Granitoid Massif Research Articles

Uranium in groundwaters of North Kazakhstan

Relevance. The need to dentify the characteristics of the distribution of radioactive elements in the groundwater of Northern Kazakhstan. Aim. Generalization of available data on the geochemistry of groundwater and uranium and radon distribution in them using the example of the northern regions of the Republic of Kazakhstan. Methods. Generalization of long-term hydrogeochemical research and compilation of an electronic data bank on the territory of Northern Kazakhstan. A laboratory study of the chemical composition of groundwater was carried out at the Research Laboratory of Hydrogeochemistry of the School of Natural Resources Engineering of Tomsk Polytechnic University. Measurements of 222Rn contents in waters were carried out using the Alfarad Plus complex in the Laboratory of Hydrogeology of Sedimentary Basins of Siberia, Institute of Geology and Geography, Siberian Branch, Russian Academy of Sciences. Results. The groundwater of aquifers of different ages, distributed in the territory of Northern Kazakhstan (North Kazakhstan uranium province), was studied. Two geochemical sets of groundwater were identified. The first is characterized by the dominance of HCO3– and Mg2+ in the water composition, and the second by Cl– and Na+. A change in composition and an increase in the value of total mineralization from 0,1 to 49 g/dm3, in the direction from north to south, indicate the development of continental salinization. In natural waters of the first group, uranium content varies from 0.065 to 16000 μg/dm3 and radon activity from 4 to 3885 Bq/dm3. For sodium chloride waters of the second set, concentrations can reach 32500 μg/dm3, and radon activity is 6–59 Bq/dm3, since the emanating reservoir (granitoids) is located to the north – at a distance of 80–100 km. Naturally, granitoid massifs of the studied region are sources of uranium. Their drainage by the river network leads to its removal and concentration on geochemical barriers in the groundwater of the Neogene-Quaternary aquifer. This distribution of radioactive elements is associated with the high migration ability of uranium in solution in the form of uranyl ion in oxidizing geochemical conditions.

Utilizing compositions of zircon and apatite for prospecting of Cu-Mo-Auporphyry mineralization in the Pekinsky and Tessemsky granitoid massifs of the Taimyr-Severozemelskaya folded area

Research subject. The Tessemsky granite massif is located in the North Taimyr tectonic zone, surrounded by Cambrian rocks. The Pekinsky granite massif is located within the Central Taimyr zone, surrounded by metamorphosed Proterozoic rocks. Aim. To develop a methodology for using the composition of accessory granitoid minerals when prospecting Cu-Mo-Au-porphyry mineralization on the example of the Pekinsky and Tessemsky granitoid massifs of the Taimyr Peninsula. Materials and methods. Accessory zircon and apatite contained in two granitoid samples from the Pekinsky massif (P1, P2) and two granitoid samples from the Tessemsky massif (T2, T3) were studied. Their mineral composition was examined using an EPMA Cameca SX100 instrument. The element content in minerals was determined by LA-ICPMS using an NexION 300S instrument equipped with an NWR 213 attachment. Results. Most of the zircons from the Pekinsky and Tessemsky massifs were formed at T < 738°C in oxidized magma with ΔFMQ of 0.6–2.6, which is a favorable sign for the identification of Cu-Mo-Au-porphyry mineralization. Zircons are characterized by elevated (Eu/Eu*)Y and (Ce/Nd)n/Y ratios, which is also a favorable, though not a strongly reliable, sign for identifying porphyry mineralization. The Eu/Eu* and Sr/Y ratios in the apatites from the Tessemsky massif are higher than those in the apatites from the Pekinsky massif. The rock compositions of both massifs fall within the fields of adakites on the classification diagrams. The estimates of oxygen fugacity (logfO2) calculated from Mn in apatites for four samples agree well within the error limits. Conclusion. Specific features of using the composition of accessory minerals (zircon and apatite) for prospecting the Cu-Mo-Au-porphyry mineralization associated with granitoids were considered. Accessory indicator minerals can be used to rank granitoid massifs in order to assess their ore content. The example of two granite intrusions of the Taimyr Peninsula made it was possible to show that the Tessemsky massif is more promising for the discovery of associated Cu-Mo-Auporphyry mineralization than the Pekinsky massif.

EARLY NEOPROTEROZOIC GRANITOIDS IN THE RYAZANOVSKY MASSIF OF THE YENISEI RIDGE AS INDICATORS OF THE GRENVILLE OROGENY AT THE WESTERN MARGIN OF THE SIBERIAN CRATON

Studies of the geological history of the Yenisei Ridge are important not only for understanding the tectonic evolution of mobile belts at the boundaries of ancient cratons but also for problem solving whether the Siberian craton was a part of the Rodinia supercontinent. The mineralogical-petrological, geochemical and isotope-geochronological studies yielded new data on the petrogeochemical composition, petrogenesis features, U-Pb age of zircon, and Sr and 147Sm-143Nd isotopic parameters for the rocks of the Ryazanovsky granitoid massif located near the Yenisei fault zone of the Yenisei Ridge. These rocks are represented by high-ferruginous peraluminous varieties and are comparable to A-granites or highly differentiated I-granites. Their composition evolves from normal to subalkaline granites and leucogranites, characterized by increased concentrations of highly charged and radioactive elements. Isotopic (Sr, Nd) characteristics of the rocks indicate generation from an ancient crustal substrate, the average age of which corresponds to the Paleoproterozoic. The formation of these granites at the Meso-Neoproterozoic boundary (1013±9.9 Ma) corresponds to the early stage of the Grenville orogeny and the formation time of the structure of the Rodinia supercontinent. This episode of regional crustal evolution is correlated with the synchronous successions and similar style of tectonothermal events on the periphery of large Precambrian cratons (Laurentia and Baltica), thus confirming the reliability of the proposed paleocontinental reconstructions of incorporation of the Siberian craton into the Rodinia.

Nd isotope systematics of Late Paleozoic granitoids from the Western Transbaikalia (Russia): Petrological consequences and plume model testing

Late Paleozoic granites of the Angara-Vitim batholith (AVB) occupy an area of 200,000 km2 in Western Transbaikalia (the eastern part of the Central Asian fold belt). Batholith granitoids form a sheet-like body with an average thickness of 7–10 km and a volume of about 1 million km3. The granitoid massifs that make up the batholith are composed of high-potassium calc-alkaline and subalkaline quartz monzonites, quartz syenites, amphibole-biotite granodiorites, and biotite granites of autochthonous and allochthonous facies. An extremely high heterogeneity of the batholith isotopic structure was established, which basically corresponds to the parameters of uneven-aged crustal metaterrigenous protoliths. There are significant variations in εNd(Т) and accordingly T(DM-2) in granitoids of different complexes. It is assumed that the isotopic heterogeneity of AVB was formed due to the melting of a limited protoliths number that are maximally contrasting in isotopic and lithological composition: the Paleoproterozoic continental crust with εNd(Т) ≈ -20 ÷ -22 and T(DM-2) = 2.9–2.5 Ga and Neoproterozoic mafic granulites of increased potassium alkalinity, enriched in the juvenile component (εNd(Т) ≈ -3.0; T(DM-2) = 1.2–1.3 Ga). The latter were the main magmas source of postbatholitic alkali granites. Melts from these contrasting protoliths were only in some cases complementary to the salic melts sources. The main mechanism that determined the isotopic composition of AVB granitoids was the mixing of isotopically contrasting magmas in different proportions. Mingling dikes, mafic inclusions in granitoids, and synplutonic mafic intrusions in the AVB indicate an additional mixing component. It was mafic magma from an enriched mantle reactivated in the Late Paleozoic under the mantle plume influence on the heated plastic crust of a young (Hercynian) orogen.

GRANODIORITES OF OLEKMINSKY COMPLEX OF THE EASTERN TRANSBAIKALIA: U-Pb LA-ICP-MS ZIRCONS GEOCHRONOLOGY AND AGE POSITION OF COMPLEX

The palingenic calc-alkaline granitoid massifs of the Olekminsky complex form a magmatic belt stretching within the Western-Stanovoy terrane in the northeastern direction for more than 700 km. New U-Pb LA-ICP-MS dates for zircons from the granodiorites of the Marekta-Bereinsky massif of the Olekminsky complex and the granodiorites of the Yamninsky massif of the Krestovsky complex were obtained, amounting to 371±4 Ma and 364±5 Ma, respectively. These geochronological data are well consistent with the 355–358 Ma ones, therefore suggesting the Late Carboniferous age of quartz-diorite-granodiorite-granite rocks of the Olekminsky complex. However, these dates are not correlated with the existing legends of geological maps covering the area of the Western-Stanovoy structural-formation zone or the Western-Stanovoy terrane, as the intrusive formations of the Olekminsky complex are dated as the Early Paleozoic. In addition, new geochronological data call into question distinguishing of a separate Early Paleozoic Krestovsky granitoid complex.

Nyatygran intrusive suite, Bureya massif: Petrography, geochemistry, and age

The proposed review and analytical article provides updated information on the geology, petrography, mineralogy, and chemical composition of rocks of the Precambrian Nyatygran intrusive suite. The article provides a geochemical interpretation of the chemical and trace element compositions and presents the most actual data on the uranium-lead isotopic age of the rocks. The igneous formations of the Nyatygran gabbro-granodiorite-granite complex make up small intrusive massifs of gabbroids and granitoids, located near the ore-bearing Mel’gin trough, in the basins of the Verkhny Mel’gin, Chepkan, and Bureya rivers and their tributaries. In the gabbroids, the main rock-forming minerals are labradorite, andesine, bluish-green hornblende, and biotite. The gneissic granitoids are dominated by cataclastic quartz and feldspars (andesine, oligoclase, microcline) and contain abundant micas (biotite, sericite). The subalkaline leucogranites are dominated by oligoclase, quartz, orthoclase, and microcline; they also contain significant amounts of biotite and aegirine and rare amphibole (hornblende). The gabbro and gabbrodiorites of normal and elevated alkalinity are assigned to the high-aluminous high-magnesian rocks. The gabbroids represent I-type igneous rocks. The gneissic granitoids of normal and elevated alkalinity are predominantly high-aluminous, more ferroan than magnesian rocks, and are represented by S- and I-type granitoids. The determined isotopic ages of the Nyatygran suite formations are confined to the three main ranges: 933 ± 12–916,3 ± 7,2 Ma (1st magmatic phase: gabbro, gabbrodiorites, amphibole-biotite granites), 909,0 ± 6,6–907,3 ± 5,5 Ma (2nd phase: granodiorites and granites), and 806,8 ± 6,6–789 ± 4,0 Ma (3rd phase: biotite granites and granite-porphyry dikes). The Nyatygran suite age is established as Neoproterozoic and corresponds to the early Neoproterozoic, or Tonian (1000–720 Ma), according to the International Chronostratigraphic Scale, 2018. On the 3rd generation 1:1 000 000-scale State geological maps of the Russian Federation, it is presented as Early Proterozoic.

New data on the geological structure and zonality of the Vorontsovka gold field in the Northern Urals

Spatial distribution of gold, copper, and iron ore deposits in the Northern Urals with the largest Turya-Auerbakh ore region is controlled by north-west trending linear zones of a probably fault nature. The influence has been demonstrated of regional factors (including the tectonic, magmatic, and geochemical ones) favoring formation of the large Au-As-Sb-Hg-Tl Vorontsovka deposit located within a volcanogenicsedimentary, substantially carbonate rock sequence. Closely spaced swarms of Devonian pre-ore and Carboniferous post-ore mafic dykes have been identified within the deposit. The primary geochemical halos of the Vorontsovka deposit have a multielement composition and, coupled with the ores, form a thick ore-halo zone confined to the gentle tectonic contact of sandstone-siltstone and limestone units. The main halo-forming elements are zonally distributed in the section. The footwall side of the gold deposit (rear zone) is dominated by Zn, Cd, Cu, Pb, Ag, and Bi; the axial zone, by Sb, Hg, Tl, and As; and the hanging side (frontal zone), by
 As, Zn, Hg, Pb, Ag, (Cu). In the east (closer to the Auerbakh granitoid massif), Ag, Zn, Pb, Mn, Y, Mo, and W relatively accumulate, while in the west (most remotely from the intrusive), Sb, Ba, As, Hg, Co, Ni, and Sn dominate. The 40Ar/39Ar age of ~391.1 million years, obtained for hydromica of the gold-arsenic ores, corresponds to the period of emplacement of granodiorite of the final Auerbakh massif intrusive phase. The conclusion is made on the crucial magmatic contribution to the formation of gold ores of the deposit.

Structure and age of the Rassokha granitoid massif (Arga-Tas Ridge, Eastern Yakutia)

The Rassokha (Rassoshina) granitoid massif is located at the junction of the Rassokha and Argatass terranes, which are located in the western part of the Kolyma–Omolon microcontinent (superterrane), within the Verkhoyansk–Kolyma fold belt, extend in a northwesterly direction and border in the southwest with the Omulevka terrane of the passive continental margin, and in the north-the east is blocked by Cenozoic deposits of the Ozhogino depression. The massif is mainly composed of light gray, creamy massive and trachytoid porphyritic coarse- and medium-grained moderately alkaline leucogranites and alaskites. The age of the Rassokha massif and its ore mineralization was determined by a complex of isotope-geochronological methods such as U-Pb dating of zircon and Re-Os dating of molybdenite. U-Pb zircon age of the Rassokha massif is 165±0.7 Ma (n=38). The results of U-Pb dating of zircon indicate that the introduction of rocks of the Rassokha massif (alaskites, leukogranites and aplites) occurred in a relatively narrow time interval about 165 million years ago. The obtained values of the age of sulfide mineralization (179±11 million years), obtained by the Re-Os system in molybdenite isolated from alaskites, turned out to be older than the values of the U-Pb age of zircon. Most likely, some increase in the values of the Re-Os age reflects the heterogeneous isotopic composition of the captured osmium. The time of granitoids formation correlates with the early stages of Uyadino-Yasachenskiy volcanic belt formation, and most likely the massif represents intrusive part of volcanogenic belt complexes. Taking into account the geological position of the massif in the zone of the Argatass thrust, it is possible to assume the formation of granitoids in an environment of transform interaction.

The Yubileinoe Porphyry Gold–Copper Deposit (Western Kazakhstan): Geological Position and Conditions of Formation

In the Uralian Fold Belt, there are quite numerous and well-studied porphyry copper (±Mo) deposits corresponding to the traditional “diorite” (most) or “monzonite” (Talitsa, Verkhneuralskoe) models. Along with them, there are relatively small but gold-rich massifs of porphyric granitoids, including the large Yubileinoe porphyry Au–Cu deposit, which is located at the southernmost extremity of the Urals. In this study, two main types of regional hydrothermal–metasomatic alteration were distinguished based on applying quantitative petrography and areal multielement geochemical studies in the scale of the ore district: (1) an earlier synvolcanic secondary alteration of volcanics, similar to those observed in volcanic massive sulfide-bearing fields (albitization, propylitic, and listvenitic alteration) and (2) a later plutonogenic alteration of the porphyry type. The plutonogenic hydrothermal–metasomatic (HM) complex is represented by K-feldspathization, hornfels and skarn alteration at the progressive phase, and propylitization, sericitization, and beresitization at the regressive phase. They are caused by hydrothermal alteration in the apical part of the stock, composed of the mineralizing Frasnian granite porphyry complex that hosts the Yubileinoe gold deposit. A lateral series of geochemical zonality (from the periphery of volcanotectonic structures to their center) has been established for the volcanogenic stage of hydrothermal activity: CrNiCo → PbZnCuCrNi → AuAg (CrNi) → BaAuAg. A large positive anomaly of the lithochalcophilic type was found for the HM plutonogenic complex in the ore field of the Yubileinoe deposit. The concentric zonality of this anomaly is characterized by the development of Ag, W, Sn, Pb, As, and Sb halos at its periphery, and Au, Cu, Bi and Mo at its focus (“core”). The stable and radiogenic isotope geochemical data for most of the porphyry copper deposits of the Urals indicate the predominant mantle source of their rocks and ore matter. Their paleotectonic position is reconstructed as a mature stage of intraoceanic island arcs. Unlike many other porphyry objects in the Urals, the totality of geochemical, isotope–geochemical and geological features of the Yubileinoe deposit indicate the predominantly crustal magma source. According to these features, this deposit is closer to Andean-type porphyry deposits, and its position can be reconstructed as an active margin of the Mugodzhar microcontinent, i.e., a suprasubduction regime, transitional from a mature island arc to the marginal continental one. According to the complex of features, this deposit in the Urals is a close analogue of the porphyry gold deposits of the Maricunga Belt in Chile. The magmatic complexes from the Silurian (Wenlock) to the Devonian (Frasnian) age, which are parental to the porphyry gold–copper systems of the Urals, correspond to the early phase of the Wilson cycle. This phase is the most ore-productive with the formation of giant Cr and Fe–Ti–V deposits associated with ultramafic–mafic complexes. It is likely that the differentiation of mafic magmas in the large-volume chambers occurring in the lower part of the lithosphere causes the appearance (as an extreme member) of diorite melts with a noticeable enrichment in gold and copper.

Geological Position, Sources, and Age of Mingling Dikes of the Northwestern Margin of the Tuva–Mongolian Massif in Western Sangilen, Southeastern Tuva

Abstract ––The best source of information about the specific features of magmatism in collision zones is the late collisional tectonomagmatic stage, which is associated with the largest volume and diversity of the resulting magmatic associations. In this paper, granitoid and mafic late collisional magmatism is considered using the example of Early Caledonian igneous complexes of Western Sangilen (Tuva–Mongolian massif). Results of geochronological, petrographic, petrogeochemical, and mineralogical studies of the rocks of the Saizyral mingling dike and salic dikes are presented. Approximately ~485 Ma, high-potassium granitoid massifs formed simultaneously with the intrusion and occurrence of a complex of granitoid and mingling dikes. The Saizyral mingling dike resulted from the joint intrusion and mixing of basic and silicic magmas in a low-pressure region within the Erzin shear zone at a middle crust depth level. Interaction of contrasting magmas is comprised of two stages. The first stage occurs during the transport of a contrast mixture and comes down to intensive mechanical mixing and the introduction of LIL and HFS elements, as well as Th and U from granitoids into the mafic rocks. This changes the geochemical characteristics of the mafic rocks. The second stage is when the joint crystallization of magmas is accompanied by gravitational sedimentation of denser mafic magmas and the formation of narrow zones of intermediate composition at the contact of contrasting rocks.

AGE AND STRATIGRAPHIC POSITION OF THE SUPRACRUSTAL COMPLEX (THE KASKAMA BLOCK, INARI TERRANE, NORTH-EAST KOLA-NORWEGIAN REGION OF THE FENNOSCANDIAN SHIELD)

New data of U-Th-Pb age (SIMS) of magmatic (T = 730–744°C) zircon from intermediate and acid metavolcanics (1923–1926 Ma) of the supracrustal complex in the Kaskama block of the Inari terrane (north-west of the Kola-Norwegian region of the Fennoscandian shield) were obtained, which makes it possible to attribute them to the Kalevian suprahorizon. The source of primary melts of metariodacites and metabasaltes in the Kaskama block was the paleoproterozoic continental lithosphere not younger than 2390–2384 Ma. It is shown that the age of the tonalites of the Kuroaivi massif (1936 ± 7 Ma, εNd(T) = +0.1) as well as the granitoid massifs of the Southern Pechenga zone (1950–1940 Ma), are older, within the errors of U-Th-Pb age determinations, than the volcano-sedimentary rocks of the Kaskama unit and the Vepsian of the Southern Pechenga zone. This period of granite formation separates the early geodynamic stages of the continental rifting at the Yatulian-Ludikovian time from regimes, similar to the suprasubductional formation of the continental lithosphere, of the Inari terrane (1926–1850 Ma).

Происхождение и структурная позиция Камчатского срединного массива по данным глубинных геолого‑геофизических исследований

The article shows the results of deep research along the profile of the settlement of Nizhnyaya Oblukovina – the city of Andrianovka, crossing the northern part of the Kamchatka median massif. A geological and geophysical model of the structure of the earth’s crust and upper mantle has been constructed, where the structural position of the object under study is presented and an assumption is made about its origin. The model highlights a fragment of paleosubduction (slab), which was part of the most ancient convergent boundary in western Kamchatka. The final stage of subduction blocking and its displacement to the east at a distance of ~60 km in the Early Eocene is associated with the entry into the accretionary complex of a terrane in the form of an island-arc plate 6–9 km thick. At the site of the maximum inflection of the subsequent slab, an extension zone was formed – a rift zone, along which the rise of mantle material and high-temperature fluid occurred. Approximately 52 million years ago, the processes of metamorphism, focal melting and intrusion of granites into the upper layers of the crust took place. As a result, in the eastern part of the plate and its flanks, a granitoid massif was formed with a rock density of 2.58 g/cm3, which is significantly lower than the environmental density. Density deficiency led to a violation of isostatic equilibrium and, as a result, to a rise in this part of the structure. The most intense uplift occurred at the end of the Oligocene, as a result of which a ledge was formed, which the authors recommend giving the name: “Middle Kamchatka ledge” instead of the rooted “Kamchatsky median massif”. The genetic relationship of the Shanuch ore region with the features of the deep structure of the lithosphere has been revealed. The results of the research indicate a hidden (buried) distribution of the island-arc plate beyond the boundaries of the mapped outcrops of metamorphids. Intrusions of the main composition, promising for the opening of sulfide copper-nickel ores, are located in the marginal parts of the ledge.

Neoproterozoic Collision Granitoids in the Southwestern Margin of the Siberian Craton: Chemical Composition, U−Pb Age, and Formation Conditions of the Gusyanka Massif

The paper provides evidence that collisional magmatism related to the Neoproterozoic (880−860 Ma) orogenic event occurred in the southwest of the Siberian Craton. Newly obtained data are presented on the major-component and trace-element composition, U−Pb (SHRIMP II) zircon age, and Sm−Nd isotope composition for rocks of the Gusyanka granitoid massif in the Yenisei fault zone of the Yenisei Ridge. The concordant U−Pb zircon age of the Gusyanka massif is 871 ± 11 Ma indicates that its rocks were formed in the mid-Early Neoproterozoic, simultaneously with the rocks of the Kalama and Eruda massifs in the Tatarka−Ishimba fault system, during the same stage of the collisional events at approximately 880–860 Ma. The calc-alkaline granites, granodiorites, and leucogranites of the Gusyanka massif are classified, on the basis of their high alumina content and trace element composition, as S-type and were derived from a metapelitic source. Many trace-element parameters of rocks of the Kalama and Eruda massifs correspond to those of low-potassium I-type granites, which were most likely derived from mafic rocks and tonalites. The granitoids of the Gusyanka massif, on the one hand, and the Kalama and Middle Tyrada massifs, on the other, differ contrastingly in Nd isotope composition. The source of the former was either metapelites of the Tungusik Group or metasedimentary rocks of the Sukhoi Pit Group, with the involvement of juvenile material. The melts of granites of the Kalama and Middle Tyrada massifs might have been derived from a source with the involvement of an older, possibly Paleoproterozoic, crustal material and a juvenile mafic source. Thus, the orogenic events at 880−860 Ma led to the generation of melts at different levels of the Paleo- to Mesoproterozoic crust of the trans-Angara region of the Yenisei Ridge. The geodynamic history of the region is correlated with the synchronous successions and similar style of tectono-thermal events along the peripheries of the large Precambrian cratons of Laurentia and Baltica, and this is consistent with paleocontinental reconstructions of the close spatiotemporal relations between these cratons, Siberia, and their incorporation into Rodinia.

Age and Tectonic Setting of the Kopri-Type Granitoids at the Junction Zone of the Dzhugdzhur–Stanovoi and Western Stanovoi Superterranes of the Central Asian Fold Belt

Geochemical, geochronological (U–Pb on zircons, ID TIMS), and isotope–geochemical (Sm–Nd) studies of Kopri-type granitoids of the Tukuringra Complex have been carried out. The granitoids are located exclusively in the zone of the Dzheltulak suture, which separates the Dzhugdzhur–Stanovoi and Western Stanovoi superterranes of the Central Asian fold belt. It has been established that they can be classified as postcollisional adakite-like granitoids of elevated alkalinity and adakite-type basicity, formed in the age range between 127 ± 1 and 126 ± 1 Ma, which are part of the Late Mesozoic postcollisional Stanovoi volcano-plutonic belt that extends more than 1000 km in the sublatitudinal direction from the Sea of Okhotsk into the continent subparallel to the Mongolia–Okhotsk suture zone and stitches the Dzhugdzhur–Stanovoi and the Western Stanovoi superterranes. The structural position of the Kopri-type granitoid massifs registers the upper age limit of the Dzheltulak suture. Formation of the parent melts of these granitoids is associated with an essentially lithospheric source formed as a result of mixing of the Early Precambrian and a younger, apparently Phanerozoic component. In contrast to other granitoids of the Stanovoi belt that are close in composition and age, the granitoids under consideration are characterized by a certain increase in the role of the asthenospheric component in their source, which is probably due to their localization in the zone of elevated lithospheric permeability and at the junction of faults of different orientations, generally sublatitudinal, guided by the Mongolia–Okhotsk lineament, and northwestward, associated with the development of the Dzheltulak suture.

AGE AND TECTONIC SETTING OF THE KOPRI-TYPE GRANITOIDS OF THE JUNCTION ZONE OF THE DZHUGDZHUR-STANOVOY AND WEST-STANOVOY SUPERTERRANES OF THE CENTRAL ASIAN FOLD BELT

Geochemical, geochronological (U-Pb on ID TIMS zircons), and isotope-geochemical (Sm-Nd) studies of the Kopri-type granitoids of the Tukuringra Complex have been done. The granitoids localized exclusively in the zone of the Dzheltulak suture, which separates the Dzhugdzhur-Stanovoy and West Stanovoy superterranes of the Central Asian fold belt. It has been established that they can be classified as postcollision granitoids of elevated alkalinity and basicity of the adakite type, formed in the age range of 127 ± 1–126 ± 1 Ma, which are part of the Late Mesozoic postcollision Stanovoy volcano-plutonic belt extending in the sublatitudinal direction from the Sea of Okhotsk inland continent subparallel to the Mongolo-Okhotsk suture zone for more than 1000 km and stitching the Dzhugdzhur-Stanovoy and West- Stanovoy superterranes. The structural position of massifs of the Kopri-type granitoids fixes the upper age boundary of the formation of the Dzheltulak suture. The formation of the initial magmas of these granitoids is connected with an essentially lithospheric source formed as a result of mixing of the Early Precambrian and younger, apparently, Phanerozoic component. The similarity in the Nd isotopic composition of the granitoids of the Kopri-type with similar in composition and age granitoids of the West Stanovoy superterrane most likely indicates the similarity of their sources, as well as the fact that the Dzheltulak suture zone “plunges” in the northeast direction under the structures of the Dzhugdzhur–Stanovoy superterrane. This is in full accordance with modern ideas about the features of the deep structure of the junction of the Eurasian and Amur lithospheric plates.

MINERALOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE HURIVKA COMPLEX P-U-TR ORE OCCURRENCE, INHUL MEGABLOCK, UKRAINIAN SHIELD

The article presents the results of the study of the Hurivka apatite-uranium-rare earth ore occurrence, which is confined to the contact of the southern part of the Hurivka granitoid massif with metasedimentary rocks of the Inhul-Inhulets series. Argillizites, which host the productive mineralization, are represented by two zones: the lower montmorillonite-chlorite zone and the upper kaolinite-chlorite zone with hydromica. The concentrator minerals of rare earths (∑TR=0.05-0.5 %) in the bedrock are xenotime and monazite, while only xenotime was detected in argillizites. At the same time, minor impurities of yttrium and lanthanides were detected in apatite, chlorite and clay minerals. Xenotime and monazite also contain insignificant concentrations of uranium. The maximum uranium content in xenotime is 4.94% UO2, and in argillizites it can reach 0.86%. No native uranium minerals were detected in the studied ore. It is assumed that the most common form of its occurrence in argillizites is adhesion to the surface of clay and mica minerals due to sorption and adsorption processes. Anomalous high phosphorus content within the ore occurrence is associated with apatite mineralization. In bedrock, apatite is confined to skarns. In argillizites, its concentration in some intervals reaches 5%. The complex apatite-uranium-rare earth mineralization of the Hurivka ore deposit was formed in the course of complex long-term processes, which was expressed in the hydrothermal-metasomatic transformation of high carbonated rocks in contact with the granitoid massif and their subsequent argillization by low-temperature hydrotherms of endogenous and exogenous origin.

A first attempt at a provenance study in the Jadar block (Serbia) by means of U-Pb zircon geochronology

U-Pb geochronology of zircon grains retrieved from magmatic rocks intruding the Jadar block terrane in the central Balkans is used here to add new constraints on the terrane accretion processes and the provenance of crustal sources of this potentially exotic crustal block. Using an unorthodox approach, we analyzed zircons extracted from the products of Cenozoic (Cer and Boranja granitoid massifs) and Triassic magmatism (Bobija andesitic tuff - Pietra Verde). In fourteen samples of granites and epiclastites, we analyzed about 600 grains, and of these, about 30-40% were derived from the basement and were used further for the geological interpretation. Most samples show a similar Precambrian and Paleozoic age spectrum, including ubiquitous Neoproterozoic and well-defined Silurian-Ordovician populations. Only a few older zircons are present, composing minor populations at c. 1.2 Ga and 3.2 Ga. The younger zircons represent a ubiquitous Triassic population that is the strongest in all samples. This age population is most likely associated with local Permo-Triassic magmatism generated due to the opening of the Neotethys. In contrast to the magmatic rocks of Boranja and Bobija, the zircon age spectrum of the Cer polyphase pluton shows a strong Carboniferous peak, indicating a potentially important link to the Variscan margin of Eurasia. This supports opposing interpretations that either this part of the Jadar block terrane represents a southern continuation of the ?Bukkium? and Sana-Una terranes comprising displaced fragments of the southern European Variscan foreland, or, more likely, that it has an Adria affinity and that these zircons are derived from Cretaceous sediments of the Sava Zone, i.e., the suture that separates European and Adriatic domains, which were assimilated during the intrusion of the Cer granitic magmas.

Assessment of oil-and-gas-bearing capacity of pre-jurassic and jurassic deposits of the central part of the West Siberian plate

There were examined the issues of studying the features of the lithological and petrographic composition and the formation of oil deposits within the fields of the Surgut dome fold and the Frolov megadepression. It was noted that the formation of deposits of the sedimentary cover is associated with the peculiarities of the geological structure and the oil-bearing capacity of the basement rocks. In the considered territory, a high level of oil-bearing sedimentary cover is observed within the central part of the Surgut dome fold, and the deposits of the Pre-Jurassic part of the section can be additional sources of intensification of hydrocarbons in the Lower-Middle Jurassic deposits. The presence of zones of deep snaps is a search criterion for the detection of secondary reservoirs in them both — in destruction zones, basement, and in the Lower-Middle Jurassic deposits, therefore, deposits can be formed due to the vertically ascending migration of deep fluids through faults that cross the basement and horizons of the sedimentary cover.There were examined the issues of the prospects for the oil and gas content of the Lower-Middle Jurassic deposits, which must be associated with both granitoid massifs and the details of identifying the conditions of sedimentation and the establishment of contact zones of the sedimentary cover with the underlying formations.

Sorption of Np, Pu, Am, Sr, Cs on the Mineral Phases of the Rocks of the Nizhnekansky Granitoid Massif under Conditions of Underground Repositories for Radioactive Wastes

Sorption of Np, Pu, Am, Sr, Cs on the Mineral Phases of the Rocks of the Nizhnekansky Granitoid Massif under Conditions of Underground Repositories for Radioactive Wastes

Multistage Neoarchean magma genesis in the Bundelkhand Craton, India: Evidence from whole-rock elemental and Nd isotopic study of mafic magmatic enclaves and granitoids

Using field, petrography and geochemistry (elemental and Nd isotopic compositions), an integrated study has been carried out on the Neoarchean lithologies comprising mafic magmatic enclaves (MMEs) and undeformed granitoids of the Bundelkhand Craton (Central India) to understand their genesis and crustal evolution. Based on the degree of mingling/mixing with the host granitoids, the MMEs are classified into three types as E-1, E-2 and E-3 types. The E-1 type MMEs represent the early fragments formed by fractional crystallization of mafic/ultramafic magma. The E-2 type MMEs formed due to restricted mingling and rapid crystallization of a hot mafic magma that interacted with felsic granitoid magma. The E-3 type MMEs show compositional similarity with its felsic host and are proposed to have formed by magma mixing process. The MMEs underwent varying degrees of isotopic equilibration with the host granitoids. The E-1 and E-2 type MMEs were resulted from depleted mantle-wedge and the E-3 type MMEs formed from a metasomatized mantle-wedge during subduction. Underplating of basaltic magma probably played a key role in the crustal formation and also provided heat for large scale melting of the crustal rocks giving rise to granitic magma. Such tectono-magmatic events also produced mafic magmas that variably interacted with the granitic magma and played a significant role in the generation of huge Bundelkhand granitoid massif during the Neoarchean.