Landsat Remote Sensing Data as an Alternative Approach for Geological Mapping in Tanzania: A Case Study in the Rungwe Volcanic Province, South-Western Tanzania

Abstract

Rungwe Volcanic Province (RVP) is mostly covered by extrusive rocks that overlain the Precambrian basement. The use of Landsat data in this area has revealed the need of effective use of these data in geological mapping programs in Tanzania. Landsat band ratios 5/1, 3/7, 5/7 and 5/4 as well as R: G: B composite images 7:4:1, 7:5:4, 1/3:5/7:3/5 and 4/5:6/7:4/6 played an important role in identifying different rock types in the study area. Ratio images managed clearly to distinguish between mafic and felsic rocks whereby two lithological blocks were identified, Block 1 covers a combination of intrusive and metamorphic rocks while Block 2 is dominated by extrusive rocks. Composite images went further to the discrimination of individual lithological units in which different rock types were identified, example phonolitic trachytes, basalts, tephrites and granitoids. Vegetation overlap problem was cleared up by results from classification in which the thick vegetated areas were discriminated. Hence, results from Landsat data analyses showed clear lithological correlation between Landsat images and the available geological map in the study area. Apart from these data to show that they are effective in geological mapping, the performance showed by Landsat data suggests they can substitute geophysical data which are relatively very expensive.

Tanz. J. Sci. Vol. 37 2011, 26-36