Magma titanium and iron contents dictate crystallization timescales and rheological behaviour in basaltic volcanic systems

Magma ascending through Earth's crust undergoes complex chemical and physical changes that may induce crystallization, a process that contributes to lead the magmatic system toward a thermodynamic state of equilibrium. The diverse cooling and deformative regimes suffered by magmas heavily influence crystallization rates, solidification timescales, and consequently, the rheological evolution of magma. This, in turn, significantly impacts the dynamics of volcanic plumbing systems and the associated eruptive styles. Here, we investigate the rheological changes in Stromboli magma (Italy) during disequilibrium crystallization under non-isothermal subliquidus conditions. By systematically varying the cooling rate (1-10 degrees C/min) and the shear rate (1-10 s-1), we find that cooling rates significantly influence the solidification path of the basalt, whereas shear rates have a subordinate effect. By comparing our results with literature data on basalts from Mt. Etna (Italy), characterized by higher TiO2 and FeOtot contents, we observed distinct timescales and rates of solidification, contributing to unique eruptive dynamics in these volcanic plumbing systems.A critical compositional factor influences the rheological evolution and crystallization timescales of basalts under disequilibrium conditions, according to cooling rate deformation experiments carried out on Stromboli melt.