Cementation of kerogen-rich marls by alkaline fluids released during weathering of thermally metamorphosed marly sediments. Part II: Organic matter evolution,magnetic susceptibility and metals (Ti,Cr, Fe) at the Khushaym Matruk natural analogue (Central Jordan)

Spontaneous combustion, less than 1 Ma ago, affected a 60-m thick sediment pile of biomicrite at the Khushaym Matruck site (Jordan). The present study shows that three retrograde alteration stages occurred: weathering, thermal stress and oxidative alkaline perturbation. μ-FT-i.r. spectra of isolated kerogens and oxygen index of whole rocks indicate that oxidation of organic matter occurred down to ∼10 m beneath the metamorphosed zone at Khushaym Matruck. The occurrence of the oxidative weathering bacterially mediated, as suggested by the mass chromatograms of saturated hydrocarbons, can explain high Rock-Eval T_max values and low petroliferous potential measured along the sedimentary pile. On the other hand, the thermal extent of combustion events was limited to the first 2 m from the contact. The mean reflectance of 0.20–0.24% and porosity of ca. 50% of the grey clayey biomicrites indicate that organic matter was very immature and sediments were unconsolidated at the time of the combustion event. Using mineralogy, microscopic analyses of vegetable debris and magnetic susceptibility, a suite of characteristic points corresponding to the thermal imprint can be assessed: (i) x = 0m, T ∼ 1000 °C, (ii) x = 1 m, T ∼ 350 °C, (iii) x = 2 m, T ∼ 150 °C and (iv) x > ∼ 8 m, T ∼ 30 °C. Paleocirculation of meteoric groundwater in the ‘cement-marbles’ generated high-pH fluids that have circulated via fractures and through the matrix porosity of the underlying biomicrites but have also induced alkaline hydrolysis and oxidative attack of the organic matter. The polysaccharide/lignin ratio derived from μ-FT-i.r. analyses shows that the delignification of vegetable debris and degradation of polysaccharides progressively decline in the indurated zone, which indicates a decrease in the pH of migrating solutions. The latter also severely oxidized organic matter at 2.10 and 3.05 m as revealed by the oxygen index and induced the generation of bitumen. The spatial correlation between the oxidation levels of organic matter and the metal contents (Fe, Ti and Cr) suggests that redox reactions were responsible for the immobilization of metals in the indurated biomicrites. The intensity of these reactions is attributed to changes in the fluid flow regime within the sedimentary column.     

Simulation of vortex-induced vibrations of a cylinder using ANSYS CFX

In this paper, vortex-induced vibrations of a cylinder are simulated by use of ANSYS CFX simulation code. The cylinder is treated as a rigid body and transverse displacements are obtained by use of a one degree of freedom spring damper system. 2-D as well as 3-D analysis is performed using air as the fluid. Reynolds number is varied from 40 to 16000 approx., covering the laminar and turbulent regimes of flow. The experimental results of （Khalak and Williamson, 1997） and other researchers are used for validation purposes. The results obtained are comparable.     

Prediction of long-term settlement on soft clay using shear wave velocity and damping characteristics

This paper presents a method of calculating long-term settlement of a loaded pad on soft clay at Klang, Selangor, Malaysia where the soil model is treated as an anelastic material of viscoelastic property. Initially, an elastic shear modulus (G) value from shear wave velocity profiles of the seismic tests from spectral analysis of surface wave (SASW) and continuous surface wave (CSW) tests was obtained. A value of damping (D) at an equivalent elastic strain is then calculated from the hysteresis of the plate load tests corrected to equivalent strain using the Damping–Strain formula. The calculated elastic settlement and its equivalent damping are then used to calculate the long-term settlement by applying the generalised viscoelastic formula. Comparisons to traditional methods of settlement predictions were made and the viscoelastic formula has shown better agreement to the observed settlement. Further modification of the settlement formula is introduced to improve the settlement accuracy to 10%.     

Geochemistry and fluid inclusions study of highly fractionated garnet-bearing granite of Gabal Abu Diab, central Eastern Desert of Egypt

The Neoproterozoic granite of Gabal Abu Diab, central Eastern Desert of Egypt, comprises mainly garnet-bearing granite and alkali feldspar granite intruded into calc-alkaline granodiorite–tonalite and metagabbro–diorite complexes. The garnet-bearing granite is composed mainly of plagioclase, K-feldspar, quartz, garnet and primary muscovite ± biotite. The presence of garnet and primary muscovite of Abu-Diab granite suggests its highly fractionated character. Geochemically, the garnet-bearing granite is highly fractionated as indicated from the high contents of SiO₂ (74.85–77.5%), alkalis (8.27 to 9.2%, Na₂O+K₂O) and the trace elements association: Ga, Zn, Zr, Nb and Y. This granite is depleted in CaO, MgO, P₂O₅, Sr and Ba. The alumina saturation (Shand Index, molar ratio A/CNK) of 1.0 to 1.1 indicates the weak peraluminous nature of this garnet-bearing granite. The geochemical characteristics of the Abu Diab garnet-bearing granite are consistent with either the average I-type or A-type granite and also suggest post-orogenic or anorogenic setting. A fluid inclusions study reveals the presence of three fluid generations trapped into the studied granite. The earlier is a complex CO₂–H₂O fluid trapped in primary fluid inclusions with CO₂ contents >?60 vol.%. These inclusions were probably trapped at minimum temperature >?400°C and minimum pressure >?2 kb. The second is immiscible water–CO₂ fluid trapped in secondary and/or pseudo-secondary inclusions. The trapping conditions were estimated at temperature between 400°C and 170°C and pressure between 900 and 2000 bar. The latest fluid is low-salinity aqueous fluid trapped in secondary two-phase and mono-phase inclusions. The trapping conditions were estimated at temperature between 90°C and 160°C and pressure <?900 bar. The origin of the early fluid generation is magmatic fluid while the second and third fluids are of hydrothermal and meteoric origin, respectively.     

On the cratonization of the Arabian-Nubian Shield:Constraints from gneissic granitoids in south Eastern Desert,Egypt

The Shaitian granite complex(SGC) spans more than 80 Ma of crustal growth in the Arabian–Nubian Shield in southeast Egypt.It is a voluminous composite intrusion(60 km~2) comprising a host tonalite massif intruded by subordinate dyke-like masses of trondhjemite,granodiorite and monzogranite.The host tonalite,in turn,encloses several,fine-grained amphibolite enclaves.U-Pb zircon dating indicates a wide range of crystallization ages within the SGC(800 ± 18 Ma for tonalites;754 ± 3.9 Ma for trondhjemite;738 ± 3.8 Ma for granodiorite;and 717 ± 3.2 Ma for monzogranite),suggesting crystallization of independent magma pulses.The high positiveεNdi(+6–+8) indicate that the melting sources were dominated by juvenile material without any significant input from older crust.Application of zircon saturation geothermometry indicates increasing temperatures during the generation of melts from 745 ± 31 ℃ for tonalite to 810 ± 25 ℃ for trondhjemite;840 ± 10 ℃ for granodiorite;and 868 ± 10 ℃ for monzogranite.The pressure of partial melting is loosely constrained to be below the stability of residual garnet(10 kbar) as inferred from the almost flat HREE pattern((Gd/Lu)N= 0.9–1.1),but 3 kbar for the stability of residual amphibole as inferred from the significantly lower NbNand TaNcompared with LREENand the sub-chondrite Nb/Ta ratios exhibited by the granitic phases.The inverse relation between the generation temperatures and the ages estimates of the granitoid lithologies argue against a significant role of fractional crystallization.The major and trace element contents indicate the emplacement of the SGC within a subduction zone setting.It lacks distinctive features for melt derived from a subducted slab(e.g.high Sr/Y and high(La/Yb)Nratios),and the relatively low MgO and Ni contents in all granite phases within the SGC suggest melting within the lower crust of an island arc overlying a mantle wedge.Comparison with melts produced during melting experiments indicates an amphibolite of basaltic composition is the best candidate as source for the tonalite,trondhjemite and granodiorite magmas whereas the monzogranite magma is most consistent with fusion of a tonalite protolith.Given the overlapping Sm-Nd isotope ratios as well as several trace element ratios between monzogranite and tonalite samples,it is reasonable to suggest that the renewed basaltic underplating may have caused partial melting of tonalite and the emplacement of monzogranite melt within the SGC.The emplacement of potassic granite(monzogranite) melts subsequent to the emplacement of Na-rich granites(tonalitetrondhjemite-granodiorite) most likely suggests major crustal thickening prior arc collision and amalgamation into the over thickened proto-crust of the Arabian-Nubian shield.Eventually,after complete consolidation,the whole SGC was subjected to regional deformation,most probably during accretion to the Saharan Metacraton(arc–continent collisions) in the late Cryogenian-Ediacaran times(650–542 Ma).     

Apatite-rich pyrometamorphic rocks from Suweileh area,Jordan

Representative samples from the upper Cretaceous pyrometamorphic rocks from Suweileh area were investigated by using XRD, XRF, SEM/EDS, and microprobe techniques. Suweileh area is characterized by the presence of varicolored marble (dominated by green apatite-rich rocks) overlying bituminous marl and silicified limestone-phosphorite beds. The bituminous rocks are enriched with P, S, and F in addition to reduced sensitive trace elements that were inherited later by their metamorphic equivalents. The rocks were affected by severe tectonism that produced intensive fracturing which facilitated the chemical leaching. The mineralogy of the varicolored marble from Suweileh area is equivalent to Daba-Siwaqa and Maqarin areas in central and north Jordan. High-temperature and low-temperature groups of minerals were recognized. The first group is the result of pyrometamorphism produced from the spontaneous combustion of bituminous marl. The metamorphism was contemporaneous with tectonism of the Rift Valley. The second secondary group of minerals is the result of alteration by high alkaline waters followed by precipitation along the weakness zones. A hyperalkaline circulating water similar to the current issuing waters from Maqarin (north Jordan) was responsible for leaching and precipitation of anions and trace elements. A similar scenario was reported in north and central Jordan. The calculated structural formula of fluorapatite is Ca_5.02 (P_2.325, Si_0.22, S_0.0833) O₁₂ F_0.975. The apatite structure incorporates S and Si (inherited from the bituminous precursor) that substitute for P in the tetrahedral positions.     

Generation of stochastic earthquake ground motion in western Saudi Arabia as a first step in development of regional ground motion prediction model

Earthquake ground motion model is an essential part of seismic hazard assessment. The model consists in several empirical ground motion prediction equations (GMPEs) that are considered to be applicable to the given region. When the recorded ground motion data are scarce, numerical modeling of ground motion based on available seismological information is widely used. We describe results of stochastic simulation of ground motion acceleration records for western Saudi Arabia. The simulation was performed using the finite fault model and considering peak ground acceleration and amplitudes of spectral acceleration at natural frequencies 0.2 and 1.0 s. Based on the parameters of the input seismological model that were accepted in similar previous studies, we analyze influence of variations in the source factor (stress drop) and in the local attenuation and amplification factors (kappa value, crustal amplification). These characteristics of the model are considered as the major contributors to the ground motion variability. The results of our work show that distribution of simulated ground motion parameters versus magnitude and distance reveals an agreement with the GMPEs recently used in seismic hazard assessment for the region. Collection of credible information about seismic source, propagation path, and site attenuation parameters using the regional ground motion database would allow constraining the seismological model and developing regional GMPEs. The stochastic simulation based on regional seismological model may be applied for generation of ground motion time histories used for development of analytical fragility curves for typical constructions in the region.     

Amelioration of calcareous sandy soil productivity via incorporation between biochar and some organic manures

Most arid and semi-arid soils, especially calcareous sandy soils, are widely distributed in the Middle East region; the deficiency in their content of many nutrients particularly phosphorus and organic matter limits crops production. This study aimed to assess the effects of adding biochar (B) with farmyard manure (FYM) and poultry manure (PM) on some soil properties, phosphorus (P) availability, and barley growth in calcareous sandy soil. The pot experiment includes the following treatments: Control, B, B?+?FYM (1:1), B?+?PM (1:1), B?+?FYM (2:1), B?+?PM (2:1), FYM?+?B (2:1), and PM?+?B (2:1). Biochar combined with FYM and PM enhanced the water holding capacity (WHC) and soil organic matter (SOM) content in calcareous sandy soil. Phosphorus availability was increased significantly by applying biochar mixed with farmyard manure and poultry manure at all treatments. Green biomass of barley improved because of adding biochar alone, poultry manure alone, and biochar co-applied with poultry manure at all mixing ratios. Biochar application caused significant increases in phosphorus use efficiency (PUE) by barley plants compared to all other treatments, except for the control. We recommend adding biochar either individually or mixed with poultry manure to improve the productivity of calcareous sandy soil.     

Groundwater and surface-water utilisation using a bank infiltration technique in Malaysia

Bank infiltration (BI) is one of the solutions to providing raw water for public supply in tropical countries. This study in Malaysia explores the use of BI to supplement a polluted surface-water resource with groundwater. Three major factors were investigated: (1) contribution of surface water through BI to the resulting abstraction, (2) input of local groundwater, and (3) water-quality characteristics of the resulting water supply. A geophysical method was employed to define the subsurface geology and hydrogeology, and isotope techniques were performed to identify the source of groundwater recharge and the interaction between surface water and groundwater. The physicochemical and microbiological parameters of the local surface-water bodies and groundwater were analyzed before and during water abstraction. Extracted water revealed a 5–98 % decrease in turbidity, as well as reductions in HCO₃ ^?, Cl^?, SO₄ ^2?, NO₃ ^?, Ca²⁺, Al³⁺ and As concentrations compared with those of Langat River water. In addition, amounts of E. coli, total coliform and Giardia were significantly reduced (99.9 %). However, water samples from test wells during pumping showed high concentrations of Fe²⁺ and Mn²⁺. Pumping test results indicate that the two wells used in the study were able to sustain yields.