Evidence for the Venecia-Fredonia Monogenetic Volcanic Field as the northernmost Andes volcanism, supported by new geochemical, geochronological and structural data

We propose the existence of a previously undocumented monogenetic volcanic field in northwest Colombia, near Venecia and Fredonia in Antioquia, potentially marking the northernmost Andean volcanic field known to date. This field, situated within the Combia Volcanic Formation, encompasses Cerro Tusa, Cerro El Sillón, and Cerro Bravo—three features traditionally described as hypabyssal bodies but now reinterpreted as volcanic in origin. Petrographic observations of lava flows and bread-crust block deposits suggest a magmatic emplacement, linked to regional fault systems trending N-S and SE-NW, as well as local SW-NE structures, some of which intersect the volcanic features and may correlate with recent earthquake activity.

Petrographic and geochemical analyses conducted at the University of South Florida reveal a calc-alkaline dacitic composition characteristic of subduction-related volcanism. Textural features, including sieve textures, glomerocrysts, and oxidation rims, point to rapid magma ascent and disequilibrium processes. Geochemical diagrams (TAS, AFM, and spider) indicate advanced differentiation, aligning with trends observed in regional monogenetic volcanic fields.

Ongoing Ar/Ar geochronology aims to establish eruption timelines and temporal relationships among sampled units, refining connections to adjacent volcanic fields. These findings contribute to understanding magmatic evolution in the northern Andes and have broader implications for interpreting tectonomagmatic processes in subduction zone settings.