Investigations of the distribution of U, Th, and K in deep profiles exposed by Precambrian doming have been presented for Vredefort, South Africa and have recently been completed for a similar structure near Sudbury, Ontario, Canada. An evaluation of the Vredefort data shows evidence of a major crustal repetition of the vertical radioelement distribution with depth. A simple explanation is that the South African basement is geochemically layered, with repetition occurring from layer to layer. This implies a sawtooth, or ''serrated'' distribution with depth.

Preliminary results from the Sudbury investigation show a rise in heat production with distance from the Sudbury Structure, corresponding to decreasing depth in the basement rocks. The repetition of the radioelement distribution observed at Vredefort does not appear in the Sudbury data. Although Th and K make a jump at nearly the same depth, the U data show no corresponding increase. U loss is suspected in the project area, affecting the overall distribution of heat production in the Sudbury basement. Given its complex history and geographic location, the material in the sample area may not be representative of the Superior Province. ¿ American Geophysical Union 1987