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231.
232.
The Indian subcontinent has been colliding against Asia along the Himalayas. Hindu Kush and Burma in this collision zone have intermediate-depth seismicities beneath them, with most of the continental crust subducted into a few hundred km depth. The subduction, not collision, in these regions is an enigma long time. We show that the continental lithosphere subducted beneath Hindu Kush and Burma traveled over the Reunion and Kerguelen hotspots from 100 Ma to 126 Ma and is likely to have been metasomatized by upwelling plumes beneath those hotspots. The devolatilization of the metasomatized lithosphere impinging on the collision boundary would have provided a high pore fluid pressure ratio at the thrust zones and made the subduction of the continental lithosphere in these regions possible. The subducted lithosphere could give intermediate-depth seismicities by devolatilization embrittlement. Such subduction of hotspot-affected lithosphere without accompanying any oceanic plate would be one candidate for producing ultrahigh-pressure metamorphic rocks by deep subduction of the continental crust. 相似文献
233.
Ziaur Rehman Ansari L. A. K. Rao Sameer Saran 《Journal of the Geological Society of India》2013,81(6):827-834
A detailed geological, geomorphological and landuse/landcover study has been carried in a small watershed of Himalaya by visual interpretation of FCC prepared from band 123 of ASTER satellite imagery. On the basis of interpretation and field check, major litounits identified in the study area include Lesser Himalaya conglomerate consisting of quartzite, granite, phyllite boulder and pebble, Middle Siwalik sandstone and Upper Siwalik boulder beds and valley fill with Doon gravel of Holocene age. Geomorphologically the study area is characterized by typical Himalayan topography with rugged terrain. Various landforms identified and recognized include, Doon Fan Gravel Terrace, Doon Fan Gravel Dissected hill, Sub Recent Fan Terrace, Moderately Dissected Structural Hill, Piedmont Dissected Slope, River Terrace, Channel Bar and River channel. Supervised classification of ASTER False Colour Composite (FCC) (123) shows that the major landuse category in the study area is agriculture while major landcover class is forest covered land. The study shows the effect of geology and geomorphology on the type of landuse and landcover in an active tectonic zone of the study area. 相似文献
234.
Warren W. Wood Richard M. Bailey Brian A. Hampton Thomas F. Kraemer Zhong Lu David W. Clark Rhodri H.R. James Khalid Al Ramadan 《Quaternary Research》2012,77(2):215-220
The coastline along the southern Arabian Gulf between Al Jubail, Kingdom of Saudi Arabia, and Dubai, UAE, appears to have risen at least 125 m in the last 18,000 years. Dating and topographic surveying of paleo-dunes (43–53 ka), paleo-marine terraces (17–30 ka), and paleo-marine shorelines (3.3–5.5 ka) document a rapid, > 1 mm/a subsidence, followed by a 6 mm/a uplift that is decreasing with time. The mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the Arabian plate or, alternatively, by movement of the underlying Infracambrian-age Hormuz salt in response to sea-level changes associated with continental glaciation. Independent of the mechanism, rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants, airports, and artificial islands as well as the interpretation of sedimentation and archeology of the area. 相似文献
235.
Naoual Gamrani Khalid R’kha Chaham Mouncif Ibnoussina Fabio Fratini Luisa Rovero Ugo Tonietti Mohammed Mansori Lehcen Daoudi Claude Favotto Nasrrddine Youbi 《Environmental Earth Sciences》2012,66(1):129-140
This work focuses on the building material used in the Saadian sugar refinery of Chichaoua (about 70 km southwest of Marrakesh).
The study involved a classification of different types of rammed earth, followed by their mineralogical characterization based
on optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). These studies are complemented by chemical
investigations, X-ray fluorescence, and thermal analysis (DTA and TGA). The results demonstrate the use of two types of earth
for the realisation of rammed earth, the first one non-plastic, -grained with added lime, the other one of low plasticity,
and fine grained without addition of lime. Mechanical tests on site and in laboratory how at the first type of material exhibits
great strength, exceeding the values known for rammed earth. 相似文献
236.
This paper presents the results of an experimental programme to study load oscillation in granular materials. Spherical glass beads were used in the investigation. Cylindrical specimens were compressed under axisymmetric triaxial loading condition at 25,100,250 and 400 kPa confining pressures. The test parameters included: (i) particle size; (ii) gradation (uniform versus non‐uniform specimens); (iii) confining pressure; (iv) loading rate; and (v) specimen density. In general, a slight post‐peak principal stress softening was observed as well as a continuous volume increase (dilation) even at relatively high strains. This appears to be caused by the uniform shape and smooth surface of the spherical particles. Load oscillations were observed in the very small, small, and well‐graded beads at each confining pressure. For the medium beads, the oscillations appeared at high confining pressure (250 and 400 kPa), and they did not appear in the large beads. The influences of the confining pressure, loading rate, particle size, gradation and specimen density on load oscillation are presented and discussed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
237.
Khalid Omar Murtaza 《国际地球制图》2017,32(2):188-205
Using Landsat data at decadal interval (1980–2013), the glacier fluctuations (glacier area, equilibrium line altitude and specific mass balance) of nine benchmark glaciers in Kashmir Himalaya were estimated. The observed changes were related to topographic and climatic variables in order to understand their influence. From the data analysis, it was observed that the glaciers have shrunk by 17%, ELA has shifted upwards (80–300 m) and SMB shows variation in glacier mass loss from ?0.77 to ?0.16 m.w.e. Annual air temperature showed a significant increasing trend, and a slight but insignificant decrease in precipitation was observed during the period. It is evident that in the same climatic regime, varying topography plays a key role in determining the glacier changes. It is believed that the observed changes in the glacier geometry and dynamics, if continued, shall have adverse effect on the streamflows, water supplies and other dependent sectors in the region. 相似文献
238.
Nisar Ahmed Tayyaba Kausar Perveiz Khalid Sohail Akram 《Journal of the Geological Society of India》2018,91(6):736-742
Petrophysical evaluation and rock physics analysis are the important tools to relate the reservoir properties like porosity, permeability, pore fluids with seismic parameters. Nevertheless, the uncertainties always exist in the quantification of elastic and seismic parameters estimated through wireline logs and rock physics analysis. A workflow based on statistical relationships of rock physics and logs derived elastic and seismic parameters with porosity and the percentage error exist between them is given. The statistical linear regressions are developed for early Eocene Chorgali Formation between various petrophysically factors determined from borehole logging of well Ratana–03 drilled in tectonically disturbed zone and the seismic and elastic parameters estimated through rock physics modeling. The rock physics constraints such as seismic velocities, effective density and elastic moduli calculated from Gassmann fluid substation analysis are in harmony and close agreement to those estimated from borehole logs. The percentage errors between well logs and rock physics computed saturated bulk modulus (K sat ), effective density (ρ eff ), compressional and shear wave velocities (V P and V S) are 1.31%, 4.23 %, 5.25% and 4.01% respectively. The permeability of reservoir intervals show fairly strong linear relationship with the porosity, indicating that the reservoir interval of the Chorgali Formation is permeable and porous thus having large potential of hydrocarbon accumulation and production. 相似文献
239.
Nihad M. Karo Roland Oberhänsli Ahmed M. Aqrawi Elias M. Elias Khalid J. Aswad Masafumi Sudo 《Arabian Journal of Geosciences》2018,11(10):234
The Northern Zagros Suture Zone (NZSZ), formed as a result of the collision between Arabian and Sanandaj-Sirjan microplate, is considered as part of the Zagros orogenic belt. NZSZ is marked by two allochthonous thrust sheets in upward stacking order: lower and upper allochthon. The Bulfat complex is a part of the upper allochthon or “Ophiolite-bearing terrane” of Albian-Cenomenion age (97–105 Ma). Voluminous highly sheared serpentinites associated with ophiolites occur within this upper allochthon. In addition, the Gemo-Qandil Group is characterized by gabbroic to dioritic Bulfat intrusion with a crystallization age spanning from ~45 to ~?40 Ma, as well as extensive metapelites with contact to the Walash-Naupurdam metavolcanic rocks. Due to the deformation in the Sanandaj-Sirjan Zone along the eastern side of the Iraqi segment of NZSZ, the Gemo-Qandil Group was regionally metamorphosed during late Cretaceous (~?80 Ma). This tectono-compressional dynamics ultimately caused an oscillatory deformation against Arabian continental margin deposits as well. During these events, gabbro-diorite intrusion with high-grade contact metamorphic aureoles occurred near Bulfat. Thus, there is an overlap between regional and contact metamorphic conditions in the area. The earlier metamorphic characteristic can be seen only in places where the latter contact influence was insignificant. Generally, this can only observed at a distance of more than 2.5 km from the contact. According to petrographic details and field observations, the thermally metamorphosed metapelitic units of the metasediment have been completely assimilated, with only some streaks of biotite and relicts of initial foliation. They strongly resemble amphibolite-grade slices from the regional metamorphic rocks in the region. Metapelitic samples far from the intrusion give similar biotite cooling ages as the intrusive rocks. Thus, they may be affected by the same thermal event. 40Ar/39Ar dating of biotite in metapelite rocks of Bulfat by step-wise heating with laser gave average weighted isotopic ages of 34.78?±?0.06 Ma. This is interpreted as crystallization/recrystallization age of biotite possibly representing the time of cooling and uplift history of the Bulfat intrusion. Cooling and exhumation rates for the Bulfat gabbro-diorite rocks were estimated as ~?400 °C/Ma and ~?3.3 mm/year respectively. According to petrographic details, field observations and Ar/Ar dating concerning the contact metamorphism near Bulfat due to the gabbro-diorite intrusion, no significant deformation is visible during exhumation processes after the Paleogene tectono-thermal event, indicating that isotopic ages of 34.78?±?0.06 Ma could mark the timing of termination of the island arc activity in the Ophiolite-bearing terrane (upper allochthon). 相似文献
240.
Meriem Snineh Nour-Eddine Laftouhi Khalid Mehdi Abdenbi El Mandour Abdessamad Hejjaj Laila Mandi 《Environmental Earth Sciences》2018,77(3):102
The Bleida fractured aquifer is not well studied in terms of water resources as previous geophysical investigations in this area were undertaken for mining purposes. This study utilized magnetic resonance sounding surveys in order to define the distribution of water resources in the region of Bleida and to locate areas favorable for the drilling and construction of productive hydraulic boreholes. For this purpose, eight magnetic resonance sounding surveys were conducted in two sites at the intersection of faults in basement rocks. The results of these surveys indicated that there were two distinct levels of saturation in fractured rock that decreased with depth. 相似文献