Torfajökull

a radiogenic end-member of the Iceland Pb-isotopic array

Ole Stecher, Richard W. Carlson, Bjørn Gunnarsson

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    Resumé

    Torfajökull is the largest silicic center in Iceland and is located on the eastern branch of Iceland's neovolcanic zone. Torfajökull's location on the Iceland volcanic crust is unique because (1) it is situated behind the tip of a propagating ridge, and (2) several ridge jumps made it possible for lavas to extrude through relatively old basaltic crust (up to 10 Ma). Torfajökull is dominated by large amounts of silicic rocks, with less abundant basaltic and intermediate compositions. Several lavas show evidence of mixing of basaltic and rhyolitic melts. Varying degrees of assimilation of melts from hydrated and metamorphosed basaltic crust into primitive mantle-derived melts have been argued as the key mechanism in generating the variation of rock types and isotopic signatures found in the Icelandic lavas. Torfajökull, with its underlying old basaltic crust, offers the most favourable place to identify the contribution of crustal melts through radiogenic isotope analysis. Our data show that the Torfajökull lavas are among the most radiogenic Sr- and Pb-containing lavas in Iceland, but we find no correlation between major elements and the radiogenic isotope compositions. Basaltic, intermediate and rhyolitic lavas from the Torfajökull silicic center have 87Sr/86Sr- and 143Nd/144Nd-values of 0.70323–0.70342 and 0.512963–0.512999, respectively. Despite a large variation in SiO2 concentrations (50%–74%), there are no significant differences in isotopic compositions between the different rock types. Torfajökull lavas plot towards the high 87Sr/86Sr end of the Icelandic Sr–Nd-isotope array. The Pb-isotope compositions are even more strikingly uniform (206Pb/204Pb 19.168–19.308, 207Pb/204Pb 15.513–15.587, 208Pb/204Pb 38.729–39.066) with no indication of radiogenic enrichment in the silicic lavas. The Pb-isotopic signature of the Torfajökull basaltic and silicic lavas clearly defines the most radiogenic end of the Iceland Pb-isotopic arrays. The radiogenic Sr- and Pb-isotope component of the Iceland isotopic array is well defined as a FoZo (focal zone) mantle component.
    OriginalsprogEngelsk
    TidsskriftEarth and Planetary Science Letters
    Vol/bind165
    Udgave nummer1
    Sider (fra-til)117-127
    Antal sider11
    ISSN0012-821X
    DOI
    StatusUdgivet - 1999

    Citer dette

    Stecher, Ole ; Carlson, Richard W. ; Gunnarsson, Bjørn. / Torfajökull : a radiogenic end-member of the Iceland Pb-isotopic array. I: Earth and Planetary Science Letters. 1999 ; Bind 165, Nr. 1. s. 117-127.
    @article{2aea19e3b73148f2895a2797ba6837dd,
    title = "Torfaj{\"o}kull: a radiogenic end-member of the Iceland Pb-isotopic array",
    abstract = "Torfaj{\"o}kull is the largest silicic center in Iceland and is located on the eastern branch of Iceland's neovolcanic zone. Torfaj{\"o}kull's location on the Iceland volcanic crust is unique because (1) it is situated behind the tip of a propagating ridge, and (2) several ridge jumps made it possible for lavas to extrude through relatively old basaltic crust (up to 10 Ma). Torfaj{\"o}kull is dominated by large amounts of silicic rocks, with less abundant basaltic and intermediate compositions. Several lavas show evidence of mixing of basaltic and rhyolitic melts. Varying degrees of assimilation of melts from hydrated and metamorphosed basaltic crust into primitive mantle-derived melts have been argued as the key mechanism in generating the variation of rock types and isotopic signatures found in the Icelandic lavas. Torfaj{\"o}kull, with its underlying old basaltic crust, offers the most favourable place to identify the contribution of crustal melts through radiogenic isotope analysis. Our data show that the Torfaj{\"o}kull lavas are among the most radiogenic Sr- and Pb-containing lavas in Iceland, but we find no correlation between major elements and the radiogenic isotope compositions. Basaltic, intermediate and rhyolitic lavas from the Torfaj{\"o}kull silicic center have 87Sr/86Sr- and 143Nd/144Nd-values of 0.70323–0.70342 and 0.512963–0.512999, respectively. Despite a large variation in SiO2 concentrations (50{\%}–74{\%}), there are no significant differences in isotopic compositions between the different rock types. Torfaj{\"o}kull lavas plot towards the high 87Sr/86Sr end of the Icelandic Sr–Nd-isotope array. The Pb-isotope compositions are even more strikingly uniform (206Pb/204Pb 19.168–19.308, 207Pb/204Pb 15.513–15.587, 208Pb/204Pb 38.729–39.066) with no indication of radiogenic enrichment in the silicic lavas. The Pb-isotopic signature of the Torfaj{\"o}kull basaltic and silicic lavas clearly defines the most radiogenic end of the Iceland Pb-isotopic arrays. The radiogenic Sr- and Pb-isotope component of the Iceland isotopic array is well defined as a FoZo (focal zone) mantle component.",
    keywords = "mid-ocean ridges, Iceland, acid composition, radioactive isotopes",
    author = "Ole Stecher and Carlson, {Richard W.} and Bj{\o}rn Gunnarsson",
    year = "1999",
    doi = "10.1016/S0012-821X(98)00256-8",
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    volume = "165",
    pages = "117--127",
    journal = "Earth and Planetary Science Letters",
    issn = "0012-821X",
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    Torfajökull : a radiogenic end-member of the Iceland Pb-isotopic array. / Stecher, Ole; Carlson, Richard W.; Gunnarsson, Bjørn.

    I: Earth and Planetary Science Letters, Bind 165, Nr. 1, 1999, s. 117-127.

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    TY - JOUR

    T1 - Torfajökull

    T2 - a radiogenic end-member of the Iceland Pb-isotopic array

    AU - Stecher, Ole

    AU - Carlson, Richard W.

    AU - Gunnarsson, Bjørn

    PY - 1999

    Y1 - 1999

    N2 - Torfajökull is the largest silicic center in Iceland and is located on the eastern branch of Iceland's neovolcanic zone. Torfajökull's location on the Iceland volcanic crust is unique because (1) it is situated behind the tip of a propagating ridge, and (2) several ridge jumps made it possible for lavas to extrude through relatively old basaltic crust (up to 10 Ma). Torfajökull is dominated by large amounts of silicic rocks, with less abundant basaltic and intermediate compositions. Several lavas show evidence of mixing of basaltic and rhyolitic melts. Varying degrees of assimilation of melts from hydrated and metamorphosed basaltic crust into primitive mantle-derived melts have been argued as the key mechanism in generating the variation of rock types and isotopic signatures found in the Icelandic lavas. Torfajökull, with its underlying old basaltic crust, offers the most favourable place to identify the contribution of crustal melts through radiogenic isotope analysis. Our data show that the Torfajökull lavas are among the most radiogenic Sr- and Pb-containing lavas in Iceland, but we find no correlation between major elements and the radiogenic isotope compositions. Basaltic, intermediate and rhyolitic lavas from the Torfajökull silicic center have 87Sr/86Sr- and 143Nd/144Nd-values of 0.70323–0.70342 and 0.512963–0.512999, respectively. Despite a large variation in SiO2 concentrations (50%–74%), there are no significant differences in isotopic compositions between the different rock types. Torfajökull lavas plot towards the high 87Sr/86Sr end of the Icelandic Sr–Nd-isotope array. The Pb-isotope compositions are even more strikingly uniform (206Pb/204Pb 19.168–19.308, 207Pb/204Pb 15.513–15.587, 208Pb/204Pb 38.729–39.066) with no indication of radiogenic enrichment in the silicic lavas. The Pb-isotopic signature of the Torfajökull basaltic and silicic lavas clearly defines the most radiogenic end of the Iceland Pb-isotopic arrays. The radiogenic Sr- and Pb-isotope component of the Iceland isotopic array is well defined as a FoZo (focal zone) mantle component.

    AB - Torfajökull is the largest silicic center in Iceland and is located on the eastern branch of Iceland's neovolcanic zone. Torfajökull's location on the Iceland volcanic crust is unique because (1) it is situated behind the tip of a propagating ridge, and (2) several ridge jumps made it possible for lavas to extrude through relatively old basaltic crust (up to 10 Ma). Torfajökull is dominated by large amounts of silicic rocks, with less abundant basaltic and intermediate compositions. Several lavas show evidence of mixing of basaltic and rhyolitic melts. Varying degrees of assimilation of melts from hydrated and metamorphosed basaltic crust into primitive mantle-derived melts have been argued as the key mechanism in generating the variation of rock types and isotopic signatures found in the Icelandic lavas. Torfajökull, with its underlying old basaltic crust, offers the most favourable place to identify the contribution of crustal melts through radiogenic isotope analysis. Our data show that the Torfajökull lavas are among the most radiogenic Sr- and Pb-containing lavas in Iceland, but we find no correlation between major elements and the radiogenic isotope compositions. Basaltic, intermediate and rhyolitic lavas from the Torfajökull silicic center have 87Sr/86Sr- and 143Nd/144Nd-values of 0.70323–0.70342 and 0.512963–0.512999, respectively. Despite a large variation in SiO2 concentrations (50%–74%), there are no significant differences in isotopic compositions between the different rock types. Torfajökull lavas plot towards the high 87Sr/86Sr end of the Icelandic Sr–Nd-isotope array. The Pb-isotope compositions are even more strikingly uniform (206Pb/204Pb 19.168–19.308, 207Pb/204Pb 15.513–15.587, 208Pb/204Pb 38.729–39.066) with no indication of radiogenic enrichment in the silicic lavas. The Pb-isotopic signature of the Torfajökull basaltic and silicic lavas clearly defines the most radiogenic end of the Iceland Pb-isotopic arrays. The radiogenic Sr- and Pb-isotope component of the Iceland isotopic array is well defined as a FoZo (focal zone) mantle component.

    KW - mid-ocean ridges

    KW - Iceland

    KW - acid composition

    KW - radioactive isotopes

    U2 - 10.1016/S0012-821X(98)00256-8

    DO - 10.1016/S0012-821X(98)00256-8

    M3 - Journal article

    VL - 165

    SP - 117

    EP - 127

    JO - Earth and Planetary Science Letters

    JF - Earth and Planetary Science Letters

    SN - 0012-821X

    IS - 1

    ER -