Crystalline Basement of the West African Craton

Rocci, G.; Bronner, Georges; Deschamps, Marc

doi:10.1007/978-3-642-84153-8_3

Cited by 63 publications

(47 citation statements)

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“…In a previous review of the district, Rocci et al (1991) concluded that the from 3.25 to 2.9 Ga, the latter yielded by the youngest dated granite.…”

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U–Pb dating and Sm–Nd isotopic analysis of granitic rocks from the Tiris Complex: New constaints on key events in the evolution of the Reguibat Shield, Mauritania

Schofield

Horstwood

Pitfield

et al. 2012

Precambrian Research

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New U-Pb geochronology indicates that the main intrusive events, broadly 27 associated with formation of dome-shaped structures, occurred at around 2.95 to 2.87 28 Ga and 2.69 to 2.65 Ga. This study also recognises younger regional metamorphism largely Palaeoproterozoic granitic and volcano-sedimentary rocks (Bessoles, 1977; 46 Dillon & Sougy, 1974). In Mauritania, these crustal domains were juxtaposed during 47 the, c. 2.10-2.00 Ga, Eburnean Orogeny (Schofield et al., 2006). et al., 1992; Potrel, 1994; Potrel et al., 1996) 104 including orthogneiss dated by the U-Pb method at 3515 ± 15 Ma and 3422 ± 10 Ma 105( Potrel et al., 1996). Incorporation of an even older crustal component is suggested by 106Nd T DM ages of around 3.60 Ga (Potrel et al., 1996). A subsequent event has been 107 proposed based on U-Pb dating of charnokite at 2986 ± 8 Ma (Potrel et al., 1998 to 3.1 Ga (Potrel, 1994; Potrel et al., 1996;1998 The Amsaga Complex is juxtaposed against the Tiris Complex along a broad 122 belt of aluminous gneisses (Bronner, 1977;Rocci et al., 1991; O'Connor et al., 2005). 123To the northeast, these pass into an extensive complex dominated by foliated and planar fabrics (Fig. 4c). These are unaffected by earlier fold phases and are interpreted 269 as recording the youngest deformation episode episode in this part of the study area. 270The northern margin of this domain is defined by the El M'dena Fault Zone (Fig. 2 This sample was collected from the Mirikli Formation within the high strain looking crystals, suggesting a lower uranium concentration than the first population. 360Of twenty-seven zircon analyses from this second population six provided near 361 concordant data. The age spread suggests crystallization of the granite at 2487 ± 8 Ma 362(2σ, Fig. 8d) with inheritance at c.2550 and 2700 Ma (Fig. 8d). This sample yielded 363 an ε Nd value of -5.7 at t = 2487 Ma and T DM 3.14 Ga. good quality titanite and allanite (Fig. 7e) and good quality bipyrimidal and elongate 372 zircons (Fig. 7f). Thirty one analyses from twenty two zircons were performed on this 373 sample. Four analyses were excluded from a calculation giving a Concordia age of 374 2472 ± 6 Ma (2σ, Fig. 8e). This is interpreted to represent the crystallization age of 375 the rock. This sample yielded an ε Nd value of -2.1 at t = 2472 Ma and T DM 2.9 Ga. Geological development of the Tiris Complex 388The oldest rocks preserved in the Tiris Complex, pre-dating the main phase of 389 granite magmatism at around 2.95 Ga, comprise metasedimentary ferruginous 390 quartzite and aluminous and hypersthene-bearing paragneiss of the Mirikli Formation. 391These may be equivalent to similar assemblages preserved in the El Khadra and el 392Geicha formations. The presence of bands and pods of metamafite intercalated with 393 the metasedimentary host indicate that there was also an early phase of mafic dyke 394 emplacement, although the age of this also remains unconstrained. 395Early tectonism, also pre-dating the main intrusive episode, is recorded by 396...

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“…In a previous review of the district, Rocci et al (1991) concluded that the from 3.25 to 2.9 Ga, the latter yielded by the youngest dated granite.…”

mentioning

confidence: 99%

“…A subsequent event has been 107 proposed based on U-Pb dating of charnokite at 2986 ± 8 Ma (Potrel et al, 1998 to 3.1 Ga (Potrel, 1994; Potrel et al, 1996;1998 The Amsaga Complex is juxtaposed against the Tiris Complex along a broad 122 belt of aluminous gneisses (Bronner, 1977;Rocci et al, 1991; O'Connor et al, 2005).…”

mentioning

confidence: 99%

U–Pb dating and Sm–Nd isotopic analysis of granitic rocks from the Tiris Complex: New constaints on key events in the evolution of the Reguibat Shield, Mauritania

Schofield

Horstwood

Pitfield

et al. 2012

Precambrian Research

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“…Considering the recently recorded 2600 Ma ages [4,14,18], it is possible that these ancient granites are of Archean origin. The second generations are nonfoliated and crosscut young granites, sometimes very potassic in composition [2].…”

Section: The Stable Zonementioning

confidence: 99%

“…The supracrustal belts include a lower assemblage, the Birimian unit, and an upper assemblage, the Tarkwaian unit [2,14,15]. The lower assemblage includes the Lower Birimian unit, made up of metapelites associated with metamorphic rocks of various origins (greywackes, sandstones, arkoses, volcanic tuffs, siltites , volcanites, and pyroclastites); the Upper Birimian Unit is composed mainly of magmatic rocks (basic to intermediate lavas associated with pyroclastites, agglomerates, volcanic tuffs, and arkosic intercalations).…”

Section: The Stable Zonementioning

confidence: 99%

“…It includes three distinct structural domains [1][2][3][4][5] (1) the southeastern margin of the West african craton (WAC) consisting of Archean to Paleoproterozoic assemblages that underwent the Eburnean Orogeny (2000 ± 200 Ma); (2) the Neoproterozoic Volta Basin represented by its lower and middle megasequences (Bombouaka and Oti Supergroups); (3) the frontal structural units of the Pan-African Dahomeyide Orogenic Belt (600 ± 50 Ma).…”

Section: Introductionmentioning

confidence: 99%

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Pan-African Paleostresses and Reactivation of the Eburnean Basement Complex in Southeast Ghana (West Africa)

Tairou

Affaton

Anum

et al. 2012

Journal of Geological Research

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This faulting tectonics analysis concerns the southernmost segment of the Dahomeyide Orogen and the West-African craton eastern margin in southeast Ghana. The analysis of strike-slip faults in the frontal units of the Dahomeyide Belt indicates that four distinct compressive events (NE-SW, ENE-WSW to E-W, ESE-WNW to SE-NW and SE-NW to SSE-NNW) originated the juxtaposition of the Pan-African Mobile Zone and the West-African craton. These paleostress systems define a clockwise rotation of the compressional axis during the structuring of the Dahomeyide Orogen (650-550 Ma). The SE-NW and SSE-NNW to N-S compressional axes in the cratonic domain and its cover (Volta Basin) suggest that the reactivation of the eastern edge of the West African craton is coeval with the last stages of the Pan-African tectogenesis in southeast Ghana. An extensional episode expressed as late normal faulting is also recorded in this study. This E-W to SE-NW extension, which is particular to the southernmost part of the Dahomeyide Belt, appears to be post-Pan-African. This extension probably contributed to the formation of a major Jurassic rifting zone that originated the Central Atlantic and the Benue Trough.

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Algeria

Geological Atlas of Africa

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Crystalline Basement of the West African Craton

Cited by 63 publications

References 30 publications

U–Pb dating and Sm–Nd isotopic analysis of granitic rocks from the Tiris Complex: New constaints on key events in the evolution of the Reguibat Shield, Mauritania

U–Pb dating and Sm–Nd isotopic analysis of granitic rocks from the Tiris Complex: New constaints on key events in the evolution of the Reguibat Shield, Mauritania

Pan-African Paleostresses and Reactivation of the Eburnean Basement Complex in Southeast Ghana (West Africa)

Algeria

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