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The Gantour Phosphatic Basin (GPB) is formed by a sedimentary series of Maastrichtian to the Eocene age, which consists of alternating phosphate layers and sterile levels. This series outcrops in the northern part of the basin, where it is exploited in open-pit mines. The exploration methodology employed by the Office Chérifien des Phosphates (OCP) group to investigate the GPB is based on direct recognition with boreholes drilled on a 500 × 500 m grid. This research is concerned with the compilation and analysis of data collected during several drilling campaigns conducted on the central segment of the GPB, namely the Louta deposit. This research also includes acquiring, processing, and interpreting new geophysical and hydrogeological data. Its main objective is to provide a better understanding of the deep structure of the phosphatic series. Therefore, the present study was carried out according to a multidisciplinary approach that comprises three parts. (i) The first one involves geological modeling of the exploration borehole data using Datamine Studio RM software (version 1.4), developed by Datamine Corporate Ltd., (Bristol, United Kingdom). It results in establishing a series of geological cross-sections that display a detailed view of the deep structure of the phosphatic series and its lateral variations. (ii) The second part is related to the hydrogeological study, whose purpose was to elaborate on an accurate and updated piezometric map of the study area. The new map helps understand the groundwater flow in the Louta deposit. Furthermore, the superimposition of the piezometric level with the geological sections throws light on the flooded volume of phosphate in this deposit. (iii) The third part of the study focuses on implementing the Electrical Resistivity Tomography (ERT) method. The interpretation of the recorded geoelectrical data not only highlights the main features controlling the mode and the proportion of the phosphate series deepening under the Plio-Quaternary cover but also confirms the evolution of the overall structure of the studied area. The obtained 2D ERT models generally corroborate the cross-sections produced by geological modeling. They also correlate with the information provided by the hydrogeological study. Such information will help guide future hydrogeological and mining extraction planning in the studied area. [ABSTRACT FROM AUTHOR]

The Essaouira Basin, located in central western Morocco, faces a significant threat of water shortage due to both the substantially reduced rainfall caused by climate change and the continuously increasing demand for this essential resource. Groundwater resources are being increasingly exploited to meet the needs of the population, whether for agricultural or domestic purposes. Therefore, it has become necessary to intensify investigations across the entire basin, particularly through indirect methods such as geophysical techniques, to accurately delineate the productive zones. In this context, the present study was undertaken to investigate the deep structure of this basin with the aim of comprehending the functioning of its aquifer system. This study is based on the interpretation of gravity data covering the Essaouira Basin. In addition to their qualitative analysis, these data underwent a methodological approach involving transformations to extract meaningful insights. The observed anomalies were interpreted in terms of (i) thickness variations within the slightly folded sedimentary series of the basin; (ii) Paleozoic basement topography; and (iii) the presence of salt deposits. In fact, among the negative anomalies, some coincide with evaporitic deposits that are known either from the geological outcrops or the seismic surveys carried out in the Essaouira Basin within the framework of petroleum exploration programs, while others coincide with areas of increased thickness of sedimentary sequences. The latter include synclines and basement depressions, where the accumulation of groundwater tends to occur; as a result, they constitute suitable zones for the drilling of water extraction wells. Groundwater flows observed in some existing wells are consistent with this hypothesis. The results of the contact analysis approach implemented within the framework of the study reveals the Essaouira Basin is affected by a fault network whose main direction is parallel to the Atlantic margin (i.e., NNE–SSW). This implies that the extensional tectonic phase responsible for initiating the rifting of the Central Atlantic in the Triassic era has primarily impacted the structural configuration of this basin. This study demonstrates the strong potential of the gravity method as a tool to delineate the deep structure of sedimentary basins and to identify potentially productive groundwater zones. The final results will provide important support to decision makers in sustainable groundwater management, especially in vulnerable areas. [ABSTRACT FROM AUTHOR]

The Sidi Ifni region in southwest Morocco is mainly composed of crystalline rocks with limited groundwater storage capacity. These water resources drain in particular fault zones with high fracture permeability. The main objective of this study is to describe the geological structure of the region to optimize future drilling locations. The gravity data were processed using various techniques, such as total horizontal gradient, tilt derivative, and Euler deconvolution, in conjunction with the interpretation of the geological data, to create a new structural map. This map confirms the presence of many previously identified or inferred faults and identifies significant new faults with their respective trends and depths. Analysis of this map shows that major faults are oriented NNE-SSW and NE-SW, while minor faults are oriented E-W, NW-SE, and NNW-SSE. The superposition of the hydrogeological data and the structural map reveals that the high groundwater flow values in the boreholes are located in the vicinity of the major faults and talwegs. The structures deduced from the filtering and interpretation of the gravity data suggest that the hydrogeological system of the Ifni Inlier is controlled by its structures. To confirm this impact, a high-resolution electrical resistivity map (7200 Hz) was used, with penetration depths ranging from 84 to 187 m. Negative boreholes, located in high resistivity ranges corresponding to sound basement formations without fault crossings, showed high resistivity values. The positive holes, located in anomalies with low linear resistivity, revealed the impact of fault crossings, which drain water and tend to decrease the resistivity values of the formations. Therefore, these new structural maps will assist in planning future hydrogeological studies in this area. [ABSTRACT FROM AUTHOR]

The Ouled Abdoun sedimentary basin in Morocco contains the largest phosphate reserves in the world. To the Northwest of the basin, the phosphate layers crop out or are at a shallow depth and are exploited in open pit mines. By contrast, towards the central and southwestern parts of the basin, the phosphate layers lay below the Plio-Quaternary sediments of the Tadla Plain. This study aims to characterize the distribution and structure of the phosphatic series at depth under this cover, in particular to guide the future exploration and exploitation of the phosphate deposits. The work is based on gravimetric and seismic data acquired in a previous oil exploration study, calibrated by borehole data. The analysis of the gravity data controlled by boreholes first reveals the existence of large regional faults in the basin, forming pronounced gradients in the gravity data. The faults are also seen in the seismic profiles. In the Southeast of the basin, the phosphatic series exhibit a stairway structure controlled by some of these regional faults. The drilling data and the isochron maps established from the seismic profiles show that the base of the phosphatic series is more than 500 m deep in the southeastern area of the basin. As the phosphatic layers get buried deeper, they also become thicker. The phosphate reserves thus increase towards the southeast, and our analysis identifies the areas where this reserve is larger. Our results eventually suggest that the mining methods currently adopted in the Khouribga mining district will need to be modified and adapted to the more complex situation of the phosphatic series deeply buried in the basin. [ABSTRACT FROM AUTHOR]

The Bou Azzer-El Graara inlier (BAEI) in the Central Anti-Atlas has been extensively studied due to its famous Pan-African ophiolite and its great mineral potential. In 1998, an airborne survey was flown over this inlier, providing high-resolution magnetic data. This study is concerned with reinterpreting these data to help elucidate the BAEI structure. For this purpose, the aeromagnetic data were processed through a series of filters and transformations. They were then subjected to a detailed analysis, taking into account the study area geology. Qualitative analysis of the reduced to pole data indicates that the observed anomalies are broadly consistent with outcrops of Precambrian mafic and metavolcanic rocks in the BAEI. The extension of this type of rocks below the Paleozoic sedimentary cover could explain similar anomalies found outside the inlier. Additional analysis of the processed data helped to identify various lineaments and structures organized into two main trends: ENE-WSW and ESE-WNW. Furthermore, the calculation of anomalous source depths by Euler deconvolution from aeromagnetic data shows that these vary between 0 and 1000 m within the inlier. However, deeper sources occur beneath the detached and slightly folded Paleozoic sedimentary deposits in the northern part of the inlier. Moreover, a quantitative interpretation using the 3D inverse method was applied to high-amplitude anomalies associated with the Bou Azzer ophiolite (BAO) and the Foum Zguid great dyke (FZGD). The results indicate that (i) the BAO consists of three north-northeast dipping magnetic bodies, (ii) the FZGD corresponds to a deeply rooted vertical structure with lateral thickness variations and (iii) the NE-SW FZGD structure represents the eastern limit of the BAO as indicated by geological and magnetic data. This suggests that the FZGD fracture may have played an important role during the Pan-African collages as a key structure controlling the oblique suturing of the ophiolite slices. • We perform a structural interpretation of aeromagnetic data from Bou Azzer inlier. • The anomalies are generally associated with mafic rocks and metavolcanics outcrops. • We delineated magnetic lineaments and structures dissecting the study area. • We carry out a 3D modeling of the Bou Azzer ophiolite and the Foum Zguid dyke. [ABSTRACT FROM AUTHOR]

The Western Bahira Basin (WBB), located in Central Morocco, is known for its large reserves of phosphate, which are currently being extracted through open pit mines within the Gantour Phosphatic Plateau (GPP). This mining activity, as well as the increasing agricultural development that this region has been experiencing during the last few decades, has subjected the groundwater in this semi-arid region to intense exploitation through pumping. Consequently, thorough knowledge of the underground water resources is essential for sustained activity. This study uses gravity data to investigate the deep geologic structure of the western Bahira and Gantour plateau area. Its main purpose is to improve the knowledge of this structure that influences the groundwater dynamics. The methodology involves, in addition to the qualitative and quantitative interpretation of the gravity data, the use of various filtering and analysis techniques to highlight the major geological structures. In fact, a qualitative analysis of the residual gravity map shows that the observed anomalies can be explained in terms of the bedrock topography of the study area. Positive anomalies spatially correlate with the outcrops of this bedrock in the Hercynian massifs of Jebilet and Rehamna, as well as with the Douar Rhirat structural high. The negative anomalies, on the other hand, tend to reflect increased thicknesses of sedimentary sequences, such as in the southern part of the WBB. Moreover, the Brikyine granite in the north of the study area is noticeably associated with the highest amplitude negative anomaly. Analysis of the residual gravity data using the total horizontal gradient, upward continuation, and Euler deconvolution techniques provides a quantitative assessment of the geologic structure. These methods help delineate various structures oriented in two main directions: N45E and N105E. Among these structures, several major faults have been identified. They are rooted at a maximum depth in excess of 2800 m. These faults are responsible for the general structure of the study area and the morphology of the basement. Furthermore, the 2D forward modeling, performed across the main negative gravity anomalies of the WBB, helps characterize the Paleozoic bedrock topography and provides more constraints on its variation. The resultant gravity models clearly show an asymmetric structure for the western Bahira trough. This depression is filled by sedimentary formations whose thickness at the depot-center can locally reach 1200 m. Additional analysis of piezometric data shows that the groundwater flows are controlled by the gravity structures highlighted in this study. • The structure of the western Bahira and Gantour area was inferred from gravity data. • The gravity anomalies clearly correlate with the topography of Hercynian basement. • We delineated and characterized structural features that dissect the study area. • The obtained results underpins future hydrogeological studies of the study area. [ABSTRACT FROM AUTHOR]

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Les rejets sulfurés de la mine abandonnée de Kettara, située à 30 km au Nord-Nord-Ouest de Marrakech, sont directement entreposés sur un substratum schisto-gréseux fracturé. D'une superficie d'environ 16 ha, ils constituent une réelle source de pollution pour l'écosystème local en particulier à cause du Drainage Minier Acide (DMA) vers les eaux de surface et de la nappe phréatique. Le projet de réhabilitation du site minier de Kettara prévoit dans l'un de ses axes de minimiser l'effet DMA par neutralisation à l'aide de dépôts stériles riches en carbonates issus de l'extraction des phosphates de la mine de Youssoufia voisine. Ces derniers seront utilisés à la fois comme amendement des rejets miniers acides et comme couverture évapo-transpirante (barrière capillaire). Notre étude a permis d'une part, de mieux appréhender la nature et la structure du parc à résidus et de son substratum et d'autre part, de caractériser l'impact de ces résidus sur la qualité des ressources en eau souterraine. Les résultats issus de cette étude vont contribuer à la réussite du projet de réhabilitation du site. Editeur Z.W. Kundzewicz Citation Lghoul, M., Kchikach, A., Hakkou, R., Zouhri, L., Guerin, R., Bendjoudi, H., Teíxido, T., Antonio Penã, J., Enriqué, L., Jaffal, M. et Hanich, L., 2012. Etude géophysique et hydrogéologique du site minier abandonné de Kettara (région de Marrakech, Maroc): contribution au projet de réhabilitation. Hydrological Sciences Journal, 57 (2), 370–381. [ABSTRACT FROM PUBLISHER]

Abstract: The Marrakech region is known for its significant mining potential concealed by the Hercynian basement. In order to extend the exploration of this basement beyond its outcrops in the Jebilets and Guemassa massifs, we used magnetic and gravity data from a sub-area in the Haouz basin. Our methodology in this study consists of processing the data, so as to highlight the buried geological contacts and to reveal their dips. The study of the geological contacts is ensured by the upward continuation processing of the residual gravity map at various altitudes, followed by the determination of the horizontal gradient maxima for each level. The progressive migration of these maxima while increasing the upward continuation altitude indicates the dip direction. The structures deduced from gravity are superimposed on the magnetic map in order to emphasize their possible association with magnetic sources. Comparison between gravity anomalies and local geology shows that these anomalies are mainly caused by basement topography undulations. Moreover, lows coincide with granite and thick sedimentary depressions while highs coincide with basement outcrops. The local maxima of the horizontal gradient of the residual gravity data and its upward continuation at various altitudes define a field of features, organized into groups oriented both NE–SW and NW–SE, which correspond to the regional Hercynian structures. Moreover, the main highlighted lineaments coincide perfectly with known fractures such as the North-Atlas and the Guemassa faults whose dip and direction are well documented. These detected features allow us to complete and enrich the structural map of the Haouz basin. A joint detailed analysis of the mapped gravity contacts and the magnetic data was carried out, through the use of Magnetic and Gravity Euler Trends in terms of depth and rooting, taking into account the local geology, to identify potential structures for mining exploration. [ABSTRACT FROM AUTHOR]

Abstract: During the SISMAR cruise (spring 2001), new deep seismic data were acquired on the Atlantic Moroccan margin. The purpose of the present work is to analyse and to interpret a part of the data consisting of four wide-angle seismic profiles (4, 5, 8 and 10) recorded offshore El Jadida. Lines 4 and 5, perpendicular to the margin, show a crustal thickness of 35km under the western Moroccan Meseta which thins progressively seaward where it reaches a minimum thickness of 10km. The calculated velocity models show that this crust consists of two crustal layers overlain by a sedimentary cover corresponding to the post-Paleozoic sediments, characterised by a low velocity. The detailed shallow structure is obtained primarily from multichannel seismic data. Half grabens are imaged and display deeper basins located at the foot of the continental slope where the sedimentary cover reaches a maximum thickness of 6km. The sedimentary strata are disrupted by salt migration along faults and forming diapirs. The first crustal unit corresponds to the upper crust, with p-wave velocities ranging from 6km/s at the top to 6.5km/s at the base. The lower crust represented by the second unit is characterized by velocities increasing from 6.7 to 7.5km/s at the base of the lower crust. [Copyright &y& Elsevier]

Abstract: Aeromagnetic data of the Anti-Atlas Mountains show an important magnetic anomaly along the ‘Major Anti-Atlas Fault’, produced by different mafic and ultramafic rocks of a Neoproterozoic ophiolite complex. The magnetic modelling of Bou Azzer–El Graara ophiolitic suture shows a deep-seated anomaly through the upper continental crust corresponding to a north-dipping subduction. The polarity of the Pan-African subduction in the Anti-Atlas is therefore compatible with the contemporaneous Pan-African orogenic belts, where polarity of subduction dipped away from the West African Craton during the amalgamation of Western Gondwana. To cite this article: A. Soulaimani et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

A large number of seismic reflection lines and boreholes have been carried out in the Essaouira Basin by the oil industry. The present study concentrates on the reinterpretation of these data in the restricted area of Khemis Meskala, in order to better characterise the structure of the Cretaceous aquiferous system. The reflector corresponding to the bottom of the Vraconian formation has been identified on the different seismic sections. This horizon, which marks the base of the aquiferous system, was first digitised on time migration sections and then converted to depth sections using a suitable linear velocity law. The isobath map of the bottom of the Vraconian resulting from this study images the 3D geometrical structure of this horizon and shows that it is slightly folded in domes and basins. This document will be useful for rationalising the future hydrogeological researches that will be undertaken in the Khemis Meskala area. To cite this article: M. Jaffal et al., C. R. Geoscience 334 (2002) 229–234. [Copyright &y& Elsevier]

The Moroccan phosphate deposits are the largest in the world. Phosphatic layers are extracted in open-pit mines mainly in the sedimentary basins of Gantour and Ouled Abdoun in Central Morocco. The purpose of this study was to prospect and evaluate the water potential of aquifers incorporated in the phosphatic series using the following geophysical methods: Magnetic resonance sounding (MRS), electrical resistivity tomography (ERT), time-domain electromagnetics (TDEM), and frequency-domain electromagnetics (FDEM). The objective was, on the one hand, to contribute to the success of the drinking water supply program in rural areas around mining sites, and on the other hand, to delimit flooded layers in the phosphatic series to predict the necessary mining design for their extraction. The use of geophysical methods made it possible to stratigraphically locate the most important aquifers of the phosphatic series. Their hydraulic parameters can be evaluated using the MRS method while the mapping of their recharge areas is possible through FDEM surveys. The results obtained in two selected experimental zones in the mining sites of Youssoufia and Khouribga are discussed in this paper. The application of the implemented approach to large phosphate mines is in progress in partnership with the mining industry. [ABSTRACT FROM AUTHOR]

This study provides new elements that illustrate the benefits of combining gravity, structural, stratigraphic and piezometric data for hydrogeological purposes. A combined methodology was applied to the western Haouz aquifer (Morocco), one of the main sources of water for irrigation and human consumption in the Marrakech region. First, a residual anomaly map was calculated from the Bouguer anomaly data. The computed map provided information on the ground density variation, revealing a strong control by a regional gradient. We then used various filtering techniques to delineate the major geological structures such as faults and basins: vertical and horizontal derivatives and upward continuation. This technique highlighted news structures and provided information on their dip. The gravity anomalies perfectly delineated the basement uplifts and the sedimentary thickening in depressions and grabens. The interpretation of gravimetric filtering, geological and hydrogeological data then highlighted two types of groundwater reservoirs, an unconfined aquifer hosted in conglomeratic mio-pliocene and quaternary rocks, covering the entire western Haouz and a deep confined aquifer contained in cenomanian-turonian limestone and eocene dolomitic formations in the south. Combining piezometric and residual anomaly maps revealed that groundwater flow and storage was in perfect agreement with the structures showing a negative anomaly, while structures with positive anomalies corresponded to groundwater divides. The study of gravity gradient zones by contact analysis enhanced the existing structural pattern of the study area and highlighted new structures, mainly oriented N70 and N130. The results of this study present a common framework and provide a notable step forward in the knowledge of the geometry and the groundwater flow pattern of the western Haouz aquifer, and will serve as a solid basis for a better water resource management. [ABSTRACT FROM AUTHOR]

Abstract: Exploitation of the phosphatic layers in Sidi Chennane deposit (Morocco) collides frequently with problems bound to the existence, in the phosphatic series, of sterile bodies qualified as derangements. Our study shows that these bodies, masked by the Quaternary cover can be mapped using the Time-Domain ElectroMagnetic Soundings method (TDEM). It is based on the acquisition and the interpretation of a series of tests carried out above a visible derangement in an old trench of exploitation and on 2500 TDEM soundings carried out in a virgin area of the deposit. The article concerns to the analysis of the results and of the proceeding for a possible large geophysics survey. To cite this article: A. Kchikach et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]