Characterisation, classification, and evaluation of some groundwater samples in the Mostaganem area of northwestern Algeria

Mostaganem City, located in the northwestern part of Algeria, has grown and has been urbanized rapidly. The city and surrounding areas depend heavily on groundwater as a resource for drinking water, as well as domestic, industrial, and agricultural uses. Understanding the groundwater chemistry provides insight into the interactions of water with the environment and contributes to better resource management. In total, 12 groundwater samples from wells in Mostaganem City have been analyzed for major physical–chemical elements and metals. The results show that the waters have pH values ranging between 7.1 and 8.1, salinity between 226 and 1,073 mg/L, and nitrate concentrations between 15 and 47.7 mg/L. The high concentration of nitrates is explained by the utilization of chemical fertilizers in agriculture. Almost all samples are of type Na–SO₄ and Na–HCO₃, and the trace metal concentrations are within the admissible standard ranges. We conclude that the groundwater in Mostaganem may safely be used for drinking, domestic, agricultural, and industrial purposes.     

Gravity data analysis of Ungaran Volcano, Indonesia

Mount Ungaran is a Quaternary volcano located in the province of Central Java, Indonesia. The study area was covered by a gravity survey in order to delineate the subsurface structure and its relation to the hot springs that are spread throughout the area. The gravity data were analyzed using gravity gradient interpretation techniques, such as the horizontal gradient and Euler deconvolution methods, and many faults were detected. The results of the present study suggest that the hot springs around Ungaran Volcano are structurally controlled and have depths ranging from 1 to 3 km. The results of the present study lead to an understanding of the relationships between the interpreted faults and the locations of hot springs and may aid in future geothermal exploration of the area.     

Early warning indicators for river nutrient and sediment loads in tropical seagrass beds: a benchmark from a near-pristine archipelago in Indonesia

In remote, tropical areas human influences increase, potentially threatening pristine seagrass systems. We aim (i) to provide a bench-mark for a near-pristine seagrass system in an archipelago in East Kalimantan, by quantifying a large spectrum of abiotic and biotic properties in seagrass meadows and (ii) to identify early warning indicators for river sediment and nutrient loading, by comparing the seagrass meadow properties over a gradient with varying river influence. Abiotic properties of water column, pore water and sediment were less suitable indicators for increased sediment and nutrient loading than seagrass properties. Seagrass meadows strongly responded to higher sediment and nutrient loads and proximity to the coast by decreasing seagrass cover, standing stock, number of seagrass species, changing species composition and shifts in tissue contents. Our study confirms that nutrient loads are more important than water nutrient concentrations. We identify seagrass system variables that are suitable indicators for sediment and nutrient loading, also in rapid survey scenarios with once-only measurements.     

Fault pattern delineation and structural interpretation of the Gafsa trough (onshore central Tunisia) using gravity data

The purpose of this investigation was to identify subsurface lineaments in Gafsa trough (onshore central Tunisia) after gravity data analysis. The Bouguer and residual gravity maps show a gravity values decrease from west to east associated with subsidence variation and confirmed by a regional seismic reflection profile. The deep structural map of the study area is elaborated after the application of two methods: (1) the automatic lineament tracing after horizontal gravity gradient and (2) 3D Euler method. The dominant trends show approximately NW–SE, E–W, and NE–SW directions. Some of these trends are well correlated with the major faults systems. We can qualify the deep structuration model as a mosaic of quadratic blocks bounded by significant deep flower fault corridors. The elaborated structural map of the study area constitutes also a useful document for rationalizing the future petroleum exploration in the Gafsa trough.     

Joint evaluation of gravity, electrical and magnetotelluric methods for geothermal potential of fractured Aptian reefal carbonates in the Hmaima–El Gara area (Oued Serrat basin, Central–Western Tunisia)

Hmaima–El Gara area is located in Central–Western Tunisia and is known as an important geothermal province. In this study, we attempt to delineate the subsurface structures of the area using integrated interpretation of gravity, electrical and magnetotelluric data. The Hmaima thermal aquifer, associated with fractured Aptian reefal limestones, is characterized by high gravity and high resistivity. Horizontal gradient and Euler deconvolution method has been applied to the gravity data and provided fast information about both the depth and trends of the shallower subsurface structures in the area. As several of the mapped lineaments correlate with published geological fault trends, the other lineaments may be indicators of new insights for hydrothermal exploitation in the Hmaima–El Gara area (economical potential favorite zones).     

Structural Investigations of Afghanistan Deduced from Remote Sensing and Potential Field Data

This study integrates potential gravity and magnetic field data with remotely sensed images and geological data in an effort to understand the subsurface major geological structures in Afghanistan. Integrated analysis of Landsat SRTM data was applied for extraction of geological lineaments. The potential field data were analyzed using gradient interpretation techniques, such as analytic signal (AS), tilt derivative (TDR), horizontal gradient of the tilt derivative (HG-TDR), Euler Deconvolution (ED) and power spectrum methods, and results were correlated with known geological structures.The analysis of remote sensing data and potential field data reveals the regional geological structural characteristics of Afghanistan. The power spectrum analysis of magnetic and gravity data suggests shallow basement rocks at around 1 to 1.5 km depth. The results of TDR of potential field data are in agreement with the location of the major regional fault structures and also the location of the basins and swells, except in the Helmand region (SW Afghanistan) where many high potential field anomalies are observed and attributed to batholiths and near-surface volcanic rocks intrusions.A high-resolution airborne geophysical survey in the data sparse region of eastern Afghanistan is recommended in order to have a complete image of the potential field anomalies.     

3D Gravity Inversion using Tikhonov Regularization

Subsalt exploration for oil and gas is attractive in regions where 3D seismic depth-migration to recover the geometry of a salt base is difficult. Additional information to reduce the ambiguity in seismic images would be beneficial. Gravity data often serve these purposes in the petroleum industry. In this paper, the authors present an algorithm for a gravity inversion based on Tikhonov regularization and an automatically regularized solution process. They examined the 3D Euler deconvolution to extract the best anomaly source depth as a priori information to invert the gravity data and provided a synthetic example. Finally, they applied the gravity inversion to recently obtained gravity data from the Bandar Charak (Hormozgan, Iran) to identify its subsurface density structure. Their model showed the 3D shape of salt dome in this region.     

Evaluation of retention properties of a semi-synthetic fractured block from modelling at performance assessment time scales (Äspö Hard Rock Laboratory, Sweden)

Modelling of radionuclide transport in fractured media is a primary task for safety evaluation of a deep nuclear waste repository. A performance assessment (PA) model has been derived from site characterization data with the aim of improving confidence for quantifying transport of sorbing radionuclides at a safety time scale of 10⁶ y. The study was conducted on a 200?×?200?×?200 m semi-synthetic fractured block, providing a realistic system derived from the Äspö Hard Rock Laboratory (Sweden) dataset. The block includes 5,632 fractures ranging from 0.5 to 100 m in length and a heterogeneous matrix structure (fracture coating, gouge, mylonite, altered and non-altered diorite). The PA model integrates steady-state flow conditions and transport of released radionuclides during the safety time scale. An original simulation method was developed involving Eulerian flow and transport within fracture planes with a mixed hybrid finite element scheme and a semi-analytical source term to account for heterogeneous matrix diffusion. Total mass flux of radionuclides (conservative to strongly sorbing) was computed. A method to simplify the system was demonstrated, leading to a major path of 12 fractures. This is mainly due to the low connectivity of the fracture network. Matrix diffusion and sorption proved to have major impact on block retention properties for PA conditions.     

Imagery of the metamorphic bedrock roof of the Sahel active fault in the Sablettes (Algiers) reclaimed area by ambient vibration HVSR

The Sablettes (Algiers) coastal reclaimed fringe region, located on the hanging wall of the Sahel active fault, is subject to different types of geological hazard such as flood and tsunami, coastal uplift, earthquake, liquefaction, landslide, and site effects. In this present work, we used ambient vibration HVSR for imaging the bedrock. The thickness of the sedimentary column under the backfill layer is unknown, and the coastal reclaimed areas are prone to strong amplification of seismic waves. The determination of the depth of the metamorphic base allowed us to establish a mapping of the bedrock roof surface. The 3D representation of this surface enabled us to present models of tectonic structures in this basement (i.e., fault, fold). This analysis will make it possible to make better evaluation of the amplification after having determined the depth of the metamorphic basement exceeding 240 m, which is supposed to have velocities close to those of the seismological basement, as well as the thicknesses of the different layers surmounting it.     

Petrographisch-lagerstättenkundliche Untersuchung der Kupferlagerstätte Sar Cheshmeh (Süd-Iran)

Zusammenfassung Die Cu-Lagerstätte Sar Cheshmeh liegt im Süd-Iran in einer Vulkanitzone, die in 150 km Abstand nördlich parallel zur Zagrosüberschiebung verläuft. Die Lagerstätte ist an einen latitandesitischen bis rhyodazitischen Gesteinskomplex gebunden. Die auftretenden zonaren Vererzungen und hydrothermalen Alterationen des Nebengesteins weisen auf eine porphyry copper-ore-Lagerstätte hin. Aus den vorliegenden Untersuchungen und im Sinne der Plattentektonik ergibt sich, daß der Sar Cheshmeh-Gesteinskomplex von Magmen des Kontinentralrandes gebildet wurde. Gleiches gilt für die Andesitformation von Ardestan im zentralen Iran. Die Wurzel der Magmenherde liegt wahrscheinlich in einer Tiefe von ca. 140 bis 160 km, was in etwa der Tiefenlage der Benioff-Zone entspricht.

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The copper ore deposit of Sar Cheshmeh in South Iran is situated in a volcanic zone which runs 150 kms north parallel to the Zagros overthrust. The orebody lies within a latitandesite-rhyodazite complex. The mineral zoning and the hydrothermal alteration of the rocks indicate a porphyry copper ore deposit. According to the plate tectonic theory the Sar Cheshmeh rock complex is formed by rocks of the continental margin type. The same applies to the andesite formation of Ardestan in Central Iran. The magmas orginated probably at a depth of 140–160 kms, this being also the depth of the Benioff zone.

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Résumé Le gisement métallifère de cuivre de Sar Cheshmeh en Iran du Sud est situé dans une zone volcanique parallèle au charriage du Zagros, à 150 km au nord. Il se trouve dans un complexe de latiteandésite-rhyodacite. La zone minéralisée et l'altération hydrothermale des roches indiquent un gisement de minerai de cuivre porphyrique. Selon la théorie des plaques, le complexe des roches de Sar Cheshmeh est formé de roches du type marge continentale. Cela vaut aussi pour la formation andésitique d'Ardestan en Iran central. Le magma provient probablement d'une profondeur de 140 à 160 km, ce qui corresponde à peu près à la Zone de Bénioff.

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