Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 57. (Budapest 1965)
Csalogovits, I. J.: Geological and petrological conditions of the Szanda - Bercel area
40 I. J. CSALOGOVITS mm, the ratio of maximum and minimum grain diameter is 1.3. The crystals of the matrix represent the third generation of the plagioclases. These have the form of slats (ratio of maximum-minimum diameter is 5.7) and are free from inclusions. Metavulcanitic decomposition (montmorillonitization) is powerful here. Coloured components occur in the matrix only decomposed, chloritized augite grains and small serpentine scraps are indicative of olivine. Occasional felsitization appears in the fresh parts of the glass between the slats of the matrix. The „base andésite" of the SW side of Péterhegy is of similar type. The porphyria bytownites are resorbed, some of them are very rich in augite and olivine inclusions, and are of a crushed structure. There are no mechanical changes in the matrix Fig. 5.: Cross-section through the hydrothermal formations of Mt. Bercel Legends: 1. Andésite. 2. Andésite decomposed hydrothermally. 3. Highly decomposed andésite. 4. Montmorillonite. 5. Mixture of the decomposed andésite rubbles and montmorillonite-calcite. 6. Mouldering calcite. 7. Wax-opal in the environment of plagioclases of crushed structure: crushing took place before cooling and this necessarily indicates and intratelluric origin of part of the porphyries. The rocks of the Bábakő section (SW) of the large quarry of Péterhegy are similar to the former. A difference appears in the size of the inclusions which measure as much as 0.4 mm here (augite) and make up 3—4% of the components. The rock at exploring level II of Péterhegy (quarry, N side of Péterhegy) is also bytownite-phenoandesite in a hydrothermally decomposed condition. Decomposition is indicated by the montmorillonitization of the plagioclases and slight limonitization. b) Bytownite- andésite (Délkút dike) The rock of the Délkút dike which forms the bottom of the Szanda slip volcano is chemically similar to that of Szanda. Because of speedier cooling resulting from its smaller mass (the dike is 8—12 m thick), the matrix between the 2.5 mm bytownite porphyries of intratelluric origin shows no intersertal texture, unlike the rocks of Szanda; the glass content is higher and the texture is pilotaxitic. In the glass between the fluxion-structure plagioclases (0.12—0.04 mm) of the matrix there occur small augite microlites and magnetite grains. The ratio of maximum and minimum diameters of the porphyric plagioclases is 2.2: in case of smaller porphyries it is 1.25, while it varies from 3 to 6.5 in the crystals of the matrix. Only magnetite inclusions occur in the porphyries here. With the opaque grains of the glass, 3—4% of the components are magnetite. Isometric basaltic augite of 50—80 p. magnitude occurs sporadically.
