Deciphering the evolution of the magma plumbing system in a dilated continental fault: A case study from the Datong volcanic field, North China Craton

The spatiotemporal evolution of magma plumbing systems in continental rift settings is fundamental to understanding volcanic activity and assessing associated hazards. However, the processes governing this evolution, particularly the transition from simple to complex architectures, remain poorly constrained. This study investigated the Datong volcanic field, North China Craton, as a natural laboratory to unravel the evolutionary pathway of a magma plumbing system controlled by active faulting. We present a comprehensive analysis of three successive eruptive episodes—a pyroclastic density current, Lava 1, and Lava 2—distributed along the Sanggan River fault in northern China. Our integrated approach combines field relationships, petrography, whole-rock and mineral geochemistry, thermodynamic modeling, mantle source inversion, and geothermobarometry. The results reveal that the first two eruptive episodes were fed by a transient, shallow (<3 kbar) dike cluster, suggesting rapid magma ascent with limited crustal residence. In contrast, the third episode sourced magma from a more mature and complex two-tiered reservoir system, comprising a deep magma chamber at ∼8 kbar and a shallow crystal mush zone at ∼2 kbar. Critically, we demonstrate that the development of plumbing systems is not strictly linear. Instead, we propose a model of plumbing system duality in extensional settings, where mature, stable reservoirs can coexist with transient, structurally controlled magma conduits. This suggests that fault-induced stress concentration may facilitate the propagation of new dikes that bypass established reservoirs. This finding highlights the unpredictability of eruption pathways, offering significant implications for volcanic hazard assessment in continental rifts globally.