The Kotuikan ring structure as possible evidence for a large impact event in the northern Siberian craton

Remote-sensing, cosmogeological, tectonic, geophysical, structural, compositional, isotopic, and geochronological criteria permit identifying the Kotuikan ring structure in the northern Siberian Platform as a Paleoproterozoic large astrobleme, close in age to the Vredefort and Sudbury impact structures. Also, indirect evidence for two more large impact structures was obtained here. This confirms widely hypothesized massive bombardment of the early Earth by asteroids and a possible effect of large impact events on the Earth's mantle dynamics and rotation regime, that is, the tectonic evolution of our planet, including plate tectonics.     

The Gagarka gold deposit in the central Urals, Russia

The Gagarka gold deposit was formed in two stages. The gold-telluride ore of the main early stage was formed ～260 Ma ago synchronously with Permian collision, which was accompanied by retrograde metamorphism with mobilization of Au and Te from geochemically similar massive sulfide lodes in the rift zone. The Au-bearing argillic metasomatic rocks of the late stage presumably Mesozoic in age are distinguished by specific geochemistry and locally superposed on the ore related to the early stage. The upper part of the metasomatic column consists of quartz-kaolinite rock, which is confused in many cases with products of Mesozoic-Cenozoic weathering and because of this is not perceived as a guide for hidden Au-bearing argillic alteration, whose resource potential remains underestimated in the Urals.     

High-magnesium picrite–basalt associations of the Tunka terrane (Baikal–Hövsgöl region) as an indicator of the back-arc basin spreading

High-Mg metabasalts and metapicrites discovered within the Urtagol Formation in the central zone of the Tunka bald mountains (East Sayan) are studied. In geochemistry the high-Mg metavolcanics are similar to subductional rocks. We have established that the Nb-rich recycled material of oceanic crust (RSC) was a source of elements for high-Ti metabasalts, and subductional fluid rich in LREE and Th relative to Nb was the source of these elements for high-Ti metapicrites. The enrichment of low-Ti metavolcanics, formed, probably, at the early stages of the basin opening, was due to the contamination of melt with continental-crust material. A comparison of the metavolcanics with nonmetamorphosed analogs is made, and some genesis aspects are considered. The results obtained led to the conclusion that the metavolcanics mark the paleospreading of the back-arc basin.     

Paleoenvironmental reconstruction of the Early to Middle Miocene Central Paratethys using stable isotopes from bryozoan skeletons

Stable carbon and oxygen isotope values from single bryozoan colonies were used to reconstruct the paleoenvironments of the Early to Middle Miocene (Ottnangian to Badenian) sediments of the Central Paratethys. This approach utilizes a locally abundant allochem while avoiding matrix and multiple allochem contamination from bulk rock samples. Bryozoan colonies (and a few foraminifera and rock matrix samples) from 14 localities yielded 399 carbon and oxygen isotope values. Data from six of the localities (15 % of the total number of samples) were interpreted as having been diagenetically altered and were rejected. The remaining data indicate a primarily localized upwelling signal with lesser variation caused by global climatic and regional tectonic forcing of sea level, salinity, and temperature. Paleotemperatures were calculated to range from 12 to 21 °C. Despite potential taxonomic and diagenetic problems, bryozoan colonies are a powerful, underutilized source of paleoenvironmental carbon and oxygen isotope data.     

Early Carboniferous (Viséan) emplacement of the collisional Kłodzko–Złoty Stok granitoids (Sudetes, SW Poland): constraints from geochemical data and zircon U–Pb ages

Sensitive high-resolution ion microprobe zircon U–Pb dating and geochemical data of igneous rocks from the composite K?odzko–Z?oty Stok (KZS) Granite Pluton, Sudetic Block, indicate that the granitoids represent an Early Carboniferous Viséan phase of Variscan metaluminous, high-K, I-type, syn-collisional granite magmatism within the Saxothuringian Zone of the Central European Variscides. Igneous zircon records hypabyssal magmatism that produced various granitoids and lamprophyre (spessartite) emplaced from ca. 340 to 331 Ma. The KZS granitoids have compositions ranging from granodiorite to monzonite, low A/CNK ratios (<1), and are associated with abundant mafic members. Most of them are alkaline, highly potassic, and moderately evolved. The major and trace element contents of the KZS granitoids suggest geochemical heterogeneity, and the hybrid nature of magmas derived from a range of sources in the middle crust, with a strong input of material from the upper mantle. Mixing of magmas of mantle origin with high-K material from partly melted continental crust was probably a more important factor than fractional crystallization, in controlling the evolution of the magmas. The mean Pb–U ages of the main population of igneous zircon from a quartz monzodiorite (?elazno) and hornblende monzonite (Droszków) are 340.2 ± 2.5 Ma and 339.5 ± 3.1 Ma, respectively. A slightly younger biotite-hornblende granodiorite from Chwalis?aw, 336.7 ± 2.5 Ma, was cut by a spessartite dyke at 333.1 ± 3.1 Ma. This indicates that mafic magmas were immediately intruded into fractured, probably incompletely solidified, granodiorites. The lamprophyric dyke also contains igneous zircon of Neoproterozoic age, 566.3 ± 6.4 Ma, typical of the crust in the Saxothuringian Zone. Tonalite from Ptasznik Hill near Droszków is of similar age to the spessartite, 331.5 ± 2.6 Ma. High REE contents in the tonalite and its igneous zircon indicate advanced differentiation of granitic magma, producing a more leucocratic melt associated with post-magmatic activity including abundant late crosscutting pegmatites and quartz veins, and contact metasomatic mineralization. The KZS granitoids have rather similar petrographic and geochemical characteristics to granitoids from other parts of the Central European Variscides, where a thickened orogenic root caused a substantial rise in crustal temperatures, producing granitoid magmas closely correlated with regional tectonic activity between the Saxothuringian and Brunovistulia Terranes at the NE margin of the Bohemian Massif.     

Effects of inhibitors on ferricyanide uptake and assimilation by plants

Effects of inhibitors on uptake and assimilation of ferricyanide by different plants were investigated. Detached roots of plants were kept in a closed-dark hydroponic system with ferricyanide solution amended with various inhibitors. Dissociation of ferricyanide to free cyanide and iron in solution was negligible. The application of inhibitors affected both botanical assimilation and uptake of ferricyanide. Of the inhibitors tested, silver nitrate showed a significantly inhibitory effect on ferricyanide uptake by rice, soybean and maize (P < 0.01), while a negligible effect was found in willows spiked with the same inhibitor (P > 0.05). However, lanthanum chloride showed the most severe effect on botanical assimilation of ferricyanide by maize and rice (P < 0.01), whereas silver nitrate and tetraethylammonium chloride were the most sensitive inhibitors to soybean and willows, respectively (P < 0.01). Botanical assimilation of ferricyanide was observed positively in responses to temperatures, in which maize was more susceptible than other selected plants. In conclusion, application of inhibitors has a substantial influence on the uptake and assimilation of ferricyanide by plants, and the inhibitory efficiency is highly dependent on the species of inhibitors applied.     

High-resolution profiles of iron, manganese, cobalt, cadmium, copper and zinc in the pore water of estuarine sediment

The remobilization of iron, manganese, cobalt, cadmium, copper and zinc in the pore water of estuarine sediment cores at Yingkou was assessed using diffusive equilibrium in thin films and diffusive gradients in thin films techniques. A relatively anoxic system (+33.7 to ?224.1 mV) in the sediment cores might cause the reductive release of iron, manganese and cobalt into pore water from the estuarine sediment. High-average concentrations of iron (47.85 μg ml^?1) and manganese (3.81 μg ml^?1) were observed using diffusive equilibrium in thin films on the sediment core, but the concentration of cobalt (18.02 ng ml^?1) was relatively low. A strong correlation between iron and cobalt was observed based on the vertical profiles of the metals. Manganese and iron were more readily released from the solid phase to the solution. The peak cobalt, copper and zinc concentrations were observed in the upper layer (2–4 cm) measured using diffusive gradients in thin films. However, the peak iron, manganese and cobalt concentrations were located in the deeper layer (≥7 cm). In addition, the concentration profiles measured using diffusive gradients in thin films of cobalt, copper and zinc were independent of the iron, manganese and cobalt distribution with respect to depth.     

Levels, seasonal variations, and health risks assessment of ambient air pollutants in the residential areas

People living in the urban area and the surrounding suburban area have disparities in exposure and health risks due to different levels of ambient air pollutants. The main objective of this study is to investigate the concentrations, seasonal variations, and related health risks of ambient air pollutants (PM₁₀, NO₂, and SO₂) in urban and suburban areas of Ningbo, China. The results showed that the average PM₁₀, NO₂, and SO₂ concentrations in the urban area were 85.2, 49.3, and 37.4 μg/m³, which were 1.13, 1.25, and 1.41 times the values of the suburban area during the period of March 2009 to February 2010. For the potential health risk analysis, the residents have been divided into four age categories namely, infants, children (1 year), children (8–10 years), and adults. The analysis took into account age-specific breathing rates, body weights for different age categories. The results showed that the potential health risks to respiratory disease for all age categories living in urban area were higher than those in suburban area.     

Practical estimation and distribution of diffuse pollutants arising from a watershed in Turkey

This study presents the diffuse pollution profile of a coastal watershed with respect to the dominating sector of agriculture including forestry. A rough estimation of the diffuse loads expressed by two major nutrients of nitrogen and phosphorous is realized by calculations based on unit loads obtained from the literature for each land-use activity. The key concern is to rank the different diffuse loads arising from the watershed. The major diffuse nitrogen loads are estimated to arise from agricultural activities with 54 %, followed by livestock breeding that contribute to the nitrogen budget by 11 %. Almost 7 % of the nitrogen loads come from meadows and pasture, and 5 % from forests. In the distribution of diffuse phosphorus loads, it is estimated that 48 % of the loads arise from agricultural activities, and 18 % from livestock breeding. Almost 14 % of the phosphorous loads come from septic tank effluents; however, 13 % of the loads are due to rural run-off. The future loads for 2028 and 2039 are also estimated; 30–40 % decrease is foreseen in the agricultural pollutants and animal manure through the stepwise application of ecological agriculture and livestock breeding. The basic aim of this study is to put forth a practical methodology for estimating diffuse loads in a watershed for the decision-makers and local administrative authorities with especially limited available data. Through such, distribution of various diffuse loads becomes available among the administrative units composing the watershed.