Volume 12, Nº 1 (2018)

Correlation of the Permian continental and marine deposits of Northeastern Russia, the southern Far East, Siberia, and the Pechora Сisurals is carried out. A consistent zonal succession of brachiopods, marine bivalves, and ammonoids is revealed and linked with the macroflora in the boundary deposits of the Cisuralian/Biarmian Series of the Boreal Superrealm. As a result, analogues of the Solikamian, Irenskii, Filippovskii, and Saraninian Horizons of the Kungurian Stage are established in the main coal basins and marine sequences of Northeastern Russia and the southern Far East. The correlative floristic horizon, stretching from the east of the East European Platform to the Pechora Cisurals, Pai-Khoy, Siberia, the Kuznetsk Basin, Northeastern Russia, and the southern Far East is established. The unity of the Sheshmian–Kazanian nonmarine floral assemblages and nonmarine bivalves, which correspond to the marine biota of Kazanian age, and their distinction from Kungurian assemblages are established. The Kungurian–Kazanian boundary is traced in marine and continental deposits within the entire Boreal Superrealm. The invalidity of the Ufimian Stage is established. The Kazanian Stage corresponds to the Roadian Stage of the International Chronostratigraphic Chart; however, the lower boundary of the Kazanian Stage is not defined precisely and can be conventionally considered isochronous to the boundary of the Roadian Stage.

The Dzheltula alkaline massif is located in the Tyrkanda ore region of the Chara–Aldan metallogenic zone of the Aldan–Stanovy Shield (South Yakutia). The region contains separate placer gold objects, which are being explored at the present time, and ore-bearing Mesozoic alkaline intrusions, which are weakly studied due to their poor accessibility. The Dzheltula massif (DM) is the largest exposed multiple-ring intrusion within the Tyrkanda ore region; therefore, it is considered as a typical object for geological, petrological, geochronological, and metallogenic studies. The DM consists of five magmatic phases of syenite composition. ⁴⁰Ar–³⁹Ar dating has established that the crystallization age of the oldest phase, the leucocratic syenite porphyry (pulaskite), is 121.1 ± 1.3 Ma. The crystallization age of the cross-cutting phases represented by syenite–porphyry dikes (laurvikites and pulaskites) ranges from 120.1 ± 2 to 118.3 ± 2.1 Ma. The youngest phase of the massif, trachyte, crystallized at 115.5 ± 1.6 Ma. According to the mineralogical and geochemical studies, two types of ore mineralization, namely gold and uranium–thorium–rare-earth (U–Th–REE), are established within the DM. The gold mineralization was found in the quartz–chlorite–pyritized metasomatites. It is confined to the NNE- and NNW-trending fault zones and coincides with the strike of the syenite porphyry dike belt. Uranium–thorium–rare-earth mineralization has been established in the quartz–feldspathic metasomatites localized in the outer contact of the massif. The juxtaposition of mineralization of different types in some zones of the Dzheltula syenite massif significantly increases the ore potential of the studied object within the Tyrkanda ore region.

It has been observed that the intensity of underwater gas flares unexpectedly increased after the deep-focus (625.9 km) earthquake that occurred in the Sea of Okhotsk on August 14, 2012. In this regard, we have analyzed the data resulting from interpretation of the focal mechanism for the strike-slip earthquakes which occurred in the Benioff seismic zone of the subducting Pacific Plate within the Sea of Okhotsk region over the period from 1977 to 2010. The NNW sinistral and NE dextral faults are found to form a conjugate system due to the WNW stress field. We have established that the dextral faults are mostly common at a depth of about 200 km along the Kuril Islands extension, while the sinistral ones are concentrated in the Nosappu Fracture Zone and traced to the NNW down to a depth of 680 km. The area of the gas flare discharge and gas hydrate accumulations have the same (NNW) direction. Thus, we have revealed that the Nosappu Fracture Zone appears to be a structure which controls fluid fluxes, providing permeability of the subducting slab of the Pacific Plate for ascending fluids from the lower mantle.