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

average thickness may be put at 110 centimetres. At some points, the Károly vein is inflated up to 6 metres' thickness. — On the surface, the veins are noticed by blocks and boulders of variable size of banded gangue quartz. Continuous vein crests of some length are unknown. The distribution of gangue quartz occurrences on the surface suggests the presence of further, hitherto undetected veins. However, in the mine there were found veins whose presence is not indicated at all on the surface, so that the further proceeding of the galleries may yet yield agreeable surprises. Structure of the veins, variation of ore content along dip and strike. The change of the veins along their strike may be studied favorably in the main gallery, disclosing them almost in their total length at a level of 400 metres above sea. The undisclosed sections will hardly yield workable ore, as around the ends of the galleries following the veins the latter either thin out, become poor or entirely sterile, or split and fan out. The structure of the veins is intensely variable. There occur all kinds of transition between symmetrical banded structures and coarse brecciated fissure fillings. Banded structure is most common, the bands of a given mineral generation having a thickness of 0,1 to 5,0 centimetres. The close-spaced thin bands of quartz alternating with ore represent a characteristic hydrothermal vein structure. Part of ore occurs in scattered grains of variable sise rather than in continuous bands. Within a given band of ore minerals the grain size is fairly constant. Part of the banded fissure fillings indicate open fissures, undergoing further distension in the course of ore genesis, so that the minerals making up the vein were able to grow unhampered on both walls of the fissure. Phenocrysts almost invariably occur on the margin (oldest part) of the vein, or in the genetical center of the same. The banded vein structure is almost always asymmetrical, i. e. the bands of identical age and substance on opposite points of the vein are of different thickness. Consequently, the genetical and geometrical centre lines of the veins do not coincide. It is a general observation that in case of inclined veins the bands of both gangue and ore situated above the centre line are better-developed than the corresponding opposite ones. Therefore, in the case of veins of simple, one-phase filling the youngest mineral generation is situated off the centre. However, in most cases the situation is not so simple as all that. The fissures, filled up almost entirely, were repeatedly opened by tectonic movements, along the plane of some of the older mineral generations. In the parts of the vein, formed in several phases after repeated opening, it is futile to seek any symmetry. — In the course of ore genesis the fissures were sometimes compressed instead of being distended. In such cases the previously formed fissure filling was crushed and the friction breccia formed in this way was incrusted and cemented by the hydrothermal agents into a highly variable, brecciated, cockaded ore rock. In building up the fissure fillings an important part is played by the host rock, the horses of which sometimes make up a considerable part of the veins. The latter are further characterized by frequent cavities whose vertical dimensions may reach even 15 metres. For some of these cavities a formation by subsequent leaching could be established. They were originally filled by a bigger amount of host rock, kaolinitized and finally washed out by descendent waters. Another part of cavities was formed by cleavage of the veins subsequent to mineralization. In the mineral filling of the veins the most important part is played by quartz and its varieties. Of these, micro- or cryptocrystalline, massive gangue