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

be younger (2.29 m. y.). In spite of the varying lava compositions of the different volcanoes (Table 1, analyses 81-218), these rocks form a more or less coherent group, with the exception of Bondoró-hegy. While, the Balaton Region lavas tend to show a stronger lithospheric signature (higher K/Nb, Rb/Nb and lower Ce/Pb, as well as higher ^Pb/^Pb and ^Sr/^Sr the inverse is true for the Bondoró-hegy basalt, that is the only known example of an astenosphere dominated liquid in the central part of the Pannonian Basin. LREE and highly incompatible element enrichment are very similar in different lavas, however, the degree of enrichment is positively correlated with the degree of undersaturation of the lavas. Badacsony lava is a fairly undersaturated basanite (mg 64.3-64.5, ne 12.114.6%, S.I. -20). Halom-hegy mg 66.7, ne 12.8-12.9%), Hegyestű (mg 64.9, ne 13.4%) and Sarvaly (Sümegprága) (mg 64.8-65.6, ne 8.1-12%) show similar degrees of undersaturation. Gulács (mg 64.3-64.7, ne 6.9-7.84%), Hegyesd (mg 63.463.6, ne 4.67-5.87%, S.I. -5.8) are less undersaturated basanites. The lava of Halyagos at Diszel is inhomogeneous (mg 65.2-67.0, ne 3.37-10.2%) (alkali olivine basalt and basanite). Kovácsi-hegy basalt has a composition of mg 58.3-62.4, ne 3.30-8.50%) and the Szigliget lava is mg 65.7-65.9, ne 4.53-5.34%. Less undersaturated are the lavas of Láz-hegy at Uzsa (mg 65.7-68.4 ne 0.20-6.4%), Szentgyörgyhegy (mg 64.0-65.0, ne 0-3.15%, hy 0-3.87%), Agár-tető (mg 59.2-65.3, ne 00.64%, hy 0-1.23%), Haláp (mg 60.4-65.7, ne 0-3.35%, hy 0-1.35%) and especially the Kab-hegy (Tormarét) which is the less undersaturated rock in the Pannonian Basin volcanic province being a typical olivine tholeiite (mg 61.3-63.5, hy 1.3810.2%). The S.I. can be as high as +3 to +5. The exceptionally high mg-number of the Bondoró-hegy basanite (76.2-76.3, ne 11.1-12.4%) is the result of the fact that this is the only rock that lacks olivine phenocrysts, but contains abundant debris and xenocrysts originating from mantle peridotites. Nógrád and adjacent regions The Nógrád region is situated at the northern border zone of the Pannonian Basin, close to the mountain chains of the Carpathian arc. Alkali basalt volcanoes are younger here than in the Balaton region (Medves Plateau 2.76 m.y., Magasmart 0.53 m.y.). The basalts of Banská Stiavnica (Selmecbánya) and Kysihibel are, however, old (6.8-7.7 m.y.). The Medves plateau is the largest basalt flow in Nógrád, with two major quarries (Magyarbánya and Eresztvény). Somoskő, Szilváskő, Kis-Salgó, PécskŐ and others are smaller volcanoes. Nógrád lavas are fairly evolved undersaturated basaltic liquids (Table 1, analyses 219-239). As Graz Basin basalts, and unlike Balaton region lavas, they show a strong asthenospheric signature. Sr isotope ratio is relatively low, Nd isotope ratio as well as Ce/Pb is higher. Pb isotope ratios plot near to the NHRL of HART. The lavas of the Medves Plateau have a slightly varying composition: Magyarbánya MED (mg 61.1-61.3, ne 16.8-19.3%, S.I. -23) and Eresztvény ERES (mg 61.2-62.1, ne 11.8-14.6%). Somoskő (SKO) is even more evolved with mg 56.3, ne 15.4%. The young basalt of Brehy = (Magasmart) is also an undersaturated, but primitive basanite (ne 15.1%, mg 68.2). The old basalt lava of Banská Stiavnica has a normative ne-content of 11.4% (mg 65.7). Dobra Niva = (Dobornya) and Kysihibel basalts are much less undersaturated (ne 2.4%, mg 60.5 and ne 0.8%, mg 56.8 respectively).