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编号 3 (2025)
Articles
Dynamics of eruptions of Grot geyser (Valley of Geysers, Kamchatka) in 2024
摘要
The paper presents the results of visual and instrumental observations of eruptions of the Grot geyser carried out in 2024 in the Valley of Geysers (Kamchatka). It was found that the eruption regime of Grot Geyser has changed significantly: Grot Geyser has turned from an irregularly erupting geyser into a relatively regular geyser with an interval between eruptions of 10.4 hours in the winter low season, a break during the most intense flood, and subsequent resumption of geyser activity with an interval of 24 hours. The eruption volume of Grot geyser is estimated at ≈70 m3 using the chloride-tracer method.
3-11
Silver-polymetallic deposit Perevalnoye of the Ducatsky ore field (Balygychano-Sugoysky volcanic trough, North-East of Russia)
摘要
The geological, structural, mineralogical, and geochemical features of the silver polymetallic deposit Perevalnoye (Northeastern Russia) are considered for the first time. The deposit is located on the northeastern flank of the Dukat ore field in the central part of the Balygychan-Sugoysky riftogenic volcanic trough, which formed synchronously with the structures of the Okhotsk-Chukchi volcanic belt. The deposit lies on the periphery of a volcanic dome uplift and is localized in a large subvolcanic dike of Late Cretaceous porphyritic rhyolites (nevadites) at a depth of 140‒160 m from the surface. The richest mineralization is controlled by the knee-shaped bends of the dyke. The main amount of silver in the ores is mainly associated with Ag-tetrahedrite and freibergite. In addition, a significant proportion of silver is due to pyrargyrite, native silver, acanthite, and geffroite ((Ag, Cu, Fe)9(Se, S)8). A small part of the silver is associated with rare (for these ores) minerals – proustite, argentopyrite, and minerals of the lenaite (AgFeS2) – chalcopyrite isomorphic series. The main mineralogical feature of the ores is the widespread development of coarse–scaled muscovite and rutile, the presence of rhodonite, anatase, zircon and leucoxene. Siderite and rhodochrosite predominate among carbonates. A two-stage ore formation has been established for the Perevalny deposit – the telescoped superposition of high-temperature greysens (late stage) on silver-polymetallic ores (early stage) with distinct signs of thermometamorphism of the latter and the associated natural Ag enrichment. Greisenization and the influx of high-temperature solutions seem to be associated with the introduction of a late phase of an undiscovered intrusive massif. The results of mineralogical studies allow us to classify the Ag–polymetallic deposit Perevalnoye, as well as other deposits of the Omsukchan metallogenic zone, to the intermediate sulfidized class of epithermal deposits.
12-27
New data on the age of young volcanic formations in the Chegem River basin (North Caucasus, Russia)
摘要
As a result of the isotope-geochronological studies of a number of young volcanic activity objects on the northern slope of the Greater Caucasus in the upper Chegem River basin (Kabardino-Balkaria, Russia), which were attributed by the different researchers to both the Jurassic period and the late Cenozoic. Their age and position in the regional Neogene-Quaternary magmatism geochronological scale of the Elbrus neovolcanic region were determined. The stratigraphic relationships of the studied geological objects with the products of catastrophic explosive volcanism, as a result of which the large Chegem caldera was formed in the region at the end of the Neogene, were substantiated. The assignment of volcanic apparatuses active in the late Pliocene to the pre-caldera, syncaldera and post-caldera stages of magmatism was clarified. The obtained results of K–Ar dating show that at the pre-caldera stage (about 3.1 Ma) endogenous activity in the studied region was areal. During this period, a large number of small volcanic apparatuses erupted, which now have been completely destroyed and marked by dikes and stocks of rhyolites, less often trachyandesites. At the end of the Pliocene, in the period 2.9–2.8 Ma, as a result of catastrophic explosive eruptions, the Chegem caldera was formed, filled by a thick layer of ignimbrites of rhyolite-dacite composition. According to the obtained data, synchronously with the caldera formation, a series of acid extrusions and dikes composed of vitrophyres were intruded along its western, southern and eastern periphery. At the postcaldera stage (about 2.8 Ma), the Kum-Tyube and Kuygen-Kaya stratovolcanoes were active in the western part of the caldera, have been erupted lavas of dacitic and subsequently andesitic composition. It has been established that in the Quaternary, volcanic activity was absent in almost the entire territory of the upper Chegem River basin. The exception is the Aktoprak pass vicinity in the extreme northwestern part of the region, where local magmatism manifestations with increased alkalinity were recorded in the Early Pleistocene (about 1 Ma). A number of geological objects (Bashil spindle and others), the formation of which was previously attributed by some researchers to the end of the Pleistocene – Holocene, are in fact either Pliocene syncaldera extrusions or were formed as a result of exogenous processes not associated with volcanic activity.
28-61
Correlation of the aerosol lidar signal, laser strainmeter signal and rock temperature in Baksan Neutrino Observatory during earthquakes in Turkey on February 6, 2023
摘要
We report for the first time the observation of an asymmetrical behavior of the laser strainmeter signals in Baksan Neutrino Observatory (BNO, located in the Elbrus region) during two earthquakes of similar magnitude in Turkey on February 6, 2023. We have revealed a correlation between the signals of laser strainmeter, rock basement temperature in the dead-ended BNO tunnel, and the aerosol lidar signal during the second MW 7.7 earthquake at 10:24 UTC, Feb 6, 2023. The estimated crustal stress area radius is ~2000 km which is larger than the distance between the earthquake epicenter and BNO (~900 km), thus the signals of the strainmeter, thermometer and lidar can reflect stress-deformed state variations.
62-67
Shipunskoye earthquake 17.08.2024, MW = 7.0, of the east coast of Kamchatka
摘要
The article presents instrumental parameters and macroseismic data on the Shipunsky earthquake of August 17, 2024, ML = 7.0, MW = 7.0, discusses its tectonic position and features of the aftershock process, estimated based on the results of the first month of observations after the main event. The mechanisms and parameters of the Shipunsky earthquake sources and its strongest aftershocks are presented, obtained using the original method for calculating seismic moment tensors developed at the KB FRC EGS RAS. The direction of movement and the orientation of the rupture planes in the sources of these events allow us to attribute their occurrence to the subduction of the Pacific plate under the Okhotsk plate, on which Kamchatka is located. The Shipunsky earthquake did not cause casualties or damage. Its maximum macroseismic manifestation was observed at Cape Shipunskiy, 6 points on the SSI–17 scale (GOST R 57546–2017); in Petropavlovsk-Kamchatsky, the intensity of the tremors was 5–6 points. No tsunami alarm was declared, and no tsunami waves were recorded.
68-79
Assessment of tsunami hazard for the coast of the bay of Korf (Bering Sea) according to the results of numerical modeling
摘要
The paper discusses the results of solving the problem of assessing the tsunami hazard of a section of the north-eastern coast of Kamchatka in the area of the Korf village, located on a sandy spit in the northern part of the Korf bay of the same name. To obtain these estimates, the “worst case” methodology was used. Based on the results of an analysis of seismicity and historical data on tsunami manifestations in the western part of the Bering Sea, three tsunamigenic zones were identified – near-field (Bering Sea), regional (Western Aleutians) and far-filed (Southern Chile), which create the greatest tsunami threat for the study area (north-eastern coast of Kamchatka) Based on the results of the analysis of seismicity and tectonic features of the source zones, sets of model tsunamigenic earthquakes typical for each of them were determined. For this set of models, numerical modeling of tsunami generation and propagation was performed and the most dangerous model sources were identified. The maximum elevations created by these sources for the Korf village area were 1.3 m for sources in the near (Bering Sea) zone, 2.4 m for the regional (Aleutian) zone, and 2.5 m for the far (Chilean) zone. At the next stage, for these sources, more detailed calculations were carried out on sequences of nested computational grids, which determined the characteristics of the tsunami impact on the coast. The main results of the work are the identification of the most dangerous tsunamigenic zones in relation to the Korf Spit, the selection of model sources for them and assessments of extreme impacts of tsunami waves that threaten this section of the coast.
80-104