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991.
Acta Geotechnica - In the HADES underground research laboratory in Belgium, a large-scale PRACLAY Heater test and a small-scale ATLAS Heater test are performed to examine the... 相似文献
992.
993.
Zircons from the porphyry-like quartz-diorite boss of the Pebble Cu-Au-Mo deposit (southwest Alaska) have been examined. By
their appearance and internal structure (cathode luminescence and electron probing), the zircons have been subdivided into
four genetic groups: (1) xenogenic detrital (mainly rounded); (2) magmatogene (protolith crystal in the center and growth
zone at the edge); (3) hydrothermally altered (with new-formed regeneration edges in growth zones); (4) metamict-altered (unconsolidated
center of the crystal and sectoring in growth zones). Based on SHRIMP U-Pb dating for the principal heterogeneous elements
in every group, the following stages of ore formation have been identified for the Pebble deposit: (a) crystallization of
quartz diorite-porphyry bosses (95–92 Ma, the concordant age is 94.7 ± 1.5 Ma); (b) late magmatic metasomatic alterations
with copper-molybdenum mineralization (92–85 Ma, the concordant age is 90.15 ± 0.78 Ma); (c) postmagmatic argillization with
epithermal gold-sulfide mineralization (82–80 Ma, the concordant age is 82.9 ± 2.7 Ma). 相似文献
994.
K. S. Ivanov Yu. N. Fedorov V. S. Ponomarev V. A. Koroteev Yu. V. Erokhin 《Doklady Earth Sciences》2012,443(1):321-325
The SHRIMP-II zircon U-Pb dates for metamorphic rocks from the West Siberian basement are determined for the first time. It
is established that the major protolith of the metamorphic strata from the Shaimsk-Kuznetsovsk meganticlinorium is composed
of sedimentary Late- and Middle-Devonian rocks (395–398 Ma). It is likely that the greywackes, whose strata were mainly formed
under erosion of ophiolitic rocks, served as a substrate for the metamorphic rocks. The metamorphic transformations of the
rocks occurred under conditions of greenschist and occasionally lower amphibolite facies of metamorphism during the Late Carboniferous-Early
Permian period. 相似文献
995.
Comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges 总被引:1,自引:1,他引:1
Süleyman Adanur Ahmet Can Altuni?ik Alemdar Bayraktar Mehmet Akk?se 《Natural Hazards》2012,64(1):593-614
This paper presents a comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges. Bo?azi?i (The First Bosporus) and Fatih Sultan Mehmet (Second Bosporus) suspension bridges built in Istanbul, Turkey, are selected as numerical examples. Both bridges have almost the same span. While Bo?azi?i Suspension Bridge has inclined hangers, Fatih Sultan Mehmet Suspension Bridge has vertical hangers. Geometric nonlinearity including P-delta effects from self-weight of the bridges is taken into account in the determination of the dynamic behavior of the suspension bridges for near-fault and far-fault ground motions. Near-fault and far-fault strong ground motion records, which have approximately identical peak ground accelerations, of 1999 Chi-Chi, 1999 Kocaeli, and 1979 Imperial Valley earthquakes are selected for the analyses. Displacements and internal forces of the bridges are determined using the finite element method including geometric nonlinearity. The displacements and internal forces obtained from the dynamic analyses of suspension bridges subjected to each fault effect are compared with each other. It is clearly seen that near-fault ground motions are more effective than far-fault ground motion on the displacements and internal forces such as bending moment, shear force and axial forces of the suspension bridges. 相似文献
996.
B. M. S. Giambastiani A. M. McCallum M. S. Andersen B. F. J. Kelly R. I. Acworth 《Hydrogeology Journal》2012,20(6):1027-1044
A FEFLOW three-dimensional (3D) groundwater model is developed to enhance the understanding of groundwater processes in the complex alluvial stratigraphy of Maules Creek Catchment (New South Wales, Australia). The aquifer vertical heterogeneity is replicated by indexing 204 lithological logs into units of high or low hydraulic conductivity, and by developing a 3D geological conceptual model with a vertical resolution based on the average lithological unit thickness for the region. The model mesh is populated with the indexed geology using nearest neighbour gridding. The calibrated model is successful in simulating the observed flow dynamics and in quantifying the important water-budget components. This indicates that the lateral groundwater flow from the mountainous region is the main inflow component of the system. Under natural conditions, the Namoi River acts as a sink of water, but groundwater abstraction increasingly removes a large amount of water each year causing dewatering of the system. The pumping condition affects the river–aquifer interaction by reversing the flow, from gaining to losing river conditions during the simulation period. The procedure is relevant for the development of groundwater models of heterogeneous systems in order to improve the understanding of the interplay between aquifer architecture and groundwater processes. 相似文献
997.
Péter Ozsvárt Lajos Dosztály Georgios Migiros Vassilis Tselepidis Sándor Kovács 《International Journal of Earth Sciences》2012,101(6):1487-1501
The Avdella Mélange in the northern Pindos Mountains and its equivalent formation, the Loggitsion Unit in the Othris Mountains expose early Mesozoic (Mid-Late Triassic) oceanic fragments beneath the Western Greek Ophiolite Belt of the Inner Hellenides, Northern Greece. The mélange consists of locally interfingering blocks and slices of ribbon radiolarite, radiolarian chert and pillow basalt and is usually overthrust by Jurassic ophiolites. New Middle and Upper Triassic radiolarian biostratigraphic data are presented from radiolarites and basalt-radiolarite sequences within mélange blocks. Pillow basalts associated with the radiolarites provide clues to the opening of the Neotethyan ocean basin. The radiolarians indicate a Middle Triassic age (latest Anisian, probably early Illyrian), which is documented for the first time in the northern Pindos Mountains. The new radiolarian biostratigraphic data suggest that rift-type basalt volcanism already began in pre-Ladinian time (late Scythian?—Anisian). These basalts were then overlain by Upper Anisian to Carnian (?Norian) radiolarites. 相似文献
998.
999.
1000.
J Hamilton-Taylor A.S PostillE Tipping M.P Harper 《Geochimica et cosmochimica acta》2002,66(3):403-415
Equilibrium dialysis was used to measure Co- and Cu-binding by an isolated peat humic acid (PHA) in controlled laboratory experiments under simulated estuarine conditions: ionic strengths of 0.005 to 0.7 M in NaCl and mixed Na-Mg-Ca chloride solutions, with trace metal concentrations of ∼5 × 10−7 M, a PHA concentration of 10 mg/L, and at constant pH values of ∼7.8 (Co and Cu) and ∼4.6 (Cu only). Generally, Co- and Cu-humic binding decreased substantially with increasing ionic strength and, in the case of Cu, with decreasing pH. The presence of seawater concentrations of Ca and Mg had a relatively small effect on Co-humic binding and no measurable effect on that of Cu under the experimental conditions. The binding data were well-described by an equilibrium speciation code (the Windermere Humic Aqueous Model, WHAM) after optimising the fits by varying the metal-proton exchange constants for humic acid within justifiable limits (i.e., within 1 standard deviation of the mean exchange constants used in the WHAM database). The main factor producing the observed variations in metal-humic binding at constant pH was the electrostatic effect on the humic molecule. WHAM was used to predict Co- and Cu-humic binding in simulations of real estuaries. Co-humic binding is predicted to be relatively unimportant (generally <5% of total Co), whereas the Cu-humic complex is likely to be the dominant species throughout an estuary. The main factors producing changes in Co- and Cu-humic binding in the real-estuary simulations are the electrostatic effect on the humic molecule, ligand competition (mainly from carbonate species) for metals, and to a lesser extent Ca and Mg competition for humic binding sites. Variations in pH are significant only at the freshwater end of an estuary. WHAM simulations also indicated that competition effects between metals are more likely to occur in freshwaters than in seawater, due to enhanced electrostatic binding at low ionic strength. 相似文献