Fluid flow in the subduction channel: Tremolite veins and associated blackwalls in antigoritite (Villa Clara serpentinite mélange, Cuba)

Exotic blocks of massive antigorite-serpentinite (antigoritite) document a deep-seated subduction channel in the Villa Clara serpentinite-matrix mélange, central Cuba. The petrological and geochemical characteristics antigoritite allow distinguishing two types rock: i) ii) dolomite-bearing antigoritite. Both are intimately related field exposures represent deep peridotite infiltrated by H2O-CO2 fluid mixtures that triggered antigoritization local carbonation. Fluid infiltration continued after forming vein network as potential response to hydrofracturing precipitated tremolitite veins fluid-antigoritite reaction blackwalls. mineralogical chemical zoning blackwalls (Atg + Chl Tr adjacent vein) attest for multi-step metasomatic processes during fluid-rock interaction characterized advection infiltrating towards blackwall and, possibly, diffusion out fluid-filled vein. Tentative thermodynamic modeling domain Atg points formation at 400–500 °C 5–10 kbar exhumation channel, suggesting pressurized hydrofracturing. compositions antigoritites, indicate LILE- LREE-enriched evolved from subducting plate, while SrNd isotope systematics compatible with an external composed mixture fluids sediments probably lesser extent, altered oceanic crust.