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Centennial volcanic cycle revealed by volatiles in melt inclusions at Cotopaxi volcano, Ecuador

^^ Silvana Hidalgo^^ 1, Anais Vásconez 1, Diego Narvaez 2, Benjamin Bernard 1, Jean-Luc Devidal 3, Federica Schiavi3, Pablo Samaniego3

  • Affiliations:  1 Instituto Geofísico, Escuela Politécnica Nacional, Quito-Ecuador; 2 Facultad de Geología, Escuela Politécnica Nacional, Quito-Ecuador; 3 Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, Clermont-Ferrand, France 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 255

  • Programme No: 1.1.41

  • Theme 1 > Session 1

Abstract

Cotopaxi volcano is one of the most active volcanoes in Ecuador and the most dangerous in the country. It has experienced at least four VEI 4-5 eruptions in the last 500 years (i.e., 1742-1744, 1766-1768, 1853 and 1877). We have analyzed major and volatile contents of melt inclusions hosted in plagioclases (An46-79) and clinopyroxene (DiHd0.73-0.80) of the four major eruptions mentioned above and one occurring in the 10th century. These eruptions were chosen because they represent the different eruptive scenario for this volcano. Uncorrected melt inclusion compositions (i.e., 58-72 wt.% SiO2) follow the same trend formed by whole rocks and matrix glass in silica versus MgO, CaO, and Al2O3 plots. The mean volatile contents of all studied melt inclusions are 638±322 for S, 1273±332 for Cl, 667±144 for F, and 2.15±0.98 wt.% H2O. Interestingly, each eruption displays its own geochemical signature. Altogether, the studied eruptions reveal a long-term volcanic cycle at Cotopaxi volcano, characterized by: (1) the differentiation of magma in a deep chamber during a period without major eruptions, (2) highly explosive unrest and eruption of a large volume of evolved magma, (3) intrusion of mafic, volatile-rich magma leading to explosive activity, (4) predominantly effusive eruption of the previously intruded mafic magma, and, finally, (5) the closure of the cycle with the differentiation of the remanent magma. These findings could enhance the ability to forecast eruption styles in the future.