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

ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNGARICI Tomus 56. PARS MINER ALO Gl CA ET PALAEONTOLOGICA 1964. The non-magmatic derivation of Atlantic and Mediterranean rockprovinces and their connection with orogenie metamorphism By J. I. CSALOGOVITS, Rudapest The denomination of Atlantic and Mediteranean province given by NIGGLI is the collective noun of magmatic rocks having a higher alcalinity than the normal pacific structure. According to the increasing silification degree, NIGGLI dérivâtes the sodium type Atlantic rocks from the Theralite-F.ssexite-FoyaiteEvisite soda.alkaline magmas, and the potassian-type Mediterranean rocks from the Missourite-Monzonite-Syenite-granito-syenite magmas. Of course such a juvenile conception of the alcalinity tends only to retard the genetic derivation of alkaline rocks, because it remains to be an open question how the Pacific, Atlantic and Mediterranean magmas are interconnected genetically. On this line opinions are not clear-cut. R.A. DALY explains the alcaline magmas to be melt-lime assimilations of a Pacific composition in which the dissolved lime-material reacts in his opinion by forming a basic plagioclase with silicatemelts, then it detaches itself from the melts by means of gravitative differentiating and forms an alkaline rest-magma. This conception, however contains a lot of difficulties. The material and heat necessary for the melt as well as the increase of viscosity in consequence of temperature decrease, excludes the forming of gravitative differentiation ; neither does it give an answer to the question of the separation of alkaline magmas into Atlantic resp. Mediterranean provinces. Apparently that more up to date form of this principle of gravitative derivation is the differentiation according to the ion-gravity (E. SZÁDECZKY -KARDOSS). Although this is in principle fully in accordance with the previous genetics, it contains a number of contradictions. Tn a weak gravitative field the differentiation which occurs within the period of cooling, in other terms the gravitative ion-diffusion, would not cause such a heterogenity at which — even if taking into consideration the expected effect of the non-mentioned thermal diffusion - the Na

4 of an ion gravity of 5,83 and the K+ of an ion-gravity of 3,97 would differentiate of Ca+ + of an ion-gravity of 8,04 (and from one another) in such a manner as to bring about alkaline magma provinces ; the less so when Fe + + of an ion-gravity of 23,31 resp. Fe + + + of an iongravity of 44,29 do not differentiate in this way, but contrary to this assumption with a higher ion-gravity in accordance with the higher oxydation degree into alkaline rock types of adequate silification degree proper to the Pacific types. Considering the other side of the question, there remains the non-juvenile conception of the alkalinity. With a view to the fact that the foyidic, resp. zeolite components of alkaline rocks may also be connected with sodium or potassiummetasomatism of the post-genetic cooling (spilitization, fenitization, adinolization etc.), and these, however, can be distinguished from the primary mineral associations crystallized from the melt, and only that question remains to be 2 Természettudományi Múzeum Évk. 1964. - -