Effusive and evolved monogenetic volcanoes: two newly identified (~800 ka) cases near Manizales City, Colombia

Abstract Two recently discovered volcanoes (Las Margaritas 1 and 2) located near the city of Manizales in central Colombia (northern Andes) show that monogenetic can be both effusive fed by evolved compositions, unlike most other fields. This study presents results cartographic, petrographic, geochemical, geochronological analyses. Mapping indicates are purely effusive, where first erupted a dome coulée second lava flow. K/Ar dating groundmass yielded emplacement ages 0.77 ± 0.04 0.80 0.05 Ma for each volcano. The rocks contain plagioclase, amphibole, Fe-Ti oxides as ubiquitous minerals, but only one volcano hosts biotite. two also differentiated presence amphibole oxidation rims them. Both andesitic composition have calk-alkaline signature. Trace elements light rare earth element (LREE) enrichment, negative Th, Nb, Ta, Ti anomalies. Overall, indicate equilibrium conditions allowed not phenocrysts microphenocrysts to crystallize, convection stagnation processes zonation glomerocrysts form. This, along with chemical information, subduction characteristics explained small magma batches breaking off from crustal reservoirs. These eruptions thus associated efficient degassing during ascent, while compositional evolution is related relative long-term crust.