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 study of Re–Os isotopic systematics of the Mesozoic magmas in East Antarctica and its comparison with Sr–Nd–Pb–Os published data allowed us to reveal the main features of Antarctic magmatism associated with the activity of the Karoo–Maud (Dronning Maud Land (DML), Karoo and Ferrar provinces) and the Kerguelen (Lambert rift area) plumes. It is shown that a melt source of the 180-Ma Karoo–Maud plume could be enriched lithospheric mantle. Variations of the 187 Os/ 188 Os ratio in the range of 0.1242–0.1426 characterize almost all types of melts in the Karoo and DML provinces, including both high- and low-Ti magmas as well as high-Mg ferropicrites produced by melting of mantle pyroxenite. This observation is consistent with previous assumption that magmas derived from pyroxenite mantle at the initial stage of plume impact represented melts of deep lithospheric fragments of ancient Gondwana paleocontinent that were entrapped by plume. Thereby, mantle heterogeneity recorded in the Nd–Pb–Sr isotopic compositions of the basalts is not expressed in the systematic variations of Re–Os isotope system. The magmatic source of the basalts of the Ferrar province differs from the source of Mesozoic magmatism in the Karoo and DML provinces by great variations in the 187 Os/ 188 Os ratio: from 0.1 to 0.31, and by the lower osmium contents, with limited variations of other isotopic systems, indicating an admixture of enriched EM-II source. This is consistent with inferred subduction reworking of the mantle of the western Antarctic margin (Sushchevskaya et al., 2022). Ultramafic picritic magmas from the Lambert Glacier area are characterized by a radiogenic osmium isotopic composition: 187 Os/ 188 Os 0.1582–0.2388. Source of these magmas could be ancient depleted mantle, which later experienced mantle metasomatism due to the multiple interactions with fluid-saturated melts. Picritic melts of the paleorift zone of the Lambert Glacier are close to a magma source of the Karoo and DML provinces in terms of Sr-Nd isotopic composition, but differ in more radiogenic lead.

present the first results of a comprehensive isotope-geochemical study of dolomitic carbonatites of the Mal'dzhangarka massif located in the southeast of the Billyakh melange zone (southeastern periphery of the Anabar Shield). Zircon grains separated from core samples from a depth of 6-30 m have a three-phase structure. All of them were trapped from the host metamorphic rocks and mark the age of the main stage of high-gradient metamorphism in the region, 2027 +/- 9 Ma. Pyrochlore containing 38-705 ppm U and 5-21 ppm radiogenic Pb, with weak metamictization of the crystal lattice and an undisturbed U-Pb system, made it possible to estimate the concordant age of rare-metal mineralization in the massif, 167 +/- 4 Ma, which is probably close to the crystallization age of the host carbonatites. The estimated age corresponds to one of the stages of kimberlite-carbonatite magmatism on the eastern slope of the Anabar dome. The Re-Os isotope system of pyrite from superposed late carbonate-sulfide veinlets in the carbonatites testifies to a close (within the error of determination) age, 179 +/- 14 Ma, and a low initial Os isotope ratio, which indicates the contribution of mantle material to the formation of this isotope system.

Xenoliths of high-alumina pyroxenites in the Quaternary basalts of the Sigurd Volcano of West Spitsbergen are spinel and spinel-garnet clinopyroxenites, spinel-garnet websterites, and websterites. The granoblastic texture with relics of subhedral magmatic texture, the change of mineral assemblages, and the signs of partial melting in the xenoliths reflect their multistage formation. The goal of our study was to determine the sequence and thermodynamic conditions of the change of mineral assemblages and to establish their age by Re-Os, U-Pb, Sm-Nd, and Rb-Sr isotope dating. It has been established that the primary assemblage in the pyroxenites, which included high-alumina Opx, Cpx, and Spl, was transformed in several stages: (1) Spl -> Grt replacement with the formation of garnet-containing websterites and clinopyroxenites, (2) development of kelyphitic Opx-Spl rims over Grt grains, (3) formation of Amph, (4) exsolution with the formation of Cpx and Opx, and (5) partial melting. Comparison of the obtained results with published data shows that the primary assemblage is similar in Al2O3/MgO ratio to Opx + Cpx +/- Spl cumulates resulted from the crystallization of basaltic melts at 1.2 GPa and the degree of crystallization of similar to 15%, i.e., in the lower crust (at 2.0 GPa, Grt and Cpx crystallize from the solution). The equilibrium parameters of the Grt-Opx assemblage in the pyroxenites are 1060-1310 degrees C and 2.2-3.3 GPa; in the P-T diagram, their points are localized below the Spl -> Grt phase transition curve, in the system CaO-MgO-Al2O3-SiO2, thus corresponding to the model continental geotherm with a surface heat flow density of 60 mV/m(2) and somewhat higher. This indicates the Spl -> Grt replacement and the formation of garnet-containing pyroxenites in the shallow-depth upper mantle. The formation of kelyphitic Opx-Spl rims over the Grt grains indicates a subsequent temperature and pressure decrease to values above the Grt -> Spl phase transition curve. This is confirmed by the presence of exsolution structures in pyroxene, which formed when the temperature decreased by 100-150 degrees C. The Re and Os isotope composition in the bulk samples of Spl-Grt websterites that did not undergo partial melting corresponds to an age of 457.0 +/- 3.5 Ma, which reflects the time of transformation of the primary Cpx-Opx-Spl assemblage into a garnet-including one. A similar value (488.6 +/- 5.9 Ma) was obtained by U-Pb dating of zircon from Spl-Grt websterite, also without signs of melting. Zircon crystals from Spl-Grt clinopyroxenite with clear signs of partial melting have typomorphic features of autochthonous magmatic zircons. They form a single age cluster of 310.7 +/- 3.3 Ma, which marks the age of melt crystallization in the pyroxenites. Thus, Spl pyroxenites are, most likely, Opx + Cpx +/- Spl cumulates, products of crystallization of basaltic melts in the lower crust. The subsequent Spl -> Grt replacement and the formation of garnet-containing websterites and clinopyroxenites in the shallow-depth upper mantle can be regarded as an indicator of the delamination of the continental crust into the mantle, and the Re-Os isochron date of 457.0 +/- 3.5 Ma is the most likely upper age bound of the crust delamination into the mantle. The subsequent uplifting of the Spitsbergen lithosphere, which was expressed as the formation of kelyphitic Opx-Spl rims over garnet, exsolution in pyroxene, and partial melting, was not far in time from the delamination stage and lasted < 300 Ma.

The paper presents the results of the comprehensive isotope geochemical (Re-Os, Pb and δ34S) study of sulfide mineralization of the Morozkinskoye deposit. The ore zones of the deposit are localized in the syenite massif of Mount Rudnaya, which is located within the Central Aldan ore region (southern Yakutia). Gold mineralization is represented by vein-disseminated or vein type mineralization and is manifested in acidic low-temperature metasomatites – beresites (Qz-Ser-Ank-Py). For the first time we obtained an age estimate of the gold mineralization ~ 129 ± 3 Ma, which the synchronism of the hydrothermal ore process in the beresites, which formed the Morozkinskoye deposit, and magmatic crystallization of the syenites of Mount Rudnaya (~130 Ma). The osmium initial isotopic composition of the studied sulfides indicates a mixed mantle-crustal source of sulfide mineralization. New lead isotopic data of syenites indicate the predominance of mantle lead and an insignificant role of the lower – crust lead, while the isotopic composition of pyrite denotes the presence of the upper crustal material in the ore genesis. The sulfide δ34S values vary from –2.3 to +0.6 ‰ and indicate a predominantly magmatic source of sulfur in the ores.

The first results of the study of the Re–Os isotope system of native gold from the orogenic Malo-Tarynskoe, Khangalas, and Bazovskoe deposits located in the central part of the Yana–Kolyma metallogenic belt are reported. The concentration of Re in the studied gold samples varies from 0.168 to 6.997 ppb, while the concentration of Os ranges from 0.068 to 1.443 ppb. The obtained data allowed us to calculate the isochrone age, which is consistent with the 40Ar–39Ar and K–Ar ages of sericite from these deposits within the error. The results indicate that the studied gold deposits were formed in the range of 147.8–137.1 Ma, synchronously with the Late Jurassic–Early Cretaceous orogenic processes in the Yana–Kolyma metallogenic belt and on the eastern margin of the Siberian Continent. The initial Os isotope ratios in the studied samples and fractions of gold from the Malo-Tarynskoe, Khangalas, and Bazovskoe deposits, (187Os/188Os)i = 0.1844–0.2475, suggest a significant role of a nonradiogenic component normally associated with mantle sources.

This article reports new geochemical, Sr-Nd-Hf-Pb and Re-Os data on the rocks of the Middle Paleoproterozoic (1.99 Ga) Tiksheozero ultramafic-alkaline-carbonatite complex confined to the northeastern margin of the Karelian Craton. We focus on the poorly studied silicate rocks. Based on petrographic and geochemical research, the silicate rocks are subdivided into two groups: an ultramafic-mafic series depleted in REE, and other incompatible elements and an alkaline series enriched in these elements. Isotope studies showed that all rocks have juvenile isotope signatures and were likely derived from a primitive OIB-type mantle source with possible contributions of the subcontinental lithospheric mantle (SCLM). Insignificant crustal contamination is recorded by Pb and Os isotopic compositions. The incompatible element enrichment in the alkaline rocks and depletion in ultramafic-mafic rocks of the mildly alkaline series with allowance for insignificant crustal contamination confirm their derivation from different primary melts. However, a narrow range of Sr, Nd, Hf, and Pb isotope compositions and compact clusters in 207Pb/204Pb-206Pb/204Pb, Nd-87Sr/86Sr and Hf-Nd isotope diagrams indicate their origination from a common mantle source. A model of subsequent two-stage melting is being most consistent with the geochemical data for this complex.

В работе представлены результаты комплексного изотопно-геохимического (Re-Os, Pb и δ34S) исследования сульфидной минерализации Морозкинского месторождения. Рудные зоны месторождения локализованы в сиенитовом массиве горы Рудная, который расположен в пределах Центрально-Алданского рудного района (южная Якутия). Золоторудная минерализация представлена прожилково-вкрапленной, реже жильной минерализацией и проявлена в кислотных низкотемпературных метасоматитах – березитах (Qz-Ser-Ank-Py). Впервые получена оценка возраста золотого оруденения ~ 129 ± 3 млн лет, которая свидетельствует о синхронности гидротермального рудного процесса в березитах, сформировавшего месторождение Морозкинское, и магматической кристаллизации сиенитов горы Рудная (~130 млн лет назад). Начальный изотопный состав осмия изученных сульфидов указывает на смешанный, мантийно-коровый, источник вещества сульфидной минерализации. Новые данные по изотопному составу свинца сиенитов свидетельствуют о преобладании свинца мантийной природы и несущественной роли свинца нижней коры, тогда как изотопный состав свинца пирита указывает на присутствие вещества верхнекорового источника при генезисе рудного минерала. Значения δ34S сульфидов изменяются от –2,3 до +0,6 ‰ и указывают на преимущественно магматический источник серы в рудах.

The article presents the results of the sulfide mineralization dating of the Mayskoe gold ore deposit using the Re-Os isotope system and isochron age estimation method of the main sulfide minerals: arsenopyrite, pyrite, and antimonite. The complex multistage formation of the studied sulfides, as well as the close intergrowths of genetically different mineral phases, did not allow obtaining a single rhenium-osmium isochron corresponding to the formation time of sulfide mineralization. Isochrones for single minerals, collected from each sulfide sample, turned out to be the result of isotopically distinct components mixture (radiogenic crustal and non-radiogenic mantle) and do not make sense from the geochronological point of view. In terms of geology, the most significant result of the study is an age estimation of 128.8 ± 4.4 Ma, obtained for the sulfide mineralization of Mayskoe deposit using Re-Os isotope dating of single fractions of pyrite and antimonite of the ore mineralization stage. While arsenopyrite is most closely associated with gold mineralization, one of the arsenopyrite varieties corrodes framboidal pyrite of the pre-ore stage, has a maximum of the crust component in the osmium isotopic composition and forms a mixing line in the isochron diagram with an apparent formation age of 458 ± 18 Ma. The initial osmium isotopic composition of the studied sulfides indicates a mixed mantle-crust source of sulfide mineralization. The issue of simultaneous ore genesis and granitoid magmatism in the Mayskoe deposit remained unresolved (the age of granitoids according to the U-Pb zircon system is 108 Ma). However, a possible solution could be the further determination of the Re-Os isochron age of the ore mineralization sulphides from the single paragenesis of a specific sample containing both arsenopyrite and pyrite (+ antimonite) with gold.

В работе приводятся результаты датирования сульфидной минерализации Майского золоторудного месторождения с использованием Re-Os изотопной системы основных сульфидных минералов: арсенопирита, пирита и антимонита и изохронного метода оценки возраста. Сложное полистадийное образование изученных сульфидов, а также тесные взаимные срастания генетически различных минеральных фаз не позволили получить единую рений-осмиевую изохрону, соответствующую времени образования сульфидной минерализации. А мономинеральные изохроны по отдельным навескам каждого образца сульфидов оказались результатом смешения изотопно различных компонентов (радиогенного корового и нерадиогенного мантийного) и не имеют прямого геохронологического смысла. Геологически наиболее значимым результатом проведенного исследования следует рассматривать возрастную оценку 128,8±4,4 млн лет, полученную для сульфидной минерализации Майского месторождения с использованием рений-осмиевой систематики монофракций пирита и антимонита рудной стадии минерализации. Арсенопирит наиболее тесно ассоциирует с золотым оруденением, одна из разновидностей которого корродирует фромбоидальный пирит дорудной стадии, имеет максимальную долю корового компонента в изотопном составе осмия и образует линию смешения на изохронной диаграмме с кажущимся возрастом образования 458±18 млн лет. Начальный изотопный состав осмия изученных сульфидов указывает на смешанный, мантийно-коровый, источник вещества сульфидной минерализации. Вопрос о синхронности процессов рудогенеза и гранитоидного магматизма для района месторождения Майского остался неразрешенным (возраст гранитоидов по U-Pb системе циркона – 108 млн лет), тем не менее, возможным его решением стало бы дальнейшее определение изохронного Re-Os возраста по сульфидам рудного этапа из единого парагенезиса конкретного образца, содержащего как арсенопирит, так и пирит (+ антимонит) с золотом.

The discussed below results on Pb isotopic compositions have been obtained by both TIMS and LA-ICP-MS-MC techniques on sulphide and plagioclase mg-weight specimens and single grains correspondingly. General Pb isotopic compositions imply derivation from both, the mantle and crustal sources with the latter being dominant. The obtained results from the Talnakh intrusion notably discrepant from that of the Norilsk and Kharaelakh being less radiogenic, while the latter two cluster together, demonstrating a minor divergence between massive and disseminated ores. Analysis of Pb-207/Pb-204 versus delta S-34 along with Th/U assumes three sources of mantle, lower curst and upper crust, while Pb isotopes alone do not provide distinguishing of the massive ores from poor one. Disparity of Pb isotopes in sulphides and plagioclases assumes their chemical and isotopic disequilibrium, precluding their coexistence in a single batch of melt.

The chapter describes a technique of analysing copper and nickel isotopes in ores and magmatic rocks of deposits. Average delta Cu-65 value strongly diverges in rich intrusions: Kharaelakh (-1.55 parts per thousand), Talnakh (-0.7 parts per thousand), and Norilsk-1 (+0.25 parts per thousand). Perhaps this is due to the mixing of the crustal and mantle sources of matter in the formation of these massifs. The Kharaelakh intrusion by delta Cu-65 has a large share of crustal matter. In the remaining massifs, the average value of delta Cu-65 is almost the same (-0.8 to -0.3 parts per thousand) and does not correlate with the isotope composition of sulphur. The average values of nickel Ni-61/Ni-60 isotope composition vary within narrow limits from -0.6 to 0 parts per thousand in all intrusions of the region and point to a single source of this metal. Data on copper and nickel isotopes in the products of mining and metallurgical companies in the world are given. Variations in the isotopic composition of copper are more associated with raw materials sources of companies, and the isotope composition of nickel, with different technological processes. A possible change in the isotopic composition of nickel during carbonylation (a mond process) is considered.

The Maksovo metasapropelite deposit, which contains shungite matter and is called maksovite, is located in the eastern Onega structure. The deposit is a diapiric fold which formed ca. 2070±10 Ma ago. It is underlain by carbonate rocks and overlain by tuff siltstones and is cross-cut by 1956±5 Ma gabbro-dolerites. Unaltered maksovites are pelitomorphic rocks with a massive to mildly layered texture and moderate concentrations of all petrogenic components and Сorg of about 30%. Fe-Mg rich and alkaline metasomatic rocks evolve after maksovites and mafic and carbonate tuff siltstones in the northwestern part of the deposit within a multiple ridge-like fold after brecciation zones. They differ from unaltered sedimentary rocks in heterogeneous (brecciated, streaky) textures, mineral and chemical composition and are saturated with numerous sulphide, carbonate, quartz and albite veinlets. They are identified by intense biotitization, chloritization and the presence of calcite, microcline metacrystals, albite-carbonate metacrystals with apatite and carbonate-quartz metacrystals with sulphides and rutile, veinlets and disseminated mineralization. Na concentration rises to 5.67% and K concentration to 7.57%. P and Ti concentrations, accompanying alkaline metasomatism, as well as Mg-Fe and ore-bearing components (often incompatible), increase locally. Metasomatic rocks evolve heterogeneously and are represented by breccia zones. Their slightly elevated radioactivity disturbs the qualitative characteristics of primary maksovite as a useful mineral. Maksovites were dated at 1558±61 Ma by the Re-Os method from sulphides.

The chapter presents data on Rb-Sr and Sm-Nd TIMS analysis of pyroxenes, plagioclases, gross samples of igneous rocks and sulphide ores. In most Sm-Nd analyses of minerals, the isotope system (pyroxene-plagioclase) does not reflect the age of intrusions and shows a rejuvenated or aged isochronous age. Only for the Kharaelakh intrusion, one 241 +/- 32 Ma isochron was obtained, close to the U-Pb age of zircons. The primary isotope ratio Sr-87/Sr-88 and the eNd parameter of samples are calculated for the age of 250 Ma based on the average U-Pb age of zircons. The primary ratio of plagioclases strontium from magmatic rocks of intrusions (0.7032-0.7090) is lower than that of ore sulphides (0.7081-0.7116). The heterogeneity of Sr and Nd isotope composition of minerals and rocks within a single intrusion is caused by different degrees of impact of ore and host-rock contamination. In the gross samples of igneous rocks from the studied massifs, the primary ratio of strontium varies from 0.7049 to 0.7128, and epsilon(Nd) varies from -7.7 to +7.0. These data indicate a significant effect of the crustal component in the formation of igneous rocks during the injection of mantle material with the parameters Sr-87/Sr-88 = 0.7037 and epsilon(Nd) = +9.5. Based on Nd and Sr isotopic data, it is impossible to clearly distinguish groups of intrusions with different ore content.

The chapter presents new geochronologic results of various isotope techniques (U-Pb SIMS and Re-Os TIMS) along with their comparison with already published data. The main intrusions of the Norilsk district are demonstrated to be emplaced almost simultaneously with two possible magma intrusion pulses at 254 +/- 4 and 244 +/- 4 Ma (U-Pb SIMS), assuming c. 10 Ma duration of igneous activity. This is corroborated by sulfides Re-Os dating (245-250 Ma), suggestion synchroneity of intrusion and the ore formation. Some Permian and Carboniferous zircon xenocrysts have been found along with Precambrian grains (c. 1.9 and 2.7 Ga), while no Devonian xenocrysts has been revealed. A group of 145-150 Ma old mafic rocks has also been discovered: those nature and relation to the ore-bearing Norilsk intrusions yet to be studied. The geochronologic study suggests, that: (1) ore-bearing massifs belong to the early emplacement phase (250-255 Ma); (2) ore-bearing massifs contain xenogenic Palaeozoic zircons, pointing to important role of the host-rocks; (3) Late Triassic igneous activity (225-230 Ma) has not affected ore systems.

The Maksovo shungite-bearing metasapropelite (maksovite) deposit is located in the eastern part of the Onega Basin that was initiated and formed in the Paleoproterozoic in the southeastern Fennoscandian Shield. The maksovite deposit represents a diapiric fold formed about 2050 ± 10 Ma ago. It is underlain by carbonate sequences and, in turn, overlain by tuffaceous siltstones and intruded by gabbro-dolerites (1956 ± 5 Ma). Unaltered maksovites represent pelitomorphic rocks with a massive or obscure-layered structure containing about 30% C org . Alterations superimposed on the maksovites and underlying tuffaceous siltstone sequences are developed along brecciation zones within the ridge-shaped fold. The alterations are represented by alkaline Fe–Mg metasomatites with brecciated structures, as well as heterogeneous mineral and chemical compositions. They differ in terms of intense biotitization, chloritization, and development of the apatite-bearing albite–carbonate and sulfide-bearing carbonate–quartz stringers. Alteration zones are enriched in Na, K, P, Ti, Mg, Fe, and other ore components. Based on the Re–Os dating of sulfides, the age of metasomatites is estimated at 1558 ± 61 Ma.

The mantle xenoliths of lherzolite composition from Mesozoic alkaline–ultrabasic diatremes of Jetty Oasis were studied. The treated xenoliths represent the mantle section of the East Antarctic Craton down to depths of 60–80 km. The osmium isotope composition of these nodules testifies to the beginning of the formation of the lithospheric mantle in the considered region of the craton 2400 Ma ago. The absence of any signs of Early Archeozoic lithosphere points either to partial destruction of the lithosphere at the convergent boundary of the plates in the Late Archean or to thermal erosion of the Archean lithosphere under the effect of a deep-seated plume in the Mesozoic during rift formation.

This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.