The Sm-Nd geochronological study was performed to investigate rare-metal pegmatites from the two unique deposits, i.e., the Kolmozero lithium deposit and Shongui deposit with beryllium mineralization (Kola Peninsula, Russia). For Kolmozero lithium deposit was obtained the Sm-Nd isochrone, corresponding to an age of 1705 ± 60 Ma with high εNd(T ) = +9.1. For Shongui beryllium deposit was obtained the Sm-Nd age, corresponding to an age of 1747 ± 33 Ma with high εNd(T ) = +9.7. This age values are close to the ages of metamorphism obtained earlier by Rb-Sr, K-Ca, and K-Ar methods. Pegmatites are characterized by a wide range of εNd(T ) values from +2 to +16 and 147Sm/144Nd ratios up to 0.3. Possible reasons for disturbance of the Sm-Nd isotope system of pegmatites are analyzed, including multicomponent mixing, fluid influence and metamorphic overprinting. The highly radiogenic signatures of rare metal pegmatites of the Shongui and Kolmozero deposits were found to appear by fractionation of Nd and Sm and their different redistribution with the change of the Sm/Nd ratio. High εNd(T ) values and changes in Sm/Nd ratios indicate the role of REE (rare-earth element) fractionation, while narrow εNd(T ) ranges suggest interaction with fluids during pegmatite formation. These findings emphasize the need for further research into the composition of fluids and their influence on isotope systems.

This paper presents the results of a Sm-Nd study of sulfide minerals and whole-rock samples from Cu-Ni-PGE layered complexes of the Fennoscandian Shield. Syngenetic (early) and epigenetic (late) sulfides were analyzed in each complex using the Sm-Nd method. Late sulfide minerals with low Sm/Nd values (the 147Sm/144Nd ratio is often in the range of 0.02-0.07) are associated with an increased mobility of Nd relative to Sm, resulting in a relative excess of Nd compared to Sm in these sulfides. Simultaneously, early sulfides, which are deposited during the magmatic stage of ore formation, typically exhibit higher Sm/Nd values (the 147Sm/144Nd ratio is frequently above 0.07). Additionally, Sm-Nd isotope data for sulfide minerals were used to date ore-forming processes in two Cu-Ni-PGE complexes-Nyud-II (Monchegorsk area, Russia) and Ahmavaara (Finland). The Sm-Nd ages of syngenetic and metamorphic ore from these complexes were determined. Syngenetic ores formed at 2496 f 36 Ma (Nyud-II) and 2441 f 93 Ma (Ahmavaara), while metamorphic ores formed at 1940 f 32 Ma (Nyud-II) and 1904 f 24 Ma (Ahmavaara). Thus, Sm-Nd isochrons yield the timing of sulfide mineralization and its relationship with the ages of the rocks containing it, while Sm/Nd ratios in sulfides help understand the processes of ore formation. A comprehensive analysis of the full isotopic dataset (this study and other published data) showed the potential of using Sm-Nd isotope data to trace the sequence of sulfide mineralization, which has been confirmed for some hydrothermal deposits. However, this sequence has not been confirmed for magmatic sulfides; this opens up the possibility for further research.

The Porya Guba clinopyroxenite-wehrlite complex is located in the core of the Lapland-Kola collisional orogen (similar to 2.0-1.9 billion years old) in the northeastern part of the Fennoscandian Shield and contains iron-titanium-vanadium and nickel-copper mineralization with platinum group elements (PGEs). The controversial geological position of the complex within the mafic granulites of the Kolvitsa melange (pre-, syn- or post-orogenic) is clarified by Sm-Nd isotopic dating of the rocks and mineralization. The Sm-Nd age of the barren clinopyroxenites that dominate the complex is 1858 +/- 34 Ma (epsilon Nd(T) = -1.5) and is interpreted as the time of its emplacement as evidenced by a sample from the largest intrusion, named Zhelezny. This age is younger than that of the peak of granulite metamorphism in the host rocks (1925-1915 Ma) and coincides within error with the age of rutile from granulites (1880-1870 Ma), indicating the time at which cooling to 450 degrees C occurs. Emplacement in the cooled rocks is confirmed by the detection of quenching zones in clinopyroxenites around granulite xenoliths. Magnetite ores, as well as mineralized pyroxenites with sulfide disseminations, are formed during a late stage of the complex development, as suggested by active assimilation of granulite xenoliths by these rocks. The isotopic age of mineralized pyroxenites enriched in PGEs is 1832 +/- 35 Ma (epsilon Nd(T) = -2.0), while the age of magnetite ores is 1823 +/- 19 Ma (epsilon Nd(T) = -2.5). Thus, the obtained isotopic data indicate that the emplacement of the Porya Guba complex and probably other small mafic-ultramafic intrusions in the Kolvitsa melange granulites took place after the end of the Lapland-Kola collision.

The isotopic age of rocks from the Porya Guba clinopyroxenite–wehrlite complex hosting the Kolvitsa Fe–Ti–V deposit is determined for the first time. The Sm–Nd age of the barren clinopyroxenites prevailing in the studied massif is 1858 ± 34 Ma (εNd(T) = –1.5) and is considered as the time of emplacement of the Porya Guba Complex that occurred after the peak of granulite metamorphism (1925–1915 Ma). Quenching zones found around xenoliths of granulites in clinopyroxenites indicate the emplacement of the complex into the cooled rocks of the Lapland–Kola orogen, which is consistent with the estimated time of its cooling (1880–1870 Ma, 450°, by rutile). Mineralized rocks, as inferred from active assimilation of granulite xenoliths, are formed at a late stage of development of the complex: the age of mineralized pyroxenites enriched in platinum and palladium (0.8 g/t) is 1832 ± 35 Ma (εNd(T) = –2.0), while the age of titanomagnetite ores is 1823 ± 19 Ma (εNd(T) = –2.5). Thus, the obtained isotopic data indicate that the emplacement of small ultramafic intrusions developed in the Kandalaksha–Kolvitsa granulites (Kolvitsa Melange) took place during the cooling stage of the Lapland–Kola orogen.

Due to tectonic uplift in the Cenozoic and numerous shelf-wide glaciations during the Quaternary, ∼1–2.5 km of sedimentary overburden has been eroded from the Barents Sea shelf, leading to the exhumation and partial uncapping of hydrocarbon accumulations. Widespread natural gas and oil leakage from the glacially eroded middle-upper Triassic reservoir directly into the water column has been documented at the Sentralbanken high in the northern Norwegian Barents Sea. However, it remains unclear whether the hydrocarbon leakage occurs only from the middle-upper Triassic reservoir units in geological settings exceptionally conducive to hydrocarbon leakage, or if other reservoir formations contributed to the release of hydrocarbons into the water column. It is also not clear whether complete erosion of the caprock is a prerequisite for widespread liberation of natural gas and oil from glacially eroded reservoirs across Arctic continental shelves. Here we analyze multibeam echosounder data covering ∼5,000 km2 and a suite of high-resolution P-cable seismic lines from a range of geological structures across the northern Norwegian Barents Sea. Our analyses reveal that ∼21,700 natural gas seeps originate from exhumed, faulted and variably eroded structural highs bearing a range of Mesozoic reservoir formations. All investigated structural highs fuel seabed methane release hotspots with no exception. Evident from observations of seismic anomalies, fluid accumulations are pervasive in the subsurface and likely to continue fuelling seabed gas seepage into the future. We also document that gas seepage through faults piercing overburden, caprocks and reaching potential reservoir levels is pervasive at all investigated structural highs. On the Storbanken high and the Kong Karl platform, such fault-controlled seepage is more prevalent than seepage from reservoir formations subcropping below the seafloor. Using a simple parametrization approach, we estimate that seeps identified within our multibeam data coverage produce a seabed methane flux of 61 x 107 mol/yr (9,803 ton/yr), which is one to two orders of magnitude higher than other globally known submarine methane seepage provinces. Fluxes of methane from sea water to the air above the thermogenic gas seep provinces in the northern Norwegian Barents Sea remain to be determined.

AbstractIn this study, we investigated the high-pressure (HP) metamorphism of the Precambrian continental crust exposed in the Zheltau terrane in South Kazakhstan (Koyandy complex) and the Chu-Kendyktas terrane in the North Tien Shan of Kyrgyzstan (Aktyuz, Kemin and Kokdzhon complexes) within the SW part of the Central Asian Orogenic Belt. HP quartz–feldspar lithologies of the Koyandy complex consist of migmatized kyanite-bearing garnet–mica paragneisses, garnet–kyanite paragneisses and their derivatives associated with eclogites. Paragneisses demonstrate prograde evolution involving mica dehydration melting and producing magnesium-rich garnet, kyanite and K-feldspar at the near-peak to retrograde stages at pressures of 15–18.5 kbar and temperatures of 800–870°C. The widespread growth of micas in these rocks reflects lower stages of retrogression at P = 10–12 kbar and T = 720–770°C. The age distributions of the cores of detrital zircon grains from the paragneisses indicate a predominance of Neoproterozoic and minor occurrence of Mesoproterozoic and Palaeoproterozoic sources of their protoliths. The ages of ∼487–485 Ma obtained from the zircon rims of the paragneisses reflect the timing of their HP metamorphic re-equilibration. These age clusters are consistent with the age estimates obtained from the rims of zircons in the eclogite-bearing garnet gneisses of the adjacent Aktyuz complex in the North Tien Shan. The P–T paths and zircon ages obtained from the high-grade quartz–feldspar gneisses of the Zheltau and Chu-Kendyktas terranes are thus interpreted to indicate involvement of the crustal material derived from the Precambrian basement (magmatic zircons aged ca. 844 Ma) and its Ediacaran–Cambrian sedimentary cover (detrital zircons with maxima at 1 Ga and 800–600 Ma) in the latest Cambrian subduction processes induced by the closure of the oceanic basins assigned to the Palaeo-Asian Ocean.

The cruise had two main objectives: Deployment of the two CAGE ocean floor observatories (OS1 and OS2) at shallow PKF site and deeper PKF site; CAGE ocean floor observatories were designed and build as collaborative work of CAGE scientists with Kongsberg engineers. Observatories have identical set up except that only one of them have side looking multibeam. The set up is: Seabed Platform/seabed lander/mooring frame (x2) – OS1 has black mooring frame, OS2 has grey mooring frame, CTD (x2), Oxygen sensor (x2), CH4 sensor (x2), CO2 sensor (x2), pH sensor (x1), Fluorometer (x2), ADCP (x2), Current profiler (x1), Multibeam echosounder (x1) – grey lander, OS2, Broadband Hydrophone (x2), Flowmeter (x2) For specific description of each lander, please refer to ‘taking over’ documents (WP4 team leader). Landers and sensors arrived to Tromsø with a track from Hamburg, A. Silyakova was a reference person to receive goods and shipping documents. Time period between 24 and 26 of June was the assemblage of observatories and tests of telemetry/communication/camera on a launcher. Pär Jeanson (PhD student WP4) and Reidar Kaasa (substitute engineer instead of Anoop in WP4) from CAGE were assigned to receive training on observatory assemblage/communication. 26 of June – taking over procedure. Sites for the deployment were discussed during preparatory phase. Water depth at the sites could not exceed 500 meters due to restrictions in relation to the recovery rope, which is only 500 meters long. Photographs from the tow cam used during CAGE 15-2 cruise (chief scientist on the cruise G. Panieri) revealed sites with bacterial mats on the ocean floor. Prior each deployment we did echosounder and multibeam survey to know where flares are highly concentrated. Information from the survey was mapped instantly. Target spots for both observatories were chosen based on all this combined information. Oceanographic survey in the area of shallow PKF methane flares; From the “Testing seep fertilization hypothesis” proposal:‘ During cruise CAGE 14-1 the USGS-GAS system detected elevated methane fluxes near the coast and over the shelf seep site in ca. 90m water depth. Methane fluxes above the 240 and 400m site are much less, although slightly elevated with respect to the open ocean (e.g. Vestnesa). Unexpectedly, high methane concentrations (up to 20nM) are often accompanied by low CO2 concentrations. Initial estimates of the total CO2 budget show that under those conditions seep areas are CO2 sinks. What are the biological, geochemical and hydrographic conditions that made these seeps a CO2 sink? Are the observations from CAGE 14-1 repeatable? And ultimately, what are the processes causing the strong CO2 consumption.’It was decided to test seep fertilization hypothesis during CAGE 15-3 cruise by conducting comprehensive water sampling for biogeochemical environment in the entire water column above the area of methane flares. At the same time, USGS-GAS system was onboard allowing to simultaneously measuring surface water/lower atmosphere gas concentrations. This potentially allows calculating vertical gas flux from one realm to another. Depending on available time, collaborators equipment and human resources, water from 64 CTD stations was samples for following parameters: CH4 concentration; discrete sampling to introduce into CDRS system – 13C CH4, CO2; pH; DIC and 13C DIC; DOC; MOx; FISH; DNA; DMSP; CDOM; Nutrients (nitrate, silicate, phosphate). The cruise may be known as: CAGE15_3

A microtomographic study of the internal structure of sulfide minerals from the ore-bearing rock varieties of two economically significant deposits in the Arctic zone of the Russian Federation, disseminated ore of the Pilgujarvi Cu–Ni deposit (Pechenga) and metalliferous gabbronorites of the platinum-bearing Fedorovo–Pansky complex (Kola Peninsula), was carried out. It was shown that all sulfide samples studied had a homogeneous structure without obvious defects or silicate inclusions larger than 1 µm. The absence of silicate microinclusions larger than one micron in sulfides testifies to the isomorphism of rare earth element (REE) occurrence in sulfides and eliminates, to a certain extent, the debatable problem of the influence of microinclusions on the results of Sm–Nd isotope-geochronological studies of sulfides. The presence of smaller (10–500 nm) silicate microinclusions is, with a high degree of probability, unable to control the total REE budget in a sulfide mineral. The conclusion of the absence of a significant effect of microinclusions on the obtained ages is confirmed by the results of Sm–Nd dating using sulfides from the same mineral aliquots: the Sm–Nd ages of the ores of the Pilgujarvi Cu–Ni deposit were estimated at 1965 ± 87 Ma; and the ore-bearing gabbronorites of the Fedorovo-Pansky complex, at 2482 ± 61 Ma. This agrees well with the datings obtained earlier using other isotopic systems (U–Pb, Re–Os).

From the afternoon of May 19th to the early morning of June 2nd 2017, CAGE-WP6 at the Department of Geology Uit, the Arctic University of Norway, arranged a scientific cruise aimed at investigating sediment cores and porewater, and water masses, at the western Svalbard margin, Fram Strait, East Greenland Ridge, and Storfjorden Trough, visiting methane seep sites off Vestnesa Ridge, and in Storfjorden Trough on R/V “Helmer Hanssen”. Investigated areas were (in order of visiting sites on the cruise): Prins Karls Forland (PKF) (overlap with ‘leg 1’ 17th to 19th of May – see Leg 1 report), southern Yermak Plateau, Vestnesa Ridge, East Greenland Ridge, Storfjorden Trough and Storfjorden. The scientific sampling was done within the framework of several ongoing projects at the Department of Geology, University of Tromsø: “CAGE – Centre for Arctic Gas Hydrate, Environment and Climate”-WP6: “Methane Release, Ocean Acidification and CO2”. Planned surveys north of Svalbard was abandoned due to extensive sea ice cover and the East Greenland Ridge was surveyed instead. Sea ice over outer Vestnesa prevented surveys there and Storfjorden trough was also completely covered, but the sea ice broke up towards the end of the cruise and thus could be surveyed during the very last part of the cruise. A total of 15 gravity cores (c. 60 m), and 20 CTD (conductivity-temperature-depth) casts were performed along the western Svalbard margin (Vestnesa and PKF and Yermak). Data were also collected at East Greenland Ridge and in Storfjorden Trough and Storfjorden, brine overflow was detected. The CTD casts and chirp- and multibeam lines from PKF May 17-19th are reported in the cruise report for Leg 1. Chirp profiles and multibeam lines were acquired during transits and in surveys (mapping of East Greenland Ridge, moraine systems and basins in Storfjorden Trough, active and inactive pockmarks at Vestnesa Ridge and over and to find potential core sites. The cruise may be known as: CAGE17_1_leg2

Banded iron formations (BIFs) are widespread over the world (3.81 Ga to 1.80 Ga) as the Algoma and Superior types. The paper provides new isotope (Nd-Sr, U-Pb) data on associated noble-metal mineralization in Algoma-type BIFs of the Fennoscandian Shield. U-Pb dating of accessory zircon applied to estimate the formation time of noble-metal-bearing skarn and related rocks in the Olenegorsk and Kirovogorsk BIFs, NW Fennoscandian Shield show that they occurred in the interval between the formation of basalt protolith (2.81 Ga amphibolites) and metamorphism in BIFs (2.75 Ga) to the formation of gold-bearing iron-rich skarn with native Au, Ag, Bi and tellurides (2.65 Ga) and low-temperature quartz-zeolite veins with redeposited Au (2.55 Ga). REE distribution in zircons and corresponding rocks indicated an important role of redox reactions in Fe and REE redistribution affected by reducing fluids on haematite-quartz protolith of BIFs.

Beryl is both an accessory and a rock-forming mineral in pegmatites that contain beryl, making it a major source of Be. Beryl-bearing pegmatites of the Shongui deposit, located in the Kola province of the Northeastern Fennoscandian Shield, hold beryl with a yellowish-greenish color. An investigation into the chemical composition of this beryl from pegmatite dike No. 7 has been performed for the first time via the secondary ion mass spectrometry (SIMS) technique, and the chemical composition of the beryl-bearing pegmatites has been analyzed for the first time by the inductively coupled plasma mass spectrometry (ICP-MS) method. These pegmatites have high concentrations (ppm) of Be (11.8), Li (30.9), Rb (482), Nb (50.3), Ta (14.6), Cs (66.8), and Mn (283) and low concentrations of Sr, Y, Ba, rare earth elements (REE), Zr, and Th. In the Shongui pegmatite field, concentrations of Be, Li, Rb, Cs, Nb, Ta, and Mn increase from barren to beryl-bearing pegmatites, whereas concentrations of Ba, Sr, Y, and REE decline. Rb/Ba, Rb/Sr, and Zr/Hf ratios, showing the fractionation degree, change from the barren to beryl-bearing pegmatites: Rb/Ba and Rb/Sr increase from 111 and 0.46 to 1365 and 8.06, respectively, and Zr/Hf decreases from 18.9 to 14.5. The chemical composition of beryl from the Shongui deposit is unique. This mineral has a concentration of 25,300 ppm of alkalis (Li, Cs, K, Rb, Na) and the average Li, Ce, and Na content is 4430, 5000, and 15,400 ppm, respectively. According to its chemical composition, the Shongui beryl belongs to the Li-Cs-Na type, a type that is not recognized in the available classifications. It is supposed that this beryl was mainly crystallized in the magmatic stage rather than in any hydrothermal and metasomatic stages. Two beryl groups have been distinguished in beryl-bearing pegmatite dike No. 7: beryl from the intermediate zone (Brl-I) and beryl from the core zone (Brl-II). These beryls are concluded to have crystallized in the following order: Brl-I and then Brl-II. Compared with Brl-I, Brl-II is depleted in Cs, Na, Cl, and H2O and is enriched in Fe and Mn. The Fe/Mn ratio varies from 9.18 to 16.50 in these beryls and their yellowish-greenish shades are thought to be driven by a large amount of Fe compared to Mn.

The cruise occurred from May 1st to May 9th 2016 and was part of the Centre of Excellence for Arctic Gas Hydrate, Environment and Climate (CAGE) at UiT – The Arctic of Norway. The main goal of the cruise was to recover two observatories that were deployed on June 30th and July 2nd 2015 during CAGE 15-3 (chief scientist Anna Silyakova). The sites were selected according to pictures taken during CAGE 15-2 cruise (chief scientist Giuliana Panieri) illustrating bacterial mats on the sea floor. The exact locations were decided just prior to deployment according to flare locations. The present cruise also aimed at investigating an area of extensive flares western Svalbard, particularly the shallow shelf and shelf edge. The addressed scientific topics include quantification of methane concentration in the water column, dissolved inorganic carbon, pH, microbial activity and identification, nutrients, DMSP, CDOM and current amplitude and direction. The cruise may be known as: CAGE16_4

Parceling the anthropogenic and natural (geological) sources of fossil methane in the atmosphere remains problematic due to a lack of distinctive chemical markers for their discrimination. In this light, understanding the distribution and contribution of potential geological methane sources is important. Here we present empirical observations of hitherto undocumented, widespread and extensive methane and oil release from geological reservoirs to the Arctic Ocean. Methane fluxes from >7000 seeps significantly deplete in seawater, but nevertheless reach the sea surface and may transfer to the air. Oil slick emission spots and gas ebullition are persistent across multi-year observations and correlate to formerly glaciated geological structures, which have experienced km-scale glacial erosion that has left hydrocarbon reservoirs partially uncapped since the last deglaciation ~15,000 years ago. Such persistent, geologically controlled, natural hydrocarbon release may be characteristic of formerly glaciated hydrocarbon-bearing basins which are common across polar continental shelves, and could represent an underestimated source of natural fossil methane within the global carbon cycle.

From the afternoon of May 15th to the afternoon of May 19th, CAGE-Centre for Arctic Gas Hydrate, Climate and Environment, the Department of Geoscience UiT, the Arctic University of Norway, arranged a scientific cruise to survey offshore Prins Karls Forland, Svalbard to perform CTD measurements and water sampling on R/V “Helmer Hanssen”. The purpose is to study the variations in methane release and its dependence on oceanographic changes. The area has been continuously surveyed for the last three years for methane concentration, and methane consumption by bacteria and other related data. Because of the good weather conditions time allowed survey of the outer part of the shelf west of Prins Karls Forland – the socalled ‘Masox area’. Here three CTD’s were taken and the area surveyed by echosounding (EK60), chirp and multibeam for combined flare survey (EK60) and geological recording of sedimentary environments (chirp and multibeam). A total of 69 CTD (conductivity-temperature-depth) casts were performed with 12 water bottles sampled for each CTD station. The cruise may be known as: CAGE17_1_leg1

—We present data on the geochronology, geochemistry, and Nd isotope composition of granitoids of the Gremyachikha and North Gremyachikha massifs (Kundusyul pluton) located in the Neoproterozoic metamorphosed island arc calc-alkalic volcanic rocks of the Talanovka–Bogorodka block in northern Kuznetsk Alatau (Martaiga uplift). The granitoids formed 890–880 Ma as a result of the accretion and collision of Neoproterozoic oceanic/island arc complexes with an unknown block formed by continent-marginal metasedimentary strata. The predominance of a metasedimentary source formed during the erosion of the early Precambrian and Neoproterozoic complexes is confirmed by the wide range of the ages of xenogenic zircons in the granitoids (2800 to 930 Ma) and by variations in the εNd values (−7.8 to −1.0) and model Nd age of the granites (2.20–1.64 Ga).

The main goal of CAGE 15-­2 cruise was to study the gas hydrate system and methane emissions off western Svalbard and in Storfjordrenna. We addressed this through a comprehensive scientific program comprising dives with the MISO-­‐Tow Cam adapted to the multicorer frame from UiT-­‐NPI (TowCam/Multicorer, TCM), methane measurements in sediments and water column, sediment coring (multicorer + gravitycorer), water column and sediment biogeochemistry, microbiology, micropaleontology, macrobiology, and bathymetric mapping. In addition, during the ecosounder and TCM surveys we collected data for selecting the locations for the CAGE observatories to be deployed during the cruise. The areas investigated were: W Prins Karls Forland (two sites at ca 90 m and 240 m water depth),An area located at the coordinate 78N 08E called “site 7808” (ca 90 m water depth; marker CAGE 882),Vestnesa Ridge (ca 1200 m water depth; markers CAGE 888 and 895),Storfjordrenna (two sites at ca 350, benthic station SR1, and 390 m water depth, Pingos site; marker CAGE 933),Craters area (ca 350 m water depth). We planned the following activities during the CAGE 15-­2 cruise: EM 300 Simrad swath bathymetry mapping to identify seabed morphologyMapping of flare distributionsCTD stations at different water depths and in different areas for measurements ofocean water masses characteristics, andwater sampling for water/gas chemistry and microbiology investigations across methane seeps.TCM surveys (video-­‐camera) to image seabed fluid flow expressions, sites of bacteria mats and gas bubbles. These results were used to define sampling stations and collect data for the future deployment of CAGE observatories (cruise CAGE15-­‐3)Repeated deployments with TCM to sample surficial and shallow sediments with respect to microbiology, geochemistry, biogeochemistry, and micropalentology.Gravity corer for studying sediment biogeochemistry, biomarkers, microbiology, and foraminifera.Van Veen grabs sampling for studying macrofauna.Scrape sampling to collect fauna communities and possible carbonate blocks. The cruise may be known as: CAGE15_2

2 Всероссийский научно-исследовательский институт минерального сырья им

The research cruise was part of the Centre of Excellence (SFF) Centre for Arctic Gas Hydrate Environment and Climate (CAGE) at UiT – The Arctic University of Norway. It was partly supported by The Norwegian Petroleum Directorate. From Tromsø, we visited Sentralbankrenna and Hopendjupet in the central Barents Sea in order to pursue the following scientific objectives: – Identify gas seepage associated with known and assumed sandstone reservoirs sub-cropping at the sea floor. – Identify gas seepage related to leakage along faults and geological structures breaching the seafloor. – Collect gravity cores, multibeam and sub-bottom data to establish how grounding zone processes impact marine-based ice sheet behaviour and trigger ice-stream retreat during deglaciation. The cruise may be known as: CAGE20_2

The effect of enrichment with Nd in sulfides from magmatic Cu-Ni-PGE complexes and sulfide ores from hydrothermal Pb-Zn, Au-Mo, and gold deposits was found and characterized. This paper concerns the report and analysis of isotopic geochemical data on the sulfide ores from the large Paleoproterozoic mafic–ultramafic magmatic Cu-Ni-PGE complexes of Fennoscandia and the literature data on sulfide ores from the Qingchengzi Pb-Zn deposit (northeastern China), Tokuzbay gold deposit (southern Altai, northwestern China), and Dahu Au-Mo deposit (central China). The mineral/rock partition coefficients for Nd and Sm (the DNd/DSm ratio) are defined as a prospective tool for the reconstruction of the sulfide mineral formation and geochemical substantiation of possible sources of ore-forming fluids for deposits of various genetic types. The observed selective Nd accumulation indicates either hydrothermal or metamorphic (metasomatic) impact, which is associated with increased Nd mobility and its migration or diffusion. Due to this process, there is a relative Nd accumulation in comparison with Sm and a consequent increase in the DNd/DSm ratio. At the isotopic system level, this leads to a sufficient decrease in the Sm/Nd ratio for the secondary sulfides of such kind. The revealed effect may serve as an isotopic geochemical marker of recent processes. These processes are quite frequently associated with the most important ore formation stages, which bear the commercially valuable concentrations of ore components. Sulfides from magmatic Cu-Ni-PGE complexes are more characterized by the selective accumulation of Nd in the sequential sulfide mineral formation. For sulfides from hydrothermal deposits, the effect of Nd enrichment is more intense and closely related to ore-forming fluids, under the influence of which sulfide mineralization is formed in multiple stages. The study aims at expanding the knowledge about fractionation and the behavior of lanthanides in ore-forming processes and allows the development of additional criteria for the evaluation of the ore potential of deposits with different geneses, ages, and formation conditions.