Spatially and Geochemically Anomalous Arc Magmatism: Insights From the Andean Arc

Abstract

While most volcanic arcs show a distinctive spatial relationship to subducting plates, there are many examples where volcanoes occur in anomalous locations. These are commonly also geochemically anomalous relative to the composition of more typical subduction-related rocks. Using Holocene volcanoes in South America as a case study, we document the spatial and geochemical patterns along the Andean volcanic belt. To determine whether spatial variations are also geochemically anomalous, we assess a series of geochemical indices that provide information on the depth and degree of melting, and the role of metasomatic subduction inputs in melt generation. We use these parameters to develop a scori..