U, Th, K Content, Heat Production and Thermal Conductivity of Sao Paulo, Brazil Continental Shelf Sediments: A Reconnaissance Work

摘要

A reconnaissance of the natural potassium, uranium and thorium content, the radiogenic heat production, and the thermal conductivity of 80 bottom surface sediment samples collected in the Brazilian continental shelf off Sao Paulo was made. The average equivalent contents of these radioelements in an estuarine ambient were 1.21%, 1.75 ppm, and 4.29 ppm respectively, and 1.20%, 1.21 ppm, and 4.05 ppm respectively in the shelf samples. The U-234 to U-238 isotopic ratios varied from 0.60 to 1.75 with an average of 1.11, indicating that the sources for the uranium in these sediments are both terrigenous and from the sea water. An average radiogenic heat production of 0.63 + or - 0.04 micro W/cu m was calculated from the experimental concentration data. Data for the thermal conductivity measurements ranged from 0.83 to 2.51 micro W/m/deg C, with an average of 1.81 micro W/m/deg C.