MEASUREMENT OF RADIOELEMENT CONTENTS OF ROCKS OF UGEP, SE NIGERIA, BYGAMMA-RAY SPECTROMETRIC AND INSTRUMENTAL NEUTRON-ACTIVATION ANALYSIS TECHNIQUES

A combination of gamma-ray spectrometry and instrumental neutron activ ation analysis is adopted in the quantitative evaluation of the three major radioelements (U, Th and K) concentrations in some rock samples collected at previously delineated radiometric anomalies (Geological S urvey of Nigeria, 1976), in the Ugep area of the Lower Benue Region of Nigeria. A preferential enrichment of Th to U and K is observed in mo st samples analysed, with U/Th ratios ranging from 0.11 to 0.25. K con tents are fairly normal in some samples analysed, with Th (ppm)/K (%) ratios ranging from 2 to 5. Anomalous Th/K ratios, Th (ppm)/K (%) rati os ranging from 2 to 5 up to 16, were obtained for samples from those areas identified in the airborne survey maps as ''Th-anomaly zones'' ( Geological Survey of Nigeria, 1976).