Volume 2, Issue 3, January - June, 2025

Mineral chemistry and P-T conditions of incipient Charnockite around Ikare, Southwestern Nigeria

Oyeshomo AV^1♦, Bolarinwa AT², Altenberger U³, Harlov DE⁴, Olayemi SO², Ajila TF¹

¹Department of Earth Sciences, Adekunle Ajasin University, Akungba-Akoko, Nigeria
²Department of Geology, University of Ibadan, Ibadan, Nigeria
³Institute of Earth and Environmental Studies, University of Potsdam, 14476 Potsdam, Germany
⁴Deutsches Geo Forschungs Zentrum, Telegrafenberg, 14473 Potsdam, Germany

^♦Corresponding Author
Department of Earth Sciences, Adekunle Ajasin University, Akungba-Akoko, Nigeria

ABSTRACT

Charnockites could be of magmatic, metamorphic, or metasomatic origin and formed in diverse geotectonic settings. Previous works on incipient charnockitic rocks outcropping around Ikare, southwestern Nigeria, were inconclusive due to lack of micro-chemical data for pressure-temperature estimation. Hence, this present study was designed to determine the petrology, geochemistry, and pressure-temperature estimates of these charnockitic rocks. Petrographic studies showed that the essential minerals are quartz, plagioclase, alkali feldspar, biotite, orthopyroxene and hornblende ± clinopyroxene. The accessory minerals are zircon, apatite, ilmenite, and magnetite. Hornblende is stable with orthopyroxene. Plagioclase feldspars in the charnockite are andesine and be expressed as An35Ab64. Orthopyroxene be described as Fs57.5En42.5Wo0 are mainly hypersthene. Hornblende in the incipient charnockite varies from pargasite to ferropargasite in composition. Alkali feldspar is a microcline. Geothermobarometric computations using both hornblende-plagioclase and two-feldspar thermometers obtained temperatures ranging from 7400C to 8000C at assumed pressure of five kbar. The temperature range 8000C recorded on thermodynamic modeling of a sample, further suggest a low pressure-high temperature metamorphic conditions for the incipient charnockite around Ikare

Keywords: Magmatic, micro-chemical, geothermobarometric, incipient charnockite, Ikare

Discovery Nature, 2025, 2(3), e1dn1039

PDF

DOI: https://doi.org/10.54905/disssi.v2i3.e1dn1039

Published: 03 January 2025