Abstract: The Jarawa Younger Granite Complex of Northcentral Nigeria is part of a larger belt of the Jurassic Younger Granite suite of Northern Nigeria. They are intruded into older Basement Complex rocks and are therefore structurally controlled by the pre-existing structures in the basement. Though this area is interesting in terms of geology and tectonic setting, detailed geological and structural interpretation of features in the area is lacking due to limited accessibility occasioned by the rugged/hilly nature of the terrain. Principal Component Analysis (PCA), Minimum Noise Fraction (MNF) and Band Ratio (BR) techniques were applied on Landsat 8 data for lithological discrimination while for structural interpretation, filtering techniques of edge enhancement and edge detection were applied on Digital Elevation Model (DEM) acquired by Shuttle Radar Topographic Mission (SRTM) sensor. The PCA, MNF and BR were useful for preliminary lithological and structural discrimination between different rock units in the area. For structural interpretation, DEM was used to generate shaded relief model and edge maps which enable detailed structural interpretation. Geologic fieldwork was further conducted to validate structures and units identified from image processing. Field investigations revealed five litho-textural units including Basement Complex, Hornblende-Biotite-Granite, Biotite-Microgranite, Jarawa Biotite-Granite and Jarawa Biotite-Microgranite. Foliations observed at the contact between the Younger Granite Complex and the Basement complex averagely trend NE-SW; the Rafin Jaki Granite Porphyry Dyke which range in size from 0.3 – 0.9 meters is seen to harbour xenoliths of older Basement rocks mostly at the contact between the two. Joints and veins in the Jarawa biotite granite, biotite micro granite, dolerite dykes and Rafin jaki granite porphyry show a dominant trend of NW-SE; joints and veins in the hornblende biotite granite and migmatite gneisses show a dominant trend of NNE-SSW, hornblende granite porphyry shows a NE-SW trend and the Jarawa microgranite shows N-S, ENE-WSW dominant trend. The later rocks have a dominant trend of NW-SE with the exception of the Jarawa microgranite that is almost in alignment with the earlier rocks and the rocks of the basement which show a NNE-SSW dominant trend. The dominant trend of the basement; NNE-SSW, and the NW-SE, NE-SW, N-S, and ENE-WSW of the granitic rocks within the study area correspond with the major structural directions of N-S, NE-SW, NW-SE, NNE-SSW and ENE-WSW of the Basement Complex and Younger Granite Ring Complex. These results have important implications in terms of regional tectonics and geological mapping as well as mineral exploration and geotechnics.
Keywords: Jarawa, PCA, Dyke, SRTM, Remote sensing
| DOI: 10.17148/IARJSET.2019.6107