Ba/Rb and Rb/Sr ratios as indicators of magmatic fractionation, postmagmatic alteration and mineralization - Afu younger granite complex, northern Nigeria.

Imeokparia, E.G.

doi:10.2343/geochemj.15.209

Cited by 23 publications

(6 citation statements)

References 22 publications

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“…High Ba content is consistent with the presence of abundant biotite and feldspars in the rock samples, which is related to plagioclase; biotite and hornblende fractionation (Chappell et al, 1998). Barium tend to remain in the solid phase during partial melting and would be most abundant in the higher melting temperature fractions, while aqueous phases associated with magmatic activity should have relatively low Ba concentrations (Imeokparia, 1981).…”

Section: Discussionsupporting

confidence: 63%

Geochemistry and Petrogenesis of the Banded and Granitic Gneisses in Parts of Kushaka Schist Belt, Northwestern Nigeria

2021

JEES

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The Kushaka schist belt in the Kwona Mutua and Kushaka areas is one of the 12 well recognized N-S trending belts composed of igneous, metamorphic and metasedimentary rocks in varying proportion. The major rocks of the belt comprise the Migmatite-Gneiss-Quartzite Complex, schists and Pan-African granitoids. Banded and granite gneisses constitute the bulk of the Migmatite-Gneiss-Quartzite Complex. Banded gneiss consists of paleosome and leucosome of dioritic, tonalitic, granodioritic and granitic composition while granite gneiss is composed of biotite, staurolite-biotite and staurolite-muscovite gneiss. Major mineral constituents of these rocks are quartz, orthoclase, plagioclase, pyroxene, biotite, muscovite, orthoclase, microcline and staurolite while the accessory minerals are titanite, apatite and iron oxides. Metamorphism may have reached grannulite facies locally with pyroxenes crystallizing in the dioritic and granodioritic rock. Analysis of geochemical data reveals marked variation in the abundance of SiO2 (60.77-77.53 wt %), Al2O3 (12.9-15.99 wt %), Fe2O3 (0.78-7.04 wt%), Na2O (1.67-5.15 wt%) and K2O (1.64-6.13 wt %), typical of rocks of hybrid sedimentary-igneous protoliths. Igneous protolith reveals decreasing P2O5 content with increasing silica content, low K2O/ Na2O ratio (0.24 -0.87), low K2O values (< 2.5 wt %) displaying mixed tholeiitic and calc-alkaline, metaluminous and peraluminous, ferroan and magnesian character, and high-K calc-alkaline to shoshonitic affinities. By contrast, the rocks of sedimentary protolith shows high K2O/ Na2O ratio (1.19 -2.5), high Na2O values (> 3 wt %) and staurolite mineral. Their pelitic and mafic attributes were derived essentially from a quartz-diorite, granodiorite and granite-quartz monzonite source. Fractional crystallization and partial melting of older dioritic-granodioritictonalitic source rock derived from upper mantle materials contaminated by continental crust played important roles during their genesis. They are enriched in Large Ion Lithophile Elements (LILE) but depleted in Nb, P and Ti typical of volcanic arc and syn-collisional settings.

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Section: Discussionsupporting

confidence: 63%

Geochemistry and Petrogenesis of the Banded and Granitic Gneisses in Parts of Kushaka Schist Belt, Northwestern Nigeria

2021

JEES

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“…A large scattering of data on the Rb þ Ba versus K 2 O plot suggests exchange of Rb and Ba between K-feldspar (dominant reservoir of Ba and Rb) and biotite (reservoir of Rb) with local metamorphic fluid (Fig. 8; Imeokparia, 1981). A similar process has been documented from the millimetre to centimetre sized charnockitic veins in the amphibolite-facies rocks (the 'incipient charnockitization'; Newton, 1992;Touret et al 2019).…”

Section: B Major-and Trace-element Compositionsmentioning

confidence: 58%

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

et al. 2022

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The North Purulia Shear Zone that dissects the granulite basement of the Chotanagpur Granite Gneissic Complex of the East Indian Shield exposes a deformed and metamorphosed nepheline syenite. The studied ‘foid-monzosyenite’ shows high abundances of large ion lithophile elements and high field strength elements with low abundances of compatible elements. Trace-element signatures show negative U, Th, Zr, Ti and Pb and positive Sr, Ba and Eu anomalies with respect to the primitive mantle. The chondrite-normalized diagram shows strongly fractionated rare earth element patterns ((La/Lu)N ∼23–87). Geochemical fingerprints suggest that the basanitic protolith was formed by low-degree partial melting of garnet peridotite in the sub-continental lithospheric mantle. The enriched large ion lithophile, high field strength element and light rare earth element concentrations (relative to primitive mantle) can be explained by a mixed mantle source with components from a previously deformed alkaline rock/carbonatite. Geochemical data do not support any significant crustal contamination and suggest variable fractionation of clinopyroxene, ilmenite, titanite and apatite from the parental melt. Petrological data are consistent with the view that the nepheline syenite magma was emplaced in a rift setting with a minimum temperature of 800–900°C, low fO2 conditions (below the fayalite–magnetite–quartz buffer) at a mid-crustal depth between 950 and 900 Ma. The continental rift zone, however, did not lead to the formation of an open ocean basin. Subsequently, the studied rock and its basement was deformed and metamorphosed in a continent–continent collisional setting at ∼900 Ma. Combining information from the other Indian occurrences with this study, it is demonstrated that the deformed alkaline rocks and carbonatite are potentially valuable for tracing the birth and demise of the palaeo-supercontinents.

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“…Groundmass texture is mostly glassy associated with minor iron oxide, quartz, plagioclase, and alkali feldspar. Vincenzo et al 1996;Imeokparia 1981). In contrast, Sr shows negative correlation with increasing SiO 2 .…”

Section: Classification and Petrographic Descriptionmentioning

confidence: 90%

Petrology and Geochemical Features of Semporna Volcanic Rocks, South-east Sabah, Malaysia

James¹,

Ghani²,

Akinola³

et al. 2021

JSM

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The volcanic rocks in Semporna Peninsula, Sabah, Malaysia forms parts of the Miocene subjected slab during the Miocene-Pliocene orogeny. This study presents new petrographic and geochemical data of volcanic rocks in Semporna area. The volcanic rocks range in composition from basaltic andesite, andesite, dacite to rhyolite, with most of the volcanic shows calc-alkaline affinity with a minor tholeiitic feature. The trace elements shows enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE) suggesting that the volcanic rocks have similar geochemical patterns and might come from similar magma source. The petrochemical data suggests that volcanic rocks of Semporna shows characteristic of subduction zone (negative Nb, Ta, and Ti). Decreasing magnitude of Europium anomalies from intermediate to acid lavas suggests an important role of plagioclase in the fractional crystallization. Negative Ce anomaly in part of Semporna volcanic rocks suggest that those volcanic rocks may related with emergence of oxygenated deep-sea environment. Tectonic diagrams showed that the Semporna volcanic rocks were formed in an island arc setting.

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Ba/Rb and Rb/Sr ratios as indicators of magmatic fractionation, postmagmatic alteration and mineralization - Afu younger granite complex, northern Nigeria.

Cited by 23 publications

References 22 publications

Geochemistry and Petrogenesis of the Banded and Granitic Gneisses in Parts of Kushaka Schist Belt, Northwestern Nigeria

Geochemistry and Petrogenesis of the Banded and Granitic Gneisses in Parts of Kushaka Schist Belt, Northwestern Nigeria

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

Petrology and Geochemical Features of Semporna Volcanic Rocks, South-east Sabah, Malaysia

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