INTEGRATING SEISMIC, GEOCHEMICAL, AND PETROLOGIC OBSERVATIONS TO UNDERSTAND THE TRANS-LITHOSPHERIC STRUCTURE OF MAGMATIC SYSTEMS: THE SOUTHERN PUNA PLATEAU

Geochemical, petrological, and geophysical datasets are crucial for understanding the structure of magmatic plumbing systems throughout the lithosphere. However, the inferred magmatic architecture beneath volcanoes can vary widely depending on the discipline and/or methodology used to investigate them. Recent studies have worked to integrate these different perspectives into a holistic model, leading to a shift away from the traditional “isolated” magma chamber model toward a more diffuse (“mushy”) trans-lithospheric view of magmatic plumbing systems, but finding individual localities where these diverse datasets can be combined in a robust way has proven difficult.

In this study, we outline the apparently contrasting viewpoints of magma system architecture based on the geophysical and geochemical characteristics of active magmatic systems, and field studies of exposed and extinct magmatic systems. We then investigate a region in the central Andes of South America with good seismic data coverage and compositionally diverse volcanics that has erupted over a relatively small area in the last ∼8 Ma. These data sets reveal evidence for melt stagnation and evolution at two main locations: near the crust-mantle transition and in mid-crustal magma reservoirs. Contextualizing these results with the apparently continuous magmatic structure seen in exposed sections indicates that these contrasting perspectives can be reconciled by understanding the sensitivities and limitations of the individual data sets. Thus, we show that the evidence that has led to the discrete conceptualizations of magma systems often inferred from seismic data or geochemistry are consistent with the more-or-less continuous magmatic architecture observed in the crust of exposed arc sections.