Monitoring gas leakages simulated in a near surface aquifer of the Ellerbek paleo-channel     

Said A. al Hagrey  Dirk Schäfer  Daniel Köhn  Carla E. Wiegers  David Chung  Andreas Dahmke  Wolfgang Rabbel 《Environmental Earth Sciences》2016,75(14):1083

  相似文献   

Small dam reservoir siltation in the Atlas Mountains of Central Morocco: analysis of factors impacting sediment yield     

Naima Alahiane  Ahmed Elmouden  Abderrahmane Aitlhaj  Said Boutaleb 《Environmental Earth Sciences》2016,75(12):1035

  相似文献   

Structural boundaries delimitation from geomagnetic data using the continuous wavelet transform. Application to Hoggar (Algeria)     

Sid-Ali Ouadfeul  Said Eladj  Leila Aliouane 《Arabian Journal of Geosciences》2012,5(3):365-370

The main goal of the proposed work is to delineate structural boundaries in a very complex geology environment using the spatial and statistical properties of the potential field data. The analysis is performed using magnetic anomaly of the total field data over In Ouzzal, an Archaean north–south elongated block belonging to the Hoggar (Algeria). This region is geologically and geophysically very poorly known except some localized areas. The intrinsic properties of high-frequency signals and the related causative sources are explored, thanks to two-dimensional continuous wavelet transform. The obtained results, represented by spatial distribution of the maxima of the modulus of the wavelet transform at each scale, clearly show that the major magnetic singularities of the field may be related to geological features. Comparison with the Euler’s deconvolution solutions exhibits a very good correlation. Even though where geological structures are known, our method shows better resolution and accuracy. The proposed multiscale method proves to be more powerful, easy to use, and versatile where classical methods of potential field interpretation fail or are very constraining. However, work is still ongoing to try to better and fully characterize the causative sources of the potential fields.  相似文献   

Hornblende gabbros of Wadi Az Zarib area,Central Eastern Desert,Egypt: opaque mineralogy,geochemistry, tectonic setting,and petrogenesis     

Mohamed W. Ali-Bik  Said H. Abd El Rahim  Wael Abdel Wahab 《Arabian Journal of Geosciences》2014,7(10):4009-4027

A small intrusive fresh gabbroic mass intrudes the Neoproterozoic metasediments and Dokhan volcanics of Wadi Az Zarib area, Central Eastern Desert. It is composed of hornblende gabbros and leuco-hornblende gabbros. Their petrography, opaque mineralogy, and geochemistry are addressed to elucidate their tectonic setting and petrogenesis. They represent a subduction-related calc–alkaline magma that evolved in an island arc setting. In terms of maturity, the supposed arc represents an intermediate stage between continental arc and active continental margin. Thermobarometry and physical–chemical data of the parent magma as deduced from compositions of amphiboles, biotite, and plagioclase indicate crystallization temperatures of 931–825 °C at pressures of 6.16–4.01 kbar and H₂O_melt of 6.4–5.2 wt%. Data, as presented, argue in favor of fractional crystallization mechanism to be accounted to the present suite to interpret the observed variations. The evolution of the suite from hornblende gabbros to leuco-hornblende gabbros was accompanied by decreasing of MgO, CaO, Cr, and Ni with simultaneous increasing of Al₂O₃, TiO₂, Na₂O, K₂O, Ba, Rb, Sr, La, and Ce. Residuals calculated during mass balance fractional crystallization modeling suggest that brown and green hornblendes are the main fractionated phases which derived the melt composition towards the leuco-hornblende gabbros.  相似文献   

Modelling the effect of temperature on unsaturated soil behaviour     

Matthieu Dumont  Said Taibi  Jean-Marie Fleureau  Nabil Abou Bekr  Abdelghani Saouab 《Comptes Rendus Geoscience》2010,342(12):892-900

A simple thermohydromechanical (THM) constitutive model for unsaturated soils is described. The effective stress concept is extended to unsaturated soils with the introduction of a capillary stress. This capillary stress is based on a microstructural model and calculated from attraction forces due to water menisci. The effect of desaturation and the thermal softening phenomenon are modelled with a minimal number of material parameters and based on existing models. THM process is qualitatively and quantitatively modelled by using experimental data and previous work to show the application of the model, including a drying path under mechanical stress with transition between saturated and unsaturated states, a heating path under constant suction and a deviatoric path with imposed suction and temperature. The results show that the present model can simulate the THM behaviour in unsaturated soils in a satisfactory way.  相似文献   

Structural Setting of Northern Tunisia Insights from Gravity Data Analysis Jendouba Case Study     

Imen Hamdi Nasr  Adnen Amiri  Mohamed Hédi Inoubli  Abdelhmid Ben Salem  AbdelHak Chaqui  Said Tlig 《Pure and Applied Geophysics》2011,168(10):1835-1849

Detailed gravity data in conjunction with available surface geology are analyzed to infer the organization of the underlying structures in Jendouba area. Gravity data analysis benefits from the gravity Bouguer anomaly, upward continuations, residual distribution, derivatives and Euler deconvolved maps. The main results display a positive amplitude gravity anomaly as the response of Triassic evaporitic bodies and important NE trending features at the boundaries between the Triassic outcrops and their enveloping strata. Integration of gravity, geological and structural maps let to the identification of major structural directions and trends of the study area. It confirms some structural elements gathered from outcrops. It defines also new ones.  相似文献   

Behaviour of Ni-PGE-Au-Cu in mafic-ultramafic volcanic suites of the 2.7 Ga Kambalda Sequence, Kalgoorlie Terrane, Yilgarn Craton     

Nuru Said  Robert Kerrich  Campbell McCuaig 《Geochimica et cosmochimica acta》2011,75(10):2882-2910

The 2.7 Ga Kambalda Sequence comprises a mafic to ultramafic dominated volcanic rock sequence of the Kalgoorlie Terrane, Yilgarn Craton, Western Australia. The Sequence is divided into Lower and Upper Units separated by the Kambalda Komatiite Formation. Five basalt suites of the Lower Unit are tholeiitic where MgO spans 5-10 wt.% MgO, with minor assimilation-fractional crystallization (AFC), whereas six volcanic suites identified in the Upper Unit are tholeiitic to komatiitic-basalts with MgO 24-5 wt.% having generally greater degrees of AFC. Upper suites plot at Al₂O₃/TiO₂ (17-26) close to the primitive mantle ratio of 21, and Pt + Pd (19-31 ppb), whereas the PGE-depleted Lower basalts plot at generally lower Al₂O₃/TiO₂ (<16) and Pt + Pd (<10 ppb). Most suites have an average Pt/Pd ratio of 1.11, despite large variations in MgO contents, broadly consistent with the Pt/Pd ratio in the primitive mantle. On primitive mantle-normalised PGE plots, Upper suites generally display less fractionated patterns of the IPGE (Os, Ir, Ru and Rh) from the PPGE (Pt and Pd) relative to the Lower basalts. Most suites exhibit patterns with positive slopes reflecting relative enrichment of Pd, Pt, Au and Cu relative to Ni and IPGE. In suites of both Units, the concentrations of Ir and Ru fall with decreasing MgO contents, indicating their broadly compatible behaviour during magmatic evolution that involved AFC. Platinum and Pd behave as incompatible elements in the high-MgO suites, whereas Pt and Pd behave compatibly during crystallisation of the Lower basalt magmas, an interpretation consistent with progressively higher Cu/Pt and Cu/Pd ratios at decreasing MgO contents, and with falling Pt/Ti, collectively due to sulphur saturation induced by AFC as recorded in an antivariance of Pd/Ir with Nb/Th, a monitor of AFC.Collectively, the data suggest that several of the Lower Basalt suites crystallised under sulphide-saturated conditions, whereas most of the Upper Basalt Sequences remained sulphur undersaturated during magmatic evolution. Alteration, and fractional crystallisation of silicate and oxide phases, can be ruled out as factors governing PGE distribution in these mafic-ultramafic suites. Instead, the data suggest that discrete PGE-bearing phase (s) fractionated from the magmas. Such phases could be platinum group minerals (PGM; e.g., laurite) and/or alloys, or discrete PGE-rich nuggets or sulphides.  相似文献   

Aeromagnetic data analysis using the 2D directional continuous wavelet transform (DCWT)     

Sid-Ali Ouadfeul  Mohamed Hamoudi  Leila Aliouane  Said Eladj 《Arabian Journal of Geosciences》2013,6(6):1669-1680

In this paper, we have analyzed the geomagnetic anomaly field reduced to the pole by the 2D directional continuous wavelet transform (DCWT). The objective is to identify geological contacts. The proposed idea has been applied firstly at a synthetic model, the obtained results showed the robustness of the proposed technique, after that the synthetic data has been noised; analysis shows that contacts identified by DCWT are affected by noise. To resolve this problem, we have proposed an algorithm to reduce the noise effect in the contacts model. Application on the real geomagnetic data of In Ouzzal area located in the West of Hoggar (Algeria) shows clearly the robustness of the proposed method. Comparison with the analytic signal solutions exhibits a difference between the two models of contacts. Our method gives results that are accurate with the structural geological map.  相似文献   

New paleomagnetic results from the northern margin of the Kohistan Island Arc     

Haider Zaman  Yo-ichiro Otofuji  Said Rahim Khan  Mirza Naseer Ahmad 《Arabian Journal of Geosciences》2013,6(4):1041-1054

Different phases of remanent magnetizations have been identified in the Cretaceous–Tertiary rocks collected from the northern margin of the Kohistan Island Arc, northern Pakistan. Among them, a magnetite-related component is recognized as the most useful one because of its relatively stable behaviour and widespread presence in the volcanics and red beds. Calculation of mean direction for this component reveal two visible groupings in terms of paleomagnetic directions (Yasin + Baris Group: D?=?341.6º, I?=?10.6º, α ₉₅?=?23.3 º, k?=?11.7, N?=?5; Sandhi Group: D?=?28.4º, I?=??27.4º, α ₉₅?=?32.5 º, k?=?8.96, N?=?4). The fold tests applied to both these groups are inconclusive, indicating a syn-folding to post-folding origin for this component. A set of inclinations from this study provide new insight into post-collision northward displacement of the Kohistan Arc with respect to its surrounding terranes. Reliability of the paleomagnetic declinations from this study is not fully guaranteed, but when compared with previously reported paleomagnetic directions, a systematic increase in counter-clockwise deflections towards west has been detected along this paleo-island arc. This trend of declinations is well matched with the extrusion model of Asia, where counter-clockwise rotation has been suggested for the tectonic terranes around Western Himalaya. Another important observation is a divergence in paleomagnetic declinations across the rivers, which may indicate the presence of faulted zones under the cover of flowing water. This aspect can be compared to recent geological interpretations that Kohistan may not have acted as a rigid block following its collision with India but may have been deformed through localized shears and faults.  相似文献   

Vegetation effects on soil moisture estimation from ERS-2 SAR images     

S. Said  M.K. Arora 《水文科学杂志》2013,58(3):517-534

  相似文献