Specificity of the products of Tyatya volcano eruption in 1973

Based on 198 determinations of the complete silicate analysis of Tyatya volcano (Kunashir Island), we compared the data of the latter (1973) and all previous eruptions to reveal their differences and determine the evolution of Tyatya volcanism in the Holocene. The application of the estimation of the thermobaric parameters of the upper mantle magma chamber of the volcano made it possible to determine the temperature decrease in the magma chamber in 1973. An assumption was made about the polycyclic magmatic activity of the Tyatya volcano. The results of statistical processing of data on the thickness of tephra and the size of its fragments from the 1973 eruption are presented. Polynomial regressions of various degrees are applied. Models of tephra distribution based on three-dimensional trend analysis have been constructed. The results of the study are recommended for the creation of information databases on the petrochemistry of eruption products and the distribution of pyroclastics from volcanoes in the Kuril Island arc.

Genesis and Nd Isotope Composition of Ferromanganese Deposits of the Sea of Okhotsk and the Kuril Island Arc

—The Nd isotope composition of ferromanganese deposits (FMD) from the central part of the Sea of Okhotsk and the Kuril island arc has been studied. The results showed that diagenetic samples from the Deryugin Basin have a heterogeneous Nd isotope composition. The positive εNd values here might be both due to the input of a terrigenous impurity and due to diffuse endogenetic element supply. The FMD samples from the Sonne underwater ridge show a εNd value specific to seawater (–3.2). The εNd value of hydrogenetic FMD from Volcano 7.14 is –3.4, which corresponds to the εNd value of the Pacific water. The FMD samples from Volcano 5.5 are characterized by εNd = –2.0. The higher εNd value might be due to a moderate dilution of the hydrothermal fluid by seawater and might also indicate the presence of volcanic fragments in the FMD samples. The highest εNd value (+4.4) has been established for volcaniclastic sandstone saturated with Fe and Mn hydroxides. It points to a mixing of volcanomictic and hydrothermal materials.

ATAKAMIT AS A PRODUCT OF FUMAROLE MINERAL FORMED ON MODERN ON VOLCANOES

The results of electron microscopic, X-ray, IR-spectroscopic and X-ray microprobe studies of atacamite mineralization of fumarole origin on Alaid volcano (Kuril island arc) are discussed.

COMPLEX GEOLOGICAL-GEOPHYSICAL STUDIES OF THE UNDERWATER VOLCANO 7.10 (KURIL ISLAND ARC)

Submarine volcano 7.10, which is part of the North Iturup group of submarine volcanoes of the Kuril island arc, was studied in 5 voyages of the research vessel Vulkanolog in 1982–1989. Comprehensive studies have shown that the edifice of the 7.10 submarine volcano is composed of rocks of a range from dacites to basalts. The summit and slopes of the volcano are devoid of sediments, and the base is overlain by a sedimentary stratum, thickness of which reaches 800 m. The minimum depth recorded above the top of the volcano is 210 m. In the volcanic edifice, subvertical, northeastern and northwestern feeder channels, as well as peripheral magma chambers at depths of 2.5–3.0 km, were identified. It is assumed that during the terminal eruption, small lava flows poured out in the northeast and southwest directions, while the main lava flow poured out in the southeast direction and reached the base of the volcanic edifice.

Revealing of surface deformations induced by geodynamic processes in the Kuril island arc from GNSS data

<p>Kuril subduction zone is one of the most active continental margins due to the high plate convergence rate. Latest oceanographical, seismological and geological studies show a block structure of the Kuril island arc. In 2006-2008 Kuril GNSS network was installed along the island arc to provide information on the dynamics of the continental margin. Proper geodetic characterization of surface deformations in Kuril region is necessary for studies of regional geodynamical processes associated with seismic cycles and the evolution of the subduction zone. Since Kuril network has some disadvantages such as small amount of continuous stations (cGNSS) and its near-linear arrangement, special attention must be paid to correct processing of the GNSS data to exclude miscalculations that can affect further modeling of regional geodynamical processes.</p><p>We use regression analysis of time series of cGNSS stations displacements to distinguish components which are related to: 1) long-term accumulation of elastic stresses (secular velocity); 2) almost instant release of substantial part of accumulated stresses during main shock (coseismic offsets); 3) transient processes following large subduction eartquakes. The main advantages of the proposed regression analysis algorithm are: 1) an automatic process for detecting coseismic displacements, based on direct modeling of surface deformations using a dislocation model, 2) an automatic process for identifying transient processes; 3) taking into account the realistic GNSS noise model in calculating errors.</p><p>Since most of the GNSS stations were deployed only after large 2006-2007 Simushir earthquakes their time series were affected by intense and long-term postseismic transient processes such as afterslip and viscoelastic relaxation in the upper mantle. We use our direct models of these postseismic processes to construct residual time series, which allows us to estimate magnitudes of seasonal periodic signal and to calculate realistic errors.</p><p>We use correlation-based clustering algorithm to identify the influence of block structure of island arc on observed deformation patterns during interseismic, coseismic and postseismic stages of the seismic cycle. We also check our processing of GNSS data by constructing model of slip distribution in the source of 2006 Simushir earthquake on the basis of our estimates of coseismic offsets and by comparing our model with previous ones obtained on the basis of satellite geodetic data. The performed analysis of continuous GNSS observations shows that different parts of Kuril island arc are at different stages of seismic cycle.</p>

FIELDWORKS AT ALAID VOLCANO IN 2020, ATLASOV ISLAND, THE KURILES. PHASE 2

The second phase of field work in 2020 on the Alaid Volcano, located on Atlasov Island in the north of the Kuril Island Arc, was carried out on October 2. There was no snow in the crater at the time, and this made it possible to study the deep part of the crater and take samples of rocks and snow. The measurements of the temperature of fumarole gases showed that for the tested fumaroles it varied in the range of 35° to 95° C. Rock samples were also taken from the Svechka Rock and at Cape Shtormovoy. It was found that there is currently no water in Yuryev Creek, located in the west-northwest part of Atlasov Island. The studies carried out have made it possible to obtain new unique information, which will undoubtedly be useful to various researchers of active volcanoes in the Kuril island arc.