Primary magmas at thevolcanic front of the NE Japan arc: Coeval eruption of crustal low-K tholeiitic and mantle-derived medium-K calc-alkaline basalts at Azumavolcano

Toshiro Takahashi, Yuka Hirahara, Takashi Miyazaki, Ryoko Senda, Qing Chang, Jun Ichi Kimura, Yoshiyuki Tatsumi

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

It has long been thought that the low-K tholeiitic (TH) and medium-K calc-alkaline (CA) lavas in the NE Japan arc were produced by fractional crystallization from mantle-derived basalt magmas, and that the latter formed from mixing of mafic and felsic magmas, both derivedfrom a common primaryTH basalt through fractionation. An alternative view was recently proposed on the basis of Sr isotope microanalysis of plagioclase phenocrysts from the Zao volcano, suggesting that (1) the low-K TH basaltic andesites formed by melting of lower crustal amphibolite and that (2) the medium-K CA basalts to andesites formed by mixing of mantle-derived basalt and crustal TH melts. To investigate further the origin of the 'primary' low-K TH and medium-K CA basalts, we investigated basalts and andesites from Azuma volcano. Azuma is a Quaternary eruption center at the volcanic front in the NE Japan arc that has erupted two types of basalt: (1) radiogenic-Sr (87Sr/ 86Sr=0.7058-0.7062) low-K TH basalt lavas without evidence of magma mixing and assimilation; (2) unradiogenic-Sr (87Sr/86Sr=0.7039-0.7041) medium-K CA basalt lavas with subtle evidence for magma mixing. Associated intermediate lavas are voluminous and are all (3) mildly radiogenic-Sr (87Sr/86Sr=0.7044-0.7055) medium-K andesites, all ofwhich have CA affinities with evidence for rigorous magma mixing but no crustal assimilation. The low-K TH basalt has an isotopic composition similar to that of crustal granitoids beneathAzuma and has a composition indicating that it potentially formed from a high-degree lower crustal amphibolite melt. The medium-KCA basalt has a basaltic groundmass with Mg-rich olivine (Fo89) and calcic plagioclase phenocrysts (An90) and the most unradiogenic Sr (87Sr/ 86Sr=0.7037-0.7038), suggesting that it originated from a primary mantle melt. Major and trace elementmicroanalysis of the basaltic groundmass indicates that the primary magma composition iscloseto high-K. We conclude that the mantle-derived basalt at Azuma is the result of a high- to medium-K magma that was later mixed with a low-K TH basalt melt from the amphibolitic lower crust to form medium-K CA basalts and andesites. This supports the view of a lower crustal origin of the low-KTH basalts and simultaneously requires a reappraisal of the origin of theacross-arc variation in K contents of the mantle-derived primary arc basalts, as the high- to medium-K CA basalt is geochemically fairly similar to the high-K rear-arc basalt in the NE Japan arc.

Original languageEnglish
Article numberegs065
Pages (from-to)egs065
JournalJournal of Petrology
Volume54
Issue number1
DOIs
Publication statusPublished - Jan 1 2013

Fingerprint

basalt
volcanic eruptions
Japan
Earth mantle
volcanic eruption
arcs
mantle
andesite
magma
tholeiitic basalt
melt
amphibolite
Volcanoes
assimilation
plagioclase
volcanoes
volcano
Chemical analysis
fractional crystallization
lower crust

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

Primary magmas at thevolcanic front of the NE Japan arc : Coeval eruption of crustal low-K tholeiitic and mantle-derived medium-K calc-alkaline basalts at Azumavolcano. / Takahashi, Toshiro; Hirahara, Yuka; Miyazaki, Takashi; Senda, Ryoko; Chang, Qing; Kimura, Jun Ichi; Tatsumi, Yoshiyuki.

In: Journal of Petrology, Vol. 54, No. 1, egs065, 01.01.2013, p. egs065.

Research output: Contribution to journalArticle

Takahashi, Toshiro ; Hirahara, Yuka ; Miyazaki, Takashi ; Senda, Ryoko ; Chang, Qing ; Kimura, Jun Ichi ; Tatsumi, Yoshiyuki. / Primary magmas at thevolcanic front of the NE Japan arc : Coeval eruption of crustal low-K tholeiitic and mantle-derived medium-K calc-alkaline basalts at Azumavolcano. In: Journal of Petrology. 2013 ; Vol. 54, No. 1. pp. egs065.
@article{83a0de2105f048d79b2ea63af8ad2bc1,
title = "Primary magmas at thevolcanic front of the NE Japan arc: Coeval eruption of crustal low-K tholeiitic and mantle-derived medium-K calc-alkaline basalts at Azumavolcano",
abstract = "It has long been thought that the low-K tholeiitic (TH) and medium-K calc-alkaline (CA) lavas in the NE Japan arc were produced by fractional crystallization from mantle-derived basalt magmas, and that the latter formed from mixing of mafic and felsic magmas, both derivedfrom a common primaryTH basalt through fractionation. An alternative view was recently proposed on the basis of Sr isotope microanalysis of plagioclase phenocrysts from the Zao volcano, suggesting that (1) the low-K TH basaltic andesites formed by melting of lower crustal amphibolite and that (2) the medium-K CA basalts to andesites formed by mixing of mantle-derived basalt and crustal TH melts. To investigate further the origin of the 'primary' low-K TH and medium-K CA basalts, we investigated basalts and andesites from Azuma volcano. Azuma is a Quaternary eruption center at the volcanic front in the NE Japan arc that has erupted two types of basalt: (1) radiogenic-Sr (87Sr/ 86Sr=0.7058-0.7062) low-K TH basalt lavas without evidence of magma mixing and assimilation; (2) unradiogenic-Sr (87Sr/86Sr=0.7039-0.7041) medium-K CA basalt lavas with subtle evidence for magma mixing. Associated intermediate lavas are voluminous and are all (3) mildly radiogenic-Sr (87Sr/86Sr=0.7044-0.7055) medium-K andesites, all ofwhich have CA affinities with evidence for rigorous magma mixing but no crustal assimilation. The low-K TH basalt has an isotopic composition similar to that of crustal granitoids beneathAzuma and has a composition indicating that it potentially formed from a high-degree lower crustal amphibolite melt. The medium-KCA basalt has a basaltic groundmass with Mg-rich olivine (Fo89) and calcic plagioclase phenocrysts (An90) and the most unradiogenic Sr (87Sr/ 86Sr=0.7037-0.7038), suggesting that it originated from a primary mantle melt. Major and trace elementmicroanalysis of the basaltic groundmass indicates that the primary magma composition iscloseto high-K. We conclude that the mantle-derived basalt at Azuma is the result of a high- to medium-K magma that was later mixed with a low-K TH basalt melt from the amphibolitic lower crust to form medium-K CA basalts and andesites. This supports the view of a lower crustal origin of the low-KTH basalts and simultaneously requires a reappraisal of the origin of theacross-arc variation in K contents of the mantle-derived primary arc basalts, as the high- to medium-K CA basalt is geochemically fairly similar to the high-K rear-arc basalt in the NE Japan arc.",
author = "Toshiro Takahashi and Yuka Hirahara and Takashi Miyazaki and Ryoko Senda and Qing Chang and Kimura, {Jun Ichi} and Yoshiyuki Tatsumi",
year = "2013",
month = "1",
day = "1",
doi = "10.1093/petrology/egs065",
language = "English",
volume = "54",
pages = "egs065",
journal = "Journal of Petrology",
issn = "0022-3530",
publisher = "Oxford University Press",
number = "1",

}

TY - JOUR

T1 - Primary magmas at thevolcanic front of the NE Japan arc

T2 - Coeval eruption of crustal low-K tholeiitic and mantle-derived medium-K calc-alkaline basalts at Azumavolcano

AU - Takahashi, Toshiro

AU - Hirahara, Yuka

AU - Miyazaki, Takashi

AU - Senda, Ryoko

AU - Chang, Qing

AU - Kimura, Jun Ichi

AU - Tatsumi, Yoshiyuki

PY - 2013/1/1

Y1 - 2013/1/1

N2 - It has long been thought that the low-K tholeiitic (TH) and medium-K calc-alkaline (CA) lavas in the NE Japan arc were produced by fractional crystallization from mantle-derived basalt magmas, and that the latter formed from mixing of mafic and felsic magmas, both derivedfrom a common primaryTH basalt through fractionation. An alternative view was recently proposed on the basis of Sr isotope microanalysis of plagioclase phenocrysts from the Zao volcano, suggesting that (1) the low-K TH basaltic andesites formed by melting of lower crustal amphibolite and that (2) the medium-K CA basalts to andesites formed by mixing of mantle-derived basalt and crustal TH melts. To investigate further the origin of the 'primary' low-K TH and medium-K CA basalts, we investigated basalts and andesites from Azuma volcano. Azuma is a Quaternary eruption center at the volcanic front in the NE Japan arc that has erupted two types of basalt: (1) radiogenic-Sr (87Sr/ 86Sr=0.7058-0.7062) low-K TH basalt lavas without evidence of magma mixing and assimilation; (2) unradiogenic-Sr (87Sr/86Sr=0.7039-0.7041) medium-K CA basalt lavas with subtle evidence for magma mixing. Associated intermediate lavas are voluminous and are all (3) mildly radiogenic-Sr (87Sr/86Sr=0.7044-0.7055) medium-K andesites, all ofwhich have CA affinities with evidence for rigorous magma mixing but no crustal assimilation. The low-K TH basalt has an isotopic composition similar to that of crustal granitoids beneathAzuma and has a composition indicating that it potentially formed from a high-degree lower crustal amphibolite melt. The medium-KCA basalt has a basaltic groundmass with Mg-rich olivine (Fo89) and calcic plagioclase phenocrysts (An90) and the most unradiogenic Sr (87Sr/ 86Sr=0.7037-0.7038), suggesting that it originated from a primary mantle melt. Major and trace elementmicroanalysis of the basaltic groundmass indicates that the primary magma composition iscloseto high-K. We conclude that the mantle-derived basalt at Azuma is the result of a high- to medium-K magma that was later mixed with a low-K TH basalt melt from the amphibolitic lower crust to form medium-K CA basalts and andesites. This supports the view of a lower crustal origin of the low-KTH basalts and simultaneously requires a reappraisal of the origin of theacross-arc variation in K contents of the mantle-derived primary arc basalts, as the high- to medium-K CA basalt is geochemically fairly similar to the high-K rear-arc basalt in the NE Japan arc.

AB - It has long been thought that the low-K tholeiitic (TH) and medium-K calc-alkaline (CA) lavas in the NE Japan arc were produced by fractional crystallization from mantle-derived basalt magmas, and that the latter formed from mixing of mafic and felsic magmas, both derivedfrom a common primaryTH basalt through fractionation. An alternative view was recently proposed on the basis of Sr isotope microanalysis of plagioclase phenocrysts from the Zao volcano, suggesting that (1) the low-K TH basaltic andesites formed by melting of lower crustal amphibolite and that (2) the medium-K CA basalts to andesites formed by mixing of mantle-derived basalt and crustal TH melts. To investigate further the origin of the 'primary' low-K TH and medium-K CA basalts, we investigated basalts and andesites from Azuma volcano. Azuma is a Quaternary eruption center at the volcanic front in the NE Japan arc that has erupted two types of basalt: (1) radiogenic-Sr (87Sr/ 86Sr=0.7058-0.7062) low-K TH basalt lavas without evidence of magma mixing and assimilation; (2) unradiogenic-Sr (87Sr/86Sr=0.7039-0.7041) medium-K CA basalt lavas with subtle evidence for magma mixing. Associated intermediate lavas are voluminous and are all (3) mildly radiogenic-Sr (87Sr/86Sr=0.7044-0.7055) medium-K andesites, all ofwhich have CA affinities with evidence for rigorous magma mixing but no crustal assimilation. The low-K TH basalt has an isotopic composition similar to that of crustal granitoids beneathAzuma and has a composition indicating that it potentially formed from a high-degree lower crustal amphibolite melt. The medium-KCA basalt has a basaltic groundmass with Mg-rich olivine (Fo89) and calcic plagioclase phenocrysts (An90) and the most unradiogenic Sr (87Sr/ 86Sr=0.7037-0.7038), suggesting that it originated from a primary mantle melt. Major and trace elementmicroanalysis of the basaltic groundmass indicates that the primary magma composition iscloseto high-K. We conclude that the mantle-derived basalt at Azuma is the result of a high- to medium-K magma that was later mixed with a low-K TH basalt melt from the amphibolitic lower crust to form medium-K CA basalts and andesites. This supports the view of a lower crustal origin of the low-KTH basalts and simultaneously requires a reappraisal of the origin of theacross-arc variation in K contents of the mantle-derived primary arc basalts, as the high- to medium-K CA basalt is geochemically fairly similar to the high-K rear-arc basalt in the NE Japan arc.

UR - http://www.scopus.com/inward/record.url?scp=84871538497&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84871538497&partnerID=8YFLogxK

U2 - 10.1093/petrology/egs065

DO - 10.1093/petrology/egs065

M3 - Article

AN - SCOPUS:84871538497

VL - 54

SP - egs065

JO - Journal of Petrology

JF - Journal of Petrology

SN - 0022-3530

IS - 1

M1 - egs065

ER -