Petrological Constraints on the Thermal History of Magma Storage in the Crust

Understanding the links between magmatic evolution and volcanic eruptions requires knowledge of the physical behavior of magmas stored and transported within Earth's crust. The mobility of magmas is fundamentally tied to their rheology and therefore the temperatures they experience during residence—their thermal history. We review petrological and other constraints on magma thermal histories that silicic magmas experience during crustal storage. We also focus on the recent debate between cold and warm magma storage models, using a common conceptual framework that allows a more coherent synthesis of magma storage conditions. Evidence suggests that although most silicic crustal magmatic systems spend most of their time in a rheologically immobile state, variations exist in space and time. The recognition of dominantly immobile but variable storage conditions allows us to move beyond a simple dichotomy and to ask more interesting questions about how these variations in magma storage occur and evolve. ▪ Understanding the thermal conditions of crustal magma storage is critical to assessing magma mobility and the ability to erupt. ▪ We synthesize available information about thermal histories that magmas experience within a common conceptual framework. ▪ Most silicic magmas spend most of their time in a rheologically immobile state, but variability exists over time and space within and between magma systems. ▪ We can advance our understanding most effectively by focusing on the controls on these variations and implications for magma evolution and eruption.