Multi-scale analysis of water alteration on the rockslope stability framework

Water is an important weathering factor on rock discontinuities and in rock mass mechanical behaviour because of its chemical features such as temperature, pH or salinity which make it a “good” candidate to rock degradation. Furthermore the increase of rainfall frequency or intensity highlights some problems on the rock slope stability analysis. This study aims to evaluate the effect of water flow on the rock slope stability and it is performed at two space scales: in situ scale and laboratory (micro scale and macro scale). It shows how water induces degradation at multi-scale (surface roughness and matrix) and thus may decrease the stability of the discontinuous rock mass. It has two main components: the effect of water-solid chemical mechanisms and the analysis of the mechanical response of the discontinuity modified by the water alteration.     

Supra-subduction affinity in the Neoproterozoic serpentinites in the Eastern Desert, Egypt: Evidence from mineral composition

Serpentinites in the Eastern Desert (ED) of Egypt represent integral components of the ophiolites. Metamorphic textures of the serpentinites preserve the complex mineralogical evolution from primary peridotite through metamorphism, and late-stage hydrothermal alteration. Two textural types are distinguished in the olivines of the present serpentinized peridotites, namely (a) highly-strained olivine grains with kink bands, as in the deformed mantle tectonites from ophiolites, and (b) non-strained grains. The latter may represent recrystallized crystals during later thermal metamorphic events due to the intrusion of granite. On the basis of X-ray diffraction analysis, antigorite is the main serpentine minerals with lesser chrysotile and lizardite which indicates that serpentinites were formed under prograde metamorphism. Relict primary minerals of the serpentinites are Cr-spinel, olivine and pyroxene. Chrome spinel relicts have high Cr# (0.60–0.80), whereas primary olivines are Mg-rich nature (Fo = 89–96). Geochemical compositions of serpentinites indicate that they formed not at mid-ocean ridges but at spreading centers associated with subduction zones and this could have happened in a supra-subduction zone either in the fore-arc or back-arc environments. Mineral compositions of primary chrome spinels and olivines are similar to those of modern fore-arcs. High Cr# in the relict chrome spinels and Fo in the primary olivines of serpentinites indicate that they are residual after extensive partial melting and originated by sea-floor spreading during subduction initiation.     

Geochemistry and environmental impacts of retorted oil shale from Jordan

Physical and chemical characterization of spent oil shale (OS) from El-Lajjun area has been carried out and compared with the original OS. The spent shale (SS) is subjected to leaching tests to detect the possibilities of heavy metals released from it into the environment. Standard column leaching experiments have revealed no detectable release of heavy metals to the percolating water. The effectiveness of the SS in removing Pb²⁺ from wastewater has been investigated. The SS is very efficient in removing most of Pb²⁺ where 1 m³ of SS has an efficiency to remove from 64 to 94% of Pb²⁺ from about 1,300 m³ wastewater sample containing 50 ppm Pb²⁺. The efficiency decreases substantially with increasing Pb²⁺ concentration in the wastewater. In real situations, where Pb²⁺ concentration is very low (i.e., less than 5 ppm), the efficiency of the SS is expected to be 100%.     

Marble-hosted sulfide ores in the Angouran Zn-(Pb–Ag) deposit, NW Iran: interaction of sedimentary brines with a metamorphic core complex

The Angouran Zn-(Pb–Ag) deposit, Zanjan Province, NW Iran, is located within the central Sanandaj-Sirjan Zone of the Zagros orogenic belt. The deposit has proven and estimated resources of 4.7 Mt of sulfide ore at 27.7% Zn, 2.4% Pb, and 110 g/t Ag, and 14.6 Mt of oxidized carbonate ores at 22% Zn and 4.6% Pb. It is hosted by a metamorphic core complex that is unconformably overlain by a Neogene volcanic and evaporite-bearing marine to continental sedimentary sequence. The sulfide orebody, precursor to the significant nonsulfide ores, is located at the crest of an open anticline at the contact between Neoproterozoic to Cambrian footwall micaschists and hanging wall marbles. ⁴⁰Ar–³⁹Ar data on muscovite from mineralized and unaltered footwall micaschists suggest a rapid Mid-Miocene exhumation of the metamorphic basement (∼20 Ma) and yield an upper age constraint for mineralization. The fine-grained sulfide ore is massive, replacive, often brecciated, clearly postmetamorphic and dominated by Fe-poor sphalerite, with minor galena, pyrite, anhydrite, quartz, muscovite, dolomite, and rare calcite. Sphalerite contains Na–Ca–Cl brine inclusions (23–25 mass% total dissolved solids) with homogenization temperatures of 180–70°C. Fluid inclusion chemistry (Na–K–Li–Ca–Mg–Cl–Br), ore geochemistry, S, and Pb isotope data suggest that the Angouran sulfide ore formed by the interaction of modified, strongly evaporated Miocene seawater and the lithotypes of an exhumed metamorphic core complex. Minor contributions of metals from Miocene igneous rocks cannot be excluded. Mineralization occurred in a collisional intra-arc setting with high heat flow, probably during the transition from an extensional to a compressional regime. The Angouran deposit may represent a new type of low-temperature carbonate-hosted Zn–Pb ore that is distinct from Mississippi Valley type and sedimentary-exhalative deposits.Editorial handling: B. Lehmann     

Die elektrochemische Bestimmung des im Wasser gelösten Sauerstoffs mit Hilfe einer modifizierten Membranelektrodentechnik

Zusammenfassung Die Anwendungsm?glichkeiten der elektrochemischen Sauerstoffbestimmung wurden durch die Einführung der Kurzzeitmessung erweitert. Diese Methode gibt eine gr?ssere Empfindlichkeit und erlaubt somit die Sauerstoffbestimmung im μg/l-Bereich. Ferner wurde ein System entwickelt, das von der Membrandicke und dem Membranmaterial unabh?ngig ist. Das ist ein Vorteil, der speziell für Sauerstoffmessungen in Kl?ranlagen interessant sein dürfte.

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Summary This paper presents a new electrochemical technique for DO measurements by means of membrane electrodes. In stead of the well-known steady state measurements, a transient technique which is more sensitive was used. This gives the possibility of measuring oxygen in the μl/l range. The system is independent of the membrane material and the membrane thickness. The stirring influence is considerably less than for steady state measurements. The independence of the membrane material will be especially useful for oxygen measurements in waste purification plants.

     

Plant remains from the Tharumsa Formation of Ladakh,India

Plant remains, including both mega and micro collected from the middle part of the Tharumsa Foramtion (early Miocene) are described for the first time from the Tharumsa village of the Kargil district, Jammu and Kashmir to reconstruct the palaeoenvironment. They indicate their affinities with Broussonetia of the Moraceae and Abies, Cedrus and Pinus of the Pinaceae. Their presence indicates warm and moist tropical to sub-tropical climate in the Kargil area during the depositional period against the cold and dry climate prevailing at present.     

Quantifying changes in groundwater level and chemistry in Shahrood,northeastern Iran

Temporal changes in the quantity and chemical status of groundwater resources must be accurately quantified to aid sustainable management of aquifers. Monitoring data show that the groundwater level in Shahrood alluvial aquifer, northeastern Iran, continuously declined from 1993 to 2009, falling 11.4 m in 16 years. This constitutes a loss of 216 million m³ from the aquifer’s stored groundwater reserve. Overexploitation and reduction in rainfall intensified the declining trend. In contrast, the reduced abstraction rate, the result of reduced borehole productivity (related to the reduction in saturated-zone thickness over time), slowed down the declining trend. Groundwater salinity varied substantially showing a minor rising trend. For the same 16-year period, increases were recorded in the order of 24% for electrical conductivity, 12.4% for major ions, and 9.9% for pH. This research shows that the groundwater-level declining trend was not interrupted by fluctuation in rainfall and it does not necessarily lead to water-quality deterioration. Water-level drop is greater near the aquifer’s recharging boundary, while greater rates of salinity rise occur around the end of groundwater flow lines. Also, fresher groundwater experiences a greater rate of salinity increase. These findings are of significance for predicting the groundwater level and salinity of exhausted aquifers.     

A literature review of Algerian salt lakes: values,threats and implications

Chotts are salt lakes located in the arid regions of Northern Africa. These unique wetlands are recognized for their role in the migration and breeding of waterbirds and economic values generated from mineral extraction, agriculture and tourist activities. Despite their importance for flora and fauna biodiversity, they continue to face important threats due to human activities. This article consolidates a literature review of Algerian chotts from global to local importance. An in-depth view demonstrates the changes in land use of two large chotts in the southeastern region of Algeria: Chotts Merouane and Melghir. Land use images highlight a net expansion of agricultural lands, a decrease in grazing area around the lakes and a decrease of salt lake surface area. The local focus highlights the threats and changes of Algerian and Northern African chotts and proposes some perspectives for the future.     

<Emphasis Type="Italic">Salpingoporella</Emphasis> (dasycladalean algae) species from the Lower Cretaceous carbonate facies of Kopet Dagh basin (NE Iran)

Salpingoporella species from algal bearing of Barremian-Aptian limestones in the Kopet Dagh basin (NE of Iran) are described. Different species (S. cemi, S. hasi, S. heraldica, S. hispanica, S. milovanovici, S. muehlmbergi, S. parapiriniae, S. piriniae, S. cf. biokovensis, S. steinhauseri, S. polygonalis) are investigated from different biometrical aspects such as depositional environments and biogeographical distribution as well as their systematic palaeontology from two formations (the Tirgan and Sarcheshmeh formations) in nine stratigraphic sections.     

A numerical model study of the structure and similarity scaling of the nocturnal boundary layer (NBL)

A one-dimensional numerical model based on the equations of mean motion and turbulent kinetic energy (TKE), with Delage's (1974) mixing-length parameterization has been used to simulate the mean and turbulent structure of the evolving stably stratified nocturnal boundary layer (NBL). The model also includes a predictive equation for the surface temperature and longwave radiational cooling effects.In the absence of advective and gravity wave effects, it is found that the model-simulated structure, after a few hours of evolution, could be ordered fairly well by a similarity scaling (u _*0, _*0, L ₀, and h) based on surface fluxes and the NBL height. Simple expressions are suggested to describe the normalized profiles of momentum and heat fluxes, TKE, eddy-viscosity and energy dissipation. A good ordering of the same variables is also achieved by a local scaling (u _*0, _* and L) based on the height-dependent local fluxes. The normalized TKE, eddy viscosity and energy dissipation are unique functions of z/L and approach constant values as z/L , where L is the local Monin-Obukhov length. These constants are close to the values predicted for the surface layer as z/L , thus suggesting that the Monin-Obukhov similarity theory can be extended to the whole NBL, by using the local (height-dependent) scales in place of surface-layer scales. The observed NBL structure has been shown to follow local similarity (Nieuwstadt, 1984).