Geological mapping of the Penamacor - Idanha-a-Nova zone (Central Portugal) by digital classification

The Penamacor-Idanha-a-Nova zone (Central Portugal) is characterized by the presence of some plutons of granite-granodiorite-diorite composition, intruded in a metasedimentary sequence of schist and greywacke with some intercalations of quartzite and slate. The intrusions display an internal zoning due to the variation in composition and/or grain size. In general, the zone presents a scarce vegetation cover that reaches a minimum during summertime. For this study we used a set of winter and summer images of the TM system of Landsat5 that were used to digital classification. Considering the existence of geological cartography of the area, we used supervised classification by different methods like minimum distance and maximum likelihood. They were also considered empiric techniques of classification as scattergram or equal density analysis. We obtained satisfactory results in the differentiation between the metasedimentary sequence and siliceous rocks and in internal zoning of plutons. The geological mapping offers a support to land ordering. For these reason, the speed and efficiency in the application of these techniques to satellite images offer important economic and scientific advantages.