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Multiple, coeval silicic magma storage domains beneath the Laguna Del Maule volcanic field inferred from gravity investigations
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  • Sarah F Trevino,
  • Craig Andrew Miller,
  • Basil Tikoff,
  • Dominique Fournier,
  • Bradley S Singer
Sarah F Trevino
University of Wisconsin - Madison
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Craig Andrew Miller
GNS Science

Corresponding Author:c.miller@gns.cri.nz

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Basil Tikoff
University of Wisconsin-Madison
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Dominique Fournier
Mira Geoscience
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Bradley S Singer
University of Wisconsin-Madison
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The rhyolite-producing Laguna del Maule volcanic field (LdMVF) records magma-induced surface inflation rates of ~ 25 cm/year since 2007. During the Holocene, ~60 meters of cumulative surface uplift is recorded by paleoshorelines of the Laguna del Maule, located on the southeast edge of the LdMVF (Chile-Argentina border) near the Barrancas volcanic complex. Rhyolites from the Barrancas complex erupted over ~14 ka including some of the youngest (1.4 ± 0.6 ka) lava flows in the field. New gravity data collected on the Barrancas complex reveals a Bouguer low (-6 mGal, Barrancas anomaly) that is distinct from the pronounced gravity low (-19 mGal; Lake anomaly) associated with present-day deformation and magma intrusion to the north. Three-dimensional inversion of the Barrancas anomaly indicates the presence of a magma body with a maximum density contrast of -250 kg/m3 centered at a depth of ~ 3 km below surface. Comparison of model densities with measured densities from nearby silicic plutons suggest that a magma body, containing < 30 % melt phase and a low volatile content, exists beneath the Barrancas complex. The Barrancas and Lake gravity lows represent magma in different physical states, associated with past and present-day storage beneath the LdMVF. The gravity model mirrors existing geochemical observations which independently indicate that at least two distinct rhyolites were generated and stored as discrete magma bodies within the broader LdMVF. Small temperature changes of these discrete bodies could reverse crystallization and viscous lock-up and propel magma toward a crystal-poor eruptible state.
Apr 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 4. 10.1029/2020JB020850