Volatile emission during the eruption of Baitoushan Volcano (China/North Korea) ca. 969 AD |
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| Authors: | Susanne Horn Hans-Ulrich Schmincke |
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| Institution: | (1) Abteilung Vulkanologie und Petrologie, Geomar Forschungszentrum, Wischhofstrasse 1–3, D-24148 Kiel, Germany e-mail: hschmincke@geomar.de, DE |
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| Abstract: | 3 magma volume (DRE): 24 ± 5 km3]. The main phase (ca. 95 vol.%) is represented by comenditic tephra deposited dominantly as widespread fallout blankets and
proximal ignimbrites. The eruption column is estimated to have reached ca. 25 km and thus entered the stratosphere. A late
phase (5 vol.%) is represented by trachyte emplaced chiefly as moderately welded ignimbrites. The comendites contain ∼ 3,
and the trachytes 10–20 vol.% phenocrysts, mainly anorthoclase, hedenbergite, and fayalite. Primary glassy melt inclusions
with no signs of leakage were found only in phenocrysts in the comenditic tephra, whereas those in phenocrysts in the trachytes
are devitrified. The comendite magma is interpreted to have been generated by fractional crystallization from a trachyte magma
represented by melt inclusions in the phenocrysts in the comendite tephra. The mass of volatiles emitted to the atmosphere
during the eruption was estimated using the petrologic method. The average H2O concentration of the comenditic matrix glass is 1.5 wt.% (probably largely secondary) and of the corresponding melt inclusions
∼ 5.2 wt.%. Melt inclusions in feldspar and quartz present the highest halogen concentrations with a calculated average for
chlorine of 4762 ppm and for fluorine of 4294 ppm. The comenditic matrix glasses are represented by a fluorine-rich (3992 ppm
F) and fluorine-poor group (2431 ppm F), averaging 3853 ppm for chlorine. Only 20% of all sulfur analyses of the comenditic
matrix glasses and melt inclusions are above the detection limit of ≥ 250 ppm S. The difference between pre- and post-eruptive
concentration of H2O is at least 3.7 ± 0.6 wt.% H2O taking into consideration re-hydration of the matrix glass and possible leakage of melt inclusions. The difference between
pre- and post-eruptive concentrations of the halogens amounts to 909 ± 90 ppm Cl, and 1863 ± 280 ppm and 302 ± 40 ppm F. The
difference for S was estimated based on the average of the maximum S 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 megatons for H2O, 45 ± 10 megatons for chlorine, 42 ± 11 megatons for fluorine, and 2 ± 0.6 megatons for sulfur. The 969 ± 20 AD eruption
of Baitoushan Volcano, one of the largest eruptions of the past 2000 years, is thought to have had a substantial but possibly
short-lived effect on climate.
Received: 25 July 1998 / Accepted: 8 September 1999 |
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| Keywords: | Baitoushan Volcano Melt inclusions Peralkaline rhyolites Petrologic method Mass balance Volatile emission Climate impact |
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