____________________________________________________________________________________________ *Corresponding author: E-mail: udinmwenefosa@gmail.com; British Journal of Applied Science & Technology 4(17): 2417-2429, 2014 SCIENCEDOMAIN international www.sciencedomain.org Fracture Characterization, Mineral Vein Evolution and the Tectonic Pattern of Igarra Syn-Tectonic Granite, Southwestern Nigeria Oden, Michael I. 1 and Udinmwen Efosa 1* 1 Department of Geology, University of Calabar, PMB 1115, Calabar, Cross River State, Nigeria. Authors’ contributions This work was carried out in collaboration between all authors. Author OIM designed the study, wrote the protocol and managed the analyses of the study while Author UE wrote the first draft and managed the literature search. All authors read and approved the final manuscript. Received 19 th December 2013 Accepted 24 th February 2014 Published 21 st April 2014 ABSTRACT Extensive outcrops of the pan-African granite were studied in detail with particular interest in the joint pattern and mineral vein characteristics. The attitude of 57 tectonic joints and 60 mineral veins were measured, the length and width of the veins documented. Rose diagrams and graphs representing fractures and veins were plotted and analysed based on their behavior and preferred orientations. Two (2) basic trends of mode I fractures(joints) and veins were observed in the granites, these are the E-W trending joints and veins parallel to the maximum principal stress (σ 1 ) direction and the N-S trending joints and veins parallel to the minimum principal stress (σ 3 ) direction. These granites contain mostly Mode I fractures which require lower stress to initiate and propagate relative to Mode II and Mode III fractures, although other trends (NW-SE and NE-SW) of joints and veins were mapped, they are highly insignificant compared to the major E-W and N-S trending joints and veins within the plutons. Mineral veins in these syn-tectonic granites developed apertures that were sensitive to the orientations of the stresses; the widest veins being those oriented approximately in the E-W direction, parallel to the maximum principal stress (σ 1 ). Mineral veins in N-S orientation are generally thin and non-persistent; their formation indicates fluid pressure-build up in the course of the orogeny. The occurrence of sheet/exfoliation joints lends credence to the Original Research Article