The tectonothermal evolution of the Venezuelan Caribbean Mountain System: 40Ar/39Ar age insights from a Rodinian-related rock, the Cordillera de la Costa and Margarita Island

In the Cordillera de la Costa, magnesiohornblende, phengite, magnesian siderophyllite, ferroan phlogopite and K-feldspar from rock units of the Carayaca and Ávila terranes yield a wide range of ages (275-20 Ma). The oldest ages (275 Ma and 120 Ma) obtained from the Caruao Metatonalite suggest at least two thermal events at these times and are in agreement with the amalgamation of Pangaea and fluid infiltration, respectively. The remaining ages (35-20 Ma) are consistent with previous results and reflect short-lived fluid infiltrations related to tectonothermal events. A phengite age of 35 Ma from an omphacitite lens in the Antímano Marble of the Carayaca Terrane indicates a younger HP/LT event than previously stated. The preservation of this phengite age and constant Si-content profile indicate a short-lived HP/LT event followed by a very rapid exhumation. At 35-20 Ma rocks from the Ávila Terrane remained at shallower crustal levels than the ones of the Carayaca Terrane, but were thermally affected by tectonism and the infiltration of relatively cold and 40Ar-free fluids causing widespread chloritization of trioctahedral micas.