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

Table 4 (continued) Szt-1033 Szt-1034 Szt1069 cpx* cpx cpx ol* ol cpx* cpx Pg ol* ol cpx* cpx Pg SiO, 52.67 48.32 51.12 40.26 40.72 53.02 52.44 58.64 40.56 40.31 51.83 49.27 50.71 TiO. 0.20 0.68 0.52 0.00 0.00 0.18 0.64 0.15 0.02 0.02 0.61 1.49 0.15 AhO. 2.82 8.57 5.74 0.01 0.03 2.85 3.76 25.58 0.03 0.05 6.18 8.67 31.07 CrO. 0.43 3.05 1.15 0.04 0.07 1.00 1.17 nd 0.03 0.02 1.21 0.42 nd FeO 2.74 2.96 3.08 9.02 9.28 3.02 3.42 0.44 10.07 11.31 3.65 4.00 0.50 MnO 0.07 0.05 0.06 0.14 0.14 0.05 0.10 nd 0.14 0.18 0.11 0.09 nd NiO nd nd nd 0.40 0.41 nd nd nd 0.37 0.31 nd nd nd MgO 17.02 15.21 16.16 49.55 49.40 17.95 17.90 0.14 48.52 47.64 15.90 14.84 0.17 CaO 23.81 20.68 21.72 0.08 0.16 20.66 19.72 8.09 0.10 0.23 18.79 20.27 14.31 NibO 0.18 0.53 0.41 nd nd 0.76 0.83 6.15 nd nd 1.37 1.09 3.10 K,0 0.00 0.00 0.00 nd nd 0.00 0.00 0.65 nd nd 0.00 0.01 0.30 Total 99.94 100.05 99.96 99.48 100.2 99.49 99.98 99.84 99.83 100.1 99.65 100.14 100.31 mg 91.71 90.15 90.34 90.73 90.46 91.37 90.32 89.60 88.20 88.59 86.86 ol - olivine, Cpx = clinopyroxene, Pg = plagioclase, * = Primary phase in the lherzolites, its occurrence is scarce and it is certainly absent in all but one samples we investigated. Secondly, the potash content of the amphiboles is small, in some instances quite insignificant, so the involvement of amphibole does not seem to account for the elevated potassium contents found in the glasses. Though there is compelling microscopic evidence for the role of breakdown of amphibole in the genesis of glass in the xenolith Szt1106, the chemistry of this glass does not show any distinctive features compared with the other examples. In fact the chemical compositions and CIPW norms of pargasitic amphiboles are very different from those of the glasses. Therefore we can conclude that the formation of glass must have involved the melting of additional phases as well as materials introduced by metasomatic agents. In more general terms, our experience supports the view that the involvement of amphibole and/or mica in the partial melting cannot be safely demonstrated by chemical means because of the large variations of Ca/Na/K that exist for glasses reportedly derived from amphibole or mica (FREY &