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Kendrick-11Dec'12.docx Click here to view linked References serpentinites trap noble gases and halogens that originate from seawater, diverse crustal lithologies and organic matter. Combined with previous analyses of metamorphosed serpentinites, the new data suggest that approximately 60-70% of the 36 Ar entering subduction zones in serpentinites is lost from chrysotile and/or antigorite and could potentially escape through the forearc. An additional, ~20-30 % of the 36 Ar entering subduction zones in serpentinites is lost during antigorite breakdown and may be cycled through the arc or back-arc, and ~1-10 % of the 36 Ar entering subduction zones in serpentinites may be subducted into the deeper mantle. The data demonstrate decoupling of noble gases, halogens and water during subduction and suggest that subduction-zone fluid fluxes may concentrate noble gases and iodine in newly formed forearc serpentinites. The distinctive I/Cl enrichment of forearc serpentinites suggest that halogen abundance ratios provide a plausible means for inferring the geotectonic setting of serpentinisation in ophiolite samples. The exceptional Cl, Br, I and noble gas concentrations of serpentinites, the potential subduction of the forearc serpentinites and the stability of serpentine minerals to mantle depths of >200 km, imply that serpentinites could dominate the deep recycling budgets of both the heavy halogens and atmospheric noble gases.

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