Geochemistry and Geochronology of the Guajira Eclogites, northern Colombia : evidence of a metamorphosed primitive Cretaceous Caribbean Island-arc
(Universidad Nacional de Colombia)Cardona, A.
(Smithsonian Tropical Research Institute)Valencia, V.
(The University of Arizona. Department of Geosciences)Altenberger, U.
(Potsdam Universität)López-Martínez, M.
(Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE). Departamento de Geología)Tobón, M.
(Universidad Nacional de Colombia)Zapata, S.
(Universidad Nacional de Colombia)Zapata, G.
(Universidad Nacional de Colombia)Concha, A.E.
(Universidad Nacional de Colombia)
||The chemical composition of eclogites, found as boulders in a Tertiary conglomerate from the Guajira Peninsula, Colombia suggests that these rocks are mainly metamorphosed basaltic andesites. They are depleted in LILE elements compared to MORB, have a negative Nb-anomaly and flat to enriched REE patterns, suggesting that their protoliths evolved in a subduction related tectonic setting. They show island-arc affinities and are similar to primitive islandarc rocks described in the Caribbean. The geochemical characteristics are comparable to low-grade greenschists from the nearby Etpana Terrane, which are interpreted as part of a Cretaceous intra-oceanic arc. These data support evidence that the eclogites and the Etpana terrane rocks formed from the same volcano-sedimentary sequence. Part of this sequence was accreted onto the margin and another was incorporated into the subduction channel and metamorphosed at eclogite facies conditions. 40Ar-39Ar ages of 79. 2±1. 1Ma and 82. 2±2. 5Ma determined on white micas, separated from two eclogite samples, are interpreted to be related to the cooling of the main metamorphic event. The formation of a common volcano-sedimentary protolith and subsequent metamorphism of these units record the ongoing Late Cretaceous continental subduction of the South American margin within the Caribbean intra-oceanic arc subduction zone. This gave way to an arc-continent collision between the Caribbean and the South American plates, where this sequence was exhumed after the Campanian.
||Tots els drets reservats
||article ; publishedVersion
Primitive island-arc ;
Guajira Peninsula ;
||Geologica acta, Vol. 9, Núm. 3-4 (setembre-desembre 2011) , p. 425-443, ISSN 1696-5728
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