Abstract provided by author:
The main application of ARC/INFO has been in the conversion of the paper analogue map of the mapping area to a digital format in line with the Geological Survey of Namibia's long term objective of establishing national geological and mineral occurrence databases. The map production component of the study is also in line with the corresponding shift towards putting an automated map production system in place
The Swakop Group metasedimentary sequence consist of the Arandis Formation (schist-calc-silicate-marble) the Karibib Formation (marble dominated) and the Kuiseb Formation (schist) at the top of the sequence. The formations are subdivided into members according to the recently revised regional scheme. The syn- to late- tectonic porphyritic Salem granites and the leucogranites intrude the metasediments of the succession. Abundant pegmatite intrusions are present throughout the metasediments while quartz veins are minute and restricted. The post-Damara (Karoo) dolerites and felsic dykes are common and exhibit a NE-SW orientation. Two phases of deformation have affected the study area. The marble-cored structural domes are a characteristic feature of the area and are interpreted as Fl and F2 fold interference domes. The amphibolite facies metamorphic grade is indicated by the biotite-quartz-cordierite-K-feldspar-sillimanite metamorphic assemblage in the metapelite of the Kuiseb Formation. The presence of cordierite indicate metamorphic temperatures of 600 °C to 700 °C and pressures between 3. 5 kbar and 5 kbar
The previously unmapped subunits of the Arandis and Karibib Formations have differentiated by the combined use of image processing techniques, aerial photographs and existing geological base maps. Image processing included linear contrast enhancement, principal component analysis and band ratioing. Spectral response curves indicate the statistical reflectance of each one of the major lithological units with respect to the wavelength bands in the TM data. The linearly contrasted colour composites of bands 1, 5, 7, bands 4, 5, 7 and bands 3, 4, 5 (blue, red and green, respectively) were the most suitable for lithological discrimination. Principal components PC2, PC3 and PC4 (green, red and blue, respectively) also proved suitable particularly for the granites. To eliminate the variation in illumination of the images TM band ratios 5/3, 5/4 and 5/7 in blue, green and red, respectively, have been the most informative