Environmental-geochemical state of the Yuzhnoural’skaya SDPP reservoir

The presented results were obtained in a long-term multidisciplinary study of the water-cooling reservoir of the Yuzhnoural’skaya SDPP, burning high-ash brown coals from the Chelyabinsk Basin. Up-to-date analytical methods (X-ray fluorescence analysis on synchrotron beams, atomic absorption spectrometry, and capillary electrophoresis) were used to study the microelement composition of coal, ash, and slag of the Yuzhnoural’skaya SDPP, soils from ash dumps and territories adjacent to the SDPP, as well as reservoir bottom sediments. The hydrochemical characteristics of the reservoir and water chemistry in the SDPP engineering system were determined. The levels of accumulation of microelements and heavy metals by aquatic organisms in the reservoir were evaluated. Special attention is paid to the analysis of the sources of arsenic in the reservoir.     

Improvement of Local Categorical Precipitation Forecasts from an NWP Model by Various Statistical Postprocessing Methods

Several statistical postprocessing methods are applied to results from a numerical weather prediction (NWP) model to test the potential for increasing the accuracy of its local precipitation forecasts. Categorical (Yes/No) forecasts for 12hr precipitation sums equalling or exceeding 0.1, 2.0 and 5.0 mm are selected for improvement. The two 12hr periods 0600-1800 UTC and 1800-0600 UTC are treated separately based on NWP model initial times 0000 UTC and 1200 UTC, respectively. Input data are taken from three successive summer seasons, April-September, 1994-96. The forecasts are prepared and verified for five synoptic stations, four located in the western Czech Republic, and one in Germany near the Czech-German border. Two approaches to statistical postprocessing are tested. The first uses Model Output Statistics (MOS) and the second modifies the MOS approach by applying a successive learning technique (SLT). For each approach several statistical models for the relationship between NWP model predictors and predictand were studied. An independent data set is used for forecast verification with the skill measured by a True Skill Score. The results of the statistical postprocessing are compared with the direct model precipitation forecasts from gridpoints nearest the stations, and they show that both postprocessing approaches provide substantially better forecasts than the direct NWP model output. The relative improvement increases with increasing precipitation amount and there is no significant difference in performance between the two 12hr periods. The skill of the SLT does not depend significantly on the size of the initial learning sample, but its results are nevertheless comparable with the results obtained from the MOS approach, which requires larger developmental samples.     

Pseudotachylites of the Main Anabar Fault (Northern Yakutia): Petrological and Chronological Indicators of Melting during High Rate Tectonic Deformations

Doklady Earth Sciences - The results of the 40Ar/39Ar dating of the vein material of pseudotachylite from the deformation zone of the Main Anabar fault (Northern Yakutia) are presented. The depth...     

Gas reservoirs in the Dead Sea area: evidence from chemistry of combustion metamorphic rocks in Nabi Musa fossil mud volcano

Nabi Musa located at the northern tip of the Dead Sea at 31°48′ N, 35°25′ E is one of fifteen complexes of the Hatrurim Formation or the so-called “Mottled Zone” (MZ) which are fossil mud volcanoes. Self ignition of methane during their eruptions in the Middle–Late Pleistocene caused combustion metamorphism of sediments. Melting foci have been discovered in two craters of Nabi Musa volcano, with numerous veins of paralavas having particular calcic-silicic compositions (Ca₂SiO₄- and CaSiO₃-normative). Their major- and trace-element spectra bear signature of a mixed sedimentary protolith consisting of Cretaceous marine carbonates, marl, and quartz sand. The paralavas inherit high Sr, P, and U enrichments, positive La/La* and Y anomalies, and a negative Ce/Ce* anomaly from calcareous marine sediments, including bituminous and apatite-rich chalks. The presence of quartz arenite in the protolith is responsible for relatively high Ti, Nb, Zr, and Hf while the marl pelitic component accounts for MREE and LREE depletion. The suggested mixing models predict that the Nabi Musa paralavas result from combustion metamorphism of a sediment mixture with 53–60 wt.% chalk, 5–14 wt.% marl, and 27–44 wt.% quartz arenite. The history of mud volcanism at Nabi Musa began with small eruptions that mobilized gas and water from shallow (within 300 m) Turonian carbonate aquifers, and later explosive activity triggered violent gas blowouts from the older terrigenous reservoir of Aptian–Albian Nubian-type sandstone lying as deep as 1300–1500 m.     

Late accretion and lithification of chondritic parent bodies: Mg isotope studies on fragments from primitive chondrites and chondritic breccias

Abstract— Recent results of isotopic dating studies (¹⁸²Hf‐¹⁸²W, ²⁶Al‐²⁶Mg) and the increasing number of observed igneous and metamorphosed fragments in (primitive) chondrites provide strong evidence that accretion of differentiated planetesimals predates that of primitive chondrite parent bodies. The primitive chondrites Adrar 003 and Acfer 094 contain some unusual fragments that seem to have undergone recrystallization. Magnesium isotope analyses reveal no detectable radiogenic ²⁶Mg in any of the studied fragments. The possibility that evidence for ²⁶Al was destroyed by parent body metamorphism after formation is not likely because several other constituents of these chondrites do not show any metamorphic features. Since final accretion of a planetesimal must have occurred after formation of its youngest components, formation of these parent bodies must thus have been relatively late (i.e., after most ²⁶Al had decayed). Al‐Mg isotope data for some igneous‐textured clasts (granitoids and andesitic fragments) within the two chondrite regolith breccias Adzhi‐Bogdo and Study Butte reveal also no evidence for radiogenic ²⁶Mg. As calculated from the upper limits, the formation of these igneous clasts, the incorporation into the parent body regolith, and the lithification must have occurred at least 3.8 Myr (andesite in Study Butte) and 4.7 Myr (granitoids in Adzhi‐Bogdo) after calcium‐aluminum‐rich inclusions (CAI) formation. The absence of ²⁶Mg excess in the igneous inclusions does not exclude ²⁶Al from being a heat source for planetary melting. In large, early formed planetesimals, cooling below the closure temperature of the Al‐Mg system may be too late for any evidence for live ²⁶Al (in the form of ²⁶Mg excess) to be preserved. Thus, growing evidence exists that chondritic meteorites represent the products of a complex, multi‐stage history of accretion, parent body modification, disruption and re‐accretion.     

The Phosphates of Pleistocene–Holocene Sediments of the Eastern Gallery of Denisova Cave

Authigenic phosphate mineralization was first studied on the territory of Russia on the basis of the Holocene and Pleistocene deposits of Denisova Cave. The formation of phosphates in the eastern gallery is related to biodegradation of the horizons of guano of insectivorous bats, which inhabited the cave in the absence man. The results confirmed the archaeological record of the Holocene and the upper part of Pleistocene sequences of the eastern gallery.     

Synthesis of NH4-Substituted Muscovite at 6.3 GPa and 1000°C: Implications for Nitrogen Transport to the Earth’s Mantle

Doklady Earth Sciences - The synthesis of NH4-bearing muscovite at P = 6.3 GPa and T = 1000°C in equilibrium with NH3–H2O fluid is performed. It is determined that the newly formed...     

230Th/U Dating of Travertines Related to Paleoearthquakes in Gorny Altai: First Results

Doklady Earth Sciences - First 230Th/U-dating results have been obtained for six Quaternary travertine deposits from the southeastern Gorny Altai associated with zones of active faults that bound...