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

Tabic 2. The range of major element compositions in glasses from WPB, Olmani, Mongolia and Tahaa WPB hOlmani #Mongolia ! Tahaa Si0

2 47.82-59.12 42.7-50.90 51.83-64.99 62.23-65.06 TiO, 0.82-2.99 0.60-3.72 0.02-0.74 0.60-0.99 A1A 18.43-22.65 12.40-21.10 15.5-23.39 16.12-18.48 FeOtot 2.20-6.87 0.70-10.90 1.66-4.49 0.90-4.25 MgO 2.22-4.44 0.71-12.30 0.48-4.25 1.15-3.23 CaO 3.71-10.31 2.30-12.80 0.21-8.05 0.81-1.65 Na,0 2.92-5.84 0.40-7.30 6.80-10.55 3.82-6.10 K

;

0 0.13-4.08 3.30-3.80 0.54-4.74 6.22-10.43 +JONES etal. ( 1983); #[ONOV etal. (1994); ! SCHIANO et al. (1992) however less silica-rich than glasses from Mongolian and Tahaa Island (Society archipelago) xenoliths (Table 2). This is compensated by smaller quantities of Fe, Mg and Ca both in WPB and Mongolian glasses relative to the Olmani ones. Alkali content is high and variable, however the abundance of potash is considerably greater in glasses from Tahaa xenoliths than in WPB and other continental peridotite inclusions. In our glasses a positive correlation exists between Mg and Ca and a negative one between Fe and Si. In contrast, JONES et al. ( 1983) observed a positive correlation among P, Si, Ti and Na in the glasses of Olmani xenoliths. However, in WPB glasses if anything, there is a weak negative correlation between Si and Ti and no correlation between Na and Si. Na and Ti show a very weak positive correlation. One part of the peridotite xenoliths contain glasses with quartz-normative compositions (Szt-1033, Szt1034, Szt-1

106, Szt-1

116, G-1055), Because of the high alumina contents, some of theses glasses are corundum-normative (Table 3). In contrast, glasses in the other part of the xenoliths are nepheline-normative. The abundance of normative nepheline is particularly high in the glass composition of sample Szt1069, owing to the low Si and high alkali content. In the Ca-Na-K diagram (Fig. 9) glasses from WPB peridotites plot inside the area (encircled field) defined by compositional variability of similar glasses in Olmani, Tanzania (JONES et al. 1983), Nunivak Island, Alaska (FRANCIS 1976), Algeria (GIROD et al. 1981), Victoria, Australia (FREY & GREEN 1974, IRVING