In:
Journal of Disaster Research, Fuji Technology Press Ltd., Vol. 17, No. 5 ( 2022-08-01), p. 716-723
Abstract:
High-temperature melting and crystallization experiments were carried out at pressures from 1 atm to 196 MPa and under H 2 O-saturated conditions on the basaltic andesite melt of the Izu-Oshima 1986B eruption (i.e., the B M melt), using a 1-atmosphere f O 2 -controlled furnace and an internally heated pressure vessel. These data were used to constrain the H 2 O-saturated plagioclase liquidus (HSPL) of the melt. The f O 2 conditions were controlled by a mixed H 2 -CO 2 gas at the Ni-NiO (NNO) buffer for the 1 atm experiments, but were not controlled for the high-pressure experiments. Plagioclase is the liquidus phase at 1 atm, whereas early saturation of Fe-Ti oxide above the plagioclase liquidus occurred in the high-pressure experiments due to the elevated f O 2 conditions. The HSPL temperature decreases from 1172 ± 8°C to 1030 ± 20°C as the pressure increases from 1 atm to 196 MPa. A combination of previously proposed models for the plagioclase liquidus and melt H 2 O-solubility can predict the experimentally determined HSPL temperatures, even if oxidation-induced magnetite crystallization occurs. Using these models and the previously reported pre-eruptive temperature of ∼1100 ± 30°C, we estimate the pre-eruptive pressure conditions of the B M melt to be 42 -32 +48 MPa, which corresponds to depths of 1.9 -1.4 +1.9 km. The estimated depth is consistent with that of the shallow active dikes previously identified from geophysical studies, suggesting that the B M melt was derived from a small, shallow magma chamber formed in the shallow dike region.
Type of Medium:
Online Resource
ISSN:
1883-8030
,
1881-2473
DOI:
10.20965/jdr.2022.p0716
Language:
English
Publisher:
Fuji Technology Press Ltd.
Publication Date:
2022
detail.hit.zdb_id:
2740254-X