Uplift and Exhumation of Eclogites and Blueschists in Venezuela: Constraints Based on Structural Analysis, Geothermobarometry, and Geochronology

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The uplift and exhumation of high pressure rocks in orogenic zones is a long-standing problem. A new hypothesis for the uplift and exhumation of blueschists and eclogites has been developed in this project on the basis of structural analysis of Late Cretaceous subduction complex in eastern Venezuela. The observation that these rocks had undergone large extensional strains parallel to the arcuate trend of the subduction zone and the volcanic arc led to a model in which oblique plate convergence changes required large arc-parallel extension and considerable forearc thinning. This renewal will test several aspects of this new model by dating the deformation sequence and determine the pressure-temperature history of particularly the lower grade rocks of the complex, and compare the results to the predictions of the model. Results are expected to test this possible mechanism of returning high pressure rocks to the earth's surface.