The time and length scales of magma mixing: The natural laboratory of Volcan Quizapu, Chile

Injection of magma from the lower crust and mantle into pre-existing shallow crustal magma reservoirs is major control on the eruptive behavior of the volcanoes and the diversity of volcanic rocks found on the Earth surface. The first section of this study examines magma mixing caused by gas-driven overturn and the response of dispersed crystals in recharge and residing magma. Large-scale redistribution of crystals during a single overturn is predicted, resulting in crystal-melt chemical disequilibria. Furthermore, it is predicted that the overturn time scale is (1) short compared to the response time scale of crystallization and (2) similar to the response time scale of dissolution.;The second part of this work focuses on the process of magma mixing in the natural system of Volcan Quizapu and its historic eruptions of 1846/47 and 1932. In contrast, to most arc magma system, the 1846/47 eruption of Volcan Quizapu exhibits a simple mixing relationship between andesite recharge and residing dacite magma. Comparing and contrasting this eruption with the homogeneous dacite from the 1932 eruption provides a catalog of the magma mixing signatures that develop on the whole rock and crystal scales during a single mixing event. Moreover, the temperature evolution in the shallow dacite magma system is investigated using multiple geo-thermometers. It is shown that heat transfer of sensible and latent heat due to crystallization in the hot recharge magma during the magma mixing results in a late-stage reheating of the dacite magmas and their eruptions as effusive lava rather explosive pumice.;The final chapter of this work explores the time scales magma storage in the shallow crust at Volcan Quizapu using the 226Ra- 230Th age dating as well as the time scale that is associated with the recharge, mixing, and eruption in 1846/47 using Magnesium diffusion in plagioclase. A four-component mixture model is developed to decipher 226Ra-230Th age information from bulk mineral separates. It is shown that single mixing events alter the long-term record for crystal storage and that the time scales of recharge, mixing, and eruption are on the order days to weeks for the 1846/47 eruption of Volcan Quizapu.