| dc.description.abstract | The Geological mapping exercise was carried out in Igayaza, Isingiro district, western Uganda,the area lies on a generally rugged topography with intervening valleys, steep gorges, flat topped ridges and rounded hills. The aim of the field was acquainting us with skills in geological mapping. The mapping exercise involved conduction of field work based on surface geological mapping in which the study area was traversed and a mapping plan developed and various observations on outcrops made were recorded. After field work, samples were sorted and taken to the laboratory for further analysis and data acquired for structures was interpreted and analyzed. The findings were compiled with its interpretation made.
The climate of the area is composed of two wet seasons with mean annual precipitation of about 750mm to 1250mm and mean annual minimum temperatures of 12.5-15°C to a maximum of 25-
27.5C.
The rock types in Gayaza include shales, quartzites, conglomerates, phyllites, laterites, Aplites and mylonites (only found in area I). The rocks were deposited in the order of shales followed by sandstones (later metamorphosed to quartzites) which were later intruded by granites and as a result of erosion and weathering the granites formed arena structures which predominate much of the Karagwe-Ankolean system. The Karagwe-Ankolean system(1400 & 95 Ma) is exposed in Uganda, as the Northern-most extension of the Kibaran mobile belt, extending from Angola further South to Uganda in the North (Nakajjigo, 2021). It is said to terminate into the Buganda-Toro system(older) which is itself overlying the Basement Complex. Distinguishing Buganda-Toro from the Basement Complex rocks is, however, difficult.
Petrographic studies confirmed presence of quartz and clay minerals (as the dominant minerals) together with some micas, alkali feldspars and iron oxides in the rocks of the mapped area. The type of metamorphism that affected these rocks is mainly regional and of low grade evidenced by foliation and some index minerals such as chlorite. Sandstones and shales were metamorphosed to quartzites and phyllites respectively. Deep, quiet and shallow water dynamic environments of deposition were proposed due to the presence of shale and quartzites and some structures such as beds and laminations in shales.
The major structures in the area mapped include; beddings, faults, folds and joints all exhibiting two major trends; the northwest-southeast (NW-SE) trend which is similar to that of the regional folds and the northeast-southwest (NE-SW) direction similar to that of the cross foldsThe minor structures include; micro-folds, micro-faults, quartz veins, boudins, rods, foliation, lamination and mud cracks. The drainage pattern of the area is essentially structurally controlled.
No economic minerals were found but some industrial minerals of high place value such as sand, kaolin, shales and quartzite, mainly used for construction works do exist. The major economic activities in Gayaza area include: crop growing (especially matooke), animal keeping (on a small scale) and brick layering. | en_US |
