The causes of continental arc flare ups and drivers of episodic magmatic activity in Cordilleran orogenic systems

Continental arcs in Cordilleran orogenic systems display episodic changes magma production rate, alternating between flare ups (70–90 km3 km−1 Myr−1) and lulls (< 20 on timescales of tens millions years. Arc segments or individual magmatic suites may have even higher rates, up several 100 s Myr−1, during ups. These rates are largely determined by estimating volumes arc crust, but do not reflect melt from the mantle. The bulk mantle-derived magmas recycled back into mantle delamination roots after differentiation deep crust. Mantle-derived for continental estimated to be 140–215 Myr−1 ≤ 15 lulls. Melt averaged over multiple cycles consistent with independent estimates partial melting wedge subduction zones, however, both anomalously high low, respectively. difference is larger than predicted petrologic numerical models that explore range globally observed parameters (e.g., convergence height wedge). This suggests other processes required increase magmatism suppress There many viable explanations, one possibility crystallized melts asthenospheric temporarily stored lithosphere then remobilized Basaltic stall inactive parts system, like back-arc, refertilizing suppressing delivery lower Subsequent landward migration (i.e., toward interior continent) encounter such refertilized source regions, contributing activity a up. A review commonly coincide this start years before occurs. region activity, width, can also expand significantly expansion different regions across lithospheric crustal boundaries cause temporal shifts radiogenic isotopic composition magmatism. In absence migration, more muted. Isotopic studies xenoliths exposures crust suggest primary, generated substantial contributions subcontinental lithosphere. caused variety mechanisms, including slab anchoring folding transition zone could generate dip. Episodic shallowing associated tectonic systems, alternations shortening extension upper plate. Studies help link irregular geodynamic cyclicity.