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Vladivostok, Russia

Grebennikov A.V.,Far East Geological Institute
Journal of Earth Science | Year: 2011

A comprehensive mineralogical-geochemical and petrological study of ignimbrites from the Yakut-Gora volcanic depression (Primorye, Far Eastern Russia) revealed a wide distribution of silica-metal spherules ("globules") that are typical liquid immiscibility resultant. The metallic portion of a spherule (composition varies from low-carbon iron to cohenite) borders gas pores and is rimmed by symplectite that consists of quartz, magnetite, and silica-potassic glass. This allows us to consider that the whole formation formed through reduction of the enclosing silicate melt. Abundant evidence of high reduction states of ignimbrite melts and the presence of iron carbides suggest an H 2-CH 4 composition of the fluidal phase in ignimbrite magmas. © 2011 China University of Geosciences and Springer-Verlag Berlin Heidelberg.

Chugaev A.V.,RAS Institute of Geology and Mineralogy | Bortnikov N.S.,RAS Institute of Geology and Mineralogy | Gonevchuk V.G.,Far East Geological Institute | Gorelikova N.V.,RAS Institute of Geology and Mineralogy | And 2 more authors.
Geology of Ore Deposits | Year: 2012

The age of the main productive phase of ore formation at the large Solnechnoe tin deposit has been estimated for the first time based on the study of the Rb-Sr isotopic system of hydrothermal quartz and adularia from ore veins and metasomatic rocks. The Rb-Sr isochron age (84 ± 1 Ma) of mineralization coincides with the age of intrusive rocks pertaining to the third phase of the Silinka Complex, which control tin mineralization. The 87Sr/ 86Sr ratios of ore-forming solution and granitic rocks of the final intrusive phase are close to each other, indicating that the granitic melt was most likely one of the main sources of metals. The long and multistage formation history of the deposit could have been caused by complex geodynamic evolution of the Sikhote-Alin accretionary fold region in the Cretaceous. © 2012 Pleiades Publishing, Ltd.

Ueta A.,Hokkaido University | Sugimoto A.,Hokkaido University | Iijima Y.,Institute of Observational Research Center for Global Change | Yabuki H.,Institute of Observational Research Center for Global Change | And 3 more authors.
Hydrological Processes | Year: 2013

Deciduous forest covers vast areas of permafrost under severe dry climate in eastern Siberia. Understanding the water cycle in this forest ecosystem is quite important for climate projection. In this study, diurnal variations in isotopic compositions of atmospheric water vapour were observed in eastern Siberia with isotope analyses of precipitation, sap water of larch trees, soil water, and water in surface organic layer during the late summer periods of 2006, 2007, and 2008. In these years, the soil moisture content was considerably high due to unusually large amounts of summer rainfall and winter snowfall. The observed sap water δ18O ranged from -17.9‰ to -13.3‰, which was close to that of summer precipitation and soil water in the shallow layer, and represents that of transpired water vapour. On sunny days, as the air temperature and mixing ratio rose from predawn to morning, the atmospheric water vapour δ18O increased by 1‰ to 5‰ and then decreased by about 2‰ from morning to afternoon with the mixing ratio. On cloudy days, by contrast, the afternoon decrease in δ18O and the mixing ratio was not observed. These results show that water vapour that transpired from plants, with higher δ18O than the atmospheric water vapour, contributes to the increase in δ18O in the morning, whereas water vapour in the free atmosphere, with lower δ18O, contributes to the decrease in the afternoon on sunny days. The observed results reveal the significance of transpired water vapour, with relatively high δ18O, in the water cycle on a short diurnal time scale and confirm the importance of the recycling of precipitation through transpiration in continental forest environments such as the eastern Siberian taiga. © 2012 John Wiley & Sons, Ltd.

Krylova T.L.,RAS Institute of Geology and Mineralogy | Pandian M.S.,Pondicherry University | Bortnikov N.S.,RAS Institute of Geology and Mineralogy | Anand S V.,Pondicherry University | And 3 more authors.
Geology of Ore Deposits | Year: 2012

Formation conditions of orebodies and conditions of wolframite deposition at the Degana tungsten deposits in Rajasthan, India and the Tigrinoe tin-tungsten deposit in the Russian Far East were studied. Differences in the composition and state of fluid systems were established by microthermometric study of fluid inclusions (FI) and thorough petrographic examination of FI. At the Degana deposit, the ore veins in granite were formed from K-Na-Ca-(Mg, Fe, etc.) chloride solutions with a salinity up to 36 wt % NaCl equiv at a temperature of >420 to 120°C and under a pressure reaching 1550 bar. The formation temperature of the orebodies hosted in breccia reached 450°C and pressure was below 400 bar. The salinity of mainly Nachloride aqueous solutions was no higher than 18 wt % NaCl equiv. At the Tigrinoe deposit, the temperature during formation of quartz-wolframite-cassiterite veins varied from 420 to 240°C and the pressure was no higher than 300 bar. The salt concentration of Na-chloride solutions was 7-3 wt %. Wolframite crystallized at the very beginning of ore deposition. Probable sources of fluids are discussed. It is suggested that the factors controlling wolframite deposition could have been different even at the same deposit. © 2012 Pleiades Publishing, Ltd.

Dai S.,China University of Mining and Technology | Chekryzhov I.Y.,Far East Geological Institute | Chekryzhov I.Y.,Far Eastern Federal University | Seredin V.V.,RAS Institute of Geology and Mineralogy | And 7 more authors.
Gondwana Research | Year: 2015

Metalliferous coal deposits, mainly hosting Zr(Hf)-Nb(Ta)-REE and U(Mo,Se)-REE ores, in East Asia (Primorye of Russia and South China) primarily result from the evolution of plumes ascending from deep mantle and/or asthenospheric flows, both of which incorporate some reworking of the continental crust. This mantle-crust interaction not only led to coal-basin formation but also played a significant role in extensive volcanism and ore-generating hydrothermal activity. Three mineralization styles are identified in these deposits: tuffaceous, hydrothermal-fluid, and mixed tuffaceous-hydrothermal types. The tuffaceous Zr(Hf)-Nb(Ta)-REE deposits have source magmas with an alkali basalt composition, although felsic, mafic, and intermediate types of tuffaceous horizons have been identified in the study area. The mineralization occurred not only in the coal but also in the host rocks, and not only during peat accumulation but also during the later stages of coal development (including coalification and late epigenetic processes). Rare metals in the metalliferous coal deposits are generally either associated with clay and organic matter or occur as secondary minerals derived from decomposition of the primary magmatic rare-metal bearing minerals (e.g. Nb-bearing rutile) under the influence of organic acids and hydrothermal fluids. © 2015 International Association for Gondwana Research.

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