Phases tectoniques superposées dans les métasédiments Précambriens du domaine côtier occidental de la Cote d'Ivoire

Bard, J. P.; Lemoine, Serge

doi:10.1016/0301-9268(76)90009-7

Cited by 16 publications

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“…However, he considers them as two distinct phases D2 and D3 deformation. This tectonics differs from that described by Bard & Lemoine (1976) at Monogaga and Kounoukou, which indicates a superposition of four folding phases. The D3 phase of brittle deformation corroborates the assertions of Vidal & Alric, (1994) according to which the last tectonic events to have marked the Birimian are post-Birimian movements such as the N130˚ fractures.…”

Section: Discussioncontrasting

confidence: 65%

“…These results corroborate those of Kouadio et al (2016) and Kouadio (2017) who identified paragneisses in the sector of Grand-Béré by using a petrographic and geochemical approach. These paragneisses are characterized by an absence of muscovite, unlike those identified by Bard & Lemoine (1976), which contain muscovite and staurotide in addition to garnet and biotite (Koffi et al, 2018). In addition, the paragneisses in our study area present a migmatitic character due to the onset of anatexis.…”

Section: Discussionmentioning

confidence: 99%

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Petro-Structural Study of Paragneiss in the SASCA Domain (Gbowé Sector at Grand-Béréby), Southwestern Côte d’Ivoire

Kouadio¹,

Sangaré²,

Houssou³

et al. 2020

GEP

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The petrographic and structural study of Gbowé (Grand-Béréby) formations located in the SASCA domain (South-West of Côte d'Ivoire) revealed migmatitic paragneisses. For an in-depth understanding of the petrographic, structural and metamorphic characteristics, six (6) thin sections were made from these paragneisses. These gneisses are characterized by paleosomes and neosomes (leucosome and melanosome), consisting of quartz, garnet, plagioclase, biotite, cordierite, sillimanite, myrmekite and microcline. The mineralogical assemblage thus described indicates a retrograde metamorphism (transition from granulitic facies to amphibolitic facies). The structural and microstructural study identified two types of deformation (ductile and brittle). The ductile deformation is characterized by phases D1 (NE-SW flattening) and D2 (NW-SE flattening), materialized by foliations (N140˚, N050˚), folds (asymmetrical folds, similar folds, concentric folds, ptymatic folds) and boudins. Fracture schistosity and fold fracture schistosity are characteristic of the brittle deformation (phase D3). The microstructural study coupled with the metamorphic study shows that the deformations had an impact on the texture of the minerals (recrystallization and mineral reactions). It also allowed giving the paragenesis of phases D1 and D2. The D1 phase is characterized by gar-net1, biotite1, quartz1, sillimanite1 and cordierite1 and the D2 phase is characterized by garnet1, quartz2, sillimanite2, biotite2, garnet2 and orthose2. These parageneses thus highlighted bear witness to a polydeformation and polymorphism that affects the study area.

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Section: Discussioncontrasting

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Petro-Structural Study of Paragneiss in the SASCA Domain (Gbowé Sector at Grand-Béréby), Southwestern Côte d’Ivoire

Kouadio¹,

Sangaré²,

Houssou³

et al. 2020

GEP

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“…Historically, the high‐grade metamorphic domains were interpreted as the basement below the Birimain volcano‐sedimentary formations. A polycyclic orogenic evolution was suggested based on field relationships reflecting poly‐phased structural‐metamorphic fabrics (Arnould, ; Bard & Lemoine, ; Ledru et al ., ). Following this model, the gneissic basement supposedly pre‐dating the Birimian series underwent high‐grade metamorphism during an early orogenic event (Tempier, ; Lemoine et al ., ; Tshibubudze et al ., ; Hein, ) which is termed ‘Eoeburnean’ (Baratoux et al ., ; De Kock et al ., , ; Perrouty et al ., ).…”

Section: Geological Backgroundmentioning

confidence: 99%

Petrological and geochronological constraints on lower crust exhumation during Paleoproterozoic (Eburnean) orogeny, NW Ghana, West African Craton

Block

Ganne

Baratoux

et al. 2015

Journal Metamorphic Geology

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New petrological and geochronological data are presented on high-grade ortho-and paragneisses from northwestern Ghana, forming part of the Paleoproterozoic (2.25-2.00 Ga) West African Craton. The study area is located in the interference zone between N-S and NE-SW-trending craton-scale shear zones, formed during the Eburnean orogeny (2.15-2.00 Ga). High-grade metamorphic domains are separated from low-grade greenstone belts by high-strain zones, including early thrusts, extensional detachments and late-stage strike-slip shear zones. Paragneisses sporadically preserve high-pressure, low-temperature (HP-LT) relicts, formed at the transition between the blueschist facies and the epidote-amphibolite sub-facies (10.0-14.0 kbar, 520-600°C), and represent a low (~15°C km À1 ) apparent geothermal gradient. Migmatites record metamorphic conditions at the amphibolite-granulite facies transition. They reveal a clockwise pressure-temperature-time (P-T-t) path characterized by melting at pressures over 10.0 kbar, followed by decompression and heating to peak temperatures of 750°C at 5.0-8.0 kbar, which fit a 30°C km À1 apparent geotherm. A regional amphibolite facies metamorphic overprint is recorded by rocks that followed a clockwise P-T-t path, characterized by peak metamorphic conditions of 7.0-10.0 kbar at 550-680°C, which match a 20-25°C km À1 apparent geotherm. These P-T conditions were reached after prograde burial and heating for some rock units, and after decompression and heating for others. The timing of anatexis and of the amphibolite facies metamorphic overprint is constrained by in-situ U-Pb dating of monazite crystallization at 2138 AE 7 and 2130 AE 7 Ma respectively. The new data set challenges the interpretation that metamorphic breaks in the West African Craton are due to diachronous Birimian 'basins' overlying a gneissic basement. It suggests that the lower crust was exhumed along reverse, normal and transcurrent shear zones and juxtaposed against shallow crustal slices during the Eburnean orogeny. The craton in NW Ghana is made of distinct fragments with contrasting tectono-metamorphic histories. The range of metamorphic conditions and the sharp lateral metamorphic gradients are inconsistent with 'hot orogeny' models proposed for many Precambrian provinces. These findings shed new light on the geodynamic setting of craton assembly and stabilization in the Paleoproterozoic. It is suggested that the metamorphic record of the West African Craton is characteristic of Paleoproterozoic plate tectonics and illustrates a transition between Archean and Phanerozoic orogens.

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“…In more details, maximum metamorphic conditions progressively increase locally when approaching some of the pluton massifs and can reach amphibolite facies conditions at the contact with the granite bodies ( Fig. 2b; [Tagini, 1971], [Bard, 1974], [Bard and Lemoine, 1976], [Vidal and Guibert, 1984], [Delor et al, 1992a] and [Delor et al, 1992b]). This metamorphic gradient is characterised by temperature but also pressure increase.…”

Section: Geological Setting Of the South Comoé Domainmentioning

confidence: 99%

Evolution of a Paleoproterozoic “weak type” orogeny in the West African Craton (Ivory Coast)

et al. 2009

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The Paleoproterozoic domain of the Ivory Coast lies in the central part of the West African Craton (WAC) and is mainly constituted by TTG, greenstones, supracrustal rocks and leucogranites. A compilation of metamorphic and radiometric data highlights that: i) metamorphic conditions are rather homogeneous through the domain, without important metamorphic jumps, ii) HP-LT assemblages are absent and iii) important volumes of magmas emplaced during the overall Paleoproterozoic orogeny suggesting the occurrence of longlived rather hot geotherms. Results of the structural analysis, focused on three areas within the Ivory Coast, suggest that the deformation is homogeneous and distributed through the Paleoproterozoic domain. In details, results of this study point out the long-lived character of vertical movements during the Eburnean orogeny with a two folds evolution. The first stage is characterized by the development of "domes and basins" geometries without any boundary tectonic forces and the second stage is marked by coeval diapiric movements and horizontal regional-scale shortening. These features suggest that the crust is affected by vertical movements during the overall orogeny. The Eburnean orogen can then be considered as an example of long-lived Paleoproterozoic "weak-type" orogen.

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Phases tectoniques superposées dans les métasédiments Précambriens du domaine côtier occidental de la Cote d'Ivoire

Cited by 16 publications

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Petro-Structural Study of Paragneiss in the SASCA Domain (Gbowé Sector at Grand-Béréby), Southwestern Côte d’Ivoire

Petro-Structural Study of Paragneiss in the SASCA Domain (Gbowé Sector at Grand-Béréby), Southwestern Côte d’Ivoire

Petrological and geochronological constraints on lower crust exhumation during Paleoproterozoic (Eburnean) orogeny, NW Ghana, West African Craton

Evolution of a Paleoproterozoic “weak type” orogeny in the West African Craton (Ivory Coast)

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Phases tectoniques superposées dans les métasédiments Précambriens du domaine côtier occidental de la Cote d'Ivoire

Cited by 16 publications

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Petro-Structural Study of Paragneiss in the SASCA Domain (Gbow&#233; Sector at Grand-B&#233;r&#233;by), Southwestern C&#244;te d’Ivoire

Petro-Structural Study of Paragneiss in the SASCA Domain (Gbow&#233; Sector at Grand-B&#233;r&#233;by), Southwestern C&#244;te d’Ivoire

Petrological and geochronological constraints on lower crust exhumation during Paleoproterozoic (Eburnean) orogeny, NW Ghana, West African Craton

Evolution of a Paleoproterozoic “weak type” orogeny in the West African Craton (Ivory Coast)

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Petro-Structural Study of Paragneiss in the SASCA Domain (Gbowé Sector at Grand-Béréby), Southwestern Côte d’Ivoire

Petro-Structural Study of Paragneiss in the SASCA Domain (Gbowé Sector at Grand-Béréby), Southwestern Côte d’Ivoire