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

Understanding Geodiversity for Sustainable Development in the Chinchiná River Basin, Caldas, Colombia

“…This allows the formation of several polygenetic and monogenetic volcanoes, including the iconic Nevado The CRB is in the Northern Andean Volcanic Zone, or more specifically in the Northern Volcanic Segment of Colombia, which was formed by the Nazca oceanic lithospheric plate subduction under northern South America [40,42] (Figure 2A). This allows the formation of several polygenetic and monogenetic volcanoes, including the iconic Nevado del Ruiz Volcano [43][44][45][46][47][48][49][50][51][52][53] (Figures 2B and 3A-D). The basin's tectonic history and ongoing orogenic activity in the region has created multiple fault systems that govern its steep and diverse topography.…”

“…Two of the six remaining glaciers in Colombia can be found in the CRB, nourishing the paramo ecosystem, which is recognized for its special water retention capacity, which feeds the downstream rivers, lakes, and aquifers throughout the basin [59][60][61][62] (Figure 3G). del Ruiz Volcano [43][44][45][46][47][48][49][50][51][52][53] (Figures 2B and 3A-D). The basin's tectonic history and ongoing orogenic activity in the region has created multiple fault systems that govern its steep and diverse topography.…”

“…Polygenetic volcanoes are predominantly situated in the southeastern region of the basin, with only one located in the northeastern region (Figure 11A). Conversely, monogenetic volcanoes are primarily distributed in the central region of the basin, where the Villamaría-Termales monogenetic volcanic field is located [46,47], as well as in the northern region of the basin, where the Tapias-Guacaica monogenetic volcanic field is located [51][52][53] (Figure 11A).…”