Mapping radioactive minerals using remote sensing: a case study of Mrima Hill Kwale County, Kenya
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Date
2020Author
Ondieki, Jephter, O
Type
ThesisLanguage
enMetadata
Show full item recordAbstract
Mrima hill is an elliptical carbonatite plug area of approximately 2 km across, a gazetted forest
reserve in Kwale county, bounded by 4° 29'l0"S; 39° 15 '10'’ E coordinates, 750 feet above the
sea level. The hill is covered by deeply weathered materials. Rare earth elements, niobium,
Monazite minerals and associated carbonatite rocks are known to exist in the area. The area is
classified as a high background radiation. Applications of geological remote sensing and GIS for
radioactive mineral mapping have not been fully integrated into the mineral exploration activities
of the Geological Survey of Kenya. This study employed remote sensing and Geographic
Information System (GIS) to map minerals in Mrima hill region in Kwale County, specifically
radioactive minerals, as the area has been classified a high background radiation area. In this
study, the data used was obtained from Earth explorer (https://earthexplorer.usgs.gov/) website,
with spatial resolution of 30 m, and was processed for mineral spectral signatures by using
ENVI5.3 and Arc Map 10.3 software by means of the color composite, band rationing, principal
component analysis and supervised classification.Landsat-8 OLI imagery of Mrima hill was
processed to enhance the geological features and mineral potential of the area. Band ratios 6/7,
6/5, 4/2 were assigned to RGB. Band ratio 4/2 highlighted ferric ion minerals, 6/5 emphasized
ferrous minerals, and 6/7 distinguished iron oxide minerals from carbonate minerals. In a second
technique, band ratio 6/7 was replaced with 7/ 5 in order to accentuate clay minerals with high
reflectance within band 7. Supervised classification training data were obtained using five
classes for rocks associated with radioactive minerals (carbonatite, granites, sandstone,
serpentine and shale). The classification using maximum likelihood classification was fairly
accurate and matched the radiometric and geologic map of the area, also showing an alteration
zone that coincided with the high dose rate areas. However, for areas covered by vegetation,
botanical indicators of vegetation species associated with radioactive mineralization including,
the Asparagus sp, Stanleya, Aster venustus, and Oryzopsisj species, from the Envi database, were
used to map for the presence of radioactive minerals in the study area. The use of supervised
classification method identified the following vegetation; big berry Manzanita, big sagebrush,
Mormon tea, pynon pine, specifically as associated with radioactive minerals. The classified
image was finally validated using existing radiometric data of the study area. In conclusion, this
study demonstrated the usefulness of applications of remote sensing to map minerals in general,
for application in mineral exploration.
Publisher
University of Nairobi
Subject
Mapping radioactive minerals using remote sensing: a case study of Mrima Hill Kwale County, KenyaRights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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