地球化学的に見たマグマの生成および消滅

抄録

Theterm “magma” as a chemical system is used to include all naturally occurring mobile rock matter that consists in noteworthy part of a liquid phase. Formation of magma is caused by heating or decreasing of pressure, and extinction of magma is caused by cooling. End products of fractional crystallization of magma by cooling include not only the igneous rocks, but also a gas phase and possibly a watery solution. The chemical properties of the original silicate magma in the Earth derived from V. M. Goldschmidt’s hypothesis and the characteristics of the magmas formed successively in the Earth from H. C. Urey’s hypothesis are estimated from geochemical point of view. The quantity of the granite magma derived from the original silicate magma is very small, and the large amount of basic rocks in the deep place as far as more than about 1000km of the Earth is indispensable for the genesis of the granite shell in the surface of the Earth. Along with the formation of the granitie magmas in the surface of the Earth a large amount of chemical elements of the residual magma also is collected in the Earth’s crust.