Mantle transition zone beneath the Caribbean-South American plate boundary and its tectonic implications |
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Authors: | Jianping Huang Elizabeth Vanacore Fenglin Niu Alan Levander |
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Institution: | 1. Section of Earth and Environmental Sciences, Université de Geneve, Rue des Maraichers 13, 1205 Geneva, Switzerland;2. Instituto Colombiano del Petróleo, Ecopetrol, Bucaramanga, Colombia;1. Department of Earth and Environmental Science, University of Geneva, Rue des Maraichers 13, Geneva 1205, Switzerland;2. Thomson Reuters, London, UK;3. Tectonic Analysis Ltd., Geneva, Switzerland;4. Norges Geologiske Undersøkelse, 7491 Trondheim, Norway;5. Geostrat S.A., Quito, Ecuador;6. ETH Zürich, Geological Institute, ETH Zentrum, NO E 59, Sonneggstrasse 5, CH-8092 Zürich, Switzerland;7. Facultad de Geología, Minas y Petróleos, Escuela Politécnica Nacional, A.P. 17-01-2759, Quito, Ecuador |
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Abstract: | We analyzed receiver-function data recorded by a temporary broadband array deployed as part of the BOLIVAR project and the permanent seismic network of Venezuela to study the mantle transition zone structure beneath the Caribbean-South American plate boundary and Venezuela. Significant topography on both the 410-km and the 660-km discontinuities was clearly imaged in the CCP (common-conversion-point) stacked images. Beneath the southeastern Caribbean, the 410-km is featured by a narrow (~ 200 km EW) ~ 25-km uplift extending in the NS direction around 63° west, while the 660-km is depressed by ~ 20 km in a narrow region slightly west to the uplift, a scenario that is more consistent with westward descent of the oceanic South American plate rather than a break-off of NNW dipping proto-Caribbean oceanic lithosphere along the El Pilar Fault. We also found a thick transition zone beneath the Falcon region in northwestern Venezuela, possibly associated with the subducted Nazca plate. A flat 410-km was observed beneath the Guayana shield, suggesting that the shield has a stable and moderately deep keel, which has little effect on the underlying transition zone structure. |
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