Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 66. (Budapest 1974)
Embey-Isztin, A.: Petrochemistry of the dike-rocks in the Velence Hills (Hungary)
ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNGARICI Tomus 66. Budapest 1974. Petrochemistry of the Dike-Rocks in the Velence Hills (Hungary) By A. EMBEY-ISZTIN, Budapest Abstract — The established constant chemical differences, especially the variance of K 2 0/Na 2 0 have strengthened the view that the fine grained and porphyritic aplites are products of two different genetical acts. The granite porphyries represent a more sodic and basic differentiate wich is supposed to have developed by early crystallization of potassium-rich feldspar and subsequent crystallization of sodium-rich feldspar along with mafic minerals in the granitic magma. — 7 figures. Recently a number of chemical analyses of the dike-rocks have been completed by GY. PITTER and M. EMSZT. Additional analytical data of earlier papers (JANTSKY 1957, VENDL 1914, GOKHALE 1965) have also been used in the petrochemical calculations which constitute the subject of this paper. The usual calculations such as NIGGLI values, CIPW norms, and the standard cell of rocks (BARTH 1952) have been carried out by the electronic computer at the Eötvös Loránd University. For the opportunity of using the program my thanks are due to lecturer GY. BUDA. Basic dike-rocks These rocks are very subordinate in the Velence granite area. Their detailed and reviewed description is given by EMBEY-ISZTIN (1972). On the basis of the calculated NIGGLI values as compared with those of the extreme acid end member of the spessartites given by NIGGLI (1923), one may realize that the Sárhegy dikerock is almost identical with it, whereas, both the Székesfehérvár quarry and the Csala forest dike-rocks are quite different from any rock type in the lamprophyre family (Table 1). Table 1. NIGGLI values of the basic dike-rocks. acid end member (NIGGLI 1923) Sárhegy Csala forest Székesfehérvár quarry si 195 196 273 296 al 31 32 37 46 fm 30 30 25 19 c 21 18 11 9 alk 18 20 27 26 total 100 100 100 100 If we draw the differentiation diagram after NIGGLI (Fig. 1), one may see, that the chemical composition of the dike-rocks progressively approaches that of the Velence
