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Kalt, Angelika

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Kalt, Angelika
Affiliation principale
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https://libra.unine.ch/handle/123456789/160

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  • Publication
    Accès libre
    Detrital, metamorphic and metasomatic tourmaline in high-pressure metasediments from Syros (Greece): intra-grain boron isotope patterns determined by secondary-ion mass spectrometry
    (2008)
    Marschall, Horst R.
    ;
    Altherr, Rainer
    ;
    Kalt, Angelika 
    ;
    Ludwig, Thomas
    The boron isotopic composition of zoned tourmaline in two metasediments from the island of Syros, determined by secondary-ion mass spectrometry (SIMS), reflects the sedimentary and metamorphic record of the rocks. Tourmaline from a silicate-bearing marble contains small (≤20 μm) detrital cores with highly variable δ11B values (−10.7 to +3.6‰), pointing to a heterogeneous protolith derived from multiple sources. The sedimentary B isotopic record survived the entire metamorphic cycle with peak temperatures of ~500°C. Prograde to peak metamorphic rims are homogeneous and similar among all analysed grains (δ11B ≈ +0.9‰). The varying δ11B values of detrital cores in the siliceous marble demonstrate that in situ B isotope analysis of tourmaline by SIMS is a potentially powerful tool for provenance studies not only in sediments but also in metasediments. A meta-tuffitic blueschist bears abundant tourmaline with dravitic cores of detrital or authigenic origin (δ11B ≈ −3.3‰), and prograde to peak metamorphic overgrowth zones (−1.6‰). Fe-rich rims, formed during influx of B-bearing fluids under retrograde conditions, show strongly increasing δ11B values (up to +7.7‰) towards the margins of the grains. The δ11B values of metamorphic tourmaline from Syros, formed in mixed terrigenous–marine sediments, reflect the B signal blended from these two different sources, and was probably not altered by dehydration during subduction.
  • Publication
    Accès libre
    Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks
    (2006-09-15)
    Marschall, Horst R.
    ;
    Altherr, Rainer
    ;
    Ludwig, Thomas
    ;
    Kalt, Angelika 
    ;
    Gméling, Katalin
    ;
    Kasztovszky, Zsolt
    Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks from the island of Syros (Greece) were studied, using secondary ion mass spectrometry, inductively coupled plasma optical emission spectrometry and prompt gamma neutron activation analysis. Partitioning between coexisting mineral phases was found to be rather constant and independent of element concentrations. For several mineral pairs, apparent partition coefficients vary in a narrow range, while concentrations vary by more than an order of magnitude. Hence, it was possible to establish sets of inter-mineral partition coefficients for Li, Be and B among 15 different high-pressure minerals. This data set provides important information on the behaviour of the light elements in different lithologies within subducting slabs from the onset of metamorphism to the eclogite stage. It is essential for modelling trace-element and isotope fractionation during subduction and dehydration of oceanic crust.