Timing of subduction and exhumation in a subduction channel: melts from La Corea Melange (eastern Cuba)

High pressure igneous rocks (tonalites), generated by partial melting of subducted basaltic rocks accreted to the mantle wedge, are present in the La Corea serpentinite-matrix melange (eastern Cuba) as centimeter- to meter-sized blocks and as concordant to crosscutting veins within high-pressure parent amphibolite blocks. The slab melts have adakitic signatures, in agreement with formation after partial melting of metabasite. Thermobarometric calculations indicate 620-680 degrees C and 13-15 kbar during crystallization of tonalites and down to 250-300 degrees C, 6 kbar during retrogression, indicating counter-clockwise P-T paths (hot subduction-cool exhumation). Free water required for melting of amphibolite at moderate temperature (700-750 degrees C) and moderate pressure (13-16 kbar) close to the wet basaltic solidus is inferred to have been provided after dehydration of sediments, altered basaltic crust and serpentinite of the subducting Proto-Caribbean lithosphere. Single zircon (SHRIMP) and phengite 40Ar/39Ar age data constrain the P-T-t evolution of the melange from the timing of crystallization of melts at similar to 110-105 Ma to cooling at similar to 87-84 Ma, ca. 350 degrees C, ca. 9 kbar. These figures are consistent with subduction of an oblique ridge, shortly before 115 Ma. Furthermore, our data indicate very slow exhumation (ca. 1 mm/yr) in the subduction channel during the oceanic convergence stage (120-70 Ma) until final fast exhumation to the surface occurred at 70-65 Ma during a regional arc-platform collision event. (C) 2011 Elsevier B.V. All rights reserved.