90-1 A Multidisciplinary Approach to Understanding the Seismic Structure of Arc Systems

Abstract:

Seismic techniques are a common way to resolve where melt resides throughout the lithosphere in an active magmatic system. However, they often struggle to constrain the presence of magma at depths where geochemical and petrologic studies indicate magma storage and differentiation takes place, particularly below the "big red blobs" that characterize the shallow portion of the magmatic system. This is because 1) seismic arrays often lack the aperture and station density necessary to resolve the translithospheric system at the necessary resolution, and 2) we generally have a poor understanding of how seismic measurements relate to spatial distributions of melt.

In this study, we will explore how seismic properties can be related to rock composition and melt percentage, and how we can integrate geochemical observations and petrological characteristics from both active and extinct magmatic systems to better understand their architecture and evolution. To do this, we turn to the large, long-lived magmatic systems of the southern Altiplano and Puna Plateau, where existing geochemical and petrological data are abundant and seismic data are sufficient to image the entire translithospheric magmatic system. In addition, the tectonic history of the region allows for along-strike variations in the margin to be related to the evolution of a thermally-maturing silicic magmatic system. Our seismic results provide spatiotemporal insight into the evolution of a silicic magmatic system that can be reconciled with the geochemical trends and the petrological features of exposed arcs. This study provides a framework to investigate more typical (i.e., smaller) arc magmatic systems, which may require alternative imaging approaches to delineate the distribution of melt in the crust, and will allow us to move toward a more comprehensive multidisciplinary model of arc magmatic systems.

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