PETROGRAPHY AND MICROTEXTURAL CHARACTERISTICS OF GRANODIORITE FROM WASIMI, SOUTHWESTERN NIGERIA
Journal: Earth Science Malaysia (ESMY)
Author: E. J. Oziegbe, O. O. Ocan, A. P. Adebisi
This is an open access article distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Rock samples of granodiorite from Wasimi were studied in detail to determine the minerals, mineral associations and the different micro-texture present in order to unravel the processes that were involved during the cooling of the magma. The following minerals were observed; plagioclase feldspars, K-feldspars, biotite, pyroxene, amphiboles, with zircon and sphene as accessory minerals. The pyroxene are engulfed in amphiboles and have reaction rims. Pyroxene occur as inclusions in plagioclase feldspars. Amphiboles are poikilitic with inclusions of quartz. Symplectic texture exits between the following minerals; plagioclase and K-feldspar, biotite and quartz, plagioclase and amphibole. The plagioclase feldspars have fractured and bent twin lamellae. Crystals of plagioclase feldspars are zoned and also exhibit both Carlsbad and albite form of twinning. It can be said that there was an initial slow cooling of the magma which was responsible for the large crystals of feldspars which was later followed by rapid cooling as the magma rises close to the surface which gave rise to zoned plagioclase feldspars and indication of high level intrusive.