Magnetic variation studies in the lake baikal region

Data on geomagnetic field variations observed at the Patrony and Enkhaluk observatories are used to study the induction vectors in the frequency-time domain. The main features of frequency responses related to conducting zones are examined. The results of monitoring the induction vectors are presented. The induction vectors are reliably determined in the period range 600–1300 s. This range is most suitable for magnetic variation monitoring. Annual variations are discovered in the behavior of induction vectors. Their specific features are examined. Anomalous variations in the modulus of the real part of the induction vectors are identified. These variations can be due to a strong earthquake (K = 15) in southern Lake Baikal.     

The geoelectrical properties of the earth around the Karymshina multidisciplinary observation site in southern Kamchatka

This paper is concerned with the Earth’s electromagnetic field, a deep geoelectrical section, and the dynamics of earth conductivity. This analysis is based on MTS curves along directions that to a first approximation go along and across southern Kamchatka. It is shown that the longitudinal and transverse MTS curves are subject to the influence of local and regional geoelectrical inhomogeneities. The coast effect was studied by 3-D numerical modeling. The patterns we have found were used for interpretation of generalized MTS curves. The resulting parameters of the geoelectrical section were refined by reducing the longitudinal curve to the standard curve of apparent resistivity. The results from this interpretation are to be refined as more geoelectrical information is forthcoming. The dynamics of lithospheric conductivity were studied from data acquired during the 2005–2008 monitoring of magnetotelluric impedance in the range of periods between several hundred and several thousand seconds. The basis for the analysis was assumed to be the transverse impedance and its phase. The latter was found to exhibit anomalous bay fluctuations that might have been related to earthquakes. A possible origin of these anomalies is discussed.     

Results of monitoring the geomagnetic variations at the Magadan and Paratunka observatories

We analyze the magnetic tensor and tipper data in the interval of periods from a few minutes to a few hours for the geomagnetic time series of 2007–2008. The frequency responses, the polar diagrams, and the real and imaginary induction arrows which reflect the effects of geoelectric heterogeneities are calculated. The monitoring of the tipper and tensor data series revealed the annual variations in these parameters, which are caused by the changes in the electric conductivity of the lithosphere. The anomalous variations identified in the behavior of the magnetic tipper and tensor are probably due to earthquakes with M ≥ 6.3.     

The Main Factors of Uranium Accumulation in the Ishim Plain Saline Lakes (Western Siberia)

Hydrochemical analysis of the high-salinity lakes in the Ishim Plain (>250–300 g/L) located at the border with the Northern Kazakhstan uranium ore province is performed. The studies have shown that the main factor of concentration and redistribution of uranium in the lake basins of the Ishim Plain are the processes of intense salt deflation causing sanding of lakes and uranium depletion in the near-surface layer of the bottom deposits. The correlation between the hydroxide forms of uranium binding in the bottom lacustrine deposits of the Ishim Plain and the coffinite composition of the Semizbai deposit makes it possible to consider this province to be promising for the discovery of hydromineral uranium deposits.

     

Geologic interpretation of the near-infrared images of the surface taken by the Venus Monitoring Camera,Venus Express

We analyze night-time near-infrared (NIR) thermal emission images of the Venus surface obtained with the 1-μm channel of the Venus Monitoring Camera onboard Venus Express. Comparison with the results of the Magellan radar survey and the model NIR images of the Beta-Phoebe region show that the night-time VMC images provide reliable information on spatial variations of the NIR surface emission. In this paper we consider if tessera terrain has the different NIR emissivity (and thus mineralogic composition) in comparison to the surrounding basaltic plains. This is done through the study of an area SW of Beta Regio where there is a massif of tessera terrain, Chimon-mana Tessera, surrounded by supposedly basaltic plains. Our analysis showed that 1-μm emissivity of tessera surface material is by 15–35% lower than that of relatively fresh supposedly basaltic lavas of plains and volcanic edifices. This is consistent with hypothesis that the tessera material is not basaltic, maybe felsic, that is in agreement with the results of analyses of VEX VIRTIS and Galileo NIMS data. If the felsic nature of venusian tesserae will be confirmed in further studies this may have important implications on geochemical environments in early history of Venus. We have found that the surface materials of plains in the study area are very variegated in their 1-μm emissivity, which probably reflects variability of degree of their chemical weathering. We have also found a possible decrease of the calculated emissivity at the top of Tuulikki Mons volcano which, if real, may be due to different (more felsic?) composition of volcanic products on the volcano summit.     

Annual variations in the electromagnetic field of the earth and electrical conductivity of the geological environment

Synchronous annual variations in the geoelectric and geomagnetic field are studied on the basis of long-term electromagnetic monitoring. It is shown that the annual geoelectric variations have intraterrestrial origin and are not related to the annual geomagnetic variations. Temporal variations in the magnetotelluric impedance and magnetic tipper, which characterize the electrical conductivity of the geological environment, are analyzed. It is established that annual variations in the magnetotelluric impedance mainly describe the variations in the electrical conductivity of surface crustal layers and are less sensitive to the deep electrical conductivity of the Earth. The annual variations in the imaginary magnetic tipper at the periods of 1000–3000 s probably reflect the changes in conductivity of a deep transversal low-resistive zone (the fault). It is suggested that annual variations in the geoelectrical and geomagnetic fields, as well as in the electrical conductivity of the geological environment, arise as a response to the changes in the geodynamical processes caused by the revolution of the Earth around the Sun.