Petrogenesis of magmas in the Antillanca Volcanic Complex (AVC) (S. Chile) over space and time

Abstract

Crater Rayhuén within the Antillanca Volcanic Complex (AVC) in southern Chile is known as a monogenetic system. That is, the system contains simple chemistry and is not affected by igneous processes such as assimilation, magma mixing and has limited fractionation. However, the samples studied here show evidence for multiple mixing events as well as fractional crystallisation. Here, petrology, geochemical data and thermodynamic modelling is used to provide evidence of these processes. Petrogenesis is interpreted through the system’s chemistry and comparison to nearby volcanoes of the same source. Results yield sieve and zoning textures which are interpreted to be evidence for multiple mixing events. Geochemical data plotted with thermodynamic modelling as well as fractionation vectors illustrate that anorthite fractionation was a dominant and important part of the system’s magmatic history. This study reveals that Crater Rayhuén’s magmatic history is much more complex than first thought and as such either does not fit within the definition of a monogenetic system or there is a need to re-evaluate the way we think about monogenetic volcanism.