抄録
Combined Pb-Sr-Nd-Hf-Os isotopes, together with major and trace element compositions, were determined from clinopyroxene and olivine phenocrysts, along with whole rocks, for ocean island basalts with high μ(μ = 238U/204Pb) (HIMU) and enriched mantle isotopic characteristics from Cook-Austral Islands. Clinopyroxene and olivine separates record reliable isotopic information of the sources because of minimized in situ radiogenic ingrowth and their lower susceptibility to crustal contamination. Coherent isotopic systematics in multi-isotope spaces defined by the HIMU samples are best explained by recent mixing of melts derived from the HIMU reservoir and the local shallow mantle. The isotopic compositions of the HIMU reservoir are constrained to be low εNd (≤+4), low εHf (≤+3), and moderately radiogenic 187Os/ 188Os (0.14-0.15) in association with radiogenic Pb isotopes ( 206Pb/204Pb ≥21.5). Since ancient oceanic crust would have had exceptionally radiogenic 187Os/188Os, moderately high 187Os/188Os precludes recycled oceanic crust as the only contributor to the HIMU reservoir. Instead, mantle metasomatized with partial melts from subducted oceanic crust is a likely candidate for the HIMU reservoir. Moreover, partial melting of oceanic crust in equilibrium with Mg perovskite would fractionate U/Pb, Sm/Nd, and Lu/Hf, which are in accordance with the time-integrated U/Pb, Sm/Nd, and Lu/Hf deduced from Pb, Nd, and Hf isotopic compositions of the HIMU reservoir, respectively, with a formation age of 2-3 Ga. We thus propose that the HIMU reservoir was formed by hybridization of a subducted oceanic crust-derived melt with the ambient mantle and then stored for several billion years in the lower mantle.
| 元の言語 | 英語 |
|---|---|
| 記事番号 | Q0AC09 |
| ジャーナル | Geochemistry, Geophysics, Geosystems |
| 巻 | 12 |
| 発行部数 | 2 |
| DOI | |
| 出版物ステータス | 出版済み - 3 1 2012 |
| 外部発表 | Yes |
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All Science Journal Classification (ASJC) codes
- Geophysics
- Geochemistry and Petrology
これを引用
Geochemical characteristics and origin of the HIMU reservoir : A possible mantle plume source in the lower mantle. / Hanyu, Takeshi; Tatsumi, Yoshiyuki; Senda, Ryoko; Miyazaki, Takashi; Chang, Qing; Hirahara, Yuka; Takahashi, Toshiro; Kawabata, Hiroshi; Suzuki, Katsuhiko; Kimura, Jun Ichi; Nakai, Shun'Ichi.
：: Geochemistry, Geophysics, Geosystems, 巻 12, 番号 2, Q0AC09, 01.03.2012.研究成果: ジャーナルへの寄稿 › 記事
}
TY - JOUR
T1 - Geochemical characteristics and origin of the HIMU reservoir
T2 - A possible mantle plume source in the lower mantle
AU - Hanyu, Takeshi
AU - Tatsumi, Yoshiyuki
AU - Senda, Ryoko
AU - Miyazaki, Takashi
AU - Chang, Qing
AU - Hirahara, Yuka
AU - Takahashi, Toshiro
AU - Kawabata, Hiroshi
AU - Suzuki, Katsuhiko
AU - Kimura, Jun Ichi
AU - Nakai, Shun'Ichi
PY - 2012/3/1
Y1 - 2012/3/1
N2 - Combined Pb-Sr-Nd-Hf-Os isotopes, together with major and trace element compositions, were determined from clinopyroxene and olivine phenocrysts, along with whole rocks, for ocean island basalts with high μ(μ = 238U/204Pb) (HIMU) and enriched mantle isotopic characteristics from Cook-Austral Islands. Clinopyroxene and olivine separates record reliable isotopic information of the sources because of minimized in situ radiogenic ingrowth and their lower susceptibility to crustal contamination. Coherent isotopic systematics in multi-isotope spaces defined by the HIMU samples are best explained by recent mixing of melts derived from the HIMU reservoir and the local shallow mantle. The isotopic compositions of the HIMU reservoir are constrained to be low εNd (≤+4), low εHf (≤+3), and moderately radiogenic 187Os/ 188Os (0.14-0.15) in association with radiogenic Pb isotopes ( 206Pb/204Pb ≥21.5). Since ancient oceanic crust would have had exceptionally radiogenic 187Os/188Os, moderately high 187Os/188Os precludes recycled oceanic crust as the only contributor to the HIMU reservoir. Instead, mantle metasomatized with partial melts from subducted oceanic crust is a likely candidate for the HIMU reservoir. Moreover, partial melting of oceanic crust in equilibrium with Mg perovskite would fractionate U/Pb, Sm/Nd, and Lu/Hf, which are in accordance with the time-integrated U/Pb, Sm/Nd, and Lu/Hf deduced from Pb, Nd, and Hf isotopic compositions of the HIMU reservoir, respectively, with a formation age of 2-3 Ga. We thus propose that the HIMU reservoir was formed by hybridization of a subducted oceanic crust-derived melt with the ambient mantle and then stored for several billion years in the lower mantle.
AB - Combined Pb-Sr-Nd-Hf-Os isotopes, together with major and trace element compositions, were determined from clinopyroxene and olivine phenocrysts, along with whole rocks, for ocean island basalts with high μ(μ = 238U/204Pb) (HIMU) and enriched mantle isotopic characteristics from Cook-Austral Islands. Clinopyroxene and olivine separates record reliable isotopic information of the sources because of minimized in situ radiogenic ingrowth and their lower susceptibility to crustal contamination. Coherent isotopic systematics in multi-isotope spaces defined by the HIMU samples are best explained by recent mixing of melts derived from the HIMU reservoir and the local shallow mantle. The isotopic compositions of the HIMU reservoir are constrained to be low εNd (≤+4), low εHf (≤+3), and moderately radiogenic 187Os/ 188Os (0.14-0.15) in association with radiogenic Pb isotopes ( 206Pb/204Pb ≥21.5). Since ancient oceanic crust would have had exceptionally radiogenic 187Os/188Os, moderately high 187Os/188Os precludes recycled oceanic crust as the only contributor to the HIMU reservoir. Instead, mantle metasomatized with partial melts from subducted oceanic crust is a likely candidate for the HIMU reservoir. Moreover, partial melting of oceanic crust in equilibrium with Mg perovskite would fractionate U/Pb, Sm/Nd, and Lu/Hf, which are in accordance with the time-integrated U/Pb, Sm/Nd, and Lu/Hf deduced from Pb, Nd, and Hf isotopic compositions of the HIMU reservoir, respectively, with a formation age of 2-3 Ga. We thus propose that the HIMU reservoir was formed by hybridization of a subducted oceanic crust-derived melt with the ambient mantle and then stored for several billion years in the lower mantle.
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U2 - 10.1029/2010GC003252
DO - 10.1029/2010GC003252
M3 - Article
VL - 12
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
SN - 1525-2027
IS - 2
M1 - Q0AC09
ER -