Caracterización geoquímica y petrográfica de los productos eruptivos del volcán El Reventador: Período 2002-2018.

Abstract

El Reventador volcano is an andesitic cone located 90 km east of the city of Quito. It is one of the most active volcanos of Ecuador, registering activity since the historic period. After its reactivation in 2002, El Reventador has emitted ash, lava and pyroclastic flows in a series of alternating eruptive events that included effusive and explosive periods. Between 2002 and 2018, the silica contents of El Reventador´s eruptive products changed by up to ~10 SiO2 wt. % from ~53 up to ~63 SiO2 wt. % and three eruptive periods were identified in 2002, 2004-2005 and 2007-2018 according to the geochemical trends for major oxides. Geochemical analysis of the rocks from the 2007-2018 eruptive events identified two additional subgroups between 53 - 57 SiO2 wt. % and 57- 60 SiO2 wt. %.

In this study, different petrogenetic models are used to describe the overall chemical evolution of the volcano in 2007-2018. These models were built according to the chemical and petrographic characteristics of the rocks and describe a fractional crystallization process as the main mechanism of magmatic differentiation. The geochemical modelling was developed in two parts. One using major elements through the approximation of mass balance, and two, using trace elements for Rayleigh fractional crystallization modelling. Based on the results and previous studies, more than one process of differentiation is discussed. At crustal levels, these are: mixing, assimilation, and fractional crystallization. And for the source, a deep mantle probably affected by amphibolite-eclogite facies metamorphism. Subduction-zone metasomatism due to entering fluids into the oceanic trench is also discussed.