High MgO lavas (komatiites and picrites) are a rare but important component of the mid-Cretaceous Caribbean plateau large igneous province (LIP). These lava types are critical to understanding mantle temperature and dynamics that lead to their production but are inaccessible in other oceanic LIP provinces. This project is an integrated field, petrological and geochemical study of the recently discovered Tortugal ultramafic/mafic lavas of Costa Rica. Major element, trace element, platinum group element and Sr-Nd-Pb-Os isotope analyses, combined with 40Ar-39Ar dating, will be used to characterize the Tortugal lavas in order to further document the spatial and temporal variability in petrogenesis related to LIP formation in the region. The Tortugal suite is temporally related to the Gorgona Island komatiites, picrites and basalts 1000 km to the southeast, however preliminary data show significant differences in mantle source and thermal regime between the two areas. Understanding the spatial variability in high MgO lavas will help distinguish between rapid decompression melting or plume head models for the creation of the Caribbean plateau.
