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

sidered as the tectonically displaced parts of one or several, originally contiguous, dikes. We have already pointed out the continuous transition from country rock to dike filling : that is why we seek in vain a fault plane indicating the dislocation in most of the cases. Part of the faults plotted in the mining maps of the occurrence are rather explanatory in nature, by the assumption of which the investigators hoped to present the quartzite blocks as displaced parts of an originally continuous dike. There is no denying the fact that there have been phases of tectonic displacement, important in size even as related to the bulk of the occurrence, during and after the formation of the ore deposit. This movement has not, however, broken up pre-existing dikes ; its result has much rather consisted in grinding the quartzite material and dislocating part of the same. The faults along which the displacement took place are to the most part situated in the country rock. The quartzite material and the country rock have suffered the dislocation side by side. Tectonic features. The tectonic processes moulding our area have been rather intense. The faults represented may be, according to their strike, relegated to two groups. The more ancient one is of north-north-easterly, the younger one of north-westerly strike. The tectonic contact of the granite and slate is parallel to the first set and the strike of the aplite veins occurring in the area also follows this direction. The quartz material found in the tunnel was most probably also deposited along this same strike and the silicic veins encountered on the surface likewise belong to this set. Considering their strike, the latter indicate the final stage of magmatic activity and are thus younger than the dikes parallel to the strike of the mountain system. The origin of this set of faults may be ascribed probably to the Saalic period of orogeny, or to an even earlier one. However, in treating this problem we are restricted to mere guesswork. The rise of mineralizing solutions was subsequent to, rather than contemporaneous with the formation of the quartzite material of the ,,dikes". The tectogenesis generating the fault system of north-westerly strike has resulted in the grinding of the quartzite material filling the fissures of the granite mass and in fracturing the ore body. Its age is unknown but displacement along this set of faults is assumed to have occurred in several steps ranging in age from late Mesozoic to Pannonian. The youngest of these have traversed the Pannonian sediments proper. It seems that gaping fissures have only been formed along the first set of faults, and even here only temporarily, while the second set of north-westerly strike mostly featured closed fissures. Beside the faults of this strike there are but a few fluorite-bearing quartz veinlets belonging to this set in the disclosures under day. The ore-bearing dikes of the Kőrakáshegy area have been displaced by the faults out of their original position. It is impossible to reconstruct the slip of the displacement as there is an enormous number of faults of variable size in a great diversity of directions. However, slip may be considered to have been important as related to the size of the occurrence. However, in our opinion, the strike-slip of the faults has not exceeded 10 to 15 metres. In consequence of the dislocation a grinding of the quartzite material was effected, yielding the opportunity for the brecciating mineralization Í characteristic of the occurrence, whereby subsequent solutions loaded with metal ions have cemented the fissures of the breccia with ore minerals. It could be established that the reiterated tectonic movements have broken up the granite in a very complicated manner.