Analysis of the magnetometer response to the passage of seismic wave     

S. S. Starzhinskii  V. M. Nikiforov 《Izvestiya Physics of the Solid Earth》2010,46(2):154-164

Results of synchronous recording magnetic variations and seismic vibrations caused by an earthquake with a magnitude M = 6.7 at a distance of 806 km from the observation site are considered. Measurements are carried out at the VLA observatory. Different patterns of seismic noise generation and their contributions to the magnetic variations recorded by torsion magnetometer are analyzed. As well, the correlation between the seismic and magnetic components is studied. The close correlation between the seismic accelerations of rocks and the magnetic variations is revealed, and its transfer coefficient is estimated. Such correlation in other types of magnetometers is supposed to hinder the measurement of seismomagnetic signals, which will require the seismic noise parameters to be known for different types of magnetometers.  相似文献   

The Chailag-Khem fluorite-barium-strontium rare earth carbonatite occurrence, the Western Sayan Range, Russia     

A. V. Bolonin  A. V. Nikiforov  D. A. Lykhin  A. M. Sugorakova 《Geology of Ore Deposits》2009,51(1):17-32

The geological and mineralogical data on the Chailag-Khem F-Ba-Sr-REE occurrence in the Western Sayan Range, Russia, are discussed. The chemical compositions of rocks, ores, and minerals (ICP-MS, Link) are reported. The occurrence is localized in a tectonic crush zone composed of Cambrian quartz-sericite slates intruded by quartz syenite porphyry. Ore mineralization occurs as veins, cement of tectonic breccia, and metasomatic disseminations in host rocks. Massive ore consists of calcite, strontianite, and quartz; impregnations of euhedral fluorite, ankerite, and bastnaesite crystals; and fine-grained barite aggregate. Accessory minerals include parisite, synchysite, barytocelestine, sulfides, rutile, and uraninite. Late metasomatic calcite and strontianite segregations and veinlets are abundant. In genetic, mineralogical, and geochemical features, the Chailag-Khem occurrence is similar to the Late Mesozoic carbonatite deposits of Central Tuva, of which the Karasug Fe-F-Ba-Sr-REE deposit is the largest and best known. All carbonatite deposits and occurrences are located within a longitudinal zone transverse to the major tectonic elements of the region.  相似文献   

Results of electromagnetic sounding with JASC submarine cable     

S. S. Starzhinskii  V. M. Nikiforov 《Izvestiya Physics of the Solid Earth》2011,47(3):223-232

We present the results of long-term deep geoelectric studies using the JASC (Japan Sea Cable) submarine communication cable in the region of the Sea of Japan. In the 2D inversion of the amplitude and phase’s apparent resistivity curves and the frequency dependences of the tipper, we invoked the geological and geophysical information about the region and on-shore electromagnetic observations to fit the model to the observations. The resulting geoelectrical cross section of the region of the Sea of Japan along the JASC cable obtained in this way agrees well with the experimental data. The upper part of the section contains a conductive block beneath the bottom of the Central basin of the Sea of Japan at a depth of 10–40 km, a fault submerging below the continent in the marginal part and a deep fault in the continental region. In the lower portions of the cross section, the high-resistivity block interrupts the continuity of the horizontal conductive layers beneath the Yamato Uplift, and the conductive bottom part of the geoelectric cross section submerges under the continent. In the continental segment of the cross section, there is a large block with reduced electric resistivity, which is located between the conductive layers at a depth interval of 200–560 km. We analyze the characteristic features of the geoelectric cross section and the deep section imaged by seismic tomography in the region of the Sea of Japan.  相似文献   

Composition and sources of magmatism of the middle paleozoic Vilyui rift area and the problem of combination of its basic and kimberlitic derivates     

K. N. Egorov  A. I. Kiselev  V. V. Yarmolyuk  A. V. Nikiforov 《Doklady Earth Sciences》2011,436(1):76-82

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Morphogenetic classification of the Arctic coastal zone     

S. L. Nikiforov  Yu A. Pavlidis  V. Rachold  M. N. Grigoryev  F. M. Rivkin  N. V. Ivanova  M. M. Koreisha 《Geo-Marine Letters》2005,25(2-3):89-97

Arctic coastal evolution is the result of interactions between exogenic and endogenic processes. In the arctic region, this evolution differs from that in other areas of the worlds oceans as a result of interactions between modern wave and ice factors, and the influences of glaciations and large-scale sea level changes in the past. Geologic structure, origin and development determine contemporary relief morphology. Morphology appears to be the most significant relief characteristic, but it is controlled by a set of interactive processes active over long periods. Our approach, in which a multitude of interacting factors are simultaneously analyzed and determined, could be called morphogenetic. We consider marine coasts and offshore zones (shelf) as a unit, and providing a general explanation for their evolution. The classification presented here is based upon the general approach given in the Science and Implementation Plan of Arctic Coastal Dynamics (ACD), a project of the International Arctic Science Committee and the International Permafrost Association. Our classification extends beyond the morphological ACD classification to include a morphogenetic classification.  相似文献   

Improving capabilities of broadband differential satellite navigation systems via radio occultation technology     

T. O. Myslivtsev  S. V. Nikiforov  A. I. Pogoreltsev  P. V. Savochkin  I. V. Sakhno  A. A. Semenov  B. V. Troitsky 《Geomagnetism and Aeronomy》2016,56(4):457-463

The existent satellite system for radio occultation monitoring the Earth’s neutral atmosphere and ionosphere (COSMIC) provides data to consumers in the regions with limited possibilities of constructing dense measurement networks (e.g., in the World Ocean area). A forthcoming increase of LEO small spacecrafts and the deployment of new satellite radio navigation systems will result in a pronounced increase in the efficiency of radio occultation method and its space resolution. As a result, the Space-Based Augmentation Systems (SBAS) broadband differential system will become global, or the quality of corrections delivered to single-frequency consumers of individual systems, e.g., the Augmentation and Monitoring System, will be improved. Therefore, the methods for processing and analyzing obtained radio occultation data should be improved. A simple method to reconstruct the electron density profile at radio occultation points, based on the total electron content measurement on the satellite–satellite path and the IRI-type ionospheric model has been proposed. The method needs initial information, it does not require refraction measurements, and it is free of the assumption that the ionosphere is spherically stratified in the occultation region. Verification of the proposed method based on data for 121 radio occultation cases across Europe in May 2013 demonstrated good agreement with the vertical sounding data.  相似文献   

Early paleozoic age and geodynamic setting of the Botogol and Khushagol alkaline massifs in the Central Asian foldbelt     

A. V. Nikiforov  V. V. Yarmolyuk 《Doklady Earth Sciences》2007,412(1):6-10

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Isotope geochemistry (O, C, S, Sr) and Rb-Sr age of carbonatites in central Tuva     

A. V. Nikiforov  A. V. Bolonin  B. G. Pokrovsky  A. M. Sugorakova  A. V. Chugaev  D. A. Lykhin 《Geology of Ore Deposits》2006,48(4):256-276

The Rb-Sr isochron age of igneous ankerite-calcite and siderite carbonatites in central Tuva is estimated at 118 ± 9 Ma. The following ranges of initial values of O, C, Sr, and sulfide and S isotopic compositions were established: δ¹⁸O_carb = +(8.8?14.7)‰, δ¹³C_carb = ?(3.6?4.9)‰, δ¹⁸O_quartz = +(11.6?13.7)‰, δ³⁴S_pyrite = +(0.3?1.1)‰, and (⁸⁷Sr/⁸⁶Sr)_i =0.7042?0.7048 for ankerite-calcite carbonatite and δ¹⁸O_sid = +(9.2?12.4)‰, δ¹³C_sid = ?(3.9?5.9)‰, δ¹⁸O_quartz = +(11.2?11.4)‰, δ³⁴S_pyrite = ?(4.4–1.8)‰, δ³⁴S_sulfate = +(8.6?14.5)‰, and (⁸⁷Sr/⁸⁶Sr)_i = 0.7042?0.7045 for siderite carbonatite. The obtained isotopic characteristics indicate that both varieties of carbonatites are cognate and their mantle source is comparable with the sources of Late Mesozoic carbonatites in the western Transbaikal region and Mongolia. The revealed heterogeneity of isotopic compositions of carbonatites is caused by their contamination with country rocks, replacement with hydrothermal celestine, and supergene alteration.  相似文献   

Andradite–Morimotoite Garnets as Promising U–Pb Geochronometers for Dating Ultrabasic Alkaline Rocks     

E. B. Salnikova  M. V. Stifeeva  A. V. Nikiforov  V. V. Yarmolyuk  A. B. Kotov  I. V. Anisimova  A. M. Sugorakova  V. V. Vrublevskii 《Doklady Earth Sciences》2018,480(2):778-782

U–Pb geochronological studies of garnet of the andradite–morimotoite series and Sm–Nd geochronological studies of this garnet and apatite from the Chikskii Massif (Tuva-Mongolia microcontinent) were carried out. The garnet studied is characterized by relatively high concentrations of U (14–16 ppm) and by a low level of common Pb (Pb_с/Pb_t = 0.07–0.1). The concordia age of garnet is 492 ± 2 Ma (MSWD = 0.01, probability 92%) and matches within the error with the Sm–Nd age determined by the isochrone for apatite, garnet, and bulk rock (489 ± 9 Ma, MSWD = 0.86). This allows us to consider calcic garnets of the andradite–morimotoite series as promising mineral geochronometers for U–Pb dating of ultrabasic alkaline rocks.  相似文献   

Evolution of magmatic and hydrothermal activity in the western Arctic and North Atlantic regions     

N. O. Sorokhtin  L. I. Lobkovsky  G. V. Novikov  E. E. Kozlov  O. Yu. Bogdanova  S. L. Nikiforov 《Oceanology》2016,56(4):572-577

This paper discusses the geodynamic evolution of the lithosphere in the Arctic region during the Phaneorozic and its polyphase lithotectonic reorganization. Spatiotemporal patterns of the mosaic junction of lithospheric plates of different age are presented for the Caledonian–Hercynian stage and for the Cenozoic evolution of the North Atlantic and Arctic oceanic basins. Special attention is given to the intersections of fault systems with different kinematics, which control the manifestation of peculiar magmatism and the formation of numerous mineral deposits. It is shown that the hydrothermal activity of the region is related to the ocean opening in the Eocene and is confined to the mid-ocean ridge.  相似文献