Regresar

Geochemical and isotopic variations in a frontal arc volcanic cluster (Chachimbiro-Pulumbura-Pilavo-Yanaurcu, Ecuador)

Abstract:

Volcanic arc clusters are groups of adjacent volcanic edifices that allow the investigation of geochemical changes occurring through time within a limited area (< few hundreds of km2). As such they may increase our understanding of processes that lead to magma differentiation in arcs. Geochemical changes over time in volcanic clusters can be related to source or intracrustal processes. Here, we show that magmatic rocks of 9 edifices of the Chachimbiro-Pulumbura-Pilavo-Yanaurcu volcanic cluster, in the frontal arc of Ecuador, display temporal changes of major and trace elements as well as Pb isotopes during their ~13 Ma long life history (13 Ma to 6 ka). Additionally, geochemical compositions of magmatic rocks of these edifices also become more homogeneous through time. Fractionation, assimilation and recharge models suggest that the changes in geochemical composition and in the compositional spread of erupted materials of the cluster are controlled by an increased depth of magma evolution since ~300–400 ka ago. We propose two speculative scenarios to explain the deepening of magmatic evolutionary processes since ~300–400 ka in the studied cluster. Nonetheless, a higher geochronological and geochemical resolution is needed to determine the cause and exact timing of such a switch as well as its synchronicity or diachroneity with respect to the geochemical changes observed in other volcanic centers along and across the Ecuadorian arc.