Pleistocene to Holocene Growth of a Large Upper Crustal Rhyolitic Magma Reservoir beneath the Active Laguna del Maule Volcanic Field, Central Chile

Summary

The rear-arc Laguna del Maule volcanic field (LdM) in the Andean Southern Volcanic Zone, 36°S, is among the most active latest Pleistocene–Holocene rhyolitic centers globally and has been inflating at a rate of > 20 cm a–1 since 2007. At least 50 eruptions during the last 26 kyr allow for a thorough interrogation of changes in the physical and chemical state of this large, ∼20 km diameter, silicic system. Trace element concentrations and Sr, Pb and Th isotope ratios indicate that the mafic precursors to the LdM rhyolites result from mixing between partial melts of garnet-bearing mantle and crust in Th-excess and partial melts of garnet-free crust in U-excess. The 238U/230Th ratios of the LdM lavas are decoupled from the slab fluid signature, similar to several recently studied frontal arc