Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 76. (Budapest 1984)

Embey-Isztin, A.: Texture types and their relative frequencies in ultramafic and mafic xenoliths from Hungarian alkali basaltic rocks

bole grains (Fig. 4). It is surprising that the lherzolite fragments have very different textures (e. g coarse with euhedral spinel inclusions, equigranular tabular, and medium-grained types). Inclusion Szt-2001 is composed of black pyroxenite (Al-augite) and dunite (Fig. 4). Since the fayalite content of the olivine is rather high (100 Mg/Mg +SFe = 86.4; unpublished analysis) which is a usual feature in the black pyroxene rich suite xenoliths, we cannot be sure of the composite nature of this xenolith. DISCUSSION The alkali basaltic volcanic province of Transdanubia was chiefly formed 5 to 2.5 m. y. ago (BALOGH et al. 1982). This relatively short time interval enables us to consider the textural properties of the mantle derived peridotite xenoliths as important indicators of a quasi contemporaneous tectonic state of the upper mantle beneath this region. Furthermore, Fig. 4. Sketches of composite xenoliths. For explanations see the text