Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin

John Caulfield, Simon Turner*, Richard Arculus, Chris Dale, Frances Jenner, Julian Pearce, Colin Macpherson, Heather Handley

*Corresponding author for this work

    Research output: Contribution to journalArticle

    12 Citations (Scopus)

    Abstract

    The Fonualei Spreading Center affords an excellent opportunity to evaluate geochemical changes with increasing depth to the slab in the Lau back-arc basin. We present H2O and CO2 concentrations and Sr, Nd, Pb, Hf and U-Th-Ra isotope data for selected glasses as well as new Hf isotope data from boninites and seamounts to the north of the Tonga arc. The Pb and Hf isotope data are used to show that mantle flow is oriented to the southwest and that the tear in the northern end of the slab may not extend east as far as the boninite locality. Along the Fonualei Spreading Center, key geochemical parameters change smoothly with increasing distance from the arc front and increasing slab surface temperatures. The latter may range from 720 to 866 degrees C, based on decreasing H2O/Ce ratios. Consistent with experimental data, the geochemical trends are interpreted to reflect changes in the amount and composition of wet pelite melts or super-critical fluids and aqueous fluids derived from the slab. With one exception, all of the lavas preserve both U-238 excesses and Ra-226 excesses. We suggest that lavas from the Fonualei Spreading Center and Valu Fa Ridge are dominated by fluid-fluxed melting whereas those from the East and Central Lau Spreading Centers, where slab surface temperatures exceed similar to 850-900 degrees C, are largely derived through decompression. A similar observation is found for the Manus and East Scotia back-arc basins and may reflect the expiry of a key phase such as lawsonite in the subducted basaltic crust.

    Original languageEnglish
    Article number11209
    Number of pages17
    JournalJournal of Geophysical Research
    Volume117
    Issue number11
    DOIs
    Publication statusPublished - 21 Nov 2012

    Keywords

    • TRACE-ELEMENT SIGNATURE
    • SUBDUCTION-ZONE FLUIDS
    • KERMADEC ISLAND-ARC
    • COLLECTOR-ICP-MS
    • TH-230-U-238 DISEQUILIBRIUM
    • MAGMA EVOLUTION
    • ISOTOPE RATIOS
    • SEDIMENT MELTS
    • MARIANA ARC
    • FLUX RATES

    Cite this

    Caulfield, J., Turner, S., Arculus, R., Dale, C., Jenner, F., Pearce, J., ... Handley, H. (2012). Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin. Journal of Geophysical Research, 117(11), [11209]. https://doi.org/10.1029/2012JB009526
    Caulfield, John ; Turner, Simon ; Arculus, Richard ; Dale, Chris ; Jenner, Frances ; Pearce, Julian ; Macpherson, Colin ; Handley, Heather. / Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin. In: Journal of Geophysical Research. 2012 ; Vol. 117, No. 11.
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    title = "Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin",
    abstract = "The Fonualei Spreading Center affords an excellent opportunity to evaluate geochemical changes with increasing depth to the slab in the Lau back-arc basin. We present H2O and CO2 concentrations and Sr, Nd, Pb, Hf and U-Th-Ra isotope data for selected glasses as well as new Hf isotope data from boninites and seamounts to the north of the Tonga arc. The Pb and Hf isotope data are used to show that mantle flow is oriented to the southwest and that the tear in the northern end of the slab may not extend east as far as the boninite locality. Along the Fonualei Spreading Center, key geochemical parameters change smoothly with increasing distance from the arc front and increasing slab surface temperatures. The latter may range from 720 to 866 degrees C, based on decreasing H2O/Ce ratios. Consistent with experimental data, the geochemical trends are interpreted to reflect changes in the amount and composition of wet pelite melts or super-critical fluids and aqueous fluids derived from the slab. With one exception, all of the lavas preserve both U-238 excesses and Ra-226 excesses. We suggest that lavas from the Fonualei Spreading Center and Valu Fa Ridge are dominated by fluid-fluxed melting whereas those from the East and Central Lau Spreading Centers, where slab surface temperatures exceed similar to 850-900 degrees C, are largely derived through decompression. A similar observation is found for the Manus and East Scotia back-arc basins and may reflect the expiry of a key phase such as lawsonite in the subducted basaltic crust.",
    keywords = "TRACE-ELEMENT SIGNATURE, SUBDUCTION-ZONE FLUIDS, KERMADEC ISLAND-ARC, COLLECTOR-ICP-MS, TH-230-U-238 DISEQUILIBRIUM, MAGMA EVOLUTION, ISOTOPE RATIOS, SEDIMENT MELTS, MARIANA ARC, FLUX RATES",
    author = "John Caulfield and Simon Turner and Richard Arculus and Chris Dale and Frances Jenner and Julian Pearce and Colin Macpherson and Heather Handley",
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    Caulfield, J, Turner, S, Arculus, R, Dale, C, Jenner, F, Pearce, J, Macpherson, C & Handley, H 2012, 'Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin', Journal of Geophysical Research, vol. 117, no. 11, 11209. https://doi.org/10.1029/2012JB009526

    Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin. / Caulfield, John; Turner, Simon; Arculus, Richard; Dale, Chris; Jenner, Frances; Pearce, Julian; Macpherson, Colin; Handley, Heather.

    In: Journal of Geophysical Research, Vol. 117, No. 11, 11209, 21.11.2012.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin

    AU - Caulfield, John

    AU - Turner, Simon

    AU - Arculus, Richard

    AU - Dale, Chris

    AU - Jenner, Frances

    AU - Pearce, Julian

    AU - Macpherson, Colin

    AU - Handley, Heather

    PY - 2012/11/21

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    N2 - The Fonualei Spreading Center affords an excellent opportunity to evaluate geochemical changes with increasing depth to the slab in the Lau back-arc basin. We present H2O and CO2 concentrations and Sr, Nd, Pb, Hf and U-Th-Ra isotope data for selected glasses as well as new Hf isotope data from boninites and seamounts to the north of the Tonga arc. The Pb and Hf isotope data are used to show that mantle flow is oriented to the southwest and that the tear in the northern end of the slab may not extend east as far as the boninite locality. Along the Fonualei Spreading Center, key geochemical parameters change smoothly with increasing distance from the arc front and increasing slab surface temperatures. The latter may range from 720 to 866 degrees C, based on decreasing H2O/Ce ratios. Consistent with experimental data, the geochemical trends are interpreted to reflect changes in the amount and composition of wet pelite melts or super-critical fluids and aqueous fluids derived from the slab. With one exception, all of the lavas preserve both U-238 excesses and Ra-226 excesses. We suggest that lavas from the Fonualei Spreading Center and Valu Fa Ridge are dominated by fluid-fluxed melting whereas those from the East and Central Lau Spreading Centers, where slab surface temperatures exceed similar to 850-900 degrees C, are largely derived through decompression. A similar observation is found for the Manus and East Scotia back-arc basins and may reflect the expiry of a key phase such as lawsonite in the subducted basaltic crust.

    AB - The Fonualei Spreading Center affords an excellent opportunity to evaluate geochemical changes with increasing depth to the slab in the Lau back-arc basin. We present H2O and CO2 concentrations and Sr, Nd, Pb, Hf and U-Th-Ra isotope data for selected glasses as well as new Hf isotope data from boninites and seamounts to the north of the Tonga arc. The Pb and Hf isotope data are used to show that mantle flow is oriented to the southwest and that the tear in the northern end of the slab may not extend east as far as the boninite locality. Along the Fonualei Spreading Center, key geochemical parameters change smoothly with increasing distance from the arc front and increasing slab surface temperatures. The latter may range from 720 to 866 degrees C, based on decreasing H2O/Ce ratios. Consistent with experimental data, the geochemical trends are interpreted to reflect changes in the amount and composition of wet pelite melts or super-critical fluids and aqueous fluids derived from the slab. With one exception, all of the lavas preserve both U-238 excesses and Ra-226 excesses. We suggest that lavas from the Fonualei Spreading Center and Valu Fa Ridge are dominated by fluid-fluxed melting whereas those from the East and Central Lau Spreading Centers, where slab surface temperatures exceed similar to 850-900 degrees C, are largely derived through decompression. A similar observation is found for the Manus and East Scotia back-arc basins and may reflect the expiry of a key phase such as lawsonite in the subducted basaltic crust.

    KW - TRACE-ELEMENT SIGNATURE

    KW - SUBDUCTION-ZONE FLUIDS

    KW - KERMADEC ISLAND-ARC

    KW - COLLECTOR-ICP-MS

    KW - TH-230-U-238 DISEQUILIBRIUM

    KW - MAGMA EVOLUTION

    KW - ISOTOPE RATIOS

    KW - SEDIMENT MELTS

    KW - MARIANA ARC

    KW - FLUX RATES

    U2 - 10.1029/2012JB009526

    DO - 10.1029/2012JB009526

    M3 - Article

    VL - 117

    JO - Journal of Geophysical Research

    JF - Journal of Geophysical Research

    SN - 0148-0227

    IS - 11

    M1 - 11209

    ER -