Seasonal and Year-to-Year Variations of Phytoplankton Primary Production in the Rybinsk Reservoir: The Effect of Weather and Climate Variations

Water Resources - The seasonal and long-term dynamics of phytoplankton primary production has been studied in the Rybinsk Reservoir (Upper Volga) in 2005–2014. A positive correlation has been...     

Criteria for the detection of hydrothermal ecosystem faunas in ores of massive sulfide deposits in the Urals

The ore-formational, ore-facies, lithological, and mineralogical-geochemical criteria are defined for the detection of hydrothermal ecosystem fauna in ores of the volcanic-hosted massive sulfide deposits in the Urals. Abundant mineralized microfauna is found mainly in massive sulfide mounds formed in the jasperous basalt (Buribai, Priorsk, Yubileinoe, Sultanov), rhyolite–basalt (Yaman-Kasy, Blyava, Komosomol’sk, Sibai, Molodezhnoe, Valentorsk), and the less common serpentinite (Dergamysh) formations of the Urals (O–D2). In the ore-formational series of the massive sulfide deposits, probability of the detection of mineralized fauna correlates inversely with the relative abundance of felsic volcanic rocks underlying the ores. This series is also marked by a gradual disappearance of colloform pyrite, marcasite, isocubanite, pyrrhotite, and pyrite pseudomorphoses after pyrrhotite; increase of the amount of bornite, fahlores, and barite; decrease of contents of Se, Te, Co, and Sn in chalcopyrite and sphalerite; and decrease of Tl, As, Sb, and Pb in the colloform pyrite. Probability of the detection of mineralized fauna in the morphogenetic series of massive sulfide deposits decreases from the weakly degraded sulfide mounds to the clastic stratiform deposits. The degradation degree of sulfide mounds and fauna preservation correlates with the attenuation of volcanic intensity, which is reflected in the abundance of sedimentary and volcanosedimentary rocks and the depletion of effusive rocks in the geological sections.     

Asteroid identification using BTA images

We report the results of identification of the Main Belt asteroid 2006 HO 153 accidentally found during the observations of transneptunian objects in 1998. We briefly describe the technique of identification, where the use of change rates of spherical coordinates of the observed asteroid plays an important role.     

Sulfide minerals in the Menez Gwen nonmetallic hydrothermal field (Mid-Atlantic Ridge)

Mineralogy and geochemistry of the sulfide-bearing rocks and ores discovered in the Menez Gwen field are studied. Samples were taken during the expedition of the Shirshov Institute of Oceanology (cruise 49, R/V Akademik Mstislav Keldysh. The mineral composition of rocks and ores were studied by the traditional methods of optical microscopy, scanning electron microscopy (CAMSCAN), and microprobe analysis (EPMA SX-50). Contents of trace elements were determined by the laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). The Zn-Cu ore comprises zonal sulfide chimney intergrowths. Numerous Se-rich copper ore fragments occur in the volcanomictic layered gritstones and/or barite slabs. The mineral composition, zonality, and association of trace elements in ore are typical of “black smokers” formed at the basalt base near the Azores Triple Junction in the MAR. The results obtained make it possible to reconstruct formation history of the Menez Gwen hydrothermal field into the high-temperature (Cu-Se association in ore clasts), medium-temperature (Zn-Cu-As association in ore), and recent (Ba-SiO₂ association) stages.     

Holocene Environments of Anomalous Uranium Concentrations in Sediments of Syrytkul Lake (Southern Urals)

Doklady Earth Sciences - The influence of the Holocene sedimentation conditions on uranium accumulation in sediments in Syrytkul Lake has been studied. The comparison of geochemical, palynological,...