Relative performance of CMIP5 and CMIP6 models in simulating rainfall in Peninsular Malaysia     

Pour  Sahar Hadi  Shahid  Shamsuddin  Mainuddin  Mohammed 《Theoretical and Applied Climatology》2022,149(1-2):709-725

Theoretical and Applied Climatology - This study evaluated the skills of global climate models (GCMs) of the fifth and sixth Coupled Model Intercomparison Project (CMIP5 and CMIP6) in simulating...  相似文献   

The Sabzevar blueschists of the North-Central Iranian micro-continent as remnants of the Neotethys-related oceanic crust subduction     

Hadi Omrani  Mohssen Moazzen  Roland Oberhänsli  Uwe Altenberger  Manuela Lange 《International Journal of Earth Sciences》2013,102(5):1491-1512

The Sabzevar ophiolites mark the Neotethys suture in east-north-central Iran. The Sabzevar metamorphic rocks, as part of the Cretaceous Sabzevar ophiolitic complex, consist of blueschist, amphibolite and greenschist. The Sabzevar blueschists contain sodic amphibole, epidote, phengite, calcite ± omphacite ± quartz. The epidote amphibolite is composed of sodic-calcic amphibole, epidote, albite, phengite, quartz ± omphacite, ilmenite and titanite. The greenschist contains chlorite, plagioclase and pyrite, as main minerals. Thermobarometry of a blueschist yields a pressure of 13–15.5 kbar at temperatures of 420–500 °C. Peak metamorphic temperature/depth ratios were low (~12 °C/km), consistent with metamorphism in a subduction zone. The presence of epidote in the blueschist shows that the rocks were metamorphosed entirely within the epidote stability field. Amphibole schist samples experienced pressures of 5–7 kbar and temperatures between 450 and 550 °C. The presence of chlorite, actinolite, biotite and titanite indicate greenschist facies metamorphism. Chlorite, albite and biotite replacing garnet or glaucophane suggests temperatures of >300 °C for greenschist facies. The formation of high-pressure metamorphic rocks is related to north-east-dipping subduction of the Neotethys oceanic crust and subsequent closure during lower Eocene between the Central Iranian Micro-continent and Eurasia (North Iran).  相似文献   

Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq     

Hossein Azizi  Ayten Hadi  Yoshihiro Asahara  Youssef Osman Mohammad 《Central European Journal of Geosciences》2013,5(4):523-537

The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ? _Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.  相似文献   

Lithological Mapping in the Eastern Part of the Central Iranian Volcanic Belt Using Combined ASTER and IRS data   总被引：1，自引：0，他引：1  

Seyed Mohammad Hadi Hadigheh  Hojjatollah Ranjbar 《Journal of the Indian Society of Remote Sensing》2013,41(4):921-931

The study area is located in the eastern part of the central Iranian volcanic belt. Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) and Indian Remote Sensing Satellite (IRS ) pan images were used for applying several image classification methods for lithological mapping. ASTER visible-near infrared and shortwave infrared bands were sharpened using IRS pan image. We used classification methods such as Maximum likelihood, Spectral Angle Mapper (SAM) and Spectral Information Divergence (SID) in order to evaluate the usefulness of these methods for geological mapping. The classification results showed that MLC has the best accuracy and the classified image closely resembles the previously prepared geology map of the area.  相似文献   

Geochemical characterization and modelling of the Toarcian/Domerian porewater at the Tournemire underground research laboratory     

J. Tremosa  D. Arcos  J.M. Matray  F. Bensenouci  E.C. Gaucher  C. Tournassat  J. Hadi 《Applied Geochemistry》2012

For safety evaluation of hazardous waste repositories in clay-rocks, a thorough assessment of porewater chemistry and water–rock interactions is required. However, this objective is a challenging task due to the low hydraulic conductivity and water content of such rocks, which subsequently renders porewater sampling difficult (without inducing perturbations). For this reason, an indirect approach was developed to determine porewater composition of clay-rocks, by a geochemical model of water–rock interaction using some properties of the rock and the solution. The goal of this paper is to obtain the porewater composition of the Toarcian/Domerian argillaceous formation at Tournemire (South of France), for which a reliable model is still lacking. The following work presents a comprehensive characterization of the geochemical system of the Tournemire clay-rock, including mineralogy, petrology, mobile anions, cation exchange properties, accessible porosity and CO₂ partial pressure. Perturbation corrections from fracture water sampling were also computed. These water were found in sealed fractures (Beaucaire et al., 2008) and their radiocarbon apparent age is estimated at 20 ka. Their age together with their equilibrium situation allow considering these fracture waters as representative of the formation porewater. The model developed to calculate the Tournemire porewater composition is essentially based on cation exchange by a multi-site approach, but equilibrium with some mineral phases (calcite, quartz and pyrite) is also considered. Different exchange sites of different affinities towards cations are used, which proportions are given by the mineralogy. Exchange on illite is performed with a three-sites model, while one site is considered for smectite phases. Multi-site model results are compared with corrected fracture water data and two other models: a model only based on mineral equilibrium and a model using cation exchange on one global site. The best results were obtained with the models that take into account cation exchange and particularly with the multi-site model. The interest in considering a model with exchange sites of different affinities is particularly obvious for a satisfactory representation of the K⁺ content in solution. A dependence of K⁺ content to the amount of high affinity sites was observed, leading to an improvement of its simulation when uncertainty on mineralogical data is considered. Once validated, the multi-site model was applied at different levels of the Tournemire argillaceous formation to obtain a profile of the porewater composition.  相似文献   

Shrinkage Properties of Soft Clay Treated with Cement and Geofibers   总被引：4，自引：2，他引：2  

Behzad Fatahi  Thu Minh Le  Behnam Fatahi  Hadi Khabbaz 《Geotechnical and Geological Engineering》2013,31(5):1421-1435

In this study, effects of two types of geofibers, namely polypropylene and recycled carpet, on three dimensional shrinkage properties of cement treated kaolinite and bentonite clays are investigated. Cement treated clay specimens were prepared with cement contents of 5, 10, and 15 % by weight of dry soil for kaolinite samples, and 30, 40 and 50 % for bentonite samples. To investigate and understand the influence of different fiber types and contents, three different percentages of fiber content (i.e. 0.1, 0.2 and 0.5 % polypropylene fibers; and 0.5, 0.75 and 1 % carpet fibers) were adopted. The results of shrinkage tests on 126 cylindrical samples of cement treated clay with various cement and fiber contents were analysed to understand the relationships between these parameters and the shrinkage percentage of treated soil. Results of this study indicate that combination of cement and fiber is effective in reducing the volume change of clayey soils undergoing drying process. In the applied ranges of cement and fiber contents, the influence of cement addition on the shrinkage reduction is more significant than the addition of fibers for the treated kaolinite. However, addition of fibers in curtailing the shrinkage of bentonite clay is more significant than the cement addition.  相似文献   

Pseudo-static bearing capacity of shallow foundations on heterogeneous marine deposits using limit equilibrium method     

Ardavan Izadi  Mahsa Nazemi Sabet Soumehsaraei  Ali Ghorbani 《Marine Georesources & Geotechnology》2013,31(10):1163-1174

Abstract

By application of the limit equilibrium method associated with Coulomb failure mechanism, the effect of variation of undrained shear strength with depth on seismic bearing capacity was evaluated. The approach followed in this study to take into account seismic forces is pseudo-static. It is also assumed that the occurrence of an earthquake does not have any effects on the values of soil cohesion. Two different marine soil deposits exhibiting linear and bilinear variations of undrained shear strength with depth were considered. The undrained bearing capacity factor has been computed as a function of dimensionless parameters of λ₁B/c₀, λ₂B/c₀, and Z_t/B. The results of this paper have been compared with solutions reported in the literature, and the consistency of the results confirmed the ability of Coulomb failure mechanism and its corresponding limit equilibrium method formulation in static condition. Furthermore, the pseudo-static bearing capacity of shallow foundations on heterogeneous marine deposit is addressed. Finally the results of this study presented in the form of table and design charts.  相似文献   

Editorial     

Hadi Hajibeygi  Jan Dirk Jansen  Olwijn Leeuwenburgh  Denis Voskov 《Computational Geosciences》2017,21(5-6):833-833

  相似文献   

Groundwater Origin in Qanats,Chemo-Isotopic,and Hydrogeological Evidence     

Hojat Mirani Moghadam  Rahim Bagheri  Gholam Hossein Karami  Hadi Jafari 《Ground water》2020,58(5):771-776

A systematic study of the chemo-isotopic characteristics and origin of the groundwater was carried out at six major qanats in the hyper-arid Gonabad area, eastern Iran. These qanats as a sustainable groundwater extraction technology have a long history, supporting human life for more than a thousand years in this region. The Gonabad qanats are characterized by outlet electrical conductivity (EC) values of 750 to 3900 µS/cm and HCO₃-Na-Mg and Cl-Na water types. The Gonabad meteoric water line (G_nMWL) was drawn at the local scale as δ²H = 6.32×δ¹⁸O + 8.35 (with R² = 0.90). It has a lower slope and intercept than the global meteoric water line due to different water vapor sources and isotope kinetic fractionation effects during precipitation in this arid region. The altitude effects on isotopic content of precipitation data were derived as δ¹⁸O = (−0.0031 × H_(m.a.s.l))−1.3). The δ²H and δ¹⁸O isotopes signatures demonstrate a meteoric origin of the groundwater of these qanats. The shift of the qanat's water samples from the local meteoric water line (LMWL) in a dry period with higher temperatures is most probably due to evaporation during the infiltration process and water movement in qanat gallery. Based on the isotopic results and mass balance calculations, the qanats are locally recharged from an area between 2000 to 2400 m.a.s.l of nearby carbonate formations and coarse alluvial sediments. The dissolution of evaporate interlayers in Neogene deposits deteriorates the groundwater quality, especially in Baidokht qanat.  相似文献   

Composition and structure of species along altitude gradient in Moghan-Sabalan rangelands,Iran     

Sahar Ghafari  Ardavan Ghorbani  Mehdi Moameri  Raoof Mostafazadeh  Mahmood Bidarlord 《山地科学学报》2018,15(6):1209-1228

This study provides a checklist of species distributed at the altitude gradient of Moghan-Sabalan rangelands in Ardabili province, Northwest Iran. We evaluated the changes in species composition, growth types of species, Raunkiaer’s life forms, geographical distribution, threat and endemicity status, and palatability of species along two altitudinal gradients in the sampling plots, which were conducted in eleven sites/habitats with 300 meters above sea level (masl) altitude intervals (from 100 to 3300 masl). We assessed the plant species composition with special reference to the gradient analysis, and identified overall 396 species, which was comprising 44 families and 194 genera. Results showed that Asteraceae family is by far the most species-rich family, followed by Poaceae, Fabaceae, Caryophyllaceae and Brassicaceae. Among the genera, Astragalus is the most diverse genus, followed by Allium, Veronica and Bromus, Galium, Silene and Ranunculus. Results indicated that the number of species increased as the altitude increased to 1200–1500 masl, but then starts to decline to 3300 masl. Family-to-genera ratio was 1:4.4, the family-tospecies ratio was 1:9, and the genera-to-species ratio was 1:2.04. Growth type of species analysis shows that the frequency of perennial plants was higher in the study area followed by annual species while the lower group was biennial species. The number of annuals showed a decreasing trend towards higher altitude. Hemicryptophytes and therophytes were the most frequent life forms constituted each with (41.9%). Hemicryptophytes showed an increasing trend with altitude, while therophytes showed a decreasing trend with altitude increase, followed by geophytes, chamaephytes, and phanerophytes. Results showed more than half of the species of the study area belonged to Iran-Turanian region and these species showed an increasing trend with altitude. In contrast, Sahara-Sindian species comprise a minor component of the spectrum, with decreasing trend with altitude. The rare and endangered species out of the surveyed taxonomic groups comprised 53 species in total which 29 of them are considered lower risk (LR), 13 data deficient (DD), 5 vulnerable (Vu) and with 3 rare (R) and identified endemic plants comprised 24 species. Some 56.6% species were identified as class III, 22.6% were class I and 20.8% were class II as the palatability variation. Moghan-Sabalan rangelands require strong conservation management policies in case of species loss and changing natural communities due to the occurrence of conversion into cropland, over-grazing and other anthropogenic effects.  相似文献