Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 51. (Budapest 1959)
Kaszanitzky, F.: Genetic relation of ore occurrence in the Western Mátra Mountains, North Eastern Hungary
sequence (Bányabérc vein, Pelyhes vein). The veins have traversed a motley sequence of different andésites and their currence is not bound to any definite rock type, as contrary to the opinions of some former authors. However, the statistical evaluation of the data of several kilometres of galleries following the lodes has shown that there is a well-defined relation between the mineral composition, texture and structure of the veins and the nature of the immediate host rock. When situated in unaltered rock, the veins are of a massive banded structure. Most of the gangue consists of cryptocrystalline striated quartz. Amethyst is very frequent. The ore minerals occur in thin veinlets, or, especially in the lateral parts of the vein, in a loose scatter. In case the host rock is agglomerate, — or pseudoagglomerate, for that matter, — the vein is but rarely banded. Quartz is either totally absent or quite subordinate. Ore occurs in scattered aggregates of variable size or in cockades. Most of the gangue consists of intensely altered horses. These vein sections are generally rather poor in ore. The explanation of the phenomenon is presumably that the fissures in unaltered andésite have been much more stable than those in agglomerates. Through them the solutions could have passed unhampered, while the loose agglomerate was soon altered and the clay minerals and the smaller grain-size categories of the agglomerate brought about a partial or total occlusion of the fissure. The surge of the solutions was thus partly inhibited, partlv diverted sideways and that is why in such parts of the veins ore is found even at distances of several metres off the center of the vein. Tectonics The tectonical influences prior to the development of the hydrothermal vein system have generally been deleted by subsequent alteration processes. There undoubtedly occurred displacements of considerable dimensions, although it is impossible to-day to reconstruct their direction and magnitude. The dikes of cataclastic rock of 10 to 60 centimetres diameter, disclosed in a number of instances by the galleries, have preceded ore formation, as they are intersected by the ore-bearing veins. On the other hand, a tectonic zone of several hundred metres' width is crossing the northern part of the area in the environment of the Bányabérc. This zone also bears some ore locally. After the development of the Mátra Mountains the vertical epeirogenic movements of the Alföld (Hungarian Great Plain) Basin have led to the development of deep fissures of considerable length in the andésite body. It was along these that the ore-bearing hydrothermal solutions have surged. The textural nature of the veins indicates a repeated opening and closing of the fissures. According to their strike, the veins may be divided into three groups ; of 1. NNW — SSE, 2. NNE — SSW, 3. ESE—WNW strike. Of these the veins of the third group are oldest, the two other groups being of identical age. However, the age difference between groups 1, 2 and 3, respectively, is not significant. The veins are situated in something like a half circle east and northeast of Tóthegyes Peak, the main mass of the Western Mátra Mountains. Part of the veins is radial, the other, greater part tangential to the mentioned half circle.
