Geochemistry and mineral chemistry of pyroxenite xenoliths and host volcanic alkaline rocks from north west of Marand (NW Iran)     

Khezerlou  Ali Akbar  Amel  Nasir  Gregoire  Michel  Moayyed  Mohsen  Jahangiri  Ahmad 《Mineralogy and Petrology》2017,111(6):865-885

Mineralogy and Petrology - The Plio-Quaternary alkaline volcanic rocks from the northwest of Marand (NW Iran) consist of trachy-andesites, trachy-basaltic andesites, leucite-tephrites and...  相似文献   

Comparative modelling approaches of hydro-mechanical processes in sealing experiments at the Tournemire URL     

A. Millard  N. Mokni  J. D. Barnichon  K. Thatcher  A. Bond  A. Fraser-Harris  C. Mc Dermott  R. Blaheta  Z. Michalec  M. Hasal  T. S. Nguyen  O. Nasir  H. Yi  O. Kolditz 《Environmental Earth Sciences》2017,76(2):78

In this paper, a comparative modelling exercise from the DECOVALEX-2015 project is presented. The exercise is based on in situ experiments, performed at the Tournemire Underground Research Laboratory (URL), run by the IRSN (Institut de Radioprotection et de Sûreté Nucléaire), in France. These experiments aim at identifying conditions (e.g. technical specifications, design, construction, and defects) that will affect the long-term performance of swelling clay-based sealing systems, which is of key importance for the safety of underground nuclear waste disposal facilities. A number of materials are being considered as seals; the current work focusses on a 70/30 MX80 bentonite–sand mixture initially compacted at a dry density of 1.94 Mg/m³. The performance of the sealing plug involves at least three different important components, which are the hydro-mechanical behaviour of the bentonite–sand core, the overall permeability of the surrounding argillite, and the influence of the technological gap between the core and the argillite. Two particular tests have been selected for a comparative modelling exercise: the WT-1 test, which was designed to study the rock mass permeability, and the PT-A1 test, which aimed at quantifying the evolution of the hydro-mechanical field within the bentonite–sand core. A number of independent teams have worked towards modelling these experiments, using different codes and input parameters calibrated on additional small-scale laboratory experiments. Their results are compared and discussed.  相似文献   

ASTER mapping of limestone formations and study of caves, springs and depressions in parts of Sultanate of Oman   总被引：1，自引：0，他引：1  

Sankaran Rajendran  Sobhi Nasir 《Environmental Earth Sciences》2014,71(1):133-146

Caves, springs, and large depressions of limestone karst formations are becoming more attractive tourist places and have potential importance on socio-economic development. The present study is a multi-scale point of view on limestone karst, from the space images to microscopic fabric. Here, the karst features consist of limestone formations of Cretaceous (Albian–Cenomanian) age of Tanuf Valley and Tertiary (Late Paleocene–Middle Eocene) age of Sur region of parts of Sultanate of Oman which are mapped in the visible near-infrared and shortwave infrared spectral bands of advanced spaceborne thermal emission and reflection radiometer (ASTER) using decorrelated stretch image processing technique and the occurrences of caves, springs, and depressions of the formations in the field were studied. The decorrelated RGB images of ASTER spectral bands 8, 3, and 1 discriminated well the limestone formations and associated lithology. The limestone formations of Tanuf valley (Natih formations of Hajar unit) are thick-bedded, massive, shallow marine limestone and clayey limestone, which have caves and springs. Large depressions are studied as collapsed structures at the boundary between Abat formations; they consist of gray to white marly or micritic limestone with chert nodules and Seeb Formation of bioclastic limestone, calcarenite, marl, and sandstone of Sur region. Interpretations of limestone formations, their occurrences and distributions of caves, springs and depressions of these regions are verified and confirmed in the field and studied in the laboratory. Occurrences of more springs and depressions in the limestone formations of the study sites are interpreted and located on the Google Earth image. The study proved the capability of ASTER sensor in mapping of limestone formations and recommends the technique to other geographical regions where similar geological questions need to be resolved.  相似文献   

Assessment of Metals Concentration and Ecotoxicology of the Sediment Core of Rehri Creek, Karachi Coast, Pakistan     

Muhammad Z. CHAUDHARY  Nasir AHMAD  Azhar MASHIATULLAH  Sajjad MUNIR  Tariq JAVED 《《地质学报》英文版》2013,87(5):1434-1443

Trace metal concentrations were investigated in a recent sediment core collected from the Rehri Creek area of the Karachi coast,Sindh-Pakistan.The core was sliced horizontally at 2.5-cm intervals to determine grain size,sediment composition,pH,organic matter,and acid-leachable trace metals:cadmium,chromium,copper,lead,and zinc.The trace metals were analyzed by ICP.To separate anthropogenic from geogenic input,several approaches were made,including comparison with sediment quality guidelines—ecotoxicological sense of heavy metal contamination and classification by quantitative indexes.Grain-size analysis and sediment composition of core sample show a sandy nature with neutral pH.Elemental sequence(ES)of the trace metals is in the order of Zn(19.2-109.56 ppm)>Si(66.46-101.71 ppm)>Ba(12.05-26.86 ppm)>As(8.18-17.36 ppm)>Ni(4.2-14.69 ppm)>Cr(3.02-9.62 ppm)>Pb(2.79-6.83 ppm)>Cu(2.2-5.29 ppm)>Co(0.9-2.05 ppm).Thus it is likely that the area may face a serious threat of metal pollution with the present deposition rates unless stringent pollution control norms are adopted.The Sediment Geo-accumulation Index shows that there is no Cr,Cu,Ni,Pb,Zn,or Fe pollution;however,the former index and the Pollution Load Index indicate arsenic pollution in the sediments.  相似文献   

Capability of L-band SAR data in mapping of sedimentary formations of the Marmul region,Sultanate of Oman     

Sankaran Rajendran  Sobhi Nasir 《Earth Science Informatics》2018,11(3):341-357

This study demonstrates the capability of the longer wavelength (L-band) and fine mode images of the Phased Array type L-band Synthetic Aperture Radar (PALSAR), and the optical spectral bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to map sedimentary formations and structures of the Marmul region, Central Oman. Results of study shows that the principal components image of the visible and near infrared–shortwave infrared (VNIR-SWIR) spectral bands of the ASTER have potential to discriminate the occurrence and distribution of marine and Quaternary sedimentary formations of the region. The color composite image developed using PALSAR data (R:HH?+?HV; G:HH; B:HV) has capable to differentiate the occurrence of the sedimentary formations and structures of the region. We developed ratios images by summing the HH intensity as a numerator and the HV intensity as a denominator (R:HH+(HH?+?HV)/HV, G:HH?+?HV, B:HH/HV), and by summing the HV intensity as a numerator and the HH intensity as a denominator (R:HV+(HH?+?HV)/HH, G:HV?+?HH, B:HV/HH) to study better the sedimentary formations and structures. The images discriminated well the occurrence of the limestones and shale formations of the marine deposits, the wadi alluvium of the Quaternary deposits and the manmade building structures of the region. We studied the minerals of the sedimentary formations using VNIR-SWIR spectral bands of the ASTER by spectral angle mapper (SAM) image processing method. The study showed presence of carbonates, silicates and OH bearing aluminosilicate minerals in the formations. The image interpretations are verified in the field and confirmed by the laboratory studies.  相似文献   

The distribution and population dynamics of O-group plaice (Pleuronectes platessa L.) on nursery grounds in the Firth of Forth     

M. G. Poxton  N. A. Nasir 《Estuarine, Coastal and Shelf Science》1985,21(6):845-857

Midsummer (1 August) population estimates of about 2 million O-group plaice (Pleuronectes platessa L.) were derived for sandy bays around the Firth of Forth in 1979–1980. This is an order of magnitude less than similar estimates made for the Clyde Sea Area in 1973–1974. Autumn population estimates of 0·4–1·0 million fish were comparable to estimates by the Ministry of Agriculture, Fisheries and Food for the area between the Scottish border and Flamborough Head (2·3 million for 1970 and 1973) which represented 4·8% (1973) to 5·3% (1970) of the total number of O-group fish on the English east coast.Largo Bay was the most important nursery area holding 25% of the total population. It is particularly well situated to receive newly metamorphosed plaice carried in water currents along the north side of the Forth from the spawning ground off Fife Ness. Plaice in the Forth are mainly distributed on fine to medium sandy beaches (186–480 μm), the mean number per haul in midsummer (D) being correlated with the median diameter (m.d. in μm) of the low water sediments by the equation: D=−45·7666+0·2327 m.d. (n=11,r=0·68,P<0·02 but>0·01).The shallow inshore water in sandy bays in the outer Firth was well mixed and more marine than estuarine (27·7–35·0‰). The correlation coefficient between fish density and water temperature was low, while that with salinity (S‰) was: D=6·1618+0·2238S (n=23,r=0·62,P<0·005).Regression analysis demonstrated that the relationship between the instantaneous mortality rate (Z) and the initial population density (D_p) was: Z×100=0·7480+0·0546d_p (n=12,r=0·87,P<0·001).The mean mortality rate for the O-group plaice in the Forth nursery areas was 53% month⁻¹.  相似文献   

Shear behaviour of cemented pastefill-rock interfaces     

O. Nasir  M. Fall   《Engineering Geology》2008,101(3-4):146-153

The shear stress–strain behaviour and shear strength parameters of the interface between cemented paste backfill (CPB) and rock are of practical importance in the optimal and safe design of CPB structures. An understanding of the shear behaviour and properties at this interface is also required to develop comprehensive interface models for CPB-rock analyses, interface design methods for the static and dynamic stability analysis of CPB structures, and building high performance CPB structures. In this study, direct shear tests were conducted to investigate the interface shear strength behaviour between CPB and rock. All tests were carried out in a standard direct shear test apparatus for a range of curing ages of 1 to 28 days for the CPB. The procedures of the laboratory tests will be described. Results will be presented for interface shear behaviour, including stress–strain curves, vertical deformation and shear strength parameters. The test results show that the shear strength parameters and behaviour of the CPB-rock interface are time-dependent and significantly influenced by the normal load.  相似文献   

Geology and petrology of the Hormuz dolomite, Infra-Cambrian: Implications for the formation of the salt-cored Halul and Shraouh islands, Offshore, State of Qatar     

Sobhi Nasir  Hamad Al-Saad  Abudlrazak Alsayigh  Oliver Weidlich 《Journal of Asian Earth Sciences》2008,33(5-6):353-365

Geological investigations of the Halul and the Shraouh islands, offshore Qatar, indicate that most of their calcareous rocks, which display abundant stromatolitic bedding, belong to the Infra-Cambrian Hormuz Series. Mineralogical, petrological, and geochemical analyses show that these calcareous rocks consist dominantly of dolomite and have formed in a reducing depositional environment. Faint laminations and small streaks of organic matter furnish evidence for the involvement of algal mats in their genesis and indicate their formation in an intertidal to supratidal setting. The Halul and Shraouh dolomites experienced extensive recrystallization and sulfatization during the emplacement of the Halul and Shraouh salt domes that form the cores of the islands. During mobilization and ascent of the salt, the dolomite recrystallized, and its Sr initial ratios were abnormally enhanced by the incorporation of ⁸⁷Sr from a source, which is more radiogenic than the attendant seawater at the time of the dolomite formation near the Proterozoic–Cambrian boundary. Geochemical analysis show that Si, Al, Ti Zr, and % of insoluble residue are highly correlative, suggesting the presence of detrital minerals such as rutile and zircon. A paleosabkha model may well agree with this chemical signature. However, the Infra-Cambrian age of the Hormuz rocks and the presence of stromatolitic layers containing organic materials in the studied rocks, suggest that organogenic dolomitization could be an alternative dolomitization model.  相似文献   

Modelling of the hydro-mechanical response of sedimentary rocks of southern Ontario to past glaciations     

O. Nasir  M. Fall  T.S. Nguyen  E. Evgin 《Engineering Geology》2011,123(4):271

Glaciation is considered as one of the main natural processes that can have a significant impact on the long term performance of a deep geological nuclear waste repository (DGR) located in the Northern Hemisphere. The northern part of the American continent has been subjected to a series of strong glaciation and deglaciation events over the past million years. The last glacial cycle in the Northern Hemisphere started approximately 110,000 year ago. During that cycle, southern Ontario was buried under a continental ice sheet, with a maximum thickness of up to 3000 m at about 20,000 years ago. The ice cap retreated approximately 10,000 years ago. However, field data from deep boreholes in sedimentary rocks of southern Ontario show anomalous pore water pressure including underpressure and overpressure zones. In this paper, a large-scale coupled hydro-mechanical (HM) model is developed to investigate the hydro-mechanical (HM) response of the sedimentary rocks of southern Ontario to past glacial cycles. Particular emphasis has been placed on the evolution of pore water pressures and surface displacements. The HM model is verified using analytical solutions. The results of the large-scale HM modeling study shows that the past glaciation, particularly the second cycle (22,000 apb) had significant impact on the pore water pressure gradient and effective stress distribution in the sedimentary rocks of southern Ontario. Furthermore, good agreement between the large scale modeling results and anomalous pressures leads us to the conclusion that these anomalies could be glacially induced. The results of this research can provide information that will contribute to a better understanding of the impact of future glaciations on the long term performance of DRGs in sedimentary rocks.  相似文献   

Petrogenesis of early cretaceous carbonatite and ultramafic lamprophyres in a diatreme in the Batain Nappes,Eastern Oman continental margin   总被引：1，自引：0，他引：1  

S. Nasir  S. Al-Khirbash  H. Rollinson  A. Al-Harthy  A. Al-Sayigh  A. Al-Lazki  T. Theye  H.-J. Massonne  E. Belousova 《Contributions to Mineralogy and Petrology》2011,161(1):47-74

Allochthonous carbonatite and ultramafic lamprophyre occur in a diatreme at the beach of the Asseelah village, northeastern Oman. The diatreme consists of heterogeneous deposits dominated by ‘diatreme facies’ pyroclastic rocks. These include aillikite and carbonatite, which intrude late Jurassic to early Cretaceous cherts and shales of the Wahra Formation within the Batain nappes. Both rock types are dominated by carbonate, altered olivine, Ti–Al–phlogopite and Cr–Al–spinel and contain varying amounts of apatite and rutile. The carbonatite occur as fine-grained heterolithic breccias with abundant rounded carbonatite xenoliths, glimmerite and crustal xenoliths. The aillikite consists of pelletal lapilli tuff with abundant fine-grained carbonatite autoliths and crustal xenoliths, which resemble those in the carbonatite breccia. The aillikite and carbonatite are characterized by low SiO₂ (11–24 wt%), MgO (9.5–12.4 wt%) and K₂O (<0.3 wt%), but high CaO (18–22 wt%), Al₂O₃ (4.75–7.04 wt%), Fe₂O_3tot (8.7–13.8 wt%) and loss-on-ignition (24–30 wt%). Higher CaO, Fe₂O_3total, Al₂O₃, MnO, TiO₂, P₂O₅ and lower SiO₂ and MgO content distinguish carbonatite from the aillikite. The associated carbonatite xenoliths and autoliths have intermediate composition between the aillikite and carbonatite. Mg number is variable and ranges between 58 and 66 in the carbonatite, 66 and 72 in the aillikite and between 48 to 64 in the carbonatite autoliths and xenoliths. The Asseelah aillikite, carbonatite, carbonatite xenoliths and autoliths overlap in most of their mineral parageneses, mineral composition and major and trace element chemistry and have variable but overlapping Sr, Nd and Pb isotopic composition, implying that these rocks are related to a common type of parental magma with variable isotopic characteristics. The Asseelah aillikite, carbonatite and carbonatites xenoliths are LREE-enriched and significantly depleted in HREE. They exhibit similar smooth, subparallel REE pattern and steep slopes with (La/Sm) _n of 6–10 and relative depletion in heavy rare earth elements (Lu = 3–10 chondrite). Initial ⁸⁷Sr/⁸⁶Sr ratios vary from 0.70409 to 0.70787, whereas initial ¹⁴³Nd/¹⁴⁴Nd ratios vary between 0.512603 and 0.512716 (εNd _i between 2.8 and 3.6). ²⁰⁶Pb/²⁰⁴Pb _i ratios vary between 18.4 and 18.76, ²⁰⁷Pb/²⁰⁴Pb _i ratios vary between 15.34 and 15.63, whereas ²⁰⁸Pb/²⁰⁴Pb _i varies between 38.42 and 39.05. Zircons grains extracted from the carbonatite have a mean age of 137 ± 1 Ma (95% confidence, MSWD = 0.49). This age correlates with large-scale tectonic events recorded in the early Indian Ocean at 140–160 Ma. Geochemical and isotopic signatures displayed by the Asseelah rocks can be accounted for by vein-plus-wall-rock model of Foley (1992) wherein veins are represented by phlogopite, carbonate and apatite and depleted peridotite constitutes the wall-rock. The carbonatite and aillikite magmatism is probably a distal effect of the breaking up of Gondwana, during and/or after the rift-to-drift transition that led to the opening of the Indian Ocean.  相似文献