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831.
P. A. Fokin V. R. Demidova V. M. Yatsenko P. V. Stavinskii O. V. Lisunova 《Moscow University Geology Bulletin》2008,63(5):304-310
Sedimentologic analysis of cores from wells sunk in the Vankor petroleum field allowed refinement of the accumulation conditions producing the sandy strata of the Nizhnyaya Kheta River (Nizhnekhetsky) Formation accumulated in the coastal marine zone and of the Yakovlevo (Yakovlevsky) Formation accumulated under alluvial-deltaic conditions. Petrographic examination of the sandstones added information on the sources, transport, and accumulation conditions of the terrigenous material in the northeastern marginal part of the West Siberian sedimentation basin. 相似文献
832.
Patricia Vázquez Ana Luque Francisco J. Alonso Carlota M. Grossi 《Environmental Earth Sciences》2013,69(4):1237-1248
This study assesses the changes on the surface of crystalline stones due to salt crystallisation. Efflorescence was forced to grow on the surface of granite and marbles through 60 cycles of salt crystallisation with sodium sulphate. Changes on surface roughness, gloss and colour were measured every 15 cycles and the specimens were examined with naked eye and SEM. Sodium sulphate produces damage which depends on mineral composition. Results show that granites experience a mechanical decay with an increase in roughness. Peaks of mica can be observed on the surface and cracks widen and grow deeper. Colour and gloss do not show any significant change, although gloss decreases with an increase in surface roughness. In marbles, the decay is mainly chemical. Surface roughness increases due to dissolution of the calcite. White marbles exhibit yellowing. Gloss decreases during the first cycles—as grain boundaries become more visible—but tends to regain almost its initial value as the number of cycles increases. In this case, gloss does not show any relation with surface roughness. 相似文献
833.
Yu. M. Pushcharovsky 《Geotectonics》2013,47(2):67-74
The nearly latitudinal giant fracture zones in the northeastern Pacific Ocean are accompanied by narrow fault-line uplifts making up tectonic couples that strike for thousands of kilometers. They are especially distinctly expressed in the gravity map of the World Ocean [7]. As is shown in the paper, a compensation mechanism of deep mass displacement operates in the uplift-deepwater trench system. The uplifts have similar asymmetric structures, which reflects the long-term unidirectional effect of the deep geodynamic stress. In my opinion, the system of the fault-line uplifts began to form at the Cretaceous-Cenozoic boundary. 相似文献
834.
James Gerald Brophy 《Contributions to Mineralogy and Petrology》2009,157(6):797-811
Magma ascent, decompression-induced H2O exsolution and crystallization is now recognized as an important process in hydrous subduction zone magmas. During the course
of such a process calculations suggest that the ascent rate of a degassing and crystallizing mafic magma will be greater than
crystal settling velocities. Thus, any crystals formed as a consequence of volatile exsolution will remain suspended in the
magma. If the magma erupts before the percentage of suspended crystals reaches the critical crystallinity value for mafic
magma (~55 vol.%) it will produce the commonly observed crystal rich island arc basalt lava. If the magma reaches its critical
crystallinity before it erupts then it will stall within the crust. Extension of compaction experiments on a 55 vol.% sand-Karo
syrup suspension at different temperatures (and liquid viscosities) to the likely viscosities of interstitial andesitic to
dacitic liquid within such a stalled magma suggest that small amounts (up to ~10%) can be expelled on a time scale of 1–10 years.
The expelled liquid can create a new intermediate to silicic body of magma that is related to the original mafic magma via
fractional crystallization. The short time scale for liquid expulsion indicate that decompression-induced H2O exsolution and crystallization can be an important mechanism for fractional crystallization. Based on this assumption a
general model of decompression-induced crystallization and fractionation is proposed that explains many of the compositional,
mineralogical and textural features of Aleutian (and other andesites). 相似文献
835.
836.
Mercury from mineral deposits and potential environmental impact 总被引:6,自引:0,他引:6
James J. Rytuba 《Environmental Geology》2003,43(3):326-338
837.
838.
The water characteristics of the Gucheng Lake, such as eutrophication, health and spatial distribution, were investigated.
On the basis of the trophic state index (TSI) and entropy weight, a synthesized trophic state index (STSI) model was established
to assess lake eutrophication condition through calculating STSI, choosing TP, TN, COD, BOD and NH3-N as trophic variables. The STSI ranged from 50.58 to 62.44, which showed that the water has been between eutrophic and supereutrophic.
A histogram was applied to health risk assessment which was analyzed from carcinogenic substances (Cr+6, As and Cd) and non-carcinogenic substances (hydroxybenzene, Pb, Hg, CN− and NH3), and the results showed that the former was much greater than the latter for effect. The total risk for each resident caused
by all pollutants ranged from 5.18E-05 to 8.34E-05, which is far higher than the standard, recommended by Sweden Bureau of
Environment Protection and Holland Ministry of Building and Environment Protection (1.0E-05). Cluster analysis was used to
detect similarities and dissimilarities among the seven sampling sites and explain the observed clustering in terms of affected
conditions. Twenty-one variables were used to divide seven sampling sites into three groups, namely, north lake, south lake
and lake center. 相似文献
839.
Studies on the water and suspended matter concentration dynamics were performed for the summer and autumn periods in Kruglaya
Bay, Chupa Inlet (Karelian Coast, the White Sea). The tidal cycle appeared as the major factor defining the water salinity,
temperature, and suspended matter concentration. The water temperature and suspended matter concentration increased during
low tide, and the opposite pattern was observed for water salinity; all the processes were true for both surface and bottom
water layers. Therefore, we conclude that major bulk of the allochtonous suspended matter is carried into the sea by the ebb
stream. 相似文献
840.