Geology and Mineral Resources of West Africa

Wright, J. B.

doi:10.1007/978-94-015-3932-6

Cited by 133 publications

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“…These results and the geochemical data reveal the juvenile nature of these rocks reinforcing the interpretation that this region may be part of the Rhyacian juvenile continental magmatic arc, that extends through other parts of São Luís Craton with correspondence in the northeast portion of the Amazonian Craton and in West Africa (Abouchami et al 1990, Boher et al 1992, Wright et al 1995, Hirdes et al 1996.…”

Section: U-pb Geochronologysupporting

confidence: 73%

Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

et al. 2017

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ABSTRACT:The São Luís Cráton comprises an area between northeast Pará state and northwest Maranhão that exposes Paleoproterozoic granitic suites and meta-volcanosedimentary sequences. In the east of this geotectonic unit, about 70 km south of São Luís, there is a portion of the São Luís Craton, represented by the intrusive Rosario Suite (RS). This work is focused on rocks of this suite, including petrographic, lithochemical and geochronological studies to understand the crustal evolution of these granitoid rocks. The rock spectrum varies from tonalitic to granodioritic, quartz dioritic and granitic compositions, and there are partial structural and mineralogical changes related to deformation along transcurrent shear zones. The geochemical studies show granitic metaluminous compositions of the calc-alkaline series with I-type affinity typical of magmatic arc. Rare earth elements show marked fractionation and slight Eu positive or negative anomalies (Eu/Eu* = 0.82 to 1.1). Zircon U-Pb data provided consistent ages of 2165 ± 7 Ma, 2170 ± 7 Ma, 2170 ± 7 Ma, 2161 ± 4 Ma and 2175 ± 8 Ma, dating emplacement of these granitoids as Paleoproterozoic (Rhyacian). Sm-Nd isotopic data provided model ages (T DM ) of 2.21 to 2.31 Ga with positive values of εNd +1.9 to +3.2 (t = 2.17 Ga), indicating predominantly Rhyacian crustal sources for the parental magmas, similar to those ones found in other areas of the São Luís Craton. The data, integrated with published geological and geochronological information, indicate the occurrence of an important continental crust formation event in this area. The Paleoproterozoic evolution between 2.17 and 2.15 Ga is related to the Transamazonian orogeny. The granitoids of the Rosario Suite represent the main phase of continental arc magmatism that has continuity in other parts of the São Luís Craton and can be correlated with Rhyacian accretionary magmatism in the northwestern portion of the Amazonian Craton that amalgamated Archean terrains during the Transamazonian orogeny.KEYWORDS: Rosário Suite; São Luís Craton; Petrology; U-Pb geochronology; Sm-Nd T DM . RESUMO: O Cráton INTRODUCTIONIn models of global supercontinent reconstruction, the São Luís Craton and the northeastern portion of the Amazonian Craton (to the east of the Guayana Shield) have been considered remnants of the West African Craton preserved in the northern South American Platform after the breakup of the Pangea Supercontinent (Hurley et al. 1967, Torquato & Cordani 1981, Lesquer et al. 1984, Brito Neves et al. 2000.On the African side, several studies based on structural, geochemical, geophysical and geochronological data demonstrate the existence of Archean and dominantly juvenile Paleoproterozoic crust (Abouchami et al. 1990, Boher et al. 1992, Gasquet et al. 2003. On the Brazilian side, the northern part of the Amazonian Craton and São Luís Craton have demonstrated geochronological and evolutionary similarities. In this part of the Amazonian Craton, the ancient continental crust stabilized in the Archean is bordered by...

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Section: U-pb Geochronologysupporting

confidence: 73%

Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

et al. 2017

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“…Their environments of deposition have variously been assigned to marine, fluvio-deltaic and lacustrine regime [2,6,11,12]. These varying views stem from the absence of detailed stratigraphic information, coupled with virtually non-fossiliferous nature of its strata, and the lack of a simple basin-filling model for the embayment.…”

Section: Introductionmentioning

confidence: 99%

Stratigraphy and depositional environments of the Mamfe Formation and its implication on the tectonosedimentary evolution of the Ikom-Mamfe Embayment, West Africa

Bassey¹,

Eminue²,

Ajonina³

2013

Open Geosciences

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Abstract:A 42 m thick outcropping portion of the Mamfe Formation is subdivided into Manyu (31 m thick) and Kesham (11m thick) Members on the basis of textural, mineralogical and structural differences. The Manyu Member (Albian) consists of folded and indurated, medium to coarse grained arkosic sandstones and thickly laminated organic-rich shales deposited in a lacustrine environment. The Kesham Member (Cenomanian) consists of subarkoses intercalated with massive green shale and mudstone deposited in a fluvial environment. The change in depositional environment was tectonically controlled. The mid Cretaceous paleogeography of the embayment was governed by the NE-SW trending "Ikom ridge" which prevented marine incursion from adjacent the Benue Sea. Evaporites found within the basin were precipitated from ocean water that was periodically spilled by strong tides and storms across the ridge into the embayment. The filling-up of the embayment to base level in the Cenomanian resulted in a shift in the depositional center downstream to adjoining lower Benue Trough. Similarity in heavy mineral composition and maturity of the Cenomanian sandstones with recent clastics in the embayment indicates their derivation from the same source terrain and relatively stable tectonic and climatic conditions at the source area since the Cenomanian time.

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“…The geologic strata of the Anambra Basin were deposited in a syncline initiated by the major folding episode in the Benue trough during Late Cretaceous times. During the Maastrichtian, the Anambra Basin became silted up and extensive thickly vegetated swamps developed near sea level, on top of a broad delta fan built up by rivers bringing sediments from the hinterland (Wright et al, 1985). Sedimentation in the Anambra Basin commenced with the CampanoMaastrichtian marine and paralic shales of the Enugu and Nkporo Formations.…”

Section: Geologic Settingmentioning

confidence: 99%

“…Geological epoch favouring the formation of coal include the Carboneferous, Permian, and Jurassic to Tertiary. In southern Nigeria, the coal resources are found within the Mamu and Nsukka Formations of CampanianMaastrichtian age (Reyment, 1965;Wright et al, 1985). These formations outcrop at intervals along the Enugu Escarpment over a distance of about 144 Kilometers from Enugu to Ogboyoga in Kogi State (Fig.…”

Section: Introductionmentioning

confidence: 99%

Major oxides and trace element distributions in coal and coaly shale seams in the Enugu escarpment of South-Eastern Nigeria.

Ogala¹,

Omo-Irabor²,

Finkelman³

et al. 2010

Glo Jnl Geo Sci

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Elemental distributions in nine (9) sub-bituminous coal and four coaly shale samples from the Anambra Basin, southeastern Nigeria were determined using FUS-ICP and TD-ICP spectrometry. Of the major oxides in these samples, SiO 2 and Al 2 O 3 indicate the prevalence of quartz and clay minerals. The strong statistical correlation between SiO 2 and Al 2 O 3 indicates a common source, likely detrital. The strong correlation between the other major oxides with both SiO 2 and Al 2 O 3 indicates that all of these elements have a common detrital source. However, epigenetic carbonates and syngenetic or epigenetic sulphides may also be present. The concentrations of most trace elements in these coals are unremarkably, falling well within the range for U.S. and World coals. These data do not indicate any potential for economic by-product, potential technological problems or environmental or health concerns.

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Geology and Mineral Resources of West Africa

Abstract: I. Rolfe (ed.) Statistical methods in geology R. F. Cheeney Echinoid palaeobiology A. Smith Geomorphology in arid regions D. O. Doehring (ed.) Petroleum geology F. K. North Environmental change and tropical geomorphology I.

Cited by 133 publications

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Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

Stratigraphy and depositional environments of the Mamfe Formation and its implication on the tectonosedimentary evolution of the Ikom-Mamfe Embayment, West Africa

Major oxides and trace element distributions in coal and coaly shale seams in the Enugu escarpment of South-Eastern Nigeria.

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