A Biogeochemical Imprint of the Panama Basin in the North Andean Arc

Abstract

Oceans and continents mingle at convergent margins. However, the effects of this interaction in the construction and evolution of the continental crust remain poorly understood. Here we use geochemical data from the Panama Basin and the Northern Volcanic Province of Colombia to reveal that the oceanological and biogeochemical processes of a subducted ocean basin are imprinted in the compositions of continental arc volcanoes. The Panama Basin is a biologically highly productive area of the Eastern Equatorial Pacific in which the strongly biogenic sedimentation is reclassified and preserved differently depending on tectonically controlled depositional environments. Due to a shallow lysocline, sediments deposited on newly formed spreading centers are carbonate-rich, whereas those accumulated on older subsiding seafloor become gradually richer in terrigenous components, organic carbon and authigenic U. Volcanoes of the North Volcanic Province of Colombia erupt high-Mg# andesites that are common in some arcs, but display unusually high U contents and a symmetrical or “parabolic-shaped” along-arc trace element and isotopic variations that appear unrelated to differentiation or the pre-existent crustal architecture. Instead, the parabolic-shaped elemental trends mirror the reconstructed compositional variations of sediments deposited across axis on the currently subducted Sandra and Buenaventura ocean ridges. We interpret that subduction of these ocean ridges delivered a compositionally variable sediment influx that influenced the compositions of arc magmas. These findings demonstrate a strong connectivity between oceans and continents, and further imply that arc volcanoes can be reliable records of the oceanological and biogeochemical conditions of long subducted ocean basins.