Thallium Isotopes As Tracers of Recycled Materials in Subduction
1 2 Thallium isotopes as tracers of recycled materials in subduction 3 zones: review and new data for lavas from Tonga-Kermadec and 4 Central America 5 6 7 Sune G. Nielsen1,2, Julie Prytulak3, Jerzy Blusztajn1,2, Yunchao Shu1,2,4,5, Maureen Auro1,2, Marcel 8 Regelous6 and Jim Walker7 9 10 1NIRVANA Laboratories, Woods Hole Oceanographic Institution, Woods Hole, MA, USA 11 2Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA 12 3Department of Earth Science and Engineering, Imperial College London, UK 13 4Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China 14 5University of Chinese Academy of Sciences, Beijing, China 15 6GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany 16 7Department of Geology and Environmental Geosciences, Northern Illinois University, DeKalb, IL, USA 17 1 18 Abstract - Sediment is actively being subducted in every convergent margin worldwide. 19 Yet, geochemical data for arc lavas from several subduction zones, such as Northern Tonga and 20 Costa Rica have revealed either attenuated or limited evidence for sediment in their mantle 21 source regions. Here we use thallium (Tl) isotopes to trace slab components in lavas from the 22 Tonga-Kermadec and Central American arcs. In general, both arcs display Tl isotope data that 23 are most compatible with addition of sediment to the sub-arc mantle from the subducting slab. 24 This evidence is particular strong in the Tonga-Kermadec arc where pelagic clays dominate the 25 Tl budget along the entire arc. Contributions from altered oceanic crust as well as the Louisville 26 Seamount chain that subducts underneath Northern Tonga are not visible in Tl isotopes, which is 27 likely due to the very high Tl concentrations found in pelagic sediments outboard of the Tonga- 28 Kermadec arc.
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