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

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A recently proposed model by the PI explains the uplift and exhumation of high pressure/low temperature rocks in NE Venezuela as the result of oblique subduction beneath an arcuate island arc zone that was convex to the ocean. The normal component of convergence is thought to cause arc-normal contraction structures (folds, thrust faults) and the strike-slip component is thought to cause arc-parallel transcurrent faults and shear zones. An increase in curvature of the arc along strike may increase the strike-slip component of convergence, which in turn causes arc- parallel extension and thickness reduction. The terrane is then uplifted to maintain isostatic equilibrium. On Margarita Island and the Araya Peninsula of NE Venezuela, a Late Cretaceous subduction complex/forearc terrane was extended parallel to the Leeward Antilles volcanic island arc during its uplift and retrograde metamorphism. The model outlined can explain the structural geometry of these uplifted subduction-related rocks, but has not yet been rigorously tested. This project will test the model by collecting data from North Central Venezuela for structural analysis and geothermobarometry. Fission track 40Ar/39Ar, U/Pb, and fluid inclusion studies will be combined with the structural and geothermobarometric data to produce pressure- temperature-time-deformation paths for these rocks. The results of this study will greatly enhance our understanding of Caribbean tectonics, and will give significant insight to the problem of rapid uplift of high pressure/low temperature rocks during collisional tectonic processes.