MICROSTRUCTURAL INTERPRETATION OF THE GARNET-SILLIMANITE- BEARING GRANITE GNEISS OF IKARE AREA, SOUTHWESTERN NIGERIA
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Date
2023
Authors
Oziegbe, E. J.
Oziegbe, O.
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Publisher
Ife Journal of Science
Abstract
This study presents microstructures from the granite gneiss of the Basement complex of southwestern Nigeria. The granite gneiss of Ikare area comprises of the mineral assemblage; garnet, biotite, K-feldspar, quartz, plagioclase, sillimanite and opaque minerals. K-feldspar porphyroblasts have cuspate interstitial quartz grains, also quartz grains are included in K-feldspar. Most K-feldspar grains are highly strained and in some cases are fractured. Prismatic and fibrolite-type sillimanite are both present. Biotite is closely associated with fibrolite-type sillimanite. Sillimanite was observed to mimic the foliation produced by biotite. K-feldspar is the dominant mineral and could have formed by the dehydration reaction of biotite + plagioclase + quartz + sillimanite ==> garnet + K-feldspar + melt. Microscopic structures such as strained feldspar grains, micro-fractures in K-feldspar, simple twinning in K-feldspar, myrmekite, mimicking textures, microperthitic intergrowth and cuspate volumes of quartz surrounding K-feldspar are indicative of melt-bearing and solid-state deformation of regional metamorphic rocks.
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Citation
Oziegbe, E.J. and Oziegbe, O., 2023. Microstructural interpretation of the garnet-sillimanite-bearing granite gneiss of Ikare area, southwestern Nigeria. Ife Journal of Science, 25(1), pp.035-044.