Integration of Geophysical and Satellite Imagery Data From the Alto de Ligonha Pegmatite Fields, Northern Moçambique: Implications for the Control of Mineralisation

Major parts of Mocambique were flown a few years ago to acquire high resolution magnetic and radiometric data. It has been since then the intent of the National Geology Directorate of Moçambique to interpret these data generating value-added maps that are easier to use by the exploration and mining industries than mere airborne geophysical grid data and maps. The National Geology Directorate of Moçambique and the Council for Geoscience have joined with the financial support of the National Research Foundation of South Africa to conduct an example study case in the Alto de Ligonha pegmatite fields, northern Moçambique, with a special view to support the small scale-mining sector of the region. Analysis of the airborne geophysical, satellite imagery and geology data, in combination with ground geophysical data acquired over specific mineral showings, reveals that the occurrence of pegmatites is mostly confined to amphibolitic gneiss, which is part of the meso-Proterozoic Namama Thrust Belt. Generation of the respective value-added map was achieved using crisp exploratory K-means clustering of the airborne geophysical data. The map is the result of clustering 850,000 four-element samples (Th- and K-surface concentration, apparent magnetic susceptibility and the vertical magnetic gradient) into a number of classes. It clearly enhances the outcrop area of the amphibolitic gneiss where the occurrence of mineralised pegmatites is the most probable. The automated integration of airborne geophysical data using the well known K-means algorithm proved to be a fast, objective and effective tool to generate a value-added integrated map. The experience made in the Alto de Ligonha pegmatite fields encourages the adoption of this methodology over other parts of the Moçambique Fold Belt. This makes it an integral part of geological mapping ongoing in the country.