Episodic continental arc magmatism: investigating links between compositional variation and flare-ups in the Peruvian arc

Cordilleran continental arcs are known to exhibit episodic magmatism characterized by sequences of flare-ups and lulls. The controls on this episodic behavior have not been adequately resolved at this time, but model types can be broadly classified as either cyclic feedback processes operating internal to the arc system related to the upper plate, or external forcing processes acting on the arc related to the lower plate, such as an increase in mantle power or plate dynamics. This study analyzes a geochronology and geochemistry dataset from the Peruvian segment of the American Cordillera to determine likely triggering mechanisms, with a focus on testing the arc-internal back-arc underthrusting upper plate model by DeCelles, Ducea [1]. A sequence of stacked time series plots is created for segments of the Peruvian Coastal Batholith and for the Eastern Cordillera to compare flare-ups and lulls. Analysis results show little direct support for upper plate feedback models at the arc segment scale. Irregular episodicity, mantle dominated geochemistry and pronounced along-strike variability is observed for the Peruvian arc, suggesting magmatism is driven by upper plate mantle processes acting as the primary modulator of the physical, thermal, and chemical evolution of the arc system. Chemical diversity along and across-arc can be explained by changing upper plate mantle input and basement terranes, varying assimilated material, changing crustal thickness, arc migration, and the extent of magma fractionation. The absence of a uniform arc magma chemistry across arc segments strongly supports a migration-driven framework. Arc migration into refertilized lithospheric reservoirs triggers widespread magma remobilization, producing voluminous, spatially heterogenous flare-ups that inherit the isotopic and compositional character of the local upper plate, directly explaining the segment scale variations observed across the Peruvian arc.