Geothermometers, Arrhenian behaviour and 'geothermometers'     

Igor M. Villa 《地学学报》2001,13(2):84-85

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Mikulino and Valdai palaeoenvironments in the Vologda area, NW Russia     

Valery Gey  Matti Saarnisto  Juha Pekka Lunkka  Igor Demidov 《Global and Planetary Change》2001,31(1-4)

Nine representative sediment sequences and pollen diagrams obtained during the Quaternary mapping programme carried out by the Geological Expedition (St. Petersburg, Russia) between 1960s and 1980s are presented from the Vologda area, NW Russian Plain, covering the time span from the Moscow cold (Saale) stage into the Late Valdai (Weichsel) substage. This work was done in order to shed light on the evolution of palaeoenvironments, vegetation and climate in the area. The results suggest that two major depressions in the Vologda area, namely the Mologa–Sheksnian and Prisukhonian basins, witnessed lake level fluctuations that were most likely closely linked to climatic fluctuations. It is suggested that during the Mikulino (Eem) thermal optimum most of the lowland areas were dry land. However, during the Early and Middle Valdai, the large depressions started to flood as a result of wet and cold climate. This caused the accumulation of lacustrine and also lacustrine–alluvial and lacustrine–bog sediments into the basins. The Valdai forest composition varied between closed spruce–birch forests and treeless tundra. Lakes persisted throughout the Valdai stage including the extremely dry last glacial maximum (LGM)-time when the Scandinavian Ice Sheet dammed the northbound rivers in the Vologda area.  相似文献   

Study of the outer galactic structure for 288°≤l≤310°, −7°≤b≤2°     

Silvia L. Garzoli  Igor F. Mirabel 《Astrophysics and Space Science》1973,25(1):207-216

The structure of the outer part of the Galaxy is studied, based upon 21-cm line observations of Hi in the region 288°l310°, –7°b2°.In this longitude range the galactic plane is strongly bend toward negative latitudes.The principal outer structure is a spiral arm which has a pitch angle of 10° and is formed by several concentrations differing in shape and size. There exists also a secondary concentration which could be a split from the previous structure.Possible hypotheses about the origin of the later feature are discussed.  相似文献   

Trace element accumulation in fishes collected from coastal waters of the Caspian Sea     

Anan Y  Kunito T  Tanabe S  Mitrofanov I  Aubrey DG 《Marine pollution bulletin》2005,51(8-12):882-888

Concentrations of 13 trace elements (V, Mn, Cr, Co, Cu, Zn, Se, Mo, Ag, Cd, Hg, Tl and Pb) were determined in muscle of bony fishes collected from coastal areas of the Caspian Sea (Kazakhstan, Azerbaijan, Turkmenistan and Iran). In all the fishes, Zn concentration was highest, followed by Cu, Se, Mn and Co, while levels of toxic elements (Ag, Cd, Cd, Tl and Pb) were relatively low. Concentrations of several elements were significantly varied between the species in each sampling area. For most of the trace elements examined, the concentrations decreased significantly with body weight of fishes. In contrast, a positive correlation with body weight was found for Co, Se and Pb concentrations in one fish species, and Hg in 2 fish species. Geographical difference in the concentrations of trace elements was examined using the Caspian roach collected from five stations of Iranian coastal waters. The concentrations of Co, Mo, Ag, Cd and Tl were higher in fishes from western stations than those from eastern stations, whereas the opposite trend was observed for Hg, indicating that local sources of trace metal pollution may be present in the Iranian coastal areas of the Caspian Sea. Levels of trace elements in Caspian fishes were relatively low in comparison to those of other regions, but Zn and Hg levels in some specimens exceeded the guideline values for food.  相似文献   

俄罗斯高精度重力法直接预测油气藏（GONG）技术的原理及应用效果分析     

王西文  米哈依诺夫． 《地球科学与环境学报》1996,(1)

本文研究一种最优化的俄罗斯油气勘探中的地球物理和实用方法．简要描述了作为该方法的基础的重力－地震综合解释，并在理论上建立了这种解释模式．用该方法可给出油气勘探阶段远景区评价，其预测探井成功率在８０％～９０％。  相似文献   

Artificial Lineaments in Digital Terrain Modelling: Can Operators of Topographic Variables Cause Them?     

Igor V. Florinsky 《Mathematical Geology》2005,37(4):357-372

Digital terrain modeling is widely used in geological studies. In some cases, orthogonal and diagonal linear patterns appear on maps of local topographic variables. These patterns may be both portrayals of geological structures and artefacts. Some researchers speculated that possible anisotropy of operators of local topographic variables might be a cause of these artefacts. Using a principle for testing derivative operators in image processing, we gave proof to isotropy (rotation invariability) of operators of a majority of local topographic attributes of the complete system of curvatures (i.e., slope gradient, horizontal curvature, vertical curvature, mean curvature, Gaussian curvature, accumulation curvature, ring curvature, unsphericity curvature, difference curvature, minimum curvature, maximum curvature, horizontal excess curvature, and vertical excess curvature). Rotating an elevation function about z-axis and then applying these operators cannot lead to variations in both values of the topographic variables and patterns in their maps, comparing with results of applying these operators to an unrotated elevation function. This demonstrates that linear artefacts with preferable directions in maps of the topographic attributes specified cannot be caused by intrinsic properties of their operators. Other possible sources for false linear patterns in maps of topographic variables are briefly discussed: (a) errors in the compilation of digital elevation models (DEMs), (b) grid geometry of digital terrain models (DTMs), (c) errors in DEM interpolation, (d) imperfection of algorithms for DTM derivation, and (e) aliasing errors.  相似文献   

Magnetite compositions and oxygen fugacities of the Khibina magmatic system     

Igor D. Ryabchikov  L.N. Kogarko 《Lithos》2006,91(1-4):35-45

Most titanomagnetite in the Khibina alkaline igneous complex, sampled through 500 m of a vertical cross-section, is represented by Ti-rich varieties. The ulvöspinel component is most commonly around 55 mol%, rarely reaching up to 80 mol%.

We calculated an f_O2–T diagram for magnetite + ilmenite + titanite + clinopyroxene + nepheline + alkali feldspar and magnetite + titanite+ clinopyroxene + nepheline + alkali feldspar phase assemblages at a hedenbergite activity of 0.2. The diagram shows that magnetites with 55 mol% of ulvöspinel crystallized at oxygen fugacities just slightly below the quartz–fayalite–magnetite buffer. More Ti-rich varieties crystallized at higher temperatures and slightly lower ΔQMF values, whereas more Ti-poor magnetites crystallized at or below about 650 °C.

Under the redox conditions estimated for the apatite-bearing intrusion of the Khibina complex (close to the QFM buffer), substantial quantities of methane may only form during cooling below 400 °C in equilibrium with magma. However, even at higher orthomagmatic temperatures and redox conditions corresponding to ΔQMF = 0, the hydrogen content in the early magmatic stage is not negligible. This hydrogen present in the gas phase at magmatic temperatures may migrate to colder parts of a solidifying magma chamber and trigger Fischer-Tropsch-type reactions there. We propose therefore, that methane in peralkaline systems may form in three distinct stages: orthomagmatic and late-magmatic in equilibrium with a melt and — due to Fischer-Tropsch-type reactions — post-magmatic in equilibrium with a local mineral assemblage.  相似文献   

Evaluating Hyperspectral Imager for the Coastal Ocean (HICO) data for seagrass mapping in Indian River Lagoon,FL     

Hyun Jung Cho  Igor Ogashawara  Deepak Mishra  Joseph White  Andrew Kamerosky  Lori Morris 《地理信息系统科学与遥感》2014,51(2):120-138

Differentiation between benthic habitats, particularly seagrass and macroalgae, using satellite data is complicated because of water column effects plus the presence of chlorophyll-a in both seagrass and algae that result in similar spectral patterns. Hyperspectral imager for the coastal ocean data over the Indian River Lagoon, Florida, USA, was used to develop two benthic classification models, Slope_RED and Slope_NIR. Their performance was compared with iterative self-organizing data analysis technique and spectral angle mapping classification methods. The slope models provided greater overall accuracies (63–64%) and were able to distinguish between seagrass and macroalgae substrates more accurately compared to the results obtained using the other classifications methods.  相似文献   

Cyclones and their possible changes in the Arctic by the end of the twenty first century from regional climate model simulations     

Mirseid Akperov  Igor Mokhov  Annette Rinke  Klaus Dethloff  Heidrun Matthes 《Theoretical and Applied Climatology》2015,122(1-2):85-96

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Long-lasting Cadomian magmatic activity along an active northern Gondwana margin: U–Pb zircon and Sr–Nd isotopic evidence from the Brunovistulian Domain,eastern Bohemian Massif     

Soejono  Igor  Janoušek  Vojtěch  Žáčková  Eliška  Sláma  Jiří  Konopásek  Jiří  Machek  Matěj  Hanžl  Pavel 《International Journal of Earth Sciences》2017,106(6):2109-2129

International Journal of Earth Sciences - Cadomian magmatic complexes of the Brunovistulian Domain crop out at the eastern termination of the Bohemian Massif. However, the age, nature and...  相似文献