Constraining the conditions and timescales of magma storage, mixing, and transfer—and understanding how deep-seated unrest progresses towards eruption—is key to deciphering early stages of magma system reactivation. While these processes are increasingly well-resolved in Iceland’s on-rift zones, magma dynamics in off-rift flank zones remain poorly understood, despite their potential for hazardous explosive eruptions after long...

The valence state of Fe plays a vital role in setting and recording the oxidation state of magmas, commonly expressed in terms of oxygen fugacity ( $$f_{\textrm{O}_{2}}$$ f O 2 ). However, our knowledge of how and why $$f_{\textrm{O}_{2}}$$ f O 2 varies within and between magmatic systems remains patchy because of diverse challenges associated with estimating the valence state of Fe in glasses and minerals routinely. Here we i...

Clinopyroxene is a major rock forming mineral capable of incorporating diverse metal cations. As a consequence, clinopyroxene preserves valuable archives of magmatic processes. Understanding clinopyroxene is thus essential for understanding Earth’s wider chemical evolution. However, knowledge about the relative abundances of ferrous and ferric iron in magmatic clinopyroxene remains sparse because it is not currently possible t...

Silicic volcanoes are increasingly understood to be underlain by crystal-rich and vertically extensive magma reservoirs within which disequilibrium is widespread. Observations from ignimbrite deposits demonstrate that silicic magma reservoirs are often compartmentalised and compositionally stratified. However, it is currently unclear whether the small (i.e., < 0.1 km 3 dense rock equivalent) eruptions that dominate activity at...