Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 56. (Budapest 1964)
Csalogovits, J. I.: The non-magnetic derivation of Atlantic and Mediterranean rock-provinces and their connection with orogenic metamorphism
According to his assumption the heat effect of the magma produces partial steam-pressure in the sediment where a partial pressure-gradient having an opposed direction to that of the temperature gradient may be formed and it presses part of the steam into the magma. The essence of the genesis is the water assimilation following from the steam pressure induced in consequence of the heat-effect. The steam resp. steam pressure necessary for water assimilation depends on the heat capacity of the melt, the porosity "of the country-rock, its water-contents as well as the conductive and convective thermal conductivity. From the thermodinamical consideration of the principle it follows that within the relatively short period of the cooling only a marginal deformation can arise because - although the water moving in the deposit may move according to the partial pressure gradient (effusive effect), in the melt, however, only according to the concentration gradient (diffusive effect). Here the moving of the material is secured by the thermal effect of the magma, which is proportionate to the specific heat and the volume of the melt. With a view to the fact that the flow of the material is going on across the boundary surface, it may easily be understood that the specific surface of the magma body represents a decisive factor of the process, and so does the cooling speed too which factor is also in proportion with the specific surface. If within the length of time indicated by the time-derivate of the flux which occurs during the cooling of the melt that cross-effect takes place at all, which is determined on the side of the magma by the water diluting capacity and the diffusion speed, its effect — owing to the connexion of the mentioned factors — is only marginal and not regional, because a big specific surface results in a quicker cooling, whereas a small specific surface shows a poor flow of material. The amount of exitheat during crystallization and the length of time required for the cooling is by no means sufficient for the formation of a regional diffusion of a great extent, because only a very small part of the exit heat can be used for steam mobilization of a negative direction, when taking into consideration on the one side the conductive thermal flow, and on the other side the high specific heat of the water. In our opinion the flow of the material in an orogenic system which is formed as an effect of thermic pressure, in magnitudinal order it may not even approach the measure of material flow which is brough aboutby the tectogene pressure gradient of the orogenic metamorphosis, and which occurs, by means of the orogenic compressive forces in the volume of that part of the crust which is being considered. Furthermore the thermically induced transvaporisation may form marginal deformations and metavulcanisation of a chlorite-calcite character, but it does not give any answer to the question of alkaline migration. The above mentioned examinations of BARTH are convergent with the LAHN-DiLL-type transformation of submarine lavas (H. J. RÖSLER), considering naturally the spilitization as a subsequent epigenetic effect formed post-genetically by way of halmirolisis. at which the water assimilation is indicated by primary chlorites which are formed instead of maphitic silicates, and the thus liberated Fe and Si surplus may form sedimentary iron ores by an exogenous chemical and biogenous way. In rocks formed this way, however, no alkalinity can arise syngenetically, only post-genetically in the course of albitization following the cooling phenomenon or else halmirolitically. If, however, we consider the water contents of some basic alkaline rocktypes, then on the one hand it may be seen that here the aqueous alkaline phase Na-Si0 2 -H 2 0 Ca-Si0 2 -H 2 0 appears as an indepent zoolite-phase, respectively also in alkaline amphiboles and biotite, and the water content in these rocks is by far more than may be derived by primary magmatic way from basalticalcalo-basaltic melts, taking of course into consideration the poor water diluting capacity of the basic melt.
