Remobilization of highly crystalline felsic magma by injection of mafic magma

Constraints from the middle sixth century eruption at Haruna volcano, Honshu, Japan

Yuki Suzuki, Setsuya Nakada

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The latest eruption of Haruna volcano at Futatsudake took place in the middle of the sixth century, starting with a Plinian fall, followed by pyroclastic flows, and ending with lava dome formation. Gray pumices found in the first Plinian phase (lower fall) and the dome lavas are the products of mixing between felsic (andesitic) magma having 50 vol. % phenocrysts and mafic magma. The mafic magma was aphyric in the initial phase, whereas it was relatively phyric during the final phase. The aphyric magma is chemically equivalent to the melt part of the phyric mafic magma and probably resulted from the separation of phenocrysts at their storage depth of ∼15 km. The major part of the felsic magma erupted as white pumice, without mixing and heating prior to the eruption, after the mixed magma (gray pumice) and heated felsic magma (white pumice) of the lower fall deposit. Although the mafic magma was injected into the felsic magma reservoir (at ∼7 km depth), part of the product (lower fall ejecta) preceded eruption of the felsic reservoir magma, as a consequence of upward dragging by the convecting reservoir of felsic magma. The mafic magma injection made the nearly rigid felsic magma erupt, letting low-viscosity mixed and heated magmas open the conduit and vent. Indeed the lower fall white pumices preserve a record of syneruptive slow ascent of magma to 2 km depth, probably associated with conduit formation.

Original languageEnglish
Pages (from-to)1543-1567
Number of pages25
JournalJournal of Petrology
Volume48
Issue number8
DOIs
Publication statusPublished - 2007 Aug
Externally publishedYes

Fingerprint

Volcanoes
remobilization
volcanoes
volcanic eruptions
magma
Japan
volcano
volcanic eruption
Domes
injection
Crystalline materials
Vents
pumice
Deposits
Viscosity
Heating
magma chamber
domes
lava dome
pyroclastic flow

Keywords

  • High-crystallinity felsic magma
  • Magma plumbing system
  • Multistage magma mixing
  • Upward dragging of injected magma
  • Vent opening by low-viscosity magma

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

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title = "Remobilization of highly crystalline felsic magma by injection of mafic magma: Constraints from the middle sixth century eruption at Haruna volcano, Honshu, Japan",
abstract = "The latest eruption of Haruna volcano at Futatsudake took place in the middle of the sixth century, starting with a Plinian fall, followed by pyroclastic flows, and ending with lava dome formation. Gray pumices found in the first Plinian phase (lower fall) and the dome lavas are the products of mixing between felsic (andesitic) magma having 50 vol. {\%} phenocrysts and mafic magma. The mafic magma was aphyric in the initial phase, whereas it was relatively phyric during the final phase. The aphyric magma is chemically equivalent to the melt part of the phyric mafic magma and probably resulted from the separation of phenocrysts at their storage depth of ∼15 km. The major part of the felsic magma erupted as white pumice, without mixing and heating prior to the eruption, after the mixed magma (gray pumice) and heated felsic magma (white pumice) of the lower fall deposit. Although the mafic magma was injected into the felsic magma reservoir (at ∼7 km depth), part of the product (lower fall ejecta) preceded eruption of the felsic reservoir magma, as a consequence of upward dragging by the convecting reservoir of felsic magma. The mafic magma injection made the nearly rigid felsic magma erupt, letting low-viscosity mixed and heated magmas open the conduit and vent. Indeed the lower fall white pumices preserve a record of syneruptive slow ascent of magma to 2 km depth, probably associated with conduit formation.",
keywords = "High-crystallinity felsic magma, Magma plumbing system, Multistage magma mixing, Upward dragging of injected magma, Vent opening by low-viscosity magma",
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