Primary melt from Sannome-gata volcano, NE Japan arc

Constraints on generation conditions of rear-arc magmas

Takeshi Kuritani, Takeyoshi Yoshida, Jun Ichi Kimura, Toshiro Takahashi, Yuka Hirahara, Takashi Miyazaki, Ryoko Senda, Qing Chang, Yoshinori Ito

研究成果: ジャーナルへの寄稿記事

13 引用 (Scopus)

抄録

The conditions under which rear-arc magmas are generated were estimated using primary basalts from the Sannome-gata volcano, located in the rear of the NE Japan arc. Scoriae from the volcano occur with abundant crustal and mantle xenoliths, suggesting that the magma ascended rapidly from the upper mantle. The scoriae show significant variations in their whole-rock compositions (7.9-11.1 wt% MgO). High-MgO scoriae (MgO > ~9.5 wt%) have mostly homogeneous 87Sr/86Sr ratios (0.70318-0.70320), whereas low-MgO scoriae (MgO < ~9 wt%) have higher 87Sr/86Sr ratios (>0.70327); ratios tend to increase with decreasing MgO content. The high-MgO scoriae are aphyric, containing ~5 vol% olivine microphenocrysts with Mg# [100 × Mg/(Mg + Fe2+)] of up to 90. In contrast, the low-MgO scoriae have crustal xenocrysts of plagioclase, alkali feldspar, and quartz, and the mineralogic modes correlate negatively with whole-rock MgO content. On the basis of these observations, it is inferred that the high-MgO scoriae represent primary or near-primary melts, while the low-MgO scoriae underwent considerable interaction with the crust. Using thermodynamic analysis of the observed petrological features of the high-MgO scoriae, the eruption temperature of the magmas was constrained to 1,160-1,220 °C. Given that the source mantle was depleted MORB-source mantle, the primary magma was plausibly generated by ~7 % melting of a garnet-bearing spinel peridotite; taking this into consideration, and considering the constraints of multi-component thermodynamics, we estimated that the primary Sannome-gata magma was generated in the source mantle with 0.5-0.6 wt% H2O at 1,220-1,230 °C and at ~1.8 GPa, and that the H2O content of the primary magma was 6-7 wt%. The rear-arc Sannome-gata magma was generated by a lower degree of melting of the mantle at greater depths and lower temperatures than the frontal-arc magma from the Iwate volcano, which was also estimated to be generated by ~15 % melting of the source mantle with 0.6-0.7 wt% H2O at ~1,250 °C and at ~1.3 GPa.

元の言語英語
ページ(範囲)1-18
ページ数18
ジャーナルContributions to Mineralogy and Petrology
167
発行部数2
DOI
出版物ステータス出版済み - 2 1 2014
外部発表Yes

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Volcanoes
volcanoes
Japan
Earth mantle
Melting
magma
volcano
arcs
melt
mantle source
Bearings (structural)
Rocks
Thermodynamics
Quartz
melting
Garnets
Alkalies
thermodynamics
mantle
Temperature

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

これを引用

Primary melt from Sannome-gata volcano, NE Japan arc : Constraints on generation conditions of rear-arc magmas. / Kuritani, Takeshi; Yoshida, Takeyoshi; Kimura, Jun Ichi; Takahashi, Toshiro; Hirahara, Yuka; Miyazaki, Takashi; Senda, Ryoko; Chang, Qing; Ito, Yoshinori.

:: Contributions to Mineralogy and Petrology, 巻 167, 番号 2, 01.02.2014, p. 1-18.

研究成果: ジャーナルへの寄稿記事

Kuritani, T, Yoshida, T, Kimura, JI, Takahashi, T, Hirahara, Y, Miyazaki, T, Senda, R, Chang, Q & Ito, Y 2014, 'Primary melt from Sannome-gata volcano, NE Japan arc: Constraints on generation conditions of rear-arc magmas', Contributions to Mineralogy and Petrology, 巻. 167, 番号 2, pp. 1-18. https://doi.org/10.1007/s00410-014-0969-7
Kuritani, Takeshi ; Yoshida, Takeyoshi ; Kimura, Jun Ichi ; Takahashi, Toshiro ; Hirahara, Yuka ; Miyazaki, Takashi ; Senda, Ryoko ; Chang, Qing ; Ito, Yoshinori. / Primary melt from Sannome-gata volcano, NE Japan arc : Constraints on generation conditions of rear-arc magmas. :: Contributions to Mineralogy and Petrology. 2014 ; 巻 167, 番号 2. pp. 1-18.
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abstract = "The conditions under which rear-arc magmas are generated were estimated using primary basalts from the Sannome-gata volcano, located in the rear of the NE Japan arc. Scoriae from the volcano occur with abundant crustal and mantle xenoliths, suggesting that the magma ascended rapidly from the upper mantle. The scoriae show significant variations in their whole-rock compositions (7.9-11.1 wt{\%} MgO). High-MgO scoriae (MgO > ~9.5 wt{\%}) have mostly homogeneous 87Sr/86Sr ratios (0.70318-0.70320), whereas low-MgO scoriae (MgO < ~9 wt{\%}) have higher 87Sr/86Sr ratios (>0.70327); ratios tend to increase with decreasing MgO content. The high-MgO scoriae are aphyric, containing ~5 vol{\%} olivine microphenocrysts with Mg# [100 × Mg/(Mg + Fe2+)] of up to 90. In contrast, the low-MgO scoriae have crustal xenocrysts of plagioclase, alkali feldspar, and quartz, and the mineralogic modes correlate negatively with whole-rock MgO content. On the basis of these observations, it is inferred that the high-MgO scoriae represent primary or near-primary melts, while the low-MgO scoriae underwent considerable interaction with the crust. Using thermodynamic analysis of the observed petrological features of the high-MgO scoriae, the eruption temperature of the magmas was constrained to 1,160-1,220 °C. Given that the source mantle was depleted MORB-source mantle, the primary magma was plausibly generated by ~7 {\%} melting of a garnet-bearing spinel peridotite; taking this into consideration, and considering the constraints of multi-component thermodynamics, we estimated that the primary Sannome-gata magma was generated in the source mantle with 0.5-0.6 wt{\%} H2O at 1,220-1,230 °C and at ~1.8 GPa, and that the H2O content of the primary magma was 6-7 wt{\%}. The rear-arc Sannome-gata magma was generated by a lower degree of melting of the mantle at greater depths and lower temperatures than the frontal-arc magma from the Iwate volcano, which was also estimated to be generated by ~15 {\%} melting of the source mantle with 0.6-0.7 wt{\%} H2O at ~1,250 °C and at ~1.3 GPa.",
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T2 - Constraints on generation conditions of rear-arc magmas

AU - Kuritani, Takeshi

AU - Yoshida, Takeyoshi

AU - Kimura, Jun Ichi

AU - Takahashi, Toshiro

AU - Hirahara, Yuka

AU - Miyazaki, Takashi

AU - Senda, Ryoko

AU - Chang, Qing

AU - Ito, Yoshinori

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N2 - The conditions under which rear-arc magmas are generated were estimated using primary basalts from the Sannome-gata volcano, located in the rear of the NE Japan arc. Scoriae from the volcano occur with abundant crustal and mantle xenoliths, suggesting that the magma ascended rapidly from the upper mantle. The scoriae show significant variations in their whole-rock compositions (7.9-11.1 wt% MgO). High-MgO scoriae (MgO > ~9.5 wt%) have mostly homogeneous 87Sr/86Sr ratios (0.70318-0.70320), whereas low-MgO scoriae (MgO < ~9 wt%) have higher 87Sr/86Sr ratios (>0.70327); ratios tend to increase with decreasing MgO content. The high-MgO scoriae are aphyric, containing ~5 vol% olivine microphenocrysts with Mg# [100 × Mg/(Mg + Fe2+)] of up to 90. In contrast, the low-MgO scoriae have crustal xenocrysts of plagioclase, alkali feldspar, and quartz, and the mineralogic modes correlate negatively with whole-rock MgO content. On the basis of these observations, it is inferred that the high-MgO scoriae represent primary or near-primary melts, while the low-MgO scoriae underwent considerable interaction with the crust. Using thermodynamic analysis of the observed petrological features of the high-MgO scoriae, the eruption temperature of the magmas was constrained to 1,160-1,220 °C. Given that the source mantle was depleted MORB-source mantle, the primary magma was plausibly generated by ~7 % melting of a garnet-bearing spinel peridotite; taking this into consideration, and considering the constraints of multi-component thermodynamics, we estimated that the primary Sannome-gata magma was generated in the source mantle with 0.5-0.6 wt% H2O at 1,220-1,230 °C and at ~1.8 GPa, and that the H2O content of the primary magma was 6-7 wt%. The rear-arc Sannome-gata magma was generated by a lower degree of melting of the mantle at greater depths and lower temperatures than the frontal-arc magma from the Iwate volcano, which was also estimated to be generated by ~15 % melting of the source mantle with 0.6-0.7 wt% H2O at ~1,250 °C and at ~1.3 GPa.

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