Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 50. (Budapest 1958)
Kaszanitzky, F.: Genetic relations of the Pátka-Kőrakáshegy ore occurrence, Velence area, North Central Hungary
The individual blocks were then compressed and that is why the individual parts of the „dikes" occur in a tectonically jammed-up position. In this way parts of originally different level could have been brought side to side, which would account for the variability of the mineralization changing in the galleries almost step by step. In the opinion of the author the rise of metalliferous solutions was not restricted to any of the fault systems. Their rising has taken place, according to evidence observed in the disclosures, mostly along thin, nearly vertical fissures. That is why the zones of richer ore content known at present are of this kind. The intensity of tectonic movements subsequent to ore mineralization must have been much smaller than that of the phases prior to the same. The granite cone containing the ore deposit is the shape of an inverted funnel whose width is no greater than 200 metres on the upper level. The investigators previously studying the area (B. J a n t s k y, J. Kiss) have regarded it as a compressed granite block. In the opinion of the present author this character is restricted to the upper parts of the rock body. In the lower levels it cannot be demonstrated. According to J. Kiss the funnel-shaped rock of the Kőrakáshegy is tapering downwards. The disclosures of the lower horizons have failed to corroborate this assumption. Ore genesis. The mineral assotiation of the occurrence in rather monotonous. Beside predominant sphalerite there occur smaller amounts of galena, dispersed grains of tetrahedrite and chalcopyrite as well as the oxidation products of the above named minerals. In all of the three levels sphalerite is the predominant ore mineral. It generally occurs in an irregular zig-zag pattern of massive veinlets of 1 to 2 cm width around the blocks of the quartz breccia, cementing, as it were, the fragments of the same. No phenocrysts have been found. Sphalerite also occurs in the form of isolated grains of 1 to 2 millimetres' size bedded into the silicatic material of the fissure filling. Lastly, the dark silicic material containing Zn which has already been described above contains the ore in very fine, possibly colloidic dispersion. Wurtzite and „schalenblende"-like modifications are lacking. Beneath the microscope sphalerite exhibits a lively yellowish to reddish brown internal reflex. Because of the intense internal reflex the grains sometimes show a weakly anisotropic character. The grain size of the ore crystals is almost entirely homogeneous. From the crystal outlines obtained by structural etching a dodecahedral development of the individual crystal grains may be concluded. On some occasions twinnig was also observed, producing composite polylamellar twins. Sphalerite contains some iron : however, the infiltration of iron ions into the lattice has not been significant. The texture of the ore is indicative of intense tectonic deformation. In consequence of this the greater sphalerite bodies have fallen apart into a shapeless sprinkle of small angular detritus, the space between the individual grains being filled by silica and subsequent ore minerals. Some of the precipitated sphalerite was replaced by ore minerals of subsequent precipitation and especially by quartz. Silicic acid has invaded sphalerite along cleavage planes of the rhomb dodecahedron. In consequence of this replacement there has remained no more than a skeleton-like rest of originally large sphalerite aggregates. Of the ore minerals galena, tetrahedrite, and more seldom chalcocite and chalcopyrite take part in replacing sphalerite.
