Volatile emission during the eruption of Baitoushan Volcano (China/North Korea) ca. 969 AD

The 969 +/- 20 AD Plinian eruption of Baitoushan Volcano (China/North Korea ) produced a total tephra volume of 96 +/- 19 km(3) [magma volume (DRE): 24 +/- 5 km(3)]. The main phase (ca. 95 vol.%) is represented by comenditic t ephra deposited dominantly as widespread fallout blankets and proximal igni mbrites. The eruption column is estimated to have reached ca. 25 km and thu s entered the stratosphere. A late phase (5 vol.%) is represented by trachy te emplaced chiefly as moderately welded ignimbrites. The comendites contai n similar to 3, and the trachytes 10-20 vol.% phenocrysts, mainly anorthocl ase, hedenbergite, and fayalite. Primary glassy melt inclusions with no sig ns of leakage were found only in phenocrysts in the comenditic tephra, wher eas those in phenocrysts in the trachytes are devitrified. The comendite ma gma is interpreted to have been generated by fractional crystallization fro m a trachyte magma represented by melt inclusions in the phenocrysts in the comendite tephra. The mass of volatiles emitted to the atmosphere during t he eruption was estimated using the petrologic method. The average H2O conc entration of the comenditic matrix glass is 1.5 wt.% (probably largely seco ndary) and of the corresponding melt inclusions similar to 5.2 wt.%. Melt i nclusions in feldspar and quartz present the highest halogen concentrations with a calculated average for chlorine of 4762 ppm and for fluorine of 429 4 ppm. The comenditic matrix glasses are represented by a fluorine-rich (39 92 ppm F) and fluorine-poor group (2431 ppm F), averaging 3853 ppm for chlo rine. Only 20% of all sulfur analyses of the comenditic matrix glasses and melt inclusions are above the detection limit of greater than or equal to 2 50 ppm S. The difference between pre- and post-eruptive concentration of H2 O is at least 3.7 +/- 0.6 wt.% H2O taking into consideration re-hydration o f the matrix glass and possible leakage of melt inclusions. The difference between pre- and post-eruptive concentrations of the halogens amounts to 90 9 +/- 90 ppm Cl, and 1863 +/- 280 ppm and 302 +/- 40 ppm F. The difference for 8 was estimated based on the average of the maximum 8 concentrations in the melt inclusions (455 ppm S) and the detection limit, resulting in 205 +/- 40 ppm S. The calculated mass of volatiles injected into the atmosphere , based on the erupted magma volume and volatile data, is 1796 +/- 453 mega tons for H2O, 45 +/- 10 megatons for chlorine, 42 +/- 11 megatons for fluor ine, and 2 +/- 0.6 megatons for sulfur. The 969 +/- 20 AD eruption of Baito ushan Volcano, one of the largest eruptions of the past 2000 years, is thou ght to have had a substantial but possibly short-lived effect on climate.