Petrology andTrace Element Budgets of High-pressure Peridotites Indicate Subduction

At Cima di Gagnone, garnet peridotite and chlorite harzburgite lenses within pelitic schists and gneisses correspond to eclogite-facies breakdown products of hydrated peridotites and are suitable for studying dehydration of serpentinized mantle.Thermobarometry and pseudosection modelling yield peak temperatures of 750^8508C and pressures53 GPa.The minimum temperature recorded by the garnet peridotite corresponds to the maximum conditions experienced by the chlorite harzburgite, suggesting that these rocks recrystallized cofa-cially at 8008C. Alternatively, they might have decoupled during subduction, as achieved in tectonically active plate interface bound-aries.The major and rare earth element (REE) variability of the peridotites was mostly acquired during pre-subduction mantle evolu-tion as a result of partial melting and reactive melt flow.The ultra-mafic suite is also characterized by fluid-mobile element enrichments (B, Pb, As, Sb, Cs, Li, U, Be), which confirm deriv