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[en] The results of study of the alkaline silicate melt–hydrous saline (carbonate, sulfate, and fluoride) fluid system, as well as partitioning of ore metals (Ba, Sr, and REEs) between coexisting phases at T = 1250°C and P = 2 kbar are reported. It is shown that aqueous solutions with the compositions studied cannot be effective concentrators and transporters of ore elements such as REEs, Sr, and Ba. The sulfate melt accumulates Sr and Ba in the alkaline silicate melt–hydrous sulfate fluid system, which provides evidence for the efficiency of sulfate ore extraction of Sr and Ba from the melt. The results obtained support the important oregenerating role of dense saline phases formed upon the development of liquid heterogeneity in fluid–magmatic systems.
[en] New age dating (291 Ma) was obtained for one of the largest alkaline granite massifs in the world, the Khan–Bogd Massif (Mongolia). For the first time, apart from zircon, other zirconium silicates, elpidite and armstrongite, have been analyzed. Our determinations showed the highly depleted nature of the mantle sources of granites with εNd = 12. All the studied Zr-silicates demonstrate positive Eu anomalies in the REE patterns, which indicate a low oxidation potential during alkaline granite formation.
[en] New U–Pb and Sm–Nd isotope data have been obtained in the Kandalaksha–Kolvitsa zone, Baltic Shield, on accessory zircon and rutile, along with whole-rock and secondary metamorphic minerals. Isotope U–Pb age of single zircon grains from metagabbro of the Kandalaksha Anorthosite Massif is 2453.5 ± 4.8 Ma, which is close to the U–Pb age of zircon from the Kolvitsa Massif metagabbro (2448 ± 5 Ma). For the first time, REEs in zircon grains of the Kandalaksha metagabbro have been analyzed and the results have been plotted. Ti-in-zircon thermometry has been applied using LA–ICP–MS: it yielded an average temperature of zircon crystallization of 844°C. The isotope and geochemical new data obtained indicate a magmatic genesis of the zircon crystals studied.
[en] The composition, age, and genetic relationships of spodumene pegmatites of the Khusuingol field (South Sangilen pegmatite belt, SW Sayan), encompassing the large Tastyg lithium deposit, with granitoids of the neighboring polygenic Dzos-Khusuingol batholith have been studied. SHRIMP-II U–Pb zircon analyses yielded an Early Paleozoic age of the granites and pegmatites. The tectonic settings of the formation of these rocks are discussed.
[en] A fundamentally new conclusion that zones of high seismic activity are controlled by electroconducting (fluid-saturated) fragments rather than by the entire deep fault is drawn. It is shown that the areal abundance of earthquake foci in geoelectric blocks of the Earth’s crust within Sakhalin and Vietnam containing electroconducting formations is mostly controlled by their roof occurring at a depth of ≤15 km.
[en] The patterns of the distribution of technogenic radionuclides 137Cs and 90Sr in the water mass and bottom deposits of three fjords of Western Spitsbergen (Isfjorden and its arms Grønfjorden and Billefjorden) were studied. The hydrological processes affecting migration of radionuclides in these water bodies were described. It was shown that the ice sheet of the archipelago that accumulates atmospheric precipitation is a source of radioactive contamination of the marine environment of the coast. Technogenic isotopes were accumulated during nuclear weapon testing in the second half of the twentieth century. The current climatic changes strengthen the role of glaciers in the contamination of arctic seas. It was noted that extrema of the 137Cs and 90Sr specific activity is mainly concentrated in the areas of glacier runoff discharge.
[en] This work is devoted to the problems of elaboration of the instrumental basis for low-frequency sensing of ambient noise of the ocean. The experimental data of testing of the technical parameters of a molecular-electronic hydrophone are given. The amplitude-frequency and noise parameters of prototypes have been studied. The operation of a hydrophone with a frequency range of 0.02–200 Hz and sensitivity of 0.75 mV/Pa is described. Ambient noise was measured with the use of correlation analysis.
[en] On the basis of combined analysis of data on a geological survey on a scale of 1 : 200 000 (1959–1960) and exploration works (1980–1990), it was found that the zones of higher radioactivity and related rich La–Ce ores are localized along linear faults 10–15 km long parallel to the axis of the Udzha Anticline. The HREE mineralization of the Y–Yb group is concentrated in sandstones and gravelstones of the Vendian Tomtor Formation, which unconformably overlap the Udzha Anticline on its wings. This indicates that the volatile flow has a deep (transmagmatic) origin rather than separation from magma. A carbonatite body with sulfide veinlets and dissemination is described with respect to a zone of high contents of La–Ce ores. The complex character of the Tomtor ores is explained by the juxtaposition of mineralization phases of various ages and composition: Nb and Sc–Th mineralization paragenetically related to the central ring structure of the intrusion and to the external rischorrite zone, respectively.
[en] Diatom analysis and radiocarbon dating of the sedimentary cover of terraces on the southeastern coast of the Gorlo Strait (White Sea) were carried out for the first time. The studies were conducted at sites from Cape Veprevskii to Cape Intsy. The Holocene marine sediments were traced up to 4 m a.s.l. The relative sea level rose during the Boreal and the first half of the Atlantic periods. The sea level reached the present value not earlier than 8500 14C ysr BP and probably was stabilized at 3.5–4.0 m a.s.l. about 6300 14C yrs BP. The sea regression is dated to approximately 3000 14C yrs BP, when the marine settings of sediment accumulation changed to continental ones. The higher levels were formed prior to 9500–8500 14C yrs BP and were not later flooded by the sea according to the data of diatom analysis. During the Early Holocene regression, the assumptive paleosol horizons were formed there. They are covered by lacustrine, peaty, and aeolian sediments.
[en] This paper clarifies the structure of the Bol’shoi Ilek section (height up to 83 m), which is composed by the deposits of Cretaceous and Quaternary systems, in the southeastern part of Western Siberia. The major volume of the section comprises the Lower Cretaceous rocks of the delta complex, reaching a thickness of 80 m and characterizing the Ilek Formation stratotype. The remains of fishes, lizards, turtles, crocodiliforms, dinosaurs, and mammals typical for the Barremian–Early Albian were found for the first time when screen-washing the sand fraction. The Mesozoic rocks are superposed by Quaternary eolian–deluvial and eluvial deposits with a thickness of 3–13.5 m or more. This sequence consists of three layers with mammoth fauna remains, the middle of which is dated at 14C ~ 22 500 years ago. In addition, according to the investigation data, Bol’shoi Ilek is a huge landslide with an area of more than 1 km2. All these facts make it possible to draw an analogy with the even-aged section of the Shestakovo high bank which also partially exposes the giant landslide. Such landslides are triggered by earthquakes with a magnitude of more than nine points, which is indicative of a powerful seismic event that occurred in the southeastern part of the study region at the very end of the Pleistocene.