| Summary: | Fluid and solid inclusions in magmatic garnet from Permian pegmatites of the Koralpe Mountains were investigated. On the basis of MnO/(MnO + FeO) ratios, different degrees of melt fractionation during garnet growth were linked with fluid inclusion densities and chemistries. It is shown that garnet indicating low-melt fractionation trends contained primary CO<sub>2</sub> ± N<sub>2</sub>-rich fluid inclusions of the highest densities, up to 1.15 g/cm<sup>3</sup>, compared to garnet samples of increased fractionation trends comprising CO<sub>2</sub>-N<sub>2</sub>-rich fluid inclusions with lower densities up to 0.85 g/cm<sup>3</sup>. This fluid composition is interpreted as a part of an unmixed CO<sub>2</sub> ± N<sub>2</sub>-H<sub>2</sub>O-rich fluid that was present during garnet crystallization. Variabilities in the nitrogen composition up to 40.83 mol% resulted from different degrees of partial melting of mica and plagioclase from the metapelitic host rock. Densities, fluid chemistries, and mineral chemical data enabled a continuous upward trend for garnet crystallization during anatexis from lower (ca. 25 km) up to middle crustal levels (12–15 km). Resulting amphibolite/granulite facies conditions of 7.6 kbar/700 °C for garnet crystallization in spodumene-free pegmatites were significantly higher than previously suggested for pegmatite formation in the Koralpe Mountains.
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