Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 66. (Budapest 1974)

Embey-Isztin, A.: Petrochemistry of the dike-rocks in the Velence Hills (Hungary)

Table 4. Chemical composition of the different rock types Granite porphyry, Sukoró Granite porphyry, Pátka Aplite, Mélyszeg (dilatation -injection type) Aplite, Székesfehérvár quarry (replacement type) Si0

2 67.30 68.75 78.72 76.78 Tio; 0.43 0.42 0.04 0.03 A1

2

0

3 14.72 15.31 11.49 12.67 Fe

2

0

3 0.53 1.34 0.29 0.53 FeO 2.40 1.81 0.06 0.05 MgO 0.88 1.06 0.20 0.50 MnO 0.08 0.08 0.02 0.01 CaO 2.29 0.56 0.22 0.11 Na

2

0 3.85 4.22 0.32 3.85 K,0 4.62 4.51 6.69 5.11 + HÖO 0.73 0.91 0.80 0.32 -H;O 1.09 1.08 0.88 0.38 0.15 0.16 0.03 0.04 CO, 0.90 0.00 0.00 0.02 Analyst: GY. PITTER. In the author's opinion the fine-grained aplite is an isovolumetric alteration product of the granite. In this case the composition of the standard cell of the granite and aplite can yield useful information about the exchange of material during the metasomatism. As is well known all calculations are referred here to a volume of 160 oxygen anions. The composition of the standard cell for the granite and aplite is: Granite Considering the difference between the two rocks by subtracting the one from the other we can see that granite passes into aplite : By adding 3.3 Si 0.5 Na 3.8 cations total : representing 13.7 valences total : representing By subtracting 1.9 Al 0.8 Fe 0.1 Mg 0.3 Ca 5.4 H 8.5 cations 13.7 valences It is worth mentioning that a remarkably small fraction of the rock (less than 5%) need migrate in order to effect aplitization. Fig. 6. shows that aplites of dilatationinjection type fall into the stability field of orthoclase without exception, therefore, they are potassic rocks as defined by BARTH (1952). For that reason, it is obvious