Cisaillement ductile et granitoides syntectoniques; l'exemple du Massif Hercynien des Jebilet (Maroc)

Lagarde, Jean‐Louis; Cartigny, Pierre

doi:10.2113/gssgfbull.s7-xxiv.2.299

Cited by 52 publications

(37 citation statements)

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“…The Jebilet massif consists of three lithotectonic domains, the Western, Central, and Eastern Domains (Fig. 1b), which are separated by major shear zones ( [Huvelin, 1977] and [Lagarde and Choukroune, 1982]). The Western Domain consists of Cambrian and Ordovician rocks, whereas the Central domain consists of metamorphosed and deformed upper Visean (350 to 340 Ma) rocks.…”

Section: Geological Frameworkmentioning

confidence: 99%

Draa Sfar, Morocco: A Visean (331 Ma) pyrrhotite-rich, polymetallic volcanogenic massive sulphide deposit in a Hercynian sediment-dominant terrane

Marcoux

Belkabir²,

Gibson

et al. 2008

Ore Geology Reviews

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Draa Sfar is a Visean, stratabound, volcanogenic massive sulphide ore deposit hosted by a Hercynian carbonaceous, black shale-rich succession of the Jebilet terrane, Morocco. The ore deposit contains 10 Mt grading 5.3 wt.% Zn, 2 wt.% Pb, and 0.3 wt.% Cu within two main massive sulphides orebodies, Tazakourt (Zn-rich) and Sidi M'Barek (Zn-Cu rich). Pyrrhotite is by far the dominant sulphide (70 to 95% of total sulphides), sphalerite is fairly abundant, chalcopyrite and galena are accessory, pyrite, arsenopyrite and bismuth minerals are rare. Pyrrhotite is monoclinic and mineralogical criteria indicate that it is of primary origin and not formed during metamorphism. Its composition is very homogeneous, close to Fe 7 S 8 , and its absolute magnetic susceptibility is 2.10 − 3 SI/g. Ar-Ar dating of hydrothermal sericites from a coherent rhyolite flow or dome within the immediate deposit footwall indicates an age of 331.7 ± 7.9 Ma for the Draa Sfar deposit and rhyolite volcanism.The Draa Sfar deposit has undergone a low-grade regional metamorphic event that caused pervasive recrystallization, followed by a ductile-brittle deformation event that has locally imparted a mylonitic texture to the sulphides and, in part, is responsible for the elongated and sheet-like morphology of the sulphide orebodies. Lead isotope data fall into two compositional end-members. The least radiogenic end-member, ( 206 Pb/ 204 Pb = 18.28), is characteristic of the Tazakourt orebody, whereas the more radiogenic end-member ( 206 Pb/ 204 Pb 18.80) is associated with the Sidi M'Barek orebody, giving a mixing trend between the two end-members. Lead isotope compositions at Draa Sfar testify to a significant continental crust source for the base metals, but are different than those of the Hajar and South Iberian Pyrite Belt VMS deposits.The abundance of pyrrhotite versus pyrite in the orebodies is attributed to low fO 2 conditions and neither a high temperature nor a low aH 2 S (below 10 − 3 ) is required. The highly anoxic conditions required to stabilize pyrrhotite over pyrite are consistent with formation of the deposit within a restricted, sediment-starved, anoxic basin characterized by the deposition of carbonaceous, pelagic sediments along the flank of a rhyolitic flow-dome complex that was buried by pelitic sediments. Deposition of sulphides likely occurred at and below the seafloor within anoxic and carbonaceous muds. Draa Sfar and other Moroccan volcanogenic massive sulphide deposits occur in an epicontinental volcanic domain within the outer zone of the Hercynian belt and formed within a sedimentary environment that has a high pelagic component. In spite of the diachronous emplacement between the IPB deposits (late Devonian to Visean) and Moroccan deposits (Dinantian), all were formed around 340 ± 10 Ma following a major phase of the Devonian compression.

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Section: Geological Frameworkmentioning

confidence: 99%

Draa Sfar, Morocco: A Visean (331 Ma) pyrrhotite-rich, polymetallic volcanogenic massive sulphide deposit in a Hercynian sediment-dominant terrane

Marcoux

Belkabir²,

Gibson

et al. 2008

Ore Geology Reviews

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“…1c). Dans sa partie centrale sont juxtaposées deux formations attribuées au Viséen supérieur (Huvelin, 1977), séparées par le cisaillement ductile sénestre Sidi Bou Othmane (Lagarde & Choukroune, 1982): les Flyschs de Hoepffner et al, 2005), 1: unités allochtones des Mauritanides, 2: Craton ouest Africain, 3: Terrains paléozoïques, a: déformés par l'orogenèse varisque, b: non déformés, 4: chaîne atlasique (AH: Haut Atlas, AM: Moyen Atlas), 5: Chaîne Rifo-Tellienne (Maghrébides), a: front sud de la chaîne, b: terrains paléozoïques allochtones des zones internes. (b) les zones structurales de la chaîne varisque du Maroc (d'après, Hoepffner et al, 2005), 1: a: zone des Sehoul, b: son prolongement probable vers l'ouest, 2: Bloc côtier, 3: Zone centrale avec a: sous-zone occidentale et b: sous-zone orientale, 5: zone sud, 6: zones internes du Rif.…”

Section: Les Jebilet Orientalesunclassified

Tectono-Sedimentary and magmatic evolution of the Upper Visean basins of Azrou-Khénifra and eastern Jebilet (Moroccan Meseta)

Bamoumen¹,

Aarab²,

Soulaı̈mani³

2008

Estud. geol.

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During Upper Visean times, the eastern mesetian basins of eastern Jebilet and Azrou Khenifra show great tectono-sedimentary and magmatic evolution similarities. Their deposits record large instabilities and disorganization with huge thickness and lithological variations, related to a synsedimentary tectonic context. At the same time, tilted block tectonics affect the basement of these basins, controlled by bordering transfert faults. Basic dominant magmatic bodies set up in these basins. Their continental alkaline chemical characteristics are consistent with the regional geodynamic context in this area. Initiated along the transitional zone between eastern and western Meseta, the Azrou-Khenifra and Jebilet basins correspond to intracontinental throws, initiated on and controlled by major strike-slip faults. Their evolution is most likely earlier in time and of a weak opening rate than the neighboring western Meseta basins.

Au Viséen supérieur, les bassins mesetiens des Jebilet orientales et dâ€™Azrou Khénifra montrent de grandes similitudes de leur évolution tectono-sédimentaire et magmatiques. Leurs dépôts enregistrent de grandes instabilités liées à une tectonique syn-sédimentaire responsable localement dâ€™une intense désorganisation et de grandes variations de faciès et dâ€™épaisseurs. Ces instabilités sont engendrées par une tectonique en blocs basculés qui affecte le substratum anté-Viséen, contrôlée par des accidents bordiers sub-verticaux à forte composante transcurrente. Des corps magmatiques, pour lâ€™essentiel basiques, se mettent en place dans ces bassins. Ils présentent des caractères chimiques des séries magmatiques alcalines mise en place dans un contexte intracontinental et anorogénique. Initiés le long de la zone de transition entre la Meseta orientale et occidentale, les bassins dâ€™Azrou-Khénifra et des Jebilet orientales correspondent à des sillons intracontinentaux, initiés et contrôlés par des décrochements. Leur évolution est sans doute plus précoce et montre un faible taux dâ€™ouverture que celui enregistré dans les bassins adjacents de la meseta occidentale

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“…Mis à part les noyaux paleozoïques allochtones du Rif, la chaîne hercynienne est constituée, au dessus (Michard, 1976;Lagarde et Choukroune, 1982;Lagarde, 1985;Lagarde et Michard, 1986).…”

Section: Les Caractéristiques Majeures De L'évolution Géologique Variunclassified

“…Parmi les études radiochronologiques effectuées sur le granite, soit par la méthode K^/Ar 39 (Choubert et al, 1965), soit par Rb/Sr (Tisserand, 1977;Mrini, 1985), on retient la période de 280 -300 Ma considérée comme celle de la mise en place du granite d'Oulmès (Mrini, 1985 (Piqué, 1976;Dahmani, 1985) a été discuté par Ait Omar (1986) et Diot et al (1987) (Brun et Pons, 1981), Sidobre au Sud du massif central français (Âcuana Sorriaux, 1981), de Bretagne centrale (Hanmer et Vîgneresse, 1980), ou à ses congénères de la Meseta marocaine dont, celui des Jebilet au Sud (Lagarde et Choukroune, 1982) et celui de Tichka dans le Haut -Atlas (Lagarde et Roddaz, 1983). …”

Section: -3-1 Le Massif D'oulmèsunclassified

Developpement des aureoles de contact d oulmes et de ment (Maroc central)

Dahmani¹

1995

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Cisaillement ductile et granitoides syntectoniques; l'exemple du Massif Hercynien des Jebilet (Maroc)

Cited by 52 publications

References 0 publications

Draa Sfar, Morocco: A Visean (331 Ma) pyrrhotite-rich, polymetallic volcanogenic massive sulphide deposit in a Hercynian sediment-dominant terrane

Draa Sfar, Morocco: A Visean (331 Ma) pyrrhotite-rich, polymetallic volcanogenic massive sulphide deposit in a Hercynian sediment-dominant terrane

Tectono-Sedimentary and magmatic evolution of the Upper Visean basins of Azrou-Khénifra and eastern Jebilet (Moroccan Meseta)

Developpement des aureoles de contact d oulmes et de ment (Maroc central)

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