A study of outburst activity of Z and in 2000–2010

We present the results of our study of the classical symbiotic star Z And during its period of activity in 2000–2010. In this period, the system experienced a series of six outbursts, for three of which high-resolution spectra were obtained and analyzed. These observations provided information about the system’s behavior during the entire activity period, rather than during an individual outburst. In particular, we found a fundamental difference between the first outburst, which initiated the activity period, and subsequent outbursts, namely, the presence of bipolar collimated optical outflows for some of the outbursts. We propose a model that can explain all the spectroscopic phenomena observed during this series of outbursts, as well as previous series of outbursts of Z And, and suggest that similar scenarios may be valid for other classical symbiotic stars.     

Mantle and crustal sources of Archean anorthosite: a combined in situ isotopic study of Pb–Pb in plagioclase and Lu–Hf in zircon

Isotopic analyses of ancient mantle-derived magmatic rocks are used to trace the geochemical evolution of the Earth’s mantle, but it is often difficult to determine their primary, initial isotope ratios due to the detrimental effects of metamorphism and secondary alteration. We present in situ analyses by LA-MC-ICPMS for the Pb isotopic compositions of igneous plagioclase (An_75–89) megacrysts and the Hf isotopic compositions of BSE-imaged domains of zircon grains from two mantle-derived anorthosite complexes from south West Greenland, Fiskenæsset and Nunataarsuk, which represent two of the best-preserved Archean anorthosites in the world. In situ LA-ICPMS U–Pb geochronology of the zircon grains suggests that the minimum crystallization age of the Fiskenæsset complex is 2,936 ± 13 Ma (2σ, MSWD = 1.5) and the Nunataarsuk complex is 2,914 ± 6.9 Ma (2σ, MSWD = 2.0). Initial Hf isotopic compositions of zircon grains from both anorthosite complexes fall between depleted mantle and a less radiogenic crustal source with a total range up to 5 ε_Hf units. In terms of Pb isotopic compositions of plagioclase, both anorthosite complexes share a depleted mantle end member yet their Pb isotopic compositions diverge in opposite directions from this point: Fiskenæsset toward a high-μ, more radiogenic Pb, crustal composition and Nunataarsuk toward low-μ, less radiogenic Pb, crustal composition. By using Hf isotopes in zircon in conjunction with Pb isotopes in plagioclase, we are able to constrain both the timing of mantle extraction of the crustal end member and its composition. At Fiskenæsset, the depleted mantle melt interacted with an Eoarchean (~3,700 Ma) mafic crust with a maximum ¹⁷⁶Lu/¹⁷⁷Hf ~0.028. At Nunataarsuk, the depleted mantle melt interacted with a Hadean (~4,200 Ma) mafic crust with a maximum ¹⁷⁶Lu/¹⁷⁷Hf ~0.0315. Evidence from both anorthosite complexes provides support for the long-term survival of ancient mafic crusts that, although unidentified at the surface to date, could still be present within the Fiskenæsset and Nunataarsuk regions.     

Characteristics and causes of changes in annual runoff of the Wuding River in 1956–2009

The Yellow River is the second largest river in China. Its runoff experienced rapid changes in the past decades. The trend and driving forces of change of the river’s runoff has been a hot topic in some academic fields in China in recent years, due to its importance in solving the contradiction between supply and demand of water resources, reasonable exploitation and utilization of water resources and its significance in promoting the social, economic and ecologically sustainable development. The Wuding River is one of the large tributaries in the Middle Yellow River and soil and water conservation measures have been implemented in the tributary much earlier. It can be a good example for investigating the trend and causes of changes of runoff of the Yellow River. In this paper, the variation trend and abrupt change are determined in the time series of annual runoff of the Wuding River recorded at a hydrological station near its outlet during the period from 1956 to 2009 using several time series analysis methods. Secondly, the influences of climate change and human activities are estimated through calculating the amount of runoff reduction due to climate change in different periods. Results show that the annual runoff was continually decreasing, the drought trend was aggravating, and abrupt change in runoff series appeared in 1971 and 1997 as a result of large scale water and soil conservation measure after 1971 and ecosystem restoration program since 1997. It is also found that human activities were the main influence factor for runoff reduction during the period from 1972 to 2009. The contributions from climate change increased from about 23 to 30 %, and those from human activities decreased from 77 to 70 % from the period of 1972–1996 to the period of 1997–2009. Finally, a formula is built to reveal the relation of runoff with both climate factors and each main kind of human activities.     

Transport and Crystallization of Noble Platinum in Supercritical C–O–H Fluid

Experimental data is provided for the transport of platinum in a supercritical C–O–H fluid system. The transfer of platinum in space with its condensation on the surface of native carbon (diamond and amorphous carbon) in the form of micro- and nanocrystals, shapeless particles, and filamentous formations is established for the first time. The dominant participation of platinum in the formation of carbon micro- and nanotubes is demonstrated. The results are important in modeling the formation of noble metal deposits with deep fluid carbon systems.     

Formation of gold–silver sulfides and native gold in Fe–Ag–Au–S system

We carried out experiments on crystallization of Fe-containing melts FeS₂Ag_0.1–0.1xAu_0.1x (x = 0.05, 0.2, 0.4, and 0.8) with Ag/Au weight ratios from 10 to 0.1. Mixtures prepared from elements in corresponding proportions were heated in evacuated quartz ampoules to 1050 ºC and kept at this temperature for 12 h; then they were cooled to 150 ºC, annealed for 30 days, and cooled to room temperature. The solid-phase products were studied by optical and electron microscopy and X-ray spectroscopy. The crystallization products were mainly from iron sulfides: monoclinic pyrrhotite (Fe_0.47S_0.53 or Fe₇S₈) and pyrite (Fe_0.99S_2.01). Gold–silver sulfides (low-temperature modifications) are present in all synthesized samples. Depending on Ag/Au, the following sulfides are produced: acanthite (Ag/Au = 10), solid solutions Ag_2–xAu_xS (Ag/Au = 10, 2), uytenbogaardtite (Ag/Au = 2, 0.75), and petrovskaite (Ag/Au = 0.75, 0.12). They contain iron impurities (up to 3.3 wt.%). Xenomorphic micro- (<1–5 μm) and macrograins (5–50 μm) of Au–Ag sulfides are localized in pyrite or between the grains of pyrite and pyrrhotite. High-fineness gold was detected in the samples with initial ratio Ag/Au ≤ 2. It is present as fine and large rounded microinclusions or as intergrowths with Au–Ag sulfides in pyrite or, more seldom, at the boundary of pyrite and pyrrhotite grains. This gold contains up to 5.7 wt.% Fe. Based on the sample textures and phase relations, a sequence of their crystallization was determined. At ~1050 ºC, there are probably iron sulfide melt L₁ (Fe,S ? Ag,Au), gold–silver sulfide melt L₂ (Au,Ag,S ? Fe), and liquid sulfur L_S. On cooling, melt L₁ produces pyrrhotite; further cooling leads to the crystallization of high-fineness gold (macrograins from L₁ and micrograins from L₂) and Au–Ag sulfides (micrograins from L₁ and macrograins from L₂). Pyrite crystallizes after gold–silver sulfides by the peritectic reaction FeS + L_S = FeS₂ at ~743 ºC. Elemental sulfur is the last to crystallize. Gold–silver sulfides are stable and dominate over native gold and silver, especially in pyrite-containing ores with high Ag/Au ratios.     

Urban growth and quality of life: inter-district and intra-district analysis of housing in NCT-Delhi, 2001–2011–2020

One out of three people in India is urban. In 2011, there were about 53 urban agglomerations larger than 1 million population as against only 35 in 2001. Much of this urban expansion has been occurring in the country’s largest metropolises including the National Capital Territory of Delhi which has expanded horizontally and vertically both. This has also added to overall decline in its already dilapidated housing stock and quality of life. Delhi, a historical hub for regional, national, and international commerce, and a place for the socio-political elites, has failed to provide basic life amenities to its average citizens. This research critiques the (un)sustainable elements of Delhi’s urbanization and concomitant decline in basic amenities pertaining to quality-of-life by examining the growth and expansion of its urban-built-up areas during 2001–2011–2020 and provides nuanced insights into its ‘livability’ by examining select quality-of-life attributes. The LANDSAT imageries for 2010 and 2020 are used to measure NDB-Index that assesses its built-up area and change, which are later corroborated with Census household data to examine change in its ‘livable’ and ‘dilapidated’ housing structures. Significant sub-regional disparity exists in the availability of good and livable homes, with almost 20–30% of several districts still without drinking water source inside premises. However, significant progress is also noted for basic amenities like lighting, latrine and bathing facilities, and majority of Delhi’s built-up area has expanded along newer developments and transportation corridors. This calls for goal-oriented strategic interventions by policymakers to help achieve the SDG-11 on Sustainable Cities.

     

Secondary alterations of globular and platy phyllosilicates of the glauconite–illite series in the Precambrian and Vendian–Cambrian rocks

Previously published and new data on secondary transformations of the globular and platy phyllosilicates of the glauconite–illite series from the Upper Proterozoic terrigenous rocks of the Olenek and Anabar uplifts (East Siberia), Srednii Peninsula (Murmansk coast), and Vendian–Cambrian boundary rocks of the Podolian Dniester area (Ukraine) are generalized for the first time. Plastic deformation, aluminization, chloritization, berthierinization, as well as replacement of phyllosilicates of different morphology by corrensite- chlorite and pyrite at different lithogenesis stages, are considered and lithological-mineralogical characteristics of the glauconite-bearing rocks are reported. The structural, crystal-chemical, genetic, and isotopegeochronological features of di- and trioctahedral phyllosilicates are discussed.     

Visible and “invisible” forms of gold and silver in the crystallization products of melts in the Fe–S–Ag–Au system: experimental data

The forms of Au and Ag occurrence in the crystallization products of melts in the Fe–S–Ag–Au system depending on the proportions of Fe/S and Ag/Au have been studied at (Fe + S)/(Ag + Au) = 0.1. It is shown that the S-rich systems with S/Fe = 2 contain Au–Ag sulfides and Au–Ag alloys. The systems depleted in S with S/Fe = 1 contain only Au–Ag alloys. The results of XPS provide evidence for the sulfide and metallic components of Au and Ag among the crystallization products of melts in the system studied at S/Fe = 2 and a metallic component with S/Fe = 1. According to the data of electron microprobe analysis, the content of “invisible” forms of noble metals in pyrite and pyrrhotite is < 0.024 wt % for Au and <0.030 wt % for Ag; the contents of “invisible” Au and Ag in troilites are 0.040 ± 0.013 wt % Au and 0.079 ± 0.016 wt % Ag.     

Rb–Sr and Sm–Nd study of granite–charnockite association in the Pudukkottai region and the link between metamorphism and magmatism in the Madurai Block

Pudukkottai region in the northeastern part of the Madurai Block exposes the garnetiferous pink granite that intruded the biotite gneiss. Charnockite patches are associated with both the rock types. Rb–Sr biotite and Sm–Nd whole-rock isochron ages indicate a regional uplift and cooling at ～550 Ma. The initial Nd isotope ratios (\(\varepsilon _{\text {Nd}}^{\mathrm {t}}=-20\) to ?22) and Nd depleted-mantle model ages (T_DM = 2.25 to 2.79 Ga) indicate a common crustal source for the pink-granite and associated charnockite, while the biotite gneiss and the charnockite within it represent an older crustal source (\(\varepsilon _{\text {Nd}}^{\mathrm {t}}= -29\) and T_DM = > 3.2 Ga). The Rb–Sr whole-rock data and initial Sr–Nd isotope ratios also help demonstrate the partial but systematic equilibration of Sr isotope and Rb/Sr ratios during metamorphic mineral-reactions resulting in an ‘apparent whole-rock isochron’. The available geochronological results from the Madurai Block indicate four major periods of magmatism and metamorphism: Neoarchaean–Paleoproterozoic, Mesoproterozoic, mid-Neoproterozoic and late-Neoproterozoic. We suggest that the high-grade and ultrahigh-temperature metamorphism was preceded by magmatism which ‘prepared’ the residual crust to sustain the high P–T conditions. There also appears to be cyclicity in the tectono-magmatic events and an evolutionary model for the Madurai Block should account for the cyclicity in the preserved records.     

Patterns and Scales of Phytoplankton Variability in Estuarine–Coastal Ecosystems

Phytoplankton variability is a primary driver of chemical and biological dynamics in the coastal zone because it directly affects water quality, biogeochemical cycling of reactive elements, and food supply to consumer organisms. Much has been learned about patterns of phytoplankton variability within individual ecosystems, but patterns have not been compared across the diversity of ecosystem types where marine waters are influenced by connectivity to land. We extracted patterns from chlorophyll-a series measured at 84 estuarine–coastal sites, using a model that decomposes time series into an annual effect, mean seasonal pattern, and residual “events.” Comparisons across sites revealed a large range of variability patterns, with some dominated by a recurrent seasonal pattern, others dominated by annual (i.e., year-to-year) variability as trends or regime shifts and others dominated by the residual component, which includes exceptional bloom events such as red tides. Why is the partitioning of phytoplankton variability at these three scales so diverse? We propose a hypothesis to guide next steps of comparative analysis: large year-to-year variability is a response to disturbance from human activities or shifts in the climate system; strong seasonal patterns develop where the governing processes are linked to the annual climate cycle; and large event-scale variability occurs at sites highly enriched with nutrients. Patterns of phytoplankton variability are therefore shaped by the site-specific relative importance of disturbance, annual climatology, and nutrient enrichment.     

Factors and Trends in the Formation of Natural–Technogenic Associations of Polycyclic Aromatic Hydrocarbons in the Snow–Soil System

Doklady Earth Sciences - The content of polycyclic aromatic hydrocarbons (PAHs) in soil and snow cover near the carbon black plants in Moscow, Omsk, and Samara regions was studied. The differences...     

Geochemical characteristics of selected elements in iron–manganese cutans and matrices of Alfisols in central China

The elemental geochemistry of major, minor and trace elements in iron–manganese cutans and the corresponding matrix soils, collected from three Alfisols in central China, are studied using their chemical compositions as well as correlation and factor analyses. Fe–Mn cutans accumulate high concentrations of MnO₂ and Fe₂O₃. Mean values of these two elements in cutans are about 13.7 and 1.4 times higher than those in the matrix soils. pH, clay contents, extractable X-ray noncrystalline Fe (Feo) and the ratio of Feo to free Fe-oxide (Fed) in cutans are notably higher than those in the corresponding matrices. Cutans are also enriched in some bases and heavy metals. Averages of K, Na, Co and Pb concentrations are about 2.0, 1.4, 15.4 and 6.0 times higher than those in the matrices. Statistical analysis indicates that Co, Ni, Li, Cu and Zn are abundant in Mn minerals of cutans, while Pb exists mainly in iron minerals. Fe–Mn cutans constitute an active microzone of solid–solution–plant–air interaction, element movement and exchange in soils, which cause the contents of Fe- and Mn-oxides, elemental concentrations, and geochemical behavior of cutan to show marked differences in matrix soils.     

Formation of the disk structure and jets in the symbiotic system Z and during periods of activity in 2006–2010

We present an analysis of spectrophotometric observations of the latest cycle of activity of the symbiotic binary Z And from 2006 to 2010. We estimate the temperature of the hot component of Z And to be ≈150 000−170 000 K at minimum brightness, decreasing to ≈90 000 K at the brightness maximum. Our estimate of the electron density in the gaseous nebula is N _e = 10¹⁰−10¹² cm⁻³ in the region of formation of lines of neutral helium and N _e = 10⁶−10⁷ cm⁻³ in the region of formation of the [OIII] and [NeIII] nebular lines. A trend for the gas density derived from helium lines to increase and the gas density derived from [OIII] and [NeIII] lines to simultaneously decrease with increasing brightness of the system was observed. Our estimates show that the ratios of the theoretical and observed fluxes in the [OIII] and [NeIII] lines agree best when the O/Ne ratio is similar to its value for planetary nebulae. The model spectral energy distribution showed that, in addition to a cool component and gaseous nebula, a relatively cool pseudophotosphere (5250–11 500 K) is present in the system. The simultaneous presence of a relatively cool pseudophotosphere and high-ionization spectral lines is probably related to a disk-like structure of the pseudophotosphere. The pseudophotosphere formed very rapidly—over several weeks—during a period of increasing brightness of Z And. We infer that in 2009, as in 2006, the activity of the system was accompanied by a collimated bipolar ejection of matter (jets). In contrast to the situation in 2006, the jets were detected even before the system reached its maximum brightness. Moreover, components with velocities close to 1200 km/s disappeared at the maximum, while those with velocities close to 1800 km/s appeared.     

Characteristics of selenium migration in soil–plant system of East Meshchera and Transbaikalia

Herein some results of comparative researches to determine the parameters of selenium migration in meadow biogeocenoses of East Meshchera and East Transbaikalia are presented. The parameters of selenium mobility in soils (i.e., the element total content, plant-accumulation coefficient (Kb) and/or mobile form ratio) in Urov biogeochemical provinces of the East Transbaikalia are quite comparable to the element migration parameters found in selenium-deficient landscapes of the same area. Selenium mobility indices and ecological status are significantly higher for meadow biogeocenoses of the East Meshchera (Moscow Region) and also for limestone soils.     

Spatiotemporal distribution of flood disasters in Asia and influencing factors in 1980–2019

Natural Hazards - Floods are common natural disasters in Asia. Flood datasets from 48 countries in Asia were collected to investigate the spatiotemporal distribution and influencing factors, using...     

Timing of Back–Arc Spreading of the Paleozoic Island Arc of the Urals: Implication of Sm–Nd and U–Pb Dating of Dolerites and the Composition of Inclusions in Zircon

Doklady Earth Sciences - Dolerites of the parallel dikes formed in a back-arc spreading setting have been dated by Sm–Nd to the Silurian (426 ± 34 Ma) for Mount Azov in the Central...     

Distribution of indium in ores of some base metal and tin–sulfide deposits in Siberia and the Russian Far East

The study of base-metal massive sulfide and tin–sulfide deposits in Siberia and the Russian Far East has revealed that the indium content in ores exceeding the average statistical value at similar deposits worldwide could be economically important. Sphalerite and chalcopyrite and chalcopyrite, bornite, and sphalerite are the major indium carriers in the base-metal massive sulfide and tin–sulfide ores, respectively. In addition, base-metal massive sulfide ores have high Cd, Ag, and Te contents, whereas tin–sulfide ores have elevated Ge, Ga, and Nb contents. This has stimulated the investment attractiveness of these deposits.     

Historical and contemporary aspects of pluriactivity in the Curvature Sub–Carpathians of Romania

This paper focuses on the Curvature Sub–Carpathians, especially with respect to Buzau County. The region as a whole has always been relatively well-settled and agriculture has usually been combined with a range of local industrial and handicraft employments. A study of traditional domestic activities brings out a close connection between specific natural resources and characteristic features of traditional peasant household work. The Prahova Valley has been particularly favoured on account of the oil industry and a major transport axis connecting Bucharest with Brasov via Ploiesti, but elsewhere industry did not spread extensively beyond the county centres (Buzau, Focsani, Pitesti and Targoviste) and their immediate environs such as Colibasi and Doicesti. During the present transition phase the rural population is struggling to survive by combining elements of the modern and traditional economies. The main rural centres are relatively well off while the outlying villages are experiencing severe poverty problems. Apart from brandy distilling, traditional rural industries are no longer viable, although alternative systems of pluriactivity are under discussion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Geochemical features of gold–quartz veins in granitoid intrusives and terrigenous masses of the Yana–Kolyma folded belt in the northeast of Russia

The main task of this study was to reveal geochemical and distinctive features of gold–quartz vein ores of deposits in granitoid intrusive bodies and in terrigenous black-schist masses of the Yana-Kolyma folded belt. The results obtained point to the significant role of metamorphism of the enclosing terrigenous carbonaceous masses in ore formation of both types of deposits. The established facts are not contradictory to the metamorphic–magmagene model of the formation of gold deposits in the Yana–Kolyma belt. The geochemical similarity of both types of deposits shows that these are products of the same orogenic system, which confirms the validity of combining these deposits to form a unified gold–quartz formation.