In the eastern sector of the Moroccan Central Hercynian Massif, Ediacaran and Cambrian magmatic rocks outcrop in the anticlines of Jbel Belkheit and Jbel Bou-Acila. These were emplaced between Pan-African deformed-sequences and Lower Palaeozoic levels in two successive volcanic series, separated by confirmed Lower Cambrian limestones: a) a lower series of Ediacaran age composed of felsic and intermediate volcanic rocks (rhyodacites and andesites). The rhyodacites are clearly calc-alkaline in character, comparable to rocks generated in an active margin orogenic context, whereas the andesites are transitional between calc-alkaline and tholeiitic, reflecting a change in the geotectonic context at the end of the Neoproterozoic; and b) an upper series of Cambrian age, composed of anorogenic tholeiitic basalts with massive flows in the bottom and pillow lavas in the top of the sequence. Although structural, petrographic and geochemical data rule out any genetic link between the felsic and the intermediate Ediacaran rocks, a geochemical link between the andesites and Cambrian basalts can be suggested. Both facies are thought to have been generated in an extensional context, although some of the orogenic features of their protolith are still present. In this sense, the Ediacaran andesites would be precursors of the Late Neoproterozoic – Early Cambrian rift rocks, leading to the eventual formation of Cambrian basalts. The latter facies were already emplaced in a clear extensional geodynamic context, and were probably generated by the same source that evolved during progressive crustal extension and thinning. This is confirmed by the evolution of Cambrian basalt morphostructures and geochemical characteristics from: i) massive flow basalts with a geochemical signature of intraplate tholeiites of E-MORB character; to ii) pillow lavas of oceanic tholeiites with a N-MORB character. This transition, therefore, marks the beginning of an oceanization process, which has never been described elsewhere in the Moroccan Cambrian.
In the Moroccan Eastern Meseta, the High Moulouya Batholith (HMB), which spans an area of approximately 2400 km2, is partially hidden by the Meso-Cenozoic cover. The HMB was emplaced in Cambro-Ordovician metasedimentary rocks that had undergone greenschist facies metamorphism (Chl+Mus+Qtz+Pl+Kfs). These hosting rocks were then affected by HT-BP superimposed contact metamorphism linked to HMB emplacement. Four metamorphic zones were identified, delineating four isograds corresponding to four main metamorphic reactions. These zones include the biotite zone, cordierite zone, andalusite zone, and sillimanite zone.  The biotite zone exhibits a mineral assemblage of Bt+Mus+Chl+FK+Qtz (±Pl ± Grt), marking the introduction of biotite through the discontinuous monovariant reaction: Chl+Qtz+FK+H2O=Bt+Mus . In the cordierite zone, the composition includes Bt+Mus+Crd+Chl+FK+Qtz (±Pl), and the reaction leading to Crd formation is: Chl+Bt+Mus+Qtz = Crd+FK+H2O. The successive development of aluminum silicates characterizes the andalusite and sillimanite zones, each associated with specific isograds corresponding to the following reactions: (Sill)+Qtz+H2O, Mus+Qtz=FK+And (Sill)+H2O, and/or And=Sill. The obtained results, using pseudosection modelling as well as petrogenetic grid calculations, allow to precise better the HMB emplacement PT conditions. Biotite appears at a temperature of 400°C, cordierite at 500 to 520°C and andalusite at 580 to 600°C. The stability field of the andalusite-sillimanite paragenesis allows constrains the pressure at 2.6 to 2.9 Kb, which is considered constant for the entire metamorphic aureole. Therefore, the granitoids of the HMB were emplaced at a depth of 8.5 to 9.5 km, developing a contact aureole for temperatures ranging from 400 to 625°C. Moreover, 2D gravity modelling revealed that the HMB has a laccolithic shape with a thickness ranging from 3 to 5 km. The presence of numerous feeders suggests that the emplacement of the HMB occurred through a dyking process.
L'etude des leucogranites peralumineux des Massifs de Brezouard et de Bilstein (Vosges moyennes) a pour objectif une cartographie detaillee, une caracterisation petrographique, mineralogique et geochimique des differents facies (leucogranite A 2 micas, leucogranite a cordierite, filon microgranitique, rhyolite a cordierite) et de definir les modalites d'evolution ainsi que leurs relations spatiales et genetiques. Pour le massif de Brezouard, une mise en place biphasee avec une deformation peripherique en partie subsynchrone obliteree ulterieurement par une autre cataclastique de basse temperature est mise en evidence. Le massif de Bilstein correspond a une structure independante et aurait subi une orthogneissification en relation avec le fonctionnement ductile d'une zone de cisaillement destre
Morocco has an important geothermal potential materialized by its several thermal springs which constitute an essential surface geothermal indicator. These springs are dispersed throughout the country and present in every major structural domain. However, a significant amount is concentrated in the northern and northeastern areas. Associated with the great hydrothermal system of eastern Morocco, the thermal spring of Goutitir emerges in the Meso-Cenozoic sedimentary formations located east of the Guercif Basin, composed of a mixture of clays, carbonates, and marls, covered in unconformity by Quaternary tabular molasses. The upflow of the thermal water is dependent of Alpine faults systems with N30 and N100 directions, which are probable reactivated Hercynian structures that facilitate its circulation to the surface. The Goutitir spring has been studied by an interdisciplinary approach to identify the origin of the thermal water, the rock–water interactions, and the reservoir temperatures, contributing to the establishment of the conceptual model of the associated hydrothermal system. This thermal water is of chloride-sodium type with a hyperthermal character (43–47 °C). The isotopic composition (δ18O = −8.7 to −8.35‰; δ2H = −58.6 to −54.3‰) indicates a meteoric origin and a recharging zone located at around 2000 m of altitude. The chemical composition allows to classify the water as chloride-sodium hydrochemical facies, stabilized at ~100 °C in crystalline basement rocks, which, according to seismic data, are located at ~3 km depth. The concentrations, patterns, and correlations of trace elements point out water–rock interaction processes between the deep water and basic magmatic rocks. The integration of the chemical and isotopic data and the surface geological context shows that the Goutitir water flows within a hydrothermal zone were basic to ultrabasic lamprophyres rich in gabbroic xenoliths outcrop, witnessing the existence, at depth, of basic plutons. Moreover, near the source, these veins are strongly altered and hydrothermalized, showing late recrystallization of centimetric-sized biotites. The chloride-sodium composition of this water may also be a testimony to the presence and reaction with the overlying Triassic saline and gypsiferous and Meso-Cenozoic mainly carbonated formations.
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