Litho-Lineament Mapping of Rocks in Ila Orangun Area Southwestern Nigeria Using Remote Sensing and Aeromagnetic Data: Implications for Mineral Exploration (Published)
Ila Orangun is located north of Okemesi and falls within latitudes 7054l and 8000l N and longitudes 40 53l and 50 00l E respectively. Field studies revealed six lithological units in the study area namely quartzites, granites, granite gneiss, porphyritic granites, amphibolite schist and pegmatites. The aim of the research is to elucidate the geology and structure as well as evaluate the metallic mineral potentials of the study area. An integrated multi-technique study approach was adopted for reconnaissance survey and structural interpretation which involved the use of acquired remotely sensed satellite imageries such as Landsat-8 OLI, shuttle radar topographic Mission, Radar Sentinel-2A and a geophysical method involving the use of aeromagnetic data. Results obtained from interpretation of remote sensing data was used to produce different lineament maps which displayed fractures of varying lengths and trend dominantly in the NE-SW directions and subsidiary fractures also orientate in the NW-SE, E-W and N-S directions. Results from the stereographic projection plots showed that the dominant orientation of foliation planes is in the NE-SW direction with the NE and SE sections of the study area recording the highest cluster of the foliation planes. Hence, the eastern section spotted as the mineralization zone.
Keywords: Aeromagnetic data, Brittle, Ila Orangun, Remote Sensing, lineament
Petrology and Petrochemistry of Basement Rocks in Ila Orangun Area, Southwestern Nigeria (Published)
From field studies, six (6) lithological units were identified to be common around the study area which includes quartzites, granites, granite gneiss, porphyritic granites, amphibolite and pegmatites. The results of petrographical analyses show the mineral assemblages of the various rock types in the area which include quartzites as containing quartz, biotite, muscovite and myrmekite. Granite gneiss contains quartz, biotite, orthoclase, myrmekite, microcline, nepheline, hornblende and plagioclase. Pegmatite contains quartz, myrmekite, plagioclase, hornblende, microcline and muscovites. Porphyritic granites were observed to contain quartz, biotite, microcline, orthoclase and tourmaline. Granite contains quartz, biotite, hornblende, plagioclase and orthoclase while Amphibolite schist contains quartz, biotite, hornblende and muscovites. For the purpose of this study twenty (20) pulverized rock samples were taken to the laboratory for geochemical analysis with their results used in the classification as well as suggest the geochemical attributes of the rocks. Geochemical results obtained and interpreted using various geochemical plots or discrimination plots all classified the rocks in the area as belonging to both the peralkaline metaluminous and peraluminous types. Results for the major oxides ratios produced for Na2O/K2O, Al2O3/Na2O + CaO + K2O and Na2O + CaO + K2O/Al2O3 show the excess of alumina, Al2O3 over the alkaline Na2O +CaO +k2O thus suggesting peraluminous rocks. While the excess of the alkali over the alumina suggests the peralkaline metaluminous rock type. The results of correlation coefficient show a perfect strong positive correlation which shows that they are of same geogenic sources while negative correlation coefficient values indicate a perfect weak negative correlation suggesting that they are of heterogeneous geogenic sources. The result of the factor analysis show the elemental association of the trace elements and heavy metals represented as variables in the statistical analysis. Hence, establishing the elemental association of Component 1 as consisting of Ag-As-Ba-Cd-Co, Component 2 as Cr-Cu-Ni, Component 3 as Pb-Rb, Component 4 as Zn-Fe-V and Component 5 as U-Mn. Component 1 suggest the possibilities of sulphide and gold mineralization. Component 2 suggesting pathfinder elements while Components 3, 4 and 5 suggest weathered or dispersed elements. Hence, the occurrence of heavy metallic minerals in the rocks will serve huge economic significance with focus on the pegmatites in the area.
Keywords: Ila Orangun, Pegmatites, Petrochemistry, peraluminous, petrography