MAFIC AND SALIC IGNEOUS XENOLITHS IN LATE TERTIARY ALKALINE BASALTS -FLUID INCLUSION AND MINERALOGICAL EVIDENCE FOR A DEEP-CRUSTAL MAGMATIC RESERVOIR IN THE WESTERN CARPATHIANS

Explosive Late Tertiary alkaline basalts have ejected pyroxenite, homb lendite, anorthoclasite and quartz-bearing tonalite-trondhjemite xenol iths in the northern margin of the Pannonian Basin. One tonalite sampl e contains primary CO2-H2O inclusions with up to 20 vol. % of aqueous phase. Remaining tonalites, anorthoclasites and mafic rocks trapped CO 2 inclusions without detectable water. Except for homblendites, the CO 2 inclusions coexist with silicate melts. Additional, not yet detected volatiles are responsible for depression of the CO2 final melting tem perature, which clustered mostly around -58 degrees C in all rock-type s. Maximum densities of the CO2 inclusions tend to decrease from pyrox enites (0.92 g/cm(3)), through anorthoclasites (0.89 g/cm(3)), to tona lites (0.85 g/cm(3)) and homblendites (0.75-0.87 g/cm(3)), thus reflec ting decreasing depth of formation. Equilibration PT conditions for cl inopyroxenes ranged between 1220 degrees C at 10 kbar and 1068 degrees C at 4.3 kbar, with the 50 % of estimates projecting between 6.5-7.5 kbar. Postcumulus homblende, coexisting with An(53-64) plagioclase, cr ystallized at 928-1074 degrees C. Most of the PT data for pyroxenites indicate depths between 23-26 km, close to recent Moho discontinuity ( 27-29 km), while those for tonalites and homblendites reflect their mi ddle crustal emplacement (15-20 km). Cumulate textures, varying modal composition and essentially CO2-dominated primary inclusions suggest f ormation of the xenoliths by fractional crystallization in a large res ervoir of mantle-derived basaltic magmas. The cumulate origin of tonal ites and anorthoclasites is corroborated by nearly identical whole-roc k REE distribution, showing pronounced positive Eu anomaly and enrichm ent in LREE. Contrasting calc-alkaline and alkaline affinities of clin opyroxenes and hornblendes in selected mafic xenoliths might result fr om heterogeneity of the parental basaltic magma generated either in me tasomatised lithospheric mantle or in upwelled asthenosphere.