Quickening the pulse: Fractal tempos in continental arc magmatism

The magmatic history of a continental arc can be characterized as punctuated equilibrium, whereby long periods of low-level activity are interrupted periodically by short bursts of high-volume magmatism ("flare-ups"). Geochronological records, most notably from zircon, reveal episodicity in volcanism, pluton formation, and detrital sedimentation in, and associated with, arc segments and volcano-plutonic suites. Distinct tempos can be recognized at all resolvable spatial and temporal scales and are broadly fractal, with each scale reflecting the timescale of p rocesses occurring at different levels in the arc crust. The tempos of continental arc magmatism thus reflect modulation of the mantle-power input as it is progressively filtered through the continental crust.