Abstract
Background/Objectives: The Iseyin-Oyan schist belt is made up metasedimentary rocks, gneisses, granites and pegmatite intrusions. The study was aimed at identifying the schist within this belt and assess their metamorphism, geochemical characteristics and tectonic origin. Methods: Detailed geologic field mapping was undertaken where rocks were located, studied in-situ and identified. Samples of the schist were prepared for petrographic studies. Mineralogical contents were determined using X-Ray Diffraction technique. Polished sections were studied for mineral chemistry using Scanning Electron Microscope-Energy Dispersive Spectroscopy. Rock samples were analysed using X-Ray Fluorescence Spectroscopy and Inductively Coupled Plasma Emission Spectrometry. Geochemical data were elucidated using diverse geochemical discrimination diagrams. Findings: The schists are quartz mica schists and occur in close association with amphibolites, intrusive granitoids and pegmatites. The Mineral assemblage indicates upper (at the western part) to lower (at the central part) amphibolite facies grade metamorphism in the area. Pyrope-almandine garnets occur in quartz mica schist at the western parts reinforcing higher pressure-temperature metamorphic conditions. The concentration (in %) of SiO2 ranged from 56.4-71.6; Al2O3, 13.7-21.1; Fe2O3, 2-8; MgO, 0.7-2.4; and K2O, 2.1-5.5 supporting the evidence for differential degrees of metamorphism. Large iron lithophile and high field strength elements are similar to the average upper continental crust. Pronounced negative Europium anomaly pointed to the major roles played by feldspars during the geological processes. Plagioclase ranged from albite-oligoclase and oligoclase- andesine. The precursors of the quartz mica schist are possibly arkosic and greywacke sands deposited within the active continental margins. Evidence of uplift and overturning suggested for the differential metamorphism may be due to these events usually associated with active continental margins. Applications: This study has identified the once named undifferentiated schist in the study area to be quartz mica schist with details in their grades of metamorphism elucidated. Keywords: Quartz mica schist; geochemistry; mineral chemistry; Iseyin-Oyan schist belt; precambrian basement complex
Highlights
The undifferentiated schist has been identified as quartz mica schist having lateral variation in grade of metamorphism from medium to high grade
These evidences suggest a clockwise overturn which explains an upper amphibolite facies schist exposed at the western part of the study with mineral-ins of garnet and sillimanite believed to be deeper layers of the regionally deposited supracrustals metamorphosed during probable Eburnean times
Geochemical characteristics of major oxides supported discriminations based on metamorphic facies
Summary
The Iseyin-Oyan schist belt, within the southwestern part of Nigeria, ( Figure 1 ) is one of the of Upper Proterozoic supracrustal rocks which have been infolded into the ancient polymetamorphic migmatite–gneiss basement complex rocks. [1,2,3] The syn- to latetectonic Pan-African intrusive granitoids intrudes the supracrustals and the migmatite gneiss complex. [2,3]The Iseyin- Oyan schist belt continues into the Ibadan area and forms part of the late Archaean to Palaeoproterozoic banded gneiss–quartzite–schist sequence.[5,6] Previous studies revealed undifferentiated schists as the most widespread lithology; quartzites occur near the margins of the schist belt while massive amphibolites represent mafic igneous rocks. [5] More recent geological mapping [7,8,9,10,11] within the schist belt reported the occurrence of lithologic units similar to those reported in earlier studies. The Iseyin-Oyan schist belt, within the southwestern part of Nigeria, ( Figure 1 ) is one of the of Upper Proterozoic supracrustal rocks which have been infolded into the ancient polymetamorphic migmatite–gneiss basement complex rocks. Much of the information on the geology of the area is contained in the geological map produced by the Nigerian Geological Survey Agency (NGSA) [13] where it is revealed to be underlain by “Undifferentiated Schist” associated with many igneous intrusion of Older granite that metamorphosed surrounding rocks during the Proterozoic era [13]. The present area is located within the Iseyin-Oyan schist belt in Southwestern Nigeria. It is defined by the geographical coordinates of Latitude 8◦ 00′ N and 8◦ 08′ N and Longitude 3◦ 00′ E and 3◦ 07′ E
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
