The article presents the results of an analysis of data obtained on the Yamm–Torzhok regional profile, which crosses the Ilmen anomaly of electrical conductivity along its main axis. These works continue the long-term study of the structure of the Precambrian basement complexes of the western part of the East European Platform by the staff of the Department of Geophysics of the Faculty of Geology of Moscow State University and GEMRC IPE RAS. Based on the obtained data, together with the analysis of potential fields, a deep geoelectric model was constructed, and a model of the sedimentary cover structure was presented separately.
Kuzmin I.A, Tolstykh N.D.
Sobolev Institute of Geology and Mineralogy of the Siberian Branch of the RAS, Novosibirsk, Russia;
Keywords: Talnakh intrusion, main layered series, picritic gabbro-dolerites, inverse zoning, hybrid magma.
Norilsk-type intrusions are characterized by unique reserves, disseminated copper-nickel mineralization, which is localized in picrite and taxitic gabbro-dolerites. At the same time, if picrite and taxitic gabbro-dolerites are usually genetically separated from each other, then the mechanism of formation of picrite gabbro-dolerites themselves is still under discussion. Most often, they are considered as a cumulative part of a layered series. The work shows a sharp geochemical contact between the layered series and picrite gabbro-dolerites, in the section of which, in turn, we have identified an inverse geochemical zoning, expressed in the patterns of accumulation of petrogenic elements that do not fit into a single trend of crystallization differentiation with the rocks of the main layered series. The discreteness of rocks within the horizon of picritic gabbro-dolerites is demonstrated - two intervals are distinguished: the lower one with low chromium concentrations, with stable europium and strontium anomalies, and the upper one, which is characterized by abnormally elevated Cr2O3 contents, reduced LILE concentrations and the absence of a pronounced europium maximum, typical of the lower part of picritic gabbro-dolerites. Based on the known models of formation of inverse zonality of marginal zones of layered massifs, the article presents a new genetic scheme for the formation of picritic gabbro-dolerites as products of pulsation intrusion, which suggests that the lower part of picritic gabbro-dolerites was formed from hybrid magma, and the upper one - from primitive magma, due to pulsation filling of the formation chamber, which, in our opinion, is associated with inverse zonality and accumulation of chromium in the upper part of picritic gabbro-dolerites.
V.V. Lapkovsky, M.V. Lebedev, E.A. Ianevits 1Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia
2OOO Tyumen Petroleum Research Center, Tyumen, Russia
3Branch of Lukoil-Engineering LLC "KogalymNIPIneft",Tyumen, Russia
Keywords: Stochastic modeling of structural uncertainties; probabilistic estimation of resources; estimation of seismic velocity anomalies, probability distribution of structural trap areas, lognormal distribution of structural trap areas
In the new paradigm of the Russian oil and gas industry, much attention is paid to small hydrocarbon fields. This statement increases the requirements for the accuracy of forecasts of total hydrocarbon reserves in small-scale anticlinal traps. Such forecasts can be made by probabilistic estimation of resources, taking into account the probabilities of the field existence. The objective of the present research is the development of the scientific approach to quantifying the uncertainties associated with the existence and geometric parameters of small-scale anticlinal hydrocarbon traps mapped by modern 3D seismic exploration. The main method of solving this problem is stochastic modeling of structural uncertainties based on errors of structural mapping. The results of the study are summarized as follows. The type and parameters of the probability functions of the structural area are determined by the intensity and size of the velocity anomalies, as well as the parameters of the trap itself and the nature of its structural environment. The distributions of the structural closure areas can be described by functions in which the Mean value is greater than the quantile P50 value, the Mean value is approximately equal to the P50 value, and the Mean value is less than the P50 value. The lognormal distribution, which is commonly used to model structural uncertainty, is just one of the possible options. For small-scale hydrocarbon traps, their amplitude is comparable to the thickness of a productive reservoir; therefore, a change in the amplitude of the trap determines a change in the weighted average oil-gas-saturated thickness. As a result of the modeling, a positive relationship was established between variations in the anticline traps areas and their amplitudes. Accordingly, this relationship must be taken into account during the probabilistic assessment of the resources of this kind of the hydrocarbon traps. Otherwise, there may be a significant reduction in the range of uncertainty in resource estimates. Stochastic modeling of structural uncertainties is also a method of estimating the probability of the existence of anticlinal traps mapped by seismic exploration.
A.A. Tsygankov, G.N. Burmakina
Dobretsov Geological Institute of Siberian Branch of Russian Academy of Sciences, Ulan-Ude, Russia
Keywords: Angara-Vtitm batholith, U-Pb isotopic age, Lu-Hf, sources of magma sources, geodynamics, Western Transbaikalia.
The Late Paleozoic granitoid province of Transbaikalia (Angara-Vitim batholith, AVB, Russia), located in the northeastern part of the Central Asian Orogenic Belt (CAOB), covers an area of about 200,000 km2 and is composed of rocks ranging in composition from monzonites and quartz syenites to leucocratic granites. This work is aimed at: 1) determination of the total duration and dynamics of the formation of granitoids of the Angara-Vitim batholith; 2) finding the causes that determined the spatial and temporal heterogeneity of granitoids; 3) reconstruction of the sources of salic (granitoid) magmas, assessment of the contribution of mantle-crustal interaction processes to the petrogenesis of granitoids. The article is based on new petro-geochemical, isotopic (Lu-Hf) and isotopic-geochronological (U-Pb) data on the northern part of the AVB. Combined with the results of previous studies, it has been established that one of the largest granitoid provinces on Earth (AVB) was formed ~ 45 million years ago (from 320 to 275 million years). About 90% of the batholith rocks were formed during this time. Mainly crustal metagravaccian protoliths were the source of salic magmas. Formation of monzonitoids, quartz syenites, and granodiorites is associated with melting of mixed protoliths, in which the proportion of juvenile mafic material could reach 40-50%. The Late Paleozoic granitoid magmatism of Transbaikalia began with the actual introduction of calcareous-alkaline granites, granodiorites, and quartz syenites, which make up the bulk of the first stage of magmatism. At the second stage, magmatism was concentrated in a relatively narrow (200-250 km) permeable zone of the northeastern strike. This zone drained crustal foci of salic magmas and favored the entry of mafic mantle melts into the upper horizons of the Earth's crust. The granitoids of the Angara-Vitim batholith were formed at the post-collisional stage of the evolution of the eastern segment of the CAOB under the influence of mantle plume on the crust of the young orogen.
D.V. Metelkin1,2, E.V. Vinogradov1,2, A.A. Eliseev1,2, M.E. Luzan1,2, V.V. Abashev3 1Novosibirsk State University, Novosibirsk, Russia 2Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 3Geological Institute Russian Academy of Sciences, Moscow, Russia
Keywords: Hotspots, mantle plumes, geodynamo, geomagnetic reversal frequency, paleointensity, geocentric axial dipole, equatorial dipole, anomalous geomagnetic field, global magnetic anomalies, absolute plate reconstructions
We present an analysis of modern paleomagnetic data from large igneous provinces and palaeorift structures in Siberia and the High Arctic that are potentially related to mantle plumes. The interrelationship between plume magmatism, geomagnetic reversal frequency, and field intensity over the last 600 Myr exhibits a periodicity of 70–100 Myr. Periods of mantle plume activity were preceded by an increase in geomagnetic reversal frequency, accompanied by a decrease in geomagnetic field intensity. Our proposed hypothesis explains this effect by changes in the thermal convection in the Earth’s outer core while mantle plumes are regarded as regulators of the state of the hydromagnetic dynamo. “Overheating” of the core increased the turbulence of convective currents, and therefore, the amount of reversals. During reversals, the value of the main component of the geomagnetic field – the geocentric axial dipole – first fell to zero and returned to high values only afer a full reversal of the poles. Reduction of relaxation time in periods of frequent reversals led to prolonged low values of the absolute intensity of the geomagnetic field. Mantle plumes forming during such periods could remove the excess heat and stabilize the state of the geodynamo, even almost completely stopping reversals. We link the Vendian and Devonian geomagnetic phenomena to periods of ultra-frequent reversals. During these extended periods of low value of the axial dipole, the configuration of the geomagnetic field was determined by low-order non-zonal harmonics and by the global magnetic anomalies. We observe a qualitative coincidence of the position of paleopoles with centers of lower mantle gravitational and magnetic anomalies and postulate that the anomalies were stationary. This is the basis for substantiating a new reference framework for paleotectonic reconstructions in absolute coordinates. Examples of reconstructions made using this system also agree with the hypothesis of stationary hotspots. From the terminal Precambrian to the Mesozoic inclusively, the Siberian paleocontinent was located in the area of effect of the African mantle hot field, migrating northwards along the 0° meridian from the latitude of Tristan da Cunha to that of Iceland.
V.S. Shatsky1,2,3, A.L. Ragozin1, V.N. Reutsky1, V.V. Kalinina1 1 V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, Novosibirsk, Russia 2 Novosibirsk State University, Novosibirsk, Russia 3 A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: inclusions in diamonds, diamond formation, mantle, subduction zone
Evidence of the involvement of Fe-C-O melts in diamond formation from placers in the northeastern Siberian Craton, along with our previously obtained data on iron carbide inclusions and literature sources, has provided a new perspective on processes diamond formation in subduction zones. Iron carbide and oxide inclusions in diamonds, along with the presence of moissanite and carbonates in polyphase inclusions, indicate a heterogeneous diamond environment. Extreme variations in oxygen fugacity during diamond formation processes can be caused by the generation of hydrogen and hydrocarbons during the interaction of carbonated rocks of the subducting oceanic lithospheric plate with aqueous fluids. Separated hydrocarbon fluids can create local areas of ultra-reduced mantle, where silicon carbide can be formed under conditions of the absence of equilibrium with the surrounding rocks.. A characteristic feature of the diamonds studied is that they were subjected to brittle deformation, followed by crack healing, accompanied by the formation of polyphase inclusions of iron carbides and oxides, which we interpret as melt inclusions. Brittle deformations of diamonds, in the conditions of the lower lithosphere, are explained by high deformation rates, which can be realized in the hypocenters of deep-focus earthquakes of the subducting lithospheric plate, during dehydration processes or the formation of carbonatite melts.
A.N. Didenko1,2, M.Y. Nosyrev2, G.Z. Gilmanova2, M.D. Khutorskoy1 1Geological Institute of the Russian Academy of Sciences Moscow, Russia 2Institute of Tectonics and Geophysics FEB RAS Khabarovsk, Russia
Keywords: Amur Plate, Curie Point Depth, plate boundaries, thermal anomalies and tectonic structures
Based on the results of spectral analysis of the anomalous magnetic field, the depths of the roof and the sole of the magnetically active layer of the Amur Plate and adjacent territories are calculated. The causes of variations in the depth of the sole of the magnetoactive layer (CPD) from 14 to 38 km (average 24 km) have been determined. Maximum CPD depths are observed within sedimentary basins (Erlian, Songliao, Sredneamursky) in the southwest and in the central part of the plate. The areas of minimum depths in the continental part are located in the northwest within the giant granitoid batholiths (Angara-Vitim, Khentei) and in the northeast within the Bureinsky province. The third area of minimum CPD values is located within the waters of the Sea of Japan.
The relatively high elevation of the bottom of the magnetically active layer in the Sea of Japan is associated with rifting processes in the back-arc basin, which began at the end of the Oligocene, and the generation of fluids and magma chambers above the Pacific slab, sinking under the Amur Plate. Two areas of high CPD standing in the continental part of the plate are associated with the presence of two thermal anomalies. The north-western one is explained by the presence of a thermal crustal anomaly due to the process of radioactive heat generation by granitoids of the giant Angara-Vitim, Khangai and Khentei batholiths. Northeastern Bureinskaya – the presence of an anomalous temperature of the mantle here.
A comparison of the newly constructed CPD map with the boundaries of the Amur Plate, previously determined mainly from seismic data, shows that the surface boundaries of the plate coincide mainly with the zones of the greatest CPD gradients. All of them are associated with areas of increased seismic energy generation, with the exception of one small area on the southern border of the Amur Plate at its junction with the Yangtze Plate. In our interpretation, plate boundaries are not just lines on the surface, they are fairly wide zones from tens to the first hundreds of kilometers that encircle the plate.
I.S. Sotnich1, E.A. Kostyreva1 1Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, Novosibirsk, Russia
Keywords: organic matter, bitumoids, hydrocarbon biomarkers, pyrolysis, catagenesis, maturity, Bazhenov Formation, Western Siberia.
The article presents the results of detailed organic geochemistry studies being part of a comprehensive (lithological, geochemical, petrophysical) study of the Bazhenov Formation in the Tomsk Region using the IPGG SBRAS methodology for organic matter-rich source rock. As the thermal maturity increases from PK3 to MK2, the content of 'free micro oil' in source rock's pore spaces has been observed to increase. In the same time, there are modifications to the composition of bitumoids (chloroform source rock extracts) from open and closed pores at both the group and molecular levels. Even 'immature' organic matter has been establish to show a difference in bitumoids composition from open and closed pores, which increases as it enters the main phase of oil formation.
D.V. Epishkin1,2, N.I. Zorin3, G.R. Muradyan4, A.G. Yakovlev4 1Geoelectromagnetic Research Center, Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences, Troitsk, Russia, 2STC Nord-West, Moscow, Russia, 3Center of Geophysics, Harbin Institute of Technology, Harbin, China, 4Department of Geology, Lomonosov Moscow State University, Moscow, Russia
Keywords: airborne electromagnetics, VLF-EM, RMT, UAV.
The practical feasibility of high-precision measurements of magnetic fields from remote radio transmitters in motion, including on unmanned aerial vehicles, has been demonstrated. The method is based on measuring the Euclidean norm of the full complex magnetic field vector, which makes the results independent of the sensor system's orientation. To compensate for instabilities in the primary field, normalization is performed using a synchronized signal from a stationary base station. Additional accuracy is ensured through pre-flight sensor calibration and post-processing with spatial smoothing filters. Field tests confirmed good reproducibility, with discrepancies between repeated passes below 0.5% of the signal level. In addition, magnetic field maps obtained at different altitudes show strong internal consistency and correlate well with archived ground-based inductive electromagnetic survey data.
S.M. Zhmodik, E.V. Lazareva, V.A. Ponomarchuk, A.V. Tolstov, E.V. Airiyants, V.V. Sharygin, B.Yu. Saryg-ool, D.K. Belyanin, K.A. Musiyachenko, N.S. Karmanov
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Tomtor massif of alkaline rocks and carbonatites, carbonatite breccias, carbonates, pyrochlore-group minerals, REE-fluorocarbonates, C and O isotopes
Carbonatite breccias (CBs) were discovered in the Tomtor Massif (Complex) (TM), which hosts the largest REE-Nb-Sc-Y ore deposit, by holl G2 in the northern Buranny area. CBs are petrographically complex rocks consisting of fragments of dolomite, dolomite-ankerite, ankerite and calcite carbonatites with significant contents of F-REE carbonates, pyrite, and fluorite. CBs show signs of fragmentation of carbonatites and calcite rocks, as well as the movement of these fragments by younger melt-brine enriched in CO2, F, S, and REE, and its interaction with the fragments. The studied rocks are classified as magmatic-fluidogenic and fluidogenic breccias, which provide a unique source of information on the rock composition and processes occurring at deep levels of the TM. The distribution pattern of trace elements in the KB, presented in spider diagrams, largely corresponds to the distribution of these elements in carbonatites and uniquely rich Nb-REE ores of the upper ore horizon of the TK. Spider diagrams reveal enrichment in Th, Nb, La, Ce, and Nd and depletion in U, K, Sr, Zr, Hf, and Ti, as in other carbonatite complexes of the world (including those with breccias). The REE distribution shows enrichment in MREE and HREE. The formation of the KB is accompanied by the crystallization of REE minerals with a composition unique to the TK, primarily synchysite-(Ce), parisite-(Ce) and/or bastnaesite-(Ce), cebaite-(Ce), and burbankite. Crystallization of REE-fluorcarbonates is associated with the process of dolomite replacement by ankerite, on the one hand, and the maximum amount of these minerals, as well as cebaite-(Ce) and burbankite, is recorded in calcite rocks in association with fluorite and pyrite, on the other hand. It is shown that the position of the δ18O and δ13C‰ composition points in KB fragments and in the interfragmentary space form a dependence with a high correlation coefficient value, close to the trend characterizing the process of mixing of C and O isotopes of carbonatites and sedimentary carbonates. However, this conclusion contradicts the data on high contents of REE, Nb. P and other elements typomorphic for carbonatites with increasing δ18O and δ13C‰ values and is a result of the transformation of carbonates by a low-temperature deuteric fluid. For the first time, the obtained comprehensive data on KB allow us to consider these formations as a new type of mineralization for TK.
Y.V. Kiselnikov1, E.N. Perova2, V.F. Proskurnin1, А.G. Shneider1 1Karpinsky geological research Institute, Saint Petersburg, Russia
2Saint Petersburg State University, Saint Petersburg, Russia
Keywords: Central Taimyr accretionary belt, Borzova river gold ore cluster, contact metamorphism, spessartine, mineral geothermometry, K-Ar geochronology
The metamorphic rocks in the North Eastern Taimyr region represent a consequential result of its complex geological history. Series of metamorphic processes were associated with the formation of lode copper and noble metals mineralization. The aim of this study is to investigate the type and degree of metamorphism experienced by the host basic volcanic rocks in the ore cluster. We have identified three stages of metamorphic process: the first stage led to formation of actinolite and sodium plagioclase paragenesis (with its chemical compositions corresponding to temperature about 400 °С) the second stage resulted in crystallization of hornblende, plagioclase, spessartine-almandine garnet, biotite, feldspars (oligoclase-andesine and K-Ba types) and various Fe-Ti phases (mineral geothermometers indicate the highest temperature range of 450-600 °С) and the final stage produced clinochlore, pyrite and fluorapatite (330-290°С with AlIV contents in chlorite). We interpret the studied rocks as hornfels on the basis of highly discordant contours of the aureole, the compositions of the garnet (spessartine is predominant component), and K-Ar ages of biotite (253 ± 5 Ma) and plagioclase (239 ± 8 Ma), which coincide with the time of Late Paleozoic-Mesozoic post-collisional granitoid magmatism. The absence of schistosity, disequilibrium assemblages, and abundance of volatile-rich minerals (containing F-, [OH]- and [SO4]2-) also indicate their contact origin. The discovered aureole includes the known Cu-Au-Ag veins and metasomatic occurrences, the age of which is therefore late- or post-metamorphic. We confirm our colleagues’ early suggested hypothesis about the impact of a hidden granitic massif on the host rocks and consider the high metamorphic grade to be a natural boundary for the ore cluster.
A. B. Vrevsky, A. B. Kuznetsov, A.V. Yurchenko
Institute of Precambrian geology and geochronology, Russian Academy of Sciences, St-Petersburg, Russia
Keywords: Fennoscandian shield, Paleoproterozoic, Inari Terrane, Kaskama Formation, komatiite-tholeiite association, Sm-Nd systematics
This paper deals with new geological, mineralogical, geochemical (major, trace, and rare earth elements) and Sm-Nd isotopic data for the unique Kalevian (1923-1926 Ma) komatiite-tholeiite association for the first time identified in the supracrustal Kaskama Formation from the Inari Terrane of the Kola-Norwegian region Fennoscandian shield.
In the massive and porphyritic komatiites, the primary (magmatic) mineral paragenesis represented by olivine 20-40%, orthopyroxene up to 5%, hornblende up to 10%, clinopyroxene 20-40% and plagioclase 20-30% was identified.
Relic igneous minerals (olivine, pyroxene) make it possible to estimate (COMAGMAT3.73 program) their liquidus temperatures in the range of 1500-1200 °С.
The komatiites of the Kaskama Formation belong to the Al-nondepleted type and are characterized by a low level of REEN content (1-2 relative to C1 chondrite), their total concentration (∑REE = 0.15-0.36 ppm) and an unfractionated distribution of REEs, which is a consequence of the generation and evolution of their primary melts outside the field of thermodynamic conditions of garnet stability.
The Zr–Y–Nb and Sm-Nd isotopic systematics of the rocks of the komatiite-tholeiitic association indicates the origin of their high-temperature primary melts from the plume source in depleted mantle (εNdT=+3.2±0.3), which is different from the mantle sources of the Jatulian-Ludicovian picrite-komatiite association of the Central-Lapland greenstone belt of Finland and the Pechenga intracratonic structure.
Considering the amphibolite facies metamorphic conditions of the Kaskama formation, it can be assumed that the komatiite-tholeiitic association is a deeply eroded (at least 10 km) section of the upper crustal volcanic apparatus.
A.N. Glukhov, E.E Kolova, R.V. Solovov, M.A. Tanchenko
North-East Interdisciplinary Scientific Research Institute of Far East Branch of the Russian Academy of Sciences, Magadan, Russia
Keywords: monzonite, sienite, chemical composition, geodynamic, U-Pb age, magmatic zone, orogenic belt, volcanic belt.
Undertaked analysis of composition of the monzonite-sienite intrusive rocks, is abundant in the area of Bilikano-Khulamrinskaya magmatic zone of Central segment of the Yana-Kolyma orogenic belt. That rocks compose of small intrusions, which cut of terrigenous strata of Inyali-Debin turbidite terrane. That contained medium quantity of silica and Al2O3, relatively high – K2O, Na2O, MgO and chemically similar with latite. By chemistry that very close to alkaline felsic intrusive rocks of Aldan magmatic province. Balance concentrations of chemical elements, pointed out to belonging this rocks, to granitoids of convergent continental margin, include syncollision volcanic arcs. Age of that, by U‒Pb zircone dating (SIMS) 84 Ma, coincide with secondary impulse of magmatic activity of the Okhotsk-Chukotka Volcanic belt. Specific chemical composition of monzonite rocks of the Bilikano-Khulamrinskaya magmatic zone, close to shoshonite and latite, determined by location far in rear volcanic belt, at 200 km from axis zone of that, on the sialic basement, presented by turbidite sedimentary rocks.
P.S. Martyshko, D.D. Byzov, N.V. Fedorova
Institute of Geophysics, Ural Branch of the Russian Academy of Sciences
Keywords: Gravitational and magnetic anomalies, inverse problems, Kraka massif
The paper describes methods for three-dimensional interpretation of gravity and magnetic anomalies taking into account the relief of the earth's surface. Parallel algorithms for solving direct problems of gravimetry and magnetometry (calculating field values from sources) are implemented in software for personal computers with graphic accelerators. Based on these algorithms, methods for solving inverse problems on correctness sets have been developed. When modeling, anomaly sources of arbitrary shape are approximated by a dense regular grid, the elements of which are parallelepipeds. Methods for identifying anomalies and localizing sources in the earth's crust, calculating their physical parameters have been applied in modeling the structure of the Kraka ultramafic massifs in the Southern Urals with an area of 50x80 km2. The height of the mountain ranges in this
area reaches 1043 m, and the difference in relief heights is more than 500 m.
1 VIRG-Rudgeofizika Ltd., St. Petersburg, Russia
Keywords: induced polarization, mechanisms and models of rock polarization, stationary polarizability, interphase electrical potential
Unique relationships between the parameters of induced polarization (IP) and the structure of interphase and pore space of rocks provide high interest to applied science — ensures continuous expansion of the scope of the method. The physico-chemical theory of the phenomenon of IP rocks has gaps. This is due to the complex nature of the processes that occur in rocks and produced secondary electric fields. Laboratory studies continue to be the main source of new knowledge about the mechanisms and processes occurring in rocks when an electric field is applied. In recent decades, several new hypotheses, models, and mechanisms of IP for rocks with electron-conducting mineral (EM) inclusions have been proposed. The paper describes the key features of IP mechanisms. These mechanisms are actively discussed and used to interpret IP data collected in the laboratory and field. This paper presents the results of an experimental laboratory study on the IP of interface "shungite-porous moisture", conducted on a synthetic model of rock with EM inclusions. Based on voltametric measurements, we have identified the main characteristics of shungite's polarization in an aqueous NaCl solution. An estimate is given of the magnitude of exchange currents, the dynamics of polarization at the interphase boundary at different current densities, and the relaxation of the surface electric potential. For the first time, we present measurements of electric currents flowing in the model and within the shungite inclusion - the IP currents. It has been proven that the relaxation of the electric field in the model and the IP currents have identical dependencies. The proportionality between the polarization magnitude of shungite inclusions and the normal current component on the interface between shungite and moisture has been experimentally verified. The data obtained and published suggest that the mechanism of electrode polarization of EM inclusions in rocks plays a significant role. A probable mechanism for polarization of the interphase "EM-pore moisture" in rocks has been presented.
A.Yu. Gladenkov1, A.Yu. Kazansky1 1 Geological Institute of Russian Academy of Sciences, Moscow, Russia
Keywords: Oligocene, diatoms, West Kamchatka, magnetostratigraphy, age of diatom datum levels
Results on the age estimates of the Paleogene diatom datums derived from the magnetostratigraphy at marine Cenozoic stratigraphic section of the Kvachina Bay, West Kamchatka, are presented. Based on a direct correlation with the Geomagnetic Polarity Scale, it was possible to determine the age of such levels between Subchron C13r (35.10 - 33.73 Ma) and Subchron C9r (27.86 – 27.44 Ma). Of greatest interest are the age dating of the first and last occurrences of Lisitzinia ornata (27.71 Ma and 27.54 Ma respectively), and the first occurrence of Rocella gelida (27.49 Ma). This is the first experience of absolute age estimates of Oligocene diatom biohorizons based on magnetostratigraphy not only in Kamchatka sections, but in the North Pacific region in general. The obtained age estimates of diatom datum levels are compared with the published estimates from the literature on deep-sea cores in various regions of the World Ocean.
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