Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 65. (Budapest 1973)

Embey-Isztin, A.: On the problem of graphic intergrowth and normal granitic structure

Fig. 4. Frequency distribution of 430 xenomorphic quartz grains, Aplitic microgranite (Figs. 3 -4). In Fig. 3, the positions of 200 quartz grains from samples of pronounced aplitic character, while in Fig. 4 that of 430 quartz crystals of average rock samples from the Székesfehérvár quarry, are plotted. Both diagrams show that the places of maxima he concentrically somewhere between 42-04°. Hence there can be little doubt that adjacent feldspar has played an important role in the structural orientation of xenomorphic quartz; in other words, it means that metasomatic processes must have been involved in their genesis. The same conclusion can be reached from Fig. 5. Here 75 data were sufficient to realize that certain positions predominate. This diagram contains the data of an aphte dike in the basal granite. Hence it can be said that quartz-metasomatism played an important role also in the evolution of this aphte. Although we propose to discuss aphte dikes in a separate paper, some results can be mentioned. It seems that two genetically different types of aplite dike exist in the Velence Hills. On the one hand, there is a metasomatic type, characterized by aplitic structure, replacement phenomena, coarser granite-like fabric in border zones and relics of granitic structure; on the other hand, a dilatation-injection type with an effusive-like spherulitic matrix and phenocrysts of quartz dihexahedra. The two types differ from each other even in respect of their chemical composition. In Fig. 6 it can be seen that aplites of a metasomatic type lie within the