Initial Pangean rifting north of the West African Craton: Insights from late Permian U-Pb and 40Ar/39Ar dating of alkaline magmatism from the Eastern Anti-Atlas (Morocco)

Najih, Amine; Montero, P.; Vérati, Chrystèle; Chabou, Moulley Charaf; Fekkak, Abdelilah; Baïdder, Lahssen; Ezzouhairi, Hassan; Беа, Ф.; Michard, André

doi:10.1016/j.jog.2019.101670

Cited by 20 publications

(10 citation statements)

References 86 publications

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“…Nd isotopic data from the same Triassic dykes yielded model ages of 0.6-0.8 Ga consistent with Pan-African/Cadomian magmatism. This Triassic magmatism correlates with other late Permian (264-255 Ma) lamprophyres dykes, dolerites, and gabbros documented in the Tafilalt basin of the Anti-Atlas sourced from a deep metasomatized mantle that heralds the CAMP event(Najih et al, 2019).The northern margin of the Anti-Atlas was reactivated during the Atlantic and Tethys rifting, as recorded in the High and Middle Atlas rift systems in the Late Permian-early Triassic to the early Jurassic(Lamotte et al, 2008). Rifting was accompanied by widespread lava flows, sills and dykes of the CAMP (201 Ma), encompassing the Anti-Atlas, Central and High Atlas, and Western and Eastern Meseta(Marzoli et al, 2019) (Figure8).…”

supporting

confidence: 71%

Cenozoic mountain building and topographic evolution in Western Europe: impact of billions of years of lithosphere evolution and plate kinematics

Mouthereau¹,

Angrand²,

Jourdon³

et al. 2021

BSGF - Earth Sci. Bull.

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The architecture and nature of the continental lithosphere result from billions of years of tectonic and magmatic evolution. Continental deformation over broad regions form collisional orogens which evolution is controlled by the interactions between properties inherited from hits long-lasting evolution and plate kinematics. The analysis of present-day kinematic patterns and geophysical imaging of lithosphere structure can provide clues on these interactions. However how these interactions are connected through time and space to control topographic evolution in collision zones is unknown. Here we explore the case of the Cenozoic mountain building and topographic evolution of Western Europe. We first review the tectono-magmatic evolution of the lithosphere of Europe based on the exploitation of geological, geochronological and geochemical constraints from ophiolites, mafic rocks and xenoliths data. Combined with the analyses of low-temperature thermochronological and plate kinematic constraints we discuss the key controlling parameters of the topography. We show that among the required ingredients is the primary effect of plume-, rift- and subduction-related metasomatic events on lithosphere composition. Those main events occurred during the Neoproterozoic (750-500 Ma) and the late Carboniferous-Permian (310-270 Ma). They resulted in the thinning and weakening of the sub-continental lithospheric mantle of Europe. Contrasting lithosphere strengths and plate-mantle coupling in Western Europe with respect to the cratonic lithosphere of West Africa Craton and Baltica is the first-order parameter that explain the observed strain and stress patterns. Subsequent magmatic and thinning episodes, including those evidenced by the opening of the early Jurassic Alpine Tethys and the CAMP event, followed by late Jurassic and early Cretaceous crustal thinning, prevented thermal relaxation of the lithosphere and allowed further weakening of the European lithosphere. The spatial and temporal evolution of topographic growth resolved by the episodes of increased exhumation show two main periods of mountain building. During the late Cretaceous-early Cenozoic (80-50 Ma) contractional deformation was distributed from North Africa to Europe, but the topographic response to the onset of Africa-Eurasia convergence is detected only in central Europe. The lack of rapid exhumation signal in southern Europe and north Africa reveal that the initial continental accretion in these regions was accommodated under water in domains characterized by thin continental or oceanic crust. The second phase of orogenic uplift period starts at about 50 Ma between the High Atlas and the Pyrenees. This second key period reflects the time delay required for the wider rift systems positioned between Africa and Europe to close, likely promoted by the acceleration of convergence. Tectonic regime then became extensional in northern Europe as West European Rift (WER) opened. This event heralds the opening of the Western Mediterranean between Adria and Iberia at ca. 35 Ma. While mature orogenic systems developed over Iberia at this time, the eastern domain around northern Adria (Alps) was still to be fully closed. This kinematic and mechanical conditions triggered the initiation of backarc extension, slab retreat and delamination in the absence of strong slab pull forces. From about 20 Ma, the high temperature in the shallow asthenosphere and magmatism trapped in the mantle lithosphere contributed to topographic uplift. The first period (80-20 Ma) reveals spatially variable onset of uplift in Europe that are arguably controlled by inherited crustal architecture, superimposed on the effect of large-scale lithospheric properties. The second period marks a profound dynamic change, as sub-lithospheric processes became the main drivers. The channelized mantle flow from beneath Morocco to Central Europe builds the most recent topography. In this study, we have resolved when, where and how inheritance at lithospheric and crustal levels rule mountain building processes. More studies focus on the tectonic-magmatic evolution of the continental lithosphere are needed. We argue that when they are combined with plate reconstructions and thermochronological constraints the relative impact of inheritance and plate convergence on the orogenic evolution can be resolved.

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supporting

confidence: 71%

Cenozoic mountain building and topographic evolution in Western Europe: impact of billions of years of lithosphere evolution and plate kinematics

Mouthereau¹,

Angrand²,

Jourdon³

et al. 2021

BSGF - Earth Sci. Bull.

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“…In addition, the primary mineralogical paragenesis contains plagioclase feldspar, alkali feldspar, brown hornblende, biotite and apatite. Our petrographic study of the samples collected from the dykes shows the presence of ferromagnetic (hematite and other iron oxides), The magmatic age of different outcrops of magmatic bodies in Tafilalet region is very difficult to resolve, because the field works combined with ASM data for the dykes of the TTR site (in this paper) are disaccords with the geochronological study in Jbel Dboa site; located at 14 km NE of the study area (Najih et al, 2019). This recent dating yields an age ranged between 255 ± 3Ma and 264.2 ± 2.7Ma using the biotite 40 Ar/ 39 Ar and zircon U-Pb dating (Najih et al, 2019).…”

Section: Discussionmentioning

confidence: 84%

“…Based on these works, the magmatic rocks of Tafilalet province have a sodic alkaline magma composition and intruded during the Famennian-Tournaisian and the early Visean (Álvaro et al, 2014b, 2014c, Pouclet et al, 2017. In the same way, Najih et al, (2018Najih et al, ( , 2019 confirm the geochemical affinity of these magmatic rocks, they attribute them a post-Visean and pre-Triassic age, precisely the late Permian (between 255 ± 3Ma and 264.2 ± 2.7Ma) using the biotite 40 Ar/ 39 Ar and zircon U-Pb dating. The samples were collected in the Jbel Dboa laccolith in the core of the M'Fis anticline located at 14 km NE of the TTR anticline.…”

Section: Geological Settingmentioning

confidence: 93%

“…This national program produced several 1/50.000 scale geological maps, like Irara, Marzouga, M'Fis, Taouz and El Atrous (Álvaro et al, 2014a(Álvaro et al, , 2014b(Álvaro et al, , Benharref et al, 2014b(Álvaro et al, , 2014a(Álvaro et al, , 2014c. Also, some magmatic studies were recently performed in Tafilalet region, like publications of Pouclet et al, (2017Pouclet et al, ( , 2018 and Najih et al, (2018Najih et al, ( , 2019.…”

Section: Introductionmentioning

confidence: 99%

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Petrographic and Magnetic Fabric Investigation of the Tadaout-Tizi n'Rsas Dyke Swarms in the Eastern Anti-Atlas, Morocco

Daoud

Essalhi

et al. 2021

Econ. Environ. Geol.

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Located in the eastern part of the Anti-Atlas, the Tafilalet region shows numerous dykes and sills that crosscut the Paleozoic terrains. The magmatic structures (dykes and sills) of the Tadaout-Tizi n'Rsas (TTR) anticline is studied here, it located neighboring the main branch of the Anti-Atlas Major Fault (AAMF), known in this location as the Oumejrane-Taouz Fault (OJTF). The N20° to N60°t rending dykes crosscut the Paleozoic formations (Ordovician to Devonian), whereas sills are injected into the Silurian and Devonian ones. The dyke swarms of TTR have been studied using the Anisotropy of Magnetic Susceptibility (AMS), petrographic study and structural analyses. The petrographic study of the TTR doleritic dykes shows a dominance of plagioclase feldspars, alkali feldspars, amphiboles, pyroxenes and biotite. The dykes contain also mesotype (natrolite), sphene (titanite), apatite, actinolite and pegmatitic enclaves of biotite, orthoclase feldspars and pelites. Concerning field works, they show the deformation of TTR dykes by the Variscan tectonics events, it is marked by the presence of displacements (strike-slip faults) and cleavages. The Magnetic Susceptibility (MS) measured on magmatic specimens show the dominance of ferromagnetic and paramagnetic minerals. The high values of MS in the dykes are due to the presence of hematite, amphibole, pyroxene and biotite. In addition their magnetic fabric, determined by our AMS study, allows us to reconstitute the tectonic event which affected the magmatic bodies. This one is characterized by a magnetic foliation and a NNW-trending lineation that reflect the Variscan shortening orientation.

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“…14), is likely. We assume that the Alpujarrides-Sebtides crustal units were progressively exhumed during the Early Permian collapse of the Variscan belt (Rossetti et al, 2020) and the Late Permian initial rifting of Pangea (Najih et al, 2019), prior to the onset of Middle Triassic sedimentation. Then rifting proceeded up to the Early-Middle Jurassic, as indicated by neptunian dykes in the Dorsale and neighboring Malaguide-Ghomaride domains (El Kadiri et al, 1992;El Kadiri, 2000-2002b, which are coeval with those described in the northern Sila massif of Calabria (Bouillin and Bellomo, 1990).…”

Section: Restoring the Alpujarrides-sebtides-dorsale Paleomarginmentioning

confidence: 99%

The Beni Bousera marbles, record of a Triassic-Early Jurassic hyperextended margin in the Alpujarrides-Sebtides units (Rif belt, Morocco)

Farah

Michard

Saddiqi

et al. 2021

BSGF - Earth Sci. Bull.

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The timing and process of exhumation of the subcontinental peridotites of the Gibraltar Arc (Ronda, Beni Bousera) have been repeatedly discussed in the last decades. Here we report on high-grade marbles that crop out around the central and southeastern parts of the Beni Bousera antiform of northern Rif. Instead of being mere intercalations in the granulitic envelope (kinzigites) of the peridotites, as currently admitted, they are localized between the kinzigites and the gneisses of the overlying Filali Unit. The marbles occur in the form of minor, dismembered units in a ~30 to 300 m-thick Filali-Beni Bousera ductile shear zone (FBBSZ). They display silicate-rich dolomitic marbles, sandy-conglomeratic calcareous marbles and thinly bedded marble with interleaved phyllites, which demonstrates their sedimentary origin. A stratigraphic or tectonic unconformable contact onto the kinzigites can be locally observed. Pebbles or detrital grains include K-feldspar, quartz, and zircon. Prograde metamorphic minerals are forsterite, Mg-Al-spinel, geikielite, phlogopite, scapolite, diopside, and titanite, which characterize a peak HT-LP metamorphism close to 700-750°C, 4-7 kbar, comparable to that of the overlying Filali gneisses and of the late migmatitic stage of the kinzigites. Second-order structures within the FBBSZ are northwestward ductile thrusts, which determine kinzigite horses thrust over the marbles. Within the latter, NNE-trending folds are conspicuous. The mylonitic structures are crosscut by late, northward dipping normal faults. Varied correlations with comparable settings in the other West Mediterranean Alpine belts are discussed. We propose to correlate the Beni Bousera marbles with the Triassic carbonates deposited over the crustal units of the Alpujarrides-Sebtides. The Triassic protoliths may have been deposited onto the kinzigites or carried as allochthons over a detachment during the Early Jurassic in the frame of the hyper-extension of the Alboran Domain continental crust, as observed in the Adria and Europe inverted margins of the Western Alps. In either of these hypotheses, the currently prevailing paradigm of “hot” exhumation of the Rif–Betic peridotites during the Alpine orogeny would be reconsidered.

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Initial Pangean rifting north of the West African Craton: Insights from late Permian U-Pb and 40Ar/39Ar dating of alkaline magmatism from the Eastern Anti-Atlas (Morocco)

Cited by 20 publications

References 86 publications

Cenozoic mountain building and topographic evolution in Western Europe: impact of billions of years of lithosphere evolution and plate kinematics

Cenozoic mountain building and topographic evolution in Western Europe: impact of billions of years of lithosphere evolution and plate kinematics

Petrographic and Magnetic Fabric Investigation of the Tadaout-Tizi n'Rsas Dyke Swarms in the Eastern Anti-Atlas, Morocco

The Beni Bousera marbles, record of a Triassic-Early Jurassic hyperextended margin in the Alpujarrides-Sebtides units (Rif belt, Morocco)

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