Ingul Megablock Research Articles

U-Pb isotopes geochronology by monazite of granitoids of Krynychuvatsky massive (Ingul megablock of the Ukrainian Shield)

Pegmatite (sample 13/10) exposed in the valley of the Berezivka River (Krynychuvatka village) was studied and its isotopic age was determined by monazite. Granitoids of the Krynichuvatsky massif differ from other granitoids of the Kirovohrad complex in their petrographic composition (mainly plagioclase, plagioclase-microcline), structural (aplitoid, pegmatoid inclusions) and texture (in some areas, aplitoid granites are characterized by linearly oriented grains of lamellar (lenticular) quartz, elongated feldspar crystals) and the composition of xenoliths (amphibolites, amphibole-biotite, biotite, pyroxene-biotite gneisses). To find out the time and duration of the formation of granites of the massif using the uranium-lead isotope method, we determined the age of the monazite of the apilito-pegmatoid granite (sample 12/10) — 2039.9±1.4 Ma. The age of the vein body of the pegmatite (sample 13/10) has now been determined that is widespread above the dam on the right side of the stream, the left tributary of the Berezivka River, village Krynychuvatka. Monazite occurs mainly as large (> 0.1 mm) diskshaped crystals with well-developed pinacoid facets and, in individual grains, several other facets and even ribs. The crystals are yellow, honey yellow to honey transparent and translucent. Light-yellow, water-transparent crystals with an even, smooth, shiny surface and rounded contours are present singly. Considering the fact that the main mass of granites (aplito-pegmatoid granites) exposed in the valley of the Berezivka River (Krynychuvatka village) are 2039.9±1.4 Ma, and the vein body of peg9 matite that dissects the granite was formed in 2029.1± 3.4 Ma, it can be assumed with a high probability that the Krynichuvatsky massif was formed for at least 10 million years, in the age interval of 2040—2030 Ma ago.

Uranium-Lead Age According to Zircon of Syenites of the Velykovyska Massif (Korsun-Novomyrhorod Pluton)

The results of uranium-lead dating of zircons from syenites of the Velykovyska massif (Korsun-Novomyrhorod pluton) of the Ingul megablock of the USh are given. The Velykovyska massif, located in the southern part of the Korsun-Novomyrhorod anorthosite-rapakivi granite pluton, in the area of the village Velyka Vyska, composed of fayalite-hedenbergite syenites. Syenites are small isolated intrusive bodies that are conventionally united in the Velykovyska massif. Several varieties of syenites are distinguished by textural-structural features and mineral composition — fine-grained, medium-grained (predominant), mesocratic (10-15% of dark-colored minerals, occasionally 20-30%), leuco- and melanocratic (present in subordinate quantities) syenites according to alkali content belong to the normal series. The anatomy of zircon crystals from a sample (217/862) of syenite discovered by well 862 was studied. Zircon crystals from the Velykovyska syenite massif are quite diverse — from transparent yellow and lilac to slightly transparent brown, cracked. Zircon crystals in the syenites of the Velykovyska massif crystallized from magmatic melt, probably with a short break in crystallization. The age of the syenites of the Velykovyska massif was determined by the uranium-lead isotope method based on three size fractions of multi-grain weights of zircon crystals from the fayalite-hedenbergite syenite, sample (217/860) and two size fractions of multi-grain weights of zircon crystals of the sample (158/860) St. 860. The discordia intersects the concordia at two points: the upper crossing corresponds to the age of 1774 ± 18 Ma and the lower one — –129 ± 955 Ma. Taking into account the slight discordance (0.9-1.6), the weighted average value of the age based on the 207Pbr/206Pbr isotopic ratio was calculated to be 1776.2 ± 2.8 Ma, which coincides within the margin of error with the age calculated from the upper intersection of concordia with discordia and which we take the time of crystallization of zircon crystals and the age of the syenite of the Velykovyska massif.

NOVOUKRAINSKYI MASSIF: SOURCE OF ORIGINAL MAGMAS AND TIME OF FORMATION

NOVOUKRAINSKYI MASSIF: SOURCE OF ORIGINAL MAGMAS AND TIME OF FORMATION

BACTERIAL LEACHING OF BALANCED ORES OF ALBITITE DEPOSITS OF THE UKRAINIAN SHIELD

Prospects for increasing the raw materials resources of uranium ore deposits of the albite formation of the Ingul megablock of the Ukrainian Shield and the possibility of reducing the impact of harmful waste due to the method of bacterial leaching of metals were considered. Mineral-forming systems of uranium-bearing albitites of the Ukrainian Shield have always been considered as monoelement, exclusively uranium objects. However, their out-of-balance ores and tailings contain elevated, up to industrial, concentrations of other metals, which, under conditions of hypergenic processes, pose a potential threat of environmental pollution. In order to determine the possibility of expanding raw materials resources of albite deposits of the Ukrainian Shield due to the use of the method of bacterial leaching of metals, the composition of industrial ores and host rocks was considered. In particular, our data from their mineralogical and geochemical research showed that uranium and five of its companion elements: thorium, vanadium, beryllium, zirconium and lead reach industrial content. At the same time, cobalt, nickel and zinc are characterized by an increased content close to the minimum industrial values. The most promising for bacterial leaching are rocks that contain sulfides. The rocks of the uranium ore albitite formation contain sulfur-containing compounds and, in particular, pyrite, as well as bi- and trivalent iron. We found the highest content of sulfides in albitized rocks (up to 0.82%), ore-free albitites (up to 0.81%), low-ore albitites (up to 0.61%), that is, in rocks accumulated in industrial waste. It is assumed that the use of bacterial leaching methods with the participation of chemolithotrophic microorganisms can be promising for the processing of off-balance ores and will contribute to the expansion of the raw material base of albite deposits of the Ukrainian Shield, due not only to uranium, but also to nickel, cobalt and zinc.

Uranium-lead isotopic age of monazites of plagiogneyses of the Ingulo-Inguletse series (Ingul megablock of the Ukrainian Shield)

Among the supercrustal formations of the Ingul megablock, Paleoproterozoic rocks, represented by the Ingul-Ingul series, are significantly predominant. In general, the composition of the Ingul-Ingulets series includes (from bottom to top): Zelenorichen, Artemiv, Rodioniv, Kamyano-Kostovatsky (age analogue of Spasivsk) and Roschakhiv (age analogue of Chechelivsk) worlds. The Chechelivsk suite is represented by biotite and garnet-biotite gneisses, places with sillimanite and cordierite, as well as underlying layers of pyroxene gneisses and schists. Suite rocks are widespread within the Ingul Synclinorium, in the framework of the Korsun-Novomyrhorod pluton and in the northern part of the Bratsky Synclinorium. Currently, the age of monazites from plagiogneisses distributed in the Novgorodkiv quarry and south of the village Lavrovka has been determined using the uranium-lead isotope method. The obtained monazite isotopic age values of 2022.9 ± 6.7 Ma and 2031.5 ± 1.5 Ma, respectively, can only serve as the upper age limit for the formation of the Ingul-Ingul series. Analysis of the internal structure of zircon crystals from plagiogneiss distributed south of Lavrivka, showed that the majority of zircons are complex. In almost all crystals there are mainly thin shells of light pink zircon. Light pink zircon cores are found in the middle of the light pink crystals. Crystals with a brown color have a more complex structure. Along with isometric cores of light pink zircon, cores with fine «magmatic» zoning occur, as well as highly fractured uniform brown cores and complex cores.On this basis, it is assumed that this plagiogneiss was formed by clastogenic material from several sources.

ГЕОДИНАМІКА УРАНОВОРУДНИХ ПОЛІВ ЗАХІДНОЇ ЧАСТИНИ ІНГУЛЬСЬКОГО МЕГАБЛОКУ УКРАЇНСКОГО ЩИТА

The Ingul megablock of the Ukrainian Shield contains a number of endogenous deposits of the sodium-uranium formation, which have been developed for more than 55-60 years. With the exception of the Kirovograd uranium ore region, the deposits of which are controlled by discontinuities in the fault zone of the same name, the Vatutinske and Novokostiantynivske ore fields occupy positions within the Novoukrainsky granite-gneiss dome and in close proximity to the later geostructural formation, the Korsun-Novomyrgorod pluton. Paying attention to the high degree of saturation of the Ingul megablock with endogenous uranium deposits, it is emphasized that they also contain an increased content of thorium minerals and, in combination with uranium, they produce ascending gas flows of radon. Therefore, studies of the dynamics of the upper horizons of the lithosphere and the closely related dynamics of the hydrosphere (underground and surface), as well as the gas sphere, are especially relevant both in the regions of uranium ore fields and in areas adjacent to mining enterprises. Beyond the direct influence on the radioecological situation of uranium mining enterprises, special attention should be paid to the study of the dynamics of the lithospheric surface, including fault-block structures and the kinematics of ruptures, affecting the spread of groundwater and, as a result, surface waters contaminated with uranium in the environment. In the areas of uranium ore fields, the kinematic characteristics of disjunctivals contribute to a more correct forecast of radon accumulation in natural weakly insulated underground decompressed structures and the accumulation of more long-lived products of its decay Po, Bi, and Pb with long periods of removal of biological objects from organisms. It is emphasized that in the mine workings of mining enterprises, the technological process is accompanied by nitrate pollution of groundwater due to the use of nitrate-based explosives. Thus, for the predictive assessment of radiation and nitrate pollution of the environment of industrial sites of mining enterprises and adjacent territories, the technological process of which also affects the dynamics of the litho-hydro- and gas sphere, the structural-geological, paleogeomorphological, lithological, hydrogeological, hydrographic and topographic features of the Vatutinske and Novokostiantynivske uranium ore fields. The directions of the advancement of the groundwater fronts from directly uranium mines to the nearest drains have been established. The levels of uranium pollution of surface and underground (well) waters within the Novokostiantynivske uranium ore field, as the most promising for increasing uranium mining in the coming decades, have been determined. The proposed areas and terms of complex radioecological monitoring of the Novokostiantynivske uranium ore field in order to take preventive measures to prevent the withdrawal of existing local recreational areas and water areas into the category of ecologically hazardous. On the example of the Novokostiantynivske uranium deposit, as one of the richest endogenous deposits in Ukraine, through the production shafts, which is planned to rise to the surface of uranium ore from the same type of deposits of the uranium ore field of the same name (Lisne, Litniy and Dokuchaivske) by transporting it by main drifts, the proposed optimal complex of geodynamic studies in the system of radio and general ecological monitoring of the state of the environment of such territories.

Density heterogeneity of the Earth’s crust of Ukraine and adjacent territories from three-dimensional gravity modelling

The work was performed to study the density heterogeneity of the crust of Ukraine and adjacent regions analyzing detailed 3D gravity models of the following tectonic regions and separate structures: Dnieper-Donets Basin and Donbas, Ingulsky megablock, Golovanivska suture zone, latitudinal zones of fractures of the Ukrainian Shield, Black Sea megadepression and surrounding areas. The models are constructed on the basis of geological, petrophysical and seismic data along geotravers, DSS profiles, the modern WARR methodsand are calculated using the automated software complex for interpretation of potential fields GMT-Auto. As a result, new information was obtained for the density distribution in the whole Earth’s crust.The density distributions construct for the entire crust of Ukraine and adjacent regions at certain depths (surface of the basement, 10, 20, 30 km, Moho discontinuity). The thickness was determined for conditionally distinguished «granite», «diorite», «basalt» layers of the Earth’s crust and crust-mantle mixture within the whole region of the study. Its values are graphically represented by isolines on the respective schematical maps. The resulting density inhomogeneity became the basis for constructing, for the first time in a three-dimensional version, a scheme for the predictive composition of the Earth’s crust with typification according to the power ratios of its constituent layers. The heterogeneity of the present-day consolidated crust of the whole study area is characterized by granitic, granitic-dioritic, dioritic and basaltoid types. To clearly identify the dismemberment of the lower layer of the crust which is considered inseparable by the classification of the DSS method the basaltoid type is divided into 3 subtypes. The subtype 1 with a content of 40—70 % of basalt, subtype 2, where concent-ration of basalt increases to 70—90 % and subtype 3, which is composed only of basalt.It has been established that the basicity of the Earth’s crust of the USh changes from west to east, respectively, from basalt to diorite type. Decrease in crustal basicity is also observed in suture zones, namely from diorite and basaltoid typein Golovanivskii suture to basaltoid and diorite type in the Inguletsko-Kryvorizckii suture and diorite type in the Orikhivsko-Pavlogradskii suture. In the DDB the crustal basicity increases from northwest to southeast in accordance with the segmentation of this feature. The basaltoid type of the crust is predominant in the Black Sea megadepression and adjacent territories. For the first time, a type of crust was identified that does not coincide with the known ones and is characterized by the presence in the section of the «basalt» and «granite» layers (with a zero or very low «diorite» thickness). A similar type of bark is present in the Ingul megablock of the USh, in the northern side zone of the DDB, as well as in the Black Sea megadepression.

Dyke Rocks of the Korsun-Novomyrhorod Anorthosite-Rapakivigranite Pluton

In spite of significant intensity and composition variability of dyke magmatism in the Ingul mega-block, in the Korsun- Novomyrhorod anorthosite-rapakivi granite pluton (KNP) dyke magmatism is restricted. To present day, dykes of basic composition have not been described in this pluton. Previously mentioned gabbro-diabases dykes or diabase porphyrites should be classified as medium rocks as well as they are enriched by SiO2, Na2O and K2O. The authors succeeded studied the dyke from the Nosachiv massif, which can be considered the only known dyke of basic composition in KNP. By chemical composition, this rock is similar to the Ti-enriched gabroids of KNP, but differs in the presence of high-Ti magnetite (not typical mineral in plutonic rocks of KNP), and in terms of SiO2 and Na2O + K2O it should be classified as subalkaline. Most of the dikes known in the KNP are mainly monzonites, monzosienites, less widespread syenites, granite dikes are quite rare too. As our studies have shown, in the previously described porphyry dykes diabase structure is not exihibited. Furthermore pyroxene content is the first percent, and a significant (or most) of them are probably xenogeneic. According to chemical composition such dykes should be classified as medium in composition, because the SiO2 content in them is in the range of 54-60 % and elevated content of K2O, often prevails over Na2O, by low MgO and higher TiO2 they are similar to gabroid of KNP. In these rocks, normative orthoclase and quartz are calculated in significant quantities. Therefore, we offer to consider these rocks as dyke analogues of monzonites (quartz-containing or quartz) and regard as monzonite porphyry. The significant distribution of monzonites and syenites and their dyke analogues denote clear pronounced monzonite-syenite trend of evolution in KNP.

Uranium-Lead Geochronology on Monacite of Granites of the Lypnyazka Massif and its Framing (Ingul Megablock of the Ukrainian Shield)

The Lipnyazka massif is located in the Dobrovelychkivsky district of the Kirovohrad region, v. Lipnyazka and further south. Structurally, it is located within the Bratskyy Synclinorium of the Ingul megablock and coincides with the Mikhailovsky anticline. The main petrotype of the massif rocks are porphyry-like granites, often with a gneiss-like texture, aplito-pegmatoid, pegmatoid granites and pegmatites. The latter most often form secant vein bodies. Uranium-lead isotopic dating of granitoids of the Lipnyazka granite massif has been performed, with which a number of deposits and ore occurrences of rare elements, primarily lithium, are spatially and probably genetically connected. The age of porphyry-like granites (2032 ± 6 million years), which is the main petrotype of rocks distributed in the area of the village of Limestone and pegmatoid granites (2027 ± 1 million years), which cut porphyry-like in the form of vein bodies. Aplithoid framed granites (2046 ± 8 million years old), common in the area of the mouth of the Sukhyi Tashlyk River (Dobryanka village), are somewhat older. Based on the results of determining the isotopic composition of strontium in the accessory apatite of granites, a conclusion was made about the upper crust source of granites of the Lipnyazka massif (87Sr/86Sr – 0.730-0.785).

The Bug mining area of the Ukrainian shield. Structural-petrophysical map of the crystalline basement and some problems of the Early Precambrian geology

Structural and petrophysical map of a scale 1:100 000 of the Bug mining area (BMA), one of the most promising areas of ore minerals in the eastern part of the Ukrainian shield has been built. The area is located in the Middle Bug (sheets of topographic map M-35-XXXVI-eastern half and M-36-XXXI). Materials of geological survey of a scale 1:50 000, deep geological mapping of a scale 1:200 000, exploration, as well as: geophysical surveys of a scale 1:10 000—1:50 000, seismic and geoelectric deep sounding; special tectonic works on outcrops; published results of determining the isotopic age of Precambrian rocks have been put into the basis of the constructions.Authors tried to enclose only indisputable data such as material composition, structural and textural features, petrophysical characteristics of rocks, the contours and dimensions of bodies by geophysical data and drilling, tectonophysical parameters of discontinuous structures directly in the map content.Unclear and discussion debatable points on the map are not shown and discussed in the text. These problems include the tectonic position of BMA (the Bug Mining Area), which, according to the authors, belonged to the Bug megablock in the Archean and in the Proterozoic it was divided by the fault Talnov zone and as a result of the process of shifting-pulling apart its eastern part joined the Ingul megablock. The deep crust-mantle nature established in the territory of BMA of the large Golovanevsk and Bandurivka gravitation anomalies have been shown.The authors rejected the division of Early Precambrian rocks of granulite facies into suites as because the principle of a sequence of strata and correlation of sections in the area is not observed. The problem of the scope of the Dniester and Bug series from which rocks of Proterozoic kinzigite formations were excluded is being discussed here. Particular attention has been paid to the mechanisms of formation of subvertical layered banded structure of thickness of Early Precambrian granulite complexes of the area. It is shown that this structurally textured rock fabric formed in the early Proterozoic as a result of horizontal forces and horizontal movements of the substance and the folding has mainly near-fault shift character with subvertical hinges of folds, which is clearly seen in the horizontal sections and by the results of drilling.

ПЕРШІ РЕЗУЛЬТАТИ ІНТЕРПРЕТАЦІЇ ЗА СЕЙСМОТОМОГРАФІЧНИМ ГЕОТРАВЕРСОМ "ВІННИЦЯ – ТАГАНРОГ"

Methodological aspects and results of studying of the stratigraphic section of the upper mantle along the seismic tomographic geotraverse "Vinnytsia – Taganrog" are considered in the article. To localize mantle anomalies associated with changes in the composition, density of the substrate, temperature, etc., an analysis of the curves of the first and second velocity gradients was used to search for the inflection points of the vp curve. A velocity curve was obtained by constructing a seismotomographic model using the Taylor approximation method. Before the curvature analysis, a smoothing procedure was carried out in accordance with the wavelength. This procedure is important for screening false anomalies, the size of which is responsible for Fresnel zones, since the resolution of the seismic wave has the dimension of the Fresnel zones. According to this technique, the curves of the first and second velocity gradients vp were calculated for the upper mantle under the main tectonic structures of the Ukrainian Shield along the "Vinnytsia – Taganrog" geotraverse. The profile crosses the Podol, Bug megablocks, Golovanev suture zone, Ingul megablock, Kryvyy-Rig-Kremenchug suture zone, Middle-Dnipro megablock, Orekhovo-Pavlograd suture zone and Azov megablock. According to the results, the most significant features of the mantle structure were identified in the depth interval of 50–750 km. A transregional tectonic zone was distinguished (between points 30.0E, 49N and 32.0E, 48.25N), over which the Golovan suture zone (GSZ) and the eastern part of the Bug-Ros megablock and the western part of Ingul, where significant violations of the common mantle border of 660 km are observed – a border between the upper and middle mantle. Under the Podol megablock, this border is located at a depth of 550–560 km. Under GSZ it rises to 450–460 km, and to the east of the suture zone it drops sharply to 660-670 km, where it takes a subhorizontal position. A sharp jump to marks of 450–460 km shows the global breakdown zone and the nature of the contact between different geodynamic mantle regions under the modern platform.

Ta-Nb mineralization in rare-metal pegmatite from north-western frame of Lypniazhka granite-migmatite structure

The three type of rare-metal pegmatites are know in Stankuvatske ore field (Ingul megablock, the Ukraianian Shield), such as: Li-bearing, Bi-As-U and Ta-Nb pegmatites. For the first time Ta-Nb mineralisation from Ta-Nb bearing albite-K-Feldspar rare metal pegmatite have been described. Investigated pegmatite is located on the Norh-West frame of the Lypnazky granitemigmatite massive among hosted amphibolites. Rare-metal pegmatite doesn’t have obvious zonality and consist of alkaline feldspar, biotite, muscovite, dark to black colour quartz, blue-greenish apatite, nigerite, gachnite, tourmaline, monazite. The primary ferrocolumbite and Nb-rutile-II have undergone strong hydrothermal alteration. Thus primary rutile-II decomposed with formation of skeletal intergrowths of secondary cassiterite and rutile-III with a much lower volume of Nb and Ta under the influence of hydrothermal fluid. Primary homogenous Nb-rutile-I (Nb2O5+Ta2O5 from 33,5 to 42,9 wt.%) exsolved a fine trellis-like pattern and lamellar of Nb-pure rutile-III, cassiterite and Mn-rich ilmenite. The Nb-rutile-II is occurred in tabular grains with unclear internal zonation. Primary ferrcolumbite breakdown to Ti-ixiolite and Nb-rutile-III. Primary oscillatory zonality is transformed into irregularly patchy and veinlety. Recrystallized ferrotantalite is secondary and uncommon mineral. Ferrocolumbite contains 2.93 to 4.74 wt.%TiO2, and titanian ixiolite 7,33-10,76 wt.%. The (Ti,Nb)>Ta mineral assemblages, and compositional trend of columbite with very low Ta/(Ta+Nb) and Mn/ (Mn+Fe) imply a general low level of fractionation in comparison with typical beryl-columbite rare-metal pegmatites.

Uranium-lead age of granites Chigirin massif

The age of granites of the Chyhyryn massif – 2040.0 ± 1.1 million years – was determined by the uranium-lead isotope method for accessory monazite. According to the results of mineral studies of zircon crystals, the conclusion that granites this mass, as well as granitoids of Novoukrainsky, is formed due to the crust, which indicates the presence of relict nuclei of substrate rocks in the middle of the crystals of this mineral. It is proposed to combine in one (for example, Kropyvnytskyi) complex All two-field spar granitoids of the Ingul megablock, leaving in the composition of the new Ukrainian just gabbroids, intrusive nature and a deep source that does not create doubts. The Chyhyryn massif has an area of over 3,500 km2, located in the northern part of the Ingul megablock. The main volume of rocks that make up the array is occupied by granites, which in their composition correspond to the granites of the Kirovograd complex. According to structural features, trachytoid and porphyritic granites differ among them, and biotite and garnet-biotite granites differ in composition. The inclusions are usually represented by a microcline (occupying 40-50% of the rock volume), having a tabular shape, 3-8 mm in size, which often contain small inclusions of quartz and plagioclase. Large plate crystals of the microcline are often crushed from the edges. In addition to the microcline, plagioclase crystalline crystals up to 5 mm in size occur in areas. Porphyry-like granites of the Chyhyryn massif, common within the Golovkivsky quarry. Monocytes from biotite granite were dated to determine the time of formation of the Chyhyryn massif. Granite was selected in the Golovkivsky quarry, located south of the village. Skelivka.

Rare-earth accessories and secondary minerals in plagiogneisses from the Stankuvatske Li-deposite

The Stankuvatske Li deposit (SD) is situated at western flank of the Lypniazka structure (Ingul megablock of the Ukrainian Shield). Knowledge about REE content in host metamorphic rocks is based on the results of bulk chemical analysis, but their minerals have not been determined. For the first time rare-earth mineralization of the Stankuvatsky lithium deposit has been investigated in fine-grained gneiss with «augen» and schistose structure, porphiroblastic texture, formed as result of tectonical alteration. Our investigations were carried out using petrographic and microprobe analysis (EPMA). Mineralogically gneisses consist of quartz, plagioclase, zoizite, biotite, graphite, chlorite and abundant sulphides mainly represented by pyrite, arsenopyrite, sphalerite, molibdenite. Accessory minerals presented by titanite, apatite, monazite, zircon and coffinite. Gneisses have been subjected to deformation and hydrothermal — metasomatic alteration. An investigation of rock-forming and accessory minerals allows to revel low-temperature alterations of primary allanite by bastnäsiteand chlorite with formation of secondary bastnäsite-chlorite-coisite-pyrite association with «coronary» texture. The penetration of S, F, CO2, H2O enriched fluids were caused disintegration, partial redistribution and reprecipitation of rare earth elements. As result synhysite-chlorite-pyrite association was formed.

Problems of Precambrian paleomagnetism on the territory of Ukraine

Some problems of paleomagnetic research of the Precambrian rocks of Ukraine are considered. The results of paleomagnetic researches of the Proterozoic rocks of the Ukrainian Shield, Ediacaran traps of Volyn and sedimentary rocks of Podolia were analyzed. With the emergence of many new isotopic age data for the Ukrainian Shield rocks we have new opportunities to get reliable palaeomagnetic poles. But our studies of the pilot collections of samples from some key outcrops in the Middle Dnieper, Azov, Dniester-Bug, Ingul and North-Western crustal blocks of the Ukrainian Shield with modern geochronological isotopic ages showed their absence of informativity for palaeo-magnetic determinations. On the Ukrainian Shield the gabbro-anorthosite and granite rapakivi of Korosten and Korsun-Novomyrhorod anorthosite-mangerite-charnockite-granite complexes in the northwestern and central part of the shield are good candidates for palaeomagnetic investigations. New paleomagnetic pole (Φ = 22.7°N, Λ = 164.3°E, dp/dm = 4.9°/9.6°) for ages of 1750 Ma were calculated for six sites within Ingul mega-block. Based on the analysis of paleomagnetic poles for Fennoscandia and the Ukrainian Shield the model of relative position and orientation of these blocks at 1770 and 1750 Ma were calculated. About 1770 Ma Fennoscandia and the Ukrainian Shield occupied low latitudinal positions (15° N and 2° S respectively). At the same time the Ukrainian Shield was rotated anticlockwise about 40° relatively to Fennoscandia. In the next 20 Ma Fennoscandia and the Ukrainian shield drifted southward at about 5° and occupied 10°N and 7°S paleolatitudes respectively, but relative rotation of blocks almost did not occur. The average speed of latitudinal drift of both blocks was near to 2.8 cm/yr. The new results of paleomagnetic studies of Volhyn basalts of Ratnenska suite are presented. We assume that the geometry of the geomagnetic field was not dipole as one of the interpretation of these results. In this context we should study of whole Volyn traps sequence from boreholes and Ediacaran—Cambrian sequences of Podolia in order to gather some data about frequency of geomagnetic reversals.

New results of the lithological and paleontological study of the Middle Eocene biogenic siliceous rocks of the central part of the Ukrainian Shield

The present paper contains new results of complex studies on the geological structure, lithology, and fauna of the Middle Eocene siliceous rocks of the Ukrainian Shield Ingul megablock located in the vicinity of the villages of Tsybulevo, Verblyuzhka and Pervozvanovka of Kirovograd Oblast and Voronovka village of Mykolayiv Oblast. Based on new findings and analysis of malacofauna, the Middle Eocene age of the gaize-like sandstones of Verblyuzhka village was confirmed. For the first time, numerous remains of rock-forming organisms such as sponges (lithistid Demospongiae), coralline (Corallinaceae) and green algae (Dasycladales, Halimedaceae) have been found in the siliceous deposits of this region. In addition, biogenic buildups formed by organisms with carbonate (coralline and green algae, large foraminifera) and silicate (lithistid sponges) skeletons were found for the first time in the siliceous rocks of the Pervozvanovka deposit. The observed biogenic lepispheres in the studied rocks suggests that the latter have been formed with active participation of silica-producing bacterial communities. Based on the first finds of zeolites, as well as montmorillonite traces, it is forecast that "disguised" pyroclastic material is present in the gaize-like sandstones of Voronovka village. Analysis of the lithological features and the mineral and faunal composition of the studied rocks allow us to draw a conclusion about the multi-stage genesis of the Middle Eocene siliceous deposits in the central part of the Ukrainian Shield and the influence of Paleogene volcanism on their formation. It appears that volcanic activity and denudation of volcanic products caused a massive flow of SiO2 into the waters of the Middle Eocene paleobasin. This contributed to the widespread development of siliceous-skeleton organisms (in particular, silica-producing bacterial communities) that actively participated in the formation of siliceous rocks.

ISOTOPE-GEOCHEMICAL AND GEOLOGICAL-GENETIC CRITERIA FOR SEARCH OF URAN AND GOLD DEPOSITS OF THE INGUL MEGABLOCK OF THE UKRAINIAN SHIELD

The system of isotope-geochemical criteria of forecasting and prospecting for the Early Proterozoic deposits of albitite (sodium-carbonate) and low-sulfide gold-quartz (with telluride's) ore formations was elaborated for the first time. The first is represented by Severinovsky, Michurinsky, Yuryevsky, Vatutinsky and Novokonstantinovsky deposits of uranium, the second – by the East-Yuryevsky gold deposit. The basis of isotope-geochemical criteria (regional and local) is laid, given in the development of geo-genetic features of mineralization. Regional features equally characterize the deposits of both formations, to which we can refer the geological factors of ore control for the entire Ingul block. Local criteria characterize individual ore zones or even ore bodies; their isolation requires a detailed study of ore matter and is therefore given separately for gold and uranium ores.Key words: isotopic and geochemical criteria, albitite formation, little sulphide gold-quartz formation, Ingul megablock, Ukrainian Shield.

ГРАНИТОЇДИ, РІДКІСНОМЕТАЛІЧНІ ПЕГМАТИТИ ТА ТA-NB МІНЕРАЛІЗАЦІЯ ШПОЛЯНО-ТАШЛИЦЬКОГО РУДНОГО РАЙОНУ (ІНГУЛЬСЬКИЙ МЕГАБЛОК, УКРАЇНСЬКИЙ ЩИТ)

Composition of granites, genetically associated pegmatites and superimposed metasomatites distributed within Shpoliano-Tashlyk ore area (Ingul megablock) is considered. It is established, that on the basis of similarity in their petrographic and petrochemical features granitoids of the area can be related to single complex. Features of ore mineralization are defined by both composition of granitoids (Sgranites) after which rare-metal pegmatites are formed and intensity of superimposed metasomatic alterations. Main minerals-concentrators of Ta and Nb mineralization in granitic pegmatites and metasomatites are represented by minerals of three isomorphic series – columbite-tantalite (Fe,Mn)(Nb,Ta,Ti)2O6, ilmenorutile-struverite (Ti,Nb,Ta)O2 and pyrochlore-microlite (Ca,Na)2Ta2O6(O,B,OH,F). Depending on geological setting such ore minerals as tapiolite, ixiolite, cassiterite, uraninite, nigerite, gahnite are commonly found in association with these minerals. Chemical composion of tantalo-niobates sampled from ore-bearing pegmatites and metasomatites is investigated by microprobe analysis. Most minerals of columbite-tantalite series are characterized by distinct and rhythmic internal zonality and contrasting mosaic structure which are related to considerable heterogeneities of their chemical composition. Within one aggregate mineral phases with wide range of values – from 9,80 to 71,0 % for Ta2O5 and from 10,6 to 70,1 % for Nb2O5 – are established. Among minerals ferruginous varieties which composition relates to Fe-columbite-tantalites (Nb2O5/Ta2O5 = 1–1,2; FeO/MnO = 2,5–6) prevail. Columbite-tantalites are characterised by high contents of admixture elements present (%): TiO2 – to 5,88; WO3 – to 3,70; SnO2 – to 9,20; Sc2O3 – to 5,40. Scandium ores occur as scandium-rich minerals that are mostly confined to the minerals of columbite-tantalite series found in Polohivka ore field. On the Ukrainian Shield high contents of Sc2O3 in tantalo-niobates are established for the first time. Minerals of ilmenorutile-struverite series do not quantitatively yield to minerals of columbite-tantalite series. For minerals of this series Nb2O5/Ta2O5 ratio varies in the range of 0,6-1,4. Among characteristic admixture-elements are prevailed (%): SnO2 – to 3,1, V2O5 – to 5,05; FeO – to 11,51, Cr2O3 – to 1,20. Minerals of pyrochlore-microlite series are of subordinate importance. For the first time by results of U-Pb dating of columbite-tantalites from Mostove ore manifestation (Shpoliano-Tashlyk area) the age of Ta-Nb mineralization is established to be about 1965 ± 25 million years.

ГЕОХРОНОЛОГІЯ ЛІТІЄНОСНИХ ГРАНІТОЇДІВ ІНГУЛЬСЬКОГО МЕГАБЛОКУ (УРАЇНСЬКИЙ ЩИТ)

Rare-metal elements are strategic metals which, in general, are extremely important for economic development or maintenance of defence capability of any country at the modern level. The list of needs for these strategic metals ranges depending on the level of economic development of certain country, but in general it includes such elements as Li, Ta, Nb, Be, Sb, W, REE and others. The majority of these elements has the lithophilous nature and, therefore, is characterized by close genetic relations with granites and pegmatites associated with them. In the world, industrial production of lithium is shared between deposits to lithium-bearing brine of saline depositions of marine basins (Argentina, Chile), some granites (China) and rare-metal pegmatites (Australia, China, Zimmbabve). In pegmatites lithium mineralization is represented mainly by spodumene (LiAlSi2O6), But other lithium-containing metallic minerals can also play an important role in production of this metal – petalite (LiAlSi4O10), minerals of lepidolite (Sa [Li,Al]3[Si,Al]4O10[F,OH]2) and amblygonite-montebrasite (LiAlPO4 [F,OH]) series. Rare-metal pegmatite of Ingul megablock of Ukrainian Shield can be treated as unique (insufficiently studied in world practice) pegmatitic formations in which the main metallic mineral is represented by petalite. In metallogenic interpretations two ore districts can be distinguished within the megablok, that are specialized on rare metals (Li, Rb, Cs, Be, Ta, Nb, Sn) – Polohivka and Stankuvatka. Deposits and numerous ore manifestations of rare metals formed in rather similar geological and tectonic conditions and have many common features – both country rocks composition and mineralogic composition of ores. Within Ingul megablock (Shpola-Tashlyk rare-metal district) a number of lithium rare-metal deposits associated with pegmatites is discovered. In order to determine the age of lithium mineralization in granites of Lypniazhka, Taburyshche massifs and vein bodies of pegmatitic and aplito-pegmatitic granites, which are selected from different localities of this megablock, are dated by U-Pd isotopic method by monazites. It is established that emplacement of vein granites of Ingul megablock occurred within rather narrow age interval – 2040-2020 Ma and it is not significantly separated in time from formation of most granitoids they are spatially associated with. This fact, together with geological evidences, gives grounds to make the assumption that rare-metal lithium pegmatite are formed in the same age interval.

Earth’s crust composition of the Ingul megablock of the Ukrainian Shield (types of crust) and patterns of location of ore mineral resources

Within the Ingul Megablock of the Ukrainian Shield, according to the data of three-dimensional density modeling, at the scale of 1 : 200 000, the thickness of conditionally allocated “granite”, “diorite”, “basalt” layers, which abroad have the name of the upper, middle and lower crust, are determined and their characteristic is given. In relation to the thickness of each layer to the total crust, which is expressed in parts, four types of crust are distinguished: granite, diorite, leuco-basalt, basalt. Since the composition of the Earth’s crust is an important factor in assessing the prospects for minerals, a comparison of the location of the ore deposits of manifestations of hydrothermal and hydrothermal-metasomatic genesis with a real composition scheme is made. It is established that most of the deposits of minerals are confined to blocks of granitic-diorite and diorite types of crust, and the smaller — gravitates to blocks of leuco-basalt and basalt types.