El Escondido tuff cone (38 ka): a hidden history of monogenetic eruptions in the northernmost volcanic chain in the Colombian Andes

Abstract

El Escondido is a dacitic monogenetic volcano situated in the Samaná monogenetic volcanic field, within the Central Cordillera of Colombia. The tuff cone was emplaced in a deeply incised and rainy mountainous zone, ca. 38 ky ago by an explosive eruption that affected not only the metamorphic and igneous basement but also the remnants of the ~\u2009154 ka Pela Huevos volcano. The El Escondido volcaniclastic deposits are composed of juvenile pumice and lithic fragments including dense volcanic rocks from the Pela Huevos volcano, as well as metamorphic and igneous rocks from the basement. The pumice shows tubes and spongy textures. The volcanic lithics are dominantly angular and fresh, and exhibit different mineralogy and whole-rock geochemistry in comparison to the pumice. Plagioclase and amphibole are ubiquitous; however, biotite and quartz crystals occur only in the pumice fragments (~\u200970 wt% SiO2 volatile-free), whereas olivine and pyroxene crystals are only found in the volcanic lithics (~\u200965 wt% SiO2 volatile-free). The El Escondido tuff cone is strongly eroded and Pela Huevos is a dome-like remnant in the SE sector. Because of this, along with the highly vegetated tropical zone where the volcanoes are emplaced as well as difficult political issues in the region, the edifices were not recognized until recently; this is why the younger cone was named “El Escondido” (which means “The Hidden”). These eruptions evidence that recent volcanism has occurred in a zone of the Central Cordillera that has been considered as non-volcanogenic in recent studies.