Geological Mapping Project Report Of Area I , Igayaza-Isingiro District
Abstract
The geological mapping of Igayaza village was from 31st to 8th March 2022 where we travelled to Isingiro
district in western Uganda. The major aim of this field mapping was to train students to obtain hands-on
experience in field geological mapping activities from field preparations to geological written report and
practically learn field geological mapping and field data collection techniques and procedure. The methods
used after field trip include laboratory petrographic analysis and interpretation using a microscope,
structural data analysis and interpretation using stereo net software and use of ARCGIS to digitize and
draw cross sections from the map.
This looks at the study of the general geology, stratigraphy, structure, petrography and metamorphism of
the K-A system in southwestern Uganda as the northern extension of the kibaran mobile belt.
Isingiro area is relatively low to medium in elevation. Most of the areas in Isingiro district Uganda covered
by the conspicuous Karagwe-Ankolean system which is part of the Kibaran belt of Central Africa system
of rocks on which the geologic mapping exercise was done. The mapped area (Area I) lies between UTM
coordinates of Eastings (250000-252000) and Northings (9915000-9917000) in Nyakigyera sub county,
Isingiro district. It borders Igaharo to the East and Kabingo to the South, and covers 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, this Isingiro region and surrounding area areas belong to
paleoproterozoic geology of Uganda under Rwenzori fold belt and this is where we find karagwe-Ankolean
system of rocks in Uganda. The major structures encountered in this area includes joints, bedding planes,
faults, folds and minor structures are quartz veins, crenulation cleavage. The Gayaza Synclinorium is a
typical example of a cross fold with the axis plunging to the southwest at a small angle within the Karagwe Ankolean rocks of SW Uganda. The fold is about 6km across and is preserved as a topographic high
towering over the adjacent 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 analysis of the thin sections indicates that most common 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 adjacent to granitic intrusion. From rocks of very low
grade in the synclinorium, a steep gradient is obvious towards large batholithic granites in the arena hence
the metamorphism increases with stratigraphic depth and with proximity to the granite intrusions.