Carlos Errázuriz-Henao

The subduction of carbonate-rich biogenic sediments influences Earth’s carbon cycle and regulates long-term climate. Yet, the processes controlling their behavior at the subduction interface remain debated. Here, we investigate the role of carbonate subduction through the petrogenesis of Quaternary rear-arc monogenetic volcanoes in Colombia. These volcanoes display unusual compositions resembling intraplate carbonated peridotite melts and experimental melts from peridotite + CO ₂ systems. Their geochemistry reflects an anomalous mantle source modified by subducted sediments from the Panama Basin, a large-scale region of high primary productivity and carbonate accumulation. However, pristine subducted sediments alone cannot explain the full compositional range of rear-arc Colombian lavas. Instead, we propose that sediment partial melting beneath the arc front produces carbonate- and apatite-rich restites that act as a recycled carbonated component, contributing to mantle chemical heterogeneity. This model helps explain the geochemical diversity of mantle-derived intraplate lavas and establishes a direct link between biogeochemical cycles, subduction, and the evolution of the solid Earth.

The compositions of crustal magmas are powerful tools for understanding the formation and differentiation of continents. However, the geochemical fingerprints that distinguish the two dominant mechanisms of crustal melting, namely dehydration and water-fluxed melting, are still controversial. To provide new insights into this problem, we discuss the petrogenesis of the Paipa Volcanic Complex (PVC), an isolated Quaternary volcanic field in the Colombian Eastern Cordillera. The PVC is characterized by peraluminous trondhjemite-like rhyolites with exceptionally high Na₂O contents (~6 wt %), super-chondritic Nb/Ta (~27), elevated Sr/Y ratios (~120), spoon-shaped REE patterns, and enriched isotopic compositions that overlap with those of the local basement. They also exhibit high pre-eruptive H₂O contents (~up to 9.5 wt %) and abundant Paleozoic zircon inheritances. We demonstrate that these characteristics are inconsistent with a process of intra-crustal differentiation from a mafic or intermediate mantle-derived precursor. Instead, we propose that the origin of the PVC is best explained by melting the local (meta)sedimentary basement under H₂O-saturated conditions, at middle-crustal pressures (~1.3 GPa) and relatively low temperatures (~690–740°C), following the complete breakdown of plagioclase and biotite, and the formation of reactive peritectic amphibole. This scenario differs from the high-temperature dehydration melting conditions that have been widely proposed for the Andes and globally, which result in the production of water undersaturated magmas in equilibrium with anhydrous lithologies rich in plagioclase and/or garnet. Accordingly, we speculate that an external H₂O flux was ultimately sourced from a buoyant, cold, and hydrated mantle wedge that was extensively metasomatized by fluids derived from the Nazca and Caribbean flat-slab fronts. These conditions depressed the asthenospheric mantle potential temperature, likely inhibiting mantle melting. In turn, they facilitated the infiltration and ascent of mantle-derived H₂O through pre-existing crustal faults and shear zones. Our results indicate that water-fluxed melting could be a plausible mechanism for generating crustal magmas in orogenic regions where the availability of free H₂O has been difficult to confirm.

Magmatic arcs modulate global climate over geological timescales through outgassing and rock weathering, but recognizing the fingerprints of climate change in arc magmas remains challenging. Based on a detailed reconstruction of oceanographic, atmospheric, and climatic processes since the middle Miocene, as well as an extensive geochemical database of Miocene and active arc-front magmas from the Trans-Mexican Volcanic Belt, Central American Volcanic Arc, and the North Andean Colombian Arc we developed a conceptual framework by which biogeochemical proxies in oceanic sediments can be tracked down to the composition of arc magmas. Using this framework, we show that the well-documented increases in biologically mediated authigenic Ba and U contents of seafloor sediments from the Eastern Equatorial Pacific (EEP) at the onset of the so-called “carbonate crash” (12–9 Ma) were triggered by an escalation in biological productivity and an augmented efficiency of respiratory carbon storage. We suggest that the temporal modification of the oceanic carbon cycle was regulated by the synchronous formation of three wind-powered seasonal upwellings systems —Tehuantepec, Papagayo, and Panama— that developed in the context of steepening meridional temperature gradients, intensified atmospheric circulation and global climate cooling since the Middle Miocene. Sediments deposited in the context of these newly established upwelling systems became anomalously enriched in authigenic U and Ba not only in comparison to older sediments, but also with respect to geographically adjacent areas of the EEP where vigorous upwellings are absent. These peculiar environmental conditions thus produce a heterogeneous ocean floor that upon subduction and eventual interaction with the mantle wedge creates arc volcanoes with compositional fluctuations that mimic those of the ocean sediments. These findings indicate that the oceanographic and biogeochemical effects of climate change can be engraved on the continental crust and mantle.

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.

El Complejo Volcánico y Glacial Ruiz-Tolima (CVGRT) evidencia los procesos climáticos y tectónicos que han incidido en la formación de la cordillera de los Andes. Mediante la elaboración de un inventario de geomorfositios referenciados espacialmente y con una evaluación de los elementos científicos y adicionales, se plantea la creación de un sistema de georutas o itinerarios geológicos, los cuales ejemplifican cada una de las condiciones que hacen especial la zona de estudio. Dichas georutas sirven como insumo para la creación de una herramienta de geoturismo en procura del aprovechamiento y la conservación de los lugares de interés geomorfológico.