264 D31. Precambrian Geology (Posters)

Wednesday, 7 November 2018
9:00 AM - 6:30 PM
Halls J-K

GEOCHEMISTRY AND PETROLOGY OF BASEMENT COMPLEX ROCKS AROUND AKUNGBA-AKOKO, SOUTHWESTERN NIGERIA

Paper number: 264-8
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Field, petrographic and petrochemical studies of the Basement Complex rocks around Akungba-Akoko were carried out with the aim of determining their petrology, petrochemical characteristics and origin.

The petrology of Akungba-Akoko area in the Southwestern Nigerian Basement Complex comprises of migmatite, granite gneiss and biotite gneiss intruded by biotite granite, charnockite and minor felsic and basic rocks. Seven rock samples comprising of two granite gneiss, two biotite gneiss, two biotite granite and one charnockite were collected during detailed geological mapping for petrographic and geochemical analyses.

Petrographic analysis shows that the gneisses and granitoids of the area are enriched in quartz, feldspars and mica and are granitic. Petrochemical data of the rocks reveal that they are enriched in SiO2, Al2O3 and Fe2O3 compared to CaO, Na2O, K2O and MgO. Using petrochemical variation diagrams, it was revealed that Akungba-Akoko granite gneiss and biotite gneiss are orthogneisses derived from metamorphism of igneous protolith(s) of granitic composition. The biotite granite and charnockite are of igneous/magmatic origin. The igneous protolith(s) of the granite gneiss and biotite gneiss are S-type granitoids probably derived from shallow crustal or sedimentary rocks; the biotite granite is I-type granitoid derived from crustal igneous rocks and the charnockite is M-type granitoid derived from mantle or deeper crustal source.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-320031

© Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.