Integrated Mapping of Lineaments in Ago-Iwoye SE, SW Nigeria

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Author(s) Omosanya, K.O | Mosuro, G.O | Akinbodewa A.E
Pages 68-79
Volume 1
Issue 2
Date February, 2012
Keywords Mapping, Joints, Lineament, Orientation, Tectonic, Stresses.
Abstract

Structural studies of Joints on rock exposures was carried in Ago-Iwoye, NE, SW, Nigeria (N 060561 -060581 and E 0030 521-0030 561) with the aim of integrating linear structures from outcrop to larger lineament on satellite imageries. A petrographic study of rocks was done in order to identify the rock types of the study area. Structural measurement such as the attitude (strike and dip), length, and average perpendicular distance was taken on three hundred and twenty six (326) joints while sixty nine (69) lineaments were extracted from Google Earth imageries covering the study area and its surroundings; the lengths and orientations of the lineaments were also determined and plotted on Rosette diagrams and lineament density map. Slightly foliated granite-gneiss, biotite gneiss, and pegmatites were identified from the petrographic studies. The dominant orientations of Joints are E-W & ENE-WSW suggestive of dominant N-S or NNW-SSE directed stresses, and joint types mapped include systematic, non-systematic, conjugate, T-joints and cross joints with average perpendicular spacing between joints ranging from 4cm - 67cm. Two dominant structural domains were identified from the lineament map; these are NE-SW & NW-SE with dominant orientation of Lineament being NE-SW, suggestive of NW-SE tectonic (extensional forces), minor ENE-WSW and E-W orientation suggestive of shearing evinced by conjugate joints sets were also recorded. Evidence from the lineament density map suggest that the NE, NW & SW parts of the study area were highly dense while the E-SE part is less dense or near zero relative to lineament concentration; this same trend was earlier observed during the ground mapping. There is overlap between the minor NW-SE/ENE-WSW orientations in lineaments and joints; this implies that these fractures in both cases were produced by similar tectonic events while other orientations are product of dissimilar tectonic events/regimes.

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