Results of the Complex Airborne Geophysical Survey in the Central African Ridge Area

Abstract

We review the results of different-scale airborne geophysical survey performed in the territory of the Republic of Rwanda. Such parameters as the modulus of the magnetic field vector, electromagnetic sounding data in time and frequency domain, as well as data from a gamma-ray spectrometer with a total scintillator volume of 32 L were continuously recorded during the flight. The software automatically performed the necessary navigation management on a real-time basis. Automated execution of flight tasks allowed to exclude an operator from the surveying process. It took only 6 months of field works to perform the survey at a scale of 1:50,000 over the area of 26,000 km², as well as detailing works. The total workscope amounted to 57,718 line km. Maps of anomaly magnetic field and its local part, apparent resistivity maps for the most informative frequency and time channels, Th, U, K concentration maps and Th-K ratio maps have been prepared for a short period of time. Based on the results of map interpretation we selected prospective sites for further study. Detailed airborne survey was performed for 5 sites, and ground geological and geophysical survey was performed for 3 sites. Based on the detailed survey results we selected new local objects associated with quartz-magnetite veined mineralization, dyke bodies, and mafic rock intrusions. Multiple pegmatite intrusions were identified. The information about magnetic, electrical and radiometric characteristics of rocks allowed to reliably classify the identified anomaly objects.