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New insights into the magmatic evolution of the Imbabura Volcanic Complex, Imbabura province, Ecuador

Wilman Navarrete1 ^^, Jean-Luc Le Pennec2, Gorki Ruiz3, Céline Liorzou2

  • Affiliations: 1Univ. Lille, CNRS, LOG, Laboratoire d'Océanologie et de Géosciences, F 59000, Lille, France; 2Geo-Ocean, University of Brest, CNRS, Ifremer, UMR6538, IRD, IUEM, F 29280 Plouzané, France; 3Facultad de Geología, Minas, Petróleos y Ambiental, Carrera de Ingeniería en Geología, Universidad Central del Ecuador, casilla 872 A, Quito, Ecuador. 

  • Presentation type: Poster

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

  • Poster Board Number: 34

  • Programme No: 1.7.21

  • Theme 1 > Session 7

Abstract

The Imbabura Volcanic Complex is located within the Imbabura Geopark in Ecuador and is considered a potentially active system. The knowledge of its volcanological evolution has improved over time in the literature, yet this was essentially based on radiometric and lithostratigraphic studies, without considering an appropriate geochemical characterization of the magmatic processes and sources. In this work, we review published whole-rock major and trace element contents, Sr-Nd-Pb isotope compositions, petrographic observations and radiometric ages spanning the entire volcanic history of Imbabura (Old volcano and Young edifices). A petrochemical fingerprinting is used to evaluate the magmatic processes related to fractional crystallization (FC) and assimilation-fractional crystallization (AFC) with the timing of volcanism in the Imbabura complex. Our investigation shows that (i) Old Imbabura rocks (~60-40 ka) display a nearly pure FC trend in a log(Rb = incompatible element) vs log(Ni = compatible element) plot and a negative isotopic correlation between Sr and Nd ratios, suggesting that magma differentiation was dominated by olivine±pyroxene fractionation. (ii) After 40 ka: Young Imbabura lavas become more radiogenic in Pb with increasing concentrations of Al2O3 and Fe2O3, Na2O depletion, as well as increasing Th/La ratios. The absence of correlation between Sr and Nd isotopic compositions with silica or any differentiation index, suggests a possible interaction of magmas with the lower crust (with concomitant fractional crystallization of amphibole±pyroxene in the AFC process). This research suggests that the Imbabura Volcanic Complex displays a magmatic plumbing system that has been evolving through time in the Late Pleistocene.