New petrochronological evidence for magmatic activity at the Central American arc at ∼100-84 Ma

Abstract

ABSTRACT New detrital zircon petrochronological data (~380 analysed grains), including U-Pb dating, trace element, and isotopic analyses from modern sediments and Oligocene-Miocene strata, cropping out along the western slope of the Baudó Range in the northern Pacific coast of Colombia (Tribugá and Cupica Gulfs), are used to assess the nature of Cretaceous basement rocks. Modern sediments of the Cupica Gulf show the existence of ~100-84 Ma zircons with juvenile isotopic signatures (εHf shifting from +11.0 to +12.9), and subduction-related geochemical features, as indicated by the low content of REE (<4000 ppm), Nb (<14 ppm) and Ti (<6 ppm), and the common presence of positive Ce and Eu anomalies. The detrital ages distribution of the analysed sample from the Cupica Gulf, when compared with new and available detrital zircon U-Pb data (~3500 individual ages) from Cretaceous to Pliocene strata of surrounding regions, is very dissimilar, making it difficult for them to be recycled from older sediments. Instead, we interpret the ~100-84 Ma zircons as derived from arc-related igneous rocks probably exposed along unexplored regions of the axis of the northern Baudó Range, which could be associated with the early growth of the Central American arc. Our new data encourage studying barely explored regions of northwestern South America to test available hypotheses regarding the origin of Cretaceous circum-Caribbean island arcs and its linkages with the tectonics of northwestern South America.