Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 12. 1985. (Budapest, 1985)

Basalts of the Tátika group The basalt of Kovâcsihegy (2.90± 0.24 m.y., BALOGH 1984) shows a remarkable chemical and mineralogical homogenity (EMBEY-ISZTIN & SCHARBERT 1981). The rock is an olivine basanite with low normative nepheline and S.I. and high D.I. values (28.1 and 46.4, respectively).The mgvalue is also low (55.1), the normative olivine is 11.9 %. These figures clearly indicate that the olivine basanite of Kovácsihegy is a strongly differentiated rock. Fig. 4 KO- SIO diagram for basalts and basaltic andésites of Transylvania and Bánát. Symbols same as 22 in Fig. 2 Unlike Kovácsihegy, the basalts of Lázhegy (

Uzsabánya) (3.41Í 0.84 m.y., BALOGH 1984) are mlneralogically and chemically heterogenous (EMBEY-ISZTIN & SCHARBERT 1981). The compositional spectrum comprises olivine tholeiites (normative hyperstene 5.86 %) at one end, as well as olivine basanites (normative nepheline and olivine 6.15 and 13.62 % respectively) at the other end. The mg-value falls from 63.5 to 57.0, that of the S.I. from 38.01 to 30.38 with increasing rate of undersaturation. Analyses collected by JUGOVTCS (1976) show that the rock of Szebike may be an olivine basanite medium-rich in nepheline (mg-value 60-63). The Sarvalyhegy basalt samples originate from the quarry of Sümegprága (2.79±0.29 m.y. BALOGH 1984). A high number of high-quality analyses have recently been carried out on this rock (EMBEY-ISZTIN & SCHARBERT, unpublished). According to the results of the analyses the basalts of Sümegprága are olivine basanites medium-rich in nepheline and olivine (11.15-16.68 % normative). The mg-value varies between 57.9-63.17. Considering these values as well as the position of the Sümegprága rock in the D.I.-S.I. diagram (Fig. 6), it seems likely that they were originated by a medium-rate of partial fusion followed by a subsequent fractionation. The chemistry of the Tátika basalt is known from the work of M AURITZ (1948). It seems from his data that the Tátika olivine basanite is less differentiated than the basalt of Sümegprága normative olivine up to 16 %, S.I.: 34.2-35.9, D.I.: 35.0-37.2). Basalts of the Balaton Highland (Balatonfelvidék) An important number of small basalt volcanoes is known in this region. They are built up of basaltic lava flows and/or basaltic tuffs. The petrochemistry of the basalt of Badacsony (3.45± 0.23 m.y., BALOGH 1984) has recently been studied (EMBEY-ISZTIN & SCHARBERT, unpublished) but a number of Important old analyses