South Kamchatka Research Articles

Diatoms of soils and pyroclastic deposits from South Kamchatka volcanoes

Twenty-four species of diatoms belonging to 14 genera, 12 families and 5 orders were identified from soils and pyroclastic deposits of the Gorely, Mutnovsky, Avachinsky, Koryaksky and Vilyuchinsky volcanoes (Kamchatka Peninsula, Russia). Two species of these (Nupela tenuicephala, Pinnularia bullacostae) are new to the flora of the Kamchatka Peninsula, three ones (Eunotia palatina, Neidium bergii, Stauroneis borrichii) to the Russian Far East, and another three (Psammothidium lacustre, Humidophila sceppacuerciae, Gomphonema reichardtii) to the flora of Russia. Three revealed taxa (Navicula sp., Chamaepinnularia sp., and Pinnularia sp.) are probably new to science, as their morphological and morphometric characteristics differ from those of previously described species.

Structure of the Hydrothermal System of Thermal Fields Inferred from Geological-Geophysical Modeling: A Case Study of the Kambalny Volcanic Ridge (Kamchatka)

Abstract ––Based on integrated structural and geophysical studies and generalization of geophysical, hydrogeological, mineralogical, geochemical and other data, it is shown that the southern cluster of thermal fields of the Kambalny volcanic ridge (South Kamchatka) is included in the modern hydrothermal system. New data on the structure of the steam hydrotherm discharge area investigated to a depth of about 300 m have been obtained. The structural and hydrodynamic connection between two thermal fields from this group has been established. The Kambalny Ridge geothermal system embracing all major clusters of thermal fields is assumed to have a single deep-seated source of heat supply.

НАХОДКИ ЛАМИНАРИЕВЫХ И ДРУГИХ ВОДОРОСЛЕЙ В УЛОВАХ ДОННЫМ ТРАЛОМ И ЯРУСОМ У ЗАПАДНОГО ПОБЕРЕЖЬЯ КАМЧАТКИ В 2018–2023 гг.

Data are provided on findings of marine macroalgae during bottom trawls and longline fishing on the Western Kamchatka shelf in 2018-2023. During the study period, algae were noted at 65 stations in the depth range from 20 to 350 m. Most of the algae findings were found in the Kamchatka-Kuril fishing subzone, within the South Kamchatka Nature Reserve. Among the macrophytes, representatives of the order Laminariales predominated: Agarum pertusum, A. clathratum, Alaria esculenta, Arthrothamnus bifidus, Eualaria fistulosa, Hedophyllum bongardianum, H. dentigerum, Laminaria yezoensis, Laminaria inclinatoriza and Thalassiophyllum clathrus. For southwestern Kamchatka, only 9 out of 13 species of kelp algae indicated in the literature were discovered. Brown algae Fucus distichus, Desmarestia intermedia, red algae – Ptilota asplenioides, Turnerella mertensiana and lamellar green algae – Ulva fenestrata were found sporadically. A comparative analysis of aerial photography data of coastal areas from Cape Sivuchy to Cape Lopatka in 2002 and modern satellite images did not reveal significant changes in the distribution of littoral and sublittoral algae beds. In the coastal line of capes Sivuchy, Kambalny and Maria that we studied, the kelp belt with an average width of 100-130 m reached in the summer of 2018–2023 the total coverage area is 1.92 km2. The use of accompanying data when conducting bottom surveys of commercial invertebrates and fish, longline cod fisheries, together with the analysis of satellite images, allows for an expert assessment of changes in the species composition and distribution of kelp algae, and is also a promising tool for monitoring the state of macrophyte communities in the Far Eastern seas of Russia.

Hg Mineral Forms in Argillisites of the South Kamchatka Thermal Fields, Russia

Hg Mineral Forms in Argillisites of the South Kamchatka Thermal Fields, Russia

THE RELEVANCE OF THE STUDY OF THE PRIBREZHNY VOLCANIC COMPLEX IN THE CONTEXT OF THE HISTORY INVESTIGATIONS OF SOUTH KAMCHATKA

The present paper contains a review of publications, geological maps and reports on the study of the Pribrezhny volcanic complex of South Kamchatka. The Pribrezhny volcanic complex is comprised of a number of closeset volcanic massifs stretching chain-like along the narrow coastline of the Beregovoy ridge from the Avacha Bay to the Vestnik Bay. The relevance of the work is related to the necessity of revising the geodynamic history of formation of the study area which stems from emergence of some fragmentary, contradictory information about magmatic complexes of South Kamchatka. The paper presents the data on magmatic rocks penetrated in the coastal cliffs of South Kamchatka. Consideration is being given to their formation conditions in the context of a once-popular theory of geosynclines and in that of plate tectonics. Based on the review, several open research problems are formulated concerning the undetermined propagation limits of the Pribrezhny volcanic complex and unknown time intervals of its formation, and the lack of mineralogical and isotopic-geochemical studies of magmatic rocks. A separate research problem is the formation of transitional zone between the continental margin of Kamchatka and the Kuril Island Arc. The paper shows the relevance of the study of the Pribrezhny volcanic complex of South Kamchatka and proposes possible solutions to the research problems. A detailed mapping of the junction zone of Pribrezhny volcanic complex of South Kamchatka and the Kronotsky terrain near the Malko-Petropavlovsk zone of transverse dislocations will make it possible to refine the age and kinematics of their relationship. Determination of rare elements and strontium, neodymium and lead isotopes will provide a possibility to clarify the nature of magmatism as compared to heterochronous volcanic series of South Kamchatka. The data obtained will be needed to study magmogeneration conditions for acid volcanism of South Kamchatka and monogenic volcanism of the Malko-Petropavlovsk zone of transverse dislocations. The paleomagnetic studies, along with dating of rock absolute age, will help to reconstruct the paleolatitude of formation of the Pribrezhny volcanic complex and to restore the geodynamic evolution of formation of South Kamchatka.

The Pauzhetka tephra (South Kamchatka): A key middle Pleistocene isochron for the Northwest Pacific and Okhotsk Sea sediments

The distal Pauzhetka tephra, formed by a large caldera-forming volcanic eruption in South Kamchatka, has been identified in eleven recently recovered marine sediment cores based on major and trace element compositions of tephra glass. Ten SO264 cores form a transect along the Emperor Seamount Chain (ESC) in the Northwest (NW) Pacific between ∼50.3° and ∼45°N, 800–1200 km southeast of the Pauzhetka caldera. One additional core LV28-41-4 was retrieved in the Okhotsk Sea, ∼600 km west of the caldera. The Pauzhetka tephra glass shards have a characteristic medium-K rhyolite composition and trace element content compatible with the rear-arc position of the source volcano that ensures their identification. In the NW Pacific SO264 cores, the tephra is preserved as layers in cores 33, 47, 49, 53, 55, 56 and 62, as a lens in core 45, and as cryptotephra in cores 57 and 66. It forms a cryptotephra in the Okhotsk Sea core LV28-41-4. Distinctively high XRF-retrieved K/Ti and K/Fe ratios compared to those for the host sediments help identify the Pauzhetka tephra. According to our refined stable oxygen isotope (δ18O)- and magneto-stratigraphy of two studied and two reference cores, the Pauzhetka tephra occurs within a local δ18O maximum during a transition from marine isotope stage 12 to 11c (Termination V) and below a paleointensity minimum referred to as the Bermuda excursion, at ca. 418 ka. Using the tephra age as an isochron, we show that average linear sedimentation rates decrease southward along a transect of the SO264 cores, except in core 55. It partially reflects an intensification of mid-depth currents causing winnowing, erosion or non-deposition along the ESC over the past 418 kyr. An increased linear sedimentation rate in core 55, recovered from the southern leeward side of the Minnetonka Seamount, appears to record the pelagic accumulation protected from the mid-depth current influence. Our findings expand the former ash dispersal area farther southeast in the NW Pacific and southwest in the Okhotsk Sea. The new data on the tephra thickness supports the axis direction of the fallout zone southeast of the Pauzhetka caldera. Our results suggest the Pauzhetka tephra as a key middle Pleistocene isochron for the stratigraphy and correlation of the NW Pacific and Okhotsk Sea sediments.

Transition from the Continental Margin of Kamchatka to the Island Arc of the Kurile Islands: Features of Volcanism, Crustal Deformation and Geophysical Parameters of the Slab

Abstract—Magmatism manifestations in the transition zone from the continental margin of Kamchatka to the Kurile island arc and some geophysical parameters of the subducted oceanic plate of the Northwestern Pacific are considered. The presence of the Miocene coastal volcanic (Pribrezhny) complex at the base of the South Kamchatka volcanic belt contributes to intense crustal processes causing caldera-forming eruptions in the Holocene. The Northern Kuriles are characterized by initiation of areal volcanism associated with crustal fault zones. Anomalous is the absence of volcanism on Shumshu Island proximal to Kamchatka. Seismic tomography data reveal a high seismic velocity anomaly below it, which can explain this phenomenon. Based on the presented data an assumption is made about existence of a seafloor elevation on the slab, whose submergence led to disintegration of the melting regions responsible for generation of volcanism.

The Boundary Areas Structure of the Malko-Petropavlovsk Fracture Zone from Local Seismic Tomography and Earthquake Foci Mechanisms Data

Abstract —This study continues analysis of the new seismic tomographic structure of the suprasubduction complex of the central zone of Kamchatka, obtained from the dense local networks data of 2018–2020, and is devoted to the analysis of the velocity structure in the Malko-Petropavlovsk fracture zone margins and around them. The seismic tomographic model involves about 98,000 P- and S-wave travel times from 2963 local earthquakes from August 2018 to July 2020. The resolution of this model makes it possible to trace the feeding systems of volcanoes of the South Kamchatka and East Volcanic Belt to the slab surface, as well as to identify subvertical structural faults. To construct the orientations of the compression and extension axes we used the foci mechanisms of 41 earthquakes with М ≥ 4.5 from the catalog of the International Seismological Center for the period 1979–2019. Along the Malko-Petropavlovsk fracture zone, the Avacha transform fault is clearly traced in the geometry and mutual arrangement of velocity anomalies almost throughout the entire depth of the model. Comparison of seismic anomalies with a map of the directions of the compression and extension axes distribution from the earthquake foci mechanisms showed the correlation between the change in the value of the velocity anomalies along the Avacha transform fault with the axes direction change by almost 180°. A near-surface low-velocity anomaly to the depths of 25–35 km was found along the western border of the Malko-Petropavlovsk zone under the southern tip of the Sredinny Ridge. This anomaly probably marks the axes junction zone boundary of the ancient volcanic front along the Sredinny Ridge and the modern active Eastern Volcanic Belt, which formed as a result of the Kronotsky paleoarc accretion. To the west from the Sredinny Ridge southern tip, another low-velocity anomaly was revealed. This anomaly was traced to a depth of ~150 km, has a contrasting southern boundary confirmed by the distribution of the compression and extension axes directions by the earthquake foci mechanisms and apparently marks the southern boundary of the West Kamchatka block.

Peculiarities of the Magnetic Field of Geothermal Systems of the Pauzhetsky Area (South Kamchatka)

Based on many years of research, maps of magnetic field anomalies ΔTa for large geothermal systems of the Pauzhetsky region of South Kamchatka were constructed. Magnetic fields have both general characteristics and individual features for each research object. In the area of Nizhne-Koshelevsky steam-dominated geothermal field identified a system of linear negative magnetic field anomalies, confined to thermal controlling discontinuous tectonic disturbances. Pauzhetsky geothermal field is characterized by a heterogeneous structure of the anomalous magnetic field ΔTa: NW region is marked by a quiet weakly negative magnetic field, indicating the predominance in this part of the field lateral spreading of hydrotherms from the upper aquifer; SE – a large number of alternating magnetic anomalies of high intensity, confined to subvolcanic bodies of acidic to moderate composition. The South Kambalnaya group of thermal fields is characterized by a lower magnetic induction modulus T as compared to the Pauzhetsky and Lower Koshelevsky geothermal fields, indicating a more intense alteration of the Kambalnaya Ridge rocks by hydrothermal-metasomatic processes, apparently as a result of long-term exposure to convective heat flow.

Mosses of the South Kamchatka Nature Park (Russian Far East)

Mosses of the South Kamchatka Nature Park (Russian Far East)

Mineralogy of the ores on the southern flank of the Mutnovskoe gold-silver-polymetallic deposit (Southern Kamchatka)

The Mutnovskoe deposit is one of the largest and most prospective ore deposits in South Kamchatka. The northern and southern flanks within the main veining zone Opredelyayushchaya, composed of low-sulfi (goldsilver) and sulfide-polymetallic (gold-silver-polymetallic) types of ores, respectively, are distinguished. The paper presents the results of the complex mineralogical and geochemical studies of the gold-silver-polymetallic ores of the southern flank of the deposit. Features of textures and structures, mineral, chemical compositions and genesis of the ores, as well forms of precious and base metals occurrences are shown. Typomorphic features of pyrite, sphalerite, galena, chalcopyrite, tennantite-tetrahedrite, Au, Ag, Pb and Bi tellurides, native gold, Bi, Se and Ag sulfosalts are characterized. The pyrite-sphaleritequartz, sphalerite-galena-quartz, and chalcopyrite-tennantite-tetrahedrite mineral associations are distinguished. The temperatures and composition of ore-forming solutions are shown.

Three-Dimensional Image of Crustal Density Model: A Case Study in South Kamchatka

Abstract —The methodology for building a 3D density model of the Earth’s crust and upper mantle for a crustal block in the South Kamchatka Peninsula is presented. The model is derived from the interpretation of the Bouguer anomaly values and data obtained by deep seismic soundings and electrical prospecting methods. 3D image creation can be viewed as a several phase procedure. At the first step, the area of interest is investigated through a network of intersecting profiles utilized for subsequent modeling depth density sections using the parameter scanning procedure. The a priori data include materials of geophysical surveys and geological, and petrophysical studies as well as results of depth estimation at singular points by the Euler deconvolution method. The next step involves formation of a 3D density matrix from the cross-section models. Coordinates in the cross-section planes are defined in the square grid nodes and converted to plane rectangular coordinates (the SK-42 reference system). A file of the cross-sectional database of density values is thus produced. For area shaving a sparse network of cross-sections, an additional database is derived from grid files of densities mapped horizon-wise. This ultimately results in the creation of the unified databases. A 3D network of cubic unit cells for three-dimensional (voxel) representation of density of the geologic medium is calculated. The model of density of unit cube with edge measuring 4 km was constructed for entire investigated block of the Earth’s crust. The model was detailed by decreasing successively the unit cube edges to 2.0, 1.0, and 0.5 km. The 3D modeling results are presented as block diagrams and density isosurface maps in horizontal slices at different depths. The block diagrams show isosurfaces with densities typical of deep subsurface boundaries and structures. The isosurfaces for densities of 2.75 and 2.90 g/cm3 reflect the morphology of the roof of the crystalline basement, and the lower–upper crust boundary, respectively, while the isosurfaces of 3.20 and 3.33 g/cm3 represent feasible shape of the crust–upper mantle contact. The lower-density zone ubiquitously observed in the investigated crustal block is caused by rock destruction along the deep fault. It is identified in the model with 1 km cubic unit cell side and encompasses the feeding systems of volcanoes, namely: Sopka Asacha (Asacha Volcano), Mutnovskaya Sopka (Mutnovsky Volcano), Gorelaya Sopka (Gorely Volcano), and Vilyuchinskaya Sopka (Vilyuchansky Volcano).The model with a 0.50 km cubic unit cell side shows a 2.85 g/cm3 isosurface, which delineates a column-shaped high-density region. A higher density revealed in the block is assumed to be associated with basite intrusions. 3D density models based on cross-section modeling provide additional information for geodynamic reconstructions, allowing a rough estimation of the geometry of concealed geologic features and their volumes, and can be utilized in 3D modeling to build initial models.

Mineral Formation at the East Pauzhetka Thermal Field (South Kamchatka) as an Indication of Influence of a Deep-Seated Alkaline Fluid and an Epithermal Ore-Forming System

Abstract —A sequence of argillized rocks and hydrothermal clays of the East Pauzhetka thermal field was studied in detail by means of drilling and trenching. We have identified zones composed of unusual mineral associations; their formation conditions are considered. The structure of the base of the hydrothermal-clay mass is shown. The source rocks (brecciated andesites) of the base are altered by hydrothermal–metasomatic processes and are represented by smectite–chlorite–K-feldspar–zeolite–carbonate–siliceous aggregate with sulfides, phosphates, titanium silicates and zircon silicates, and other mineral phases, including rare metals. A conceptual geological and geochemical model for the formation of argillisites and zones with mineral associations has been plotted. It is assumed that modern mineral formation in the East Pauzhetka thermal field inherits an epithermal ore-forming system located in the influence zone of a deep-seated fluid, the derivates of which are outflowing near the surface as alkaline metal-bearing solutions of the Pauzhetka hydrothermal system.

Liverworts of the South Kamchatka Nature Park: Survival in Active Volcanism Land

Kamchatka, due to its position in hemiarctic northeast Asia on the migration pathways of taxa from Asia to America and vice versa, which has an insular geographical position and provides numerous pieces of evidence regarding current active volcanism, has a peculiar flora. The study of the liverwort flora of the southeastern part of the Kamchatka Peninsula (South Kamchatka Nature Park), which, until now, has been very poorly explored, showed high taxonomic richness and some specificity due to volcanic evidence. In total, 132 species have been recorded in this sector of the “Pacific Ring of Fire”. This number is quite high compared to other floras of hemiarctic Asia. The influence of volcanism on flora formation is prominent due to the regular renewal of substrates, the appearance of specific habitats (for example, thermal water outlets), the displacement of vegetation belts, and ashfalls leading to the presence of extended spaces free of vegetation cover and is an area that is open for invaders. The altitudinal zonality, despite the difference of 2000 m in elevation, is not clearly expressed in the flora of the liverworts: arctomontane species descend far down the altitudinal profile, reaching the Betula ermanii forests. The “plantless” uppermost belt in the mountains, commonly described in floristic studies of vascular plants, is not actually free of plants if liverwort occurrences are considered. A number of species normally occupy unusual habitats in the studied flora due to contemporary volcanism evidence, e.g., sulfur-rich substrates.

Specifics of pelagic feeding by <i>Daphnia longiremis Sars</i> in the Kurile Lake in terms of structural transformation of phytoplankton

Direct observations were used to study feeding by Daphnia longiremis Sars in the Kurile Lake (South Kamchatka) in terms of structural transformation of phytoplankton in 2008. Spectrum of the daphnia’s food reflects transformations in phytoplankton species structure. Daphnia’s consumption intensity of phytoplankton, where 99.8% were diatom cells, depends on the phytoplankton biomass. It is suggested, that daphnias meet deficient in food when the values of the phytoplankton (plankton diatoms) biomass are less than 48 mgС/m3 and no compensation of plankton bacteria or detritus.

Cyanobacteria and algae biodiversity of grounds and soils from south Kamchatka volcanoes

Cyanobacteria and algae biodiversity of grounds and soils from south Kamchatka volcanoes

The Goals and Features of Monitoring of Ecosystems: The Volcanogenic Ecosystem of the Nizhne-Koshelevsky Thermal Field, South Kamchatka

The Goals and Features of Monitoring of Ecosystems: The Volcanogenic Ecosystem of the Nizhne-Koshelevsky Thermal Field, South Kamchatka

Identification of changes in the activity of Kambalny volcano (South Kamchatka) based on correlation of seismic noise

Using experimental data obtained from the network of stations installed on Kambalny volcano in the period from July 2018 to July 2019, a set of correlation functions was obtained and its preliminary interpretation was carried out. Works aimed at quality control of the obtained cross-correlation functions have been performed. We have identified considerable variations of the frequency-amplitude characteristics of the cross-correlation functions at small times, as well as significant shifts of the derived phases in large correlation times. Such variations of the cross-correlation patterns may indicate the existence of distinct time periods with different types of seismicity, as well as strong variations of mechanical properties of rocks. In turn, this might be an evidence for the ongoing activity of the magmatic system beneath the Kambalny volcano.

The influence of hydrothermal argillization on the physical and mechanical properties of tuffaceous rocks: a case study from the Upper Pauzhetsky thermal field, Kamchatka

The development of geothermal sites for electricity production, direct utilization, or tourist destinations has increased in recent decades worldwide. Such development requires investigation of the engineering geological setting, including an assessment of the physical-mechanical properties of rocks. Geothermal regions in the Kuril-Kamchatka arc are composed of Neogene-Quaternary volcanic formations with relatively high strength and deformation properties. Thermal fluids circulating within rocks change their compositions, porosities, and physical-mechanical properties. The most intense alterations occurring in the thermal fields are due to argillization. This study investigates the effects of hydrothermal alteration on the physical-mechanical properties of tuffites in the Upper Pauzhetsky thermal field located in South Kamchatka. The aims are to consider the entire range of hydrothermal argillization and to analyze the relationships between physical-mechanical properties and degrees of alteration. The variations in mineralogy, microstructure, particle size distribution, consistency, and rock properties along the section of the thermal field are studied. The results show that argillic alteration gradually decomposes tuffites to weak clay-rich soils, forming a cover several meters thick. The alteration is accompanied by decreases in strength and rock weakening; minor variations are observed between fresh and altered tuffites, whereas a dramatic reduction in strength occurs when tuffites disintegrate and are converted into clays. The heterogeneity of the clayey layer and the presence of secondary siliceous minerals and residual components of parent rocks are the factors that distinguish hydrothermal clays from sedimentary deposits.

A model of the deep structure of the Earth’s crust and upper mantle in the area of the Karymshinsky gold-ore cluster according to geophysical data (South Kamchatka)

In the South of Kamchatka, modern geodynamic processes are actively taking place. A deep geological and geophysical model of the structure of the Earth’s crust and upper mantle along the regional profile of the Apacha Village-Mutnaya Bay in the zone of Tolmachevsky active magmatic center is presented. The profile passes near the South-Western border of the Karymshinskaya volcano-tectonic structure (VTS) and crosses the Ahomtenskaya VTS. The model created on the basis of integrated interpretation of materials of the earthquake converted-wave method (ECWM), gravity and magnetotelluric sounding (MTS). The thickness of the Earth’s crust along the profile varies from 30-33 km at the edges reaching 44-46 km, in its central part. The dominant feature of the model is a high-density formation – a block of the Earth’s crust, saturated with intrusions of the main and ultrabasic composition. The formation of the block is associated with a permeable zone between the crust and the upper mantle. In the block correlation of seismic boundaries is disturbed and in a density model the area with massive heterogeneity is allocated. A significant increase in depth to the M-Boundary in the center of the model is explained by the presence of a “bloated” transition layer between bark and mantle in this place. The thickness of the layer is about 10 km, and the density of the mantle reaches 3.4 g/cm3. It is assumed that this is a site of eklogization of breeds in a zone of paleosubduction of oceanic lithosphere under a continental. The area is favorable for the accumulation of meteor waters, which are in contact with high-temperature environment and postmagmatic solutions of intrusions, which leads to the formation of hydrothermal systems. The genetic connection of Karymshinsky gold-ore cluster with the intrusive array of medium-sour composition, allocated in the zone of the Tolmachevsky active Magmatic Center is shown.