13-5 The Structure and Evolution of a Lithospheric-scale Arc Magma System using Geologically-informed Seismic Images

Session: Toe to Toe: Cordilleran Systems from Trench to Retroarc Domains

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Our understanding of magmatic systems has undergone a revolution in the past decade thanks to improvements in geochemical, petrologic, and geophysical methods. Most now view magmatic system architecture as transcrustal “mushy” magmatic systems thanks to geochemical and petrologic studies that indicate magma storage and differentiation takes place over a range of depths throughout the crust. However, reconciling “big red blobs” common in geophysical images with these transcrustal systems can still be challenging due to shortcomings in our understanding of how geophysical measurements relate to in-situ spatial distributions of melt. In this talk, we will explore how seismic properties can be related to rock composition and melt percentage in a system, and how we can integrate geochemical observations and petrological characteristics of both active and extinct magmatic systems to better understand their architecture and chemical evolution. Our case study will be the Puna Plateau of the Central Andes of South America, as it represents a locality where 1) the tectonic history allows for along-strike variations in the margin to be related to the evolution of a magmatic system, and 2) extensive geochemical and seismic data can be combined to investigate the role of depth-dependent processes in generating particularly large transcrustal magmatic systems. Our seismic results provide spatiotemporal insight into the evolution of silicic magmatic systems that can be reconciled with the geochemical trends and the petrological features of exposed arcs, and provide context through which to interpret seismic images of other magmatic systems.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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