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Russian Geology and Geophysics

2022 year, number 4

1.
CURRENT ISSUES OF TECTONICS, PALEOGEOGRAPHY, GEODYNAMIC EVOLUTION, AND MINERAL RESOURCES OF THE CONTINENTAL MARGINS OF THE RUSSIAN ARCTIC

V.A. Vernikovsky1,2, V.S. Shatsky2,3
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Tectonics, geodynamics, subduction, collision, plumes, paleogeography, stratigraphy, magmatic and metamorphic petrology, diamonds, metallogeny, Arctic

Abstract >>
The special issue is focused on the problems of tectonics, paleogeography, geodynamic evolution, and mineral resources of the continental margins of the Russian Arctic. This topic is relevant, since the knowledge of the geologic structure of the Arctic Ocean and its formation and evolution can solve many global problems of geology and important regional problems, including the formation of oil- and gas-bearing sedimentary basins as well as prospecting for and development of diamonds and deposits of nonferrous, noble, rare-earth, and other minerals. In previous issues of Russian Geology and Geophysics, considerable attention was paid to the geology and oil and gas potential of the Arctic. In this special issue, emphasis is placed on the tectonics, stratigraphy, paleogeography, and petrology of the Arctic continental margins of Russia, the development of tectonic and geodynamic models for key structures, and diamond content and metallogeny of Arctic zones of the Siberian Platform, Chukotka, and the Kola Peninsula.



2.
LATE MESOZOIC-CENOZOIC TECTONICS AND GEODYNAMICS OF THE EAST ARCTIC REGION

S.D. Sokolov1, L.I. Lobkovsky2,3, V.A. Vernikovsky4,5, M.I. Tuchkova1, N.O. Sorokhtin2, M.V. Kononov2
1Geological Institute of the Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia
2Shirshov Institute of Oceanology of the Russian Academy of Sciences, Nakhimovsky pr. 36, Moscow, 117218, Russia
3Moscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudny, 141701, Russia
4Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
5Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
Keywords: Tectonics, geodynamics, terranes, Mesozoic era, East Arctic, Amerasian basin, Chukotka, North Alaska

Abstract >>
Tectonic and geodynamic models of the formation of the Amerasian Basin are discussed. The Arctic margins of the Chukchi region and Northern Alaska have much in common in their Late Jurassic-Early Cretaceous tectonic evolution: (1) Both have a Neoproterozoic basement and a complexly deformed sedimentary cover, with the stage of Elsmere deformations recorded in their tectonic history; (2) the South Anyui and Angayucham ocean basins have a common geologic history from the beginning of formation in the late Paleozoic to the closure at the end of the Early Cretaceous, which allows us to consider them branches of the single Proto-Arctic Ocean, the northern margin of which was passive and the southern margin was active; (3) the dipping of the oceanic and, then, continental lithosphere took place in subduction zones southerly; (4) the collision of the passive and active margins of both basins occurred at the end of the Early Cretaceous and ended in Hauterivian-Barremian time; (5) the collision resulted in thrust-fold structures of northern vergence in the Chukchi fold belt and in the orogen of the Brooks Ridge. A subduction-convective geodynamic model of the formation of the Amerasian Basin is proposed, which is based on seismic-tomography data on the existence of a circulation of matter in the upper mantle beneath the Arctic and East Asia in a horizontally elongated convective cell with a length of several thousand kilometers. This circulation involves the subducted Pacific lithosphere, the material of which moves along the bottom of the upper mantle from the subduction zone toward the continent, forming the lower branch of the cell, and the closing upper branch of the cell forms a reverse flow of matter beneath the lithosphere toward the subduction zone, which is the driving force determining the surface kinematics of crustal blocks and the deformation of the lithosphere. The viscous dragging of the Amerasian lithosphere by the horizontal flow of the upper mantle matter toward the Pacific leads to the separation of the system of blocks of Alaska and the Chukchi region from the Canadian Arctic margin. The resulting scattered deformations can cause a different-scale thinning of the continental crust with the formation of a region of Central Arctic elevation and troughs or with a breakup of the continental crust with subsequent rifting and spreading in the Canadian Basin.



3.
PALEOMAGNETISM OF THE FRANZ JOSEF LAND ARCHIPELAGO: APPLICATION TO THE MESOZOIC TECTONICS OF THE BARENTS SEA CONTINENTAL MARGIN

D.V. Metelkin1,2, V.V. Abashev1,2, V.A. Vernikovsky1,2, N.E. Mikhaltsov1,2
1Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
2Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Paleomagnetism, Franz Josef Land archipelago, High Arctic Large Igneous Province, Iceland plume, strike-slip kinematics, Amerasia basin, Barents Sea continental margin, Arctic

Abstract >>
We report new paleomagnetic and geochronological data for rocks of the Franz Josef Land archipelago and generalize available information about the paleomagnetism of the Barents Sea continental margin as applied to the issues of the Mesozoic Arctic tectonics. Specifically, the obtained age estimates are indicative of a brief episode of mantle plume magmatism at the Barremian-Aptian boundary (Early Cretaceous). The paleomagnetic data show that intraplate magmatism formations in the High Arctic, including the Franz Josef Land traps, are nothing more than a trace of the Iceland plume on the migrating tectonic plates of the region. Thus, the Iceland plume was geographically stationary for at least the last 125 Myr. Our paleotectonic reconstructions suggest a direct connection of the intraplate strike-slip systems of the Eurasian continent with the configuration and subsequent evolution mode of Mesozoic marginal basins and spreading axes during the initial opening stage of the Arctic Ocean.



4.
TECTONOTHERMAL MODEL FOR THE LATE PALEOZOIC SYNCOLLISIONAL FORMATION STAGE OF THE KARA OROGEN (northern Taimyr, Central Arctic)

V.A. Vernikovsky1,2, O.P. Polyansky3, A.V. Babichev3, A.E. Vernikovskaya1,2, V.F. Proskurnin4, N.Yu. Matushkin1,2
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4A.P. Karpinsky Russian Geological Research Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
Keywords: Collision, anatexis, granite, U-Th-Pb geochronology, thermomechanical modelling, Arctic, Kara orogen, Taimyr, Kara microcontinent, Siberian craton, finite element method, heat sources

Abstract >>
We present a tectonothermal model for the late Paleozoic syncollisional formation stage of the Kara orogen in northern Taimyr in the Central Arctic. The model is based on new and published structural, petrological, geochemical, and geochronological data, as well as thermophysical properties obtained for the Kara orogen. The latter hosts a significant volume of granites formed as a result of the collision between the Kara microcontinent and the Siberian craton. Based on geological, geochemical, and U-Th-Pb isotope data, the granites were differentiated into syncollisional and postcollisional intrusions that were emplaced in the intervals 315-282 Ma and 264-248 Ma, respectively. The presented tectonothermal model covers only the syncollisional formation stage of the Kara orogen, during which anatectic granites formed. The 2D models help to reconstruct the main tectonothermal processes of the syncollisional stage of formation of this structure, taking into account the local peculiarities of the thermal state of the Earth’s crust in the region. The model shows the mechanisms of increase in the lower crust temperature necessary for the formation of syncollisional anatectic granites. The estimates obtained from the model constrain the time interval between the collision/tectonic stacking and the granite formation. The modeling also showed the general regularities typical of orogens at syncollisional stages.



5.
THE TRIASSIC OF NEW SIBERIAN ISLANDS ARCHIPELAGO AND ITS POSITION IN THE STRUCTURE OF THE SEDIMENTARY COVER OF THE LAPTEV SEA SHELF

B.L. Nikitenko1,2, V.P. Devyatov3, A.G. Konstantinov1, E.S. Sobolev1, A.V. Yadrenkin1, E.B. Pestchevitskaya1, N.K. Lebedeva1,2, A.A. Goryacheva1,2
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
3Siberian Research Institute of Geology, Geophysics and Mineral Resources, Krasny pr. 67, Novosibirsk, 630091, Russia
Keywords: Triassic, facies zonation, stratigraphy, Arctic, New Siberian Islands, Laptev Sea

Abstract >>
The geological study of the Mesozoic sections of the New Siberian Islands archipelago and Asian coastal sections of the Arctic Ocean plays a key role in tying the results of comprehensive studies with seismic data on the Laptev Sea shelf and the western part of the East Siberian Sea. Therefore, it is extremely important to improve the subdivision of the Triassic system of the New Siberian archipelago and to define the position of the system in the structure of the Laptev Sea shelf sedimentary basin. The results of our study were used to improve and refine the lithostratigraphic subdivision of the Triassic in the study area and to recognize a distinct interregional stratigraphic marker, i. e., the Czekanowski Formation (lower Olenekian). In terms of genetic, structural, and sedimentological features, the Triassic strata were grouped into two groups: the Reshetnikov Group (Induan-upper Ladinian) and the Svetlaya Group (Ladinian-Rhaetian), reflecting major stages of sedimentation. For the Triassic of the eastern Laptev Sea shelf and adjacent onshore areas, the facies zonation scheme has been developed and refined on a unified basis. Based on their structure, the Phanerozoic sections of the study area can be considered as a part of the intermediate structural stage of the Laptev Sea plate at the margins of the Siberian craton.



6.
HIGH-RESOLUTION TRIASSIC BIOSTRATIGRAPHY OF THE KOTELNY ISLAND (New Siberian Islands, Arctic Siberia)

A.G. Konstantinov1, E.S. Sobolev1, A.V. Yadrenkin1, B.L. Nikitenko1,2, E.B. Pestchevitskaya1, N.K. Lebedeva1,2, A.A. Goryacheva1,2, V.P. Devyatov3
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
3Siberian Research Institute of Geology, Geophysics and Mineral Resources, Krasny pr. 67, Novosibirsk, 630091, Russia
Keywords: Triassic, ammonoids, nautiloids, coleoids, bivalves, brachiopods, foraminifers, palynomorphs, zonal scales, Arctic, New Siberian Islands

Abstract >>
The study of Triassic paleontology and stratigraphy of various regions of northeastern Russia and adjacent Arctic shelf is essential not only for improving and refining zonal biostratigraphic schemes, interregional and global correlation of Triassic deposits, and resolving problems of stratigraphic boundaries but also for developing and substantiating a new generation of Triassic stratigraphic schemes, which could serve as the stratigraphic basis for different regional and detailed geological investigations of the Arctic. The results of the study were used to improve existing zonal scales based on various groups of fauna and palynomorphs, develop a more detailed biostratigraphic subdivision of the Triassic, and characterize individual horizons using both terrestrial and marine palynomorphs. The zonal scales are calibrated to each other and to the regional zonal scale of the Triassic of Siberia and northeastern Russia, which provides the subsequent correlation with the International Chronostratigraphic Chart of the Triassic System. The set of coeval zonal scales for the Triassic of Kotelny Island sections based on ammonoids, nautiloids, coleoids, bivalves, brachiopods, and foraminifers and the analysis of microphytoplankton and terrestrial palynomorph assemblages are a useful tool for detailed subdivision and correlation of the eastern part of the Laptev Sea shelf and adjacent regions of northeastern Russia.



7.
LITHOLOGICAL SIGNATURES OF EARLY CARBONIFEROUS EVENTS IN THE NORTHEASTERN SIBERIAN CRATON (Western Verkhoyansk region)

N.V. Sennikov1,2, R.A. Khabibulina1, O.T. Obut1,2, T.V. Gonta1
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
Keywords: Geological events, Carboniferous, Visean, lithology, redeposited fauna assemblage, tabulate corals, conodonts, ostracods, paleogeography, Western Verkhoyansk region

Abstract >>
The paper focuses on presumable sources of coarse carbonate material transported into the Visean Northern Kharaulakh basin. The sand to pebble components of the Krestyakh conglomerate unit originated by medium and distant transport by debris flows (turbidity currents) along submarine canyons from the place of their initial littoral deposition to relatively deep accommodation basins. The carbonate material was most likely derived from Ordovician, Silurian, and Devonian sediments, which are currently represented by their analogs in Kotelny Island. The sediments of the Northern Kharaulakh basin store a record of two geological events: (1) middle Visean collision of Siberia with the Laurussian supercontinent and rifting of some terranes off the Siberian сraton and (2) late Visean collision of the Kara terrane with the northern margin of Siberia.



8.
EPITHERMAL Au-Ag-Se-Te DEPOSITS OF THE CHUKCHI PENINSULA (Arctic zone of Russia): METALLOGENY, MINERAL ASSEMBLAGES, AND FLUID REGIME

N.S. Bortnikov1, A.V. Volkov1, N.E. Savva2, V.Yu. Prokofiev1, E.E. Kolova2, A.A. Dolomanova-Topol'1, A.L. Galyamov1, K.Yu. Murashov1
1Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 119017, Russia
2N.A. Shilo Northeastern Interdisciplinary Research Institute, Far Eastern Branch of the Russian Academy of Sciences, ul. Portovaya 16, Magadan, 685010, Russia
Keywords: Arctic zone, epithermal Au-Ag deposits, mineralogical features, selenides, tellurides, fluid inclusions, thermobarogeochemistry, ore formation, Chukchi Peninsula

Abstract >>
Numerous epithermal Au-Ag deposits and ore occurrences of the Chukchi Peninsula are localized in the Cretaceous Okhotsk-Chukotka (OCVB) continent-marginal and Late Jurassic-Early Cretaceous Oloi (OVB) island arc volcanic belts and in Early Cretaceous postcollisional volcanic troughs. Volcanotectonic depressions, calderas, and volcanic domes control the location of the deposits. The orebodies of the deposits are quartz-adularia veins, sometimes en-echelon ones forming extending vein zones, as well as isometric and linear stockworks. The auriferous veins of most deposits display complex breccia-crustification structures. The vein ores have rhythmically and colloform-banded structures, with a predominantly fine distribution of ore mineral grains, often with banded clusters of ore minerals (ginguro). Native gold is of low fineness; the dispersion of this index varies from low to high. Acanthite is widespread in the ores. Its highest contents are specific to deposits with the repeated redistribution of substance (Kupol, Corrida, and Valunistoe). Based on the results of mineralogical studies, most of the epithermal Au-Ag deposits of the Chukchi Peninsula can be assigned to the Se type. The ores of some deposits (Valunistoe, Dvoinoe, etc.) contain both Se and Te minerals. The telluride-richest sites of the Sentyabr’skoe and Televeem deposits are far from the main orebodies. Most of the Chukchi epithermal Au-Ag deposits have many common characteristics (low and moderate temperatures of fluids, low fluid salinity, domination of carbon dioxide over methane, etc.) typical of low-sulfidation deposits. The maximum temperatures and salinity are specific to fluids in the Central Chukchi sector of the OCVB and in the Baimka zone of the OVB, and the minimum ones are typical of fluids in the East Chukchi flank zone and inner zone of the OCVB. The average salinity of mineral-forming fluids in the inner zone of the OCVB is half as high as the salinity of fluids in the East Chukchi flank zone of this belt, although the sulfate content is higher. At the same time, the fluids in the inner zone of the OCVB are richer in carbon dioxide and bicarbonate ion than the fluids in the East Chukchi flank zone of this belt. The fluid inclusion data permit the Vesennee deposit (Baimka zone) to be regarded as an intermediate-sulfidation one and suggest the presence of epithermal high-sulfidation deposits in the inner zone of the OCVB.



9.
TRIASSIC DIAMONDIFEROUS TUFFACEOUS-SEDIMENTARY ROCKS IN THE ARCTIC ZONE OF SIBERIA

S.A. Grakhanov1,2, V.F. Proskurnin1, O.V. Petrov1, N.V. Sobolev3,4
1A.P. Karpinsky All-Russian Research Geological Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
2AO ALMAR-ALMAZY ARKTIKI, ul. Chernyshevskogo 8/2, office 207.1, Yakutsk, Sakha Republic, 677000, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
Keywords: Diamond, deposit, placer, Triassic, Arctic zone of Siberia

Abstract >>
In the Arctic zone of Siberia, large diamond occurrences have been discovered in volcaniclastic, sedimentary-volcaniclastic, volcanosedimentary, and sedimentary rocks of the upper Ladinian strata and the base of the Carnian (Triassic) strata. They are confined to the Primorye mineragenic zone, which is traced along the Laptev Sea water area from the western Verkhoyansk area to eastern Taimyr. We have first identified a specific range of diamonds in these deposits. Among the rounded crystals of varieties I, II, V, and VII, there are grains with a light carbon isotope composition and high nitrogen contents. They have no analogues in typomorphic features in the known primary deposits of Yakutia but are completely similar to diamonds in the Rhaetian, Early Jurassic, Late Jurassic, Early Cretaceous, Neogene, and Quaternary commercial placers and placer occurrences, which suggests their formation as a result of the erosion of Triassic sources.



10.
GEODYNAMIC FORMATION CONDITIONS AND AGE OF GRANITOIDS FROM SMALL INTRUSIONS IN THE WEST OF THE YANA-KOLYMA GOLD BELT (northeast Asia)

V.Yu. Fridovsky1, A.E. Vernikovskaya2,3,4, K.Yu. Yakovleva1, N.V. Rodionov5, A.V. Travin6, N.Yu. Matushkin7,4, P.I. Kadilnikov7,4
1Diamond and Precious Metal Geology Institute, Siberian Branch of the Russian Academy of Sciences, pr. Lenina 39, Yakutsk, 677980, Russia
2Diamond and Precious Metal Geology Institute, Siberian Branch of the Russian Academy of Sciences, ul. Pirogova 1, Novosibirsk, 630090, Russia
3Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences
4Novosibirsk State University
5A.P. Karpinsky Russian Geological Research Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
6V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
7Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, ul. Pirogova 1, Novosibirsk, 630090, Russia
Keywords: Granitoids, U-Pb, Ar/Ar, Sm-Nd and Rb-Sr isotope data, active continental margin, Yana-Kolyma gold belt, northeast Asia

Abstract >>
We report results of geological, mineralogical-petrographic, geochemical, isotope-geochemical (Sm-Nd, Rb-Sr), and geochronological (U-Pb, 40Ar/39Ar) studies of acid and intermediate intrusive rocks (granodiorites, leucocratic granites, subalkaline granites, and subalkaline leucocratic granites, diorites, and quartz diorites) of the Bukeschen and Samyr small plutons in the western part of the Yana-Kolyma gold belt (northeast Asia). These rocks are combined with Late Jurassic (151-145 Ma) dikes of basic, intermediate, and acid compositions into a single complex of small intrusions. They intrude the Upper Triassic-Middle Jurassic terrigenous deposits of continental margin blocks in the eastern part of the Verkhoyansk-Kolyma folded area. Our new U-Pb data for zircon (SHRIMP-II) indicate that the Bukeschen and Samyr pluton granitoids formed in the Berriasian and at 144.5 and 143 Ma, respectively. The small-intrusion granitoids have geochemical and isotope (Sm-Nd and Rb-Sr) characteristics similar to those of Late Jurassic dikes of varying composition. Therefore, they can be united into a single complex of small intrusions generated from a mixed source with the participation of mantle (OIB- and E-MORB type), lower crust, and subduction components and with Paleoproterozoic-Mesoproterozoic Sm-Nd model age estimates for the magma sources. Late Jurassic-Early Cretaceous magmatic and postmagmatic events and cooling of the intrusions played an important role in the processes of gold localization in the western part of the Yana-Kolyma gold belt. This is reflected in two tectonothermal stages (accounting for closing temperatures of the U-Pb, 40Ar/39Ar, and Re-Os isotope systems for different minerals) estimated at 151-141 and 138-137 Ma. These results for the small-intrusion complex agree with the tectonic model of the evolution of an active continental margin (northeastern Siberia) in the Mesozoic era, whose final development stage in the Berriasian age saw the formation of mostly small granitoid plutons.



11.
METAMORPHISM OF THE KORVATUNDRA STRUCTURE OF THE LAPLAND-KOLA OROGEN (Arctic Zone of the Fennoscandian Shield)

E.A. Nitkina1, O.A. Belyaev1, D.V. Dolivo-Dobrovol'skii2, N.E. Kozlov1, T.V. Kaulina1, N.E. Kozlova1
1Geological Institute of the Kola Science Center, Russian Academy of Sciences, ul. Fersmana 14, Apatity, 184209, Russia
2Institute of Precambrian Geology and Geochronology, nab. Makarova 2, St. Petersburg, 199034, Russia
Keywords: Metamorphism, deformations, P-T conditions, U-Pb, Sm-Nd, Rb-Sr, Korvatundra structure, Arctic zone of the Fennoscandian Shield

Abstract >>
We study the P - T conditions and age of metamorphic evolution of the rocks that make up the Korvatundra structure in the northeast of the Fennoscandian Shield. The rocks underwent progressive metamorphism of the amphibolite facies at 625-660 ºC and 8.7-8.8 kbar 1945 ± 34 Ma (Sm-Nd data). The pegmatite cutting the metamorphic paragenesis that formed at this stage has an age of 1917 ± 6 Ma (zircon U-Pb data). Metamorphic transformations after 1917 Ma are manifested locally as discrete zones of blastomylonites in the rocks of the northern part and some inner sites of the Korvatundra structure. Both local increases and decreases in temperature and pressure are possible in these zones. The formation of light titanite with an age of 1863 ± 44 Ma marks the next stage of shear strain. Low-temperature alterations (chloritization and silicification) took place in the zones of final deformations 1722 ± 5 Ma (Rb-Sr data). Beginning from 1.94 Ga, the general deformational and metamorphic history of the Korvatundra structure, Lapland Granulite Belt, and Tana Belt confirms the assumption of the formation of a single inverted metamorphic zoning within the Korvatundra structure and the overlying Lapland-Kolvitsa Collision Belt in the Paleoproterozoic. The obtained data supplement the idea of the Paleoproterozoic geodynamic evolution of the Lapland-Kola orogen.



12.
SULFIDE PGE-Cu-Ni AND LOW-SULFIDE Pt-Pd ORES OF THE MONCHEGORSK ORE DISTRICT (Arctic western sector): GEOLOGY, MINERALOGY, GEOCHEMISTRY, AND GENESIS

V.V. Chashchin1, V.N. Ivanchenko2
1Geological Institute of the Kola Science Center, Russian Academy of Sciences, ul. Fersmana 14, Apatity, 184209, Russia
2AO Rosgeologiya, ul. Odoevskogo 24, St. Petersburg, 199155, Russia
Keywords: Sulfide PGE-Cu-Ni and low-sulfide Pt-Pd ores, basal and reef types of deposits and manifestations, PGE geochemistry, platinum group minerals, Monchepluton, Monchetundra massif, Monchegorsk ore district

Abstract >>
During the recent exploration of the Monchegorsk ore district (MOD) in the Arctic western sector, the platinum potential of known Cu-Ni deposits (Nittis-Kumuzhya-Travyanaya (NKT), Nyud, Ore Horizon 330 (OH330), and Terrasa) has been assessed, and new sulfide PGE-Cu-Ni deposits (Western Nittis) and manifestations (Moroshkovoe Ozero, Poaz, and Arvarench), and low-sulfide Pt-Pd deposits (Loipishnyun, Southern Sopcha, and Vuruchuaivench) have been discovered. All of them are confined to Paleoproterozoic (ca. 2.5 Ga) layered intrusions (the Monchegorsk pluton (Monchepluton) and the Monchetundra massif) and are divided into two types according to their structural position: basal, located in the marginal parts of intrusions, and reef-type (stratiform). All types of ores show Pd specialization. Platinum group minerals (PGM) have a limited composition in sulfide PGE-Cu-Ni ores and are represented by predominant Pt and Pd compounds with Bi and Te and subordinate PGE arsenides and sulfides. Low-sulfide Pt-Pd ores are characterized by a significant variety of PGM, with a predominance of PGE sulfides, bismuthotellurides, and arsenides. Sulfide PGE-Cu-Ni deposits and manifestations (Western Nittis, NKT, Nyud, Moroshkovoe Ozero, Poaz, and Arvarench) formed through the accumulation of base metal sulfides and PGE in immiscible sulfides and their subsequent segregation in commercial contents. The reef-type OH330 deposit and Terrasa manifestation resulted from the injection of additional portions of sulfur-saturated magma. The basal-type low-sulfide Pt-Pd deposits (Loipishnyun and Southern Sopcha) formed from residual melts enriched in ore components and fluids separated and crystallized during long-term ore-forming processes. The reef-type Vuruchuaivench deposit is the result of deep fractionation of the parental magma with the formation of a sulfide liquid enriched in Cu and PGE. Significant reserves and large predicted resources of sulfide PGE-Cu-Ni and low-sulfide Pt-Pd ores are a reliable mineral resource base for the development of the mining industry in the Kola region of the Arctic western sector.