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
1974), Canary Isles (FORBES & STARMER 1974). However, glasses from Mongolian peridotites are distinct by having considerably higher ratios of Na/K (striped area in Fig. 9). Synthetic partial melts (MYSEN and BOETTCHER 1975; KUSHIRO 1971 ) have much lower contents of potash than do natural glasses. Their composition is close to that of a 3:1 mixture of diopside/spinel , minerals that melts first in a peridotite assemblage (Fig. 9 ) Glass compositions in the lower crustal granulite xenolith (Bo-3007) are significantly different from those of mantle peridotites (Fig. 9) being extremely low in potash and enriched in Ca. They are also considerably more enriched in AI, Fe and Mg but lower in Si and Na relative to glasses in peridotites (Table 1.). Their norm is dominated by anorthite and hypersthene, the amount of normative corundum is also significant (Table 3). CHEMISTRY OF PHASES IN THE FINE-GRAINED GLASS-BEARING ZONES Secondary phases in fine-grained glass-bearing zones and blebs show differences in their chemistry compared to their respective primary phases in the Ca Fig. 9. Glass compositions (Ca-Na-K) from mantle xenoliths of WPB (open squares) and Bo-3007 granulite xenolith (diamonds). Circles represent synthetic partial melts of spinel peridotites produced at highly differing conditions of P, X(H20), X(C02) (MYSEN & BOETTCHER 1975; KUSHIRO 1971). The star represents the composition of a 3:1 mixture of diopside/spinel. Encircled area: compositional field of natural glasses from mantle-derived xenoliths from world-wide localities (Olmani, Tanzania: JONES etal. 1983; Hoggar, Algeria: GIROD etal. 1981 ; Victoria, Australia: FREY & GREEN 1974, IRVING 1974; Alaska: FRANCIS 1976; Canary Isles: FORBES & STARMER 1974). Striped area: composition of glasses in melt pockets from Mongolian spinel peridotite xenoliths (IONOV <?/«/. 1994).
