Abstract Magma mixing is a widespread magmagenic process. However, its significance in the formation of ultrapotassic magmas has been largely overlooked so far as they are commonly thought to originate directly from mantle and ascend rapidly through crust. The Hezhong lavas Western Yunnan (SW China) (basaltic) trachy-andesitic composition. These rocks display porphyritic textures with olivine, ...

Measurements of CO2 fluxes from open-vent volcanos are rare, yet may offer special capabilities for monitoring volcanos and forecasting activity. The measured fluxes of CO2 and SO2 from Mount St. Helens decreased from July through November 1980, but the record includes variations of CO2/SO2 in the emitted gas and episodes of greatly increased fluxes of CO2. We propose that the CO2 flux variatio...