Petrology and phase equilibrium modeling of granulites from Obudu in the Benin-Nigerian Shield, Southeastern Nigeria: implications for clockwise P-T evolution in a collisional orogen

Ugwuonah, Emmanuel Nwachukwu; Tsunogae, Toshiaki; Ekwueme, Barth N.

doi:10.1007/s00710-019-00652-4

Cited by 6 publications

(4 citation statements)

References 35 publications

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“…P–T pseudosection analyses calculated using THERMOCALC software of staurolite-biotite pelitic schist from north-central Nigeria, constrain garnet/staurolite equilibration within the range of 6.4–7.7 kbar and 610–630 °C ( Ugwuonah et al., 2017 ). Also, retrograde conditions were also estimated as 3.8 kbar/590 °C to 6.8 kbar/780 °C for modeling of granulite from southeastern Nigeria ( Ugwuonah et al., 2019 ). In the Boumnyebel talc-schist in Cameroon which is part of the Pan-African Belt of Central Africa, a metamorphic peak of ∼650 °C at 9.5 kbar has been reported ( Yonta-Ngoune et al., 2010 ).…”

Section: Discussionmentioning

confidence: 99%

Geochemistry and mineral chemistry of pelitic gneiss of Ikare area, southwestern Nigeria

Oziegbe

Ocan

Costin

et al. 2021

Heliyon

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This study conducts Electron Probe Microanalysis (EPMA), X-ray Fluorescence (XRF) and Laser Ablation Inductively Coupled Plasma Spectrometry (LA-ICP-MS) analysis on the pelitic gneiss of the Basement complex of Nigeria. Phase equilibrium modeling was undertaken in the MnO-NaGarnet has inclusions of sillimanite, biotite, and quartz. There is a very close association between biotite and sillimanite. Fibrolitic and prismatic sillimanite are both present. Fibrolitic sillimanite surrounding biotite could have possibly formed through melt-residue back reactions involving crystallization of melt. Garnet has almandine higher than 60 % and pyrope less than 33 %. Plagioclase feldspar has anorthite content between 29 and 39 %, comprising of both oligoclase and andesine. Microtextures such as cordierite corona round garnet, symplectite and kinked biotite were observed. The textural association indicates that cordierite was formed at the expense of garnet and sillimanite; garnet þ sillimanite þ plagioclase ¼> cordierite þ melt/fluid. Metamorphic peak conditions of 770-840 C and 5.5-7 kbar were obtained for the mineral assemblage garnet-biotite-sillimanite-K-feldspar-quartz indicating medium-pressure granulite facies metamorphism.

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Section: Discussionmentioning

confidence: 99%

Geochemistry and mineral chemistry of pelitic gneiss of Ikare area, southwestern Nigeria

Oziegbe

Ocan

Costin

et al. 2021

Heliyon

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“…Anhydrous mafic granulites form at temperatures above 850 °C, but in the presence of water-rich fluids, mafic rocks can undergo partial melting and granulites will form at temperatures below 750 °C [11]. Geothermometric calculations based on hornblende and plagioclase geothermometer by Holland and Blundy [12] gave temperatures of 690-740 °C at 5.2 kbar [5]. Although these low values fall within the temperature and pressure values for migmatitic pyroxene granulites, it has been interpreted as post-peak reequilibration.…”

Section: Petrological Significancementioning

confidence: 99%

“…Lithologically, the rocks are mesocratic and coarse-grained with minor leucocratic bands appearing in some places. Ekwueme and Kröner [4] suggested the pyroxene gneiss may have originated from a metagreywacke or granodiorite protolith; Ugwuonah et al [5], however, termed the rock a meta quartz diorite. The rocks have experienced high-grade metamorphism up to granulite facies [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

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Mineral Chemistry of Pyroxene Gneiss in Obudu, SE Nigeria, and Its Petrological Significance

Agbi,

Iroka

2023

Materials and Geoenvironment

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The pyroxene gneiss which forms part of the basement cover in southeast Nigeria is a coarse-grained weakly foliated rock that has experienced high-grade metamorphism and anatexis. Electron microprobe data obtained from samples of this pyroxene-bearing gneiss confirm that the essential minerals are plagioclase (andesine, An30 – 37), orthopyroxene (hypersthene, En55.3 – 61.2, Wo1.0 – 2.6, Fs36.3 – 43.7), and clinopyroxene (augite, En39.7 –42.3, Wo42.0 – 45.1, Fs14.2 – 17.0). This assemblage is a typical granulite facies mineralogy produced by igneous rocks with intermediate to mafic composition that have been metamorphosed at medium pressure. Other minerals are calcic amphibole (XMg = 0.56–0.59), biotite (XMg = 0.58–0.69), orthoclase, and quartz. Orthoclase occurs mainly in leucocratic bands and clinopyroxene absent samples and may have resulted from dehydration reaction and thus dissolved in the melt phase. Fe-Ti oxides of ilmenite, hematite, and magnetite occur as accessory minerals, giving the imprint of metamorphism under oxidizing conditions. The presence of exsolved titanohematite in ilmenite indicates retrogressive metamorphism.

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The occurrences, characteristics, and implications of chaotic rocks (accretionary rocks) within the Trans-Saharan orogenic belt in Nigeria

Nweke,

Ugwuonah,

Onuba

et al. 2024

Discov Geosci

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Petrology and phase equilibrium modeling of granulites from Obudu in the Benin-Nigerian Shield, Southeastern Nigeria: implications for clockwise P-T evolution in a collisional orogen

Cited by 6 publications

References 35 publications

Geochemistry and mineral chemistry of pelitic gneiss of Ikare area, southwestern Nigeria

Geochemistry and mineral chemistry of pelitic gneiss of Ikare area, southwestern Nigeria

Mineral Chemistry of Pyroxene Gneiss in Obudu, SE Nigeria, and Its Petrological Significance

The occurrences, characteristics, and implications of chaotic rocks (accretionary rocks) within the Trans-Saharan orogenic belt in Nigeria

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