Structural-morphological and REE geochemical control of the correctness of Sm-Nd dating for fluorite formation in the garsonui deposit,eastern Transbaikalia

Using ICP-MS, X-ray excited optical luminescence (XEOL), and Sm-Nd isotopic analysis, the distribution, structural position, and isotopic characteristics of isomorphic REE admixtures were studied in ten fluorite samples with different colors, morphologies, and cleavage characteristics from the Garsonui epithermal deposit. It was shown that the comprehensive analysis of the structural-morphological and REE geochemical features of samples can be used for the optimization of sample selection for correct Sm-Nd dating. As a result, the Sm-Nd method was used for the first time to constrain the age of the main stage of the formation of the Garsonui deposit, which is one of the largest fluorite deposits in Transbaikalia, as 141 ± 6 Ma.     

Dynamics and energetics of the thermal and nonthermal components in the solar flare of January 20, 2005, based on data from hard electromagnetic radiation detectors onboard the CORONAS-F satellite

Based on data from the SONG and SPR-N multichannel hard electromagnetic radiation detectors onboard the CORONAS-F space observatory and the X-ray monitors onboard GOES satellites, we have distinguished the thermal and nonthermal components in the X-ray spectrum of an extreme solar flare on January 20, 2005. In the impulsive flare phase determined from the time of the most efficient electron and proton acceleration, we have obtained parameters of the spectra for both components and their variations in the time interval 06:43–06:54 UT. The spectral index in the energy range 0.2–2 MeV for a single-power-law spectrum of accelerated electrons is shown to have been close to 3.4 for most of the time interval under consideration. We have determined the time dependence of the lower energy cutoff in the energy spectrum of nonthermal photons E _γ0(t) at which the spectral flux densities of the thermal and nonthermal components become equal. The power deposited by accelerated electrons into the flare volume has been estimated using the thick-target model under two assumptions about the boundary energy E ₀ of the electron spectrum: (i) E ₀ is determined by E _γ0(t) and (ii) E ₀ is determined by the characteristic heated plasma energy (≈5kT (t)). The reality of the first assumption is proven by the fact that plasma cooling sets in at a time when the radiative losses begin to prevail over the power deposited by electrons only in this case. Comparison of the total energy deposited by electrons with a boundary energy E _γ0(t) with the thermal energy of the emitting plasma in the time interval under consideration has shown that the total energy deposited by accelerated electrons at the beginning of the impulsive flare phase before 06:47 UT exceeds the thermal plasma energy by a factor of 1.5–2; subsequently, these energies become approximately equal and are ～(4–5) × 10³⁰ erg under the assumption that the filling factor is 0.5–0.6.     

Isotopic-geochronological systems in metamorphic rocks: Pon’goma Island,Belomorian mobile belt

Several isotopic methods (U-Pb, Sm-Nd, Rb-Sr, and K-Ar) were applied to different rock-forming and accessory minerals to decipher the chronology of events in a separate segment of the Belomorian mobile belt. Enderbites intruded supracrustal rocks at 2.73 Ga and granodiorites were emplaced at 2.41 Ga. Immediately afterwrads, a permeable schistosity zone was formed along the enderbite-granodiorite contact. Isotopic data indicate that this zone served as a pathway for heat and fluid. The retrograde stage of regional metamorphism and subsequent cooling continued from 1.89 Ga till ～ 1.46 Ga.The cooling rate of the Pon’goma Island rocks is similar to that of other Precambrian complexes and amounted to ～1.5⁰/Ma, which is consistent with previous data on the northern segment of the Belomorian belt. Based on isotopic geochronological data, two tectonometamorphic scenarios can be proposed for the evolution of the Belomorian belt. The first scenario suggests long-term regional metamorphism, i.e., lengthy residence of the Archean and Lower Proterozoic rocks at a significant depth and high temperatures. Geochronological data for different systems (U-Pb, Sm-Nd, Rb-Sr, and K-Ar) suggest Caledonian hydrothermal cryptometamorphic processes. However the rocks of this age are absent from the study area.     

On geoeffective solar flares and variations of the seismic noise level

The work continues the study of interrelations between strong flare-induced magnetic storms and variations of seismicity. Using data on the time dependences of the parameters of seismic noise (average level and root mean squared (RMS)), recorded by stations of the KNET seismic network during monitoring of the territory of Bishkek geodynamic site (North Tien Shan). The presented results indicate the high sensitivity of the seismic noise in the frequency range of 10–20 Hz to external and, in particular, electromagnetic effects in comparison to the seismic activity. We noted the manifestations of the effects of magnetic storms that occurred after strong and super-strong solar flares in 2000–2006. These were short-term increases in the RMS of seismic noise, preceding changes in the accumulation rate of the number of events. The obtained results agree with conclusions about the interrelation between seismicity and magnetic storms. A model is suggested to describe one of the possible mechanisms by which the electromagnetic pulses and the currents induced by them in a medium devoid of piezoelectric properties influence the seismic process.     

On the stimulation of acoustic emission in rock samples by electromagnetic fields

The combined impacts of the electromagnetic fields generated by two independent sources on the process of crack formation in loaded heterogeneous materials (rocks) are studied. The interest in such experiments lies in the fact that in natural conditions, the combination of several fields—the potential triggers of seismic activity—is rather the rule than the exception. It is shown by examples that in the conditions of crossed electric and magnetic fields (CrEMFs) the enhancement in acoustic activity can be triggered with a lower strength electric field than in case of the electric impact alone.     

Rare-earth mineralization in early Carboniferous coals of the Volga-Ural region

This study presents new ICP spectroscopy data on lanthanide concentrations in early Carboniferous coal deposits in the Volga-Ural region. The results confirmed an overall LREE over HREE enrichment and emphasized the role of carbonate host strata as a major factor that is responsible for REE enrichment and geochemical anomalies. The results of this study were also used to identify the modes of REE occurrences in the organic and inorganic constituents of coal.     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

This paper reports the first results of a study of 11 isotope systems (³He/⁴He, ⁴⁰Ar/³⁶Ar, ³⁴S/³²S, ⁶⁵Cu/⁶³Cu, ⁶²Ni/⁶⁰Ni, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ^206–208Pb/²⁰⁴Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.     

Stereoscopic observations of solar flares made onboard the 2001 Mars Odyssey spacecraft and CORONAS-F satellite

The results of observations of solar hard radiation recorded by two spacecraft—2001 Mars Odyssey and CORONAS-F—which were located in the vicinity of Mars and Earth, respectively, are discussed. The HEND instrument, developed at the Space Research Institute of the Russian Academy of Sciences, recorded photons with energies ranging from 80 keV to 2 MeV, and the SPR and SONG instruments, developed at the Skobeltsyn Research Institute of Nuclear Physics of the Moscow State University, detected radiation in the energy interval from 15 keV to 100 MeV. The rising of the sunspot group 10486 in late October 2003, which had been observed from Martian orbit before it was seen from the Earth’s surface, is analyzed in detail. In this case, observations made from directions that differ by 24° showed a close-to-24 h advance for the detection of hard radiation of flares. Stereoscopic observations of M-class flares near the limb show that the overwhelming part of radiation with energies above 80 keV arises at heights that do not exceed 7–10 thousand km. Also reported are the results of observations of the powerful flare on August 25, 2001, by the two devices, which complement each other substantially. The processes resulting in the formation of high-energy radiation of solar flares are discussed.     

A comparison of finely dispersed mineral components in fossil coals of the Kama and Donets basins

This study presents the results of SEM-EDX analysis of the mineral components of coals from the Kama (Volga-Ural region) and Donets basins and discusses the characteristics of the depositional environments and conditions of coalification. The results reveal differences in the mineral composition of coals from these two basins.