Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 92. (Budapest 2000)

Embey-Isztin, A. ; Scharbert, H. G.: Glasses in peridotite xenoliths from the western Pannonian Basin

GLASS COMPOSITIONS Glass compositions from peridotites vary widely (Table 1). Though we did not analyse P2O5, it is likely that this oxide is also present since JONES etal. (1983) found that all glasses in their xenoliths originating from Olmani basalts (Tanzania) carried about 1% P2O5. Glasses from Mongolian peridotite xenoliths also contain varying amounts of P2O5 (average abundances between 0.11 and 1.86%; IONOV et ai 1994). Glasses in lherzolite xenoliths from Yemen contain P2O5 in concentrations up to 1% (BRUNET&CHAZOT 1999). Glasses are more aluminous and siliceous, less magnesian and iron-rich and generally richer in alkalis, especially in potash than typical lavas of the volcanic region (cf. EMBEY-ISZTIN et al. 1 993Í7, b). Compared to glass compositions of Olmani peridotites (Tanzania), WPB glasses are more siliceous and aluminous, Figs 5-8. 5: Narrow vein around a primary orthopyroxene with primary inclusion-spineis (poikilitic texture, Szt1034). The vein is composed of fragments of primary orthopyroxene, secondary clinopyroxene, glass and vugs. II N, M=20x. 6: Texturally equilibrated amphibole grain in Szt-1

106 showing signs of decomposition involving the formation of secondary clinopyroxene and glass. II N, M=40x. 7: Dark glass with abundant elongated quench plagioclase needles and vugs with a spherical structure in the composite xenolith Szg-3007. The glassy area developed between Type II pyroxenite (lower left grey area) and Type I peridotite (upper right white area). II N, M=20x. 8: Widely developed glassy area containing tiny needles of quench plagioclase in the granulite xenolith, Bo-3007. +N, M=100x.