Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 16. 1993. (Budapest, 1993)

Graz Basin is a marginal basin at the westernmost edge of the Pannonian area, close to the Eastern Alps (Fig. 1). Lavas in this region are by far the most undersaturated basalts in the whole Pannonian area (Table 1, analyses 48-65). Three volcanoes are known to have produced lava rocks (Stradner Kogel, Steinberg and Klöch). In addition, tuff volcanoes are also present e.g. Kapfenstein, famous for its nodules of peridotites. Graz Basin lava flows seem to be very young (Steinberg 2.20, Klöch 2.28 m. y. Balogh, personal communication). Stradner Kogel Analyses (48-56) in Table 1 show that the Stradner Kogel lava has the highest alkali and lowest silica content in the whole volcanic province. Consequently, this is an extremely undersaturated rock with normative ne exceeding 30%, lc about 13%, and larnite (Ca-orthosilicate) around 6% (nefelinite). The saturation index (S.I.), (Fitton et al. 1991) can be as low as -50 to -55. Their low mg-values (100xMg/Mg+Fe

2

+

) (56.4-56.6) attest to a relatively highly evolved character. The enrichment of incompatible elements including LREE is also the most pronounced among the Pannonian Basin basalts (Tables 2 and 3). On the contrary, compatible elements such as Ni and Cr are low. The ratio of K/Nb and Rb/Nb is low, however, Ce/Pb is among the highest in the whole volcanic province. The lava rock is characterised by a low Sr and a high Nd isotope ratio (Table 4). Pb isotope ratios fall on or near to the NHRL defined by Hart (1984). The O isotope ratio is low and typical of mantle derived magmas. Steinberg and Klöch Steinberg (ST) and Klöch (K) lavas (Table 1, analyses 57-65) are the second most undersaturated basalts of the Pannonian Basin. Normative ne varies between 14-23% in rocks of both localities. Klöch basalts are, however quite primitive with higher mg-values (65.6-67.2) and somewhat higher Ni and Cr concentrations. Steinberg lavas (mg 54.0-63.5) are differentiated. Compared to Klöch, incompatible elements, such as LREE, are slightly more enriched in Steinberg lavas. Burgenland Basalt volcanoes of Burgenland are situated also in the western part of the Pannonian Basin, close to the Vienna Basin. Two individual volcanoes produced lava flows (Pauliberg = Pálhegy [P] and Oberpullendorf = Felsőpulya [OP]). Basaltic tuff is also known e.g. Tobaj. The lavas are sensibly less undersaturated than in the Graz Basin, especially in the case of Oberpullendorf (Table 1, analyses 147). Oberpullendorf This rock is one of the rare cases in the Pannonian Basin, containing normative hy (up to 5.4%) (olivine basalt - olivine tholeiite). The mg-value is between 63.2 - 65.9, however, the abundances of Ni and Cr are greater than in most other lavas of the whole volcanic province. An outstanding feature of all Burgenland ba-