Climate change scenarios for precipitation and potential evapotranspiration over central Belgium

In this article, we examine climate model estimations for the future climate over central Belgium. Our analysis is focused mainly on two variables: potential evapotranspiration (PET) and precipitation. PET is calculated using the Penman equation with parameters appropriately calibrated for Belgium, based on RCM data from the European project PRUDENCE database. Next, we proceed into estimating the model capacity to reproduce the reference climate for PET and precipitation. The same analysis for precipitation is also performed based on GCM data from the IPCC AR4 database. Then, the climate change signal is evaluated over central Belgium using RCM and GCM simulations based on several SRES scenarios. The RCM simulations show a clear shift in the precipitation pattern with an increase during winter and a decrease during summer. However, the inclusion of another set of SRES scenarios from the GCM simulations leads to a less clear climate change signal.     

Nodal and Mixed Finite Elements for the Numerical Homogenization of 3D Permeability

The aim of upscaling is to determine equivalent homogeneous parameters at a coarse-scale from a spatially oscillating fine-scale parameter distribution. To be able to use a limited number of relatively large grid-blocks in numerical oil reservoir simulators or groundwater models, upscaling of the permeability is frequently applied. The spatial fine-scale permeability distribution is generally obtained from geological and geostatistical models. After upscaling, the coarse-scale permeabilities are incorporated in the relatively large grid-blocks of the numerical model. If the porous rock may be approximated as a periodic medium, upscaling can be performed by the method of homogenization. In this paper the homogenization is performed numerically, which gives rise to an approximation error. The complementarity between two different numerical methods – the conformal-nodal finite element method and the mixed-hybrid finite element method – has been used to quantify this error. These two methods yield respectively upper and lower bounds for the eigenvalues of the coarse-scale permeability tensor. Results of 3D numerical experiments are shown, both for the far field and around wells.     

Linking hydrological, infinite slope stability and land-use change models through GIS for assessing the impact of deforestation on slope stability in high Andean watersheds

In the Ecuadorian Andes, episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common. Consequently, not only considerable financial costs are experienced, but also major ecological and environmental problems arise in a larger geographical area. Sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels. In developing countries world-wide, slope movement hazards are growing: increasing population pressure and economic development force more people to move to potentially hazardous areas, which are less suitable for agriculture and rangelands.This paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process-based slope stability model, which includes a dynamic soil wetness index using a simple subsurface flow model. The model provides a time-varying estimate of slope movement susceptibility, by linking land-use data with spatially varying hydrologic (soil conductivity, evapotranspiration, soil wetness) and soil strength properties. The slope stability model was applied to a high Andean watershed (Gordeleg Catchment, 250 ha, southern Ecuadorian Andes) and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements, as measured in the field with GPS. The proposed methodology allows assessment of the effects of past and future land-use change on slope stability. A realistic deforestation scenario was presented: past land-use change includes a gradual fragmentation and clear cut of the secondary forests, as observed over the last four decades (1963–2000), future land-use change is simulated based on a binary logistic deforestation model, whereby it was assumed that future land-use change would continue at the same rate and style as over the last 37 years (1963–2000).     

Numerical Homogenization of the Rigidity Tensor in Hooke''s Law Using the Node-Based Finite Element Method

Combining a geological model with a geomechanical model, it generally turns out that the geomechanical model is built from units that are at least a 100 times larger in volume than the units of the geological model. To counter this mismatch in scales, the geological data model's heterogeneous fine-scale Young's moduli and Poisson's ratios have to be upscaled to one equivalent homogeneous coarse-scale rigidity. This coarse-scale rigidity relates the volume-averaged displacement, strain, stress, and energy to each other, in such a way that the equilibrium equation, Hooke's law, and the energy equation preserve their fine-scale form on the coarse scale. Under the simplifying assumption of spatial periodicity of the heterogeneous fine-scale rigidity, homogenization theory can be applied. However, even then the spatial variability is generally so complex that exact solutions cannot be found. Therefore, numerical approximation methods have to be applied. Here the node-based finite element method for the displacement as primary variable has been used. Three numerical examples showing the upper bound character of this finite element method are presented.     

Processes of normal fault evolution in a siliciclastic sequence: a case study from Miri, Sarawak, Malaysia

Detailed field observations of normal faults formed at shallow depth in a deltaic sand–clay sequence near Miri, Sarawak are used to study the main structural elements during the early stages of fault development. We studied over 450 segmented faults, many of which contain clay smear, in an excellent outcrop exposing a collapsed crest structure.In agreement with previous studies we find that important elements of fault zone evolution are: (i) clay smear, (ii) telescoping on parallel strands, and (iii) preferred deformation of fault-bounded lenses. We model the consequences of telescoping on parallel strands and conclude that the reliability of juxtaposition diagrams can decrease dramatically in the presence of undetected multiple fault strands. The across fault connectivity can either increase or decrease depending on small variations in many of the input parameters.All the faults studied have a continuous clay smear over the interval studied, except for the places where a sand bed has an offset smaller than its thickness, and therefore has not moved past clay. Although on average the clay content observed correlates well with the average clay content of the faulted section, there are large variations in clay content controlled by local complexity in deformation. Understanding of this local complexity is a prerequisite for further improvement of clay smear in the subsurface.     

Origin and evolution of high-salinity, Zn–Pb mineralising fluids in the Variscides of Belgium

High-salinity, Na–Ca–Cl-rich fluids (˜20 wt% salts) in inclusions in gangue and ore minerals from Mesozoic Mississippi Valley-type (MVT) deposits in the Verviers Synclinorium (eastern Belgium) and in Cretaceous vein calcites at the Variscan front were investigated by microthermometric and crush-leach analysis. The MVT deposits formed at temperatures of ˜110 °C while the Cretaceous vein calcites were precipitated at temperatures <50 °C. Their Cl–Br content (Cl/Br ratio between 246 and 458) suggests that the fluids probably originated by the evaporation of seawater during basin development at the southern margin of the Caledonian Brabant Massif in the Late Palaeozoic. The Na–Ca–K content (Na: 29,700–49,600 ppm, Ca: 25,700–46,200 ppm, K: 1,000–5,620 ppm) is similar to that of the mineralising fluids in other Pb–Zn districts, interpreted to be of evaporative origin (e.g. Newfoundland, East Tennessee, Polaris). Furthermore, comparison of the Na–Ca–K content of the fluids with that of an evolved evaporitic brine enables the recognition of major water–rock interactions that modified the fluid composition. It indicates that the ambient fluids participated in the early diagenetic dolomitisation of Upper Palaeozoic carbonates and also in the albitisation of plagioclase in Lower Palaeozoic siliciclastics of the Caledonian basement. Illitisation of smectites or dissolution of K-feldspar probably controlled the K-content of the fluids. A model is proposed where the bittern brines migrated down into the deep subsurface because of their density during extension. After the Variscan orogeny, these fluids were finally expelled along extensional faults, resulting in the formation of Zn–Pb deposits. Received: 26 April 2000 / Accepted: 22 November 2000     

Metamorphic fluid flow in the northeastern part of the 3.8-3.7 Ga Isua Greenstone Belt (SW Greenland): A re-evalution of fluid inclusion evidence for early Archean seafloor-hydrothermal systems

Fluid inclusions in quartz globules and quartz veins of a 3.8-3.7 Ga old, well-preserved pillow lava breccia in the northeastern Isua Greenstone Belt (IGB) were studied using microthermometry, Raman spectrometry and SEM Cathodoluminescence Imaging. Petrographic study of the different quartz segregations showed that they were affected by variable recrystallization which controlled their fluid inclusion content. The oldest unaltered fluid inclusions found are present in vein crystals that survived dynamic and static recrystallization. These crystals contain a cogenetic, immiscible assemblage of CO₂-rich (+H₂O, +graphite) and brine-rich (+CO₂, +halite, +carbonate) inclusions. The gas-rich inclusions have molar volumes between 44.8 and 47.5 cm³/mol, while the brine inclusions have a salinity of ∼33 eq. wt% NaCl. Modeling equilibrium immiscibility using volumetric and compositional properties of the endmember fluids indicates that fluid unmixing occurred at or near peak-metamorphic conditions of ∼460 °C and ∼4 kbar. Carbonate and graphite were precipitated cogenetically from the physically separated endmember fluids and were trapped in fluid inclusions.In most quartz crystals, however, recrystallization obliterated such early fluid inclusion assemblages and left graphite and carbonate as solid inclusions in recrystallized grains. Intragranular fluid inclusion trails in the recrystallized grains of breccia cementing and crosscutting quartz veins have CO₂-rich assemblages, with distinctly different molar volumes (either between 43.7 and 47.5 cm³/mol or between 53.5 and 74.1 cm³/mol), and immiscible, halite-saturated H₂O-CO₂-NaCl(-other salt) inclusions. Later intergranular trails have CH₄-H₂ (X_H2 up to ∼0.3) inclusions of variable density (ranging from 48.0 to >105.3 cm³/mol) and metastable H₂O-NaCl(-other salt?) brines (∼28 eq. wt% NaCl). Finally, the youngest fluid inclusion assemblages are found in non-luminescent secondary quartz and contain low-density CH₄ (molar volume > 105.33 cm³/mol) and low-salinity H₂O-NaCl (0.2-3.7 eq. wt% NaCl). These successive fluid inclusion assemblages record a retrograde P-T evolution close to a geothermal gradient of ∼30 °C/km, but also indicate fluid pressure variations and the introduction of highly reducing fluids at ∼200-300 °C and 0.5-2 kbar. The quartz globules in the pillow fragments only contain sporadic CH₄(+H₂) and brine inclusions, corresponding with the late generations present in the cementing and crosscutting veins. We argue that due to the large extent of static recrystallization in quartz globules in the pillow breccia fragments, only these relatively late fluid inclusions have been preserved, and that they do not represent remnants of an early, seafloor-hydrothermal system as was previously proposed.Modeling the oxidation state of the fluids indicates a rock buffered system at peak-metamorphic conditions, but suggests a change towards fluid-graphite disequilibrium and a logf_H2/f_H2O above the Quartz-Fayalite-Magnetite buffer during retrograde evolution. Most likely, this indicates a control on redox conditions and on fluid speciation by ultramafic rocks in the IGB.Finally, this study shows that microscopic solid graphite in recrystallized metamorphic rocks from Isua can be deposited inorganically from a fluid phase, adding to the complexity of processes that formed reduced carbon in the oldest, well-preserved supracrustal rocks on Earth.     

What conditions supply chain strategies of ports? The case of Dubai

Recent academic debates about port competition have centered on the strategic responses of port authorities, operators, managers and owners to the emergence of global supply chains. The competitive performance of a port authority or operator, given the rise of the integrated logistics sector, depends increasingly on its strategic relationship to these supply chains and rather less on traditional port competition factors such as hinterland size and physical infrastructure. However, there are few empirical studies investigating the degree to which particular port actors are capable of inserting themselves into global supply chains. In this article we ask what factors condition the supply chain strategies of port actors. We hypothesize that the strategic supply chain choices of a port authority or operator are conditioned by the territorialized institutional framework in which the dominant actors in a port operate. We apply these insights through a case study of the transformation of Dubai Port Authority, and the rise of Dubai Ports World (DPW).

Soil stabilization with microbially induced desaturation and precipitation (MIDP) by denitrification: a field study

Acta Geotechnica - A field trial was performed to test the feasibility of microbially induced desaturation and precipitation (MIDP) by denitrification for the stabilization of a silty soil....