Results of U–Pb LA–ICP–MS dating of detrital zircons from Ediacaran–Early Cambrian deposits of the eastern part of the Baltic monoclise

Here we present the results of U–Pb LA–ICP–MS dating of detrital zircons from the Ediacaran–Early Cambrian deposits of the eastern part of the Baltic monoclise (Leningrad Region). The obtained age spectra of the detrital zircons suggest that, in the Ediacaran–Early Cambrian, the main clastic material source to the northwest of the Russian Platform was the Baltic Shield. Then in the Early Cambrian along with the Baltic Shield provenance, a clastic source from the Timanian margin of Baltica (northeast in modern coordinates) contributed to the deposits. The obtained data either somewhat set limits of the Timanian orogen formation as older than the previously suggested Middle Cambrian (about 510 Ma), based on the “absence of a Proto–Uralian–Timanian provenance signal” in the Sablino Formation rocks in the south Ladoga, or suggest another rearrangement of detritus transportation paths at the end of Stage 3 (Atdabanian).     

Fluxes of iron and manganese across the sediment–water interface under various redox conditions

Fluxes of dissolved forms of iron and manganese across the sediment–water interface were studied in situ in the Gulf of Finland and the Vistula Lagoon (Baltic Sea), and in the Golubaya Bay (Black Sea) from 2001 to 2005. Fluxes were measured using chamber incubations, and sediment cores were collected and sliced to assess the porewater and solid phase metal distribution at different depths. Measured and calculated benthic fluxes of manganese and iron were directed out of sediment for all sites and were found to vary between 70–4450 and 5–1000 µmole m^− 2 day^− 1 for manganese and iron, respectively. The behavior of the studied metals at various redox conditions in the near-bottom water and in the sediment was the main focus in this study. Our results show the importance of bottom water redox conditions for iron fluxes. We measured no fluxes at oxic conditions, intermediate fluxes at anoxic conditions (up to 200 μmole m^− 2 day^− 1) and high fluxes at suboxic conditions (up to 1000 μmole m^− 2 day^− 1). Total dissolved iron fluxes were generally dominated by iron(II). Contribution of iron(III) to the total iron flux did not exceed 20%. Obtained fluxes of manganese at all studied regions showed a linear correlation (r² = 0.97) to its concentration in the porewater of the top sediment layer (0–5 mm) and did not depend on dissolved oxygen concentrations of bottom water. Organically complexed iron and manganese were in most cases not involved in the benthic exchange processes.     

Assessing the efficiency of combined use of surface water and groundwater for process water supply to Kalininskaya NPP

The potential improvement of the reliability of process water supply system is discussed for the case of an important power facility with the use of combined water intake systems. Hydrological simulation is used to determine the deficiency periods of surface water resources and, accordingly, the period of involvement of subsurface compensation water intake. A hydrodynamic model is used to predict the damage to surface runoff caused by the operation of the groundwater intake. The results are used to prepare an operations schedule for the management of combined water intake system.     

WSO-UV—ultraviolet mission for the next decade

The World Space Observatory UltraViolet (WSO–UV) is an international space mission devoted to UV spectroscopy and imaging. The observatory includes a 170 cm aperture telescope capable of high-resolution and long slit low-resolution spectroscopy, and deep UV and optical imaging. The observatory is designed for observations in the ultraviolet domain where most of astrophysical processes can be efficiently studied with unprecedented capability.     

On the composition and differentiation of Ceres

The dwarf planet Ceres has a density of 2040-2250 kg m⁻³, and a dark non-icy surface with signs of hydrated minerals. As opposed to a differentiated internal structure with a nonporous rocky core and a water mantle, there are arguments for undifferentiated porous interior structure. Ceres’ mass and dimensions are uncertain and do not exclude undifferentiated interior even if hydrostatic equilibrium is attained. The rocky surface may be inconsistent with a large-scale water-rock differentiation. A differentiated structure with a thick water mantle below a rocky crust is gravitationally unstable and an overturn would have led to abundant surface salt deposits, which are not observed. A formation of hydrated surface minerals caused by internal heating implies a major density increase through devolatilization of the interior. A later accumulation of hydrated materials is inconsistent with anhydrous surfaces of many asteroids and with a low rate of the cosmic dust deposition in the inner Solar System. Ceres’ internal pressures (<140-200 MPa) are insufficient to significantly reduce porosity of chondritic materials and there is no need for abundant water phases to be present to account for the bulk density. Having the porosity of ordinary chondrites (∼10%), Ceres can consist of rocks with the grain density of pervasively hydrated CI carbonaceous chondrites. However, additional low-density phases (e.g., water ice) require to be present in the body with the grain density of CM chondrites. The likely low-density mineralogy of the interior implies Ceres’ accretion from pervasively aqueously altered carbonaceous planetesimals depleted in short-lived radionuclide ²⁶Al. Abundant water ice may not have accreted. Limited heat sources after accretion may not have caused major mineral dehydration leading to formation of water mantle. These inferences can be tested with the Dawn spacecraft in 2015.     

Glaciogenic and related sedimentary rocks: Main lithochemical features. Communication 2. The Paleozoic and Cenozoic

Lithochemical features of the Early-Late Paleozoic and Cenozoic glaciogenic and related sedimentary rocks around the world are considered. Comparison of the bulk chemical composition of diamictites with the average Post-Archean Australian Shale (PAAS) revealed that the diamictites do not show any lithochemical characteristics unambiguously indicating their formation under cool climatic conditions. The chemical index of alteration (CIA) often used in the paleoclimatic reconstructions should be considered as additional (though very important) tool, because it is controlled by local factors. Taking into account these facts, there are likely no grounds to expect that the amount of the redeposited sedimentary material in the Late Paleozoic and Cenozoic glaciogenic rocks is more than in their Early Proterozoic and Late Riphean-Vendian analogues.     

Clarkes of concentrations of trace elements in the Riphean fine-grained terrigenous rocks of the Uchur-Maya region and the Yenisei Range

The clarkes of concentrations (K_c) of a wide range of trace elements (Li, Be, B, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In, Sb, Cs, Ba, REE, Hf, Ta, Hg, Tl, Pb, Bi, Th, and U) were analyzed for fine-gained terrigenous rocks (mudstones, metapelites) from the reference Riphean sections of the Uchur-Maya region and the Yenisei Range. It was established that the shales and mudstones of the Uchur and Aimchan groups in the Riphean hypostratotype section are characterized by moderate (2.5 < K_c < 5) and intense (K_c > 5) geochemical specialization for Li, B, and Zn. At the same time, the similar rocks of the Lakhanda and Ui groups do not exhibit any distinct geochemical specialization, although they are notably enriched in HREE. The metapelites from the basal formations of the Riphean sedimentary successions in the Yenisei Range are distinctly specialized for B and slightly for Li, Rb, Be, Nb, Ta, Th, Ge, and Cd. In addition, moderate specialization for Cu is characteristic of the metapelites from the Korda and Lopatino formations; for Bi, Sb, Hg, and V, for their analogs from the Potoskui Formation; and, for Hg and Cs, for the similar rocks from the Lopatino Formation. The metapelites of the Lower Riphean Korda Formation from the central zone of the Yenisei Range have elevated contents of significantly more elements (Li, Be, Sc, V, Cr, Co, Ni, Zn, As, Rb, Y, Zr, Nb, Sb, Ag, In, Hf, Hg, and others) than their counterparts from its eastern near-platform part. The mudstones of the ore-bearing (Pb, Zn) Gorevo Formation are characterized by elevated concentrations of several ore elements such as Pb, Cd, As, Sb, and Bi. The elevated K_c values of the rare lithophile and of several ore elements in the metapelites of the Yenisei Range are determined by the high geochemical differentiation of the Early Precambrian blocks constituting the western margin of the Siberian Craton, which were eroded in the Riphean, and the syn-sedimentary riftogenic and intraplate magmatism. On the contrary, the fine-grained and terrigenous rocks from the basal part of the Riphean section in the Uchur-Maya region are compositionally closer to the immature Late Archean substrates or their Early Proterozoic analogs.