Petrology and geochemistry of feldspathic impact‐melt breccia Abar al' Uj 012, the first lunar meteorite from Saudi Arabia

Abar al' Uj (AaU) 012 is a clast‐rich, vesicular impact‐melt (IM) breccia, composed of lithic and mineral clasts set in a very fine‐grained and well‐crystallized matrix. It is a typical feldspathic lunar meteorite, most likely originating from the lunar farside. Bulk composition (31.0 wt% Al₂O₃, 3.85 wt% FeO) is close to the mean of feldspathic lunar meteorites and Apollo FAN‐suite rocks. The low concentration of incompatible trace elements (0.39 ppm Th, 0.13 ppm U) reflects the absence of a significant KREEP component. Plagioclase is highly anorthitic with a mean of An_96.9Ab_3.0Or_0.1. Bulk rock Mg# is 63 and molar FeO/MnO is 76. The terrestrial age of the meteorite is 33.4 ± 5.2 kyr. AaU 012 contains a ~1.4 × 1.5 mm² exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias. Bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali‐suite rocks. The IM clast is mainly composed of clinopyroxenes, contains a significant amount of cristobalite (9.0 vol%), and has a microcrystalline mesostasis. Although the clast shows similarities in texture and modal mineral abundances with some Apollo pigeonite basalts, it has lower FeO and higher SiO₂ than any mare basalt. It also has higher FeO and lower Al₂O₃ than rocks from the FAN‐ or Mg‐suite. Its lower Mg# (59) compared to Mg‐suite rocks also excludes a relationship with these types of lunar material.     

An approach to model the mechanical behavior of transversely isotropic materials

The present work proposes an approach to adapt existing isotropic models to transversely isotropic materials. The main idea is to introduce equivalence relations between the real material and a fictitious isotropic one on which one can take all the advantages of the well‐established isotropic theory. Two applications of this approach are presented here: a failure criterion and a damage model that takes into account the load‐induced anisotropy. In both cases, theoretical predictions are in agreement with the experimental data. In the present paper, the developed approach is applied to sedimentary rock materials; nevertheless, it can be generalized to any material that exhibits transverse isotropy. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of hot dry summer tropical climate on forage intake and milk yield in Holstein–Friesian and indigenous zebu cows in Sudan

The effects of dry summer ambient temperature on some physiological and productive responses were studied in an exotic European breed (Holstein–Friesian) and a local zebu breed (Butana ecotype) of cattle in Sudan. Rectal temperature and respiration rate were positively correlated, and dry matter intake and milk yield were negatively correlated with variation in ambient temperature. However, significant adverse effects on high ambient temperature were only observed in the exotic breed.     

Contribution de la gravimétrie à l'étude de la structure du bassin de Tadla (Maroc) : Implications hydrogéologiques

This study is based on the analysis and the interpretation of the gravity data of the Tadla basin. Its purpose is to increase the knowledge of this basin structure. A residual anomaly map was first calculated from the Bouguer anomaly data witch are strongly affected by a regional gradient. The computed map provides information on the ground density variation but it does not bring enough of new elements. Data filtering allows us to emphasize the structures affecting the basin. We chose the horizontal gradient coupled to the upward continuation techniques that permit to highlight news structures and to give information on their dip. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the Tadla basin. To cite this article: A. Najine et al., C. R. Geoscience 338 (2006).     

Adsorptive removal of textile reactive dye using Posidonia oceanica (L.) fibrous biomass

The Mediterranean seagrass Posidonia oceanica (L.) leaf sheaths were used as low cost, available and renewable biological adsorbent for the removal of reactive textile dye from aqueous solutions. Batch experiments were carried out for sorption kinetics and isotherms. Operating variables studied were temperature, pH and chemical pre-treatment. Biosorption capacity seems to be enhanced by increasing the temperature. Maximum colour removal was observed at pH 5. Pre-treating fibres with H₃PO₄ and HNO₃ solutions increased the adsorption efficiency up to 80 %. Experimental sorption kinetic data were fitted to both Lagergren first-order and pseudo-second-order models and the data were found to follow first-order equation for raw fibres and pseudo-second-order for pre-treated ones. Equilibrium data were well represented by the Freundlich isotherm model for all tested adsorption systems. Besides, the thermodynamic study has showed that the dye adsorption phenomenon onto P. oceanica biomass was favourable, endothermic and spontaneous.     

An evaluation of aquifer vulnerability in two nitrate sensitive areas of Catalonia (NE Spain) based on electrical resistivity methods

The protection of groundwater has become one of the most important European environmental policies as evidenced by the Orders relating to the protection of water from contamination, Directive 2000/60/CE of the European Parliament and the European Union Council, and more concretely Directive 2006/118/118/CE, related to the protection of groundwater from pollution and degradation. Traditional methods for assessing vulnerability include soil surveys, drilling and analysis of lithology logs from wells with the objective of characterising the thickness, hydraulic properties and lateral extend of the protective layers. However, such studies can be labour-intensive and expensive. In addition, the parameters measured may have high spatial variability, which makes accurate characterization over large areas difficult. Fortunately, a numerical index of protection can be assigned from the longitudinal electrical conductance parameter derived from electrical resistivity surveys (VES, ERT or any other electrical or EM method). This can be more accurate and reliable than any other vulnerability index derived only from visual inspection or interpolated from sparse borehole data.     

Ash Shutbah: A possible impact structure in Saudi Arabia

We have investigated the Ash Shutbah circular structure in central Saudi Arabia (21°37′N 45°39′E) using satellite imagery, field mapping, thin‐section petrography, and X‐ray diffraction of collected samples. The approximately 2.1 km sized structure located in flat‐lying Jurassic Tuwaiq Mountain Limestone has been nearly peneplained by erosional processes. Satellite and structural data show a central area consisting of Dhruma Formation sandstones with steep bedding and tight folds plunging radially outward. Open folding occurs in displaced, younger Tuwaiq Mountain Limestone Formation blocks surrounding the central area, but is absent outside the circular structure. An approximately 60 cm thick, unique folded and disrupted orthoquartzitic sandstone marker bed occurring in the central area of the structure is found 140 m deeper in undisturbed escarpment outcrops located a few hundred meters west of the structure. With exception of a possible concave shatter cone found in the orthoquartzite of the central area, other diagnostic shock features are lacking. Some quartz‐rich sandstones from the central area show pervasive fracturing of quartz grains with common concussion fractures. This deformation was followed by an event of quartz dissolution and calcite precipitation consistent with local sea‐ or groundwater heating. The combination of central stratigraphic uplift of 140 m, concussion features in discolored sandstone, outward‐dipping concentric folds in the central area, deformation restricted to the rocks of the ring structure, a complex circular structure of 2.1 km diameter that appears broadly consistent with what one would expect from an impact structure in sedimentary targets, and a possible shatter cone all point to an impact origin of the Ash Shutbah structure. In fact, the Ash Shutbah structure appears to be a textbook example of an eroded, complex impact crater located in flat‐lying sedimentary rocks, where the undisturbed stratigraphic section can be studied in escarpment outcrops in the vicinity of the structure.     

Sediment yield variability in central Tunisia: a quantitative analysis of its controlling factors

Abstract

This paper refers to the quantification and prediction of the sedimentation rate of 26 hillside-dam reservoirs in Central Tunisia. The objectives of the study are to develop a simple and practical methodology to identify controlling factors of sedimentation, and to propose a regionalization from the study sites. Principal component analysis (PCA) and complementary multi-dimensional statistical methods are used to relate highly variable area-specific sediment yield to hydro-morphometric, lithological, geomorphological and anthropogenic characteristics of catchments. It appears that catchment area is not the main controlling factor of sedimentation in the studied area. The overall slope index, drainage network characteristics and runoff parameters are also important in characterizing sediment yield. Applied to the annual sedimentation rate series, PCA resulted in retaining the first three principal axes, explaining 65% of the total variance. Statistical methods showed that the overall slope index, the total drainage length, the compacity index and the runoff parameters are as important for the sedimentation quantification. This allowed a graphical clustering of the study zone into three distinct groups having similar behaviours: (i) watersheds characterized by high sediment transport rates and high runoff coefficients, (ii) basins distinguished by relatively low values of both flow discharge and sediment transport rates, and (iii) watersheds with an intermediate sediment yield, especially characterized by relatively high relief. In a second step, a multiple regression model including the four characteristic catchment properties was developed, presenting a valuable tool to predict area-specific sediment yield from catchments in central Tunisia. This model shows reasonable efficiency with an absolute prediction error of 81%.

Citation Ayadi, I., Abida, H., Djebbar, Y. & Mahjoub, M. R. (2010) Sediment yield variability in central Tunisia: a quantitative analysis of its controlling factors. Hydrol. Sci. J. 55(3), 446–458.     

Influence of methane concentration on the optical indices of Titan’s aerosols analogues

This work deals with the optical constant characterization of Titan aerosol analogues or “tholins” produced with the PAMPRE experimental setup and deposited as thin films onto a silicon substrate. Tholins were produced in different N₂–CH₄ gaseous mixtures to study the effect of the initial methane concentration on their optical constants. The real (n) and imaginary (k) parts of the complex refractive index were determined using the spectroscopic ellipsometry technique in the 370–1000 nm wavelength range. We found that optical constants depend strongly on the methane concentrations of the gas phase in which tholins are produced: imaginary optical index (k) decreases with initial CH₄ concentration from 2.3 × 10^?2 down to 2.7 × 10^?3 at 1000 nm wavelength, while the real optical index (n) increases from 1.48 up to 1.58 at 1000 nm wavelength. The larger absorption in the visible range of tholins produced at lower methane percentage is explained by an increase of the secondary and primary amines signature in the mid-IR absorption. Comparison with results of other tholins and data from Titan observations are presented. We found an agreement between our values obtained with 10% methane concentration, and Imanaka et al. (Imanaka, H., Khare, B.N., Elsila, J.E., Bakes, E.L.O., McKay, C.P., Cruikshank, D.P., Sugita, S., Matsui, T., Zare, R.N. [2004]. Icarus, 168, 344–366) values, in spite of the difference in the analytical method. This confirms a reliability of the optical properties of tholins prepared with various setups but with similar plasma conditions. Our comparison with Titan’s observations also raises a possible inconsistency between the mid-IR aerosol signature by VIMS and CIRS Cassini instruments and the visible Huygens-DISR derived data. The mid-IR VIMS and CIRS signatures are in agreement with an aerosol dominated by an aliphatic carbon content, whereas the important visible absorption derived from the DISR measurement seems to be incompatible with such an important aliphatic content, but more compatible with an amine-rich aerosol.