Reduced carbonic fluids in mafic granulite xenoliths from the Bakony-Balaton Highland Volcanic Field, W-Hungary

A unique CO2-CO-C fluid system-which has not been described from the lower crust so far-occurs in inclusions of the rock-forming minerals, mainly in plagioclase and clinopyroxene. A primary and two secondary fluid inclusion (FI) generations were identified on the basis of textural analyses and distribution of homogenization temperatures. Primary FIs are connected to the formation of garnet granulite. The older secondary generation was trapped after the main temperature increase and some pressure decrease during crustal thinning. The younger secondary generation trapped within the depth limits of the present lower crust at pressures between 0.6-0.7 GPa. The overall composition of the fluid system has not changed during crustal thinning. The calculated oxygen fugacity values are slightly above and under QFM (between 10-8.5 and 10-10.1 at 1200 °C).