ON THE GEOCHEMICAL STUDIES OF STABLE ISOTOPES (Ⅲ） ON THE ESTIMATION OF THE ISOTOPE RATIO IN THE MANTLE

摘要

Up to the present time, the questions of the chemical composition in the interior of the earth and of the isotopic ratio in those parts has been debated. It is supposed that the average composition of the interior layer of the earth resembles that of cer¬tain types of rocks and meteorites. For example, the interior may be represented by dunite, eclogite and peridotite. Or it can be represented by meteoritic compo¬sition. For any theories concerning the model composition of the interior, one might conclude that elements such as Li, Na, K, Ca, Al, and halogens are concen-trated toward the earth's surface, while S, Mg, Fe, and Ni are enriched in the deeper layer. In order to estimate the isotope ratio in the mantle, the following cases are discussed. (1) The isotope ratio in the mantle might have a composition similar to the meteoritic value. (2) The isotope ratio in the mantle might have a composition similar to the terrestrial value.