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

the feldspar laths. The ground mass sometimes exhibits ore particles. These rocks are of a macroscopically black, greenish, grey, violet or bluish colour. Between them and the pyroxene andésites in the stricter sense there occur all kinds of transition. In these the size of the feldspars gradually increases to 1 to 3 millimetres. The plagioclases exhibit zoning, and melanocratic ingredients — hypersthene and augite — are increasingly frequent. Hypersthene is generally digested and encrusted by fresh augite. The rocks of Points 2. and 3. occur in a relatively small extension on the bottom of Szomor Creek, on the Malombérc, in Kartal Valley, Bükkszél and Csatornás. They are presumably parts of an older, subvolcanic rock body, re-worked by assimilation. 4. "Inclusion-rich" pyroxene andésite. It occurs between the „main Mátra andésite" and the types lacking dark ingredients, mentioned above. Macroscopically as well as under the microscope it is much resembling the pyroxene andésites. The sole differences are its somewhat lighter colour and the somewhat smaller grain size of the porphyric inclusions. It is characterized by that it contains a great number of inclusions of the above-described rocks. This type of rock may be considered a lateral facies of the Mátra pyroxene andésite. 5. Hypersthene andésite, augite andésite, hypersthenic augite andésite. Between them, these rocks constitute the "Mátra andésite" and maybe regarded as varieties of the same. There are continuous transitions between these types so that mapping them apart sometimes presents insurmountable difficulties. When fresh, these are rocks of massive porphyric texture, with color ranging from dark grey to black. Porphyric ingredients are plagioclase, hypersthene, augite, biotite, and pyrite. The ground mass of the rock is variable. It is greyish brown, sometimes colourless. There is few glass, the feldspar laths almost touch each other. The texture of the rock is pylotaxitic, sometimes hyalopilitic. The predominating ingredient is feldspar. It forms authomorphic flakes of 2—3 millimetres' size in the ground mass. It is frequently of a zonal structure. The feldspars are of oligoclasic to andesinic composition. Glass and hypersthene inclusions are frequent. The feldspar of the ground mass seems to be somewhat more acid. Of the porphyric melanocratic ingredients hypersthene is most frequent, in the form of 3—4 millimetre size crystals. It is rarely fresh. Generally it is altered or in train to alter. The crystals are frequently decomposed or altered, respectively into bastite. Augite is less frequent than hypersthene. It forms generally small stocky columns of 1—3 millimetre height. It frequently occurs in the form of a web of unaltered crystals surrounding altered hypersthene. Biotite is quite scarce and is in most cases entirely decomposed. Pyrite, chlorite, limonite and opal occur as secondary minerals, formed by the alteration of the primary ones. 6. Andésite agglomerates. The space between the lava bodies consisting of the above described rocks is filled by agglomerates of the same. Predominating on the surface, they are much less frequent in the mining galleries. In their place the endometavolcanites gain importance. The agglomerate is generally coarse, with bombs of varying size. Tuff material shows kaolinitic alteration in large areas.