Istituto di Geoscienze e Georisorse     
Scambelluri M., Tonarini S. Boron isotope evidence for shallow fluid transfer across subduction zones by serpentinized mantle. In: Geology, vol. 40 (10) pp. 907 - 910. Geological Society of America, 2012.
Serpentinites formed by alteration of oceanic and forearc mantle are major volatile and fluid-mobile element reservoirs for arc magmatism, though direct proof of their dominance in the subduction-zone volatile cycles has been elusive. Boron isotopes are established markers of fluid-mediated mass transfer during subduction. Altered oceanic crust and sediments have been shown to release in the subarc mantle 11B-depleted fluids, which cannot explain 11B enrichment of many arcs. In contrast to these crustal reservoirs, we document high δ11B values retained in subduction-zone Alpine serpentinites. No 11B fractionation occurs in these rocks with progressive burial: the released 11B-rich fl uids uniquely explain the elevated δ11B of arc magmas. B, O-H, and Sr isotope systems indicate that serpentinization was driven by slab fl uids that infi ltrated the slab-mantle interface early in the subduction history.
URL: http://geology.gsapubs.org/
Subject boron isotopes
Alpine subduction
Erro-Tobbio serpentinites

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