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Nº 4 (2025)

Ano: 2025
Artigos: 6
URL: https://bakhtiniada.ru/0203-0306/issue/view/20492

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Articles

Magmatic activity of Mutnovsky volcano and crater formation at the site of blowing well 022

Kiryukhin A., Polyakov A., Sergeeva A., Nuzhdaev I., Zhuravlev N., Voronin P., Usacheva O., Puzankov M.

Resumo

Mutnovsky volcano in the last four thousand years is characterized by predominantly magmatic activity in the northern sector, where the Mutnovsky geothermal field was formed. Magmatic activity is detected by the Frac-Digger method using seismic data of KF FIC EGS RAS, the most powerful sequence of shallow dykes of NE strike is manifested at the surface by blowing geothermal wells. Dyke emplacement in March 2024 is synchronized with a hydrothermal explosion with the formation of a crater with a volume of up to 0.36 million m³ at the site of well 022 (Crater 022+). Unaltered debris from the explosion indicates lithoclastic character in the head gas-saturated part of the dyke. The base of the explosion crater is a hydrothermally altered (opal, zeolites) plane of 160×75 m². The mechanism of the hydrothermal explosion is considered as a result of hydraulic fracturing of the two-phase geothermal reservoir by a shallow dyke, with subsequent pressure increase in the shallow hydrothermal reservoir near the well with a closed wellhead valve.

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Vulkanologiâ i sejsmologiâ. 2025;(4):3-21

3-21

(Rus)

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Phase and chemical composition of high-temperature sublimates of Avachinsky volcano (Kamchatka)

Plutakhina E., Malik N., Nikolaeva I.

Resumo

This work presents results of studying sublimates (mineral phases deposited from volcanic gases) that were collected in silica glass tubes placed in high-temperature fumaroles at the Eastern fumarole field of Avachinsky volcano (Kamchatka) in 2013–2023. The concentration distributions of 62 elements along the length of the tubes (along the temperature gradient) were studied by ICP-MS and ICP-AES methods. 35 phases of sublimates corresponding to natural minerals and 7 phases of sublimates for which no natural analogues are known were diagnosed. A general mineral sequence with decreasing temperature is as follows: Na and K halides; Na, K, Ca sulfates; sulfides; X-ray amorphous As-S glass and Tl, Pb, Bi halides. The most common phases are As-S glass, SiO₂, NaCl, KCl, Na₂SO₄‒K₂SO₄; rare phases are KCdCl₃, K₂Pb(SO₄)₂, Tl(I,Cl,Br), Pb₂Tl(Cl,I,Br)₅, PbTl₃(Cl,I,Br)₅, Pb(Cl,I,Br)₂, Tl₃BiI₆, ReS₂, Pb-Zn-Cd-In sulfides and AgI.

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Vulkanologiâ i sejsmologiâ. 2025;(4):22-41

22-41

(Rus)

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Pliocene-Quaternary Volcanism in the Interfluve of the Kozyrevka and Malaya Romanovka Rivers (Sredinny Range of Kamchatka): Age and Composition of the Rocks

Pevzner M., Tolstykh M., Lebedev V., Babansky A.

Resumo

The isotopic K–Ar age of volcanoes in interfluve of the Kozyrevka and Malaya Romanovka rivers in the Sredinny Range of Kamchatka has been established for the first time. Six stages of activation have been identified: the termination of the Miocene (5.8–5.5 Ma), the Early Pliocene (4.9–4.5 Ma), the Middle Eopleistocene (1.5–1.4 Ma), the Late Eopleistocene (1.1–1.0 Ma), the Middle Pleistocene (0.4–0.3 Ma). No more recent volcanic activity has been recorded in the area. It has been established that the beginning of Quaternary volcanic activity was preceded by a period of rest lasting about 3 million years. It has been established for the first time that the formation of a large fault of the upper strike occurred at the northern foot of the Romanovka volcano no earlier than 0.4–0.3 million years ago. The analysis of K–Ar isotopic dates allowed us to suggest that the activation stages of Quaternary volcanic activity at ~1.5 and ~0.3 Ma had a regional character. The regional activity is less clearly traced for the stages of ~1.0 and ~0.6 Ma. Over the last six Ma, rocks ranging from basalts to dacites have erupted in the interfluve. It was found that extensive covers and large lava structures are composed of rocks of medium and acidic composition, while basalts are confined to small monogenic centers. In general, the studied volcanics are chemically similar to the Late Miocene-Quaternary rocks of the southern part of the Sredinny Range. The results of our work fundamentally change the previously existing estimates of the age of volcanoes in the studied area of the Sredinny Range. It is suggested that there were no significant glaciations in the interfluve of Kozyrevka and Malaya Romanovka at least in the Quaternary.

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Vulkanologiâ i sejsmologiâ. 2025;(4):42-59

42-59

(Rus)

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TTEPHRA FROM LACUSTRINE SEDIMENTS OF THE MAGADAN REGION

Minyuk P., Pozhidaeva D., Sotskaya O., Burnatny S., Lozhkin A., Anderson P., Malakhova G.

Resumo

Tephra of two generations is found in the sediments of numerous lakes located on the territory from the coast of the Sea of Okhotsk in the south to the basin of the Indigirka River in the north. Tephra of different ages are distinguished in its distribution area, rock magnetic, geochemical, mineralogical, and thermomagnetic characteristics, which makes it possible to diagnose it in sections. The accumulation of lower tephra is associated with the eruption that formed the Kuril Lake caldera in Kamchatka about 7 600 years ago. It is found in all lakes where sedimentation took place at that time. The nature of tephra occurrence was controlled by the distance from the source, morphological and hydrodynamic parameters of the lakes, and post sedimentation processes. Tephra has a rhyolitic composition with a silica content of 75.6–75.9%, weakly magnetic. Magnetic particles are predominantly pseudodomain. It is dominated by titanomagnetites with average titanium contents in the range of 3.6–6.5 wt. %. The distribution of upper tephra is limited to the area of the Northern Okhotsk region. It is highly magnetic, dominated by low-titanium titanomagnetites (Ti = 2.6 – 3.2 wt. %). The size of magnetic particles is pseudodomain-multi-domain (closer to multi-domain). The magnetic susceptibility of the tephra interlayers, which is an order of magnitude higher than the magnetic susceptibility of the lake sediments, is its main distinguishing feature. Tephra has a rhyodacite composition with a silica content of 70.2‒70.5%. It is about 3 000 years old. Tephra layers in lake sediments are important chronological and correlation markers of the Holocene.

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Vulkanologiâ i sejsmologiâ. 2025;(4):60-83

60-83

(Rus)

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Gabbro of the Esmeralda underwater volcano(Mariana Island Arc)

Fedorov P., Rashidov V., Ananyev V.

Resumo

The mineralogical and petrochemical compositions of gabbro from the Esmeralda underwater volcano, located in the southern part of the Mariana Island Arc, dredged during the 4^th and 5^th cruises of the research vessel “Vulcanologist”, were studied. It has been established that gabbros belonging to the tholeiitic series are highly fractionated rocks, in contrast to the dredged gabbroids in the basins of the southern part of the Mariana Island Arc system. It is shown that gabbro is characterized by elevated iron content. The elevated iron content of rocks is confirmed by high iron content in pyroxenes and plagioclases, which allows us to classify the bulk of dredged gabbro as an association of Island Arc ferruginous tholeiites. Low concentrations of highly charged and heavy rare earth elements relative to the composition of MORB, as well as their interelement ratios, suggest the formation of primary melts from a depleted mantle source. The enrichment of gabbro with large-ion lithophile elements indicates the participation in magmogenesis of not only high-temperature sedimentary melt, but also the significant role of a low-temperature fluid component.

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Vulkanologiâ i sejsmologiâ. 2025;(4):84-100

84-100

(Rus)

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Upgrading the Sensitivity of the Seismological Network in the Lena River Delta Area

Ponasenko S., Dergach P., Duchkov A.

Resumo

This work is devoted to the study and improvement of the quality parameters of the obtained data of the seismological network in the western area of the Lena River Delta. The sensitivity and azimuth gap between neighboring stations, also known as the “azimuthal gap”, were chosen as the main metrics to be evaluated. When evaluating scenarios for the placement of network points, an area was selected in which the average sensitivity values were estimated as the highest priority metric and azimuth gap. The planning of the placement of points was carried out in order to optimize the sensitivity of the network, ensuring, if possible, an average value of the azimuth gap in the selected area of less than 180°. As a result of the assessment of the current arrangement, it was decided to dismantle the “SML09” point and move the equipment to a more promising location. In addition, a scenario was proposed for the installation of additional stations, in which the average sensitivity in the studied area increases by 0.49, which, according to the Gutenberg–Richter law, should lead to an increase in the number of earthquakes by 2.08 times.

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Vulkanologiâ i sejsmologiâ. 2025;(4):101-112

101-112

(Rus)

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