A 3-D lithospheric model of the Caribbean-South American plate boundary |
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Authors: | Javier Sanchez Hans-Jürgen Götze Michael Schmitz |
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Institution: | 1.Christian-Albrechts-Universit?t zu Kiel,Kiel,Germany;2.FUNVISIS,Caracas,Venezuela |
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Abstract: | A 3-D structural model of the Caribbean-South American plate boundary was constructed by gravity modeling. The model was constrained
by four wide-angle seismic refraction sections, Moho depth estimations from receiver functions, and additionally seismological
hypocenters, surface geology, and geodynamic information. Density values were calculated from empirical velocity-density functions,
and mineralogical-chemical composition considering specific P/T conditions. We tested different structural models for Western
and Eastern Venezuela. In the final model, the fit of the measured and modeled gravity fields for a long Caribbean slab in
Western Venezuela was better than the fit obtained for a short one. This interpretation is consistent with the constraining
data. The slab is interpreted to extend further to the south beneath Northern Colombia and culminates in the area of the seismic
cluster of the Bucaramanga nest. The modeling estimates a slab dip angle under Maracaibo and Mérida Andes of 15°, which increases
to 32° below 100 km depth. The dip direction of approx. N150°E ± 5 increases lightly eastward. In Eastern Venezuela, considering
its short wavelength, lineaments analyzed from gravity data (by curvature methods and Euler deconvolution) seem to be related
to shallow structures and density contrast in the Serranía del Interior and not from a deep detached slab beneath the continental
crust. It is deduced from modeling results that this slab configuration has a very small influence on the gravity field. The
slab was modeled according to the subduction-transform propagation model with purely westward subduction and a slab break
off along a vertical dip-slip tear through the lithosphere. |
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