Physical Theory of Generation, Upward Transfer, Differentiation and Explosion of Magmas

Abstract

A sequence of stages of generation, upward transfer, differentiation, and solidification of magmas is studied in its physical aspects. It is assumed that the parental basaltic magmas are generated at a few hundred kilometers depths from the surface during some stages of terrestrial evolution. The generation of magmas is considered as the cause of tectonic activity within the crust and the upper mantle. A stability of molten layer under various physical conditions is studied. If the rate of convection W within magmas is smaller than 0.01cm/year the magmas degenerate in situ. On the contrary they are transferred toward surface reserving their mass for W 〓 1cm/year. For W～0.1cm/year the molten layeres are floating upward with decreasing mass-and disappear at some depths. It might have a connection with the low velocity layer confirmed in seismology. When the initial thickness of magmas is greater than 200km, they approach the surface even for W～0.1cm/year. Differentiation of magmas accompanted solidification is also studied. An albite-anorthite binary model is supposed and variations in temperature inside and outside the magma reservoir is calculated. A life of sheet magma of which thickness is 1km is nearly a hundred thousand years when it is situated at depths from the surface of the earth. A life is reduced to half when situated close to the surface. The average solidification rate is of the order of cm/year.