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951.
952.
Batoul Taghipour Farid Moore Mohammad Ali Mackizadeh 《Chemie der Erde / Geochemistry》2010,70(4):377-384
The Rangan area is part of Cenozoic magmatic belt of central Iran. Eocene volcanic flows and pyroclastic rocks are intruded by a Neogene rhyolitic dome along the major Qom–Zefreh fault. The dome is pervasively hydrothermally altered. The main mineral assemblage is jarosite+barite+pyrite+quartz+sericite. This assemblage indicates acid sulphate or advanced argillic alteration. Sulfur and oxygen isotope data (δ34S & δ18O (SO4)) obtained from jarosite and barite indicate a mixing episode during the evolution of hydrothermal system and reflect the overlapping of two distinct sources of acid sulphate alteration in Rangan, i.e., a magmatic–hydrothermal fluid reacting with steam-heated meteoric water. Considering the position of brittle–ductile transition and major fault movements, jarosite and barite seemingly precipitated from rapid injection of magmatic–hydrothermal fluids into the upper portions of a steam-heated environment. 相似文献
953.
Seismic risk assessment of buildings in Izmir,Turkey 总被引:1,自引:1,他引:0
Izmir, the third largest city and a major economic center in Turkey, has more than three million residents and half million
buildings. In this study, the seismic risk in reinforced concrete buildings that dominate the building inventory in Izmir
is investigated through multiple approaches. Five typical reinforced concrete buildings were designed, modeled and assessed
for seismic vulnerability. The sample structures represent typical existing reinforced concrete hospital, school, public,
and residential buildings in Izmir. The seismic assessments of the considered structures indicate that they are vulnerable
to damage during expected future earthquakes. 相似文献
954.
The effect of water on heat capacity has been determined for four series of hydrated synthetic aluminosilicate glasses and supercooled liquids close to albite, phonolite, trachyte, and leucogranite compositions. Heat capacities were measured at atmospheric pressure by differential scanning calorimetry for water contents between 0 and 4.9 wt % from 300 K to about 100 K above the glass transition temperature (Tg). The partial molar heat capacity of water in polymerized aluminosilicate glasses, which can be considered as independent of composition, is (J/mol K). In liquids containing at least 1 wt % H2O, the partial molar heat capacity of water is about 85 J/mol K. From speciation data, the effects of water as hydroxyl groups and as molecular water have tentatively been estimated, with partial molar heat capacities of 153 ± 18 and 41 ± 14 J/mol K, respectively. In all cases, water strongly increases the configurational heat capacity at Tg and exerts a marked depressing effect on Tg, in close agreement with the results of viscosity experiments on the same series of glasses. Consistent with the Adam and Gibbs theory of relaxation processes, the departure of the viscosity of hydrous melts from Arrhenian variations correlates with the magnitude of configurational heat capacities. 相似文献
955.
Kamal A. Ali Robert J. Stern William I. Manton Peter R. Johnson Sumit K. Mukherjee 《International Journal of Earth Sciences》2010,99(4):705-726
The Neoproterozoic Atud diamictite in Wadi Kareim and Wadi Mobarak in the Eastern Desert of Egypt and the Nuwaybah formation
in NW Saudi Arabia consist of poorly sorted, polymictic breccia, with clasts up to 1 m of granitoid, quartz porphyry, quartzite,
basalt, greywacke, marble, arkose, and microconglomerate in fine-grained matrix. Stratigraphic relations indicate that the
diamictite was deposited in a marine environment. Integrated field investigation, petrographic study and U–Pb SHRIMP zircon
ages demonstrate that the Atud and Nuwaybah are correlative. The distribution of zircon ages indicate that ~750 Ma ages are
dominant with a significant component of older materials, characterized by minor Mesoproterozoic and more abundant Paleoproterozoic
and Neoarchean ages. Some matrix and metasedimentary clast zircons yield ages that are a few 10s of Ma younger than the age
of the youngest clast (754 ± 15 Ma), suggesting Atud/Nuwaybah diamictite deposition ~750 Ma or slightly later, broadly consistent
with being deposited during the Sturtian glaciation (740–660 Ma). The Paleoproterozoic and Neoarchean clasts have no source
within the ensimatic Arabian–Nubian Shield. The distribution of the pre-Neoproterozoic ages are similar to the distribution
of the pre-Neoproterozoic ages in Yemen and Saharan Metacraton, suggesting that these clasts have been transported hundreds
of kilometers, maybe by ice-rafting. The Atud diamictite may represent important evidence for Cryogenian “Snowball Earth”
in the Arabian–Nubian Shield. 相似文献
956.
Contribution of diffuse sources to the sediment and phosphorus budgets in Ben Chifley Catchment,Australia 总被引:3,自引:3,他引:0
Relative contribution of different diffuse sources to the sediment and phosphorous (P) budgets in the Ben Chifley Reservoir
was estimated using a multivariate mixing model and geochemical indices and tracers. The influence of the underlying geology
on land use characteristics and the dynamics of sediment and P in the catchment were discussed. Sediments currently in transport
to the reservoir are derived mainly from areas underlain by Quaternary alluvium, accounting for 33% of the reservoir sediment
budget. A major portion of the sediments from the Quaternary alluvium originates from pasture land which also contributes
about 60% of sediment-bound P in the reservoir, followed by cropland (30%) and forest area (10%). Phosphorus-based fertiliser
contributes more than 50% of the soil P in pasture and cropland and more than 60% in forest plantation area. The remaining
P reaching the reservoir originates from natural soils (native sources). Phosphate from both fertiliser and native sources
are transported to the water courses and ultimately the reservoir as a consequence of gully, stream bank and surface erosion.
Erosion control, trapping of fertiliser runoff, establishing riparian vegetation and reducing application of P-based fertiliser
by increasing native pasture cultivation in the risk areas should be considered as management options for controlling the
impact of P and sediment in the reservoir. 相似文献
957.
Mineralogical and spectroscopic characterization,and potential environmental use of limestone from the Abiod formation,Tunisia 总被引:1,自引:0,他引:1
Ali Sdiri Teruo Higashi Tamao Hatta Fakher Jamoussi Norio Tase 《Environmental Earth Sciences》2010,61(6):1275-1287
Limestone beds of the Late Cretaceous Abiod formation (Campanian-Maastrichtian system) are fundamentally important for the
economic growth of the raw material sector in Tunisia. However, little attention has been paid to the detailed physical and
chemical properties of the Abiod limestone. Nine limestone samples collected from the Abiod formation outcropping in the areas
of Bizerte, Gafsa and Gabes, Tunisia, as well as their separated clay fractions, were characterized using different techniques,
such as XRF, XRD, FTIR and TG/DTA. XRF showed the chemical composition of the limestone in which calcium carbonate was the
main constituent, and silica, iron and magnesium were the impurities. XRD also confirmed the presence of small amounts of
clay minerals and quartz along with sharp peaks of calcite. FTIR spectra indicated that the limestone was mainly composed
of CaCO3 in the form of calcite, as identified by its main characteristic absorption bands. These data were in agreement with XRD
and XRF analysis data. The TG/DTA curves of the limestone samples, showing a close similarity to that of pure calcium carbonate,
exhibited an endothermic peak between 600 and 760°C, with the maximum near 750°C. Moreover, FTIR spectra of clay fraction
samples indicated high silica content in some samples. Especially the samples SD1 and SD2 collected in the northern area showed
higher amounts of silica compared with those of AS1, AS2, CHB, ZNC, SND, MKM and GBS collected from southern districts. However,
among the latter seven samples, one could recognize two groups based on the clay mineral investigations: (1) limestone with
minor amounts of smectite and mixed layer minerals of smectite/illite (AS1 and 2, CHB, ZNC, SND and GBS) and (2) limestone
with smectite, kaolinite and apatite (SND and MKM). Differences in these mineralogical and chemical characteristics should
be considered when limestone from the Abiod formation is utilized as a medium for heavy metal removal from wastewater. 相似文献
958.
Ahmed I. Rushdi Khalid F. Al-Mutlaq Bernd R. T. Simoneit Adnan Al-Azri Ali A. Z. DouAbul Sheikha Al-Zarban Faiza Al-Yamani 《Arabian Journal of Geosciences》2010,3(2):113-131
River runoff and atmospheric fallout (dust and air particulate matter) are major input sources of natural and anthropogenic
terrestrial organic and inorganic components to the Arabian seas. In this study, we report on the various lipid tracer compounds
that might be transported to the Arabian Gulf by rivers, dust, and air particulate matter. These are based on geochemical
analysis of sediment, dust, and particulate samples collected from Iraq, Kuwait, and Saudi Arabia. The samples were extracted
with a dichloromethane/methanol mixture and analyzed by gas chromatography-mass spectrometry. The extractable organic compounds
(lipids) in the samples include n-alkanes, n-alkanoic acids, n-alkanols, methyl n-alkanoates, steroids, triterpenoids, carbohydrates, and petroleum hydrocarbons. The steroids and triterpenoids were major
components in river and wetland samples. The major sources of these lipids were from natural vegetation, microbial (plankton
and bacteria) residues in the sediments, sand, and soils, with some contribution from anthropogenic sources. Accordingly,
these sources could be major inputs to the Arabian seas besides the autochthonous marine products. Future studies of the organic
and inorganic biogeochemistry on river, dust, and coastal areas are needed to characterize the various regional sources, transformation,
and diagenetic processes of the organic matter en route to the marine environment. 相似文献
959.
Ali Harzallah 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(4):459-470
The vertical structure of the flow variability through the Strait of Gibraltar is studied based on the Gibraltar Experiment and the Word Ocean Circulation Experiment data sets. An analysis of the leading modes of velocity and density variability at the Strait of Gibraltar showed an adjustment of the water masses exchanged through the Strait. Mediterranean mass variations resulting from the water exchanged by barotropic tidal oscillations generate changes of the baroclinic component of the flow that damp these mass variations. This adjustment explains the previously observed fortnightly variation of the shear. Moreover, the adjustment is found to operate for the subinertial time scale flow variability forced by the atmospheric pressure. An analytical model aimed at reproducing variations of the velocity with time and in the vertical is derived. The model includes a depth-varying parameterisation of friction and takes into account density gradient fluctuations across the Strait. The model reproduces the main features of the flow, in particular the shear and the interface depth variations with the tide phase. 相似文献
960.
Nurur Rahman †‡ Janusz Krywult Patrick M. Motl Piotr Flin Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2006,367(2):838-850
We have made a comparative study of morphological evolution in simulated dark matter (DM) haloes and X-ray brightness distribution, and in optical clusters. Samples of simulated clusters include star formation with supernovae feedback, radiative cooling and simulation in the adiabatic limit at three different redshifts, z = 0.0, 0.10 and 0.25. The optical sample contains 208 Abell, Corwin & Olowin (ACO) clusters within redshift, z ≤ 0.25 . Cluster morphology, within 0.5 and 1.0 h −1 Mpc from cluster centre, is quantified by multiplicity and ellipticity.
We find that the distribution of the DM haloes in the adiabatic simulation appears to be more elongated than the galaxy clusters. Radiative cooling brings halo shapes in excellent agreement with observed clusters; however, cooling along with feedback mechanism makes the haloes more flattened.
Our results indicate relatively stronger structural evolution and more clumpy distributions in observed clusters than in the structure of simulated clusters, and slower increase in simulated cluster shapes compared to those in the observed one.
Within z ≤ 0.1 , we note an interesting agreement in the shapes of clusters obtained from the cooling simulations and observation. We also note that the different samples of observed clusters differ significantly in morphological evolution with redshift. We highlight a few possibilities responsible for the discrepancy in morphological evolution of simulated and observed clusters. 相似文献
We find that the distribution of the DM haloes in the adiabatic simulation appears to be more elongated than the galaxy clusters. Radiative cooling brings halo shapes in excellent agreement with observed clusters; however, cooling along with feedback mechanism makes the haloes more flattened.
Our results indicate relatively stronger structural evolution and more clumpy distributions in observed clusters than in the structure of simulated clusters, and slower increase in simulated cluster shapes compared to those in the observed one.
Within z ≤ 0.1 , we note an interesting agreement in the shapes of clusters obtained from the cooling simulations and observation. We also note that the different samples of observed clusters differ significantly in morphological evolution with redshift. We highlight a few possibilities responsible for the discrepancy in morphological evolution of simulated and observed clusters. 相似文献