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

In the interior of the sphalerite grains small isle-like inclusions of chalcopyrite will often be encountered. These small chalcopyrite bodies are partly shapeless, but some of them exhibit a triangular or bisphenoidic shape. Part of chalcopyrite was separated from sphalerite by unmixing due to cooling ; however, some of the chalcopyrite grains are more ancient than sphalerite. It may be observed that the individual chalcopyrite inclusious are attacked and partly replaced by sphalerite. Beside this chalcopyrite generation older than sphalerite there is also a younger one occurring in the form of thin veinlets filling the fissures in sphalerite. Beside chalcopyrite, tetrahedrite also appears as a product of unmixing within sphalerite. Pyrite, the latest formation, is also seen in the fissures of sphalerite. The development of sphalerite is completely identical on the individual levels. In the course of microscopic investigation there were neither textural, nor optical differences to be demonstrated between any of the sphalerite sections derived from the different levels. The only difference is the scarcity of tetrahedrite in the sphalerite of the lower levels as related to that of the upper ones. Chalcopyrite content, on the other hand, exhibite no quantitative variation of this kind. The elements Ag, Cu, Cd, Ge, As, Sb, Bi, Sn, Co were demonstrated spectrographically in sphalerite (I. K u b o v i c s, analyst). The occurrence is richer in chalcopyrite of the younger set than in that of the older one. The former usually occurs along the margin of the sphalerite grains or beside the same in the form of independent grains, aggregates or rags. These formations are throughout smaller than the average grain size of sphalerite and galena. Young chalcopyrite often replaces galena and sphalerite. It advances in thin veinlets along their surfaces of cleavage while later on the veinlets, having increased in thickness, interweave and partly digest the named minerals. Finally no more than small incontiguous spots of them remain within the body of chalcopyrite. — Young chalcopyrite is of a light yellow color. Its anisotropy becomes apparent under oil immersion only. Young chalcopyrite occurs but seldom in itself. It is usually accompanied by tetrahedrite. None of the two chalcopyrite generations exhibits any traces of variation on the different levels. As regards quantity, sphalerite is followed by galena. The latter occurs in independent spots as well as in the form of small islands within the sphalerite body. Intergrowths with sphalerite are often encountered, whereby the former tends to be replaced by the latter. Galena often forms thin veinlets. The greater grains invariably exhibit translation and undulous folding, respectively. As this is most frequent in the interior of the grains, it is indicative of a compressive stress having acted during crystallization. In the interior of galena there are beside the remnants of digested sphalerite also tetrahedrite grains of some hundredths of a millimetre in size. Older chalcopyrite is also present in the form of inclusions. Complex sulphides and silver ores are lacking. Galena of primary precipitation has suffered a partial resorption by subsequent ascending solutions. Most of the space thus liberated has been occupied by a younger gangue generation. Similarly to that of sphalerite, the texture of galena also fails to exhibit any differences between the individual levels. Nor is any oxidative effect to be observed on the sphalerite grains. The galena of the upper levels exhibits effects of oxidation of smaller intensity. Part of the galena has been trans-