The association of lead with uranium in rock-minerals, and its application to the measurement of geological time

Abstract

1. Introduction .—The study of radioactive minerals is of great importance from two points of view. Such minerals may be regarded as storehouses for the various series of genetically connected radioactive elements. In them the parent element slowly disintegrates, while the ultimate products of the transformation gradually accumulate. The analysis of these minerals ought, then, in the first place, to disclose the nature of the ultimate product of each series; secondly, a knowledge of the rate of formation of this product, and of the total quantity accumulated, gives the requisite data for a calculation of the age of the mineral. It has been shown that the disintegration of uranium results in the formation of eight atoms of helium. In 1907 Bolt wood brought forward strong evidence suggesting that lead is the ultimate product of this disintegration. In this paper it is hoped to produce additional evidence that such is the case, according to the following equation:—