Glassy orthopyroxene granodiorite-tonalite (named
pincinite after type locality) was described from basaltic lapilli tuffs of the Pliocene maar near Pinciná village in the Slovakian part of the Pannonian Basin. Two pincinite types exhibit a qualitatively similar mineral composition (quartz, An
20–55 plagioclase, intergranular silicic glass with orthopyroxene and ilmenite, ±K-feldspar), but strongly different redox potential and formation
PT conditions. Peraluminous pincinite is reduced (6–7% of total iron as Fe
3+ in corundum-normative intergranular dacitic glass) and contains ilmenite with 8–10 mol% Fe
2O
3 and orthopyroxene dominated by ferrosilite. High-density (up to 0.85 g/cm
3) primary CO
2 inclusions with minor H
2, CH
4, H
2S, CO and N
2 (<2 mol% total) are present in Qtz and Plg. Equilibrium
PT conditions inferred from the intergranular Opx–Ilm–Glass assemblage and fluid density correspond to 1,170±50°C, 5.6±0.4 kbar, respectively. Metaluminous pincinite is more oxidised (25–27% of total iron as Fe
3+ in diopside-normative intergranular glass of rhyolite–trachyte–dacite composition) and contains Fe
2O
3-rich ilmenite (17–29 mol%) associated with enstatite. Fluid inclusions are composed of CO
2–H
2O mixtures with up to 38 mol% H
2O. Raman spectroscopy revealed H
2S along with dominant CO
2 in the carbonic phase. Equilibrium
PT parameters for the intergranular Opx–Ilm–Glass assemblage correspond to 740±15°C, 2.8±0.1 kbar, respectively. Reducing gas species (<2 mol% total) in the CO
2-inclusions of the peraluminous pincinite resulted from hydrogen diffusion due to
fH
2 gradient imposed during decrease of redox potential from the log
fO
2 values near QFM during Qtz + Plg growth, to QFM-2 incidental to the superimposed Opx + Ilm assemblage in the intergranular melt. The decrease in oxygen fugacity was recorded also in the metaluminous pincinite, where log
fO
2 values changed from ~QFM + 2.6 to QFM + 0.4, but hydrogen diffusion did not occur. Absence of OH-bearing minerals, major and trace element abundances (e.g. REE 300–320, Nb 55–57, Th 4–31, Zr 240–300 ppm, FeO
tot/MgO up to 11), and Sr–O isotope ratios in the pincinites are diagnostic of high-temperature anorogenic magmas originated by dehydration melting of biotite in quartz-feldspathoid crust (
87Sr/
86Sr>0.705–0.706,
18O>9 V-SMOW) around alkali basalt reservoir in depths between 17 and 20 km, and around late stage derivatives of the basalt fractionation, intruding the crust up to depths of 10–11 km. Low water activity in the pincinite parental melt was caused by CO
2-flux from the Tertiary basaltic reservoirs and intrusions. The anatexis leads to generation of a melt-depleted granulitic crust beneath the Pannonian Basin, and the pincinites are interpreted as equivalents of igneous charnockites and enderbites quenched at temperatures above solidus and unaffected by sub-solidus re-equilibration and metamorphic overprint.
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