Diamonds from the Rio Sorriso placer in the Juina area, Mato Grosso State, Brazil, contain mineral inclusions of ferropericlase associated with MgSiO₃, CaSiO₃, magnesite, merrillite, and other minerals. The ferropericlase inclusions in Rio Sorriso diamonds are resolved into two distinct genetic and compositional groups: (1) protogenetic, high-Ni and low-Fe (Ni = 8270–10,660 ppm; mg# = 0.756–0.842) ferropericlases, and (2) syngenetic, low-Ni and high-Fe (Ni = 600–3050 ppm; mg# = 0.477–0.718) ferropericlases. Based on the crystallographic orientation relationships between natural ferropericlase inclusions and host diamonds, high-Ni and low-Fe ferropericlases originate in the upper part of the lower mantle, while low-Ni and high-Fe ferropericlases, most likely, originate in the lithosphere. Mineral inclusions form the ultramafic lower-mantle (MgSiO₃, which we suggest as bridgmanite, CaSiO₃, which we suggest as CaSi-perovskite, and high-Ni and low-Fe ferropericlase) and lithospheric (CaSiO₃, which we suggest as breyite, Ca(Si,Ti)O₃, and low-Ni and high-Fe ferropericlase) associations. The presence of magnesite and merrillite inclusions in association with ferropericlase confirmed the existence of a deep-seated carbonatitic association. Diamonds hosting high-Ni and low-Ni ferropericlase have different carbon-isotopic compositions (δ¹³C = −5.52 ± 0.75‰ versus −7.07 ± 1.23‰ VPDB, respectively). It implies the carbon-isotopic stratification of the mantle: in the lower mantle, the carbon-isotopic composition tends to become isotopically heavier (less depleted in ¹³C) than in lithospheric diamonds. These regularities may characterize deep-seated diamonds and ferropericlases not only in the Juina area of Brazil but also in other parts of the world.

—Studies have shown that the concentration of heavy carbon isotope in the organic matter (OM) in the surface layer of the marine sediment increases and the amount of terrigenous OM decreases by about 1.4 times with increasing distance from the Indigirka River delta from 50 km to 600 km. This is accompanied by 1.3–2.1 times decrease of heavy metals and 1.3–1.4 times decrease of rare-earth elements (REE). A strong correlation is observed between the contents of OM, heavy metals, and REE in marine sediments, with the exception of the Cd and W contents. At a distance of 50 km from the river delta, the heavy metals contents exceed their Earth’s crust clarke values, while REE contents are higher than those of the North American Shale Composite (NASC). The opposite pattern is observed at a distance of 600 km from the river delta.

The article is devoted to the four-year (2017–2020) monitoring of gas emissions from the bottom of the Seyakha Crater, located in the central part of the Yamal Peninsula (north of Western Siberia). The crater was formed on 28 June 2017 due to a powerful blowout, self-ignition and explosion of gas (mainly methane) at the site of a heaving mound in the river channel. On the basis of a comprehensive analysis of expeditionary geological and geophysical data (a set of geophysical equipment, including echo sounders and GPR was used) and remote sensing data (from space and with the use of UAVs), the continuing nature of the gas emissions from the bottom of the crater was proven. It was revealed that the area of gas seeps in 2019 and 2020 increased by about 10 times compared to 2017 and 2018. Gas in the cryolithosphere of the Arctic exists in free and hydrated states, has a predominantly methane composition, whereas this methane is of a biochemical, thermogenic and/or mixed type. It was concluded that the cryolithosphere of Yamal has a high level of gas saturation and is an almost inexhaustible unconventional source of energy resources for the serving of local needs.

A study of the distribution of methane cycle microbial communities in the upper layers of bottom sediments above large hydrocarbon reservoirs in the South Kara petroleum region of the West Siberian Province revealed the presence in these layers of both aerobic methanotrophic bacteria and anaerobic methanogenic archaea, as well as numerous heterotrophic microorganisms of various phylogenetic groups. Research was carried out in the Baydaratskaya Bay and in the east of the Pukhuchan Depression (southern part of the Kara Sea). Aerobic methanotrophic bacteria belonged to the families Methyloligellaceae, Methylophagaceae and Methylomonaceae were detected in the surface oxidized layers (0–2 cm, E_h from 60 to 175 mV) of bottom sediments. Moreover, representatives of Methyloligellaceae were found in quite significant amount (1.52–2.61% of all 16S rRNA gene sequence reads) at all studied stations of the Kara Sea. In the subsurface reduced layers (18–20 cm, E_h from –63 to –246 mV), methanogenic archaea were dominated by representatives of the order Methanomassiliicoccales (up to 3.3% of all 16S rRNA gene sequence reads). Methanogenic archaea of the orders Methanofastidiosales, Methanobacteriales and Methanomicrobiales were also discovered. In addition, aerobic/facultative anaerobic methanotrophic bacteria of the families Methylococcaceae and Methylomonadaceae were found on these reduced layers of the bottom sediments, but the relative abundance (in percentage of sequence reads of their total number) of anaerobic methanotrophic archaea was extremely low there. Apparently, the oxidation of methane in bottom sediments of the Kara Sea, where its concentration at most of the studied stations dramatically increased with sediment depth, occurs predominantly under aerobic conditions in the surface layers, where the relative abundance and phylogenetic diversity of methanotrophs are higher.