Geochemical specifics of ongonites in the Ary-Bulak Massif, eastern Transbaikalia

A genetic model for magmatic rocks of the Ary-Bulak Massif is discussed based on a detailed geological map of the massif (prepared by the authors) and on original data of the authors on the petrography of the massif, its compositional zoning, trace-element geochemistry, physicochemical parameters of its crystallization, and melt inclusions in its minerals. The Ary-Bulak Massif was determined to be zonal, with the predominance (approximately 70% by area) of porphyritic topaz ongonites (central facies), which grade toward contacts into weakly porphyritic ongonites bearing topaz and, occasionally, fluorite (margin facies). Aphyric rocks with fluorite (inner-contact facies) occur as a stripe 50–80 m wide at the southwestern inner contact of the massif. Analysis of petrographic and geochemical data indicates that subvolcanic rocks of the Ary-Bulak Massif differ from typical elvanes (as they occur in the Cornwall province) but are similar to classic ongonites in the central and marginal facies of the massif. Rocks in the southwestern inner-contact zone are unusual high-F and high-Ca varieties, whose analogues have never been found in any rare-metal provinces with ongonites and which provide evidence of a complicated evolutionary history of the Ary-Bulak Massif. The geochemical evolution of this massif was determined to be characterized by the enrichment of the older inner-contact facies rocks in CaO, K₂O, F, and Rb, Cs, B, Ba, Sr, Sn, and Ta, whose concentrations decrease in the ongonites of the central facies. The central-facies ongonites thereby have much higher Na₂O and Li concentrations than those in the inner-contact facies rocks. It is demonstrated that the intense heating and melting of crustal material in this region at the Jurassic-Cretaceous boundary could have been induced by subalkaline basaltic magma. The chemical composition of the rocks, which is unusual for typical ongonites in, for example, high Ca and Sr concentrations, could be caused by the possible assimilation by the magma of limestones, which occur in the territory at a certain depth in the Ust’-Borzya Formation that hosts the Ary-Bulak Massif. The genesis of most rocks in the massif was controlled by the magmatic differentiation of crustal granitic magma, with the residual melts forming Li-F granites enriched in several trace elements (Li, Rb, Cs, B, Ba, Sr, etc.) and ongonites as their subvolcanic analogues.     

The fauna of the Aral Sea in 1989. 1. The benthos

The benthos of the Small and Large Aral Sea was investigated in 1989. OnlyNereis diversicolor, Syndosmya segmentum, Cerastoderma isthmicum, Caspiohydrobia spp., Chironomidae andPalaemon elegans occurred in the Small Sea. In the Large Sea, the benthos was similar, but Chironomidae were absent andRhithropanopeus harrisii was present.     

Validation of the WAMC4 wave model for the Black Sea

The present paper describes the set-up and application of the third-generation wave model — WAM Cycle 4 to the Black Sea. The wind fields are calculated by a regional atmosphere model (REMO), which was driven with the conditions from the global NCEP re-analysis project. These atmospheric data are used to force the state-of-the-art WAM model. The validation is done by comparison of wave model output against directional buoy measurements registered at three deep-water locations and wave gauge data taken at a point in intermediate depth near the Black Sea coast. The results reveal that agreement between modeled and measured data is satisfactory and the quality of the simulations increases under more energetic and severer wind and wave conditions. Following the validation, a 41-year wave hindcast was implemented spanning the period 1958–1998.     

Prominence activity during the ascending phase of solar cycle 22

Longitude-latitude and time-latitude distributions of the number and area of prominences observed at Lomnický Stit coronal station in the years 1986–1990 are studied using the method of contour maps construction with different degree of smoothing. Special attention is paid to the bifurcation in the prominence distribution. Comparison with the ascending phase of solar cycle 21 is made.     

Paleomagnetic data on the sedimentation rate near the Mendeleev Rise (Arctic Ocean)

Seven cores of bottom sediments were collected during the cruise of R/V Akademik Fedorov in 2000 along the latitudinal profile crossing the Mendeleev Rise near 82° N, and then studied. The length of cores varies from 240 to 334 cm. In all cores, the boundary of the changing remanent magnetization vector corresponding to the Brunhes-Matuyama boundary was established reliably. In five cores, this boundary is at a depth of 86–102 cm; in two cores, collected to the west of the Mendeleev Rise, at depth levels of 188 and 208 cm. The correlation of paleomagnetic and lithological data demonstrates that the upper boundary of a bench of speckled pelites, overlapped by a bench of variegated pelites, is confined to the Olduvai episode or horizons lying slightly below. The average sedimentation rate of sediments from the Mendeleev Rise during the last 2–2.5 Ma have not exceeded 1–1.3 mm/ka, increasing towards the shelf seas of northeast Russia.     

Sunspot Activity and Coronal Holes during the Declining Phase of Cycle 24

Geomagnetism and Aeronomy - The dynamics of coronal holes (CHs) during the declining phase of solar cycle 24 is studied based on observational data from the Atmospheric Imaging Assembly (AIA), the...     

Changes in Water Quality in the Bureiskoe Reservoir Caused by a Large Landslide

Water Resources - The study considers the factors that had an effect on water quality in the Bureiskoe Reservoir (Far East) after a large landslide event in December 2018 (with a volume of 24.5...     

Microseismic Sounding and Active Faults of the Kerch-Taman Region

Izvestiya, Physics of the Solid Earth - Abstract—The results of integrated geological and geophysical studies of active faults and deep structure of the Kerch-Taman region are presented. Data...     

Deep Structure and Folded-Block Structure of the Garhwal Himalayas (India): Results of Integrated Geological and Geophysical Study

Geotectonics - The geological and geophysical study of the representative segment of the Alpine-Himalayan mobile belt—the Central zone of the Garhwal Himalaya—was conducted. The results...     

Macroseismic manifestations of the Okhotsk earthquake of May 24, 2013 in the territory of Moscow

The results of a study of the macroseismic effects in the territory of Moscow of a remote deepfocus earthquake that occurred on May 24, 2013 in the Sea of Okhotsk are reported. On the surface of the earth and on the first floors of the buildings the seismic effect was not felt. The effect of the shock began to manifest itself at levels higher than the fifth floor of the buildings. The distribution of points on the map where the earthquake was felt is non-uniform. Points where tremor was felt do not appear to correspond with certain types of Quaternary deposits or with zones of different depth. There is also no significant correlation of the parts of the surface with high intensities of tremor and areas of ground-water flooding. Comparison between the surface manifestations of the seismic event and the tectonic features and deep structure of the metropolis was made. Based on the results of the implemented statistical estimation of distribution points where the earthquake was felt on the territory of the city it is visible that fault zones govern the largest number of points, while block structures characterize almost half of them. Thus, we can reasonably suggest a certain macroseismic increase of vibrations from earthquakes in the areas of large faults in the city. The study of deformations of the asphalt cover of walkways on the landslide-affected slope of Vorobyovy Hills showed that the tremor caused by the Okhotsk deep focus earthquake of May 24, 2013, caused the activation of a small landslide at all levels of the hillside.