A geologic mapping project report of Area L, in Kabingo- Gayaza Isingiro District, Western Uganda
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The mapping exercise (project) which was carried out in Gayaza area, Isingiro district in Southwestern Uganda. The project was aimed at equipping geology students with field geologic mapping skills, data collection, processing and dissemination. The entire exercise involved collection of field data, data processing of the collected data and reporting of four main areas; stratigraphy, structures, petrography and metamorphism and regional synthesis. The area is generally characterized by a hilly topography with intervening narrow and broad low-lying areas which could have evolved due to differential weathering. It is also characterized by parallel and dendritic drainage and savannah vegetation. Settlement in the area is generally linear. Relief in the area is generally high making it generally difficult to access. Land use is dominantly agriculture and quarrying stone for construction material. Argillaceous and arenaceous rocks (shales, phyllites and quartzites) are characteristic of the area except for parts of granitic intrusions (arenas). As such, the area is placed in the middle part of the Karagwe-Ankolean system. The major geologic structures encountered in the area are bedding and joints/fractures. Faults, folds, boudins, lamination are taken as minor structures. Beds in the study area dip to the SE and NW with low dips at the axis of the Gayaza syncline and steeply away from the axis of the syncline. The joints show two preferred trends in the NW-SE and NE-SW in the entire area corresponding to the regional and cross fold trends of the area and moderate to steeply dipping. Petrographically, the study area is underlain by quartzites, siliceous, ferruginous and somewhat micaceous-shales. Metamorphism in the study area is generally regional (due to burial) of low to very low grade. Dynamic metamorphism in fault zones and metasomatism in areas near the granitic intrusions are also evident. Metamorphism increases in grade towards the base of the unit and with increasing proximity to the areas of granitic intrusion (arena). The area is part of the Karagwe -Ankolean system which is part of the Kibaran belt as revealed by the structural and petrographic analysis and from the granitic intrusions and the tin mineralization areas visited during the field excursion part of the mapping project.