Abstract. Experimental phase equilibria have been investigated on three medium-K silicic andesite (60-61 wt % SiO2) samples from Mount Pelhe at 2-4 kbar, 850-1040øC, under both vapor-saturated CO2-free and vapor-saturated CO2-bearing conditions. Most experiments were crystallization experiments using dry glasses prepared from the natural rocks. Both normal-and rapid quench experiments were performed. Two ranges of oxygen fugacity (fo2) were investigated: NNO (Ni-NiO buffer) to NNO + 1 and NNO + 2 to NNO + 3. At 2 kbar for moderately oxidizing conditions, plagioclase (pl) and magnetite (mt) are the liquidus phases, followed by low-Ca pyroxene (opx); these three phases coexist over a large temperature (

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