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Article Dans Une Revue Geochimica et Cosmochimica Acta Année : 2021

Potassium isotopic evidence for sedimentary input to the mantle source of Lesser Antilles lavas

Yan Hu
  • Fonction : Auteur
Fang-Zhen Teng
  • Fonction : Auteur

Résumé

Arc magmas derived from mantle melting often have trace element and isotopic signatures that indicate crustal contributions. The origin and extent of crustal contributions are critical constraints for quantifying crust-mantle recycling at subduction zones; however, it is difficult to distinguish between inputs from the downgoing oceanic slabs and that of the over-riding arc crust. Here we present a novel study using stable potassium (K) isotopes to fingerprint the long-debated crustal signatures in lavas from Martinique Island, Lesser Antilles arc. We find δ41K of Martinique lavas varies from −0.66 to 0.01‰ and correlates with chemical parameters and radiogenic isotope ratios. These correlations cannot be produced by assimilation of arc crust during magma ascent. Rather, they reflect mantle sources that have been modified by the input of subducted sediments. Most lavas display a strong negative correlation between δ41K and radiogenic isotopic compositions, from typical mantle values of −0.37‰ to much lower values of −0.66‰, suggesting the addition of <1% to 5% subducted sediments to their mantle sources. Notable divergence in this correlation occurs for three samples with variably high δ41K (−0.28 to 0.01‰), which is likely caused by the addition of isotopically heavy K-bearing fluids derived from slab dehydration. Our study indicates that a substantial fraction of large ion lithophile elements, including K in arc magmas and thus nascent crust, is inherited from subducted crust; K isotopes are useful tracers of this cycling process

Domaines

Géochimie
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Dates et versions

hal-03327741 , version 1 (27-08-2021)

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Yan Hu, Fang-Zhen Teng, Catherine Chauvel. Potassium isotopic evidence for sedimentary input to the mantle source of Lesser Antilles lavas. Geochimica et Cosmochimica Acta, 2021, 295, pp.98-111. ⟨10.1016/j.gca.2020.12.013⟩. ⟨hal-03327741⟩
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