Report of geologic mapping project of area j, Igayaza Isingiro district, Western Uganda

Abstract

This report provides a comprehensive summary of the outcomes from the mapping project conducted in the Igayaza region, situated within the Isingiro district in the southwestern part of Uganda. The project encompassed a range of field activities, including traversing the mapping areas to gather geo-data, collecting samples at specified locations for subsequent laboratory analysis, and conducting data interpretation. During the field project, records were maintained of rock descriptions, along with pertinent measurements such as strikes, dips, and overall rock trends. A diverse array of rock types were identified, including shale, quartzite, granite, phyletic shales, laterites, and conglomerates. Shales, constituting more than 70% of the mapped region, dominated the landscape, while quartzite, although abundant, occurred in comparatively lower concentrations. Other rock types were observed in limited quantities within specific areas. Petrographic analysis unveiled clay minerals as the predominant constituents within all shale varieties, while quartz was most prevalent in quartzite rocks. Numerous geological structures were encountered throughout the surveyed region, many of which suggested tectonic processes of formation. These structures encompassed folds, joints, beddings, foliation, mud cracks, boudinage, and cleavages. A prevailing orientation emerged within major structures, aligning with NW/SW and NW/NE trends, evident in bed layers and joint formations. These trends were attributed to historical compressional forces oriented in the NW-SE and NE-SW directions, giving rise to structures aligned in NE-SW and NW-SE orientations, respectively. Various features, including relict bedding within quartzites, offered insights into the regional metamorphic grade, indicating a range from low to moderate levels. Metamorphic grade was observed to diminish in proximity to areas hosting metamorphosing granite intrusions. Adjacent to granite intrusions, signs of contact metamorphism were evident in nearby rocks. Microscopic analysis disclosed wavy extinction patterns in quartzite thin sections, suggesting deformation due to metamorphism or tectonic stress. The presence of micro fractures and boudinage in select areas indicated instances of brittle deformation. The drainage pattern within the area was notably influenced by structural factors. While no economically valuable minerals were identified, the region did contain industrial minerals of significant importance, such as sand, kaolin, shales, and quartzites, which are predominantly employed in construction activities. In the Igayaza area, key economic activities encompass crop cultivation (particularly matooke cultivation), limited-scale animal husbandry, bricklaying, and stone quarrying.