Radioactivity measurements in the Kirkland Lake Area, northern Ontario

Abstract

The measurement of the radioactivity of 136 rock samples within and around the Round Lake batholith near Kirkland Lake, Ontario, shows a regular increase in radioactivity from south to north. This is believed to be due to the northward plunge of the batholith and the migration of radioactive elements towards the top surface. This agrees with previous work by Keevil and Ingham on other batholiths.This evidence of the rise of radioactive elements suggests that the radioactivity of the crust as a whole may be much less than that determined from samples taken on its surface. Using values for the lower part of the batholith as representative of the granitic layer it is estimated that at Kirkland Lake 40 per cent of the total heat flow from the interior of the Earth may be accounted for by the radioactivity of the rocks in the top 36 km of the crust.It is also assumed that erosion has removed the more highly radioactive material from the Earth's surface and deposited it as sedimentary, heat‐producing shelves or dumps along the edges of the continents. These dumps may have determined the location and their heat may have assisted in the formation of marginal mountain ranges.