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21.
Alireza Mohammadi Ahmad Khakzad Nematolah Rashidnejad Omran Mohammad Reza Mahvi Parviz Moarefvand Peyman Afzal 《Arabian Journal of Geosciences》2013,6(11):4387-4398
The goal of this study is to separate different mineralized zones in Dareh-Ashki gold deposit located in Muteh Complex, Central Iran, by using number–size (N-S) fractal model. The N-S log–log plot shows seven geochemical populations and four Au-mineralized zones. Based on obtained results, Au thresholds are 0.17, 0.32, 6.3, and 12.6 ppm which represent weakly, moderately, highly, and extremely mineralized zones in terms of Au grades, respectively. Au values lower than 0.17 ppm illustrate wall rocks. Main mineralization stage of gold commences from 6.3 ppm in this deposit. The moderately mineralized zone with Au values between 0.32 and 6.3 ppm has occupied the biggest part of the studied deposit. However, highly (with Au values between 6.3 and 12.6 ppm) and extremely (higher than 12.6 ppm) mineralized zones have small extension. Correlation between geological model and results from N-S fractal model reveals that the gold mineralized zones specifically the moderately mineralized zone are situated in green schist units. 相似文献
22.
地理信息共享不仅是地球系统科学发展的必然要求,而且对推动科学数据共享具有重要意义。自地理信息共享的概念提出以来,对地理信息共享的研究主要集中在地理信息共享技术上,但地理信息共享的实践证明,并非所有地理信息共享的障碍都能通过技术方法来解决,因此需要从非技术视角对地理信息共享进行研究。本文从新的视角,即行为的视角对地理信息共享进行了研究。本文介绍了地理信息共享行为模型,在对我国同地理信息共享有关的主要部门的问卷调查的基础上,通过实证研究,定量地分析了影响我国地理信息共享的非技术因素。结合Omran在埃及和荷兰的实证研究结果,分析了文化差异对地理信息共享行为的影响。在定性和定量分析的基础上,检验和修正了地理信息共享行为模型,并以此为基础,为我国的地理信息共享环境建设提出了相关的建议。实证研究的结果也表明,地理信息共享行为模型在不同的文化背景下的适用性。 相似文献
23.
Mineral chemistry of a Cenozoic igneous complex,the Urumieh–Dokhtar magmatic belt,Iran: Petrological implications for the plutonic rocks 
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下载免费PDF全文 Maryam Honarmand Nematollah Rashidnejad Omran Franz Neubauer Ghasem Nabatian Mohammad Hashem Emami Manfred Bernroider Jamshid Ahmadian Mohammad Ebrahimi Xiaoming Liu 《Island Arc》2016,25(2):137-153
The Niyasar plutonic complex, one of the Cenozoic magmatic assemblages in the Urumieh‐Dokhtar magmatic belt, was the subject of detailed petrographic and mineralogical investigations. The Niyasar magmatic complex is composed of Eocene to Oligocene mafic rocks and Miocene granitoids. Eleven samples, representing the major rock units in the Niyasar magmatic complex and contact aureole were chosen for mineral chemical studies and for estimation of the pressure, temperature, and oxygen fugacity conditions of mineral crystallization during emplacement of various magmatic bodies. The analyzed samples are composed of varying proportions of quartz, plagioclase, K‐feldspar, hornblende, biotite, titanite, magnetite, apatite, zircon, garnet, and clinopyroxene. Application of the Al‐in‐hornblende barometer indicates pressures of around 0.2 to 0.4 kbar for the Eocene–Oligocene mafic bodies and around 0.5 to 1.7 kbar for the Miocene granitoids. Hornblende‐plagioclase thermometry yields relatively low temperatures (661–780 °C), which probably reflect late stage re‐equilibration of these minerals. The assemblage titanite–magnetite–quartz as well as hornblende composition were used to constrain the oxygen fugacity and H2O content during the crystallization of the parent magmas in the Miocene plutons. The results show that the Miocene granitoids crystallized from magmas with relatively high oxygen fugacity and high H2O content (~5 wt% H2O). The Miocene granitoids show similar range of oxygen fugacity, H2O contents and mineral chemical compositions, which indicate a common source for their magmas. Although the crystallization pressures of the Miocene plutons discriminate various categories of plutonic bodies emplaced at depths of about 5.7–6.5 km (Marfioun pluton), about 4.2 km (Ghalhar pluton) and 1.9–2.3 km (Poudalg pluton), they were later uplifted to the same level by vertical displacement of faults. The emplacement depths of the Niyasar plutons suggest that the central part of the Urumieh‐Dokhtar magmatic belt has experienced an uplift rate of ca. 0.25–0.4 mm/yr from the Miocene onwards. 相似文献
24.
Omran E. Frihy 《Environmental Geology》2009,58(6):1177-1189
Although the western-Mediterranean coast of Egypt between Sallum and Alexandria, ~550 km long, has maintained a considerable
equilibrium throughout history, developers have built traditional protective structures in an effort to form sheltered recreational
beaches without taking into consideration its geomorphologic characteristics, coastal processes and their harmful impact on
the coastal environment and human safety. The improper practices in this environmentally valuable region have induced us to
undertake an initiative to carry out a morphodynamic analysis to provide a framework for understanding the relationship between
coastal morphology and the prevailing dynamic forces. Based on the degree of natural protection or wave sheltering, the study
shoreline can be categorized into four distinct morphotypical stretches: (1) high-energy wave-exposed shores and the outer
margins of the rocky headlands, (2) moderate to high wave-energy beaches along semi-exposed embayments and bays mostly downdrift
of the rocky headlands, (3) low-wave energy at semi-exposed headland lee-sided and pocket beaches, and (4) calm wave-sheltered
enclosing water basins for safe anchorages, moorings and recreation beaches. The results deducted will have practical applications
for shoreline management initiatives regarding sustained sites suitable for future beachfront development such as safe swimming
conditions, sport facilities, water intakes and sheltered areas for vessels. In addition, benefits realized by the understanding
of the morphodynamic processes would enhance our awareness of the significance of the role of western coast morphodynamics
in supporting sustainable development via shoreline management. As far as sustainability is concerned, the selection of appropriate
sites would help avoiding or minimizing the formation of the hard structures needed for creating safe recreation beaches.
On a national scale, results reached could provide reliable database for information that can be used in establishing a sustainable
shoreline management plan, which is, in turn, an essential part when implementing an Integrated Coastal Zone Management Plan
for this region of attraction. 相似文献
25.
Frihy Omran E. 《GeoJournal》1992,26(3):389-394
Carbon dating data of changes in seal level during the Holocene at the Nile delta coast provide eustatic depth-time curve
of the region. The curve reveals that sea level was approximately 41 meters below the present level around 8,500 years ago.
Trend analysis indicates that with melting of glaciers there was a rapid rise in sea level of about 3 mm/yr. The constructed
data points are found to be comparable with other curves in the Mediterranean and wold-wide regions. The general changes of
the data points are fairly correlated with the ancient shoreline indicators of morphological features (shelf terraces and
slopes, old dunes, sand accretion ridges) and sediments at continental shelf and its contiguous coastal zone that belong to
Holocene transgression. 相似文献
26.
Omran E. Frihy 《Natural Hazards》1992,5(1):65-81
Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively. Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers. 相似文献
27.
Nematollah Rachidnejad-Omran Mohammad Hachem Emami Mossaïeb Sabzehei Ebrahim Rastad Herv Bellon Alain Piqu 《Comptes Rendus Geoscience》2002,334(16)
A detailed analysis of metamorphic complexes outcropping in the Muteh area in central Iran leads to establish the regional stratigraphical column, and to propose a Palaeozoic age for the metamorphic protolith that mainly consists of volcano-sedimentary units. 40K---40Ar ages for minerals suggest the Mesozoic age of the metamorphic amphiboles and the Palaeocene ones for a late or even post metamorphic bimodal magmatism. To cite this article: N. Rachidnejad-Omran et al., C. R. Geoscience 334 (2002) 1185–1191. 相似文献
28.
1Introduction Seamountsarethewell knownfeaturesinthe world’soceans,beingmostcommoninthePacific (Smith,1988;Pringleetal.,1991;Hasse,1991). Recentvolcanicactivityoccursinthezonesondi vergentorconvergentplatemarginsorintheintraplate regimes.Seamountsexisteitherasisolatedvolcanic edifices(Gardneretal.,1984;MertzandRenne, 1995)or,sometimes,formlinearchainstogetherwith oceanislands.Anumberofgeochronologicalinvestiga tionsonoceanislands(DuncanandMcDougall,1974; Dymond,1975;McDougall,1979… 相似文献
29.
Analysis of solar radiation over Egypt 总被引：1，自引：0，他引：1
M. A. Omran 《Theoretical and Applied Climatology》2000,67(3-4):225-240
Summary The database utilized in this analysis consisted of daily sunshine duration and hourly global and diffuse radiation on a
horizontal surface (for Matruh Cairo, and Aswan), and normal incidence beam radiation (for Cairo and Aswan only). Monthly-average
hourly and daily values are reported for each of these three types of measured radiation, together with the calculated monthly-average
daily values for the components of global radiation, horizontal beam and diffuse radiation. The monthly-average hourly and
daily clearsky index values have also been calculated and analyzed. Monthly-average daily frequency distributions of the clearsky
index values are reported for each month.
The annual-average daily global irradiation values are 19.4, 18.67, and 21.78 MJ/m2 and for diffuse irradiation they are 6.34, 6.65 and 6.23 MJ/m2 for Matruh, Cairo and Aswan, respectively. For the normal incidence beam irradiation the annual-average daily values are
16.94 and 24.46 MJ/m2 for Cairo and Aswan, respectively. The annual-average daily fractions of the direct component of horizontal global radiation
are 0.70, 0.61 and 0.72 for the three stations, respectively. The annual-average daily values for the clearsky index are 0.585,
0.566, and 0.648, and the average frequency of clear days annually are 67.3, 42.3 and 77.6% respectively.
The annual variations and trend analysis were analyzed for daily global, direct, and diffuse radiation on a horizontal surface,
daily sunshine duration, and for the daily ratios G/G0, and D/G for the stations Matruh, Cairo and Aswan. The distribution of these components of radiation and their ratios over
the study stations in Egypt is also discussed.
The results show that Egypt is characterized by relatively high average-daily radiation rates, both global and direct, and
a relatively high frequency of clear days. Cairo, due to its urbanization and high pollution, has relatively low average-daily
radiation rates, particularly in direct radiation, and the frequency of clear days.
Received February 26, 1998 Revised February 4, 1999 相似文献
30.
The shallow subsurface structures of the offshore Nile Delta particularly in the southeastern Mediterranean were dealt through the interpretation of 40 two-dimensional seismic reflection lines. The interpretations of seismic reflection data indicated that the principle sedimentary processes affecting the study area include three main structural groups according to their origin and development. The first group of structures comprises of gravity-driven structures, which include slides, slumps, turbidities, and debris flow. Slides are present in three different forms on seismic sections: slide sheets, slides with scar, and wedges of slide materials. Slumps have many geometrical shapes: lenses, spoon-shaped slumps, and slumped blocks bound by growth faults. Debris flows are present as transparent unit (due to the dispersion of seismic waves at debris boundaries), whereas turbidities appear on the seismic profiles, which are formed of closely spaced parallel thin reflectors analogous to their thin stratified bedded layers. The second group of structures is syn-depositional structures, which include growth faults, and tilted and rotated fault blocks. Growth faults are listric in shape and usually dip seaward; displacements along the fault plane increase with depth. Some of these faults are incipient, and some are complicated and intersected by secondary antithetic faults. Most of the growth faults soles out basin wards and in the evaporites layer. Fault blocks are formed due to the Messinian evaporite movement vertically and horizontally due to its mobility as a consequence to the pressure resulted from the overloading of Pliocene sediment. The third group of structures comprises evaporite flow structures such as diapiric structures and graben collapse structures. The surface of the Messinian evaporites was folded during its flow as a consequence to the lateral compression acted on the mobile strata of the Messinian evaporites to form diapiric triangular structures and creates a stress zone faulting and fractures system. These conditions led to the formation of collapse structures or graben collapse structures. 相似文献