Ancient depleted mantle as a source of boninites in the Izu-Bonin-Mariana arc

Evidence from Os isotopes in Cr-spinel and magnetite

Ryoko Senda, Kenji Shimizu, Katsuhiko Suzuki

研究成果: ジャーナルへの寄稿記事

4 引用 (Scopus)

抄録

Boninite is a volcanic rock derived from shallow melting of highly depleted hydrous mantle, fluxed with water from subducted slabs. The eruption of boninite early in the history of the Izu-Bonin-Mariana (IBM) arc (~ 48–45 Ma), suggests generation by melting of upper mantle material that was relatively unmodified by subducted components. Thus, the boninite composition should largely reflect that of the sub-arc mantle. For better understanding of the mantle sources of nascent arc settings and the contributions of different components to arc melts, we analyzed Os isotope ratios (187Os/188Os) of bulk rocks and mineral separates (euhedral Cr-spinel from boninites and euhedral Cr-spinel/magnetite mixtures from tholeiites younger than 45 Ma that erupted after boninites) from the Bonin Islands and Guam. The age-corrected (initial) Os isotope ratios of the whole-rock samples (0.1179–0.2050) were more radiogenic and variable than those of the mineral separates, possibly because of contamination with crustal materials during magma ascent or alteration after emplacement. The age-corrected Os isotope ratios of euhedral Cr-spinel in boninite from the Bonin Islands (0.1187–0.1254) and from Guam (0.1220–0.1269) are unradiogenic relative to primitive mantle, and those of the Cr-spinel/magnetite mixtures from the tholeiites from the Bonin Islands are similar to or slightly more radiogenic (0.1224–0.1382). The most depleted Os isotope ratio of the Cr-spinel from boninite yielded a model Re depletion (TRD) age of 1.4 Ga, suggesting that the mantle source of the boninite experienced melt extraction prior to 1.4 Ga. The source of the boninites is interpreted to be mostly highly depleted mantle with a small contribution of slab flux arising from altered oceanic crust that has radiogenic Os components, with or without contributions from components with relatively unradiogenic Os such as volcaniclastics of oceanic island basalt affiliation or very young mid-ocean ridge basalt.

元の言語英語
ページ(範囲)110-119
ページ数10
ジャーナルChemical Geology
439
DOI
出版物ステータス出版済み - 11 7 2016
外部発表Yes

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Ferrosoferric Oxide
boninite
Isotopes
spinel
magnetite
isotope
mantle
Minerals
Melting
mantle source
Rocks
slab
Volcanic rocks
melting
melt
mineral
mid-ocean ridge basalt
Contamination
rock
oceanic crust

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology

これを引用

Ancient depleted mantle as a source of boninites in the Izu-Bonin-Mariana arc : Evidence from Os isotopes in Cr-spinel and magnetite. / Senda, Ryoko; Shimizu, Kenji; Suzuki, Katsuhiko.

:: Chemical Geology, 巻 439, 07.11.2016, p. 110-119.

研究成果: ジャーナルへの寄稿記事

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title = "Ancient depleted mantle as a source of boninites in the Izu-Bonin-Mariana arc: Evidence from Os isotopes in Cr-spinel and magnetite",
abstract = "Boninite is a volcanic rock derived from shallow melting of highly depleted hydrous mantle, fluxed with water from subducted slabs. The eruption of boninite early in the history of the Izu-Bonin-Mariana (IBM) arc (~ 48–45 Ma), suggests generation by melting of upper mantle material that was relatively unmodified by subducted components. Thus, the boninite composition should largely reflect that of the sub-arc mantle. For better understanding of the mantle sources of nascent arc settings and the contributions of different components to arc melts, we analyzed Os isotope ratios (187Os/188Os) of bulk rocks and mineral separates (euhedral Cr-spinel from boninites and euhedral Cr-spinel/magnetite mixtures from tholeiites younger than 45 Ma that erupted after boninites) from the Bonin Islands and Guam. The age-corrected (initial) Os isotope ratios of the whole-rock samples (0.1179–0.2050) were more radiogenic and variable than those of the mineral separates, possibly because of contamination with crustal materials during magma ascent or alteration after emplacement. The age-corrected Os isotope ratios of euhedral Cr-spinel in boninite from the Bonin Islands (0.1187–0.1254) and from Guam (0.1220–0.1269) are unradiogenic relative to primitive mantle, and those of the Cr-spinel/magnetite mixtures from the tholeiites from the Bonin Islands are similar to or slightly more radiogenic (0.1224–0.1382). The most depleted Os isotope ratio of the Cr-spinel from boninite yielded a model Re depletion (TRD) age of 1.4 Ga, suggesting that the mantle source of the boninite experienced melt extraction prior to 1.4 Ga. The source of the boninites is interpreted to be mostly highly depleted mantle with a small contribution of slab flux arising from altered oceanic crust that has radiogenic Os components, with or without contributions from components with relatively unradiogenic Os such as volcaniclastics of oceanic island basalt affiliation or very young mid-ocean ridge basalt.",
author = "Ryoko Senda and Kenji Shimizu and Katsuhiko Suzuki",
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T2 - Evidence from Os isotopes in Cr-spinel and magnetite

AU - Senda, Ryoko

AU - Shimizu, Kenji

AU - Suzuki, Katsuhiko

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N2 - Boninite is a volcanic rock derived from shallow melting of highly depleted hydrous mantle, fluxed with water from subducted slabs. The eruption of boninite early in the history of the Izu-Bonin-Mariana (IBM) arc (~ 48–45 Ma), suggests generation by melting of upper mantle material that was relatively unmodified by subducted components. Thus, the boninite composition should largely reflect that of the sub-arc mantle. For better understanding of the mantle sources of nascent arc settings and the contributions of different components to arc melts, we analyzed Os isotope ratios (187Os/188Os) of bulk rocks and mineral separates (euhedral Cr-spinel from boninites and euhedral Cr-spinel/magnetite mixtures from tholeiites younger than 45 Ma that erupted after boninites) from the Bonin Islands and Guam. The age-corrected (initial) Os isotope ratios of the whole-rock samples (0.1179–0.2050) were more radiogenic and variable than those of the mineral separates, possibly because of contamination with crustal materials during magma ascent or alteration after emplacement. The age-corrected Os isotope ratios of euhedral Cr-spinel in boninite from the Bonin Islands (0.1187–0.1254) and from Guam (0.1220–0.1269) are unradiogenic relative to primitive mantle, and those of the Cr-spinel/magnetite mixtures from the tholeiites from the Bonin Islands are similar to or slightly more radiogenic (0.1224–0.1382). The most depleted Os isotope ratio of the Cr-spinel from boninite yielded a model Re depletion (TRD) age of 1.4 Ga, suggesting that the mantle source of the boninite experienced melt extraction prior to 1.4 Ga. The source of the boninites is interpreted to be mostly highly depleted mantle with a small contribution of slab flux arising from altered oceanic crust that has radiogenic Os components, with or without contributions from components with relatively unradiogenic Os such as volcaniclastics of oceanic island basalt affiliation or very young mid-ocean ridge basalt.

AB - Boninite is a volcanic rock derived from shallow melting of highly depleted hydrous mantle, fluxed with water from subducted slabs. The eruption of boninite early in the history of the Izu-Bonin-Mariana (IBM) arc (~ 48–45 Ma), suggests generation by melting of upper mantle material that was relatively unmodified by subducted components. Thus, the boninite composition should largely reflect that of the sub-arc mantle. For better understanding of the mantle sources of nascent arc settings and the contributions of different components to arc melts, we analyzed Os isotope ratios (187Os/188Os) of bulk rocks and mineral separates (euhedral Cr-spinel from boninites and euhedral Cr-spinel/magnetite mixtures from tholeiites younger than 45 Ma that erupted after boninites) from the Bonin Islands and Guam. The age-corrected (initial) Os isotope ratios of the whole-rock samples (0.1179–0.2050) were more radiogenic and variable than those of the mineral separates, possibly because of contamination with crustal materials during magma ascent or alteration after emplacement. The age-corrected Os isotope ratios of euhedral Cr-spinel in boninite from the Bonin Islands (0.1187–0.1254) and from Guam (0.1220–0.1269) are unradiogenic relative to primitive mantle, and those of the Cr-spinel/magnetite mixtures from the tholeiites from the Bonin Islands are similar to or slightly more radiogenic (0.1224–0.1382). The most depleted Os isotope ratio of the Cr-spinel from boninite yielded a model Re depletion (TRD) age of 1.4 Ga, suggesting that the mantle source of the boninite experienced melt extraction prior to 1.4 Ga. The source of the boninites is interpreted to be mostly highly depleted mantle with a small contribution of slab flux arising from altered oceanic crust that has radiogenic Os components, with or without contributions from components with relatively unradiogenic Os such as volcaniclastics of oceanic island basalt affiliation or very young mid-ocean ridge basalt.

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