Hydrothermal alteration influences physical and chemical properties of volcanic rocks, fluid migration, and evolution of volcanic and magmatic-hydrothermal systems. The circulation of hot magmatic fluids dissolves primary minerals, reorganises soluble elements, and precipitates secondary alteration assemblages. Such alteration processes record important information for understanding ancient and modern systems, and change physical and mechanical rock properties in ways that influence magma and fluid migration pathways, eruption styles (e.g., phreatic eruptions), flank stability, and resources.
Despite its importance, alteration can often be treated simplistically due to paucity in quantitative understanding of its spatio-temporal distribution. Recent advances have enabled characterisation of alteration minerals and processes across space and time, integrating remote sensing and geophysical methods, mineralogical and geochemical constraints; mechanical property measurements; and data-driven models that couple fluid flow, reaction, and deformation. This session thus invites contributions from remote sensing, geochemistry, mineralogy, geophysics, rock physics, and modelling that advance our understanding of alteration in magmatic-hydrothermal systems, and the implications of this alteration for volcanic hazards. We encourage diverse contributions, especially those integrating multiple disciplines: ground, satellite, drone and airborne remote sensing (multi and hyperspectral, thermal, SAR, LiDAR), time-series monitoring, structural studies, fluid-rock interaction processes, mineralogical evolution, experimental simulations, geochemical modelling, geophysical mapping (ERT, MT and others), rock physics and mechanics, field to laboratory studies, scaling from sample to edifice, phreatic/phreatomagmatic explosions, fluid migration, flank instability and collapse, and computational modelling.
Through this session we aim to establish a shared framework linking alteration across disciplines and outcomes in different volcanic settings, and to promote the gradual standardisation of approaches and understanding of hydrothermal alterations, its impact on volcanic systems, and distribution across time and space. We also foster collaborations to improve our ability to identify and evaluate critical developments driven by hydrothermal processes that may lead to instability, flank failure or triggered explosions.