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

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

20 A. EMBEY—

IszTiisr fabric ("Schriftgranit"), then granophyric ones (Plate I Fig. 1, 3). Transitions of all kind exist between graphic and granophyric fabrics as well as granophyric and normal granitic structures. In Fig. 4 (Plate I) an intermediate stage of graphicgranophyric structure is beautifully revealed, while that of the granophyric-normal granitic structure is to be seen in Fig. 3 (Plate I). All these facts — the haphazard •distribution of graphic-granophyric parts, the occurence of granophyric quartz both in Ä"-feldspar and plagioclase, the transition phenomena of different structures Pig. 1. Relative positions of granophyric quartz grains compared to the host iv-feldspar. Dotted lines representing fissures in quartz — speak for a metasomatic origin of the micrographie structures viz. they can be regarded as evidence of corrosion and replacement of feldspar by quartz. Some more proofs of the replacement of feldspar by quartz can also be mentioned. Thus small relics of feldspar (in optical continuity with the surrounding feldspar), as well as former inclusions of feldspar, especially fringes of mica, are frequently encountered in granophyric quartz. In Fig. 1 (Plate II), it can be seen that the lines of small inclusions of feldspar continue also within the quartz, and in Fig. 2 (Plate II) a thin potash feldspar "tongue" becomes narrower and narrower within the quartz. Thus, at the same time, it becomes similar to the lines of inclusions mentioned above. It can therefore be deduced that the place of quartz was formerly occupied by feldspar. The same conclusion can be drawn from Figs. 3 -4 (Plate II),