The paper considers the results of a study of particles of carbonaceous substance and sulfur isotopes of associated sulfides in metapelites of the Neoarchean banded iron formation (BIF) of the Kostomuksha greenstone belt of Karelia (Karelian Craton of the Fennoscandian Shield). According to the petrographic observations, the carbonaceous matter occurs within and between silicate minerals’ grains, inside sulfides or at the grain boundaries, separating sulfide crystals from biotite or amphibole. Scanning electron (SEM) and atomic force (AFM) microscopy revealed the several types of the carbonaceous material varying in structure and carbon content. Raman spectra approved both well-structured graphite and weakly structured graphite (kerogen) components of the carbonaceous substance. The isotopic composition of total organic carbon is typical for biogenic processes. The obtained δ13Corg value within the range of –27,9– –30,6‰ is consistent with carbon fixation by photo- or chemoautotrophs. The sulfur isotopy of the associated sulfides is marked by positive Δ33S anomaly (up to +0.94‰) and negative δ34S values (–2.06‰ ─ –4.1‰). Positive Δ33S values indicate sulfur genetic association with photochemical elemental sulfur (S8) from the atmosphere, while negative δ34S values reflect isotope fractionation in bacterial-mediated processes. Based on these observations, we believe that the initial carbonaceous substance has mainly organic origin.

Gold-platinum mineralization was discovered in the ultramafic-mafic rocks of the Ariadnoe massif of the Sikhote-Alin orogenic belt. In this paper we show that ultramafic (peridotite and pyroxenite) and mafic (ilmenite and hornblende gabbro) rocks form a single series with a gradual accumulation of rare and rare earth elements of more differentiated varieties. New age determinations for zircon from ilmenite gabbro are given (164 ± 0.48 Ma). We distinguished four varieties of gold differing in the content of Au, Ag, Cu, and Hg. Platinum-bearing minerals are isoferroplatinum and cuprite. The isotopic composition of sulfides from ultramafic rocks suggests the mantle source, while sulfides from ilmenite gabbros are characterized by isotopically light sulfur indicating the possible involvement of crustal rocks in ore genesis. Carbon isotope analysis of the carbon-bearing matter of mafic-ultramafic rocks showed the presence of mantle fluids and isotopically light biogenic matter from sedimentary rocks. The presented data indicate the influence of mantle and crustal processes on the formation of ore-bearing mafic and ultramafic intrusions.

The diversity of the tholeiitic, alkali or calc-alkali, high-silica, and adakitic rocks (I-, FG- and А-types) in the northeastern margin of Asia often leads to controversial conclusions about the character of magmatism and the active margin evolution in the West Pacific during the Late Mesozoic–Cenozoic. In addition, paleogeodynamic reconstructions of the Asia-Pacific region can only be made based on the synthesis of patterns identified in compositions of magma sources, evolution and character of magmatism, and strain and kinematic analysis of fault tectonics of all parts of the eastern margin of the paleo-Asian continent. The paper presents new isotopic, geochemical, and structural data on one of the largest early Paleogene structures located at the continental margin of the southern Sikhote-Alin. Based on the new and previously published [49, 52] data we have concluded that the tectonic and magmatic settings of the region were shaped by oblique interaction of continental and oceanic plates during the Late Cretaceous-early Paleogene. The igneous products of the frontal (FG-type), in respect to the trench, and intracontinental (А-type) parts of the area are characterized by isotopic-geochemical variations caused by thermal changes in upwelling asthenosphere and by interaction with lithospheric components. These processes accounted for the formation of initial magmas similar to the IAB- or OIB-type mantle source, respectively.

The results of detailed mineralogical and geochemical studies of precious metals from ultrabasic rocks of the Ariadnoe massif (Sikhote-Alin orogenic belt) are presented. The presence of several varieties of gold with different ratios of Ag, Cu, and Hg has been revealed. Isoferroplatinum predominates among platinum minerals. The isotopic composition of ultrabasite sulfides corresponds to the mantle source, while basites are characterized by isotope–light sulfur, indicating the possibility of participation in the oreogenesis of crustal rocks. Isotope-carbon analysis of igneous rocks indicates that they contain derivatives of deep fluids and isotope-light biogenic matter of sedimentary rocks. The presented data show that mantle and crustal processes were involved in the formation of ore-bearing intrusions of ultrabasic–basic rocks. The association of ilmenite, gold, and platinum in ultrabasites and basites, a derivative of these processes, can serve as a search criterion for the detection of industrially promising sources of strategic metals.

In the south of the Russian Far East, a new promising type of sources of strategic and critically important metals (titanium, gold, platinum, niobium, hafnium, copper, antimony, etc.) has been identified: those are complex ores and placers spatially and genetically related to the late mesozoic (cenomanian) synorogenic intrusions of ultramafic-mafic rocks of the Sikhote-Alin orogenic belt. An example of this is the Ariadnensky massif of ultramafic, mafic and granitoid rocks with manifestations of gold-titanium mineralization in its mafic part, gold-antimony mineralization in the exocontact, and gold-copper mineralization in the near-intrusive zone. The main mineralogical and geochemical features of these ore formations have been determined. The typomorphic properties of native gold from ultramafic rocks have been revealed. It is shown that mantle and crustal processes were involved in the formation of different types of ore. The materials obtained provide new opportunities for the reassessment of the strategic metals resource potential of Primorye.

New data are reported on the age of Triassic-Jurassic cherts replaced up the section by siliceous mudstones, and then by mudstones, which together with basalts form thin (up to hundreds of meters) plates and lenses that pinch out along the strike at different levels of the multi-kilometer terrigenous section of the Ulban terrane (zone). In the Nimelen subzone (the Albazino gold deposit area), their time interval of formation is Norian-Early Toarcian and that of host terrigenous deposits is Pliensbachian-Bathonian. In the Mewachan subzone, cherts and siliceous–clayey rocks are Middle Triassic-Callovian in age and terrigenous rocks are Middle-Late Jurassic (including Tithonian). A comparison of deposits of the Ulban terrane with deposits of the Samarka terrane which are well-studied and similar in age and composition allows us to consider the Ulban terrane (zone) as part of the Jurassic accretionary complex of the Sikhote-Alin orogenic belt. There are also sufficient indications to believe that its structural features are consistent with the subduction model. The basis for this is that the Triassic-Jurassic cherts and siliceous–clayey rocks accumulated for about 45 million years at a rate of about 1.8 m/million years characteristic for the oceanic plate sedimentary cover. At the same time, a gradual transition from cherts to mudstones is observed evidencing the movement of the oceanic plate into the subduction zone. The inclusion of its fragments in the terrigenous section is the result of their being detached in the trench and under the overhanging slab. Tectono-stratigraphic columns of the subzones of the Ulban terrane and a scheme of zoning of the Jurassic accretionary prism have been compiled with four structural-age levels along its entire length.

The Ildeus ore-magmatic basite–ultrabasite system in the central part of the Stanovoy superterrane formed in the Triassic as a result of subduction of oceanic lithosphere of the Mongol–Okhotsk basin. In the Jurassic and Early Cretaceous, it underwent hydrothermal–metasomatic alterations during collision and postcollision processes within the southern margin of the Siberian continent. Hydrothermally altered ultrabasites and felsic–alkaline albite–quartz–biotite–K-feldspar–apatite (with calcite and barite) metasomatites of the Ildeus contain rare earth element (REE) minerals, represented by monazite in association with apatite, xenotime, oxides, REE carbonates, and REE silicates. Native metals and alloys of Ag, Au, Cu, Ni, Zn, Pt and sulfides of Fe, Co, Ni, Cu, Pb, and Zn are associated with REE minerals in rocks of the massif. The total REE content in these rocks varies from 10 to 1938 ppm, correlating positively with the concentrations of barium (up to 5876 ppm) and thorium (up to 74.5 ppm). Alkaline-silicate metasomatites with REE minerals are spatially associated with adakite dikes and veins (Sr/Y from 27 to 1716) and were formed in the presence of aqueous–carbonate–sulfate–phosphorus–potassium fluids with hybrid properties characteristic of the fluid phase of mantle alkaline–ultrabasic–carbonatite complexes, on the one hand, and lower crustal adakitic melts, on the other. It is suggested that the enrichment Ildeus ultrabasites and metasomatites with rare earth minerals, metals, and sulfides is associated with the melting of the sulfidized thickened lower crust under the influence of deep mantle fluids and intrusion of Early Cretaceous metal-bearing adakites into Triassic suprasubduction igneous complexes.

A new promising source of mineral deposits is found in the southern part of the Far East of Russia: the Ti-bearing intrusions of ultramafic rocks of the Sikhote-Alin orogenic belt. The main mineralogical–geochemical features of antimonite–quartz veins are determined at the external contact of the Ariadnoe intrusion. It is shown that mantle and crustal processes were involved in the formation of Au–Ti and Au–Sb ores. The typomorphic properties of native gold in ultramafic rocks open new possibilities for re-estimation of the prospects of a mineral base of strategic metals of Primor’e.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070152

In this paper, we discuss new data obtained by petrographical, geochemical, geochronological, and isotopic–geochemical study of magmatic rocks within the Malmyzh and Gion gold–copper-porphyry ore fields. Geochronological data show a Late Cretaceous age of their magmatic crystallization: Cenomanian (97–99 Ma) and Campanian (76–82 Ma) ages, respectively. Based on a comparative analysis of the studied samples igneous rocks with each other and with magmatic rocks of worldwide porphyry deposits, the results of a study using a secondary ion mass spectrometer of the patterns of distribution of trace elements (REE + Y, Hf, Ti, U, Th, and Pb) in accessory zircons from igneous rocks of the Malmyzh and Gion ore fields are discussed in order to estimate their potential ore content in the gold–copper-porphyry mineralization. Despite the fact that economic gold–copper ore mineralization within the potential Gion ore field was previously unknown, an analysis of the results shows, that according to the obtained values of indicative geochemical parameters of accessory zircons, the granitoids involved in its geological structure practically do not differ from the granitoids of both the neighboring Malmyzh deposit and most of the worldwide porphyry gold–copper deposits.

An Erratum to this paper has been published: https://doi.org/10.1134/S1819714023060106

The morphology, mineral and chemical composition (48 elements) of ferromanganese crusts from the northern part of the Emperor Ridge (Detroit, Hanzei, Suizei guyots), the Amlia, Rat and Stalemate fault zones at the north west of the Pacific Plate, as well as volcanic uplifts of the Kuril and Aleutian island arcs were studied. The contents of major, trace and rare-earth elements were determined in the major mineral fractions of ferromanganese crusts (carbonate, oxide manganese, hydroxide ferruginous) which served as sorbents of cobalt and other strategic metals, as well as in the residual fraction. It was established that hydrogenic crusts containing strategic metals that indicate potential economic significance are widespread in the North Pacific. Criteria are proposed for evaluating the contribution of various metal sources to the formation of crusts, which can also be used in the study of other similar objects.

The results of studies of carbonaceous matter (CM) and the S isotopic composition of associated sulfides in metapelites of the Neoarchean banded iron formation of the Kostomuksha greenstone belt of Karelia (Karelian Craton of the Fennoscandinavian Shield) are presented. The petrographic observations show that the CM occurs inside and between silicates, in sulfides, or at the grain boundaries between the sulfide crystals and biotite or amphibole. The results of scanning electron and atomic force microscopy showed the presence of several CM types distinct in structure and C content. The analysis of Raman spectra of CM revealed the presence both of well-ordered graphite and weakly structured kerogene in samples. The isotopic composition of the total organic carbon is typical of biogenic processes. The δ 13 C org values from –27.9 to –30.6‰ are consistent with the fixation of carbon by photo- or chemoautotrophs. The S isotopic composition of associated sulfides is characterized by a positive Δ 33 S anomaly (up to +0.94‰) and negative δ 34 S values (from –2.06 to –4.1‰). The positive Δ 33 S values indicate a genetic link with photochemical elemental sulfur (S 8 ) from the atmosphere, whereas the negative δ 34 S values reflect the fractionation of isotopes during bacterial-related processes. Based on these observations, we suggest that the primary CM mostly has a biogenic origin.

A new promising type of mineral resources, such as complex ores and placers spatially and genetically related to Late Mesozoic ultramafic intrusions, has been identified within the Sikhote-Alin orogenic belt. It is exemplified by the Ariadnoe massif of ultramafic rocks, in the center of which there is a gold–titanium mineralization deposit, and at the exocontact, a gold–antimony mineralization. The main mineralogical and geochemical features of gold–copper formations in its circum-intrusive zone are determined. Special focus is given to the finds of cuproauride, which are uncommon for the study area. To reconstruct the conditions of forming these ores, the isotope composition of sulfur in sulfide minerals is studied. The obtained data indicate the significant metal-bearing potential of the ultramafic rocks in Sikhote-Alin.

The distribution of Fe, Mn, Cu, V, Zn, and Ni in the mineral fractions of ferromanganese crusts of different genesis, which were formed within island arcs, is considered for the first time. Hydrothermal Fe–Mn crusts from an underwater dome located 47 km to the NNW from Chagulan Island (Aleutian Island Arc) contain up to 12 511 ppm Cu. Hydrothermal Fe–Mn crusts from the Kuril Island Arc (KIA) contain up to 1073 ppm Zn. The nickel concentration (2078 ppm) in hydrogenetic Fe–Mn crusts from the KIA is comparable to its content in the Co-rich crusts. The results of sequential leaching show that up to 90% of the total copper is sorbed by Mn oxides in hydrothermal deposits. The portion of Cu is higher in the Mn fraction from hydrogenetic Fe–Mn crusts subjected to hydrothermal influence. This trend is typical of Zn and V.

The Sikhote–Alin orogenic belt hosts ophiolites, which are confined to the upper structural level of the Jurassic accretionary prism; however, their age and paleogeodynamic formation conditions are a matter of debate. We present the results of isotopic–geochronological and petrological–geochemical study of rocks of the Breevka and Chuguevka gabbro-ultramafic massifs of the Kalinovka ophiolite complex. These massifs formed in the Late Permian rather than in the Devonian–Carboniferous as was suggested previously. The geochemical features of rocks indicate their formation most likely in an island arc system. Taking into account these results, we can conclude that the upper structural level of the Jurassic accretionary prism of the Sikhote–Alin orogenic belt hosts various rock complexes of the oceanic lithosphere distinct in age and the geodynamic setting. The Breevka and Chuguevka gabbro-ultramafic massifs are fragments of the Late Permian ophiolite complex, which formed in different parts of the island arc system (back-arc or intra-arc basins).

This paper reports new geochronological data on metagranitoids (U–Pb SIMS) and ophiolites (Sm–Nd) from the Khanka massif. New and published data define the Early Neoproterozoic Matveevka–Nakhimovka terrane with 935- and 915-Ma early suprasubduction magmatism, 850–880-Ma and 757-Ma withinplate and Pacific-type transform margin magmatism, as well as the Late Neoproterozoic–Early Cambrian Dvoryan and Tafuin terranes with 543, 520, 517, and 513-Ma suprasubduction magmatism. These two terranes are separated by a suture (Voznesenka and Spassk terranes) formed by Ediacaran–Cambrian shelf deposits and a Cambrian accretionary wedge with ophiolites older than 514 Ma. The greater part of the Khanka massif formed in the late Cambrian, with the Kordonka island-arc terrane accreted at the end of the Silurian. The Sergeevka terrane of the Ordovician island arc joined it through the Early Cretaceous strike-slip movements. Heterogeneous structures of the main part of the Khanka massif can be traced to the north based on the analogous stages of magmatism and metamorphism, where the Jiamusi massif (including the East Bureya terrane) is an Early Neoproterozoic block and the eastern Songnen massif (including the West Bureya terrane) is a Late Neoproterozoic–Cambrian block. These blocks are separated by the Spassk–Wuxingzhen–Melgin suture formed by their collision in the Late Cambrian. The Bureya–Songnen–Jiamusi–Khanka superterrane formed as a part of the Gondwana supercontinent approximately 500 Ma ago through orogeny and accretion of the Rodinia supercontinent fragments.

The sulfur isotope anomalies ∆33S and ∆36S known today in ancient rocks exhibit common geochemical patterns reflected in the existence of a correlation like ∆36S ≈ –∆33S for sulfides from Archean formations of Australia, Africa, and America. To understand the scale of this phenomenon, we investigated the pattern of sulfur isotope fractionation in sulfides from rocks of the Irkut Block of the Sharyzhalgai Uplift of the basement of the Siberian Craton, as well as the Leksa ore occurrences located in the Karelian Province. It was shown that the objects of our study held ∆33S and ∆36S isotope anomalies. This leads to the conclusion that the geochemical processes responsible for the generation of sulfur isotope anomalies are much more widespread than was assumed until now and allows us to recognize them as a phenomenon of planetary significance. The fact that the relationship between ∆36S ≈ –1.0 ∆33S isotope anomalies demonstrates the same characteristics as in other Archean rocks of the most ancient shields worldwide indicates the similar conditions and mechanisms for fractionation of sulfur isotopes at the stages of its transformation in an atmospheric photochemical cycle.