Inherited Pb isotopic records in olivine antecryst-hosted melt inclusions from Hawaiian lavas

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Abstract

Dislocation textures of olivine grains and Pb isotopic compositions ( 207Pb/ 206Pb and 208Pb/ 206Pb) of olivine-hosted melt inclusions in basaltic lavas from three Hawaiian volcanoes (Kilauea, Mauna Loa, and Koolau) were examined. More than 70% of the blocky olivine grains in the studied samples have a regular-shaped dislocation texture with their dislocation densities exceeding 10 6cm -2, and can be considered as deformed olivine. The size distribution of blocky olivine grains shows that more than 99% of blocky olivines coarser than 1.2mm are identified as deformed olivine. These deformed olivine grains are identified as antecrysts, which originally crystallized from previous stages of magmatism in the same shield, followed by plastic deformation prior to entrainment in the erupted host magmas. This study revealed that entrainment of mantle-derived crystallization products by younger batches of magma is an important part of the evolution of magnesium-rich Hawaiian magma. Lead isotopic compositions of melt inclusions hosted in the olivine antecrysts provide information of the evolutionary history of Hawaiian volcanoes which could not have been accessed if only whole rock analyses were carried out. Antecryst-hosted melt inclusions in Kilauea and Koolau lavas demonstrate that the source components in the melting region changed during shield formation. In particular, evidence of interaction of plume-derived melts and upper mantle was observed in the earliest stage of Koolau magmatism.

Original languageEnglish
Pages (from-to)169-195
Number of pages27
JournalGeochimica et Cosmochimica Acta
Volume95
DOIs
Publication statusPublished - Oct 15 2012

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melt inclusion
olivine
dislocation
Volcanoes
entrainment
magmatism
shield
isotopic composition
volcano
Textures
texture
magma
plastic deformation
Crystallization
Chemical analysis
Magnesium
upper mantle
magnesium
Plastic deformation
Melting

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

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title = "Inherited Pb isotopic records in olivine antecryst-hosted melt inclusions from Hawaiian lavas",
abstract = "Dislocation textures of olivine grains and Pb isotopic compositions ( 207Pb/ 206Pb and 208Pb/ 206Pb) of olivine-hosted melt inclusions in basaltic lavas from three Hawaiian volcanoes (Kilauea, Mauna Loa, and Koolau) were examined. More than 70{\%} of the blocky olivine grains in the studied samples have a regular-shaped dislocation texture with their dislocation densities exceeding 10 6cm -2, and can be considered as deformed olivine. The size distribution of blocky olivine grains shows that more than 99{\%} of blocky olivines coarser than 1.2mm are identified as deformed olivine. These deformed olivine grains are identified as antecrysts, which originally crystallized from previous stages of magmatism in the same shield, followed by plastic deformation prior to entrainment in the erupted host magmas. This study revealed that entrainment of mantle-derived crystallization products by younger batches of magma is an important part of the evolution of magnesium-rich Hawaiian magma. Lead isotopic compositions of melt inclusions hosted in the olivine antecrysts provide information of the evolutionary history of Hawaiian volcanoes which could not have been accessed if only whole rock analyses were carried out. Antecryst-hosted melt inclusions in Kilauea and Koolau lavas demonstrate that the source components in the melting region changed during shield formation. In particular, evidence of interaction of plume-derived melts and upper mantle was observed in the earliest stage of Koolau magmatism.",
author = "Sakyi, {Patrick Asamoah} and Ryoji Tanaka and Katsura Kobayashi and Eizou Nakamura",
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AU - Nakamura, Eizou

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N2 - Dislocation textures of olivine grains and Pb isotopic compositions ( 207Pb/ 206Pb and 208Pb/ 206Pb) of olivine-hosted melt inclusions in basaltic lavas from three Hawaiian volcanoes (Kilauea, Mauna Loa, and Koolau) were examined. More than 70% of the blocky olivine grains in the studied samples have a regular-shaped dislocation texture with their dislocation densities exceeding 10 6cm -2, and can be considered as deformed olivine. The size distribution of blocky olivine grains shows that more than 99% of blocky olivines coarser than 1.2mm are identified as deformed olivine. These deformed olivine grains are identified as antecrysts, which originally crystallized from previous stages of magmatism in the same shield, followed by plastic deformation prior to entrainment in the erupted host magmas. This study revealed that entrainment of mantle-derived crystallization products by younger batches of magma is an important part of the evolution of magnesium-rich Hawaiian magma. Lead isotopic compositions of melt inclusions hosted in the olivine antecrysts provide information of the evolutionary history of Hawaiian volcanoes which could not have been accessed if only whole rock analyses were carried out. Antecryst-hosted melt inclusions in Kilauea and Koolau lavas demonstrate that the source components in the melting region changed during shield formation. In particular, evidence of interaction of plume-derived melts and upper mantle was observed in the earliest stage of Koolau magmatism.

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