Abstract
A 150-km-wide ground deformation anomaly in the Altiplano-Puna volcanic complex (APVC) of the Central Andes, with uplift centered on Uturuncu volcano and peripheral subsidence, alludes to complex subsurface stress changes. In particular, the role of a large, geophysically anomalous and partially molten reservoir (the Altiplano-Puna magma body, APMB), located ∼ 20 km beneath the deforming surface, is still poorly understood. To explain the observed spatiotemporal ground deformation pattern, we integrate geophysical and petrological data and develop a numerical model that accounts for a mechanically heterogeneous and viscoelastic crust. Best-fit models imply subsurface stress changes due to the episodic reorganization of an interconnected vertically extended mid-crustal plumbing system composed of the APMB and a domed bulge and column structure. Measured gravity-height gradient data point toward low-density fluid migration as the dominant process behind these stress changes. We calculate a mean annual flux of ∼ 2 × 10 7 m 3 of water-rich andesitic melt and/or magmatic water from the APMB into the bulge and column structure accompanied by modest pressure changes of 100 yr) residual deformation at Uturuncu. Episodic mush reorganization may be a ubiquitous characteristic of the magmatic evolution of the APVC.
Highlights
The structural and chemical evolution of continental crust is intimately linked to igneous differentiation processes (e.g., Hawkesworth and Kemp, 2006)
Several geophysical methods have detected anomalies under the Altiplano-Puna volcanic complex (APVC) that are interpreted as the Altiplano-Puna magma body (APMB)
Many novel findings on the subsurface architecture and petrology of the APMB as well as Uturuncu volcano are presented in this themed Geosphere issue as a result of the PLUTONS project
Summary
The structural and chemical evolution of continental crust is intimately linked to igneous differentiation processes (e.g., Hawkesworth and Kemp, 2006). Satellite remote sensing studies identified a large (>70 km wide) near circular area of surface deformation (Pritchard and Simons, 2002) centered on Cerro Uturuncu (22.270 ̊S, 67.180 ̊W), a 6008-m-high Pleistocene dacitic volcano (e.g., Sparks et al, 2008) in the Altiplano-Puna volcanic complex (APVC; de Silva, 1989). Several explanations have been proposed for the deformation anomaly, including the pressurization of subsurface cavities (as a proxy for magma reservoirs) located at various crustal depths above, within, and below the APMB, and complex interactions between multiple magmatic systems located at upper to lower crustal levels (Pritchard and Simons, 2002; Sparks et al, 2008; Hickey et al, 2013).
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have