Mesoscopic Structural Analysis of the Schist Enclaves in Oban Massif, South-Eastern Nigeria

Asinya, Enah Asinya; Oden, M. I.; Ephraim, Bassey Edem; Udinmwen, Efosa; Edem, Selong

doi:10.9734/ajopacs/2016/30076

Cited by 4 publications

(3 citation statements)

References 10 publications

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“…The most recent event was the Pan-African tectonothermal event. Each of these events has left structural imprints on the basement rocks of the complex as suggested by several workers on the Nigerian basement including Rahaman et al, 1981;Onyeagocha and Ekwueme, 1982;Ephraim, 2009;Igonor, et al, 2011;Ukwang et al, 2012;Oden 2012;Opara et al,;Obi et al, (2014) Edem et al, 2015;Asinya et al, 2016;Edem et al, 2016;Ekwueme and Okoro, 2019. It is however, thought that the Pan-African deformation event was widespread and very pervasive to the extent that it probably, totally obliterated all preceding structural imprints of earlier orogenies. Consequently, the geometric characteristic of structures in the Oban Massif is expected to reflect mainly the Pan-African event of 600 ± 150 Ma.…”

Section: Geology Of the Study Areamentioning

confidence: 94%

Petrology Of Intrusive Rocks Of Oban Massif, Southeastern Nigeria

Grace O,

Barth N,

Bassey E

2024

Glo Jnl Geo Sci

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A total of forty- nine (49) fresh rock samples of the various intrusive rocks (granitoids and dolerites)were collected from the field. These rocks intruded metamorphic rocks that include pyllites, schists, gneisses and amphibolites in the Oban Massif. Intrusive rocks pegmatitic granites and granodiorite exhibit porphyritic texture rich in feldspars, quartz, muscovite, biotite, tourmaline and beryl. The granodiorite contains xenoliths of metamorphic rocks. The dolerites are ophitic and composed of plagioclase, olivine and pyroxene. From the geochemical analyses, the intrusive rocks show SiO2 to be the most abundant chemical component in all the rock units with its highest value recorded in the pegmatitic granite (Av. 70.07%), while the lowest value (59.68%) recorded in the dolerite. Al2O3 also display high concentration in rocks of Oban Massif. The rocks have concentrations of Al2O3> (CaO + Na2O + K2O), low MgO, and TiO2 concentrations while pegmatitic granites exhibit low concentration in FeOTotal. The alkaline and calc-alkaline, granitoid intrusives in the study area were found to be I-type crustal orogenic granitoids that represent a late stage intrusion along major shear and thrust zones.The results of trace elements analysis revealed that almost all the intrusive rocks of Oban Massif contain high Ba content, the highest values occur in the pegmatitic granite with a mean concentration of (2266ppm), while meladiorite was found to contain the least amount of Ba (44ppm).

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Section: Geology Of the Study Areamentioning

confidence: 94%

Petrology Of Intrusive Rocks Of Oban Massif, Southeastern Nigeria

Grace O,

Barth N,

Bassey E

2024

Glo Jnl Geo Sci

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“…The rocks are intruded by diorites, granodiorites, pegmatites, monzonites, granites, and tonalities [26]. The granodiorites cover around 10% of the region and are the most noticeable intrusive rocks They are generally gigantic, weakly foliated, and medium-coarse grained [4,26,27]. Lateritic sediments that originate from the weathering of underlying rocks overlie the rocks in some locations.…”

Section: Location General Geology and Tectonics Of The Study Areamentioning

confidence: 99%

Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

et al. 2022

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A gamma spectrometric analysis of rock samples collected from the Precambrian Oban Massif, southeastern Nigeria, was performed to determine some primordial radioelements’ activity concentrations: U-238, Th-232, and K-40, and their associated radiological hazards. The mean activity of the primordial radionuclides was determined to be 1073.06 ± 0.65, 160.74 ± 1.32, and 250.76 ± 0.91 Bq·kg−1 for 40K, 238U, and 232Th, respectively, showing that they are inhomogeneously distributed, with activity changing with the rock type and location. The activity concentrations are highest in biotite garnet schist, quartz diorite, and biotite gneiss rock domains. The mean values of the radiological hazards are 0.08 Bq·kg−1 (alpha index), 2.15 Bq·kg−1(gamma index), 2.06 Bq·kg−1(internal) and 1.63 Bq·kg−1 (external4.30 Bq·kg−1(representative level index6), 602.23 Bq·kg−1, (radium equivalent), 780 nGy·h−1 (total absorbed dose rate), 270.91 nGy·h−1 (indoor), 509.78 nGy·h−1 (outdoor), 624.99, 1329.07 and 1954.06 mSv·yr−1 (outdoor, indoor and total annual effective dose equivalent, respectively), 6448.40 (cumulative excess lifetime cancer risk) and 248.94–3761.47 Bq·kg−1 (annual gonadal dose equivalent). These results are higher than their various permissible limits (except at Ako Community) and suggest that rocks in the area may be unsuitable for constructing dwelling places. It is strongly advised that basic safety standards and precautionary measures recommended by the European Commission should be strictly adhered to while dealing with these rocks.

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“…In terms of petrology, structures, and metallogenic the Nigerian schist belts, which occupy a basically N-S trending trough (Elueze 2002;Elueze and Okunlola 2003), and are common in western and northern Nigeria (Turner, 1983;Danbatta, 2003). Nevertheless, schist belts and regions occur in the central and eastern portions of Nigeria (Oluyide and Okunlola, 1995;Oden, 2012a;Asinya et al, 2016;Oden et al, 2017). The Igarra schist belt is located to the east of Nigeria's southwestern basement complex.…”

mentioning

confidence: 99%

Structural framework and deformation episodes in the igarra schist belt, southwestern nigeria

Omang¹,

Asinya²,

Udinmwen³

et al. 2022

Glo Jnl Geo Sci

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The structural framework of the Igarra schist belt consists of brittle (mainly fractures) and ductile (foliation, cleavage, folds, lineations, strain markers) structures. The geometry of these structures reveals two major occurrences of transpressional deformation affected the schist belt. These are an older dominantly ductile deformation with NW–SE λ1 which developed foliations, cleavage, folds, and mineral/stretching lineations deforming only the metasediments and a younger brittle–ductile, E-W tectonic shortening deformation which closed deformations in the Igarra schist belt, deforming both the metasediments and granitoids, producing almost all the brittle structures in the belt. Minor fracture trends which are not associated with any of the major episodes of deformation and E-W transposition foliation in marble and gneisses constitute a relic of an unconfirmed possibly older episode of deformation. Ductile and semi-brittle shear zones in the Igarra schist belt are few and usually occur on small scale (outcrop scale), hence, they do not constitute a major episode of deformation. Mineralizations in the Igarra schist belt are pegmatite and quartz which are emplaced mainly in fractures with industrial minerals like marbles.

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Mesoscopic Structural Analysis of the Schist Enclaves in Oban Massif, South-Eastern Nigeria

Cited by 4 publications

References 10 publications

Petrology Of Intrusive Rocks Of Oban Massif, Southeastern Nigeria

Petrology Of Intrusive Rocks Of Oban Massif, Southeastern Nigeria

Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

Structural framework and deformation episodes in the igarra schist belt, southwestern nigeria

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