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  • Deutsches GeoForschungsZentrum GFZ  (1)
  • IUGG Secretariat, CIRES Cooperative Institute for Research in Environmental Sciences  (1)
  • Alfred-Wegener-Institut für Polarforschung
  • Institut für Meereskunde an der Universität Kiel
  • English  (2)
  • 2000-2004  (2)
Document type
Publisher
Language
Years
Year
  • 1
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    XXIII General Assembly : 30 June - 11 July 2003 ; Sapporo, Japan (2003)
    IUGG Secretariat, CIRES Cooperative Institute for Research in Environmental Sciences
    Details
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
    Format: application/pdf
    Format: application/pdf
    Format: application/pdf
    Format: application/pdf
    Format: application/pdf
    Format: application/pdf
    Format: application/pdf
    Location Call Number Limitation Availability
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    GFZ OAI
  • 2
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    Boron as a tracer for material transfer in subduction zones (2004)
    Deutsches GeoForschungsZentrum GFZ
    In:  Scientific Technical Report STR
    Details
    Publication Date: 2020-02-12
    Description: Late Miocene to Quaternary volcanic rocks from the frontal arc to the back-arc region of the Central Volcanic Zone in the Andes show a wide range of delta 11B values (+4 to -7 ‰) and boron concentrations (6 to 60 ppm). Positive delta 11B values of samples from the volcanic front indicate involvement of a 11B-enriched slab component, most likely derived from altered oceanic crust, despite the thick Andean continental lithosphere, and rule out a pure crust-mantle origin for these lavas. The delta 11B values and B concentrations in the lavas decrease systematically with increasing depth of the Wadati-Benioff Zone. This across-arc variation in delta 11B values and decreasing B/Nb ratios from the arc to the back-arc samples are attributed to the combined effects of B-isotope fractionation during progressive dehydration in the slab and a steady decrease in slab-fluid flux towards the back arc, coupled with a relatively constant degree of crustal contamination as indicated by similar Sr, Nd and Pb isotope ratios in all samples. Modelling of fluid-mineral B-isotope fractionation as a function of temperature fits the across-arc variation in delta 11B and we conclude that the B-isotope composition of arc volcanics is dominated by changing delta 11B composition of B-rich slab-fluids during progressive dehydration. Crustal contamination becomes more important towards the back-arc due to the decrease in slab-derived fluid flux. Because of this isotope fractionation effect, high delta 11B signatures in volcanic arcs need not necessarily reflect differences in the initial composition of the subducting slab. Three-component mixing calculations for slab-derived fluid, the mantle wedge and the continental crust based on B, Sr and Nd isotope data indicate that the slab-fluid component dominates the B composition of the fertile mantle and that the primary arc magmas were contaminated by an average addition of 15 to 30 % crustal material.
    Language: English
    Type: info:eu-repo/semantics/doctoralThesis
    Format: application/pdf
    Location Call Number Limitation Availability
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    GFZ OAI
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