Vol 486, No 1 (2019)

The wettability by asphaltenes of siliciclastic and carbonate drill–cores from oil and gas condensate fields extracted with n-hexane and chloroform was studied. The values obtained for the drill–cores of wetting by asphaltenes indicate the effect of asphaltenes on the wettability change for various rocks.

The geophysical, sesimotomographic, and mineragenic data unraveling the regularities of the distribution of large and superlarge precious-metal and uranium-ore clusters in southeastern Russia, eastern Mongolia, and northern China are analyzed. It is shown that the fact that ore clusters and districts of global class are located above the perimeter of the oceanic slab, stagnated in the transitional zone of the mantle, were probably predetermined by the concentration of lower mantle fluid-thermal flows at the frontal boundary of the slab and in its flanks represented by sublatitudinal paleotransform faults.

The work presents the first results on the anisotropy of magnetic susceptibility in Hooker Island basaltoids; this anisotropy is related to the direction of motion of the melt, the location of eruption centers, and the morphology of igneous bodies. The peculiarities of the primary magnetic fabric revealed correspond to a trap mechanism of formation of the Franz Josef Land igneous province and reflect the simultaneous effect of multiple small eruption centers. Earlier conclusions about the long-term (during the Early Jurassic–Early Cretaceous) multistage magmatism history have not been supported.

The amount of hydrocarbon deposits per unit area of Yamal Peninsula is more than 100 times as much as the global average. The hydrocarbon deposits are generally situated in areas with high current geodynamic activity. According to the data of seismic tomography, in the Yamal area, the mantle structure is abnormal. The southern part of the Kara Sea, the Yamal Peninsula, and the western part of the Gydan Peninsula are involved into the large positive anomaly of the heat flow density, the epicenter of which occurs in the vicinity of the Rusanovskoye deposit. Almost all hydrocarbon deposits of Yamal are situated on the flanks of the West Siberian rift system and, simultaneously, in the gradient zones of the heat flow density.

This paper reports on diagnostic and structural studies that were first carried out for carbonaceous material of quartz–muscovite dynamoschists from the schistosity zone in biotite migmatites, pegmatites, and diabases of the southern part of the Baikal ledge of the Siberian craton. The carbonaceous material is represented by phanerocrystalline and microcrystalline graphite with residual hydrocarbon radicals. Native Ni, Sn, zincous Cu, Fe–Ni compounds, sulfides of Cu, rutile, monazite, and zircon were revealed in the intergrowths with carbonaceous material. The carbon isotopic composition ranges from –29.19‰ to –31.58‰, except for carbonaceous material from the schistocity diabase, where δ¹³C = –24.93‰. ⁴⁰Ar–³⁹Ar dating of muscovite gave an age of 1947 ± 7.8 Ma pointing to the relation between dynamic metamorphism with accretion of the Akitkan fold system and the ancient complexes of the craton. It was concluded that the deposition of native carbon and metals was caused by migration of essentially hydrocarbonate fluid in the formations of the upper crust (Fig. 4, Table 1).

On the basis of U–Pb dating of zircon and baddeleyite from gabbro–dolerite of the Goloustnaya dyke swarm (southern margin of the Siberian Craton), the age of basites was established as 1338.0 ± 2.9 Ma. It is shown that the basite intrusions of close ages from the Goloustnaya and Listvyanka areas (southern Siberian Craton) and Victoria Island (northern Laurentia, Barking Dog complex) could have been formed under the influence of the same mantle plume and belong to the same Large Igneous Province of Ectasian (Middle Mesoproterozoic) age.

The crystal structure (R = 0.0750) of fiedlerite-1A Pb₃Cl₄F (OH) · H₂O from ancient slags of Lavrion (Greece) was studied on a single crystal. The mineral is triclinic, a = 8.5741 (7) Å, b = 8.0480 (5) Å, c = 7.2695 (4) Å, α = 90.087 (5), β = 102.126 (6), γ = 103.424 (6)°, V = 476.37 (6) ų, Z = 2. The Pb²⁺ cations center the Pb(1)F(H₂O)Cl₆, Pb(2)(OH)₂FCl₅, and Pb(3)(OH)F₂Cl₅ bicapped trigonal prisms. In the structure there is an additional position Pb', filled by 10% with Pb²⁺. There are two main structural fragments alternating along the a axis: (100) layers of Pb(2)- and Pb(3)-centred polyhedra and zigzag chains, stretched along the b axis formed by Pb(1)-centred polyhedra sharing common edges. The IR spectrum of fiederlite-1A is given.

Data from the study of minerals of the liquidus association (olivine and spinel) from high-Mg basalts (up to 10 wt % MgO) of Menshyi Brat Volcano (Iturup Island) are reported. Based on these data, it was possible to estimate the water content and to study the evolution of volatile components in the primary basic magmas that formed the Medvezhia Caldera (Irurup Island), for the first time. It is shown that the initial water content in melts could reach 5 wt % at an oxygen fugacity corresponding to the NNO + 0.4 buffer. The further evolution of magmas included continuous degassing at a depth of ≤8 km. Hydrous fluid separated from basic magma could play a significant role in the formation of large crustal chambers of siliceous magma participation in catastrophic caldera eruptions.

The article describes the petrography and mineralogy of xenoliths ilmenite-phlogopite containing deformed and granular peridotites from the Udachnaya-Eastern pipe. The age of pholopite porphyroclast from the studied deformed xenoliths matches with age of Phl megacryst and itself hosted kimberlites from Udachnaya pipe indicating the following processes closed in time: (1) crystallization of the low-Cr megacryst association; (2) deformation of rocks on the mantle lithosphere–asthenosphere border during the kimberlite-forming cycle; (3) formation of protokimberlite melts.

The results of geochemical studies of the diamondiferous suevites of the Kara astrobleme (Pay-Khoy) using a new approach based on “area” microprobe analysis of suevite matrix and consolidated impact melt aggregates with subsequent data processing by multivariate statistic methods are described for the first time. At least three suevite varieties that differ essentially in geomorphology, mineralogy, petrography, and geochemical features have been recognized. The predominant protoliths of the rocks of the target are proposed for these suevite varieties on the basis of integrated data analysis.

The data obtained for 2015–2017 on the content and composition of aliphatic hydrocarbons (HCs) in particulate matter at the river–sea geochemical barriers (the Ob, Yenisei, Lena, Khatanga, Indigirka, and Kolyma rivers–the Kara, Laptev, and East Siberian seas) are presented. It was shown that the HC distribution coincided roughly with the content of particulate matter. The losses of the HC concentrations in mixing zones of riverine and marine waters in some cases exceeded 90% of the riverine supply. The HC concentrations in the pelagic zones of the seas were about the background values (2–7 µg/L). The behavior and composition of HCs are determined by the features of riverine drainage areas, sampling seasons, and time (high or low tide). The influence of anthropogenic supply was registered exclusively in the Gulf of Ob where the composition of alkanes was close to that of oil, with a HC concentration of 86 µg per mg of particulate matter. In other samples, natural HCs prevailed.

The regional gas geochemical profile was first performed in the South China Sea in the north–south direction in January 2017 (42nd cruise of the R/V Akademik Boris Petrov). Five zones with methane emission into the atmosphere with a maximum of 30 mole km^–2 day^–1, were revealed above the oil- and gas-bearing structures in the southern part of the sea, in the Nam Con Son Basin. Methane emission into the atmosphere is generally related to ascending migration of methane from hydrocarbon deposits along fault zones. The expedition was set up by the Council for the Earth’s Hydrosphere of the Federal Agency for Scientific Organization as part of the international project “The 2nd International Indian Ocean Expedition (IIOE-2).”

Numerical simulation of a tsunami from September 28, 2018, on Sulawesi Island (Indonesia) is carried out. It is shown that the observed distribution of tsunami heights within a large area can be explained by the direct effect of a strong earthquake, whereas in the source zone (area of the city of Palu) it was produced by an underwater landslide.

The GPS-based coseismic observations in the epicentral zone of the earthquake on the Sea of Okhotsk of May 24, 2013, are analyzed. The peculiarities of the changes in amplitudes of seismic waves with distance are revealed on the basis of records from Russian and worldwide seismic stations. The global propagation of P-waves is investigated for the Sea of Okhotsk and Bolivian (June 9, 1994) earthquakes, and the respective amplitudes are estimated at teleseismic distances.

This paper describes the Murman-2018 experiment on remote electromagnetic sounding in combination with frequency and audio magnetotelluric soundings. The experimental results made it possible to quantify for the first time in the scientific literature the position of the boundary of a sharp increase in rock resistivity at a depth of 10–15 km. The nature of the established boundary (the “impenetrability” boundary for direct current) is related to the transition of rock properties in the Earth’s crust from the fragile state in the upper crust to a plastic state at a depth of 10–15 km or more.

The results of mineralogical–geochemical studies of the oligotrophic pine–fruticulose–sphagnum segment of Vasyugan Swamp (West Siberia) in the winter of 2017 are presented. A mathematical model is developed for the depth distribution of chemical elements in water and acid extracts of peats, organo-mineral sediments, and inorganic soil. It is shown that two complex geochemical barriers related to the changes in filtration properties of soils and contributing to the formation and/or accumulation of Fe compounds and other chemical elements function in the peat deposit. The first (oxidizing, reduction, sulfide, and adsorption hydroxide) barrier is found approximately at a depth of 0.40–1.25 m; the second (alkaline carbonate and hydrolytic, adsorption hydroxide, clayey, and carbonate) barrier lies in the lower layer of the peat deposit (a depth of 2.25–2.50 m). The result obtained is important for understanding the production–destruction methane cycle.

This paper reports on the oxygen isotope composition of the Late Pleistocene and Holocene syngenetic ice wedges, which were exposed at Mamontova Gora and Syrdakh Lake, the Accelerator Mass Spectrometry dating, and the reconstruction of the winter air temperatures during ice wedge formation. Organic microinclusions from the ice wedges were directly dated, which allowed us to establish seven dates ranging from 13 to 19 ka BP. The age of the ice wedges is shown to be younger than 20 ka, but older than 10 ka BP. In the area of Mamontova Gora, δ¹⁸O is in the range of –24.7 to –30.9‰ for the Late Pleistocene ice wedges, and of –23.2 to –25.9‰ for the Holocene ice wedges. In the area of Syrdakh Lake, δ¹⁸O ranges from –29.2 to –32.5‰. At the Mamontova Gora site, the average winter air temperatures, which were reconstructed from the isotope data, ranged from –28 to –31°C during most of the period when the Late Pleistocene ice wedges were formed; the January temperature was –42°C, –46°C. At the Syrdakh Lake site, the Late Pleistocene winter conditions were more severe: the average winter air temperature ranged from –30 to –32°C, and the average January air temperature was –44, –48°C. In the Holocene, the average winter air temperatures were higher and ranged from –24 to –28°C, while the average January temperatures ranged from –36 to –42°C.