GEOLOGICAL MAPPING PROJECT REPORT OF AREA I, GAYAZA, ISINGIRO DISTRICT, WESTERN UGANDA.

Abstract

The Geological mapping exercise was carried out in Igayaza, Isingiro, Western Uganda from 30th May 2022 to 6th June 2022. The main aim of this field mapping project was to give students practical experience with field geological mapping tasks, including field preparations and geological written reports, as well as to practically learn field data gathering methods and procedures. Following the field trip, various techniques were employed, such as utilizing a microscope for laboratory petrographic analysis and interpretation, Stereonet software for structural data analysis and interpretation, and ARCGIS for digitizing and creating cross sections from maps. This study examines the general geology, stratigraphy, structure, petrography, and metamorphism of the K-A system in southern Uganda, which serves as the northern extension of the Kibaran mobile belt. The Isingiro area is relatively low to medium in elevation. The majority of the lands in Isingiro district, Uganda, are covered by the noticeable Karagwe-Ankolean system, which is part of the Kibaran belt of Central Africa rock system on which the geologic mapping exercise was carried out. The mapped region (Area I) is located in Nyakigyera subcounty, Isingiro district, between the UTM coordinates Eastings (250000-252000) and Northings (9915000-9917000). It borders Igaharo to the east and Kabingo to the south, with a total land area of four-square kilometers. The area is underlain by rocks of Paleoproterozoic age that include granites, quartzites, shales, conglomerates and phyllites. In general, the Isingiro region and neighboring areas are part of Uganda's paleoproterozoic geology under the Rwenzori fold belt, which is where the karagweAnkolean rock structure can be found. Major features found in this area include joints, bedding planes, faults, and folds, while minor structures include quartz veins and crenulation cleavage. The Gayaza Synclinorium is a typical cross fold with an axis that plunges to the southwest at a small angle inside the Karagwe-Ankolean rocks of southwest Uganda. The fold measures approximately six kilometers across and is preserved as a topographic high towering above the nearby low-lying anticlines. The major structural trends are attributed to both Regional and Cross-folding oriented in the NW-SE and NE-SW directions. The petrographic examination of the thin sections reveals that the most prevalent minerals in the rocks are quartz, clay minerals, and iron oxides. The metamorphism is largely regional metamorphism and generally of low grade. Contact metamorphism occurs in rocks near a granitic intrusion. A steep gradient is visible from low-grade rocks in the synclinorium to huge batholithic granites in the arena, indicating that metamorphism intensifies with stratigraphic depth and proximity to granite intrusions.