Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 72. (Budapest 1980)
Örkényi-Bondor, L.: Andesite agglomerate from Zebegény village, Börzsöny Mountains (Hungary)
42 L. ÖRKÉNYT-BONDOR site a considerable amount of tridimite and cristobalite also developed. Beside the sequence known from the literature (hornblende -* clinopyroxene -*• orthopyroxene) another also could be established : hornblende orthopyroxene clinopyroxene. The silica contents are nearer to those of the island arc andésites. As for the FeO f Fe 2 0 3 / MgO values, they correspond in 13 specimens with those of the continental andésites; 4 values coincide with those of the island arc andésites. Of the K 2 0/N 2 0 data 2 coincide with the data of the island arc andésites; the others are in the common interval of both kinds of andésite rocks. Consequently, the chemism of the investigated rocks does not display the typical features of the continental andésites. Farther-reaching conclusions would be beyond the scope of the present paper. Acknowledgements — Thanks are due to Prof. J. Kiss for the photomicrographs and for his active interest in this work. L. BOGNÁR contributed with X-ray investigations, GY. PITTER with chemical analyses, and P. ZENTAI with minor and trace element determinations. Their precious contributions are heartily acknowledged. References BÖCKH, H. (1899-1902): Nagymaros környékének földtani viszonyai. — Földt. Int. Évk., 13: 1-57. BURRI, C. (1963): Bemerkungen zur sog. „Banater Verwachsung" der Plagioklase. — Schweiz. Min. Petr. Mitt., 43: 71-80. BURRI, C. (1972): Zur Definition und Berechnung der optischen Orientierung von Plagioklasen. — Schweiz. Min. Petr. Mitt., 52: 497-514. BURRI, C. (1974b): Vereinfachte Berechnung der Euler-Winkel zur Charakterisierung der Plagioklasoptik. — Schweiz. Min. Petr. Mitt , 54: 33-38. BURRI, C, ÖRKÉNYI, B. L. & VINCZE, SZ. H. (1976): Rechnerische Auswertung von U-Tischoperationen durch elementare Vektormethoden. — Schweiz. Min. Petr. Mitt., 56: 1-38. BURRI, C, PARKER, R. L. & WENK, E. (1967): Die optische Orientierung der Plagioklase. — BaselStuttgart, p. 1-334. DEER, W. A., HOWIE, R. A. & ZUSSMAN, J. (1963): Rock Forming Minerals., 2. Chain Silicates. — London, p. 1-379. ISSHIKI, N. (1963): Petrology of Hachijo-Jima Volcano Group, Seven Izu Islands, Japan. — /. Fac Sc. Univ. Tokyo, 15: 91-134. JAKES, P. & WHITE, A. J. R. (1972): Hornblendes from calc-alkaline volcanic rocks of islands arcs and continental margins. — Aer. Min., 57: 887-902. KUBOVICS, I. & PANTÓ GY. (1970): Vulkanológiai vizsgálatok a Mátrában és a Börzsönyben. — Budapest, p. 1-302. NIKITIN, W. W. (1936): Die Fedorow-Methode. — Berlin, p. 1-527. ÖRKÉNYI, B. L. (1976): Eulerian angles and the pseudosymmetry of the plagioclase. — Ann. Univ. Budapest., 52: 41-54. ÖRKÉNYI, B. L. & VINCZE, SZ. H. (1974): (110)(1I0) (130) (130) plagioclase twinning in andésite from Hungary. — Acta Geol. Hung., 18: 99-135. PANTÓ, GY. (1969): Textural, mineralogical and alteration characteristics of the Börzsöny Mountains volcanic rocks. — Acta Geol. Hung., 13: 277-302. STÄCHE, G. (1866): Die geologische Verhältnisse der Umgebungen von Waitzen in Ungarn. —• Jahrb. k. k. Geol. Reichsanst., 16: 277-328. SZABÓ, J. (1894): Típuskeveredések a dunai trachitcsoportban. — Földt. Közl, 24: 169-177. Author's address: DR. LÍVIA ÖRKÉNYI-BONDOR Mineralogical and Petrographical Department Hungarian Natural History Museum H- Budapest, pf. 330 Hungary
