Multitransition study and new detections of class II methanol masers     

Dinah M. Cragg  rej M. Sobolev  Simon P. Ellingsen  J. L. Caswell  Peter D. Godfrey  Svetlana V. Salii  Richard G. Dodson 《Monthly notices of the Royal Astronomical Society》2001,323(4):939-951

We have used the ATNF Mopra antenna and the SEST antenna to search in the directions of several class II methanol maser sources for emission from six methanol transitions in the frequency range 85–115 GHz. The transitions were selected from excitation studies as potential maser candidates. Methanol emission at one or more frequencies was detected from five of the maser sources, as well as from Orion KL. Although the lines are weak, we find evidence of maser origin for three new lines in G345.01+1.79, and possibly one new line in G9.62+0.20.
The observations, together with published maser observations at other frequencies, are compared with methanol maser modelling for G345.01+1.79 and NGC 6334F. We find that the majority of observations in both sources are consistent with a warm dust (175 K) pumping model at hydrogen density ∼10⁶ cm⁻³ and methanol column density ∼ 5×10¹⁷ cm⁻². The substantial differences between the maser spectra in the two sources can be attributed to the geometry of the maser region.  相似文献   

Petrogenesis of Na-rich paralava formed by methane flares associated with mud volcanism, Altyn-Emel National Park, Kazakhstan     

Rodney Grapes  Ella Sokol  Svetlana Kokh  Olga Kozmenko  Ilia Fishman 《Contributions to Mineralogy and Petrology》2013,165(4):781-803

High-Na slag-like rocks (paralava) with 4.5–11 % Na₂O from the Altyn-Emel mud volcanic field, Kazakhstan, are the products of melting of sediment + salt mixtures by methane flares associated with mud extrusion. The main minerals of the paralavas are diopside and wollastonite which have quench morphologies. Other high-temperature phases (crystallizing from melt and vapour phase) are tridymite, cristobalite, chlorapatite, alkali feldspar, pyrrhotite, native iron and silicon, iron phosphides, titanite, rutile, and carbon. The paralavas lack the Na–Ca silicates devitrite and combeite, but have high-Na and Na–K glasses that have not been homogenized despite low viscosities of <10^?3.5 Pa s. The large number of ignition foci in the Altyn-Emel mud volcano field indicates gas venting from small, shallow reservoirs. The methane flares are inferred to have been small and the fire events short-lived. Fires were extinguished once overpressure released during eruption, methane venting stopped and melted rocks rapidly quenched. The periodicity of eruptions and methane flaring most likely depends on the recurrence of earthquakes (M < 5) which are frequent in this tectonically active area.  相似文献   

Geology, mineralization, stable isotope geochemistry, and fluid inclusion characteristics of the Novogodnee–Monto oxidized Au–(Cu) skarn and porphyry deposit, Polar Ural, Russia     

Serguei G. Soloviev  Sergey G. Kryazhev  Svetlana S. Dvurechenskaya 《Mineralium Deposita》2013,48(5):603-627

The Novogodnee–Monto oxidized Au–(Cu) skarn and porphyry deposit is situated in the large metallogenic belt of magnetite skarn and Cu–Au porphyry deposits formed along the Devonian–Carboniferous Urals orogen. The deposit area incorporates nearly contemporaneous Middle–Late Devonian to Late Devonian–Early Carboniferous calc-alkaline (gabbro to diorite) and potassic (monzogabbro, monzodiorite- to monzonite-porphyry, also lamprophyres) intrusive suites. The deposit is represented by magnetite skarn overprinted by amphibole–chlorite–epidote–quartz–albite and then sericite–quartz–carbonate assemblages bearing Au-sulfide mineralization. This mineralization includes early high-fineness (900–990?‰) native Au associated mostly with cobaltite as well as with chalcopyrite and Co-pyrite, intermediate-stage native Au (fineness 830–860?‰) associated mostly with galena, and late native Au (760–830?‰) associated with Te minerals. Fluid inclusion and stable isotope data indicate an involvement of magmatic–hydrothermal high-salinity (>20 wt.% NaCl-equiv.) chloride fluids. The potassic igneous suite may have directly sourced fluids, metals, and/or sulfur. The abundance of Au mineralization is consistent with the oxidized character of the system, and its association with Co-sulfides suggests elevated sulfur fugacity.  相似文献   

Lacustrine sediments and lichen transplants: two contrasting and complimentary environmental archives of natural and anthropogenic lead in the South Urals, Russia     

Baruch Spiro  Valery Udachin  Ben J. Williamson  O. William Purvis  Svetlana G. Tessalina  Dominik J. Weiss 《Aquatic Sciences - Research Across Boundaries》2013,75(2):185-198

Lead (Pb) concentrations and isotope ratios of two different geochemical archives are compared; lake sediment cores and lichens (Hypogymnia physodes, naturally growing and transplanted) from a ca. 80 km-long transect centred on the Cu smelter and former mining town of Karabash, Ural Mountains, Russia. Lead concentrations in sediment cores from 10 lakes were generally low near their base and show an abrupt increase in their upper portions interpreted to coincide with the onset of large-scale smelting operations in 1910. Lead isotope ratios derived from ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb of the bottom layers differed significantly from those of the top. The top sediments have isotope ratios that show distinct end members, one of which was the stack dust from the Karabash smelter, which is similar to the Pb derived from ores from Sibay, a major mine in the Urals. The composition of the bottom sediment layers generally fall slightly off a mixing line between the top sediments and average Earth’s upper crust. Lichens transplanted from a reference site, as well as naturally growing lichens, sampled from southwest of the smelter have isotope ratios similar to those of the stack dust. Lichens to the northeast contained Pb from the smelter, but are increasingly influenced by other sources probably leaded petrol and local soils, and a signature derived from a source enriched in ²⁰⁷Pb. Vegetables collected from local kitchen gardens contained Pb from an additional atmospheric source, possibly coal. Our work confirms that: (1) Pb isotopes in lake sediments provide a long-term record of inputs and allows the characterisation of natural and anthropogenic sources; (2) Pb isotopes in lichens provide a short-term record of local and long-range atmospheric deposition at high spatial resolution and short time scales as they replace their Pb content within a few months; (3) determination of all four stable Pb isotopes is necessary for the identification of the sources of Pb and is extremely sensitive for discerning minor source signatures, even in an area with a dominant source such as a smelter. Particularly significant for the Karabash area is that ore-smelter-derived airborne Pb is a major component in the lake sediments and lichens but its contribution reaches insignificant levels ca. 40 km from the smelter.  相似文献   

Comparison of Early Jurassic flora from South Primorye of Russia with its main coeval floras of China     

Elena Salyukova  Elena Volynets  SUN Ge  Svetlana Shorokhova 《世界地质(英文版)》2013,16(1):19-25

The Early Jurassic flora,with over 42 species of 26 genera and documented in age by sandwiched marine beds,from the Lower Jurassic Schitukhe Formation of South Primorye,Russia,is further reported.The flora is dominated by cycadophytes,ferns and conifers,with some of ginkgoales and czekanowskiales,and characterized by occurrence of Cycadocarpidium,with very rare Coniopteris.A comparison of this flora with its coeval Early Jurassic floras of China is discussed.The Russian flora is considered as the early assemblage of Early Jurassic flora,and more similar to the Early Jurassic floras from the Shansonggang-and Yihe formations of Jilin,Beipiao Formation of Liaoning,and lower-middle Guanyintan Formation of Hunan in China.  相似文献   

The role of forcing and internal dynamics in explaining the “Medieval Climate Anomaly”     

Hugues Goosse  Elisabeth Crespin  Svetlana Dubinkina  Marie-France Loutre  Michael E. Mann  Hans Renssen  Yoann Sallaz-Damaz  Drew Shindell 《Climate Dynamics》2012,39(12):2847-2866

Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950–1250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.  相似文献   

Climate signals in sediment mineralogy of Lake Baikal and Lake Hovsgol during the LGM-Holocene transition and the 1-Ma carbonate record from the HDP-04 drill core   总被引：1，自引：0，他引：1  

Emilia P. Solotchina  Alexander A. Prokopenko  Mikhail I. Kuzmin  Pavel A. Solotchin  Anastasia N. Zhdanova 《Quaternary International》2009,205(1-2):38

Modeling the bulk sediment XRD patterns allows insight into the environmental and depositional histories of two neighboring rift lake basins within the Baikal watershed. Parallel ¹⁴C-dated LGM-Holocene records in Lakes Baikal and Hovsgol are used to discuss the mineralogical signatures of regional climate change. In both basins, it is possible to distinguish ‘glacial’ and ‘interglacial’ mineral associations. Clay minerals comprise in excess of 50% of layered silicates in bulk sediment.The abundance of smectite (expandable) layers in mixed-layer illite–smectites and the total illite abundance are the main paleoclimatic indices in the clay mineral assemblage. Both indices exhibit coherent responses to the Bølling–Allerød and the Younger Dryas. The smectite layer index is not equivalent to the abundance of illite–smectite, because illite–smectite tends to transform into illite. Repeated wetting–drying cycles in soils and high abundance of expandable layers in illite–smectites (>42%) favor the process of illitization. This relationship is clearly shown in both Baikal and Hovsgol records for the first time. The opposite late Holocene trends in illite abundance in Lake Baikal and Lake Hovsgol records suggest that a sensitive optimal regime may exist for illite formation in the Baikal watershed with regard to warmth and effective moisture.The Lake Hovsgol sediments of the last glacial contain carbonates, suggesting a positive trend in the lake's water budget. A progressive change towards lower Mg content in carbonates indicates lowering mineralization of lake waters. This trend is consistent with the lithologic evidence for lake-level rise in the Hovsgol basin.The pattern of mineralogical changes during the past 20 ka is used to interpret bulk sediment and carbonate mineralogy of the long 81-m Lake Hovsgol drill core (HDP-04) with a basal age of 1 Ma. The interglacial-type silicate mineral associations are confined to several thin intervals; most of the sediment record is calcareous. Carbonates are represented by six main mineral phases: calcite, low-Mg calcite, intermediate/high-Mg calcite, dolomite, excess-Ca dolomite and metastable monohydrocalcite. These mineral phases tend to form stratigraphic successions indicative of progressive changes in lake water chemistry. Five sediment layers with abundant Mg-calcites in the HDP-04 section suggest deposition in a low standing lake with high mineralization (salinity) and high Mg/Ca ratios of lake waters. Lake Hovsgol sediments contain the oldest known monohydrocalcite, found tens of meters below lake bottom in sediments as old as 800 ka. This unusual find is likely due to the conditions favorable to preservation of this metastable carbonate.  相似文献   

Estimate of the Eutrophication Process in the Gruža Reservoir (Serbia and Montenegro)     

Aleksandar Ostoji&#x;  Svetlana &#x;ur i&#x;  Ljiljana omi&#x;  Marina Topuzovi&#x; 《洁净——土壤、空气、水》2005,33(6):605-613

The Gru?a Reservoir (located at 238…269 m a. s. l., volume 64.6 · 10⁶ m³, surface 934 ha, drainage area 318 km², max. depth 31 m, mean theoretical retention time 22 months) was investigated during the years 1996 to 2001. The obtained values of trophic state parameters (9…200 μg L^?1 total phosphorus, 3…99 μg L^?1 chlorophyll‐a, and 0.5…2 m transparency) indicate that water of the Gru?a Reservoir is eutrophic according to three types of classification: Carlson, OECD, and Jones and Lee. It was noticed that values of average biomass abundance are large in the Gru?a Reservoir, and they could indicate a richer trophic state. When these indices are cited in connection with parameters of the trophic state, it is apparent that the Gru?a Reservoir can be classified as a eutrophic water on the basis of total phosphorus content of chlorophyll‐a and hypertrophic water with respect to transparency.  相似文献   

Morphoscopy and morphometry of quartz grains from loess and buried soil layers     

Andrej A. Velichko  Svetlana N. Timireva 《GeoJournal》1995,36(2-3):143-149

A complex method is suggested for the study of surfaces of sand grains. With this method, middle- and late Pleistocene loess-palaeosol sequences of the Russian Plain, Dnieper Basin, were studied. Surface texture of grains pointed to a dry and cold climate for their formation. During deposition of loess layers predominantly aeolian and cryogenic processes formed the grain surfaces. During interglacial and interstadial periods chemical weathering dominated.  相似文献   

Euxinia as a dominant process during OAE1a (Early Aptian) on the Eastern Russian Platform and during OAE1b (Early Albian) in the Middle Caspian     

Svetlana O. Zorina  Oksana V. Pavlova  Bulat M. Galiullin  Vladimir P. Morozov  Alexey A. Eskin 《中国科学:地球科学(英文版)》2017,60(1):58-70

A detailed study of the mineral composition and microstructure of the black shales associated with OAE1a (Eastern Russian Platform), OAE1b (Middle Caspian), and the host rocks has been carried out using X-ray diffraction, scanning electron microscopic, and microprobe analyses. The results provide important constraints for depositional environments in the sedimentary basins. Black shales with pyrite framboids imply euxinic (sulfidic) conditions with increased organic matter preservation. Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation. OAE1a on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales, and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone. The coccolith limestones indicate short intermittent episodes of interrupted stagnation, rapid oxygenation, and restoration of normal marine conditions. The presence of montmorillonite, albite, microcline, and diopside in the bituminous siltstones and in the host siltstones of OAE1a on the Eastern Russian Platform, as well as a high content of titanium in the black siltstones correlated with OAE1b in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea.  相似文献