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P. N. Aleksandrov 《Izvestiya Physics of the Solid Earth》2007,43(3):197-204
The solution of forward 2-D geoelectric problems is considered for anisotropic and bianisotropic media. The problems are reduced to the solution of integrodifferential equations obtained with the use of integral Fourier and Fourier-Bessel transforms for horizontally heterogeneous layered media and radially heterogeneous layered media. This approach is particularly effective for studying the influence of small-scale geological structures (such as faults, borehole wall mud cakes, and the like) on results of geoelectric studies. 相似文献
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The results of studies of phytoplankton production, biomass, and species composition conducted in Kursiu Marius Lagoon in 2001, 2002 are presented. A significant effect of blue-green alga blooming on the trophic status and processes in the coastal part of Kursiu Marius Lagoon is revealed. It is shown that the mass development of algae in combination with setup phenomena can cause alga accumulation in the coastal zone, oxygen deficiency, and fish kills. 相似文献
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S. M. Aleksandrov 《Geochemistry International》2010,48(12):1220-1236
The boron, tin, tungsten, beryllium, and fluorite deposits of the York Range, Seward Peninsula, represent the continuation
of the Asian segment of the Pacific ore belt and are globally conjugate with the Verkhoyan-Chukotka ore province of Northeastern
Russia. They are localized in the alteration aureoles of dolomites and limestones of the Paleozoic Port Clarence Formation
at the contact with the Mesozoic leucocratic granites and genetically belong to the magnesian-skan ore formation. Ore-generating
process developed in marbles, skarns, and greisens under hypabyssal conditions in several stages and was accompanied by sequential
formation of polymineral assemblages. Early mineralization is represented by magnetite in prograde pyroxene skarns after dolomites.
Postmagmatic ore stage is represented by formation of endogenous borates, including their tin-bearing Mg-Fe species, in the
magnesian skarns, superposition of calcareousskarn assemblages containing calcium borates, borosilicates, and scheelite, formation
of cassiterite and wolrframite in the greisenized granites, and precipitation of sulfides, chrysoberyl, and fluorite. The
mineral composition of the rocks and ores was formed under the influence of F-bearing hydrothermal solutions, which caused
the presence of fluorine in borates, rock-forming silicates, and the replacement of calcite by fluorite. Boron, tin, beryllium,
and fluorine participate at all the stages of endogenous process, but the mineral modes of their occurrence are varied, which
is confirmed by data on their chemical composition. The results of studying the skarns and ores of the Alaska deposits are
of great applied and scientific significance, and can be used for study of skarn-greisen deposits localized at the contacts
of carbonate rocks with granite intrusions of the Pacific ore belt and other world’s regions. 相似文献
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G. M. Tovmasyan R. Kh. Oganesyan R. A. Epremyan S. E. Nersesyan M. A. Mkrtchyan Yu. M. Khodzhayants M. N. Krmoyan A. L. Kashin D. Huguenin S. I. Serova Yu. V. Romanenko A. P. Aleksandrov V. G. Titov M. Kh. Manarov 《Astrophysics》1990,32(1):1-5
Byurakan Astrophysical Observatory; SKB Granit; Geneva Observatory; Flight Control Center. Translated from Astrofizika, Vol. 32, No. 1, p. 5–13, January–February, 1990. 相似文献
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E.M. Bazelyan Yu.P. Raizer N.L. Aleksandrov F. D'Alessandro 《Atmospheric Research》2009,94(3):436-447
A simple model of a glow corona occurring near the tip of a grounded electrode in a thundercloud electric field that can be enhanced by an approaching downward leader has been studied analytically and numerically with regard to the effect of wind. We obtained an approximate expression for corona current taking into account the (i) removal of space charge from the coronating point due to ion drift and wind and (ii) image of the charge in the ground. As the wind velocity decreases to zero, the expression tends to that obtained previously in the absence of wind. It was shown analytically and numerically that, in a thundercloud electric field, even moderate wind velocities lead to hundreds of percent increase in the corona current. This current decreases with time only slightly in a steady thundercloud electric field, as opposed to the current behavior in the absence of wind. However, even strong wind is not sufficient to affect the properties of a corona intensified in the electric field of an approaching downward leader. The occurrence of wind does not affect the conditions for initiation of an upward connecting leader from grounded objects and consequently the efficiency of lightning rods of ordinary height. 相似文献
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Krek A. V. Krek E. V. Ezhova E. E. Paka V. T. Kondrashov A. A. Danchenkov A. R. Bagirov N. E. Kudryavtzeva E. A. Bubnova E. S. Sergeev A. Yu. Aleksandrov S. V. 《Oceanology》2021,61(4):581-583
Oceanology - New data on the structure of the water column, upper layer of bottom sediments, and biological communities of the Gdansk and Gotland deeps and the Gulf of Finland in the Baltic Sea... 相似文献
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This paper addresses the genesis and composition of endogenous borates and other minerals from the magnesian-skarn aureoles at the contacts between dolomites and Hercynian granitoid intrusions of the Eastern and Central Pyrenees (Querigut and Costabonne peak massifs in France, and the Monchi deposit in Spain). It was shown that these occurrences and other magnesian skarns in the Sierra Morena Range, Spain, genetically belong to the periclase depth facies: zoned metasomatic aureoles of dolomites of primitive structure complicated by the development of periclase marble zones. The near-contact zones of the intrusions are represented by the granitoids of increasing basicity and alkalinity, which indicates the assimilation of host rocks by overheated granitic magmas. The postmagmatic stage was marked by the formation of magnesium and magnesium-iron borates of diverse composition in calciphyres and marbles, replacement of forsterite by humites in the calciphyres, and the development of silicates of decreasing Mg mole fraction after pyroxene skarns; the latter is accompanied by magnesium migration into the outer zones of the aureole. It was determined that the studied deposits of France contain boron minerals (kotoite, suanite, and pertsevite) previously unknown for this region in association with fluoborite and late szaibelyite. In skarns of Spain, the high-Fe borates are represented by monomineral aggregates of fine-prismatic parallel oriented crystals of vonsenite or its coarse-grained masses. It is conceivable that sulfide-bearing magnesian skarns and calciphyres of the studied deposits contain magnesium hydroxysulfides: tochilinite (after pyrrhotite) and valleriite (after chalcopyrite). 相似文献
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The composition of minerals of the titanite-malayaite series and their mineral assemblages and genesis were examined at the Bol’shoi Kan’on deposit in Magadan oblast and at other deposits. These minerals were demonstrated to be typomorphic Sn-bearing silicates in postmagmatic bimetasomatic hypabyssal calc skarns and skarnoids in tin-bearing provinces. The series of these minerals with similar crystal structures has a miscibility gap, and the minerals are characterized by notably different Sn concentrations. Moreover, titanite may contain Al, Fe, F, and OH, whose concentrations decrease in the Sn-bearing members of the series (malayaite). These silicates were formed at many deposits after the successive transforms of skarn mineral assemblages. The early assemblages include wollastonite in calcic carbonate rocks and diopside and salite in skarnoids. The latter minerals are replaced first by hedenbergite with subordinate amounts of vesuvianite and garnet first of grossular and then andradite composition. This process was syngenetic with the formation of borosilicates (danburite, axinite, and tourmaline). Ti thereby may be accommodated in grossular and Sn in Fe-bearing silicates, mostly, in andradite. Skarns often contain both titanite and malayaite, which were produced in these rocks earlier than cassiterite. The isomorphic series of these minerals has a miscibility gap. The oreforming processes ended with the crystallization of quartz, fluorite, and rare sulfides, including stannite. The late Sn-bearing minerals at some deposits are stokesite and Mg, Fe, and Ca stannates, which crystallized during malayaite replacement by newly formed calcite-quartz aggregates. The Sn-bearing sulfides are replaced by varlamoffite during supergene processes. 相似文献