Age and composition of ophiloites from the basement of the West Siberian petroliferous megabasin     

K. S. Ivanov  Yu. N. Fedorov  E. O. Amon  Yu. V. Erokhin  G. N. Borozdina 《Doklady Earth Sciences》2007,413(2):415-419

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Nature of the Ural platinum belt and its chromite-platinum metal deposits     

K. S. Ivanov  Yu. A. Volchenko  V. A. Koroteev 《Doklady Earth Sciences》2007,417(2):1304-1307

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Intraannual dissimilarities between monthly mean Northern Hemisphere temperature anomalies during the twentieth century     

S. Evtimov  M. Ivanov 《Theoretical and Applied Climatology》2007,90(3-4):161-168

Summary Northern Hemisphere monthly mean temperature anomalies during the twentieth century exhibit seasonal differences. To expose the most significant intermonthly dissimilarities, here we investigate this issue in more details. We show that the trends significantly differ for the months close to the equinoxes. Using the technique of multidimensional scaling analysis we find that two underlying attributes are sufficient to acceptably describe the structure of the observed intermonthly dissimilarities. Namely, these are the monthly sample percentiles around the 30th and the 70th together with the linear trends. We find that intraannual temperature anomaly dissimilarities statistically depend on the seasonal cycles of the Northern Hemisphere oceanic heat content, sea ice and snow cover and the Arctic sea ice cover as well as on the seasonality of the chaoticity of the Northern Hemisphere atmospheric dynamics. We also speculate that the annual cycles of these ocean and cryosphere characteristics statistically set the pattern for the observed course of linear warming over the calendar months.  相似文献   

Breakup and early seafloor spreading between India and Antarctica   总被引：2，自引：0，他引：2  

Carmen Gaina  R. Dietmar Müller  Belinda Brown  Takemi Ishihara  Sergey Ivanov 《Geophysical Journal International》2007,170(1):151-169

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Atlas of Channel Deformations in the Lower Volga     

V. V. Ivanov  V. N. Korotaev  N. A. Rimskii-Korsakov  A. V. Chernov 《Water Resources》2006,33(5):535-542

A methodology for compiling the electronic “Atlas of Channel Deformations in the Lower Volga,” its contents, and the materials used for its compilation are described. Analysis of published data and field observations made by the authors is used to examine long-term variations in channel deformations in the period of 1914–2001 and to forecast the development of the channel in the Lower Volga in the 21st century.  相似文献   

Variations of Solar Irradiance, 10.7 cm Radio Flux, He I 10830 Å Equivalent Width, and Global Magnetic Field Intensity and Their Relation to Large-Scale Solar Magnetic Field Structure     

E. V. Ivanov  V. N. Obridko  I. V. Ananyev 《Solar physics》1998,177(1-2):217-228

Variations of total solar irradiance, 10.7 cm radio emission, the Hei 10830 Ú equivalent width and the solar magnetic field flux measured for the entire Sun are compared with variations of the energy index of the global solar magnetic field and the index of the effective solar multipole for years 1979–1992. It is shown that photospheric radiation and that generated in the upper chromosphere and corona display different relationships with the global magnetic field of the Sun, and that interaction between the magnetic field and the solar irradiance is much more complicated than the traditional blocking effect.  相似文献   

Comparing shear-wave velocity profiles inverted from multichannel surface wave with borehole measurements   总被引：1，自引：0，他引：1  

Jianghai Xia  Richard D. Miller  Choon B. Park  James A. Hunter  James B. Harris  Julian Ivanov 《Soil Dynamics and Earthquake Engineering》2002,22(3)

Recent field tests illustrate the accuracy and consistency of calculating near-surface shear (S)-wave velocities using multichannel analysis of surface waves (MASW). S-wave velocity profiles (S-wave velocity vs. depth) derived from MASW compared favorably to direct borehole measurements at sites in Kansas, British Columbia, and Wyoming. Effects of changing the total number of recording channels, sampling interval, source offset, and receiver spacing on the inverted S-wave velocity were studied at a test site in Lawrence, Kansas. On the average, the difference between MASW calculated V_s and borehole measured V_s in eight wells along the Fraser River in Vancouver, Canada was less than 15%. One of the eight wells was a blind test well with the calculated overall difference between MASW and borehole measurements less than 9%. No systematic differences were observed in derived V_s values from any of the eight test sites. Surface wave analysis performed on surface data from Wyoming provided S-wave velocities in near-surface materials. Velocity profiles from MASW were confirmed by measurements based on suspension log analysis.  相似文献   

Properties of space and time distribution of solar coronal holes     

Ikhsanov  R.N.  Ivanov  V.G. 《Solar physics》1999,188(2):245-258

The space and time distribution properties of solar coronal holes (CH) are investigated. The data of the catalogue UAG-102, supplemented up to 1995, and synoptic H-charts of Solar Geophysical Data are used. It was found that both the polar and equatorial CH can be divided into two subclasses. The properties of time classes are discerned. Statistical weights of the recurrent CH are accounted, which allow to determine the character of rotation of the different classes of CH with more accuracy. It was shown that the equatorial CH with long lifetimes possess differential rotation that is similar to sunspot groups, and the long-living polar CH rotate as a rigid body. A conclusion about the existence of two types of large-scale solar magnetic fields is made.  相似文献   

Combining trace-element compositions, U–Pb geochronology and Hf isotopes in zircons to unravel complex calcalkaline magma chambers in the Upper Cretaceous Srednogorie zone (Bulgaria)     

I. Peytcheva  A. von Quadt  N. Georgiev  Zh. Ivanov  C.A. Heinrich  M. Frank   《Lithos》2008,104(1-4):405-427

Precise U–Pb geochronology and Hf isotope tracing of zircon is combined with whole-rock geochemical and Sr and Nd isotope data in order to unravel processes affecting mafic to felsic calcalkaline magmas prior to and during their crystallization in crustal magma chambers along the southern border of Central Srednogorie tectonic zone in Bulgaria (SE Europe). ID-TIMS U–Pb dating of single zircons from felsic and mixed/mingled dioritic to gabbroic horizons of single plutons define crystallization ages of around 86.5–86.0, 85.0–84.5 and 82 Ma. Concordia age uncertainties are generally less than 0.3 Ma (0.35%–2σ), and as good as 0.08 Ma (0.1%), when the weighted mean ²⁰⁶Pb/²³⁸U value is used. Such precision allows the distinction of magma replenishment processes if separated by more than 0.6–1.0 Ma and when they are marked by newly saturated zircons. We interpret zircon dates from a single sample that do not overlap to reflect new zircon growth during magma recharge in a long-lived crustal chamber. Mingling/mixing of the basaltic magma with colder granitoid mush at mid- to upper-crustal levels is proposed to explain zircon saturation and fast crystallization of U- and REE-rich zircons in the hybrid gabbro.Major and trace-element distribution and Sr and Nd whole-rock isotope chemistry define island arc affinities for the studied plutons. Slab derived fluids and a sediment component are constrained as enrichment sources for the mantle wedge-derived magma, though Hf isotopes in zircon suggest crustal assimilation was also important. Inherited zircons, and their corresponding ε-Hf, from the hybrid gabbroic rocks trace the lower crust as possible source for enrichment of the mantle magma. These inherited zircons are about 440 Ma old with ε-Hf of − 7 at 82 Ma, whereas newly saturated concordant Upper Cretaceous zircons reveal mantle ε-Hf values of + 7.2 to + 10.1. The upper and middle crusts contribute in the generation of the granitoid rocks. Their zircon inheritance is Lower Palaeozoic or significantly older and crustal dominated with 82–85 Ma corrected ε-Hf values of − 28. The Cretaceous concordant zircons in the granitoids are mantle dominated with a ε-Hf values spreading from + 3.9 to + 7.  相似文献   

New 40Ar/39Ar age constraints on the timing of magmatic events in the Panagyurishte region, Bulgaria     

Andrea B. Rieser  Franz Neubauer  Robert Handler  Svetlana H. Velichkova  Zivko Ivanov 《Swiss Journal of Geoscience》2008,101(1):107-123

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