Collaborative Research: Geochemistry and Tectonics of Cretaceous Gateway Closure in the Central American Isthmus

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Planet Earth is divided in three main layers at great depth, the core, the mantle and the crust. The dynamics of the mantle exerts significant control over the evolution of the crust, which in turn shapes the morphology of the surface we see today. Although rare, exposed mantle is found where dramatic tectonic events such as continental collisions have taken place, and these places are essentially windows into our planet. This study will focus on the Santa Elena Peninsula, Costa Rica, a practically unexplored segment of exposed mantle. The observations on the surface will provide valuable information about processes that result in volcanic activity. One goal is to link the Central American geologic history to the development of land-bridges and seaway closures that affected the evolution of global circulation, climate and ecology. These researchers will explore the paleogeography and tectonic evolution of the region through geochemical, petrologic and structural analysis of mantle and associated volcanic rocks of the Santa Elena Peninsula, Costa Rica. This will be the first time the Santa Elena mantle section will be studied with modern analytical techniques. The objectives are to constrain the timing and tectonic environment of formation and consolidation of this terrane. To address these questions the investigators will map the different lithologies and conduct detailed structural analysis. Selected samples of mantle peridotites and other ultramafic lithologies will be studied with electron-microprobe and in-situ laser ablation ICP-MS. Samples from the volcanic units will be analyzed for major, trace element and radiogenic isotope compositions. The analyses will constrain the age of the different lithologies and also the tectonic events that amalgamated the Santa Elena complex. The identification of the complex with a fore-arc, back-arc or mid-ocean ridge tectonic setting will help constrain the large-scale tectonic geometry that led to the closure of the first Central American Gateway during the Cretaceous.