Trayectoria metamórfica P-T relacionada con subducción en eclogitas del Complejo de Basamento de Samaná, Cordillera Septentrional, República Dominicana

Abstract

Lenses of eclogites from the Punta Balandra unit of the Samaná basement complex, Cordillera Septentrional, Dominican Republic, preserve information of the early metamorphic and tectonic history of subduction in the Greater Antilles island-arc system and their collision with the North America plate. For this reason, these rocks were investigated for reconstruction of quantitative metamorphic P-J paths based upon interpretation of meso and microfabrics, mineral assemblages and mineral chemistry, with the help of equilibrium phase diagrams calculated for specific bulk composition in the model system CKNFMASH and isopleths for selected solution end-members. The obtained subduction-related prograde evolution went from garnet-free first and garnet-bearing next lawsonite-blueschist facies to peak eclogue facies conditions at P=22-24 kbar and 7=6 1 0-625sC. The subsequent retrograde P-T path entered the epidote-blueschist (garnet-free) facies and ended within the greenschist facies, retracing the prograde evolution at low-P (i.e. indicates cooling during the exhumation of the rocks). Thus, Samaná basement complex eclogites and hydrated equivalents formed in a intraoceanic subduction zone in which WSW/W-migrating Atlantic lithosphere was subducted beneath the Caribbean plate. Thrust stacking of different tectonic slices can provide the geological framework for exhumation and cooling due to continuous cool underplating and explains the preservation of high-pressure assemblages.