Radiogenic heat production in crustal quarry rocks of Ogun State, south-western, Nigeria

Abstract

Radiometric survey has been used extensively in quite a lot of fields of science, majorly for geological mapping and mineral exploration. It is used to quantify the proportion of potassium, uranium and thorium in rock and soil. Radiogenic heat production was found to be associated with the radioactive emission from the three primordial radioelements: uranium, thorium and potassium. In this study, the main objectives are to investigate the potential economic heat resource associated with the quarry rocks, delineate the contribution of the radioelements to the heat generated and possible effect posed on the workers. Thirty rock samples from ten different quarries in Ogun State were randomly collected. The rock samples were then processed and subjected to radiometric analysis for geothermal investigation. The mean heat production for the ten quarries investigated was found to range from 0.549 to 3.122 μWm−3. The result revealed that uranium has the largest contribution, with a coefficient of correlation of 83.09%, of the heat produced in the quarry rocks while the lowest contribution was associated with thorium having a correlation coefficient of 15.43%. The low heat produced was found in the shale and limestone region while the high heat generated was associated with coastal plain sand and alluvium area. The mean radiogenic heats estimated across the ten quarry stations were below the 4 μWm−3 recommended value of heat to be considered for economic importance. The result implies that heats are generated across the selected quarry stations, but were not of economic significance. This study showed that heat production varies from place to place and depends solely on the geological composition of the underlying bedrock units.