Abstract
238U-230Th-226Ra systematics in lavas from Miyakejima volcano, Japan, are presented to estimate the timescale of magmatic processes beneath an island arc. Miyakejima volcano has four recent eruptive stages (Stages 1-4) starting >7000 BP. 238U-230Th-226Ra disequilibria observed in lavas with large 238U and 226Ra excesses imply metasomatism of depleted mantle by fluid-related processes. This metasomatism is also suggested by trace element and Sr-Nd-Pb isotopic systematics in the same lavas. In the equiline diagram, the trends for two magmatic stages (Stages 1 and 2) are regarded as two different isochrons with a common initial (230Th/232Th) ratio, although the trend for Stages 3 and 4 is a magma mixing line. Our model calculations show that slab-derived fluids can deliver some Th and a very rapid ascent time of the slab components in the mantle wedge (<7 kyr) is inferred. This rapid ascent can be explained by nearly instantaneous material transport in the mantle wedge by a hydrofracture model for fluid and a channel flow model for melt. Such a timescale estimate is not increased even if melting processes that enhance 226Ra are taken into account. The age difference in the equiline diagram corresponds to the interval of individual fluid-release events (13 kyr between Stages 1 and 2, and 5 kyr between Stages 2 and 3 . Thus fluid release from the slab and subsequent magma generation occur as episodic events on a several-kiloyear timescale.
| Original language | English |
|---|---|
| Journal | Journal of Geophysical Research B: Solid Earth |
| Volume | 108 |
| Issue number | 7 |
| Publication status | Published - Jul 10 2003 |
Fingerprint
Keywords
- Miyakejima volcano
- Slab dehydration
- Timescales
- U-series disequilibria
ASJC Scopus subject areas
- Earth and Planetary Sciences (miscellaneous)
- Atmospheric Science
- Geochemistry and Petrology
- Geophysics
- Oceanography
- Space and Planetary Science
- Astronomy and Astrophysics
Cite this
Mantle metasomatism and rapid ascent of slab components beneath island arcs : Evidence from 238U-230Th-226Ra disequilibria of Miyakejima volcano, Izu arc, Japan. / Yokoyama, Tetsuya; Kobayashi, Katsura; Kuritani, Takeshi; Nakamura, Eizou.
In: Journal of Geophysical Research B: Solid Earth, Vol. 108, No. 7, 10.07.2003.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Mantle metasomatism and rapid ascent of slab components beneath island arcs
T2 - Evidence from 238U-230Th-226Ra disequilibria of Miyakejima volcano, Izu arc, Japan
AU - Yokoyama, Tetsuya
AU - Kobayashi, Katsura
AU - Kuritani, Takeshi
AU - Nakamura, Eizou
PY - 2003/7/10
Y1 - 2003/7/10
N2 - 238U-230Th-226Ra systematics in lavas from Miyakejima volcano, Japan, are presented to estimate the timescale of magmatic processes beneath an island arc. Miyakejima volcano has four recent eruptive stages (Stages 1-4) starting >7000 BP. 238U-230Th-226Ra disequilibria observed in lavas with large 238U and 226Ra excesses imply metasomatism of depleted mantle by fluid-related processes. This metasomatism is also suggested by trace element and Sr-Nd-Pb isotopic systematics in the same lavas. In the equiline diagram, the trends for two magmatic stages (Stages 1 and 2) are regarded as two different isochrons with a common initial (230Th/232Th) ratio, although the trend for Stages 3 and 4 is a magma mixing line. Our model calculations show that slab-derived fluids can deliver some Th and a very rapid ascent time of the slab components in the mantle wedge (<7 kyr) is inferred. This rapid ascent can be explained by nearly instantaneous material transport in the mantle wedge by a hydrofracture model for fluid and a channel flow model for melt. Such a timescale estimate is not increased even if melting processes that enhance 226Ra are taken into account. The age difference in the equiline diagram corresponds to the interval of individual fluid-release events (13 kyr between Stages 1 and 2, and 5 kyr between Stages 2 and 3 . Thus fluid release from the slab and subsequent magma generation occur as episodic events on a several-kiloyear timescale.
AB - 238U-230Th-226Ra systematics in lavas from Miyakejima volcano, Japan, are presented to estimate the timescale of magmatic processes beneath an island arc. Miyakejima volcano has four recent eruptive stages (Stages 1-4) starting >7000 BP. 238U-230Th-226Ra disequilibria observed in lavas with large 238U and 226Ra excesses imply metasomatism of depleted mantle by fluid-related processes. This metasomatism is also suggested by trace element and Sr-Nd-Pb isotopic systematics in the same lavas. In the equiline diagram, the trends for two magmatic stages (Stages 1 and 2) are regarded as two different isochrons with a common initial (230Th/232Th) ratio, although the trend for Stages 3 and 4 is a magma mixing line. Our model calculations show that slab-derived fluids can deliver some Th and a very rapid ascent time of the slab components in the mantle wedge (<7 kyr) is inferred. This rapid ascent can be explained by nearly instantaneous material transport in the mantle wedge by a hydrofracture model for fluid and a channel flow model for melt. Such a timescale estimate is not increased even if melting processes that enhance 226Ra are taken into account. The age difference in the equiline diagram corresponds to the interval of individual fluid-release events (13 kyr between Stages 1 and 2, and 5 kyr between Stages 2 and 3 . Thus fluid release from the slab and subsequent magma generation occur as episodic events on a several-kiloyear timescale.
KW - Miyakejima volcano
KW - Slab dehydration
KW - Timescales
KW - U-series disequilibria
UR - http://www.scopus.com/inward/record.url?scp=0142259770&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0142259770&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0142259770
VL - 108
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
SN - 0148-0227
IS - 7
ER -