HIGH PRESSURE METAMORPHISM OF OPHIOLITES IN CUBA

Abstract

High-pressure metamorphic complexes of ophiolitic material in Cuba trace the evolution of the northern margin of the Caribbean Plate during the Mesozoic. In the northern ophiolite bell of western and central Cuba, these complexes document cold (i.e., mature) subduction of oceanic lithosphere. Age data indicate subduction during pre-Aptian times followed by mélange formation and uplift during the Aptian-Albian. The P-T evolution is clockwise with relatively hot geothermal gradient during exhumation (i.e., "Alpine-type"), suggesting that exhumation may have been triggered by unroofing processes ensuing arrest of subduction. It is hypothesized that tectonic processes related to termination of subduction led to formation of characteristic oscillatory zoning of garnet recorded in blocks separated by ca. 800 km along strike of the belt. In eastern Cuba, the complexes document hot subduction with peak conditions at ca. 750 °C, 15-18 kbar followed by near-isobaric cooling (i.e., counterclockwise P-T path). The contrasting petrologic evolution in the two regions indicates that the correlation of eastern and western-central Cuban mélanges is doubtful. The age and tectonic context of formation of these hot-subduction complexes is uncertain, but available data are consistent with formation during the Aptian-Albian due to a) the birth of a new subduction zone and/or b) subduction of young oceanic lithosphere or a ridge. Furthermore, tectonic juxtaposition of high-pressure ophiolitic material and subducted platform metasediments in the Escambray complex (central Cuba) that were decompressed under relatively cold geothermal gradients ("Franciscan-type" P-T paths) indicates syn-subduction exhumation during the uppermost Cretaceous (ca. 70 Ma). The diversity of P-T paths, ages and tectonic settings of formation of the high-pressure complexes of ophiolitic material in Cuba document a protracted history of subduction at the northern margin of the Caribbean Plate during the Mesozoic. © UB-ICTJA.