An insight on the polyphase thermal history of the Internal Rif (Northern Morocco) through Raman micro-spectroscopy investigation

We are greatly indebted with M.N. Zaghloul for fruitful discussions and for introduce us to Rif geology. We kindly acknowledge the Editor in chief Federico Rossetti, the associated editor Giulio Viola and two anonymous reviewers for their constructive criticisms that improved the original version of this paper.Peer reviewedPostprin

Oligo-Miocene thinning of the Beni Bousera peridotites and their Variscan crustal host rocks, Internal Rif, Morocco†

International audienceDeciphering Variscan versus Alpine history in the internal Rif system is a key to constraining the tectonic evolution of the Alboran domain and hence the geodynamics of the western Mediterranean system during the Cenozoic. This study focuses on the evolution of the metamorphic envelope of the Beni Bousera massif and its relation to the underlying peridotites. Combining structural geology, metamorphic petrology, and LA-ICP-MS U-Th-Pb dating of monazite, this study contributes to the understanding of the tectonic history of the western internal Rif. The regional foliation (S2) is characterized by LP/HT mineral assemblages and obliterates a former foliation (S1) developed along a barrovian (MP/MT) metamorphic gradient. The dating of some metamorphic monazite grains from a micaschist and a migmatitic gneiss demonstrates that the crustal envelope of the peridotite recorded two distinct tectonometamorphic episodes. Data from monazite inclusions in S1 garnet suggest that the first event, D1, is older than 250-170 Ma and likely related to the Variscan collision, in agreement with the barrovian type of the metamorphic gradient. The second event, D2, is Alpine in age (at circa 21 Ma) and corresponds to a strong lithosphere thinning allowing subsequent subcontinental mantle exhumation. Such a tectonic context provides an explanation for the LP/HT metamorphic gradient that is recorded in the regional foliation of the western Betic-Rif system. This extension is probably related to a subduction slab roll-back in the western end of the Mediterranean realm during the Oligo-Miocene times. No evidences for a Tertiary HP/LT metamorphism have been identified in the studied are

Apport de L’hydrochimie, la Fracturation et des Méthodes D’analyses Statistiques pour Caractériser les Eaux Souterrains du Massif Calcareux de la Région de Tlata Taghramt, Chaîne Calcaire du Haouz (Rif Septentrional, Maroc)

L’objectif de cette étude est de fournir les caractéristiques hydrogéologiques et hydrochimiques des eaux souterraines des roches carbonatées de la région de Tlata Taghramt. Géographiquement, cette région fait partie de la chaîne calcaire du Haouz central (Rif septentrional). La majorité des sources se localisent le long des contacts anormaux majeurs qui mettent en contact les formations carbonatées avec les formations imperméables (Sebtides/Ghomarides à l’Est et les masses des Flyschs/unités de Tanger à l’Ouest). Dans ce secteur, les formations carbonatées constituent un important réservoir karstique dont l’alimentation principale se fait par les précipitations. L'étude de la fracturation a clairement indiqué une dominance de fractures orientée N-S. Ces dernières favorisent l’apparition d’un grand nombre de sources via les joints et les sutures affectant les roches réservoirs formants les aquifères de la région. La détermination des principaux groupes de facteurs participant à la minéralisation des eaux a été réalisée par méthode d’analyse statistique. Du point de vue chimique, les eaux ont une nature généralement bicarbonatée calcique et magnésienne. Ces ressources hydriques sont la principale ressource d’eau potable et d’irrigation pour les centres ruraux de la région.   The objective of this study is to provide the hydrogeological and hydrochemical characteristics of the groundwater of carbonate rocks in the Tlata Taghramt region. Geographically, this region is part of the central Haouz limestone chain (northern Rif). Most of springs are located along the major abnormal contacts between the carbonate formations and the impermeable formations (Sebtides/Ghomarids in the east and the Flyshs/Tangier units in the west). In this sector, the carbonate formations constitute an important karstic reservoir, which is mainly supplied by rainfall. The study of the fracturing clearly indicated a dominance of N-S oriented fracturing. This fracturing favors the appearance of a large number of springs across the joints and sutures affecting the reservoir rocks that form the region's aquifers. The determination of the main groups of factors involved in water mineralization was carried out by statistical analysis. From a chemical point of view, the waters are generally bicarbonate-calcic and magnesian type. These water resources are the main source of drinking water and irrigation in the region's rural centers

Apport de L’hydrochimie, la Fracturation et des Méthodes D’analyses Statistiques pour Caractériser les Eaux Souterrains du Massif Calcareux de la Région de Tlata Taghramt, Chaîne Calcaire du Haouz (Rif Septentrional, Maroc)

L’objectif de cette étude est de fournir les caractéristiques hydrogéologiques et hydrochimiques des eaux souterraines des roches carbonatées de la région de Tlata Taghramt. Géographiquement, cette région fait partie de la chaîne calcaire du Haouz central (Rif septentrional). La majorité des sources se localisent le long des contacts anormaux majeurs qui mettent en contact les formations carbonatées avec les formations imperméables (Sebtides/Ghomarides à l’Est et les masses des Flyschs/unités de Tanger à l’Ouest). Dans ce secteur, les formations carbonatées constituent un important réservoir karstique dont l’alimentation principale se fait par les précipitations. L'étude de la fracturation a clairement indiqué une dominance de fractures orientée N-S. Ces dernières favorisent l’apparition d’un grand nombre de sources via les joints et les sutures affectant les roches réservoirs formants les aquifères de la région. La détermination des principaux groupes de facteurs participant à la minéralisation des eaux a été réalisée par méthode d’analyse statistique. Du point de vue chimique, les eaux ont une nature généralement bicarbonatée calcique et magnésienne. Ces ressources hydriques sont la principale ressource d’eau potable et d’irrigation pour les centres ruraux de la région.   The objective of this study is to provide the hydrogeological and hydrochemical characteristics of the groundwater of carbonate rocks in the Tlata Taghramt region. Geographically, this region is part of the central Haouz limestone chain (northern Rif). Most of springs are located along the major abnormal contacts between the carbonate formations and the impermeable formations (Sebtides/Ghomarids in the east and the Flyshs/Tangier units in the west). In this sector, the carbonate formations constitute an important karstic reservoir, which is mainly supplied by rainfall. The study of the fracturing clearly indicated a dominance of N-S oriented fracturing. This fracturing favors the appearance of a large number of springs across the joints and sutures affecting the reservoir rocks that form the region's aquifers. The determination of the main groups of factors involved in water mineralization was carried out by statistical analysis. From a chemical point of view, the waters are generally bicarbonate-calcic and magnesian type. These water resources are the main source of drinking water and irrigation in the region's rural centers

Lateral variations of pressure-temperature evolution in non-cylindrical orogens and 3-D subduction dynamics: the Betic-Rif Cordillera example

This paper is a contribution of the Orogen project funded by Total, BRGM and CNRS-INSU and it benefited from numerous discussions with the Orogen community. The 40Ar/39Ar facility at ISTO was funded and is supported by the ERC Advanced grant RHEOLITH, the LABEX project VOLTAIRE (ANR-10-LABX-100-01), the Région Centre project ARGON, and the project EQUIPEX PLANEX (ANR-11-EQPX-0036). We would to thank the guest-editor David Pedreira and the two reviewers, Juan Soto and André Michard for a really extensive analysis of our manuscript, which is obviously in better shape now. Special thanks are due to Federico Rossetti who commented on an early version of the manuscript.The long-term Pressure-Temperature-time-deformation (P-T-t-d) evolution of the internal zones of orogens results from complex interactions between the subducting lithosphere, the overriding plate and the intervening asthenosphere. 2-D numerical models successfully reproduce natural P-T-t-d paths, but most orogens are non-cylindrical and the situation is far more complex due to 3-D pre-orogenic inheritance and 3-D subduction dynamics. The Mediterranean orogens are intrinsically non-cylindrical. Their 3-D geometry results from the complex shape of the Eurasian and African margins before convergence and from the dynamics of slab retreat and tearing leading to strongly arcuate belts. More than many other segments, the Betic-Rif belt is archetypal of this behavior. A synthesis of the tectonometamorphic evolution of the Internal Zones, also based on recent findings by our group in the framework of the Orogen Project (Alboran domain, including the Alpujarride-Sebtide and Nevado-Filabride complexes) shows the relations in space and time between tectonic and P-T evolutions. The reinterpretation of the contact between peridotite massifs and Mesozoic sediments as an extensional detachment leads to a discussion of the geodynamic setting and timing of mantle exhumation. Based on new Ar-40/Ar-39 ages in the Alpujarride-Sebtide complex and a discussion of published ages in the Nevado-Filabride complex, we conclude that the age of the HP-LT metamorphism is Eocene in all complexes. A first-order observation is the contrast between the well-preserved Eocene HP-LT blueschists-facies rocks of the eastern Alpujarride-Sebtide Complex and the younger HT-LP conditions reaching partial melting recorded in the Western Alpujarride. We propose a model where the large longitudinal variations in the P-T evolution are mainly due to (i) differences in the timing of subduction and exhumation, (ii) the nature of the subducting lithosphere and (iii) a major change in subduction dynamics at similar to 20 Ma associated with a slab-tearing event. The clustering of radiometric ages obtained with different methods around 20 Ma results from a regional exhumation episode coeval with slab tearing, westward migration of the trench, back-arc extension and thrusting of the whole orogen onto the African and Iberian margins.TotalBRGMCentre National de la Recherche Scientifique (CNRS)ERC Advanced grant RHEOLITHLABEX project VOLTAIRE ANR-10-LABX-100-01Region Centre project ARGONproject EQUIPEX PLANEX ANR-11-EQPX-003

Apport de la Fracturation et des Méthodes d’analyses Statistiques à l’etude Hydrogéochimique des Eaux Souterraines du Massif Calcareux de la Région de Tlata Taghramt, Chaîne Calcaire du Haouz (Rif Septentrional, Maroc)

L’objectif de cette étude vise à établir les caractéristiques hydrogéologiques et hydrochimiques des eaux souterraines des formations carbonatées de la région de Tlata Taghramt. Au total, 16 échantillons d'eau ont été prélevés pour l’analyse chimique. Le traitement des données hydrochimiques a été réalisé à l'aide de diagrammes de Piper, les indices de saturation en minéraux et à base des méthodes d’analyses statistiques. Les paramètres physiques tels que la conductivité électrique, le potentiel hydrogène et les températures ont été mesurés sur le terrain à savoir que : la conductivité électrique varie entre 403μS/cm et 925μS/cm, le potentiel hydrogène varie entre 7.55 et 8.04 et les températures varient entre 15°C et 18°C. L'analyse hydrochimique montre une abondance en éléments majeurs (Anions et Cations) respectivement par ordre décroissant : (HCO3-> Cl- > SO42- > NO3-) et (Ca2+ > Mg2+ >Na+ > K+). Les bicarbonates représentent 70% du total des anions, tandis que le calcium représente 12% du total des cations. Cet enrichissement en ces deux éléments traduit la nature carbonatée des formations géologiques traversées par les eaux souterraines ainsi l'interaction de l'eau avec la matrice du système aquifère. L'étude de la fracturation indique une dominance de fractures orientées N-S favorisant l’apparition des sources via les joints et les sutures affectant les roches réservoirs. De point de vue chimique, les eaux des sources ont une nature généralement bicarbonatée calcique et magnésienne.   This study aims to establish the hydrogeological and hydrochemical characteristics of groundwater of carbonate rocks in the Tlata Taghramt region. A total of 16 water samples were collected for chemical analysis. Hydrochemical data processing was carried out using Piper diagrams, mineral saturation indices and statistical analysis methods. Physical parameters such as Electrical Conductivity, PH and Temperatures were measured in the field. The EC varies between 403μS/cm and 925μS/cm, the PH varies between 7.55 and 8.04 and the temperatures vary between 15°C and 18°C. Hydrochemical analysis shows an abundance of major elements (Anions and Cations) respectively in descending order: (HCO3-> Cl- > SO42- > NO3-) and (Ca2+ > Mg2+ >Na+ > K+). Bicarbonates account for 70% of total anions, while calcium accounts for 12% of total cations. This enrichment in these two elements reflects the carbonate nature of the geological formations crossed by the groundwater and the interaction of water with the aquifer system matrix. The study of fracturing indicates a dominance of N-S oriented fractures favoring the appearance of sources via joints and sutures affecting reservoir rocks. From a chemical point of view, spring waters have a calcium and magnesium bicarbonate-type facies

Évolution des mouvements verticaux néogènes de la chaîne du Rif (Nord-Maroc) : apports d’une analyse structurale et thermochronologique

The Rif chain (Northern Morocco) belongs, with the Betic Cordillera (Southern Spain), to the westernmost part of the Alpine belt. This sector is one of the main targets for the comprehension of vertical movements linked to orogenic processes. Despite the numerous investigations lead on the Pliocene uplifted deposits in the Rif Chain, the timing and amplitude of the vertical motions subsequent to the period of cooling have never been constrained. This work aims to discuss the geodynamical processes involved in the vertical motion of the Rif margin since the Neogene. A comparison between the vertical movements determined in the internal zones and estimated in the flyschs domain (South of Jebha fault), has been realized on the basis of AHe data. Correlations reported between the vertical movements and the evolution of the stress field highlighted the linkage between the main stages of vertical motion and extension period with a radial pattern. 1-The latest exhumation stages of the deep-seated metamorphic rocks, from 12-10 km of depth, were triggered by the radial extension of these units. The collapse extended from the low grade metamorphism (Greenschists facies) to the brittle strata during the Aquitano-Burdigalian times. This extension is expressed in the superficial units, whereas deepest parts and sectors at the front of the Rif chain underwent a compression. 2-A second uplift stage proceeds at a very slow raising pace and is associated to radial extension in throughout the internal zones since the Lower Pliocene. Le flyschs sector was uplifted faster since the Late Miocene.La chaîne du Rif (Nord du Maroc) constitue, avec les Cordillères des Bétiques (Sud de l’Espagne), la terminaison occidentale de la ceinture alpine. C’est un secteur clé pour la compréhension des mouvements verticaux associés aux processus orogéniques. Jusqu’à présent, aucune étude n’a permis de contraindre les mouvements verticaux postérieurs au Miocène inférieur, malgré la présence de dépôts marins pliocènes surélevés. L’objectif de ce travail est d’apporter des arguments permettant de discuter des mécanismes géochronologiques et cinématiques impliqués dans les mouvements verticaux de la marge du Rif depuis le Néogène. Une comparaison des déplacements identifiés dans les zones internes, a pu être effectuée, avec ceux estimés dans le domaine des flyschs (Sud de l’accident de Jebha), grâce aux données AHe. Les corrélations entre mouvements verticaux et évolution du champ de déformation mettent en évidence le lien existant entre les périodes de mouvements verticaux majeurs et les phases d’extension radiale. 1-Les derniers stades d’exhumation des unités métamorphiques, depuis près de 12-10 km de profondeur, résultent d’un stade d’extension radiale affectant ces formations. Le domaine de collapse s’étend depuis le faciès Schiste Vert jusqu’au domaine fragile durant l’Aquitano-Burdigalien. Les mouvements extensifs sont limités aux parties superficielles de l’orogène tandis que les parties plus profondes et situées en avant-chaîne sont en compression. 2-Une période de surrection lente associée à de l’extension radiale, affecte l’intégralité des zones internes, au moins depuis le Pliocène inférieur. La zone des flyschs se surélève à plus grande vitesse

Refined Tectonic Evolution of the Betic-Rif Orogen Through Integrated 3-D Microstructural Analysis and Sm-Nd Dating of Garnet Porphyroblasts

Acknowledgments The authors would like to thank Ángel Perandrés-Villegas for preparing the thin sections used for this study, Fátima Linares Ordóñez for X-ray computed micro-tomography scanning, Mike Tappa for assistance with thermal ionization mass spectrometry analysis, Francisco Alonso-Chaves and Fernando Simancas for sending structural data, Whitney Behr, Johannes Glodny, Sean Mulcahy, and an anonymous reviewer for providing helpful reports, and editors Laurent Jolivet and Federico Rossetti for additional comments that helped improve two earlier manuscript versions. EFB gratefully acknowledges support from the NSF Grants EAR-1250497 and PIRE-1545903 as well as start up funds from the Boston College. DA and ARF gratefully acknowledge financial support through Spanish project “DAMAGE” (CGL2016-80687-R AEI/FEDER), and Junta de Andalucía project RNM148, both directed by Jesús Galindo Zaldivar. ARF acknowledges an PhD Grant (FPU) from the Spanish government. Open access fees have been funded by Universidad de Granada /CBUA.High-resolution microstructural analysis of porphyroblast inclusion trails integrated with Sm-Nd garnet geochronology has provided new insight into the tectonic history of the Betic-Rif orogen. Three principal age groups of porphyroblasts are demonstrated with distinctly oriented inclusion-trails. Inclusion-trail curvature axes or “FIA” (Foliation Inflexion/Intersection Axes) are shown to represent “fossilized” crenulation axes from which a succession of different crustal shortening directions can be deduced. The regional consistency of microstructural orientations and their geometric relationship with multiple sets of macroscopic folds reveal the composite character of the Gibraltar Arc formed by a superposition of different folding directions and associated lineations. Bulk-garnet ages of 35–22 Ma obtained from five micaschist samples of the Alpujarride-Sebtide complex (ASC) and of 35–13 Ma from four micaschists of the Nevado-Filabride complex (NFC) allow to deduce NNE-SSW directed shortening in the Late Eocene changing to NW-SE shortening in the early Oligocene, alternating with suborthogonal NE-SW shortening during the Miocene. These directions can be related to a major swing in the direction of relative Africa-Iberia plate-motion known from kinematic modeling of magnetic seafloor anomalies, and subsequent dynamic interference between plate convergence and suborthogonal “tectonic escape” of the Alboran Domain. Coupled to previously established P-T-t paths, the new garnet ages support a common tectono-metamorphic evolution of the ASC and NFC as laterally equivalent orogenic domains until, in the Miocene, the second became re-buried under the first.NSF Grant EAR-1250497PIRE-1545903Spanish project “DAMAGE” (CGL2016-80687-R AEI/FEDER)Junta de Andalucía project RNM148PhD Grant (FPU) from the Spanish governmentOpen access fees have been funded by Universidad de Granada /CBU

Strike-slip faults in the south Haouz (Calcareous Dorsal, Internal Rif, N of Tetouan, Maroc). Comparison with the Betics (Spain)

4 páginas, 4 figuras.-- Trabajo presentado en la 41ª Sesión Científica, Barcelona, 2006.Different sets of strike-slip faults of the Haouz Mountains (from Tetouan to the strait of Gibraltar) deform the tectonic slices of the Calcareous Dorsal there present. In this paper we study those faults at the southern part of the Haouz. Three fault formation stages can be distinguished and correspond to the progressive s1 rotation during the Neogene from a near E-W position to approximately N-S, in a progressive anticlockwise rotation. The faults and other related structures are compared with similar ones existing in the Betic Cordillera, in equivalent areas of the arc of Gibraltar.Este artículo es una contribución del grupo de Travaux de Recherches de l’Unité Risques Géologiques et Télédetection, 2006, Rabat y de los proyectos BTE2001-5230-E, CGL200401636/BTE, CGL2004-03333/ BTE, y el grupo RNM 217 de la Junta de Andalucía.Peer reviewe