Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 16. 1993. (Budapest, 1993)
salts is their low abundance of Al as compared to other alkali basalt lavas in the Pannonian Basin and basalts of world-wide localities. The enrichment of highly incompatible elements is one of the lowest in the volcanic province. The Sr isotope ratio is relatively high and that of the Nd is low. The Pb isotope ratios plot near to the NHRL line of HART. According to the measurements of K. BALOGH, Burgenland basalts show the oldest K/Ar age in the whole volcanic~"province (Oberpullendorf 11.1, Pauliberg 11.5 m. y.). Pauliberg Chemically, this lava flow is quite inhomogeneous. The normative ne-content varies widely (4.7-13.0%) corresponding to alkali basalts and basanites. This rock is highly peculiar with its very low content of alumina. In addition, while the highly incompatible elements are only moderately enriched, the less incompatible elements (Ce, Nd, Pb, Nb, Zr and Ti) show an uncommonly strong enrichment. Highly evolved rocks ("trachydolerite") are also known from Pauliberg (e.g. sample P414). Little Hungarian Plain These basalts occur in a region of a very important depression. There are individual lava flows (Somlyó SML, Ság-hegy SAG, Kis-Somlyó KSML, Herczeghegy (Sitke) SI, and tuff volcanoes, including a tuff ring between Gérce and Sitke. In many respects, Little Plain lavas (Table 1, analyses 66-80) are similar to the Balaton region basalts and differ from Burgenland and Graz Basin rocks. Their K/Ar age seems to vary considerably (Ság-hegy 6.27, Somlyó 2.98 m. y., Balogh 1984). Ság-hegy The basalt of Ság-hegy is quite primitive with a high mg-number (68.7-68.8). Ni and Cr abundances are not particularly high, however. This rock is only mildly undersaturated (ne 0.76-1.47%) (alkali olivine basalt). The enrichment of LIL elements is typical of alkali basalts and resembles Balaton region basalts. The ratio of Zr/Nb and Ce/Pb in the Ság-hegy and other Little Plain basalts is also similar to the Balaton region. Somlyó basalt (mg 60.9-64.6) has a varying composition (ne 0-3.46%, hy 04.71%) straddling the compositional fields of olivine tholeiite - olivine basalt and alkali olivine basalt. The lava of Kis-Somlyó (mg 65.3-65.4) is an alkali basalt (ne 1.98-2.45%). The rock of Sitke, Herczeg-hegy is a primitive basalt (mg 68.6) and shows an exceptionally high degree of undersaturation in this region (ne 13%) corresponding to a basanite. Balaton region The Balaton region volcanic field is situated in the Central Range, separating two depression areas (Fig. 1). This is the most important volcanic region as far as the number of volcanoes and the volume of lava and tuff production are concerned. The largest volcanoes (Kab-hegy and Agár-tető) also belong to this volcanic region. K/Ar ages mostly vary between 2.8 and 4.7 m. y., some eroded volcanoes such as Ragonya at Mencshely may be older (7.4 m.y.) and Bondoró-hegy seems to
