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RESEARCH PRODUCT

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

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article i nfo 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 °C and 13-15 kbar during crystallization of tonalites and down to 250-300 °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 °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 lith- osphere. Single zircon (SHRIMP) and phengite 40 Ar/ 39 Ar age data constrain the P-T-t evolution of the mel- ange from the timing of crystallization of melts at ~110-105 Ma to cooling at ~87-84 Ma, ca. 350 °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 conver- gence stage (120-70 Ma) until final fast exhumation to the surface occurred at 70-65 Ma during a regional arc-platform collision event.