Geological Mapping Project Report Of Area I , Igayaza-Isingiro District
Abstract
The geological mapping of Igayaza village was from 31
st January,2021 to 08th Febraury ,2021
where we travelled to Isingiro district in western Uganda. The main Purpose of this field mapping
was to enable students to acquire 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 stereonet software and use of ARCGIS to digitize and draw cross sections from
the map amongst others.
The major areas of focuses were; 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 visible 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 basically 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.
Upon the petrographic analysis of the thin sections of the samples obtained from this area, it shown
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.