Geodynamics of Some Precambrian Rocks of Southwestern Nigeria
Abstract
Magnetic carriers of Precambrian rocks of southwestern Nigeria were studied using paleomagnetism, rock magnetism, optical microscopy and scanning electron microscopy (SEM) comparatively to determine their geodynamics. The natural remanent magnetisation (NRM) of the remagnetised rocks was found to be 0.3-1.7 A/m and shows a northwesterly remanence with moderate inclination, whereas the unremagnetised rocks preserve weak NRM (< 0.5 A/m) with shallow westerly remanence. Both NRMs are carried by maghemite; which reveal higher to lower coercivity with respect to alternating field demagnetizations. Hysteresis parameters of remagnetised and unremagnetised rocks carry mixtures of multi-domain, pseudo-single domain and multi-domain grains respectively. SEM reveals fine poor-magnetite grains as discrete particles within plagioclase; suggestive of NW remanence in the remagnetized rocks that resides in the fine poor-maghemite inclusions whereas the coarse-grained maghemite in both rocks carry the westerly remanence of thermoremanence at Pan- African times tectonometamorphism.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNS13B0672O
- Keywords:
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- 0920 Gravity methods;
- EXPLORATION GEOPHYSICS;
- 0925 Magnetic and electrical methods;
- EXPLORATION GEOPHYSICS;
- 0935 Seismic methods;
- EXPLORATION GEOPHYSICS;
- 0999 General or miscellaneous;
- EXPLORATION GEOPHYSICS