Pressurizing Magma Within Heterogeneous Crust: A Case Study at the Socorro Magma Body, New Mexico, USA.

Surface deformation plays a key role in illuminating magma transport at active volcanoes, however, unambiguous separation of deep and shallow transport remains elusive. The Socorro Magma Body (SMB) lacks an upper crustal magma transport system, allowing us to link geodetic measurements with predictions of numerical models investigating rheologic heterogeneities and magma‐mush interaction in the mid‐/lower crust. New InSAR observations confirm that a pattern of central surface uplift surrounded by a region of subsidence (previously coined "sombrero" deformation) has persisted over >100 years at the SMB. Our models suggest this pattern may reflect the presence of a large (>100 km width), weaker‐than‐ambient, compliant region (CR) surrounding the mid‐crustal magma body. Interactions between a pressurizing (e.g., due to melt injection and/or volatile exsolution) sill‐like magma body and CR drive the sombrero pattern, depending on both viscoelastic relaxation and pressurization timescales, explaining its rare observation and transient nature. Plain Language Summary: Magma in the crust is transported and stored within magma bodies (regions that are mostly liquid magma) and "mush" (mostly solid crystals and some liquid magma). Mush zones are thought to be too viscous to be erupted but are likely to be weaker than the surrounding rock. To understand volcanic eruptions, it is important to understand the distribution of magma and mush, and their mutual interactions. Here we study these interactions in a mid‐crustal magma body, the Soccorro Magma Body (SMB), that does not have a surface volcano. Surface deformation at the SMB helps us study magma‐mush interaction, especially in the middle or lower crust. Previous surface deformation measurements at the SMB show "sombrero" deformation: a central area of uplift surrounded by a ring of subsidence. New satellite radar measurements are consistent with the previously reported pattern, confirming that this deformation remained remarkably constant through nearly 100 years. We suggest this is due to a large weak, mush region surrounding the SMB. Our computer models reproduce a long‐lasting, consistent sombrero deformation pattern depending on mush properties as well as pressurization history of the magma body, and we suggest these factors may explain why this pattern is relatively rare. Key Points: InSAR confirms coeval subsidence and uplift (a so‐called "sombrero" deformation pattern) persisted for >100 years at the Socorro Magma Body (SMB)A compliant region, modeled as a viscoelastic body surrounding a sill, is able to reproduce both the pattern and duration of deformationViscoelastic deformation within a broad compliant region supports the presence of mush zones at SMB and other mid‐crustal magma bodies [ABSTRACT FROM AUTHOR]