material pattern of the studied part of the Orikhovo-Pavlograd suture zone.Arrows -restored directions of application of tectonic forces (in modern coordinates).1 -5-generation of planar structures to the appropriate stages of development of the structural plan.Gray bodies (rectangles, ovals, and irregular ones) are ore formations.3.2, 2.,8, 2,0 -isotopic age according to their predecessors.