Understanding magma transport in sheet intrusions is crucial to interpreting volcanic unrest. Studies of dyke emplacement and geometry focus predominantly on low-viscosity, mafic dykes. Here, we present an in-depth study two high-viscosity dykes (106 Pa·s) the Chachahuén volcano, Argentina, Great Dyke Sosa Dyke. To quantify geometries, flow indicators, viscosity, combine photogrammetry, microst...