| Abstract: | Experimental control in the classical igneous petrology is based on determination of the equilibrium conditions of simple — mostly 1–4 component — system. The statements based on such experiments are valid for rock products chemically not influenced by active environments. For elucidation of processes between geochemically active volatile-rich country rocks, high pressure and high temperature experiments oncomplex systems containing such active rock samples, too were performed. High pressure bombs were constructed with long and narrow container, allowing to investigate the selective migration of elements between different rock samples, even by temperature slope within the container. In these bombs different igneous, sedimentary and metamorphic rocks in contact at different temperatures and pressures were investigated. P-t relations and stability fields of different mineral facies cannot be exactly determined by phase diagrams of simple uni- or multicomponent systems, because they depend on other components and on the environments, too. The new complex experiments, however permit to assess directly the stability fields of the mineral facies. The data obtained proves that an intense selective migration of the volatiles take place even in solid samples at 550° C, in some rock associations already at 250° C, if there is a concentration gradient of volatiles between the samples. Selective migration proceeds following the principle of transvaporization, i.e. towards the partial pressures — chemical activities — of the mobile components and following the sequence of their ionic potentials. In this way, different hypomagmatic and metamorphic rocks are produced. The new kind of experiments shows that — opposite to the approaches of the classical igneous petrology — a high grade contamination of the ascending magma is possible. Contamination proceeds by transvaporization. Assimilation — Einschmelzung — mostly plays an insignificant role. Gravitative crystallization differentiation operates intensely only in the higher sections of volcanic pathways, characterized by relatively low pressures and thus by low viscosity of the magma. Contamination is intense if the ascension of magma is relatively slow as it is presumable along the oblique circumpacifique or innercarpathian andesitic structural lines. In this way, basaltic magma produces andesitic to rhyolitic rocks partly abundant in volatiles. However contamination is restricted and consequently basaltic rocks are formed if magma ascends rapidly through vertical channels as it is presumably the case with the young peripherical basalt volcanics, e.g. the innercarpathian basin system. These experiments also evidence the activation process of magma by transvaporization. Selective migration of volatiles even through solid rocks is introduced by structural pressure minimum zones towards these zones, which results in the melting of neighbouring rocks and their lifting as liquid magma until volatile supply is sufficient. |
