Compositional features and petrogenetic affinity of precambrain aphibolitic-schist of Sepeteri are South western Nigeria

Okunola, OA; Akintola, AI; Egbeyemi, RO

doi:10.4314/gjgs.v4i2.45149

Cited by 1 publication

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“…4B) shows the entire metasediments plot outside the magmatic field also supporting the sedimentary antecedent of these rocks. These petrogenetic character of the Kushaka and Birnin Gwari metasediments is similar to those of Ilesha (Elueze, 1981), Lokoja-Jakura (Okunlola, 2003), Sepeteri (Okunlola et al, 2006), Birnin-Gwari schist (Ajibade et al, 2003), Okemesi (Okunlola and Okoroafor, 2009). Al2O3 / (CaO + Na2O + K2O) versus Al2O3 / Na2O + K2O geochemical data of the metasediments (after Maniar and Piccoli, 1989) (Fig.…”

Section: Petrogenetic Characteristicssupporting

confidence: 68%

“…Thus, metasediments of the Kushaka and Birnin Gwari are of arc basaltic and andesitic setting. Basalts and amphibolites have been used as geochemical indicators of the tectonic setting in the Nigerian schist belts as of back-arc tectonic environment, near subduction zone setting (Elueze, 1992;Okunlola et al, 2006;Danbatta and Garba, 2007). Grant (1978) obtained Rb -Sr data from Kusheriki granite emplaced across the gneissic envelope in Birnin Gwari and augen gneiss in the Sabon Gayam area of Kushaka schist belt.…”

Section: Provenance Of the Protolith And Tectonic Settingmentioning

confidence: 99%

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Geochemistry and Petrogenetic Features of Metasediments in Northern Part of Kushaka and Birnin Gwari Schist Belts NW Nigeria

Oluyede¹,

Ibrahim²,

Danbatta³

et al. 2021

JEES

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The Kushaka and Birnin Gwari metasediments and associated banded iron formations constitute important lithological units within the Precambrian Basement Complex. They were studied to evaluate their compositional characteristics and petrogenesis in order to contribute further to the understanding of the geodynamic evolution of Nigeria's Schist belts. The Kushaka metasediments comprise quartzite, graphite and sulphur bearing staurolitemuscovite quartz schist interbedded with Banded Iron Formations (BIFs) while the Birnin Gwari schist comprise staurolite-biotite quartz schists with lithic (angular to rounded clastic quartz, schistose, volcanic and quartzofeldspathic) sandstones. These schists are associated with fissile and ferruginous quartzite, banded and granitic gneisses, basalts and amphibolites. Petrographic work revealed varying proportions of quartz, staurolite, biotite and muscovite with subordinate iron-oxide minerals. Geochemically the metasediments in the Kushaka are enriched in SiO2 (61.23 to 65.99 wt %) with elevated values of Al2O3 (16.53 -20.93 wt %), Ba, V, W, La, Nb, Nd, Rb, Th and Zr; while the Birnin Gwari schists, even though enriched in SiO2 (63.03 to 65.13 wt %), has moderately elevated Al2O3 (15.4 -15.16 wt %) values but is depleted these trace elements. Field and geochemical characterization of the Kushaka metasediments suggests peraluminous, tholeiite and calc-alkaline character; arkosic and shale-greywacke sedimentary protoliths derived from quartzose sedimentary and granite-quartz monzonite provenance. Calculated ICV values of 0.52 -0.99 and occurrences of graphite and sulphur in the Kushaka metasediment suggests shallow stable shelf-type sediment of carbonate and iron formations in a reducing environment with matured sedimentary protolith. The Birnin Gwari metasediments on the other hand have a peraluminous and calc-alkaline character, inherited from shale-greywacke and quartzose sedimentary protoliths derived from granodioritic and granite-quartz monzonite provenance. ICV values of 1.12 -1.18 and angular and volcanic clasts suggest rapid subsidence of basin during genesis and / or tectonic instability in the surrounding environment with immature sedimentary protolith. This is an indication of two contrasting environment in an arc setting with contribution from basaltic and andesitic detritus. Available geochronological data on granite and granitic gneisses have ascribed the Kushaka schist belt to Kibaran and the Birnin Gwari schist belt a Pan-African age.

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Section: Petrogenetic Characteristicssupporting

confidence: 68%