Geochemistry and Mineral Chemistry of Amphibolites in Parts of the Proterozoic Ilesa Schist Belt, Southwestern Nigeria

Amphibolite is an important lithologic unit of the Nigerian basement complex that are commonly intercalated within metasedimentary sequences. Disseminated grains of sulphide minerals and base metal deposits are reported to occur in amphibolites and some other lithologies in other schist belts of Nigeria apart from the Iseyin-Oyan schist belt. Detailed geochemical study of amphibolitic rocks in this schist belt is scarce in literature, whereas none exist for the area under study, thus, this study is aimed at delineating the amphibolites within the Iseyin-Oyan schist belt around Itasa area with detail appraisal of their petrography and geochemical characteristics. A geologic field mapping was undertaken, and fresh representative amphibolite samples were obtained. Petrographic and geochemical studies of the samples were carried out with a view to understand their nature and petrogenetic characteristics. Geochemical data were elucidated using diverse geochemical discrimination diagrams. The amphibolites occur as lenses of small to large rocky boulders trending NNE-SSW and are essentially basal to quartz mica schist. Modal compositions revealed that they are dominantly composed of hornblende and plagioclase. XRD and mineral chemistry revealed that the plagioclase ranged from andesine to anorthite while hornblende is mainly magnesiohornblende. Geochemical data and discrimination diagrams revealed that the amphibolites are formed from basaltic to basaltic-andesite protolith that are of tholeiitic nature and had suffered crustal contamination. Tectonic discrimination diagrams indicated that the rocks were emplaced in the Mid Ocean Ridge but had been affected by collision due to Pan African Orogenic tectonic event.

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Mineralisation potential assessment using analytical hierarchy process (AHP) modeling technique: A case study of Ilesha schist belt, southwestern Nigeria

Results in Geophysical Sciences ◽

10.1016/j.ringps.2021.100026 ◽

2021 ◽

Vol 7 ◽

pp. 100026

Author(s):

A.A. Akinlalu ◽

G.M. Olayanju ◽

K.A.N. Adiat ◽

G.O. Omosuyi

Keyword(s):

Analytical Hierarchy Process ◽

Modeling Technique ◽

Schist Belt ◽

Southwestern Nigeria ◽

Mineralisation Potential ◽

Hierarchy Process

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Geochemical Characteristics and Tectonic Setting of Amphibolites in Ifewara Area, Ife-Ilesha Schist Belt, Southwestern Nigeria

Earth Science Research ◽

10.5539/esr.v6n1p43 ◽

2016 ◽

Vol 6 (1) ◽

pp. 43 ◽

Cited By ~ 1

Author(s):

Anthony Temidayo Bolarinwa ◽

Adebimpe Atinuke Adepoju

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Major Element ◽

Tectonic Setting ◽

Crustal Contamination ◽

Geochemical Evolution ◽

Schist Belt ◽

Southwestern Nigeria ◽

Eu Anomaly ◽

Ree Patterns

Trace and Rare Earth Elements (REEs) data are used to constrain the geochemical evolution of the amphibolites from Ifewara in the Ife-Ilesha schist belt of southwestern Nigeria. The amphibolites can be grouped into banded and sheared amphibolites. Major element data show SiO2 (48.34%), Fe2O3 (11.03-17.88%), MgO (5.76-9.90%), CaO (7.76-18.6%) and TiO2 (0.44-1.77%) contents which are similar to amphibolites in other schist belts in Nigeria. The Al2O3 (2.85-15.55%) content is varied, with the higher values suggesting alkali basalt protolith. Trace and rare earth elements composition reveal Sr (160-1077ppm), Rb (0.5-22.9ppm), Ni (4.7-10.2ppm), Co (12.2-50.9 ppm) and Cr (2-7ppm). Chondrite-normalized REE patterns show that the banded amphibolites have HREE depletion and both negative and positive Eu anomalies while the sheared variety showed slight LREE enrichment with no apparent Eu anomaly. The study amphibolites plot in the Mid Oceanic Ridge Basalts (MORB) and within plate basalt fields on the Zr/Y vs Zr discriminatory diagrams. They are further classified as volcanic arc basalt and E-type MORB on the Th- Hf/3- Ta and the Zr-Nb-Y diagrams. The amphibolites precursor is considered a tholeiitic suite that suffered crustal contamination, during emplacement in a rifted crust.

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Petrogenetic and Compositional Features of Rare Metal Pan-African Post-Collisional Pegmatites of Southwestern Nigeria; A Status Review

Contemporary Trends in Geoscience ◽

10.2478/ctg-2018-0012 ◽

2018 ◽

Vol 7 (2) ◽

pp. 166-187

Author(s):

Abiola Oyebamiji ◽

Adeniyi JohnPaul Adewumi ◽

Tehseen Zafar ◽

Adegbola Odebunmi ◽

Philips Falae ◽

...

Keyword(s):

Mineral Chemistry ◽

Rare Metal ◽

Border Zone ◽

Chemical Compositions ◽

Molten Material ◽

Southwestern Nigeria ◽

Pan African ◽

Opening And Closing ◽

High Degree ◽

Rare Metal Pegmatite

Abstract This research reviews the geology, petrogenesis, compositional trends and geochronology of the rare-metal pegmatite of southwestern Nigeria. The source of these pegmatites is still presently debated which have been explained as either product of highly fractionated molten material or anatexis of the local crust. However, published works of past authors have been compiled to give a detailed understanding of the formation of the mineral deposits. The basement complex of southwestern Nigeria comprises of Precambrian rocks of amphibolite, the hornblende gneiss and the granite gneisses which were formed as a result of the opening and closing of the ensialic basin with significant, extensive subduction during the Pan-African orogeny. The pegmatites in this region have shown internal zoning and a high degree of evolution from the border zone to the core zone during the crystallization and solidification of the felsic granite to pegmatite melt. The rare-metal pegmatites have distinct chemical compositions and mineralogy, containing quartz, biotite, muscovite, microcline, garnet with localized tourmaline, tantalite and columbite. These pegmatites vary significantly by their bulk-rock and mineral chemistry which indicates a more peraluminous attribute and enrichments of lithophile elements of Rb, Cs, Ta and Ba. Previous K/Ar isotopic ages (502.8±13.0 Ma and 514.5±13.2 Ma) suggest that the pegmatites are related to the post-collisional phase of intensive metasomatism. Adopted from previous studies, a five-stage conceptual model of evolution which is widely accepted have been proposed for the origin of the pegmatites.

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MINERAL CHEMISTRY AND GEOCHEMISTRY OF HYPERSTHENE-BEARING DIORITE FROM ERUSU AKOKO, SOUTHWESTERN NIGERIA

Malaysian Journal of Geosciences ◽

10.26480/mjg.01.2020.13.18 ◽

2020 ◽

Vol 4 (1) ◽

pp. 13-18

Author(s):

E. J. Oziegbe ◽

V. O. Olarewaju ◽

O. O. Ocan

Keyword(s):

Chemical Composition ◽

Chemical Properties ◽

Mineral Chemistry ◽

Accessory Mineral ◽

Southwestern Nigeria ◽

Hydrous Minerals ◽

Icp Ms ◽

Composition Of Minerals ◽

Textural Relationship ◽

Opaque Minerals

Samples of mafic intrusive rock were analyzed for their mineralogical and chemical properties. The textural relationship was studied using the petrographic microscope, elemental composition of minerals was determined using the Electron Microprobe and the whole rock chemical analysis was done using the XRF and ICP-MS. The following minerals were observed in order of abundance; pyroxene, amphibole, plagioclase, biotite, opaque minerals, quartz and chlorite, with apatite and zircon occurring as accessory mineral. Two types of pyroxenes were observed; orthopyroxene (hypersthene) and clinopyroxene. Texturally, amphiboles have inclusions of plagioclase and pyroxene. The plagioclase has undergone sericitization. The chemical composition of the pyroxene is En51.95Fs44.53Wo3.52, biotite has Fe/(Fe+Mg):0.42, Mg/(Fe+Mg):0.59, and plagioclase is Ab63.5An34.55Or1.95. Whole rock chemistry shows a chemical composition; SiO2: 45.15 %, Al2O3: 14.04 %, Fe2O3: 16.01 %, MgO: 5.65 %, CaO: 7.58 % and TiO2: 3.59 %. There is an enrichment of LREE and a depletion of HREE. Based on the minerals, mineral chemistry and the geochemistry of the studied rock, the rock is mafic and hydrous minerals formed by hydration recrystallization of pyroxene. The rock has extensively retrogressed but has not been affected by any form of deformation.

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