Normative quartz as an indicator of the mass transfer intensity during the postmagmatic alteration of the Botuobinskaya pipe kimberlites (Yakutia)

The intensity of postmagmatic processes in the Botuobinskaya pipe kimberlites was estimated from the calculated content of normative secondary quartz (Q). Several simple algorithms are proposed to calculate the Q content from chemical analyses of kimberlites. Ten groups of altered kimberlites have been recognized from the Q contents. The contents of MgO, some trace elements, and LREE in the groups, the contents of Cr and Ca of crimson garnets, the diamond contents of kimberlites, and the average weight of diamonds decrease as the Q content increases. It is shown that the negative SiO₂–MgO correlation is the most effective indicator of the postmagmatic alteration of kimberlites. As the degree of their secondary alteration increases, the kimberlites transform into an assemblage of quartz and clay minerals enriched in some trace elements and almost completely lacking REE and diamonds.     

The statistical structure of the field of surface soil layer moisture from ground-based and satellite observations

The following data was used: the archives of measurements of available water capacity carried out at Roshydromet network of stations and satellite measurements of relative humidity of the upper soil layer from ASCAT data (from the MetOp satellites). The statistical structure of the field of available water capacity in the upper 10- and 20-cm soil layers is assessed. The correlations between the Earth remote sensing data and data from agrometeorological stations are revealed. The procedure of automatic data checking from ground-based observations is developed. The algorithm is suggested for statistically optimal conversion of the Earth remote sensing data to the estimate of moisture content in the upper soil layer.     

GPS-based modeling of the interaction between the lithospheric plates in Sakhalin

The recent geodynamics of Sakhalin are determined by the convergence between the Eurasian and North American lithospheric plates, which is reflected in the high seismicity of the island. The method of inversion of the horizontal velocities of the island surface with account for the geological features of the region is used to analyze the different models of the convergence between the plates. This made it possible to estimate the depth of the mechanical contact between the plates and the velocities of their convergence for the southern, central, and northern segments of the island.     

Horizontal motions and the generation of strong earthquakes in the North Sakhalin interiors

The recent geodynamics of Sakhalin Island is best described by the convergence of the Eurasian and North American (Sea of Okhotsk) lithospheric plates, which is manifested in the high seismic activity of the island. In North Sakhalin, the plate boundary is thought to correspond to a system of roughly N-S-trending faults, which belong to the North Sakhalin deep fault, and the Upper-Piltun fault; the latter was ruptured by the 1995 M 7.2 Neftegorsk earthquake. This study first confirmed that the stationary motion of the Sea of Okhotsk plate is retarded on this fault to form with time a series of drag folds and stress field anomalies. The latter are released during the subsequent (in a 400⦒o 1000-year period) strong earthquakes by seismic sliding on the flanks of the Upper Piltun fault. The 2003–2006 GPS observations revealed the free state of this fault zone with relative slip rates of 5–6 mm/yr.     

Satellite Monitoring of Sea Ice Cover and Water Parameters for the Caspian Sea

A number of technologies have been developed in the Planeta Research Center for Space Hydrometeorology to provide the satellite monitoring of sea ice cover and water parameters for the Caspian Sea. These technologies produce maps of sea ice, sea ice drift, tracking of near-surface water fluxes, automated classification of ice and water objects, surface wind, and sea surface temperature. Satellite-based products are used for operational hydrometeorology and climate studies of the Caspian Sea environment. A specialized web service for the preparation and comprehensive analysis of satellite data on hydrometeorological and ice conditions in the Caspian Sea was developed to provide information on ice cover characteristics, surface wind, and sea surface temperature.     

Petromagnetic parameters of bottom sediments as indicators of the climatic and environmental changes in the central zone of the Sea of Okhotsk during the last 350 kyr

Bottom sediments from the central zone of the Sea of Okhotsk were preliminarily dated. The petromagnetic parameters of two groups of samples formed at cold and warm climatic stages were studied. Warm oxygen isotopic stages and substages were characterized by the coexistence of pseudo-single-domain allogenic magnetite and predominant magnetite and greigite (pyrrhotite) grains subject to biologic control. At cold stages, sediments containing a mixture of pseudo-single-domain and multidomain terrigenous magnetite particles accumulated. The petromagnetic curves agree with the normalized standard oxygen isotopic curve over the last 350 kyr of the column section.     

Rare Earth Elements in the Bottom Sediments of the East Arctic Seas of Russia as Indicators of Terrigenous Input

The REE distribution was studied in the bottom sediments of the East Arctic shelf of Russia. It is established that sediments of the Laptev and western East Siberian seas are significantly enriched in REEs, the contents of which are much higher than those of other near-continental basins. The main REE sources are runoff of the Lena River, the basin of which comprises ancient crystalline shields and magmatic rocks enriched in LREEs with significant contribution from the coastal erosion of the ice complex from the Laptev Sea and western East Siberian Sea. The terrigenous flux with a specific REE composition is supplied to the Chukchi Sea through the Bering Strait.     

Simulation of the 2011 South Sakhalin mud volcano eruption based on the GPS data

Sakhalin Island is the only region in the Russian Far East where mud volcanism is manifested on land. The South Sakhalin mud volcano is located in the south of the island in the zone of the Central Sakhalin Fault (upthrow-thrust). The horizontal and vertical displacements of the earth’s surface after this mud volcano erupted in 2011 are revealed for the first time based on the GPS observation data. On the basis of the inversion of the measured displacements for the homogeneous elastic half-space, a model of the finite spherical eruption source is constructed. The coordinates, depth, and possible size of the source are defined and the volumes of the erupted clay rock, water, and gas are estimated.     

Behavior of major and rare-earth elements during the postmagmatic alteration of kimberlites

During serpentinization and subsequent alteration in the absence of brucite, kimberlites accumulate uncompensated silica. Its amount can be calculated from the average compositions of the rock-forming minerals (olivine, calcite, phlogopite) and the chemical compositions of the rocks. The contents of rock-forming oxides and REE were determined in 12 kimberlite pipes of the Yakutian kimberlite province, in 413 samples from secondary-alteration zones and of unaltered kimberlites. Columns of successive kimberlite alterations were constructed for each pipe on the basis of secondary-quartz data; here, the behavior of rock-forming oxides and REE was assessed. All the studied rocks had experienced different degrees of postmagmatic hydrothermal metasomatism at different depths in all the pipes. The changes were reflected in the supply/loss of rock-forming oxides and REE. The supply of REE during the hydrothermal metasomatism enriched the kimberlites with TiO₂, P₂O₅, and CaO. During the removal of REE, most of the rock-forming oxides were partially lost. The maximum REE supply was 67% in the Udachnaya-Vostochnaya pipe and 59% in the Nyurbinskaya pipe as compared with the unaltered kimberlites. The maximum REE loss was 87% in the Aikhal pipe and 81% in the Internatsional’naya pipe as compared with the unaltered kimberlites. The initial REE contents of the postmagmatically altered kimberlites changed considerably in all the studied cases. This conclusion was drawn owing to the use of normative-quartz content as a criterion for secondary alteration.