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V. V. Egorova N. I. Volkova R. A. Shelepaev A. E. Izokh 《Mineralogy and Petrology》2006,88(3-4):419-441
Summary Ultramafic and mafic xenoliths in Ordovician Agardag alkaline basalt dikes from the Sangilen Plateau, southeastern Siberia,
provide samples from the upper mantle and crust beneath central Asia. Three major groups were distinguished among the xenoliths:
Group I xenoliths are spinel lherzolites, Group II xenoliths are spinel-garnet clinopyroxenites, and Group III comprises gabbroic
xenoliths with two subgroups: Group IIIa comprises garnet bearing gabbroids and Group IIIb is represented by garnet-free gabbroids.
The spinel lherzolite xenoliths represent the uppermost lithospheric mantle beneath the Sangilen Plateau and have geochemical
characteristics similar to those of primitive mantle. Spinel-garnet clinopyroxenite and gabbroic xenoliths are of igneous
origin and represent fragments of intrusive bodies crystallized at depths close to the mantle-crust boundary, as well as in
the lower and the upper crust. The gabbroic xenoliths are evidently the crystallization products of melts similar in major
and trace element composition to parental magma of the Bashkymugur gabbronorite-monzodiorite intrusion. Gabbroic xenoliths
from the Ordovician Agardag alkaline basalt dikes demonstrate the presence of intermediate magmatic chambers within the crust
beneath the Sangilen Plateau during the Early Palaeozoic. The relatively high equilibration temperatures of the mantle and
lower crust xenoliths in the Agardag alkaline basalt dikes are largely attributable to a plume occurring beneath the Sangilen
Plateau during the Ordovician. 相似文献
2.
Gated communities of the Moscow green belt: newly segregated landscapes and the suburban Russian environment 总被引：3，自引：0，他引：3
The transition from the Soviet to the post-Soviet period in and near Moscow manifested itself in increasing production of
segregated space both in the urban core and suburban areas outside of the beltway to accommodate the preferences of the new
Russian business and governmental elite. This paper focuses on the residential single-family housing inside old and new settlements,
which are frequently gated. Approximately 260 of such suburban communities have been developed within 30 km of the beltway
during the past few years, of which a majority have some form of exclusion mechanism in place, typically tall solid fences,
gates, closed-circuit video surveillance and guarded entry checkpoints. The difference in exclusivity varies from the most
exclusive older communities inside Moscow Serebryany Bor enclave and Rublevskoe highway mansions to less exclusive new developments
along Novorizkhskoe and Dmitrovskoe highways. Despite high rates of construction, based on sociological surveys in 2003, only
about 11% of Russia’s upper class claimed to live in such new “cottages,” with the rest owning condos and luxury apartments
in the inner city or older detached homes in villages and small towns. Therefore, not all the needs have been accommodated
and more development is certain to take place. The environmental impact of such developments is profound. Based on preliminary
LANDSAT image analysis, almost 22% of suburban “green belt” forested land within 30 km zone has been converted to new construction
from 1991 to 2001. New construction is now focusing on the remaining fragments of natural vegetation, which will likely lower
air quality and water quality available for the city. Ironically, the new developments advertise themselves as “clean and
green” with massive investments in unnatural landscaping (seeded lawns, exotic shrubs, river and lake shore “improvements”).
This investment highlights the well-known paradox of development in which people move out of town to live near nature, while
destroying the wild nature they come to enjoy.
“We left city for the weekend
It was raining, saw no stars
There were fences everywhere
Our chiefs behind the bars.”
Gennady Shpalikov 相似文献
3.
Environmental and sanitary estimation of small-river water quality is made in the zone of influence of gold-mining facilities in Krasnoyarsk Region. The estimates are based on data on the hydrochemical regime and the characteristics of phytoplankton, microphyto-periphyton, macrozoobenthos, and ichthyofauna collected during the vegetation period of 2000. 相似文献
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5.
Coal pebbles found in 1994 in the Greham Bell Island (Franz Josef Land Archipelago) are made up of the Barzas-type cuticular liptobiolith. The coal belongs to the initial stage of catagenesis and is characterized by high content of cutinite (up to 70%) with very low reflectance (Ro= 0.1%). Maceration products show some tegillate elements of Arthropodaand individual Devonian spores. It is supposed that plant cuticle and Arthropoda exocuticle are present in this coal. The obtained data suggest the presence of Paleozoic rocks in the sedimentary sequence, although they are not yet recovered. These data complement the available information on the distribution of specific Devonian coals and allow us to have a new insight into the zoogenic material involved in the coal formation. 相似文献
6.
By the example of the Orlovka massif of Li-F granites in Eastern Transbaikalia, the major- and trace-element (Li, Be, B, Ta,
Nb, W, REE, Y, Zr, and Hf) compositions of the parental melt and the character of its variations during the formation of the
differentiated rock series were quantitatively estimated for the first time on the basis of electron and ion microprobe analysis
and Raman spectroscopy of rehomogenized glasses of melt inclusions in quartz. It was shown that the composition of the Orlovka
melt corresponded to a strongly evolved alumina-saturated granitoid magma (A/CNK = 1.12–1.55) rich in normative albite, poor
in normative quartz, and similar to ongonite melts. This magma was strongly enriched in water (up to 9.9 ± 1.1 wt %) and fluorine
(up to 2.8 wt %). Most importantly, this massif provided the first evidence for high B2O3 contents in melts (up to 2.09 wt %). The highest contents of trace elements were observed in the melt from pegmatoid bodies
in the amazonite granites of the border zone: up to 5077 ppm Li, 6397 ppm Rb, 313 ppm Cs, 62 ppm Ta, 116 ppm Nb, and 62 ppm
W. Compared with the daughter rock, the Orlovka melt was depleted at all stages of formation in SiO2 (by up to 6 wt %), Na2O (by up to 2.5 wt %), and, to a smaller extent, in Ti, Fe, Mg, Sr, and Ba, but was enriched in Mn, Rb, F, B, and H2O. 相似文献
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8.
N.N. Kruk A.G. Vladimirov G.A. Babin S.P. Shokalsky N.V. Sennikov S.N. Rudnev N.I. Volkova V.P. Kovach P.A. Serov 《Russian Geology and Geophysics》2010,51(5):431-446
The history of the Vendian–Early Paleozoic formation of protoliths of continental crust in the Gorny Altai segment of the Central Asian fold belt is considered, and their composition, isotopic characteristics, and formation mechanisms are estimated. We have established two stages of crust-forming processes in Gorny Altai: Early and Late Caledonian, with the different structures of formed geoblocks and nature and compositions of crustal protoliths. At the Early Caledonian stage, fragments of oceanic lithosphere of basic composition (MORB, OIT, OIB) (TNd(DM-2st) = 0.65–1.1 Ga) formed, as well as island arcs with andesite-basaltic and andesitic protoliths with low contents of incompatible elements (TNd(DM-2st) = 0.7–0.9 Ga). At the Late Caledonian stage, the redistribution of the substance of these blocks and the external supply of material led to the formation of heterogeneous crust of turbidite basins with an oceanic basement and andesite-dacitic upper-crustal protoliths (TNd(DM-2st) varies from 0.8–0.9 Ga in the framing of the volcanic arc of Altaids to 1.4–1.6 Ga at the boundary of the Altai–Mongolian microcontinent). 相似文献
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10.
Last Glacial Maximum climate of the former Soviet Union and Mongolia reconstructed from pollen and plant macrofossil data 总被引：2，自引：2，他引：0
P. E. Tarasov O. Peyron J. Guiot S. Brewer V. S. Volkova L. G. Bezusko N. I. Dorofeyuk E. V. Kvavadze I. M. Osipova N. K. Panova 《Climate Dynamics》1999,15(3):227-240
An improved concept of the best analogues method was used to reconstruct the Last Glacial Maximum (LGM) climate from a set
of botanical records from the former Soviet Union and Mongolia. Terrestrial pollen and macrofossil taxa were grouped into
broad classes – plant functional types (PFTs), defined by the ecological and climatic parameters used in the BIOME1 model.
PFT scores were then calibrated in terms of modern climate using 1245 surface pollen spectra from Eurasia and North America.
In contrast to individual taxa, which exhibit great variability and may not be present in the palaeoassemblages, even in suitable
climates, PFTs are more characteristic of the vegetation types. The modified method thus allows climate reconstruction at
time intervals with partial direct analogues of modern vegetation (e.g. the LGM). At 18 kBP, mean temperatures were 20–29 °C
colder than today in winter and 5–11 °C colder in summer in European Russia and Ukraine. Sites from western Georgia show negative,
but moderate temperature anomalies compared to today: 8–11 °C in January and 5–7 °C in July. LGM winters were 7–15 °C colder
and summers were 1–7 °C colder in Siberia and Mongolia. Annual precipitation sums were 50–750 mm lower than today across northern
Eurasia, suggesting a weakening of the Atlantic and Pacific influences. Reconstructed drought index shows much drier LGM conditions
in northern and mid-latitude Russia, but similar to or slightly wetter than today around the Black Sea and in Mongolia, suggesting
compensation of precipitation losses by lower-than-present evaporation.
Received: 11 May 1998 / Accepted: 25 September 1998 相似文献