Improvements in logging methods for mineral exploration

The aim of the study was to evaluate the possibilities of well-logging techniques in mineral exploration. After the development of various plotting and processing programs the techniques were applied at two test sites in Brittany. The parameters that proved to be useful for the detection of massive sulphide occurrences and the characterization of the various geological units were natural radioactivity, density (gamma-gamma), resistivity (normal array) and conductivity (Romulus), and micronormal induced polarization. The first step, which is described here, is concerned with the characterization through physical properties of the various formations that are intersected by the borehole. The second step, which will be outlined in the conclusion, consists in the development of borehole geophysical methods to detect an orebody that has not been intersected by drilling. Section headings are: data acquisition and means of processing; experiments at Breton test sites; identification of rocks from their physical properties; Romulus electromagnetic induction probe; conclusions and further developments. (author)